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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2018	Mar. 04, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Trading Symbol	CBIO
Entity Registrant Name	CATALYST BIOSCIENCES, INC.
Entity Central Index Key	0001124105
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		11,970,042
Entity Public Float			$ 137,450,357

Consolidated Balance Sheets - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 31,213,000	$ 14,472,000
Short-term investments	88,914,000	17,971,000
Restricted cash	50,000	5,333,000
Prepaid and other current assets	3,814,000	1,333,000
Total current assets	123,991,000	39,109,000
Other assets, noncurrent	543,000	128,000
Property and equipment, net	386,000	276,000
Total assets	124,920,000	39,513,000
Current liabilities:
Accounts payable	1,248,000	747,000
Accrued compensation	1,495,000	1,366,000
Other accrued liabilities	2,043,000	1,322,000
Deferred revenue, current portion		212,000
Deferred rent, current portion	15,000	7,000
Redeemable convertible notes	0	5,085,000
Total current liabilities	4,801,000	8,739,000
Deferred rent, noncurrent portion	174,000
Total liabilities	4,975,000	8,739,000
Stockholders’ equity:
Preferred stock, $0.001 par value, 5,000,000 shares authorized; 0 and 3,680 shares issued and outstanding at December 31, 2018 and 2017, respectively
Common stock, $0.001 par value, 100,000,000 shares authorized; 11,954,528 and 6,081,230 shares issued and outstanding at December 31, 2018 and 2017, respectively	12,000	6,000
Additional paid-in capital	323,279,000	204,262,000
Accumulated other comprehensive loss	(4,000)
Accumulated deficit	(203,342,000)	(173,494,000)
Total stockholders’ equity	119,945,000	30,774,000
Total liabilities and stockholders’ equity	$ 124,920,000	$ 39,513,000

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	3,680
Preferred stock, shares outstanding	0	3,680
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	11,954,528	6,081,230
Common stock, shares outstanding	11,954,528	6,081,230

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Contract revenue	$ 6	$ 1,018
Type of Revenue [Extensible List]	cbio:ContractMember	cbio:ContractMember
Operating expenses:
Research and development	$ 21,474	$ 12,847
General and administrative	12,354	9,993
Total operating expenses	33,828	22,840
Loss from operations	(33,822)	(21,822)
Interest and other income, net	3,767	261
Net loss	(30,055)	(21,561)
Deemed dividend for convertible preferred stock beneficial conversion feature		(3,951)
Net loss attributable to common stockholders	$ (30,055)	$ (25,512)
Net loss per share attributable to common stockholders, basic and diluted	$ (2.68)	$ (7.45)
Shares used to compute net loss per share attributable to common stockholders, basic and diluted	11,213,884	3,423,901

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (30,055)	$ (21,561)
Other comprehensive income (loss):
Unrealized (loss) gain on available-for-sale securities	(4)	1
Total comprehensive loss	$ (30,059)	$ (21,560)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balance at Dec. 31, 2016	$ 16,071		$ 1	$ 164,053	$ (1)	$ (147,982)
Balance (in shares) at Dec. 31, 2016			801,756
Stock-based compensation expense	863			863
Issuance of common stock, net of issuance costs	5,336			5,336
Issuance of common stock, net of issuance costs, shares			439,880
Issuance of convertible preferred stock, common stock and warrants for follow-on offering, net of issuance costs	18,563		$ 2	18,561
Issuance of convertible preferred stock, common stock and warrants for follow-on offering, net of issuance costs, shares		13,350	1,470,000
Issuance of common stock for follow-on offering, net of issuance costs	9,684		$ 1	9,683
Issuance of common stock for follow-on offering, net of issuance costs, shares			1,105,263
Issuance of common stock upon exercise of warrants	1,817			1,817
Issuance of common stock upon exercise of warrants, shares			330,331
Conversion of preferred stock to common stock			$ 2	(2)
Conversion of preferred stock to common stock, shares		(9,670)	1,934,000
Deemed dividend for preferred stock beneficial conversion feature				3,951		(3,951)
Deemed dividend for preferred stock beneficial conversion feature, shares			0
Unrealized gain (loss) on available-for-sale securities	1				1
Net loss	(21,561)					(21,561)
Balance at Dec. 31, 2017	30,774		$ 6	204,262		(173,494)
Balance (in shares) at Dec. 31, 2017		3,680	6,081,230
Opening balance adjustment - adoption of ASC 606 at Dec. 31, 2017	207					207
Balance at Dec. 31, 2017	30,981		$ 6	204,262		(173,287)
Stock-based compensation expense	2,606			2,606
Issuance of common stock for follow-on offering, net of issuance costs	106,762		$ 4	106,758
Issuance of common stock for follow-on offering, net of issuance costs, shares			3,382,352
Issuance of common stock upon exercise of warrants	9,545		$ 2	9,543
Issuance of common stock upon exercise of warrants, shares			1,735,419
Conversion of preferred stock to common stock, shares		(3,680)	736,000
Issuance of common stock from stock grants and exercise of stock options	107			107
Issuance of common stock from stock grants and exercise of stock options, shares			19,506
Conversion of redeemable convertible notes to common stock, value	3			3
Conversion of redeemable convertible notes to common stock, shares			21
Unrealized gain (loss) on available-for-sale securities	(4)				(4)
Net loss	(30,055)					(30,055)
Balance at Dec. 31, 2018	$ 119,945		$ 12	$ 323,279	$ (4)	$ (203,342)
Balance (in shares) at Dec. 31, 2018			11,954,528

Consolidated Statements of Stockholders' Equity (Parenthetical)	12 Months Ended
	Dec. 31, 2018 shares
Statement Of Stockholders Equity [Abstract]
Stock grants in lieu of cash compoensation	6,790

Consolidated Statements of Cash Flows - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2018

Dec. 31, 2017

Operating Activities

Net loss

$ (30,055)

$ (21,561)

Adjustments to reconcile net loss to net cash used in operating activities:

Stock-based compensation expense

2,606

863

Depreciation and amortization

149

173

Loss on disposal of property and equipment

116

Changes in operating assets and liabilities:

Prepaid and other current assets

(2,895)

(351)

Accounts receivable

Deposits

(128)

Accounts payable

500

(90)

Accrued compensation and other accrued liabilities

850

1,287

Deferred revenue

(6)

(118)

Deferred rent

182

(40)

Net cash flows used in operating activities

(28,553)

(19,940)

Investing Activities

Proceeds from maturities of short-term investments

127,967

14,300

Purchase of short-term investments

(198,912)

(25,472)

Purchases of property and equipment

(376)

(23)

Net cash flows used in investing activities

(71,321)

(11,195)

Financing Activities

Payments for the redemption of redeemable convertible notes

(5,082)

(14,318)

Proceeds from issuance of common stock, net of issuance costs

5,336

Proceeds from issuance of preferred stock, common stock and warrants for follow-on offering, net of issuance costs

18,563

Proceeds from exercise of stock options and issuance of stock grants

107

Proceeds from exercise of warrants

9,545

1,817

Net cash flows provided by financing activities

111,332

21,082

Net increase (decrease) in cash and cash equivalents

11,458

(10,053)

Cash, cash equivalents and restricted cash at beginning of the period

19,805

^[1]

29,858

Cash, cash equivalents and restricted cash at end of the period

^[1]

31,263

19,805

Supplemental Disclosure of Non-Cash Investing and Financing Activities:

Deemed dividend for convertible preferred stock beneficial conversion feature

3,951

Adoption of ASC 606

207

Conversion of redeemable convertible notes to common stock

Unrealized loss/gain on investments

Follow-on Offering

Financing Activities

Proceeds from issuance of common stock, net of issuance costs

$ 106,762

$ 9,684

[1]	The following table provides a reconciliation of cash and restricted cash to amounts reported within the condensed consolidated balance sheets:

Consolidated Statements of Cash Flows (Parenthetical) - USD ($)
$ in Thousands

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Statement Of Cash Flows [Abstract]

Cash and cash equivalents

$ 31,213

$ 14,472

Restricted cash

5,333

Total cash and restricted cash

$ 31,263

^[1]

$ 19,805

^[1]

$ 29,858

[1]	The following table provides a reconciliation of cash and restricted cash to amounts reported within the condensed consolidated balance sheets:

Nature of Operations

12 Months Ended

Dec. 31, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Nature of Operations

1.	Nature of Operations

Catalyst Biosciences, Inc. and its subsidiary (the “Company” or “Catalyst”) is a clinical-stage biotechnology company focused on developing novel medicines to address hematology indications, including the treatment of hemophilia. Its facilities are in South San Francisco, California and it operates in one segment. Prior to August 20, 2015, the name of the Company was Targacept, Inc. (“Targacept”). On August 20, 2015, Targacept completed its business combination with Catalyst (the “Merger”).

Liquidity

12 Months Ended

Dec. 31, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Liquidity

The Company had a net loss of $30.1 million for the year ended December 31, 2018 and an accumulated deficit of $203.3 million as of December 31, 2018 and expects to continue to incur losses for the next several years. As of December 31, 2018, the Company had $120.1 million in cash, cash equivalents and short-term investments and used $28.6 million of cash in operating activities for the year ended December 31, 2018. Management believes that the currently available resources, including cash, cash equivalents and short-term investments, will provide sufficient funds to enable the Company to meet its operating plan for at least the next twelve months from the date of this filing.

The Company plans to continue to fund losses from operations and capital funding needs through future equity and/or debt financings, as well as potential additional asset sales, licensing transactions, collaborations or strategic partnerships with other companies. The sale of additional equity or convertible debt could result in additional dilution to its stockholders. The incurrence of indebtedness would result in debt service obligations and could result in operating and financing covenants that would restrict the Company’s operations. The Company can provide no assurance that financing will be available in the amounts it needs or on terms acceptable to it, if at all. If the Company is not able to secure adequate additional funding it may be forced to delay, make reductions in spending, extend payment terms with suppliers, liquidate assets where possible, and/or suspend or curtail planned programs. Any of these actions could materially harm its business.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

3.	Summary of Significant Accounting Policies

Basis of Presentation

The accompanying consolidated financial statements include the accounts of the Company and its subsidiary. Intercompany accounts and transactions have been eliminated in consolidation. The Company’s consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles (“GAAP”).

Use of Estimates

The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to revenue recognition, convertible notes and related warrants up to the date of conversion, common stock and stock-based compensation. The Company bases its estimates on various assumptions that the Company believes to be reasonable under the circumstances. Actual results could differ from those estimates.

Accounting Pronouncements Recently Adopted

In November 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-18, Restricted Cash, which requires amounts generally described as restricted cash and restricted cash equivalents be included with cash and cash equivalents when reconciling the total beginning and ending amounts for the periods shown on the statement of cash flows. We adopted ASU 2016-18 effective January 1, 2018, using a retrospective transition method to each period presented. The adoption of this ASU changed previously reported amounts in the condensed consolidated statement of cash flows for the year ended December 31, 2017, by increasing our cash flows from financing activities by $5.3 million as compared to previously reported amounts for the prior year period.

In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments. The standard provides guidance on how certain cash receipts and payments are presented and classified in the statement of cash flows. The standard is intended to reduce current diversity in practice. The Company adopted ASU 2016-15 effective January 1, 2018, and this guidance did not have an impact on the Company’s financial statements.

In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments – Overall (Topic 825-10), which updates certain aspects of recognition, measurement, presentation and disclosure of financial instruments. Subsequently, in February 2018, the FASB issued ASU No. 2018-03, Technical Corrections and Improvements to Financial Instruments - Overall (Topic 825-10), which clarifies certain aspects of ASU 2016-01, which includes provisions to accounting for equity investments, financial liabilities under the fair value option and presentation and disclosure requirements for financial instruments. The amended guidance requires equity securities, except for those accounted for under the equity method of accounting, with determinable fair values to be measured at fair value with changes in fair value recognized in net income (loss). The Company adopted ASU 2016-01 and 2018-03 effective January 1, 2018, and this guidance did not have a material impact on the Company’s financial statements, as the Company only has debt securities.

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), which amends the existing accounting standards for revenue recognition. ASU 2014-09 is based on principles that govern the recognition of revenue at an amount an entity expects to be entitled when products are transferred to customers. Subsequently, the FASB has issued the following standards related to ASU 2014-09: ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations; ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing; and ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients, (collectively, the “new revenue standards”). The Company adopted the new revenue standards effective January 1, 2018, using the modified retrospective method through a cumulative adjustment to equity. The Company has identified that the most significant change relates to its accounting for collaboration arrangements with multiple deliverables, in particular, the ISU Abxis agreement. Under the old guidance, such deliverables and consideration must be accounted for under a single unit of accounting along with other arrangement deliverables and consideration that does not have stand-alone value and are recognized as revenue over the estimated period that the performance obligations are to be performed. Under the current new standard however, the total arrangement consideration is allocated to each performance obligation based on its estimated stand-alone selling price and revenue is recognized as each performance obligation is satisfied. As a result, revenue for this transaction is recorded in an earlier period than under the old guidance, resulting in a $0.2 million increase to the Company’s opening balance of accumulated deficit as of January 1, 2018.

