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Classification on the Cash Flow

Six Months Ended
June 30, 2019

Operating lease cost

Cash paid for amounts included in the measurement of lease liabilities

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Cover Page - shares	6 Months Ended
Cover Page - shares	Jun. 30, 2019	Aug. 05, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2019
Document Transition Report	false
Entity File Number	001-37985
Entity Registrant Name	ANAPTYSBIO, INC
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-3828755
Entity Address, Address Line One	10421 Pacific Center Court
Entity Address, Address Line Two	Suite 200
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92121
City Area Code	858
Local Phone Number	362-6295
Title of 12(b) Security	Common Stock, $0.001 par value
Trading Symbol	ANAB
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		27,047,596
Entity Central Index Key	0001370053
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 146,552	$ 113,596
Receivable from collaborative partners	5,000	0
Australian tax incentive receivable	0	174
Short-term investments	275,664	313,486
Prepaid expenses and other current assets	3,772	6,960
Total current assets	430,988	434,216
Property and equipment, net	1,481	1,445
Long-term investments	45,707	73,128
Other long-term assets	1,913	148
Restricted cash	60	60
Total assets	480,149	508,997
Current liabilities:
Accounts payable	10,921	5,443
Accrued expenses	14,102	8,761
Notes payable, current portion	4,781	7,574
Other current liabilities	819	58
Total current liabilities	30,623	21,836
Other long-term liabilities	1,105	796
Stockholders’ equity:
Preferred stock, $0.001 par value, 10,000 shares authorized and no shares, issued or outstanding at June 30, 2019 and December 31, 2018, respectively	0	0
Common stock, $0.001 par value, 500,000 shares authorized, 27,045 shares and 26,922 shares issued and outstanding at June 30, 2019 and December 31, 2018, respectively	27	27
Additional paid in capital	640,550	633,251
Accumulated other comprehensive income (loss)	574	(223)
Accumulated deficit	(192,730)	(146,690)
Total stockholders’ equity	448,421	486,365
Total liabilities and stockholders’ equity	$ 480,149	$ 508,997

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	10,000,000	10,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	27,044,527	26,922,000
Common stock, shares outstanding (in shares)	27,044,527	26,922,000

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Collaboration revenue	$ 5,000	$ 0	$ 5,000	$ 0
Operating expenses:
Research and development	27,350	10,583	47,981	22,393
General and administrative	4,307	3,832	8,448	7,779
Total operating expenses	31,657	14,415	56,429	30,172
Loss from operations	(26,657)	(14,415)	(51,429)	(30,172)
Other income (expense), net:
Interest expense	(281)	(436)	(601)	(887)
Interest income	2,957	1,297	5,945	2,482
Other income (expense), net	(41)	(64)	(34)	(127)
Total other income (expense), net	2,635	797	5,310	1,468
Loss before income taxes	(24,022)	(13,618)	(46,119)	(28,704)
Provision for income taxes	60	0	79	0
Net loss	(23,962)	(13,618)	(46,040)	(28,704)
Unrealized income (loss) on available for sale securities, net of tax of $99, $0, $214 and $0, respectively	370	124	797	(250)
Comprehensive loss	$ (23,592)	$ (13,494)	$ (45,243)	$ (28,954)
Net loss per common share:
Basic and diluted (in dollars per share)	$ (0.89)	$ (0.57)	$ (1.70)	$ (1.20)
Weighted-average number of shares outstanding:
Basic and diluted (in shares)	27,026	23,932	27,004	23,867

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Unrealized income (loss) on available for sale securities, tax	$ 99	$ 0	$ 214	$ 0

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (46,040)	$ (28,704)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	239	118
Stock-based compensation	6,510	4,808
Accretion/amortization of investments, net	(1,926)	(255)
Non-cash interest expense	332	317
Changes in operating assets and liabilities:
Receivable from collaborative partners	5,000	0
Australian tax incentive receivable	174	1,449
Prepaid expenses and other assets	1,435	(1,186)
Accounts payable and other liabilities	12,660	2,097
Net cash used in operating activities	(31,616)	(21,356)
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisition of investments	(132,313)	(90,411)
Sales and maturities of investments	200,267	90,031
Purchases of property and equipment	(421)	(536)
Net provided by (used in) investing activities	67,533	(916)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock, upon the exercise of stock options	789	1,469
Proceeds from issuance of common stock, upon the exercise of warrants	0	76
Payments on notes payable	(3,750)	(3,125)
Payments for offering costs, net	0	(280)
Net cash used in financing activities	(2,961)	(1,860)
Net increase (decrease) in cash, cash equivalents, and restricted cash	32,956	(24,132)
Cash, cash equivalents and restricted cash, beginning of period	113,656	81,249
Cash, cash equivalents and restricted cash, end of period	146,612	57,117
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION
Interest paid	301	585
Non-cash investing and financing activities:
Amounts accrued for property and equipment	$ 14	$ 194

CONSOLIDATED STATEMENT OF STOCKHOLDERS’ EQUITY Statement - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit
Stockholders' Equity, Beginning Balance at Dec. 31, 2017	$ 307,581	$ 24	$ 393,017	$ (426)	$ (85,034)
Stockholders' Equity, Beginning Balance (in shares) at Dec. 31, 2017		23,791,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under employee stock plans	72		72
Shares issued under employee stock plans (in shares)		9,000
Warrants exercised	75		75
Warrants exercised (in shares)		17,000
Stock-based compensation	2,260		2,260
Comprehensive income (loss), net	(375)			(375)
Net loss	(15,086)				(15,086)
Stockholders' Equity, Ending Balance at Mar. 31, 2018	294,527	$ 24	395,424	(801)	(100,120)
Stockholders' Equity, Ending Balance (in shares) at Mar. 31, 2018		23,817,000
Stockholders' Equity, Beginning Balance at Dec. 31, 2017	307,581	$ 24	393,017	(426)	(85,034)
Stockholders' Equity, Beginning Balance (in shares) at Dec. 31, 2017		23,791,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(28,704)
Stockholders' Equity, Ending Balance at Jun. 30, 2018	284,979	$ 24	399,370	(677)	(113,738)
Stockholders' Equity, Ending Balance (in shares) at Jun. 30, 2018		24,029,000
Stockholders' Equity, Beginning Balance at Mar. 31, 2018	294,527	$ 24	395,424	(801)	(100,120)
Stockholders' Equity, Beginning Balance (in shares) at Mar. 31, 2018		23,817,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under employee stock plans	1,397		1,397
Shares issued under employee stock plans (in shares)		212,000
Warrants exercised	1		1
Stock-based compensation	2,548		2,548
Comprehensive income (loss), net	124			124
Net loss	(13,618)				(13,618)
Stockholders' Equity, Ending Balance at Jun. 30, 2018	284,979	$ 24	399,370	(677)	(113,738)
Stockholders' Equity, Ending Balance (in shares) at Jun. 30, 2018		24,029,000
Stockholders' Equity, Beginning Balance at Dec. 31, 2018	486,365	$ 27	633,251	(223)	(146,690)
Stockholders' Equity, Beginning Balance (in shares) at Dec. 31, 2018		26,922,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under employee stock plans	574		574
Shares issued under employee stock plans (in shares)		84,000
Stock-based compensation	2,867		2,867
Comprehensive income (loss), net	427			427
Net loss	(22,078)				(22,078)
Stockholders' Equity, Ending Balance at Mar. 31, 2019	468,155	$ 27	636,692	204	(168,768)
Stockholders' Equity, Ending Balance (in shares) at Mar. 31, 2019		27,006,000
Stockholders' Equity, Beginning Balance at Dec. 31, 2018	$ 486,365	$ 27	633,251	(223)	(146,690)
Stockholders' Equity, Beginning Balance (in shares) at Dec. 31, 2018		26,922,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under employee stock plans (in shares)	122,705
Net loss	$ (46,040)
Stockholders' Equity, Ending Balance at Jun. 30, 2019	448,421	$ 27	640,550	574	(192,730)
Stockholders' Equity, Ending Balance (in shares) at Jun. 30, 2019		27,045,000
Stockholders' Equity, Beginning Balance at Mar. 31, 2019	468,155	$ 27	636,692	204	(168,768)
Stockholders' Equity, Beginning Balance (in shares) at Mar. 31, 2019		27,006,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under employee stock plans	215		215
Shares issued under employee stock plans (in shares)		39,000
Stock-based compensation	3,643		3,643
Comprehensive income (loss), net	370			370
Net loss	(23,962)				(23,962)
Stockholders' Equity, Ending Balance at Jun. 30, 2019	$ 448,421	$ 27	$ 640,550	$ 574	$ (192,730)
Stockholders' Equity, Ending Balance (in shares) at Jun. 30, 2019		27,045,000