Adopting ASU No. 2014-09, Revenue from Contracts with Customers, or the new revenue standard, involved new estimates and judgments related to the estimates of stand-alone selling prices and the allocation of discounts and variable consideration in allocating the transaction price. The Company recognized revenue earlier under the current new standard and may have more variability due to significant estimates involved under the new accounting guidance.

In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (“ASU 2016-02”), which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. Originally, entities were required to adopt ASU 2016-02 using a modified retrospective approach at the beginning of the earliest comparative period presented in the financial statements and the recognition of a cumulative-effect adjustment to the opening balance of retained earnings. The FASB subsequently issued ASU No. 2018-10 and ASU No. 2018-11 in July 2018, which provide clarifications and improvements to ASU 2016-02 (collectively, the “new lease standard”).

ASU No. 2018-11 a also provides the optional transition method which allows companies to apply the new lease standard at the adoption date instead of at the earliest comparative period presented and continue to apply the provisions of the previous lease standard in its annual disclosures for the comparative periods. The new lease standard requires lessees to present a right-of-use (“ROU”) asset and a corresponding lease liability on the balance sheet. Lessor accounting is substantially unchanged compared to the current accounting guidance. Additional footnote disclosures related to leases will also be required.

On January 1, 2019, the Company adopted the new lease standard using the optional transition method. The comparative financial information will not be restated and will continue to be reported under the previous lease standard in effect during those periods. In addition, the new lease standard provides a number of optional practical expedients in transition. The Company elected the package of practical expedients. As such, the Company will not reassess whether expired or existing contracts are or contain a lease; will not need to reassess the lease classifications or reassess the initial direct costs associated with expired or existing leases. The Company did not elect the use-of-hindsight or the practical expedient pertaining to land easements; the latter not being applicable to the Company.

The new lease standard also provides practical expedients for an entity’s ongoing accounting. The Company elected the short-term lease recognition exemption for all leases that qualify. This means, for those leases that qualify, the Company will not recognize ROU assets or lease liabilities, and this includes not recognizing ROU assets or lease liabilities for existing short-term leases of those assets in transition. The Company elected the practical expedient to not separate lease and non-lease components for certain classes of assets.

On January 1, 2019, the Company expects to recognize ROU assets of $2.5 million and lease liabilities of $2.3 million. The Company does not expect the adoption of the new lease standard to impact its consolidated statement of operations or its consolidated statement of cash flows.

Cash and Cash Equivalents

The Company invests its excess cash in bank deposits, consisting primarily of money market mutual funds. The Company considers all highly liquid investments with original maturities of three months or less from the date of purchase to be cash equivalents.

Restricted Cash

Restricted cash at December 31, 2018 consists of a certain certificate of deposit account that is pledged as collateral for the Company’s corporate credit card program. Restricted cash at December 31, 2017 consisted of certain checking, money market and certificate of deposit accounts that are: (i) pledged to or held in a segregated escrow account by the Company’s correspondent banks for the benefit of the holders of the redeemable convertible notes in order to facilitate the payment of the redeemable convertible notes upon redemption or at maturity as discussed in Note 4 – Fair Value Measurements or (ii) pledged as collateral for the Company’s corporate credit card and deposit for its facility lease.

Fair Value of Financial Instruments

The Company applies fair value accounting for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date.

The fair value hierarchy requires that an entity maximize the use of observable inputs when estimating fair value. The fair value hierarchy includes the following three-level classification which is based on the market observability of the inputs used for estimating the fair value of the assets or liabilities being measured:

Level 1 – Quoted prices in active markets for identical assets or liabilities.

Level 2 – Observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3 – Inputs that are generally unobservable and typically reflect management’s estimate of assumptions that market participants would use in pricing the asset or liability.

Property and Equipment

Property and equipment are stated at cost, less accumulated depreciation. Depreciation is computed using the straight-line method over the estimated useful lives of the respective assets, which are three years for computer equipment and software, and three to seven years for furniture and leasehold improvements.

Investments

All investments have been classified as “available-for-sale” and are carried at estimated fair value as determined based upon quoted market prices or pricing models for similar securities. Management determines the appropriate classification of its investments at the time of purchase and reevaluates such designation as of each balance sheet date. Unrealized gains and losses are excluded from earnings and are reported as a component of comprehensive loss. Realized gains and losses and declines in fair value determined to be other-than-temporary, if any, on available-for-sale securities are included in interest and other income. The cost of securities sold is based on the specific-identification method. Interest on short-term investments is included in interest and other income.

Derivative Liability

The embedded redemption feature in the redeemable convertible notes, which were convertible into shares of the Company’s common stock was bifurcated and was accounted for as a derivative liability at its estimated fair value. The derivative was subject to remeasurement at the end of each reporting period, with changes in fair value recognized as a component of interest and other income, in the consolidated statements of operations. These notes were repaid in 2018. The Company adjusted the liability for changes in fair value until the earlier of the conversion, redemption or maturity of the redeemable convertible notes. At December 31, 2017 the fair value was $0.

Revenue Recognition

Effective January 1, 2018, the Company adopted Accounting Standards Codification (“ASC”) 606 using the modified retrospective method through a cumulative adjustment to equity, which resulted in an immaterial $0.2 million decrease to our opening balance of accumulated deficit as of January 1, 2018. The Company enters into collaboration arrangements that may include the receipt of payments for up-front license fees, success-based milestone payments, full time equivalent based payments for research services, product supplies, and royalties on any future sales of commercialized products that result from the collaborations.

In determining the appropriate amount of revenue to be recognized as it fulfills its obligations under its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations based on estimated selling prices; and (v) recognition of revenue when the Company satisfies each performance obligation.

At the inception of each arrangement that includes variable consideration such as development milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price which is then allocated to each relevant performance obligation. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received.

As part of the accounting for these arrangements, the Company must develop assumptions that require judgment to determine the timing of recognition and the stand-alone selling price for each performance obligation identified in the contract. The Company uses key assumptions to determine the stand-alone selling price, which may include forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success.

Estimated selling prices for licenses are calculated using the residual approach if the Company has not yet established a price for such license and the license has not previously been sold on a standalone basis. Otherwise, selling prices for licenses are determined using an income approach model and include key assumptions such as: development timeline, revenue forecast, commercialization expenses, discount rate and probabilities of technical and regulatory success. To estimate selling prices for research services and product supply, the Company uses a cost-plus margin approach.

Research and Development Expenses

Research and development costs are expensed as incurred. Research and development costs consist of payroll and other personnel-related expenses, laboratory supplies and reagents, contract research and development services, and consulting costs, as well as allocations of facilities and other overhead costs. Under the Company’s collaboration agreements, certain specific expenditures are reimbursed by third parties. During the years ended December 31, 2018 and 2017, the Company recorded a reduction to research and development expenses of $0.05 million and $0.1 million, respectively related to these reimbursements.

Concentration of Credit Risk

Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash and cash equivalents, investments and restricted cash. The Company’s investment policy restricts cash investments to high credit quality, investment grade investments. The Company believes that it has established guidelines for investment of its excess cash that maintain safety and liquidity through its policies on diversification and investment maturity. The Company is exposed to credit risk in the event of default by the institutions holding the cash and cash equivalents to the extent of the amounts recorded on the balance sheets.

The Company’s accounts receivable, included in prepaid and other current assets, at December 31, 2018 was $0.01 million, due from ISU Abxis, see Note 12. The Company has incurred no credit losses to date. The Company does not require collateral from its collaboration partners.

Income Taxes

Income taxes are computed using the liability method. Deferred tax assets and liabilities are determined based on the differences between the financial reporting and tax basis of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse.

The Company follows the authoritative guidance on accounting for uncertainty in income taxes. This guidance prescribes a more-likely-than-not threshold for financial statement recognition and measurement of a tax position taken in the Company’s income tax returns. This interpretation also provides guidance on accounting for interest and penalties and associated with tax positions, accounting for income taxes in interim periods and income tax disclosures.

The Company’s policy is to include penalties and interest expense related to income taxes as a component of other expense and interest expense, respectively, as necessary.

Stock-Based Compensation

The Company measures the cost of employee and director services received in exchange for an award of equity instruments based on the fair value of the award on the date of grant and recognizes the related expense over the period during which the employee or director is required to provide service in exchange for the award on a straight-line basis.

The Company uses the Black-Scholes option-pricing valuation model to estimate the grant-date fair value of stock-based awards. The determination of fair value for stock-based awards on the date of grant using an option-pricing model requires management to make certain assumptions regarding a number of variables. Upon adoption of ASU 2016-09, the Company can make an accounting policy election to either estimate the number of share-based awards that are expected to vest, or account for forfeitures when they occur. The Company elected to account for forfeitures when they occur. As such, the Company recognizes stock-based compensation expense, over their requisite service period, based on the vesting provisions of the individual grants.

For nonemployee stock-based awards, the measurement date on which the fair value of the stock-based award is calculated is equal to the earlier of (i) the date at which a commitment for performance by the counterparty to earn the equity instrument is reached or (ii) the date at which the counterparty’s performance is complete. The Company recognizes stock-based compensation expense for the fair value-based measurement of the nonemployee awards using the Black Scholes option-pricing valuation model and the awards are typically subject to periodic re-measurement over the period that services are rendered.

Deferred Rent

The Company’s facilities lease agreement provides for an escalation of rent payments each year. The Company records rent expense on a straight-line basis over the term of the lease. The difference between the amount of expense recognized and the amount of rent paid is recorded as deferred rent in the accompanying consolidated balance sheets.

Net Loss per Share

Basic net loss per share is calculated by dividing the net loss by the weighted average number of shares of common stock outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive given the net loss of the Company for all periods presented.

Fair Value Measurements

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Fair Value Measurements

4.	Fair Value Measurements

For a description of the fair value hierarchy and our fair value methodology, see “Note 3 – Summary of Significant Accounting Policies”. As of December 31, 2018 and 2017, the Company’s highly liquid money market funds included within cash equivalents, restricted cash and U.S. Treasury securities are valued using Level 1 inputs. The Company classifies its federal agency securities as Level 2. There were no transfers in or out of Level 1 and Level 2 during the periods presented. US Treasury securities are bonds issued by the U.S. government and are fully backed by the U.S. government. Given the frequency at which U.S. Treasury securities trade and the accessibility of observable, quoted prices for such assets in active markets, they are recognized as Level 1 assets. Federal agency securities are bonds and notes issued by government-sponsored enterprises, including Fannie Mae, Freddie Mac and the Federal Home Loan Bank. Since federal agency securities typically do not trade as U.S. Treasury securities and no exchange exists to price such investments, they are recognized as Level 2 assets.

At December 31, 2017 the fair value of the derivative liability was $0. The estimated reporting date fair value-based measurement of the derivative liability was calculated using the Black-Scholes valuation model.

The following tables present the fair value hierarchy for assets and liabilities measured at fair value on a recurring basis as of December 31, 2018 and 2017 (in thousands):

	December 31, 2018
	Level 1		Level 2		Level 3		Total
Financial assets:
Money market funds⁽¹⁾	$	29,090	$	—	$	—	$	29,090
Federal agency securities⁽¹⁾		—		999		—		999
Restricted cash ⁽²⁾		50		—		—		50
U.S. Treasury securities⁽³⁾		74,139		—		—		74,139
Federal agency securities⁽³⁾		—		14,775		—		14,775
Total financial assets	$	103,279	$	15,774	$	—	$	119,053

(1)	Included in cash and cash equivalents on accompanying consolidated balance sheets.

(2)	$0.05 million of restricted cash serves as collateral for the Company’s corporate credit card.

(3)	Included in short-term investments on accompanying consolidated balance sheets and are classified as available-for-sale securities.

	December 31, 2017
	Level 1		Level 2		Level 3		Total
Financial assets:
Money market funds⁽¹⁾	$	14,334	$	—	$	—	$	14,334
U.S. Treasury securities⁽³⁾		16,471		—		—		16,471
Restricted cash⁽²⁾		5,333		—		—		5,333
Federal agency securities⁽³⁾		—		1,500		—		1,500
Total financial assets	$	36,138	$	1,500	$	—	$	37,638

(1)	Included in cash and cash equivalents on accompanying consolidated balance sheets.

(2)	$5.3 million of restricted cash in the Indenture (see Note 9) serves as full collateral for the redeemable convertible notes.