Description of the Business	6 Months Ended
Description of the Business	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of the Business	Description of the Business AnaptysBio, Inc. (“we,” “us,” “our,” or the “Company”) was incorporated in the state of Delaware in November 2005. We are a biotechnology company developing first-in-class antibody product candidates focused on unmet medical needs in inflammation. We develop our product candidates using our proprietary, antibody discovery technology platform, which is designed to replicate, in vitro, the natural process of antibody generation. We currently generate revenue from milestones achieved under our collaborative research and development arrangements. Since our inception, we have devoted our primary effort to raising capital and research and development activities. Our financial support has been provided primarily from the sale of our common and preferred stock, as well as through funds received under our collaborative research and development agreements. Going forward, as we continue our expansion, we may seek additional financing and/or strategic investments. However, there can be no assurance that any additional financing or strategic investments will be available to us on acceptable terms, if at all. If events or circumstances occur such that we do not obtain additional funding, we will most likely be required to reduce our plans and/or certain discretionary spending, which could have a material adverse effect on our ability to achieve our intended business objectives. Management believes its currently available resources will provide sufficient funds to enable the Company to meet its operating plans for at least the next twelve months. The accompanying consolidated financial statements do not include any adjustments that might be necessary if we are unable to continue as a going concern.

Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2019

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Basis of Presentation

The accompanying unaudited consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission, or the SEC. Certain information and note disclosures normally included in annual financial statements prepared in accordance with U.S. generally accepted accounting principles, or U.S. GAAP, have been omitted. The accompanying unaudited consolidated financial statements include all known adjustments necessary for a fair presentation of the results of interim periods as required by U.S. GAAP. These adjustments consist primarily of normal recurring accruals and estimates that impact the carrying value of assets and liabilities. Also, certain reclassifications have been made to 2018 financial information to conform to the current year presentation of long-term liabilities on the Consolidated Balance Sheets. Operating results for the six months ended June 30, 2019 are not necessarily indicative of the results that may be expected for the year ending December 31, 2019. The financial statements should be read in conjunction with our audited financial statements for the year ended December 31, 2018, included in our Annual Form 10-K.

Basis of Consolidation

The accompanying consolidated financial statements include us and our wholly-owned Australian subsidiary. All intercompany accounts and transactions have been eliminated in consolidation. We operate in one reportable segment and our functional and reporting currency is the U.S. dollar.

Use of Estimates

The preparation of the accompanying consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates. We base our estimates and assumptions on historical experience when available and on various factors that we believe to be reasonable under the circumstances. We evaluate our estimates and assumptions on an ongoing basis. Our actual results could differ from these estimates under different assumptions or conditions.

Leases

Prior to January 1, 2019, we recorded our leases in accordance with Accounting Standard Codification (ASC) Topic 840, Leases, and all current leases were classified as operating leases. Rent expense was recognized on a straight-line basis over the terms of the leases and, accordingly, we recorded the cumulative difference between cash rent payments and the recognition of rent expense as a deferred rent liability. When an operating lease included lease incentives, such as a rent abatements or leasehold improvement allowances, or required fixed escalations of the minimum lease payments, the aggregate rental expense, including such incentives or increases, was recognized on a straight-line basis over the term of the lease.

Effective January 1, 2019, we adopted Accounting Standard Update (ASU) 2016-02, ASC 842, Leases, under which all outstanding leases continued to be classified as operating leases. Rent expense is recognized on a straight-line basis. When an operating lease includes rent abatements or requires fixed escalations of the minimum lease payments, the aggregate rental expense is recognized on a straight-line basis over the term of the lease. When an operating lease includes lease incentives such as leasehold improvement allowances, the lease incentive is included in the right-of-use, or “ROU”, asset. Operating lease ROU assets and operating lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at the date of adoption of ASC 842, or the lease commencement date. As our leases do not provide an implicit rate, we use our incremental borrowing rate based on the information available at commencement date in determining the present value of future payments. We account for fixed lease components separately from non-lease components.

Net Loss Per Common Share

Basic net loss per common share is computed by dividing net loss by the weighted-average number of common shares outstanding during the period. Diluted net loss per share is computed by dividing net loss by the weighted-average number of common equivalent shares outstanding for the period, as well as any dilutive effect from outstanding stock options and warrants using the treasury stock method. For each period presented, there is no difference in the number of shares used to calculate basic and diluted net loss per share.

The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share because to do so would be anti-dilutive (in common stock equivalent shares):



	Three Months Ended June 30,		Six Months Ended June 30,
(in thousands)	2019	2018	2019	2018
Options to purchase common stock	2,525	2,542	2,443	2,572
Warrants to purchase common stock	—	—	—	4
Total	2,525	2,542	2,443	2,576

Accounting Pronouncements Recently Adopted

In February 2016, the Financial Accounting Standards Board, or FASB, issued ASU 2016-02, Leases (Topic 842), which requires that lessees recognize a right-of-use, or “ROU”, asset and a related lease liability on the balance sheet for all leases with a term longer than 12 months. Topic 842 was subsequently amended by ASU 2018-01, Land Easement Practical Expedient for Transition to Topic 842; ASU 2018-10, Codification Improvements to Topic 842, Leases; ASU 2018-11, Targeted Improvements; and ASU 2019-01, Leases (Topic 842): Codification Improvements. ASU 2016-02 became effective for our annual reporting period beginning January 1, 2019, including interim periods thereafter. A modified retrospective transition approach is required, applying the new standard to all leases existing at the date of initial application. An entity may choose to use either (i) its effective date or (ii) the beginning of the earliest comparative period presented in the financial statements as its date of initial application. We adopted this standard on January 1, 2019 and used the effective date as our date of initial application. Upon adoption, we elected the package of transition practical expedients, which allowed us to carry forward prior conclusions related to whether any expired or existing contracts are or contain leases, the lease classification for any expired or existing leases and initial direct costs for existing leases. We also made an accounting policy election to not recognize leases with an initial term of 12 months or less within our consolidated balance sheets and to recognize those lease payments on a straight-line basis in our consolidated statements of operations over the lease term. Adoption of the new standard resulted in the recording of operating lease ROU assets and lease liabilities of approximately $2.1 million and $2.3 million as of January 1, 2019, respectively related to our real estate leases. Adoption of this new standard did not have a material impact on our consolidated statements of operations or cash flows.

Recent Accounting Pronouncements

In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments (Topic 326), which changes the accounting treatment for recognizing the impairment of financial assets. Under the new guidance, credit losses for certain types of financial instruments will be estimated based on expected losses. The new guidance also eliminates the other-than-temporary impairment model for available-for-sale (AFS) debt securities. Entities will begin to recognize credit losses on AFS debt securities as allowances rather than as reductions in the carrying value of the securities. Impairment that is not credit-related impairment will continue to be recognized in other comprehensive income and entities will no longer consider the length of time a security has been in an unrealized loss position when determining whether a credit loss exists. ASU 2016-13 becomes effective for annual and interim periods beginning after December 15, 2019; early adoption is permitted. We believe that the adoption of this standard will not have a material impact on our consolidated financial statements.