(3)	Included in short-term investments on accompanying consolidated balance sheets and are classified as available-for-sale securities.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Financial Instruments

12 Months Ended

Dec. 31, 2018

Investments All Other Investments [Abstract]

Financial Instruments

5.	Financial Instruments

Cash equivalents, restricted cash and short-term investments which are classified as available-for-sale securities, consisted of the following (in thousands):

-December 31, 2018	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Money market funds (cash equivalents)	$	29,090	$	—	$	—		$	29,090
Agency securities (cash equivalents)		999		—	$	—			999
Restricted cash		50		—		—			50
U.S. government agency securities		74,144		1		(6	)		74,139
Agency securities		14,774		1		—			14,775
Total financial assets	$	119,057	$	2	$	(6	)	$	119,053
Classified as:
Cash and cash equivalents								$	30,089
Short-term investments									88,914
Restricted cash									50
								$	119,053

December 31, 2017	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Money market funds	$	14,334	$	—	$	—		$	14,334
U.S. government agency securities		16,473		—		(2	)		16,471
Restricted cash		5,330		3		—			5,333
Agency securities		1,500		—		—			1,500
Total financial assets	$	37,637	$	3	$	(2	)	$	37,638
Classified as:
Cash and cash equivalents								$	14,334
Short-term investments									17,971
Restricted cash									5,333
								$	37,638

As of December 31, 2018, the remaining contractual maturities of available-for-sale securities was less than one year. There have been no material realized gains or losses on available-for-sale securities for the periods presented. The carrying amounts of cash, other assets, other receivables, accounts payable and other payables approximate their fair values due to the short-term maturity of these instruments.

Property and Equipment

12 Months Ended

Dec. 31, 2018

Property Plant And Equipment [Abstract]

Property and Equipment

6.	Property and Equipment

Property and equipment consisted of the following (in thousands):

	Year Ended December 31,
	2018			2017
Furniture	$	226		$	317
Leasehold improvements		84			1,598
Computer equipment		222			237
Software		139			147
		671			2,299
Less accumulated depreciation and amortization		(285	)		(2,023	)
Property and equipment, net	$	386		$	276

Property and equipment depreciation and amortization expense for the years ended December 31, 2018 and 2017 was $0.1 million and $0.2 million, respectively.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2018

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

7.	Commitments and Contingencies

Operating Leases

In November 2017, the Company entered into a new office lease agreement to lease approximately 8,606 rentable square feet of space located in South San Francisco, California. The term of the lease is five years and two months, starting February 16, 2018. On August 10, 2018, the Company entered into an amendment to the existing office lease agreement to lease an additional approximately 4,626 rentable square feet. The lease amendment will be coterminous with the original lease term above.

The Company’s rental expense under its operating leases was $0.4 million and $0.8 million for the years ended December 31, 2018 and 2017.

Future minimum lease payments under all non-cancelable operating leases at December 31, 2018, were as follows (in thousands):

2019	$	571
2020		587
2021		605
2022		617
2023		209
Total future minimum lease payments	$	2,589

Manufacturing Agreements

On May 20, 2016, the Company signed a development and manufacturing services agreement (the “Agreement”) with AGC Biologics, Inc. (“AGC”), formerly known as CMC ICOS Biologics, Inc., pursuant to which AGC will conduct manufacturing development. Together with AGC, the Company has successfully manufactured MarzAA for the Phase 2 portion of a planned Phase 2/3 clinical trial. The Company has agreed to a total of $3.8 million in payments to AGC pursuant to the initial statement of work under the Agreement, subject to completion of applicable work stages. As of December 31, 2018, the Company’s remaining obligations to AGC were $0.3 million under the Agreement.

On February 21, 2018, the Company and AGC entered into a new statement of work under the Agreement dated May 20, 2016, between the Company and AGC. Under the new statement of work, the Company has engaged AGC for the process transfer and commercial scale cGMP manufacturing of DalcA. The Company has agreed to a total of approximately $5.6 million in payments pursuant to the new statement of work, including the commercial scale manufacturing of DalcA, subject to completion of applicable work stages. As of December 31, 2018, the Company’s remaining obligations to AGC were $3.4 million under the new statement of work.

License Agreement Obligations

Under its technology license agreements to acquire certain technology rights, the Company has an obligation to pay minimum fees and then royalties based upon a percentage of any net sales of licensed products. License fees payable under the technology license agreements are $0.1 million in 2013 and each year thereafter until royalties commence. The technology license agreements also provide for future payments to be made by the Company upon the achievement of development milestones or cumulative sales milestones. Pursuant to the license and collaboration agreement with ISU Abxis (see Note 12 - Collaborations), the Company may be obligated to pay ISU Abxis up to $2.0 million in potential milestone payments. At December 31, 2018, no such milestones have been achieved.

In December 2018, the Company entered into an amended and restated license agreement with ISU Abxis (the “A&R ISU Abxis Agreement”), which amended and restated in full its previous license and collaboration agreement with ISU Abxis entered into in September 2013 (as subsequently amended in October 2014 and December 2016). The A&R ISU Abxis Agreement eliminates the profit-sharing arrangement in the Original ISU Abxis Agreement and provides for a low single-digit royalty payment to ISU Abxis, on a country-by-country basis, for net product sales of DalcA by the Company or its affiliates in each country other than South Korea. Pursuant to the A&R ISU Abxis Agreement, the Company will make up to an aggregate of $19.5 million in milestone payments to ISU Abxis, inclusive of $2.5 million in regulatory and development milestone payments and up to $17 million in commercial milestone payments, if the applicable milestones are met.

Pursuant to the termination agreement entered on December 8, 2016, the Company may be obligated to make milestone and royalty payments to Pfizer up to $17.5 million payable upon the achievement of clinical, regulatory and commercial milestones. Following commercialization of any product, Pfizer would also receive a single-digit royalty on net product sales on a country-by-country basis for a predefined royalty term. In February 2018, the Company paid Pfizer a $1 million milestone payment based on the dosing of the first patient in the ongoing Phase 2 study. With the termination agreement, the Company recovered worldwide exclusive license for research, development, manufacturing and commercialization to all company’s original FVIIa programs, including CB 813d.

Related Parties

12 Months Ended

Dec. 31, 2018

Related Parties

8.	Related Parties

On October 24, 2017 the Company announced a strategic research collaboration with Mosaic Biosciences, Inc. (“Mosaic”) to develop intravitreal anti-complement factor 3 (C3) products for the treatment of dry AMD and other retinal diseases. On December 21, 2018, the Company amended its collaboration agreement with Mosaic to, among other things, include certain additional products. According to the Mosaic collaboration agreement, as amended, the Company and Mosaic will co-fund the research. Dr. Usman, our Chief Executive Officer and a member of our board of directors, and Mr. Lawlor, a member of our board of directors, are also members of the board of directors of Mosaic. Expenses related to the collaboration were $1.3 million and $0.03 million for the years ended December 31, 2018 and 2017.

Redeemable Convertible Notes

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Redeemable Convertible Notes

9.	Redeemable Convertible Notes

The Company has no outstanding Notes remaining as of December 31, 2018.

On August 19, 2015, immediately prior to the Merger, the Company issued to Targacept stockholders non-interest bearing redeemable convertible notes (the “Notes”) in the aggregate principal amount of $37.0 million, which matured on February 19, 2018. The Notes did not bear interest. The principal amount of the Notes was convertible, at the option of each noteholder, into cash or into shares of the Company’s common stock at a conversion rate of $137.85 per share. On February 19, 2018, the Notes matured, and the remaining Notes were repaid in full with cash from the restricted cash indenture and an immaterial amount were converted to common stock.

In connection with the issuance of the Notes, on August 19, 2015, Targacept entered into an indenture (the “Indenture”) with American Stock Transfer & Trust Company, LLC, as trustee, and an escrow agreement with American Stock Transfer & Trust Company, LLC and Delaware Trust Company, LLC, as escrow agent, under which $37.0 million, which represented the initial principal amount of the Notes, was deposited in a segregated escrow account for the benefit of the holders of the Notes in order to facilitate the payment of the notes upon redemption or at maturity (the amount of such deposit together with interest accrued and capitalized thereon, the “Escrow Funds”). The Notes were the Company’s secured obligation, and the Indenture did not limit its other indebtedness, secured or unsecured.

The conversion to common stock feature of the Notes was determined to be a derivative liability requiring bifurcation and separate accounting. The Company elected to accrete the entire debt discount as interest expense immediately after the Merger. In addition, changes in the fair value of the derivative liability were being recorded within interest and other income in the consolidated statements of operations. The Company remeasured the derivative liability to fair value until the earlier of the conversion, redemption or maturity of the redeemable convertible notes.

As of December 31, 2018, there was no derivative liability and as of December 31, 2017, the fair value of the derivative liability was immaterial. The estimated reporting date fair value-based measurement of the derivative liability was calculated using the Black-Scholes valuation model.

The Company recognized no interest expense for both years ended December 31, 2018 and 2017, related to the amortization of the debt discount as the redeemable convertible notes were immediately fully redeemable at the option of the holders and the entire debt discount was expensed immediately after the Merger.

Stock Based Compensation

12 Months Ended

Dec. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Based Compensation

10.	Stock Based Compensation

2018 Omnibus Incentive Plan

In June 2018, stockholders of the Company approved the Company’s 2018 Omnibus Incentive Plan (the “2018 Plan”). The 2018 Plan had previously been approved by the Company’s Board of Directors (the “Board”) and the Compensation Committee of the Board, subject to stockholder approval. The 2018 Plan became effective on June 13, 2018 and provided an additional 1,500,000 stock options, following receipt of the requisite stockholder approval. The 2018 Plan replaces the Company’s 2015 Stock Incentive Plan, as amended (the “2015 Plan”). All awards outstanding under the 2015 Plan will remain in effect in accordance with their respective terms.

The following table summarizes stock option activity under the Company’s equity incentive plans and related information:

	Number of Shares Underlying Outstanding Options			Weighted- Average Exercise Price		Weighted-Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value (thousands)
Outstanding — December 31, 2016		140,990		$	128.25		3.93		—
Options granted		742,000		$	4.56
Options forfeited		(61,249	)	$	165.63
Outstanding — December 31, 2017		821,741		$	13.69		9.17	$	6,376
Options granted		612,050		$	13.13
Options exercised		(12,716	)	$	4.17			$	213
Options canceled/forfeited		(43,315	)	$	7.76
Options expired		(15,783	)	$	158.81
Outstanding — December 31, 2018		1,361,977		$	12.04		8.71	$	2,294
Exercisable — December 31, 2018		414,584		$	17.98
Vested and expected to vest — December 31, 2018		1,361,977		$	12.04
Shares available to be granted — December 31, 2018		1,295,144

Valuation Assumptions

The Company estimated the fair value of stock options granted using the Black-Scholes option-pricing formula and a single option award approach. Due to its limited history as a public company and limited number of sales of its common stock, the Company estimated its volatility considering a number of factors including the use of the volatility of comparable public companies. The expected term of options granted under the Plan, all of which qualify as “plain vanilla” per SEC Staff Accounting Bulletin 107, is determined based on the simplified method due to the Company’s limited operating history and is 6.04 years based on the average between the vesting period and the contractual life of the option. The risk-free rate is based on the yield of a U.S. Treasury security with a term consistent with the option. This fair value is being amortized ratably over the requisite service periods of the awards, which is generally the vesting period. The weighted average grant date fair value of employee stock options was $9.97 and $4.01 for the years ended December 31, 2018 and 2017, respectively, and was estimated using the following weighted-average assumptions for the years ended December 31, 2018 and 2017:

	Year Ended December 31,
	2018			2017
Employee Stock Options:
Expected term (in years)		6.04			6.03
Risk-free interest rate		2.67	%		2.03	%
Dividend yield		—			—
Volatility		92.61	%		110.29	%

Options Granted to Nonemployees

During the year ended December 31, 2018, no options were issued to consultants. During the year ended December 31, 2017, options to purchase 20,000 shares of common stock were issued to consultants that vest over one to four years with a weighted-average exercise price of $4.69 per share. During the years ended December 31, 2018, and 2017, the Company recorded stock-based compensation expense attributable to these nonemployee stock awards of $0.09 million and $0.02 million, respectively.

The estimated grant-date fair value of the nonemployee stock options was determined using the Black-Scholes valuation model and the following assumptions:

	Year Ended December 31,
	2018	2017
Non-Employee Stock Options:
Contractual Life (in years)	N/A		9
Risk-free interest rate	N/A		2.35	%
Dividend yield	N/A		—
Volatility	N/A		111.55	%

Total stock-based compensation recognized was as follows (in thousands):

	Year Ended December 31,
	2018		2017
Research and development	$	590	$	164
General and administrative⁽¹⁾		1,990		699
Total stock-based compensation	$	2,580	$	863

(1)

2018 includes $0.1 million in modification stock-based compensation expense related to a Board member’s separation agreement.

As of December 31, 2018, the Company had unrecognized employee stock-based compensation expense of $6.5 million, related to unvested stock option awards, which is expected to be recognized over an estimated weighted-average period of 2.78 years.

2018 Employee Stock Purchase Plan

In June 2018, the Company’s stockholders approved the 2018 Employee Stock Purchase Plan (the “ESPP”). The 2018 ESPP had previously been approved by the Board and the Compensation Committee of the Board, subject to stockholder approval which became effective as of June 13, 2018. Under the ESPP, employees meeting certain specific employment qualifications are eligible to participate and can purchase shares of common stock semi-annually on February 9^th and August 9^th of each year, through payroll deductions. The purchase price is 85% of the lower of the fair market value of the stock at the commencement or end of the offering period. The ESPP permits eligible employees to purchase shares of common stock through payroll deductions for up to 15% of qualified compensation.

A total of 120,000 shares of common stock may be granted in accordance with the terms of the ESPP. As of December 31, 2018, no shares of common stock have been issued to employees participating in the ESPP and 120,000 shares are available for issuance under the ESPP. Compensation expense, using Black-Scholes, for the ESPP was $0.03 million as of December 31, 2018.

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Income Taxes

11.	Income Taxes

The Company has incurred cumulative net operating losses since inception and, consequently, has not recorded any income tax expense for the years ended December 31, 2018 and 2017 due to its net operating loss position.

The reconciliation of the federal statutory income tax rate to the Company’s effective tax rate for the years ended December 31, 2018 and 2017 are as follows:

	Year Ended December 31,
	2018			2017
Tax at statutory federal rate		-21.00	%		-34.00	%
State Tax (benefit)—net of federal benefit		-0.03	%		0.00	%
Permanent differences		0.68	%		0.60	%
R&D credits		-0.76	%		-1.64	%
Derecognition due to Sec. 382 and 383 limitations		-20.16	%		54.08	%
Change in valuation allowance		39.33	%		-52.90	%
Federal tax rate change		0.00	%		33.89	%
Other		1.94	%		-0.03	%
Effective tax rate		—			—

Significant components of the Company’s deferred tax assets as of December 31, 2018 and 2017 consist of the following (in thousands):

	Year Ended December 31,
	2018			2017
Deferred tax assets:
Accruals and reserves	$	751		$	1,112
Net operating loss carry forwards		23,559			11,519
R&D tax credit carry forwards		3,772			3,545
Fixed and intangible assets		3			89
Valuation Allowance		(28,085	)		(16,265	)
Net deferred tax assets:	$	—		$	—

Based on the available objective evidence at December 31, 2018, the Company does not believe it is more likely than not that the net deferred tax assets will be realizable. Accordingly, the Company has provided a full valuation allowance against its net deferred tax assets at December 31, 2018 and 2017.

As of December 31, 2018, after consideration of certain limitations (see below), the Company had approximately $112.1 million federal and $64.6 million state net operating loss carryforwards (“NOL”) available to reduce future taxable income which, if unused, will begin to expire in 2032 for federal and 2028 for state tax purposes.

As of December 31, 2018, the Company also had tax credit carry forwards available to offset future tax liabilities of approximately $0.2 million for federal and $4.5 million for state. If unused, the federal credit will begin to expire in 2037 and the state tax credit does not expire.

If the Company experiences a greater than 50 percentage point aggregate change in ownership over a three-year period (a Section 382 ownership change), utilization of its pre-change NOL carryforwards are subject to annual limitation under Section 382 of the Internal Revenue Code (California has similar provisions). The annual limitation is determined by multiplying the value of the Company's stock at the time of such ownership change by the applicable long-term tax-exempt rate. Such limitations may result in expiration of a portion of the NOL carryforwards before utilization. The Company determined that ownership changes occurred December 31, 2007, August 20, 2015, April 13, 2017, and February 15, 2018. Approximately $80.1 million and $14.2 million of the NOLs will expire unutilized for federal and California purposes, respectively. The Company has derecognized NOL related deferred tax assets in the tax affected amounts of $16.8 million and $0.0 million for federal and California purposes, respectively.

All of the federal R&D credits could expire unutilized, whereas none of the California R&D credits are subject to expiration. Approximately $6.1 million of gross federal R&D credit-related deferred tax assets were derecognized due to the Section 383 limitation. The ability of the Company to use its remaining NOL carryforwards may be further limited if the Company experiences a Section 382 ownership change as a result of future changes in its stock ownership.

Accounting for Uncertainty in Income Taxes

The Company only recognizes tax benefits if it is more likely than not that they will be sustained upon audit by the relevant tax authority based upon their technical merits. An uncertain tax position will not be recognized if it has less than a 50% likelihood of being sustained.

The Company had approximately $1.6 million and $1.5 million of unrecognized tax benefits as of December 31, 2018 and 2017, respectively. As the Company has a full valuation allowance on its deferred tax assets, the unrecognized tax benefits have reduced the deferred tax assets and the valuation allowance in the same amount. The Company does not expect the amount of unrecognized tax benefits to materially change in the next twelve months.

A reconciliation of the beginning and ending balance of the unrecognized tax benefits is as follows (in thousands):

Beginning Balance at January 1, 2017	$	1,539
Increase/(Decrease) of unrecognized tax benefits taken in prior years		(126	)
Increase/(Decrease) of unrecognized tax benefits related to current year		62
Ending Balance at December 31, 2017	$	1,475
Increase/(Decrease) of unrecognized tax benefits taken in prior years		13
Increase/(Decrease) of unrecognized tax benefits related to current year		85
Ending Balance at December 31, 2018	$	1,573

Interest and penalties related to unrecognized tax benefits would be included as income tax expense in the Company’s consolidated statements of operations. As of December 31, 2018 and 2017, the Company had not recognized any tax-related penalties or interest in its consolidated financial statements.

The Company files income tax returns in the United States federal, California, New Jersey, and Maryland state jurisdictions. The Company is not currently under examination by income tax authorities in federal, state or other jurisdictions. As of December 31, 2018 and 2017, the Company had no uncertain tax positions which affected its financial position as its results of operations or its cash flow, and will continue to evaluate for uncertain tax positions in the future. The Company is subject to United States federal and state income tax examinations by authorities for all tax years due to accumulated net operating losses that are being carried forward for tax purposes.

Collaborations

12 Months Ended

Dec. 31, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Collaborations

12.	Collaborations

Pfizer

Pursuant to the termination agreement entered on December 8, 2016, in connection with the termination of a prior license and development agreement, Pfizer granted the Company an exclusive license to Pfizer’s proprietary rights for manufacturing materials and processes that apply to Factor VIIa variants, CB 813a and MarzAA. Pfizer also transferred to the Company the IND application and documentation related to the development, manufacturing and testing of the Factor VIIa products as well as the orphan drug designation. The Company agreed to make contingent cash payments to Pfizer in an aggregate amount equal to up to $17.5 million, payable upon the achievement of clinical, regulatory and commercial milestones. Following commercialization of any covered product, Pfizer would also receive a single-digit royalty on net product sales on a country-by-country basis for a predefined royalty term. In February 2018, the Company paid Pfizer a $1 million milestone payment based on the dosing of the first patient in the ongoing Phase 2 study.

ISU Abxis

In December 2018, the Company entered into an amended and restated license agreement with ISU Abxis (the “A&R ISU Abxis Agreement”), which amended and restated in full its previous license and collaboration agreement with ISU Abxis entered into in September 2013, as subsequently amended in October 2014 and December 2016 (the “Original ISU Abxis Agreement”). Under the A&R ISU Abxis Agreement, ISU Abxis will receive commercialization rights in South Korea to DalcA and the Company will receive clinical development and commercialization rights in the rest of world (excluding South Korea) and manufacturing development and manufacturing rights worldwide (including South Korea). The A&R ISU Abxis Agreement eliminates the profit-sharing arrangement in the Original ISU Abxis Agreement and provides for a low single-digit royalty payment to ISU Abxis, on a country-by-country basis, for net product sales of DalcA by the Company or its affiliates in each country other than South Korea. Pursuant to the A&R ISU Abxis Agreement, the Company will also make up to an aggregate of $19.5 million in milestone payments to ISU Abxis, inclusive of $2.5 million in regulatory and development milestone payments and up to $17 million in commercial milestone payments, if the applicable milestones are met.

Under the Original ISU Abxis Agreement, ISU Abxis paid the Company an up-front signing fee of $1.75 million and was obligated to pay to the Company contingent milestone-based payments on the occurrence of certain defined development events, and reimbursement for a portion of the Company’s costs relating to intellectual property filings and maintenance thereof on products.

Contract revenue of $0.0 million and $0.3 million for the years ended December 31, 2018 and 2017, respectively, reflects (i) the amortization of the up-front fee over the estimated period of our performance obligations, under the Original ISU Abxis Agreement, which concluded in February 2018, and (ii) milestone payments received under the ISU Abxis Original ISU Abxis Agreement, which were recognized through February 2018, of which the Company received $0 and $0.9 million for the years ended December 31, 2018 and 2017, respectively. The adoption of the new revenue standards resulted in a $0.2 million cumulative adjustment to the Company’s opening balance of accumulated deficit as of January 1, 2018. The deferred revenue balance related to the ISU Abxis collaboration was $0 and $0.2 million as of December 31, 2018 and 2017, respectively.

Interest and Other Income

12 Months Ended

Dec. 31, 2018

Other Income And Expenses [Abstract]

Interest and Other Income

13.	Interest and Other Income

The following table shows the detail of other income, net for the years ended December 31, 2018 and 2017 (in thousands):

	Year Ended December 31,
	2018			2017
Interest income	$	2,229		$	215
Dividend income		4			50
Miscellaneous income (expense) ⁽¹⁾		1,650			(1	)
Loss on disposal of property and equipment		(116	)		(3	)
Total other income, net	$	3,767		$	261

(1)	$1.7 million miscellaneous income is mainly composed of a $1.5 million milestone payment received under an agreement associated with neuronal nicotinic receptor (“NNR”) assets sold in 2016.

Stockholders' Equity

12 Months Ended

Dec. 31, 2018

Equity [Abstract]

Stockholders' Equity

14.	Stockholders’ Equity

At the Market Issuance Sales Agreement — On March 16, 2016, the Company signed a Capital on Demand^TM Sales Agreement with JonesTrading Institutional Services LLC (“JonesTrading”). In accordance with the terms of the sales agreement, the Company was able to offer and sell shares of its common stock having a gross aggregate offering price up to $6.5 million, subject to certain limitations, from time to time in one or more public offerings of the Company’s common stock, with JonesTrading acting as agent, in transactions pursuant to a shelf registration statement that was declared effective by the SEC on April 28, 2016.

The Company sold an aggregate of 479,681 shares of common stock in the open market at a weighted-average selling price of $13.55 per share, for net proceeds (net of commissions) of $6.3 million through December 31, 2017, of which $5.5 million were sold in the year ended December 31, 2017, in the Capital on Demand program. The Company charged approximately $0.2 million for JonesTrading commission against additional paid-in capital through December 31, 2017. As of December 31, 2017, the Company has no common stock available for sale under the program.

April 2017 Underwritten Public Offering — On April 12, 2017, the Company issued and sold in a registered, underwritten public offering an aggregate of (i) 1,470,000 shares of common stock (including 540,000 shares of common stock sold pursuant to the exercise of the Underwriter’s overallotment option), (ii) 13,350 shares of Series A Preferred Stock, each convertible into 200 shares of common stock and (iii) warrants to purchase 2,070,000 shares of common stock at an exercise price of $5.50 per share (including 270,000 sold pursuant to the exercise of the Underwriter’s overallotment option). The net proceeds to the Company, after deducting the underwriting discounts and commissions and offering expenses payable by the Company were approximately $18.6 million.

Series A Convertible Preferred Stock — In connection with the closing on April 12, 2017 of the public offering, the Company filed the Certificate of Designation of Preferences, Rights and Limitations of the Series A Preferred Stock (the “Certificate of Designation”) with the Secretary of State of the State of Delaware. The Certificate of Designation describes the rights, preferences and privileges of the shares of Series A Preferred Stock. With certain exceptions, the shares of Series A Preferred Stock rank on par with the shares of the Common Stock, in each case, as to dividend rights and distributions of assets upon liquidation, dissolution or winding up of the Company.

Upon its issuance, the Series A Preferred Stock was not considered a liability or temporary equity and as such the Series A Preferred Stock was recorded in permanent equity on the Company’s balance sheet.

During the years ended December 31, 2018 and 2017, 3,680 and 9,670 shares of the Company’s Series A Preferred Stock were converted into 736,000 and 1,934,000 shares of common stock of the Company. As of December 31, 2018, there were no shares of Series A Preferred Stock issued and outstanding.