Balance Sheet Accounts and Supplemental Disclosures

6 Months Ended

Jun. 30, 2019

Balance Sheet Related Disclosures [Abstract]

Balance Sheet Accounts and Supplemental Disclosures

Property and Equipment

Property and equipment consist of the following:



(in thousands)	June 30, 2019			December 31, 2018
Laboratory equipment	$	4,528		$	4,287
Office furniture and equipment	807			780
Leasehold improvements	575			575
Property and equipment, gross	5,910			5,642
Less: accumulated depreciation and amortization	(4,429		)	(4,197		)
Total property and equipment, net	$	1,481		$	1,445

Accrued Expenses

Accrued expenses consist of the following:



(in thousands)	June 30, 2019		December 31, 2018
Accrued compensation and related expenses	$	1,909	$	2,421
Accrued professional fees	496		442
Accrued research, development and manufacturing expenses	11,360		5,577
Other	337		321
Total accrued expenses	$	14,102	$	8,761

Collaborative Research and Development Agreements

6 Months Ended

Jun. 30, 2019

Revenue Recognition [Abstract]

Collaborative Research and Development Agreements

TESARO Collaboration

In March 2014, we entered into a Collaboration and Exclusive License Agreement, or the TESARO Agreement, with TESARO, Inc. and TESARO Development, Inc., or collectively, TESARO, an oncology-focused biopharmaceutical company now a part of GlaxoSmithKline. Under the terms of the agreement, we agreed to perform certain discovery and early preclinical development of therapeutic antibodies with the goal of generating immunotherapy antibodies for subsequent preclinical, clinical, regulatory and commercial development to be performed by TESARO. Under the terms of the agreement, TESARO paid an upfront license fee of $17.0 million in March 2014 and agreed to provide funding to us for research and development services related to antibody discovery programs for three specific targets. In November 2014, we and TESARO entered into Amendment No. 1 to the Agreement to add an antibody discovery program against an undisclosed fourth target for an upfront license fee of $2.0 million.

For each development program, we are eligible to receive milestone payments of up to $18.0 million if certain preclinical and clinical trial events are achieved by TESARO, up to an additional $90.0 million if certain U.S. and European regulatory submissions and approvals in multiple indications are achieved, and up to an additional $165.0 million upon the achievement of specified levels of annual worldwide net sales. We will also be eligible to receive tiered single-digit royalties related to

worldwide net sales of products developed under the collaboration. Unless earlier terminated by either party upon specified circumstances, the agreement will terminate, with respect to each specific developed product, upon the latter of the 12th anniversary of the first commercial sale of the product or the expiration of the last to expire of any patent. Prior to the adoption of ASC 606, Revenue from Contracts with Customers, we determined that the upfront license fees and research funding under the agreement, as amended, should be accounted for as a single unit of accounting and that the upfront license fees should be deferred and recognized as revenue over the same period that the research and development services are performed. In December 2015, we determined that the research and development services would be extended through December 31, 2016. As a result, the period over which the unrecognized license fees and milestones were recognized was extended through December 31, 2016, and have since been recognized in full.

We assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, TESARO, is a customer. We identified the following material promises under the TESARO Agreement: (1) the licenses under certain patent rights relating to six discovery programs (four targets) and transfer of certain development and regulatory information, (2) R&D services and (3) Joint Steering Committee meetings. We considered the research and discovery capabilities of TESARO for these specific programs, TESARO’s inability to sub-license, and the fact that the discovery and optimization of these antibodies is proprietary and could not, at the time of the contract inception, be provided by other vendors, to conclude that the license does not have stand-alone functionality and is therefore not distinct. Additionally, we determined that the steering committee participation would not have been provided without the R&D services and license agreement. Based on these assessments, we identified all services to be interrelated, and therefore concluded that the promises should be combined into a single performance obligation at the inception of the arrangement.

As of June 30, 2019, the transaction price includes the upfront payment, research reimbursement revenue, and milestones earned to date, which are allocated in their entirety to the single performance obligation. Future potential milestones are generally not included as they are subject to revenue constraint. As part of the constraint evaluation, we considered numerous factors including the fact that the receipt of milestones is outside of our control and contingent upon success in future clinical trials, an outcome that is difficult to predict, and the licensees’ efforts. Any consideration related to sales-based milestones, including royalties, will be recognized when the related sales occur as they were determined to relate predominantly to the IP license granted to TESARO and therefore have also been excluded from the transaction price. We will re-evaluate the variable transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. During the three months ended June 30, 2019, we recognized one clinical milestone for $5.0 million which we expect to be achieved during the second half of 2019. This milestone was recognized upon the evaluation of recent actions, efforts, and public disclosures made by TESARO that led to the determination that a significant reversal of revenue would not be probable. No other future clinical or regulatory milestones have been included in the transaction price, as all other milestone amounts continued to be subject to the revenue constraint.

Milestones recognized through June 30, 2019 under the TESARO Agreement are as follows:



	Anti-PD-1 (TSR042/Dostarlimab)		Anti-TIM-3 (TSR022)		Anti-LAG-3 (TSR033)
Milestone Event	Amount	Quarter Recognized	Amount	Quarter Recognized	Amount	Quarter Recognized
Initiated in vivo toxicology studies using good laboratory practices (GLPs)	$1.0M	Q2'15	$1.0M	Q4'15	$1.0M	Q3'16
IND clearance from the FDA	$4.0M	Q1'16	$4.0M	Q2'16	$4.0M	Q2'17
Phase 2 clinical trial initiation	$3.0M	Q2'17	$3.0M	Q4'17	—	—
Phase 3 clinical trial initiation - first indication	$5.0M	Q3'18	—	—	—	—
Phase 3 clinical trial initiation - second indication	$5.0M	Q2'19	—	—	—	—

Milestones achieved during the discovery period were recognized as revenue pro-rata through December 31, 2016. Milestones achieved during fiscal 2017 were recognized as revenue in the period earned, while milestones after December 31, 2017 are recognized upon determination that a significant reversal of revenue would not be probable. Cash is generally received within 30 days of milestone achievement.

We recognized $5.0 million in revenue under this agreement during the three and six months ended June 30, 2019 and no revenue during the three and six months ended June 30, 2018.

Antibody Generation Agreement with Celgene Corporation

In December 2011, we entered into a license and collaboration agreement with Celgene, or the Celgene Agreement, to develop therapeutic antibodies against multiple targets. We granted Celgene the option to obtain worldwide commercial rights to antibodies generated against each of the targets under the agreement, which option was triggered on a target-by-target basis by our delivery of antibodies meeting certain pre-specified parameters pertaining to each target under the agreement.

The agreement provided for an upfront payment of $6.0 million from Celgene, which we received in 2011 and recognized through 2014, milestone payments of up to $53.0 million per target, low single-digit royalties on net sales of antibodies against each target, and reimbursement of specified research and development costs.

We assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, Celgene, is a customer. We identified the following material promises under the Celgene Agreement: (1) the licenses under certain patent rights relating to four targets and transfer of certain development and regulatory information, (2) R&D services, (3) a written report documenting findings and (4) Steering Committee meetings. We considered the research and discovery capabilities of Celgene, Celgene’s inability to sub-license the four targets, and the fact that the discovery and optimization of these antibodies is proprietary and could not, at the time of the contract inception, be provided by other vendors, to conclude that the license does not have stand-alone functionality and is therefore not distinct. Additionally, we determined that the report of findings and steering committee participation would not have been provided without the R&D services and license agreement. Based on these assessments, we identified all services to be interrelated, and therefore concluded that the promises should be combined into a single performance obligation at the inception the arrangement.

As of June 30, 2019, the transaction price includes the upfront payment, success fees, expense reimbursement, and milestones earned to date, which are allocated in their entirety to the single performance obligation. None of the future clinical or regulatory milestones have been included in the transaction price, as all milestone amounts were subject to the revenue constraint. As part of the constraint evaluation, we considered numerous factors, including the fact that the receipt of milestones is outside of our control and contingent upon success in future clinical trials and the licensees’ efforts. Any consideration related to sales-based milestones, including royalties, will be recognized when the related sales occur as they were determined to relate predominantly to the IP license granted to Celgene and therefore have also been excluded from the transaction price. We will re-evaluate the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur.

Milestones achieved through June 30, 2019 under the Celgene Agreement are as follows:



	Anti-PD-1 (CC-90006)
Milestone Event	Amount	Quarter Recognized
Completion of first in vivo toxicology studies using GLPs	$0.5M	Q2'16
Phase 1 clinical trial initiation	$1.0M	Q4'16

Revenue from future contingent milestone payments are recognized upon determination that a significant reversal of revenue would not be probable. Cash is generally received within 30 days of milestone achievement.

There was no revenue recognized under this agreement during the three and six months ended June 30, 2019 and 2018.

Notes Payable	6 Months Ended
Notes Payable	Jun. 30, 2019
Debt Disclosure [Abstract]
Notes Payable	Notes Payable On December 24, 2014, we entered into a Loan and Security Agreement, as amended from time to time, the Loan Agreement, with a bank and a financial institution whereby we may borrow up to $15.0 million in three separate draws of $5.0 million each. The Term A Loans, for an aggregate of $5.0 million, were drawn on December 24, 2014 with a fixed interest rate of 6.97%. In January 2016, the Loan Agreement was amended to combine Term B Loans and Term C Loans for a total of $10.0 million available for draw through December 31, 2016 and delay the beginning of our Term A Loans’ principal repayments from February 1, 2016 until February 1, 2017. The Term B Loans and Term C Loans became available for draw on July 1, 2016. In December 2016, we further amended the Loan Agreement to (i) allow for the Term B Loans and Term C Loans to be drawn on December 30, 2016, (ii) delay principal repayments of all Term Loans until February 1, 2018 and (iii) amend the interest rate for each Term Loan. The Term B Loans and the Term C Loans were drawn on December 30, 2016, and Term A, B and C Loans are now collectively referred to as the Term Loans. Principal repayments began in February 2018, and as of June 30, 2019, there are 7 monthly principal and interest payments remaining on the Term Loans, with final maturity in January 2020. The Term Loans bear interest equal to the greater of 3-month U.S. LIBOR plus 6.37% or 7.3%. The interest rate was 8.87% as of June 30, 2019. The costs incurred to issue the Term Loans were deferred and are included in the discount to the carrying value of the Term Loans in the accompanying balance sheet. The Term Loans also include a final payment fee of $0.8 million due at the earlier of prepayment or the maturity date of the Term Loans. The deferred costs and the final payment fee are being amortized to interest expense over the expected term of the Term A Loans using the effective interest method. As of June 30, 2019, the carrying amount of the Term Loans was $4.8 million, which includes amortized final payment fees of $0.4 million and is classified as current liabilities as of June 30, 2019. The effective interest rate on the Term Loans at June 30, 2019 was 13.27%. As of June 30, 2019, future principal maturities of the Term Loans were $3.8 million and $0.6 million during the remainder of 2019 and 2020, respectively. The Term Loans are secured by a first priority interest in most of our assets, excluding intellectual property. As of June 30, 2019, we were in compliance with the covenants contained in the Loan Agreement.

Fair Value Measurements and Available for Sale Investments

6 Months Ended

Jun. 30, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements and Available for Sale Investments

Fair Value Measurements

Our financial instruments consist principally of cash, cash equivalents, restricted cash, short-term and long-term investments, receivables, accounts payable, and notes payable. Certain of our financial assets and liabilities have been recorded at fair value in the consolidated balance sheet in accordance with the accounting standards for fair value measurements.

Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants on the measurement date. Accounting guidance also establishes a fair value hierarchy that requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The standard describes three levels of inputs that may be used to measure fair value:

Level 1 - Observable inputs that reflect quoted prices (unadjusted) for identical assets or liabilities in active markets.

Level 2 - Inputs are observable, unadjusted quoted prices in active markets for similar assets or liabilities, unadjusted quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and

Level 3 - Unobservable inputs that are supported by little or no market activities, therefore requiring an entity to develop its own assumptions.

Assets and Liabilities Measured at Fair Value on a Recurring Basis

The following table summarizes our assets and liabilities that require fair value measurements on a recurring basis and their respective input levels based on the fair value hierarchy:



	Fair Value Measurements at End of Period Using:
(in thousands)	Fair Value		Quoted Market Prices for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
At June 30, 2019
Money market funds⁽¹⁾	$	127,844	$	127,844	$	—	$	—
Mutual funds⁽¹⁾	8,170		8,170		—		—
U.S. Treasury securities⁽²⁾	112,676		112,676		—		—
Certificates of deposit⁽²⁾	6,155		—		6,155		—
Agency securities⁽²⁾	61,684		—		61,684		—
Commercial and corporate obligations⁽¹⁾⁽²⁾	145,907		—		145,907		—
At December 31, 2018
Money market funds⁽¹⁾	$	87,213	$	87,213	$	—	$	—
Mutual funds⁽¹⁾	7,967		7,967		—		—
U.S. Treasury securities⁽²⁾	164,245		164,245		—		—
Certificates of deposit⁽²⁾	4,784		—		4,784		—
Agency securities⁽¹⁾⁽²⁾	81,296		—		81,296		—
Commercial and corporate obligations⁽¹⁾⁽²⁾	153,983		—		153,983		—


⁽¹⁾	Included in cash and cash equivalents, and restricted cash in the accompanying consolidated balance sheets.


⁽²⁾	Included in short-term or long-term investments in the accompanying consolidated balance sheets depending on the respective maturity date.

The following methods and assumptions were used to estimate the fair value of our financial instruments for which it is practicable to estimate that value:

Marketable Securities. For fair values determined by Level 1 inputs, which utilize quoted prices in active markets for identical assets, the level of judgment required to estimate fair value is relatively low. For fair values determined by Level 2 inputs, which utilize quoted prices in less active markets for similar assets, the level of judgment required to estimate fair value is also considered relatively low.

Fair Value of Other Financial Instruments

The fair value of our other financial instruments estimated as of June 30, 2019 and December 31, 2018 are presented below:



	June 30, 2019				December 31, 2018
	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Notes payable	$	4,781	$	5,084	$	8,199	$	8,806

The following methods and assumptions were used to estimate the fair value of our notes payable:

Notes Payable—We use the income approach to value the aforementioned debt instrument. We use a present value calculation to discount principal and interest payments and the final maturity payment on these liabilities using a discounted cash flow model based on observable inputs. We discount these debt instruments based on what the current market rates would offer us as of the reporting date. Based on the assumptions used to value these liabilities at fair value, these debt instruments are categorized as Level 2 in the fair value hierarchy.

The carrying amounts of certain of our financial instruments, including cash and cash equivalents, Australian tax incentive receivable, accounts payable, and accrued expenses approximate fair value due to their short-term nature.

Available for Sale Investments

We invest our excess cash in agency securities, debt instruments of financial institutions and corporations, commercial obligations, and U.S. Treasury securities, which we classify as available-for-sale investments. These investments are carried at fair value and are included in the tables above. The aggregate market value, cost basis, and gross unrealized gains and losses of available-for-sale investments by security type, classified in cash equivalents, short-term and long-term investments as of June 30, 2019 are as follows:



(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Total Fair Value
Agency securities⁽¹⁾	$	61,558	$	133	$	(7	)	$	61,684
Certificates of deposit⁽²⁾	6,111		44		—			6,155
Commercial and corporate obligations⁽³⁾	145,548		366		(7		)	145,907
U.S. Treasury securities⁽⁴⁾	112,363		319		(6		)	112,676
Total available-for-sale investments	$	325,580	$	862	$	(20	)	$	326,422


⁽¹⁾	Of our outstanding agency securities, $47.8 million have maturity dates of less than one year and $13.9 million have a maturity date of between one to two years as of June 30, 2019.


⁽²⁾	Of our outstanding certificates of deposit, $1.0 million have a maturity date of less than one year and $5.2 million have a maturity date of between one to two years as of June 30, 2019.


⁽³⁾	Of our outstanding commercial and corporate obligations, $131.9 million have maturity dates of less than one year and $14.0 million have a maturity date of between one to two years as of June 30, 2019.

⁽⁴⁾

Of our outstanding U.S. Treasury securities $100.1 million have maturity dates of less than one year and $12.6 million have a maturity date of between one to two years as of June 30, 2019.