Beneficial Conversion Feature Series A Preferred Stock (deemed dividend) — Each share of Series A Preferred Stock was convertible into 200 shares of common stock, at any time, at the option of the holder. The net proceeds to the Company of $18.6 million were allocated to the common stock, Preferred A Stock and warrants (see below) based on a relative fair value basis. This resulted in $10.1 million being allocated to the Preferred A Stock and resulted in an effective conversion price of $3.80 per share. On April 12, 2017, the date of issuance of the Series A Preferred Stock, the publicly traded common stock price was $5.28 per share.

Based on the guidance in ASC 470-20-20, the Company determined that a beneficial conversion feature exists, as the effective conversion price for the shares of Series A Preferred Stock at issuance was less than the fair value of the common stock into which the shares of Series A Preferred Stock are convertible. The beneficial conversion feature calculated based on the intrinsic value as of the date of issuance was approximately $4.0 million. This amount was then accreted as a deemed dividend, which is a non-cash transaction. As the conversion rights were 100% effective at the time of issuance, the deemed dividend was immediately charged to accumulated deficit.

Warrants — In connection with the closing on April 12, 2017 of the public offering and the overallotment option, the Company issued warrants to purchase 2,070,000 shares of common stock at an exercise price of $5.50 per share. Upon their issuance, the common stock warrants were determined to be equity instruments under ASC 480 and ASC 815-40. The net proceeds allocated to the warrants based on a relative fair value basis resulted in $5.0 million being allocated to the warrants. As of December 31, 2018, the Company has no warrants outstanding associated with this offering.

The following is a summary of warrant activity for the year ended December 31, 2018 and 2017:

	Number of Shares
	Underlying Warrants			Exercise Price
Outstanding — December 31, 2016		12,039		$	145.11
Issued		2,070,000		$	5.50
Exercised		(330,331	)	$	5.50
Outstanding — December 31, 2017		1,751,708
Issued		—
Exercised		(1,735,419	)	$	5.50
Forfeited/Cancelled⁽¹⁾		(6,095	)	$	5.50
Outstanding — December 31, 2018		10,194		$	155.73

(1)	In April 2018, 4,250 warrants were forfeited. In November 2018, 1,845 warrants were cancelled by Healthcare Ventures VIII.

December 2017 Underwritten Public Offering — On December 20, 2017, the Company entered into an underwriting agreement with JonesTrading, in connection with a registered firm commitment underwritten public offering of 1,105,263 shares of the Company’s common stock, pursuant to a shelf registration statement that was declared effective by the SEC on April 28, 2016. On December 22, 2017 the Company sold an aggregate of 1,105,263 shares of common stock at a price to the public of at $9.50 per share. The net proceeds to the Company, after deducting the underwriting discounts and commissions and offering expenses payable by the Company were approximately $9.7 million.

February 2018 Underwritten Public Offering — On February 13, 2018, the Company entered into an underwriting agreement with JonesTrading, in connection with a registered firm commitment underwritten public offering of 2,941,176 shares of common stock, pursuant to a shelf registration statement that was declared effective by the SEC on February 6, 2018. On February 15, 2018 the Company sold 3,382,352 shares of common stock (including 441,176 shares of common stock sold pursuant to the exercise of the underwriters’ overallotment option) at a price to the public of $34.00 per share. The net proceeds to the Company, after deducting the underwriting discounts and commissions and offering expenses payable by the Company were approximately $106.8 million.

Net Loss per Share Attributable to Common Stockholders

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Net Loss per Share Attributable to Common Stockholders

15.	Net Loss per Share Attributable to Common Stockholders

The following table sets forth the computation of the basic and diluted net loss per common share during the years ended December 31, 2018 and 2017 (in thousands, except share and per share data):

	Year Ended December 31,
	2018			2017
Net loss attributable to common stockholders	$	(30,055	)	$	(25,512	)
Weighted-average number of shares used in computing net loss per share, basic and diluted		11,213,884			3,423,901
Net loss per share, basic and diluted	$	(2.68	)	$	(7.45	)

Since the Company was in a loss position for all periods presented, diluted net loss per share is the same as basic net loss per share for all periods as the inclusion of all potential common shares outstanding would have been anti-dilutive. Potentially dilutive securities on an as-if converted basis that were not included in the diluted per share calculations because they would be anti-dilutive were as follows:

	Year Ended December 31,
	2018		2017
Options to purchase common stock		1,361,977		821,741
Convertible preferred stock ⁽¹⁾		—		736,000
Common stock warrants		10,194		1,751,708
Redeemable convertible notes		—		36,883
Total		1,372,171		3,346,332

(1)	As of December 31, 2017, represents 3,680 shares of Series A Preferred Stock on an as converted basis to 0.7 million shares of common stock.

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements include the accounts of the Company and its subsidiary. Intercompany accounts and transactions have been eliminated in consolidation. The Company’s consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles (“GAAP”).
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to revenue recognition, convertible notes and related warrants up to the date of conversion, common stock and stock-based compensation. The Company bases its estimates on various assumptions that the Company believes to be reasonable under the circumstances. Actual results could differ from those estimates.
Accounting Pronouncements Recently Adopted	Accounting Pronouncements Recently Adopted In November 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-18, Restricted Cash, which requires amounts generally described as restricted cash and restricted cash equivalents be included with cash and cash equivalents when reconciling the total beginning and ending amounts for the periods shown on the statement of cash flows. We adopted ASU 2016-18 effective January 1, 2018, using a retrospective transition method to each period presented. The adoption of this ASU changed previously reported amounts in the condensed consolidated statement of cash flows for the year ended December 31, 2017, by increasing our cash flows from financing activities by $5.3 million as compared to previously reported amounts for the prior year period. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments. The standard provides guidance on how certain cash receipts and payments are presented and classified in the statement of cash flows. The standard is intended to reduce current diversity in practice. The Company adopted ASU 2016-15 effective January 1, 2018, and this guidance did not have an impact on the Company’s financial statements. In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments – Overall (Topic 825-10), which updates certain aspects of recognition, measurement, presentation and disclosure of financial instruments. Subsequently, in February 2018, the FASB issued ASU No. 2018-03, Technical Corrections and Improvements to Financial Instruments - Overall (Topic 825-10), which clarifies certain aspects of ASU 2016-01, which includes provisions to accounting for equity investments, financial liabilities under the fair value option and presentation and disclosure requirements for financial instruments. The amended guidance requires equity securities, except for those accounted for under the equity method of accounting, with determinable fair values to be measured at fair value with changes in fair value recognized in net income (loss). The Company adopted ASU 2016-01 and 2018-03 effective January 1, 2018, and this guidance did not have a material impact on the Company’s financial statements, as the Company only has debt securities. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), which amends the existing accounting standards for revenue recognition. ASU 2014-09 is based on principles that govern the recognition of revenue at an amount an entity expects to be entitled when products are transferred to customers. Subsequently, the FASB has issued the following standards related to ASU 2014-09: ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations; ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing; and ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients, (collectively, the “new revenue standards”). The Company adopted the new revenue standards effective January 1, 2018, using the modified retrospective method through a cumulative adjustment to equity. The Company has identified that the most significant change relates to its accounting for collaboration arrangements with multiple deliverables, in particular, the ISU Abxis agreement. Under the old guidance, such deliverables and consideration must be accounted for under a single unit of accounting along with other arrangement deliverables and consideration that does not have stand-alone value and are recognized as revenue over the estimated period that the performance obligations are to be performed. Under the current new standard however, the total arrangement consideration is allocated to each performance obligation based on its estimated stand-alone selling price and revenue is recognized as each performance obligation is satisfied. As a result, revenue for this transaction is recorded in an earlier period than under the old guidance, resulting in a $0.2 million increase to the Company’s opening balance of accumulated deficit as of January 1, 2018. Adopting ASU No. 2014-09, Revenue from Contracts with Customers, or the new revenue standard, involved new estimates and judgments related to the estimates of stand-alone selling prices and the allocation of discounts and variable consideration in allocating the transaction price. The Company recognized revenue earlier under the current new standard and may have more variability due to significant estimates involved under the new accounting guidance. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (“ASU 2016-02”), which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. Originally, entities were required to adopt ASU 2016-02 using a modified retrospective approach at the beginning of the earliest comparative period presented in the financial statements and the recognition of a cumulative-effect adjustment to the opening balance of retained earnings. The FASB subsequently issued ASU No. 2018-10 and ASU No. 2018-11 in July 2018, which provide clarifications and improvements to ASU 2016-02 (collectively, the “new lease standard”). ASU No. 2018-11 a also provides the optional transition method which allows companies to apply the new lease standard at the adoption date instead of at the earliest comparative period presented and continue to apply the provisions of the previous lease standard in its annual disclosures for the comparative periods. The new lease standard requires lessees to present a right-of-use (“ROU”) asset and a corresponding lease liability on the balance sheet. Lessor accounting is substantially unchanged compared to the current accounting guidance. Additional footnote disclosures related to leases will also be required. On January 1, 2019, the Company adopted the new lease standard using the optional transition method. The comparative financial information will not be restated and will continue to be reported under the previous lease standard in effect during those periods. In addition, the new lease standard provides a number of optional practical expedients in transition. The Company elected the package of practical expedients. As such, the Company will not reassess whether expired or existing contracts are or contain a lease; will not need to reassess the lease classifications or reassess the initial direct costs associated with expired or existing leases. The Company did not elect the use-of-hindsight or the practical expedient pertaining to land easements; the latter not being applicable to the Company. The new lease standard also provides practical expedients for an entity’s ongoing accounting. The Company elected the short-term lease recognition exemption for all leases that qualify. This means, for those leases that qualify, the Company will not recognize ROU assets or lease liabilities, and this includes not recognizing ROU assets or lease liabilities for existing short-term leases of those assets in transition. The Company elected the practical expedient to not separate lease and non-lease components for certain classes of assets. On January 1, 2019, the Company expects to recognize ROU assets of $2.5 million and lease liabilities of $2.3 million. The Company does not expect the adoption of the new lease standard to impact its consolidated statement of operations or its consolidated statement of cash flows.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company invests its excess cash in bank deposits, consisting primarily of money market mutual funds. The Company considers all highly liquid investments with original maturities of three months or less from the date of purchase to be cash equivalents.
Restricted Cash	Restricted Cash Restricted cash at December 31, 2018 consists of a certain certificate of deposit account that is pledged as collateral for the Company’s corporate credit card program. Restricted cash at December 31, 2017 consisted of certain checking, money market and certificate of deposit accounts that are: (i) pledged to or held in a segregated escrow account by the Company’s correspondent banks for the benefit of the holders of the redeemable convertible notes in order to facilitate the payment of the redeemable convertible notes upon redemption or at maturity as discussed in Note 4 – Fair Value Measurements or (ii) pledged as collateral for the Company’s corporate credit card and deposit for its facility lease.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company applies fair value accounting for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The fair value hierarchy requires that an entity maximize the use of observable inputs when estimating fair value. The fair value hierarchy includes the following three-level classification which is based on the market observability of the inputs used for estimating the fair value of the assets or liabilities being measured: Level 1 – Quoted prices in active markets for identical assets or liabilities. Level 2 – Observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 – Inputs that are generally unobservable and typically reflect management’s estimate of assumptions that market participants would use in pricing the asset or liability.
Property and Equipment	Property and Equipment Property and equipment are stated at cost, less accumulated depreciation. Depreciation is computed using the straight-line method over the estimated useful lives of the respective assets, which are three years for computer equipment and software, and three to seven years for furniture and leasehold improvements.
Investments	Investments All investments have been classified as “available-for-sale” and are carried at estimated fair value as determined based upon quoted market prices or pricing models for similar securities. Management determines the appropriate classification of its investments at the time of purchase and reevaluates such designation as of each balance sheet date. Unrealized gains and losses are excluded from earnings and are reported as a component of comprehensive loss. Realized gains and losses and declines in fair value determined to be other-than-temporary, if any, on available-for-sale securities are included in interest and other income. The cost of securities sold is based on the specific-identification method. Interest on short-term investments is included in interest and other income.
Derivative Liability	Derivative Liability The embedded redemption feature in the redeemable convertible notes, which were convertible into shares of the Company’s common stock was bifurcated and was accounted for as a derivative liability at its estimated fair value. The derivative was subject to remeasurement at the end of each reporting period, with changes in fair value recognized as a component of interest and other income, in the consolidated statements of operations. These notes were repaid in 2018. The Company adjusted the liability for changes in fair value until the earlier of the conversion, redemption or maturity of the redeemable convertible notes. At December 31, 2017 the fair value was $0.
Revenue Recognition	Revenue Recognition Effective January 1, 2018, the Company adopted Accounting Standards Codification (“ASC”) 606 using the modified retrospective method through a cumulative adjustment to equity, which resulted in an immaterial $0.2 million decrease to our opening balance of accumulated deficit as of January 1, 2018. The Company enters into collaboration arrangements that may include the receipt of payments for up-front license fees, success-based milestone payments, full time equivalent based payments for research services, product supplies, and royalties on any future sales of commercialized products that result from the collaborations. In determining the appropriate amount of revenue to be recognized as it fulfills its obligations under its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations based on estimated selling prices; and (v) recognition of revenue when the Company satisfies each performance obligation. At the inception of each arrangement that includes variable consideration such as development milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price which is then allocated to each relevant performance obligation. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. As part of the accounting for these arrangements, the Company must develop assumptions that require judgment to determine the timing of recognition and the stand-alone selling price for each performance obligation identified in the contract. The Company uses key assumptions to determine the stand-alone selling price, which may include forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success. Estimated selling prices for licenses are calculated using the residual approach if the Company has not yet established a price for such license and the license has not previously been sold on a standalone basis. Otherwise, selling prices for licenses are determined using an income approach model and include key assumptions such as: development timeline, revenue forecast, commercialization expenses, discount rate and probabilities of technical and regulatory success. To estimate selling prices for research services and product supply, the Company uses a cost-plus margin approach.
Research and Development Expenses	Research and Development Expenses Research and development costs are expensed as incurred. Research and development costs consist of payroll and other personnel-related expenses, laboratory supplies and reagents, contract research and development services, and consulting costs, as well as allocations of facilities and other overhead costs. Under the Company’s collaboration agreements, certain specific expenditures are reimbursed by third parties. During the years ended December 31, 2018 and 2017, the Company recorded a reduction to research and development expenses of $0.05 million and $0.1 million, respectively related to these reimbursements.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash and cash equivalents, investments and restricted cash. The Company’s investment policy restricts cash investments to high credit quality, investment grade investments. The Company believes that it has established guidelines for investment of its excess cash that maintain safety and liquidity through its policies on diversification and investment maturity. The Company is exposed to credit risk in the event of default by the institutions holding the cash and cash equivalents to the extent of the amounts recorded on the balance sheets. The Company’s accounts receivable, included in prepaid and other current assets, at December 31, 2018 was $0.01 million, due from ISU Abxis, see Note 12. The Company has incurred no credit losses to date. The Company does not require collateral from its collaboration partners.
Income Taxes	Income Taxes Income taxes are computed using the liability method. Deferred tax assets and liabilities are determined based on the differences between the financial reporting and tax basis of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. The Company follows the authoritative guidance on accounting for uncertainty in income taxes. This guidance prescribes a more-likely-than-not threshold for financial statement recognition and measurement of a tax position taken in the Company’s income tax returns. This interpretation also provides guidance on accounting for interest and penalties and associated with tax positions, accounting for income taxes in interim periods and income tax disclosures. The Company’s policy is to include penalties and interest expense related to income taxes as a component of other expense and interest expense, respectively, as necessary.
Stock-Based Compensation	Stock-Based Compensation The Company measures the cost of employee and director services received in exchange for an award of equity instruments based on the fair value of the award on the date of grant and recognizes the related expense over the period during which the employee or director is required to provide service in exchange for the award on a straight-line basis. The Company uses the Black-Scholes option-pricing valuation model to estimate the grant-date fair value of stock-based awards. The determination of fair value for stock-based awards on the date of grant using an option-pricing model requires management to make certain assumptions regarding a number of variables. Upon adoption of ASU 2016-09, the Company can make an accounting policy election to either estimate the number of share-based awards that are expected to vest, or account for forfeitures when they occur. The Company elected to account for forfeitures when they occur. As such, the Company recognizes stock-based compensation expense, over their requisite service period, based on the vesting provisions of the individual grants. For nonemployee stock-based awards, the measurement date on which the fair value of the stock-based award is calculated is equal to the earlier of (i) the date at which a commitment for performance by the counterparty to earn the equity instrument is reached or (ii) the date at which the counterparty’s performance is complete. The Company recognizes stock-based compensation expense for the fair value-based measurement of the nonemployee awards using the Black Scholes option-pricing valuation model and the awards are typically subject to periodic re-measurement over the period that services are rendered.
Deferred Rent	Deferred Rent The Company’s facilities lease agreement provides for an escalation of rent payments each year. The Company records rent expense on a straight-line basis over the term of the lease. The difference between the amount of expense recognized and the amount of rent paid is recorded as deferred rent in the accompanying consolidated balance sheets.
Net Loss per Share	Net Loss per Share Basic net loss per share is calculated by dividing the net loss by the weighted average number of shares of common stock outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive given the net loss of the Company for all periods presented.