- 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

Stockholders' Equity

6 Months Ended

Jun. 30, 2019

Equity [Abstract]

Stockholders' Equity

Stockholders’ Equity

Common Stock

Of the 500,000,000 shares of common stock authorized, 27,044,527 shares were issued and outstanding as of June 30, 2019. Common stock reserved for future issuance upon the exercise, issuance or conversion of the respective equity instruments at June 30, 2019 are as follows:



Issued and Outstanding:
Stock options	2,512,033
Shares Reserved For:
2017 Equity Incentive Plan	2,615,613
2017 Employee Stock Purchase Plan	725,132
Total	5,852,778

Equity Incentive Plans

6 Months Ended

Jun. 30, 2019

Share-based Payment Arrangement [Abstract]

Equity Incentive Plans

2017 Equity Incentive Plan

On January 12, 2017, our board of directors and stockholders approved and adopted the 2017 Equity Incentive Plan, or the 2017 Plan. The 2017 Plan became effective upon the execution and delivery of the underwriting agreement for our initial public offering on January 26, 2017, and replaced our existing 2006 Equity Incentive Plan, or the 2006 Plan. Under the 2017 Plan, we may grant stock options, stock appreciation rights, restricted stock, restricted stock units and other awards to individuals who are then our employees, officers, directors or consultants. In addition, the number of shares of stock available for issuance under the 2017 Plan will be automatically increased each January 1, beginning on January 1, 2018, by 4% of the aggregate number of outstanding shares of our common stock as of the immediately preceding December 31 or such lesser number as determined by our board of directors. The 2017 Plan automatically increased by 1,076,877 shares as of January 1, 2019.

Employee Stock Purchase Plan

On January 12, 2017, our board of directors and stockholders approved and adopted the 2017 Employee Stock Purchase Plan or the ESPP. The ESPP became effective upon the execution and delivery of the underwriting agreement for our initial public offering on January 26, 2017. In addition, the number shares of stock available for issuance under the ESPP will be automatically increased each January 1, beginning on January 1, 2018, by 1% of the aggregate number of outstanding shares of our common stock as of the immediately preceding December 31 or such lesser number as determined by our board of directors. The ESPP automatically increased by 269,219 shares as of January 1, 2019.

Stock Options

Stock options granted to employees generally vest over a four-year period while stock options granted to directors vest over a one year period. Each have a maximum term of ten years from the date of grant, subject to earlier cancellation prior to vesting upon cessation of service to us. A summary of the activity related to stock option awards during the six months ended June 30, 2019 is as follows:



	Shares Subject to Options		Weighted-Average Exercise Price per Share		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2019	2,152,455		$	27.55
Granted	539,400		$	69.02
Exercises	(122,705	)	$	6.43
Forfeitures and cancellations	(57,117	)	$	69.45
Outstanding at June 30, 2019	2,512,033		$	36.53	7.27	$	70,414
Exercisable at June 30, 2019	1,398,990		$	19.46	6.06	$	57,308

Stock-Based Compensation Expense

The estimated fair values of stock option awards granted to employees were determined on the date of grant using the Black-Scholes option valuation model with the following weighted average assumptions:



	Six Months Ended June 30,
	2019			2018
Risk-free interest rate	2.5		%	2.6		%
Expected volatility	68.5		%	68.5		%
Expected dividend yield	—		%	—		%
Expected term (in years)	6.25			6.25
Weighted average grant date fair value per share	$	44.02		$	67.05

We determine the appropriate risk free interest rate, expected term for employee stock-based awards, contractual term for non-employee stock-based awards, and volatility assumptions. The weighted-average expected option term for employee and non-employee stock based awards reflects the application of the simplified method, which defines the life as the average of the contractual term of the options and the weighted average vesting period for all option tranches. Estimated volatility incorporates historical volatility of our stock price as well as similar entities whose share prices are publicly available. The risk free interest rate is based upon U.S. Treasury securities with remaining terms similar to the expected or contractual term of the stock-based payment awards. The assumed dividend yield is based on our expectation of not paying dividends in the foreseeable future.

Total non-cash stock-based compensation expense for all stock awards that was recognized in the consolidated statements of operations and comprehensive loss is as follows:



	Three Months Ended June 30,				Six Months Ended June 30,
(in thousands)	2019		2018		2019		2018
Research and development	$	1,649	$	899	$	2,889	$	1,655
General and administrative	1,994		1,649		3,621		3,153
Total	$	3,643	$	2,548	$	6,510	$	4,808

At June 30, 2019, there was $37.7 million of unrecognized compensation cost related to unvested stock option awards, which is expected to be recognized over a remaining weighted average vesting period of 2.69 years.

Australia Research and Development Tax Incentive	6 Months Ended
Australia Research and Development Tax Incentive	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Australia Research and Development Tax Incentive	Australia Research and Development Tax Incentive Our Australian subsidiary, which conducts core research and development activities on our behalf, is eligible to receive a 43.5% refundable tax incentive for qualified research and development activities during fiscal 2019 and fiscal 2018. For the three and six months ended June 30, 2019, there were no eligible expenditures incurred in Australia, therefore no tax incentive receivable was recorded. For the three and six months ended June 30, 2018, we recorded a less than $0.1 million reduction to research and development expenses in the consolidated statements of operations and comprehensive loss for eligible expenses. We received $0.2 million and $1.5 million in cash during the six months ended June 30, 2019 and 2018, respectively, related to the tax incentive. As of June 30, 2019, we had no remaining tax incentive receivable from the Australian government.

Commitments and Contingencies

6 Months Ended

Jun. 30, 2019

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Operating Leases

We have two non-cancellable office leases with remaining lease terms of approximately 2.25 years, each of which are classified as operating leases. Only one of our leases has remaining renewal options, which includes three options to renew for one additional year. The exercise of lease renewal options is at our sole discretion, which we currently do not anticipate exercising and as such were not recognized as part of our ROU asset and lease liabilities. Our lease payments are fixed, and we recognize lease expense for these leases on a straight-line basis over the lease term. Operating lease ROU assets and lease liabilities are recorded based on the present value of the future minimum lease payments over the lease term at commencement date. As our leases do not provide an implicit rate, we used our incremental borrowing rate based on the information available at effective date of adoption in determining the present value of future payments. The weighted-average discount rate used was 8.59%.

Our balance sheet includes our ROU assets and lease liabilities as follows (in thousands):



Leases	Classification on the Balance Sheet	June 30, 2019
Operating ROU assets	Other long-term assets	$	1,764
Operating lease liabilities	Other current liabilities	819
Operating lease liabilities	Other long-term liabilities	1,105

The following costs are included in our cash flow statement (in thousands):

At June 30, 2019, the future minimum annual obligations under non-cancellable operating lease commitments in excess of one year are as follows (in thousands):



Years Ending December 31,
2019	$	474
2020	968
2021	677
2022	—
2023	—
Thereafter	—
Total minimum payments required	2,119
Less imputed interest	(195		)
Total	$	1,924

As previously disclosed in our 2018 Annual Report on Form 10-K, and under the previous lease accounting standard, future minimum annual obligations under non-cancellable operating lease commitments in excess of one year would have been as follows:



Years Ending December 31,
2019	$	937
2020	969
2021	726
2022	—
2023	—
Thereafter	—
Total minimum payments required	$	2,632