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Assets and Liabilities Measured at Fair Value on a Recurring Basis

The following tables present the fair value hierarchy for assets and liabilities measured at fair value on a recurring basis as of December 31, 2018 and 2017 (in thousands):

	December 31, 2018
	Level 1		Level 2		Level 3		Total
Financial assets:
Money market funds⁽¹⁾	$	29,090	$	—	$	—	$	29,090
Federal agency securities⁽¹⁾		—		999		—		999
Restricted cash ⁽²⁾		50		—		—		50
U.S. Treasury securities⁽³⁾		74,139		—		—		74,139
Federal agency securities⁽³⁾		—		14,775		—		14,775
Total financial assets	$	103,279	$	15,774	$	—	$	119,053

(1)	Included in cash and cash equivalents on accompanying consolidated balance sheets.

(2)	$0.05 million of restricted cash serves as collateral for the Company’s corporate credit card.

(3)	Included in short-term investments on accompanying consolidated balance sheets and are classified as available-for-sale securities.

	December 31, 2017
	Level 1		Level 2		Level 3		Total
Financial assets:
Money market funds⁽¹⁾	$	14,334	$	—	$	—	$	14,334
U.S. Treasury securities⁽³⁾		16,471		—		—		16,471
Restricted cash⁽²⁾		5,333		—		—		5,333
Federal agency securities⁽³⁾		—		1,500		—		1,500
Total financial assets	$	36,138	$	1,500	$	—	$	37,638

(1)	Included in cash and cash equivalents on accompanying consolidated balance sheets.

(2)	$5.3 million of restricted cash in the Indenture (see Note 9) serves as full collateral for the redeemable convertible notes.

(3)	Included in short-term investments on accompanying consolidated balance sheets and are classified as available-for-sale securities.

Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2018

Investments All Other Investments [Abstract]

Cash Equivalents, Restricted Cash and Short-Term Investments Classified as Available-for-sale Securities

Cash equivalents, restricted cash and short-term investments which are classified as available-for-sale securities, consisted of the following (in thousands):

-December 31, 2018	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Money market funds (cash equivalents)	$	29,090	$	—	$	—		$	29,090
Agency securities (cash equivalents)		999		—	$	—			999
Restricted cash		50		—		—			50
U.S. government agency securities		74,144		1		(6	)		74,139
Agency securities		14,774		1		—			14,775
Total financial assets	$	119,057	$	2	$	(6	)	$	119,053
Classified as:
Cash and cash equivalents								$	30,089
Short-term investments									88,914
Restricted cash									50
								$	119,053

December 31, 2017	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Money market funds	$	14,334	$	—	$	—		$	14,334
U.S. government agency securities		16,473		—		(2	)		16,471
Restricted cash		5,330		3		—			5,333
Agency securities		1,500		—		—			1,500
Total financial assets	$	37,637	$	3	$	(2	)	$	37,638
Classified as:
Cash and cash equivalents								$	14,334
Short-term investments									17,971
Restricted cash									5,333
								$	37,638

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2018

Property Plant And Equipment [Abstract]

Schedule of Property and equipment

Property and equipment consisted of the following (in thousands):

	Year Ended December 31,
	2018			2017
Furniture	$	226		$	317
Leasehold improvements		84			1,598
Computer equipment		222			237
Software		139			147
		671			2,299
Less accumulated depreciation and amortization		(285	)		(2,023	)
Property and equipment, net	$	386		$	276

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2018

Commitments And Contingencies Disclosure [Abstract]

Schedule of Future Minimum Lease Payments under All Non-cancelable Operating Leases

Future minimum lease payments under all non-cancelable operating leases at December 31, 2018, were as follows (in thousands):

2019	$	571
2020		587
2021		605
2022		617
2023		209
Total future minimum lease payments	$	2,589

Stock Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Summary of Option Activity Under Company's Equity Incentive Plans

The following table summarizes stock option activity under the Company’s equity incentive plans and related information:

	Number of Shares Underlying Outstanding Options			Weighted- Average Exercise Price		Weighted-Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value (thousands)
Outstanding — December 31, 2016		140,990		$	128.25		3.93		—
Options granted		742,000		$	4.56
Options forfeited		(61,249	)	$	165.63
Outstanding — December 31, 2017		821,741		$	13.69		9.17	$	6,376
Options granted		612,050		$	13.13
Options exercised		(12,716	)	$	4.17			$	213
Options canceled/forfeited		(43,315	)	$	7.76
Options expired		(15,783	)	$	158.81
Outstanding — December 31, 2018		1,361,977		$	12.04		8.71	$	2,294
Exercisable — December 31, 2018		414,584		$	17.98
Vested and expected to vest — December 31, 2018		1,361,977		$	12.04
Shares available to be granted — December 31, 2018		1,295,144

Summary of Stock-Based Compensation Recognized

Total stock-based compensation recognized was as follows (in thousands):

	Year Ended December 31,
	2018		2017
Research and development	$	590	$	164
General and administrative⁽¹⁾		1,990		699
Total stock-based compensation	$	2,580	$	863

(1)

2018 includes $0.1 million in modification stock-based compensation expense related to a Board member’s separation agreement.

Employee Stock Option

Summary of Weighted Average Valuation Assumptions Used to Estimate Fair Value

	Year Ended December 31,
	2018			2017
Employee Stock Options:
Expected term (in years)		6.04			6.03
Risk-free interest rate		2.67	%		2.03	%
Dividend yield		—			—
Volatility		92.61	%		110.29	%

Non Employee Stock Option

Summary of Weighted Average Valuation Assumptions Used to Estimate Fair Value

The estimated grant-date fair value of the nonemployee stock options was determined using the Black-Scholes valuation model and the following assumptions:

	Year Ended December 31,
	2018	2017
Non-Employee Stock Options:
Contractual Life (in years)	N/A		9
Risk-free interest rate	N/A		2.35	%
Dividend yield	N/A		—
Volatility	N/A		111.55	%

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Reconciliation of Federal Income Tax Rate to Company's Effective Tax Rate

The reconciliation of the federal statutory income tax rate to the Company’s effective tax rate for the years ended December 31, 2018 and 2017 are as follows:

	Year Ended December 31,
	2018			2017
Tax at statutory federal rate		-21.00	%		-34.00	%
State Tax (benefit)—net of federal benefit		-0.03	%		0.00	%
Permanent differences		0.68	%		0.60	%
R&D credits		-0.76	%		-1.64	%
Derecognition due to Sec. 382 and 383 limitations		-20.16	%		54.08	%
Change in valuation allowance		39.33	%		-52.90	%
Federal tax rate change		0.00	%		33.89	%
Other		1.94	%		-0.03	%
Effective tax rate		—			—

Components of the Company's Deferred Tax Assets (Liabilities)

Significant components of the Company’s deferred tax assets as of December 31, 2018 and 2017 consist of the following (in thousands):

	Year Ended December 31,
	2018			2017
Deferred tax assets:
Accruals and reserves	$	751		$	1,112
Net operating loss carry forwards		23,559			11,519
R&D tax credit carry forwards		3,772			3,545
Fixed and intangible assets		3			89
Valuation Allowance		(28,085	)		(16,265	)
Net deferred tax assets:	$	—		$	—

Unrecognized Tax Benefits

A reconciliation of the beginning and ending balance of the unrecognized tax benefits is as follows (in thousands):

Beginning Balance at January 1, 2017	$	1,539
Increase/(Decrease) of unrecognized tax benefits taken in prior years		(126	)
Increase/(Decrease) of unrecognized tax benefits related to current year		62
Ending Balance at December 31, 2017	$	1,475
Increase/(Decrease) of unrecognized tax benefits taken in prior years		13
Increase/(Decrease) of unrecognized tax benefits related to current year		85
Ending Balance at December 31, 2018	$	1,573

Interest and Other Income (Tables)

12 Months Ended

Dec. 31, 2018

Other Income And Expenses [Abstract]

Detail of Other Income, Net

The following table shows the detail of other income, net for the years ended December 31, 2018 and 2017 (in thousands):

	Year Ended December 31,
	2018			2017
Interest income	$	2,229		$	215
Dividend income		4			50
Miscellaneous income (expense) ⁽¹⁾		1,650			(1	)
Loss on disposal of property and equipment		(116	)		(3	)
Total other income, net	$	3,767		$	261

(1)	$1.7 million miscellaneous income is mainly composed of a $1.5 million milestone payment received under an agreement associated with neuronal nicotinic receptor (“NNR”) assets sold in 2016.