Summary of Significant Accounting Policies (Policies)	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Jun. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission, or the SEC. Certain information and note disclosures normally included in annual financial statements prepared in accordance with U.S. generally accepted accounting principles, or U.S. GAAP, have been omitted. The accompanying unaudited consolidated financial statements include all known adjustments necessary for a fair presentation of the results of interim periods as required by U.S. GAAP. These adjustments consist primarily of normal recurring accruals and estimates that impact the carrying value of assets and liabilities. Also, certain reclassifications have been made to 2018 financial information to conform to the current year presentation of long-term liabilities on the Consolidated Balance Sheets. Operating results for the six months ended June 30, 2019 are not necessarily indicative of the results that may be expected for the year ending December 31, 2019. The financial statements should be read in conjunction with our audited financial statements for the year ended December 31, 2018, included in our Annual Form 10-K.
Basis of Consolidation	Basis of Consolidation The accompanying consolidated financial statements include us and our wholly-owned Australian subsidiary. All intercompany accounts and transactions have been eliminated in consolidation. We operate in one reportable segment and our functional and reporting currency is the U.S. dollar.
Use of Estimates	Use of Estimates The preparation of the accompanying consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates. We base our estimates and assumptions on historical experience when available and on various factors that we believe to be reasonable under the circumstances. We evaluate our estimates and assumptions on an ongoing basis. Our actual results could differ from these estimates under different assumptions or conditions.
Leases	Leases Prior to January 1, 2019, we recorded our leases in accordance with Accounting Standard Codification (ASC) Topic 840, Leases, and all current leases were classified as operating leases. Rent expense was recognized on a straight-line basis over the terms of the leases and, accordingly, we recorded the cumulative difference between cash rent payments and the recognition of rent expense as a deferred rent liability. When an operating lease included lease incentives, such as a rent abatements or leasehold improvement allowances, or required fixed escalations of the minimum lease payments, the aggregate rental expense, including such incentives or increases, was recognized on a straight-line basis over the term of the lease. Effective January 1, 2019, we adopted Accounting Standard Update (ASU) 2016-02, ASC 842, Leases, under which all outstanding leases continued to be classified as operating leases. Rent expense is recognized on a straight-line basis. When an operating lease includes rent abatements or requires fixed escalations of the minimum lease payments, the aggregate rental expense is recognized on a straight-line basis over the term of the lease. When an operating lease includes lease incentives such as leasehold improvement allowances, the lease incentive is included in the right-of-use, or “ROU”, asset. Operating lease ROU assets and operating lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at the date of adoption of ASC 842, or the lease commencement date. As our leases do not provide an implicit rate, we use our incremental borrowing rate based on the information available at commencement date in determining the present value of future payments. We account for fixed lease components separately from non-lease components.
Net Loss Per Common Share	Net Loss Per Common Share Basic net loss per common share is computed by dividing net loss by the weighted-average number of common shares outstanding during the period. Diluted net loss per share is computed by dividing net loss by the weighted-average number of common equivalent shares outstanding for the period, as well as any dilutive effect from outstanding stock options and warrants using the treasury stock method. For each period presented, there is no difference in the number of shares used to calculate basic and diluted net loss per share.
Accounting Pronouncements Recently Adopted	Accounting Pronouncements Recently Adopted In February 2016, the Financial Accounting Standards Board, or FASB, issued ASU 2016-02, Leases (Topic 842), which requires that lessees recognize a right-of-use, or “ROU”, asset and a related lease liability on the balance sheet for all leases with a term longer than 12 months. Topic 842 was subsequently amended by ASU 2018-01, Land Easement Practical Expedient for Transition to Topic 842; ASU 2018-10, Codification Improvements to Topic 842, Leases; ASU 2018-11, Targeted Improvements; and ASU 2019-01, Leases (Topic 842): Codification Improvements. ASU 2016-02 became effective for our annual reporting period beginning January 1, 2019, including interim periods thereafter. A modified retrospective transition approach is required, applying the new standard to all leases existing at the date of initial application. An entity may choose to use either (i) its effective date or (ii) the beginning of the earliest comparative period presented in the financial statements as its date of initial application. We adopted this standard on January 1, 2019 and used the effective date as our date of initial application. Upon adoption, we elected the package of transition practical expedients, which allowed us to carry forward prior conclusions related to whether any expired or existing contracts are or contain leases, the lease classification for any expired or existing leases and initial direct costs for existing leases. We also made an accounting policy election to not recognize leases with an initial term of 12 months or less within our consolidated balance sheets and to recognize those lease payments on a straight-line basis in our consolidated statements of operations over the lease term. Adoption of the new standard resulted in the recording of operating lease ROU assets and lease liabilities of approximately $2.1 million and $2.3 million as of January 1, 2019, respectively related to our real estate leases. Adoption of this new standard did not have a material impact on our consolidated statements of operations or cash flows.

Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2019

Accounting Policies [Abstract]

Schedule of Outstanding Potentially Dilutive Securities Excluded in the Calculation of Diluted Net Loss Per Share



	Three Months Ended June 30,		Six Months Ended June 30,
(in thousands)	2019	2018	2019	2018
Options to purchase common stock	2,525	2,542	2,443	2,572
Warrants to purchase common stock	—	—	—	4
Total	2,525	2,542	2,443	2,576

Balance Sheet Accounts and Supplemental Disclosures (Tables)

6 Months Ended

Jun. 30, 2019

Balance Sheet Related Disclosures [Abstract]

Property and Equipment

Property and equipment consist of the following:



(in thousands)	June 30, 2019			December 31, 2018
Laboratory equipment	$	4,528		$	4,287
Office furniture and equipment	807			780
Leasehold improvements	575			575
Property and equipment, gross	5,910			5,642
Less: accumulated depreciation and amortization	(4,429		)	(4,197		)
Total property and equipment, net	$	1,481		$	1,445

Schedule of Accrued Expenses

Accrued expenses consist of the following:



(in thousands)	June 30, 2019		December 31, 2018
Accrued compensation and related expenses	$	1,909	$	2,421
Accrued professional fees	496		442
Accrued research, development and manufacturing expenses	11,360		5,577
Other	337		321
Total accrued expenses	$	14,102	$	8,761

Collaborative Research and Development Agreements (Tables)

6 Months Ended

Jun. 30, 2019

Revenue Recognition [Abstract]

Schedule of Collaborative Arrangements and Non-collaborative Arrangement Transactions

Milestones recognized through June 30, 2019 under the TESARO Agreement are as follows:



	Anti-PD-1 (TSR042/Dostarlimab)		Anti-TIM-3 (TSR022)		Anti-LAG-3 (TSR033)
Milestone Event	Amount	Quarter Recognized	Amount	Quarter Recognized	Amount	Quarter Recognized
Initiated in vivo toxicology studies using good laboratory practices (GLPs)	$1.0M	Q2'15	$1.0M	Q4'15	$1.0M	Q3'16
IND clearance from the FDA	$4.0M	Q1'16	$4.0M	Q2'16	$4.0M	Q2'17
Phase 2 clinical trial initiation	$3.0M	Q2'17	$3.0M	Q4'17	—	—
Phase 3 clinical trial initiation - first indication	$5.0M	Q3'18	—	—	—	—
Phase 3 clinical trial initiation - second indication	$5.0M	Q2'19	—	—	—	—

Milestones achieved through June 30, 2019 under the Celgene Agreement are as follows:



	Anti-PD-1 (CC-90006)
Milestone Event	Amount	Quarter Recognized
Completion of first in vivo toxicology studies using GLPs	$0.5M	Q2'16
Phase 1 clinical trial initiation	$1.0M	Q4'16

Fair Value Measurements and Available for Sale Investments (Tables)

6 Months Ended

Jun. 30, 2019

Fair Value Disclosures [Abstract]

Schedule of Assets and Liabilities that Require Fair Value Measurements on a Recurring Basis

The following table summarizes our assets and liabilities that require fair value measurements on a recurring basis and their respective input levels based on the fair value hierarchy:



	Fair Value Measurements at End of Period Using:
(in thousands)	Fair Value		Quoted Market Prices for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
At June 30, 2019
Money market funds⁽¹⁾	$	127,844	$	127,844	$	—	$	—
Mutual funds⁽¹⁾	8,170		8,170		—		—
U.S. Treasury securities⁽²⁾	112,676		112,676		—		—
Certificates of deposit⁽²⁾	6,155		—		6,155		—
Agency securities⁽²⁾	61,684		—		61,684		—
Commercial and corporate obligations⁽¹⁾⁽²⁾	145,907		—		145,907		—
At December 31, 2018
Money market funds⁽¹⁾	$	87,213	$	87,213	$	—	$	—
Mutual funds⁽¹⁾	7,967		7,967		—		—
U.S. Treasury securities⁽²⁾	164,245		164,245		—		—
Certificates of deposit⁽²⁾	4,784		—		4,784		—
Agency securities⁽¹⁾⁽²⁾	81,296		—		81,296		—
Commercial and corporate obligations⁽¹⁾⁽²⁾	153,983		—		153,983		—


⁽¹⁾	Included in cash and cash equivalents, and restricted cash in the accompanying consolidated balance sheets.

⁽²⁾

Included in short-term or long-term investments in the accompanying consolidated balance sheets depending on the respective maturity date.

Fair Value of Other Financial Instruments

The fair value of our other financial instruments estimated as of June 30, 2019 and December 31, 2018 are presented below:



	June 30, 2019				December 31, 2018
	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Notes payable	$	4,781	$	5,084	$	8,199	$	8,806

Available-for-sale Investments

The aggregate market value, cost basis, and gross unrealized gains and losses of available-for-sale investments by security type, classified in cash equivalents, short-term and long-term investments as of June 30, 2019 are as follows:



(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Total Fair Value
Agency securities⁽¹⁾	$	61,558	$	133	$	(7	)	$	61,684
Certificates of deposit⁽²⁾	6,111		44		—			6,155
Commercial and corporate obligations⁽³⁾	145,548		366		(7		)	145,907
U.S. Treasury securities⁽⁴⁾	112,363		319		(6		)	112,676
Total available-for-sale investments	$	325,580	$	862	$	(20	)	$	326,422


⁽¹⁾	Of our outstanding agency securities, $47.8 million have maturity dates of less than one year and $13.9 million have a maturity date of between one to two years as of June 30, 2019.


⁽²⁾	Of our outstanding certificates of deposit, $1.0 million have a maturity date of less than one year and $5.2 million have a maturity date of between one to two years as of June 30, 2019.


⁽³⁾	Of our outstanding commercial and corporate obligations, $131.9 million have maturity dates of less than one year and $14.0 million have a maturity date of between one to two years as of June 30, 2019.

⁽⁴⁾

Of our outstanding U.S. Treasury securities $100.1 million have maturity dates of less than one year and $12.6 million have a maturity date of between one to two years as of June 30, 2019.

Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2019

Equity [Abstract]

Schedule of Common Stock Reserved for Future Issuance

Common stock reserved for future issuance upon the exercise, issuance or conversion of the respective equity instruments at June 30, 2019 are as follows:



Issued and Outstanding:
Stock options	2,512,033
Shares Reserved For:
2017 Equity Incentive Plan	2,615,613
2017 Employee Stock Purchase Plan	725,132
Total	5,852,778

Equity Incentive Plans (Tables)

6 Months Ended

Jun. 30, 2019

Share-based Payment Arrangement [Abstract]

Summary of Activity Related to Stock Option Awards

A summary of the activity related to stock option awards during the six months ended June 30, 2019 is as follows:



	Shares Subject to Options		Weighted-Average Exercise Price per Share		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2019	2,152,455		$	27.55
Granted	539,400		$	69.02
Exercises	(122,705	)	$	6.43
Forfeitures and cancellations	(57,117	)	$	69.45
Outstanding at June 30, 2019	2,512,033		$	36.53	7.27	$	70,414
Exercisable at June 30, 2019	1,398,990		$	19.46	6.06	$	57,308

Summary of Weighted Average Assumptions in Stock Option Valuations



	Six Months Ended June 30,
	2019			2018
Risk-free interest rate	2.5		%	2.6		%
Expected volatility	68.5		%	68.5		%
Expected dividend yield	—		%	—		%
Expected term (in years)	6.25			6.25
Weighted average grant date fair value per share	$	44.02		$	67.05

Summary of Non-cash Stock-based Compensation Expense

Total non-cash stock-based compensation expense for all stock awards that was recognized in the consolidated statements of operations and comprehensive loss is as follows:



	Three Months Ended June 30,				Six Months Ended June 30,
(in thousands)	2019		2018		2019		2018
Research and development	$	1,649	$	899	$	2,889	$	1,655
General and administrative	1,994		1,649		3,621		3,153
Total	$	3,643	$	2,548	$	6,510	$	4,808

Commitments and Contingencies (Tables)

6 Months Ended

Jun. 30, 2019

Commitments and Contingencies Disclosure [Abstract]

Classification on the Balance Sheet

Our balance sheet includes our ROU assets and lease liabilities as follows (in thousands):



Leases	Classification on the Balance Sheet	June 30, 2019
Operating ROU assets	Other long-term assets	$	1,764
Operating lease liabilities	Other current liabilities	819
Operating lease liabilities	Other long-term liabilities	1,105

Costs Included in Cash Flow Statement

The following costs are included in our cash flow statement (in thousands):

Schedule of Future Minimum Annual Obligations

At June 30, 2019, the future minimum annual obligations under non-cancellable operating lease commitments in excess of one year are as follows (in thousands):



Years Ending December 31,
2019	$	474
2020	968
2021	677
2022	—
2023	—
Thereafter	—
Total minimum payments required	2,119
Less imputed interest	(195		)
Total	$	1,924

Schedule of Future Minimum Annual Obligations Under Previous Lease Accounting Standard



Years Ending December 31,
2019	$	937
2020	969
2021	726
2022	—
2023	—
Thereafter	—
Total minimum payments required	$	2,632

Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($) segment	Jan. 01, 2019 USD ($)
Accounting Policies [Abstract]
Number of reportable segments \| segment	1
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
ROU assets	$ 1,764
Lease liabilities	$ 1,924
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
ROU assets		$ 2,100
Lease liabilities		$ 2,300

Summary of Significant Accounting Policies - Summary of Potentially Dilutive Securities (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities excluded from computation of net loss per share (in shares)	2,525	2,542	2,443	2,576
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities excluded from computation of net loss per share (in shares)	2,525	2,542	2,443	2,572
Warrants to purchase common stock \| Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities excluded from computation of net loss per share (in shares)	0	0	0	4

Balance Sheet Accounts and Supplemental Disclosures - Property and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 5,910	$ 5,642
Less: accumulated depreciation and amortization	(4,429)	(4,197)
Total property and equipment, net	1,481	1,445
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	4,528	4,287
Office furniture and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	807	780
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 575	$ 575

Balance Sheet Accounts and Supplemental Disclosures - Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Accrued compensation and related expenses	$ 1,909	$ 2,421
Accrued professional fees	496	442
Accrued research, development and manufacturing expenses	11,360	5,577
Other	337	321
Total accrued expenses	$ 14,102	$ 8,761