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2018

Equity [Abstract]

Summary of Warrant Activity

The following is a summary of warrant activity for the year ended December 31, 2018 and 2017:

	Number of Shares
	Underlying Warrants			Exercise Price
Outstanding — December 31, 2016		12,039		$	145.11
Issued		2,070,000		$	5.50
Exercised		(330,331	)	$	5.50
Outstanding — December 31, 2017		1,751,708
Issued		—
Exercised		(1,735,419	)	$	5.50
Forfeited/Cancelled⁽¹⁾		(6,095	)	$	5.50
Outstanding — December 31, 2018		10,194		$	155.73

(1)	In April 2018, 4,250 warrants were forfeited. In November 2018, 1,845 warrants were cancelled by Healthcare Ventures VIII.

- Definition

Tabular disclosure of warrants or rights issued. Warrants and rights outstanding are derivative securities that give the holder the right to purchase securities (usually equity) from the issuer at a specific price within a certain time frame. Warrants are often included in a new debt issue to entice investors by a higher return potential. The main difference between warrants and call options is that warrants are issued and guaranteed by the company, whereas options are exchange instruments and are not issued by the company. Also, the lifetime of a warrant is often measured in years, while the lifetime of a typical option is measured in months. Disclose the title of issue of securities called for by warrants and rights outstanding, the aggregate amount of securities called for by warrants and rights outstanding, the date from which the warrants or rights are exercisable, and the price at which the warrant or right is exercisable.

+ References + Details

Net Loss per Share Attributable to Common Stockholders (Tables)

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Basic and Diluted Net Loss Per Common Share

The following table sets forth the computation of the basic and diluted net loss per common share during the years ended December 31, 2018 and 2017 (in thousands, except share and per share data):

	Year Ended December 31,
	2018			2017
Net loss attributable to common stockholders	$	(30,055	)	$	(25,512	)
Weighted-average number of shares used in computing net loss per share, basic and diluted		11,213,884			3,423,901
Net loss per share, basic and diluted	$	(2.68	)	$	(7.45	)

Anti-dilutive Security not Included In Diluted per Share Calculations

	Year Ended December 31,
	2018		2017
Options to purchase common stock		1,361,977		821,741
Convertible preferred stock ⁽¹⁾		—		736,000
Common stock warrants		10,194		1,751,708
Redeemable convertible notes		—		36,883
Total		1,372,171		3,346,332

(1)	As of December 31, 2017, represents 3,680 shares of Series A Preferred Stock on an as converted basis to 0.7 million shares of common stock.

Nature of Operations - Additional Information (Detail)	12 Months Ended
Nature of Operations - Additional Information (Detail)	Dec. 31, 2018 Segment
Accounting Policies [Abstract]
Number of operating segment	1

Liquidity - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Liquidity [Abstract]
Accumulated deficit	$ 203,342	$ 173,494
Cash, cash equivalents and short-term investments	120,100
Net loss	30,055	21,561
Cash used in operations	$ 28,553	$ 19,940

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019	Jan. 01, 2018
Summary Of Significant Accounting Policies [Line Items]
Increase in cash flows from financing activities as compared to previously reported amounts	$ 111,332,000	$ 21,082,000
Cumulative adjustment to accumulated deficit		207,000
Lease practical expedients	true
Derivative liability		0
Reduction to research and development expenses	$ 50,000	100,000
Software
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives	3 years
Computer equipment
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives	3 years
Furniture \| Minimum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives	3 years
Furniture \| Maximum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives	7 years
Leasehold improvements \| Minimum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives	3 years
Leasehold improvements \| Maximum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives	7 years
Subsequent Event
Summary Of Significant Accounting Policies [Line Items]
Right of use assets			$ 2,500,000
Lease liabilities			$ 2,300,000
Accumulated Deficit
Summary Of Significant Accounting Policies [Line Items]
Cumulative adjustment to accumulated deficit		$ 207,000
ISU Abxis
Summary Of Significant Accounting Policies [Line Items]
Accounts receivable	$ 10,000
ASU 2016-18
Summary Of Significant Accounting Policies [Line Items]
Increase in cash flows from financing activities as compared to previously reported amounts	$ 5,300,000
ASU 2014-09 \| ISU Abxis \| Difference between Revenue Guidance in Effect before and after Topic 606 \| Accumulated Deficit
Summary Of Significant Accounting Policies [Line Items]
Cumulative adjustment to accumulated deficit				$ 200,000

Fair Value Measurements - Additional Information (Detail)	Dec. 31, 2017 USD ($)
Fair Value Disclosures [Abstract]
Derivative liability	$ 0

Assets and Liabilities Measured at Fair Value (Detail) - USD ($)
$ in Thousands

Dec. 31, 2018

Dec. 31, 2017

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Assets, fair value

$ 119,053

$ 37,638

Money Market Funds

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Assets, fair value

^[1]

29,090

14,334

Restricted cash

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Assets, fair value

^[2]

5,333

^[3]

Federal Agency Securities | Cash and Cash Equivalents

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Assets, fair value

^[1]

999

Federal Agency Securities | Short-Term Investments

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Assets, fair value

^[4]

14,775

1,500

U.S. Treasury Securities | Short-Term Investments

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Assets, fair value

^[4]

74,139

16,471

Fair Value, Inputs, Level 1

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Assets, fair value

103,279

36,138

Fair Value, Inputs, Level 1 | Money Market Funds

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Assets, fair value

^[1]

29,090

14,334

Fair Value, Inputs, Level 1 | Restricted cash

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Assets, fair value

^[2]

5,333

^[3]

Fair Value, Inputs, Level 1 | U.S. Treasury Securities | Short-Term Investments

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Assets, fair value

^[4]

74,139

16,471

Fair Value, Inputs, Level 2

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Assets, fair value

15,774

1,500

Fair Value, Inputs, Level 2 | Federal Agency Securities | Cash and Cash Equivalents

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Assets, fair value

^[1]

999

Fair Value, Inputs, Level 2 | Federal Agency Securities | Short-Term Investments

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Assets, fair value

^[4]

$ 14,775

$ 1,500

[1]	Included in cash and cash equivalents on accompanying consolidated balance sheets.
[2]	$0.05 million of restricted cash serves as collateral for the Company’s corporate credit card.
[3]	$5.3 million of restricted cash in the Indenture (see Note 9) serves as full collateral for the redeemable convertible notes.
[4]	Included in short-term investments on accompanying consolidated balance sheets and are classified as available-for-sale securities.

Assets and Liabilities Measured at Fair Value (Parenthetical) (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Collateral for Corporate Credit Card
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted cash	$ 50
Collateral for Redeemable Convertible Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted cash		$ 5,300

Cash Equivalents, Restricted Cash and Short-Term Investments Classified as Available-for-sale Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 119,057	$ 37,637
Gross Unrealized Gains	2	3
Gross Unrealized Losses	(6)	(2)
Estimated Fair Value	119,053	37,638
Restricted cash
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	50	5,330
Gross Unrealized Gains		3
Estimated Fair Value	50	5,333
Money Market Funds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		14,334
Estimated Fair Value		14,334
Money Market Funds \| Cash Equivalents
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	29,090
Estimated Fair Value	29,090
U.S. Government Agency Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	74,144	16,473
Gross Unrealized Gains	1
Gross Unrealized Losses	(6)	(2)
Estimated Fair Value	74,139	16,471
Cash and Cash Equivalents
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	30,089	14,334
Short-Term Investments
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	88,914	17,971
Agency Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,774	1,500
Gross Unrealized Gains	1
Estimated Fair Value	14,775	$ 1,500
Agency Securities \| Cash Equivalents
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	999
Estimated Fair Value	$ 999

Financial Instruments - Additional Information (Detail)	12 Months Ended
Financial Instruments - Additional Information (Detail)	Dec. 31, 2018 USD ($)
Financial Instrument [Line Items]
Material realized gains or losses on available-for-sale securities	$ 0
Maximum
Financial Instrument [Line Items]
Available for sale securities contractual maturities	1 year

Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 671	$ 2,299
Less accumulated depreciation and amortization	(285)	(2,023)
Property and equipment, net	386	276
Software
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	139	147
Furniture
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	226	317
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	84	1,598
Computer equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 222	$ 237

Property and Equipment - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property Plant And Equipment [Abstract]
Depreciation expense	$ 0.1	$ 0.2

Commitments and Contingencies - Additional Information (Detail)	1 Months Ended			12 Months Ended
	Dec. 31, 2018 USD ($)	Feb. 28, 2018 USD ($)	Nov. 30, 2017 ft²	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2013 USD ($)	Aug. 10, 2018 ft²	Dec. 08, 2016 USD ($)	May 20, 2016 USD ($)
Commitments And Contingencies Disclosure [Line Items]
Operating lease rent expense				$ 400,000	$ 800,000
License fees payable						$ 100,000
South San Francisco, California \| New Office Lease Agreement
Commitments And Contingencies Disclosure [Line Items]
Leased area \| ft²			8,606
Operating lease term of contract			5 years 2 months
Operating lease commencement date			Feb. 16, 2018
South San Francisco, California \| Office Lease Agreement
Commitments And Contingencies Disclosure [Line Items]
Leased area \| ft²							4,626
Pfizer Inc \| Collaboration Agreement
Commitments And Contingencies Disclosure [Line Items]
Milestone payment		$ 1,000,000
Pfizer Inc \| Collaboration Agreement \| Maximum
Commitments And Contingencies Disclosure [Line Items]
Obligated to make milestone and royalty payments upon achievement of clinical, regulatory and commercial milestones								$ 17,500,000
AGC Biologics, Inc \| Dalcinonacog alfa (“DalcA”)
Commitments And Contingencies Disclosure [Line Items]
Contractual obligation payments	$ 3,400,000			3,400,000					$ 5,600,000
AGC Biologics, Inc \| MarzAA
Commitments And Contingencies Disclosure [Line Items]
Contractual obligation payments	300,000			300,000					$ 3,800,000
ISU Abxis \| Maximum
Commitments And Contingencies Disclosure [Line Items]
Potential milestone payments				$ 2,000,000
ISU Abxis \| Amended and Restated License Agreement
Commitments And Contingencies Disclosure [Line Items]
Regulatory and development milestone payment	2,500,000
ISU Abxis \| Amended and Restated License Agreement \| Maximum
Commitments And Contingencies Disclosure [Line Items]
Milestone payment	19,500,000
Commercial milestone payments	$ 17,000,000

Schedule of Future Minimum Lease Payments under All Non-cancelable Operating Leases (Detail) $ in Thousands	Dec. 31, 2018 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2019	$ 571
2020	587
2021	605
2022	617
2023	209
Total future minimum lease payments	$ 2,589

Related Parties - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Mosaic \| Strategic Research Collaboration to Develop Intravitreal Anti-Complement Factor 3 (C3) Products
Related Party Transaction [Line Items]
Expenses related to collaboration	$ 1,300	$ 30

Redeemable Convertible Notes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Aug. 19, 2015
Debt Instrument [Line Items]
Redeemable convertible notes, outstanding balance	$ 0	$ 5,085,000
Derivative liability		0
Convertible Notes
Debt Instrument [Line Items]
Convertible notes, total outstanding principal amount			$ 37,000,000
Convertible notes, maturity date	Feb. 19, 2018
Derivative liability	$ 0
Redeemable convertible notes, interest expense	$ 0	$ 0
Convertible Notes \| After Reverse Stock Split
Debt Instrument [Line Items]
Redeemable convertible notes, conversion per share price	$ 137.85

Stock Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Jun. 13, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted		612,050	742,000
Options, Outstanding, Weighted Average Exercise Price		$ 12.04	$ 13.69	$ 128.25
Stock-based compensation expense		$ 2,606	$ 863
Number of common stock available for future grant		1,295,144
Stock-based compensation expense		$ 2,580	$ 863
2018 Omnibus Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted	1,500,000
2018 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum employee subscription rate	15.00%
2018 Employee Stock Purchase Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of fair market value of common stock	85.00%
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term of stock options		6 years 14 days	6 years 10 days
Weighted average grant date fair value of stock options		$ 9.97	$ 4.01
Unrecognized employee stock based compensation expense		$ 6,500
Unrecognized employee stock based compensation expense, period for recognition		2 years 9 months 10 days
Non Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term of stock options			9 years
Options, Grants in Period		0	20,000
Options, Outstanding, Weighted Average Exercise Price			$ 4.69
Stock-based compensation expense		$ 90	$ 20
Non Employee Stock Option \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Vesting Period			1 year
Non Employee Stock Option \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Vesting Period			4 years
2018 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock authorized for issuance		120,000
Number of common stock stock issued		0
Number of common stock available for future grant		120,000
Stock-based compensation expense		$ 30

Summary of Option Activity Under Company's Equity Incentive Plans (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Shares Underlying Outstanding Options
Number of Shares Underlying Outstanding Options, Beginning Balance	821,741	140,990
Number of Shares Underlying Outstanding Options, Options granted	612,050	742,000
Number of Shares Underlying Outstanding Options, Options exercised	(12,716)
Number of Shares Underlying Outstanding Options, Options canceled/forfeited	(43,315)	(61,249)
Number of Shares Underlying Outstanding Options, Options expired	(15,783)
Number of Shares Underlying Outstanding Options, Ending Balance	1,361,977	821,741	140,990
Number of Shares Underlying Outstanding Options, Exercisable- December 31, 2018	414,584
Number of Shares Underlying Outstanding Options, Vested and expected to vest - December 31, 2018	1,361,977
Shares available to be granted - December 31, 2018	1,295,144
Weighted- Average Exercise Price
Weighted- Average Exercise Price, Beginning Balance	$ 13.69	$ 128.25
Weighted- Average Exercise Price, Options granted	13.13	4.56
Weighted- Average Exercise Price, Options exercised	4.17
Weighted- Average Exercise Price, Options Canceled/forfeited	7.76	165.63
Weighted- Average Exercise Price, Options expired	158.81
Weighted- Average Exercise Price, Ending Balance	12.04	$ 13.69	$ 128.25
Weighted- Average Exercise Price, Exercisable - December 31, 2018	17.98
Weighted- Average Exercise Price, Vested and expected to vest - December 31, 2018	$ 12.04
Weighted-Average Remaining Contractual Term (Years)
Weighted-Average Remaining Contractual Term (Years), Outstanding Balance	8 years 8 months 15 days	9 years 2 months 1 day	3 years 11 months 4 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Outstanding	$ 6,376
Aggregate Intrinsic Value, Options exercised	213
Aggregate Intrinsic Value, Outstanding	$ 2,294	$ 6,376

Fair Values of Stock Options Estimated Using Black-Scholes Valuation Model (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Black Scholes Method Used [Line Items]
Expected term (in years)	6 years 14 days	6 years 10 days
Risk-free interest rate	2.67%	2.03%
Dividend yield	0.00%	0.00%
Volatility	92.61%	110.29%
Non Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Black Scholes Method Used [Line Items]
Expected term (in years)		9 years
Risk-free interest rate		2.35%
Dividend yield	0.00%	0.00%
Volatility		111.55%

Summary of Stock-Based Compensation Recognized (Detail) - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2018

Dec. 31, 2017

Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]

Total stock-based compensation

$ 2,580

$ 863

Research and development

Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]

Total stock-based compensation

590

164

General and Administrative

Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]

Total stock-based compensation

^[1]

$ 1,990

$ 699

[1]	2018 includes $0.1 million in modification stock-based compensation expense related to a Board member’s separation agreement.

Summary of Stock-Based Compensation Recognized (Parenthetical) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 2,580	$ 863
Board Member’s Separation Agreement
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 100

Reconciliation of Statutory Federal Income Tax (benefit) Rate to Company's Effective Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Tax at statutory federal rate	(21.00%)	(34.00%)
State Tax (benefit)—net of federal benefit	(0.03%)	(0.00%)
Permanent differences	0.68%	0.60%
R&D credits	(0.76%)	(1.64%)
Derecognition due to Sec. 382 and 383 limitations	(20.16%)	54.08%
Change in valuation allowance	39.33%	(52.90%)
Federal tax rate change	(0.00%)	33.89%
Other	1.94%	(0.03%)

Components of Company's Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Accruals and reserves	$ 751	$ 1,112
Net operating loss carry forwards	23,559	11,519
R&D tax credit carry forwards	3,772	3,545
Fixed and intangible assets	3	89
Valuation Allowance	$ (28,085)	$ (16,265)

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2007
Income Tax [Line Items]
Gross federal R&D tax credit-related deferred tax assets derecognized	$ 6,100,000
Unrecognized tax benefit	1,573,000	$ 1,475,000	$ 1,539,000
Tax-related penalties or interest recognized	0	0
Uncertain tax positions	0	$ 0
Federal Income Tax
Income Tax [Line Items]
Net operating loss carryforwards	$ 112,100,000			$ 80,100,000
Net operating loss carryforwards expiration year	2032
Tax credit carryforwards available to offset future federal tax liabilities	$ 200,000
Credit carryforward, expire period	Dec. 31, 2037
Net operating loss carryforward,derecognized	$ 16,800,000
State Income Tax
Income Tax [Line Items]
Net operating loss carryforwards	$ 64,600,000
Net operating loss carryforwards expiration year	2028
Tax credit carryforwards available to offset future federal tax liabilities	$ 4,500,000
CALIFORNIA
Income Tax [Line Items]
Net operating loss carryforwards	14,200,000
Net operating loss carryforward,derecognized	$ 0

Unrecognized tax benefit (Detail) - USD ($) $ in Thousands	12 Months Ended
Unrecognized tax benefit (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Beginning Balance	$ 1,475	$ 1,539
Increase/(Decrease) of unrecognized tax benefits taken in prior years	13	(126)
Increase/(Decrease) of unrecognized tax benefits related to current year	85	62
Ending Balance	$ 1,573	$ 1,475

Collaborations - Additional Information (Detail) - USD ($)		1 Months Ended		12 Months Ended
	Sep. 16, 2013	Dec. 31, 2018	Feb. 28, 2018	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2018	Dec. 08, 2016
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Contract revenue				$ 6,000	$ 1,018,000
Milestone payment received				1,500,000
Cumulative adjustment to accumulated deficit		$ (203,342,000)		(203,342,000)	(173,494,000)
Pfizer Inc \| Collaboration Agreement
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Milestone payment			$ 1,000,000
Pfizer Inc \| Collaboration Agreement \| Maximum
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Contingent cash payments upon achievement of clinical, regulatory and commercial milestones							$ 17,500,000
ISU Abxis
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Contract revenue				0	300,000
Milestone payment received				0	900,000
Deferred revenue		0		$ 0	$ 200,000
ISU Abxis \| Up Front Payment
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Amount received for research and development process	$ 1,750,000
ISU Abxis \| Difference between Revenue Guidance in Effect before and after Topic 606 \| ASU 2014-09
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Cumulative adjustment to accumulated deficit						$ 200,000
ISU Abxis \| Amended and Restated License Agreement
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Regulatory and development milestone payment		2,500,000
ISU Abxis \| Amended and Restated License Agreement \| Maximum
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Milestone payment		19,500,000
Commercial milestone payments		$ 17,000,000

Detail of Other Income, Net (Detail) - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2018

Dec. 31, 2017

Other Income And Expenses [Abstract]

Interest income

$ 2,229

$ 215

Dividend income

Miscellaneous income (expense)

^[1]

1,650

(1)

Loss on disposal of property and equipment

(116)

(3)

Total other income, net

$ 3,767

$ 261

[1]	$1.7 million miscellaneous income is mainly composed of a $1.5 million milestone payment received under an agreement associated with neuronal nicotinic receptor (“NNR”) assets sold in 2016.

Detail of Other Income, Net (Parenthetical) (Detail) - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2018

Dec. 31, 2017

Other Income And Expenses [Abstract]

Miscellaneous income (expense)

^[1]

$ 1,650

$ (1)

Milestone payment received

$ 1,500

[1]	$1.7 million miscellaneous income is mainly composed of a $1.5 million milestone payment received under an agreement associated with neuronal nicotinic receptor (“NNR”) assets sold in 2016.

Stockholders' Equity - Additional Information (Detail) - USD ($)						12 Months Ended		22 Months Ended
	Feb. 15, 2018	Feb. 13, 2018	Dec. 22, 2017	Dec. 20, 2017	Apr. 12, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Mar. 16, 2016
Stockholders Equity Disclosure [Line Items]
Common stock, value of shares issued under sales agreement						$ 12,000	$ 6,000	$ 6,000
Net proceeds from sale of common stock	$ 106,800,000		$ 9,700,000		$ 18,600,000		$ 5,336,000
Warrants to purchase common stock					2,070,000
Warrants exercise price					$ 5.50	$ 155.73			$ 145.11
Preferred stock, shares issued						0	3,680	3,680
Preferred stock, shares outstanding						0	3,680	3,680
Net proceeds allocated to common stock, preferred A stock and warrants							$ 18,563,000
Common stock price, per share					$ 5.28
Proceeds allocated to warrants, net					$ 5,000,000
Number of warrants outstanding						10,194	1,751,708	1,751,708	12,039
Overallotment Option
Stockholders Equity Disclosure [Line Items]
Warrants to purchase common stock					270,000
April 2017 Underwritten Public Offering
Stockholders Equity Disclosure [Line Items]
Number of warrants outstanding						0
Series A Preferred Stock
Stockholders Equity Disclosure [Line Items]
Issuance of stock, shares					13,350
Conversion of each preferred stock to common stock					200
Number of shares converted						3,680	9,670
Preferred stock, shares issued						0
Preferred stock, shares outstanding						0	3,680	3,680
Net proceeds allocated to preferred stock							$ 10,100,000
Effective conversion price							$ 3.80	$ 3.80
Intrinsic value of preferred stock					$ 4,000,000
Effective percentage of conversion rights					100.00%
Common Stock
Stockholders Equity Disclosure [Line Items]
Issuance of stock, shares	3,382,352		1,105,263		1,470,000		439,880
Conversion of preferred stock to common stock						736,000	1,934,000
Common stock price, per share	$ 34.00		$ 9.50
Firm commitment underwritten public offering shares		2,941,176		1,105,263
Common Stock \| Overallotment Option
Stockholders Equity Disclosure [Line Items]
Issuance of stock, shares	441,176				540,000
Capital on Demand Sales Agreement with Jones Trading Institutional Services LLC
Stockholders Equity Disclosure [Line Items]
Issuance of stock, shares								479,681
Common stock weighted average selling price								$ 13.55
Net proceeds from sale of common stock							$ 5,500,000	$ 6,300,000
Commission against additional paid-in capital								$ 200,000
Common stock available for sale							0	0
Capital on Demand Sales Agreement with Jones Trading Institutional Services LLC \| Maximum
Stockholders Equity Disclosure [Line Items]
Common stock, value of shares issued under sales agreement										$ 6,500,000

Summary of Warrant Activity (Detail) - $ / shares	1 Months Ended	12 Months Ended
Summary of Warrant Activity (Detail) - $ / shares	Apr. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Warrants And Rights Note Disclosure [Abstract]
Number of Shares Underlying Warrants, Outstanding		1,751,708	12,039
Number of Shares Underlying Warrants, Issued			2,070,000
Number of Shares Underlying Warrants, Exercised		(1,735,419)	(330,331)
Number of Shares Underlying Warrants, Outstanding		10,194	1,751,708
Number of Shares Underlying Warrants, Forfeited/Cancelled	(4,250)	(6,095)
Warrants Outstanding, Exercise Price			$ 145.11
Warrants Issued, Exercise Price			5.50
Warrants Exercised, Exercise Price		$ 5.50	$ 5.50
Warrants Outstanding, Exercise Price		155.73
Warrants Forfeited/Cancelled, Exercise Price		$ 5.50

Summary of Warrant Activity (Parenthetical) (Detail) - shares	1 Months Ended		12 Months Ended
	Nov. 30, 2018	Apr. 30, 2018	Dec. 31, 2018
Class Of Warrant Or Right [Line Items]
Number of shares of warrants forfeited/cancelled		4,250	6,095
Healthcare Ventures VIII
Class Of Warrant Or Right [Line Items]
Number of shares of warrants forfeited/cancelled	1,845

Basic and Diluted Net Loss Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net loss attributable to common stockholders	$ (30,055)	$ (25,512)
Weighted-average number of shares used in computing net loss per share, basic and diluted	11,213,884	3,423,901
Net loss per share, basic and diluted	$ (2.68)	$ (7.45)

Anti-dilutive Security not Included In Diluted per Share Calculations (Detail) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti dilutive securities	1,372,171	3,346,332
Options To Purchase Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti dilutive securities	1,361,977	821,741
Convertible Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti dilutive securities		736,000
Common Stock Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti dilutive securities	10,194	1,751,708
Redeemable Convertible Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti dilutive securities		36,883

Anti-dilutive Security not Included In Diluted per Share Calculations (Parenthetical) (Detail) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Preferred stock, shares outstanding	0	3,680
Conversion of preferred stock to common stock	1,372,171	3,346,332
Series A Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Preferred stock, shares outstanding	0	3,680
Conversion of preferred stock to common stock		700,000