Collaborative Research and Development Agreements (Details)	1 Months Ended		3 Months Ended											6 Months Ended		12 Months Ended
	Nov. 30, 2014 USD ($) target	Mar. 31, 2014 USD ($) target	Jun. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2011 USD ($)
TESARO \| Collaborative Research And Development Agreement
Deferred Revenue Arrangement [Line Items]
Upfront license fee received	$ 2,000,000.0	$ 17,000,000.0
Number of outstanding research and development targets \| target	4	3
Milestone payments, contingent upon preclinical and clinical trial events (up to)	$ 18,000,000.0
Milestone payments, contingent upon certain U.S. and European regulatory submissions and approvals (up to)	90,000,000.0
Milestone payments, contingent upon achievement of specified levels of worldwide sales (up to)	$ 165,000,000.0
Agreement term following first commercial sale or expiration of the last to expire patent (in years)	12 years
Collaboration revenue			$ 5,000,000.0		$ 0									$ 5,000,000	$ 0
TESARO \| Initiated in vivo toxicology studies using good laboratory practices (GLPs) \| AnaptysBio-generated Anti-PD-1 Antagonist Antibody (TSR-042)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount													$ 1,000,000.0
TESARO \| Initiated in vivo toxicology studies using good laboratory practices (GLPs) \| AnaptysBio Generated Anti-TIM3 Antagonist Antibody (TSR-022)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount												$ 1,000,000.0
TESARO \| Initiated in vivo toxicology studies using good laboratory practices (GLPs) \| AnaptysBio Generated Anti-LAG3 Antagonist Antibody (TSR-033)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount									$ 1,000,000.0
TESARO \| IND clearance from the FDA \| AnaptysBio-generated Anti-PD-1 Antagonist Antibody (TSR-042)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount											$ 4,000,000.0
TESARO \| IND clearance from the FDA \| AnaptysBio Generated Anti-TIM3 Antagonist Antibody (TSR-022)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount										$ 4,000,000.0
TESARO \| IND clearance from the FDA \| AnaptysBio Generated Anti-LAG3 Antagonist Antibody (TSR-033)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount							$ 4,000,000.0
TESARO \| Phase 2 clinical trial initiation \| AnaptysBio-generated Anti-PD-1 Antagonist Antibody (TSR-042)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount							$ 3,000,000.0
TESARO \| Phase 2 clinical trial initiation \| AnaptysBio Generated Anti-TIM3 Antagonist Antibody (TSR-022)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount						$ 3,000,000.0
TESARO \| Phase 3 clinical trial initiation - first indication \| AnaptysBio-generated Anti-PD-1 Antagonist Antibody (TSR-042)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount			5,000,000.0	$ 5,000,000.0
Celgene Corporation \| Collaborative Research And Development Agreement
Deferred Revenue Arrangement [Line Items]
Upfront license fee received																$ 6,000,000.0
Collaboration revenue			$ 0		$ 0									$ 0	$ 0
Maximum milestone payments per target																$ 53,000,000.0
Celgene Corporation \| Initiated in vivo toxicology studies using good laboratory practices (GLPs) \| AnaptysBio-Generated Anti-PD-1 Antagonist Antibody (CC-90006)
Deferred Revenue Arrangement [Line Items]
Milestone payment earned										$ 500,000
Celgene Corporation \| Phase 1 clinical trial initiation \| AnaptysBio-Generated Anti-PD-1 Antagonist Antibody (CC-90006)
Deferred Revenue Arrangement [Line Items]
Milestone payment earned								$ 1,000,000.0

Notes Payable (Details) - Notes Payable to Banks		1 Months Ended
Notes Payable (Details) - Notes Payable to Banks	Dec. 24, 2014 USD ($) installment	Jan. 31, 2016 USD ($)	Jun. 30, 2019 USD ($) payment
Debt Instrument [Line Items]
Aggregate borrowing capacity	$ 5,000,000.0
Loan and Security Agreement (LSA)
Debt Instrument [Line Items]
Debt instrument, maximum borrowing capacity	$ 15,000,000.0
Number of loan installments (in installments) \| installment	3
Final payment fee		$ 800,000
Notes payable			$ 4,800,000
Debt instrument discounts			$ 400,000
Effective interest rate			13.27%
Long-term Debt, Fiscal Year Maturity [Abstract]
Debt maturities in remainder of year			$ 3,800,000
2020			$ 600,000
Term Loans
Debt Instrument [Line Items]
Fixed interest rate (as a percent)		7.30%
Number of principal and interest payments (in payments) \| payment			7
Interest rate at period end (as a percent)			8.87%
Term Loans \| 3-Month LIBOR interest rate
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)		6.37%
Term A Loans
Debt Instrument [Line Items]
Aggregate draw on term loan	$ 5,000,000.0
Fixed interest rate (as a percent)	6.97%
Term B and Term C Loans
Debt Instrument [Line Items]
Aggregate borrowing capacity		$ 10,000,000.0

Fair Value Measurements and Available for Sale Investments - Fair Value of Other Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable	$ 4,781	$ 8,199
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable	$ 5,084	$ 8,806

Fair Value Measurements and Available for Sale Investments - Available-for-sale Investments (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 325,580
Gross Unrealized Gains	862
Gross Unrealized Losses	(20)
Total Fair Value	326,422
Short-term investments	275,664	$ 313,486
Long-term investments	45,707	$ 73,128
Agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	61,558
Gross Unrealized Gains	133
Gross Unrealized Losses	(7)
Total Fair Value	61,684
Short-term investments	47,800
Long-term investments	$ 13,900
Agency securities \| Minimum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	1 year
Agency securities \| Maximum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	2 years
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 6,111
Gross Unrealized Gains	44
Gross Unrealized Losses	0
Total Fair Value	6,155
Short-term investments	1,000
Long-term investments	$ 5,200
Certificates of deposit \| Minimum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	1 year
Certificates of deposit \| Maximum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	2 years
Commercial and corporate obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 145,548
Gross Unrealized Gains	366
Gross Unrealized Losses	(7)
Total Fair Value	145,907
Short-term investments	131,900
Long-term investments	$ 14,000
Commercial and corporate obligations \| Minimum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	1 year
Commercial and corporate obligations \| Maximum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	2 years
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 112,363
Gross Unrealized Gains	319
Gross Unrealized Losses	(6)
Total Fair Value	112,676
Short-term investments	100,100
Long-term investments	$ 12,600
U.S. Treasury securities \| Minimum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	1 year
U.S. Treasury securities \| Maximum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	2 years

Stockholders' Equity - Additional Information (Details) - shares	Jun. 30, 2019	Dec. 31, 2018
Equity [Abstract]
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	27,044,527	26,922,000

Stockholders' Equity - Summary of Common Stock Reserved for Future Issuance (Details) - shares	Jun. 30, 2019	Dec. 31, 2018
Issued and Outstanding:
Stock options issued and outstanding (in shares)	2,512,033	2,152,455
Common stock, shares reserved for issuance (in shares)	5,852,778
2017 Equity Incentive Plan
Issued and Outstanding:
Shares reserved for future award grants (in shares)	2,615,613
2017 Employee Stock Purchase Plan
Issued and Outstanding:
Shares reserved for future award grants (in shares)	725,132

Equity Incentive Plans - Narrative (Details) - USD ($) $ in Millions				6 Months Ended
	Jan. 01, 2019	Jan. 01, 2018	Jan. 26, 2017	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost				$ 37.7
Options to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)				4 years
Award expiration period (in years)				10 years
Options to purchase common stock \| Director Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)				1 year
Award expiration period (in years)				10 years
Employee and nonemployee stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period remaining for amortization of unrecognized compensation cost (in years)				2 years 8 months 8 days
2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual increase in number of shares available for issuance			4.00%
Capital shares reserved for future issuance, increase (in shares)	1,076,877
2017 Employee Stock Purchase Plan \| Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual increase in number of shares available for issuance		1.00%
Capital shares reserved for future issuance, increase (in shares)	269,219

Equity Incentive Plans - Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2019
Shares Subject to Options
Stock options outstanding, beginning balance (in shares)	2,152,455
Granted (in shares)	539,400
Exercises (in shares)	(122,705)
Forfeitures and cancellations (in shares)	(57,117)
Stock options outstanding, ending balance (in shares)	2,512,033
Stock options exercisable, ending balance (in shares)	1,398,990
Weighted-Average Exercise Price per Share
Stock options outstanding, beginning balance (in dollars per share)	$ 27.55
Granted (in dollars per share)	69.02
Exercises (in dollars per share)	6.43
Forfeitures and cancellations (in dollars per share)	69.45
Stock options outstanding, ending balance (in dollars per share)	36.53
Stock options exercisable, ending balance (in dollars per share)	$ 19.46
Weighted-Average Remaining Contractual Term and Aggregate Intrinsic Value
Weighted average remaining contractual term, options outstanding (in years)	7 years 3 months 7 days
Weighted average remaining contractual term, options exercisable (in years)	6 years 21 days
Aggregate intrinsic value, options outstanding	$ 70,414
Aggregate intrinsic value, options exercisable	$ 57,308

Equity Incentive Plans - Option Fair Value Assumptions (Details) - Options to purchase common stock - $ / shares	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	2.50%	2.60%
Expected volatility	68.50%	68.50%
Expected dividend yield	0.00%	0.00%
Expected term (in years)	6 years 3 months	6 years 3 months
Weighted average grant date fair value per share (in dollars per share)	$ 44.02	$ 67.05

Equity Incentive Plans - Allocation of Share-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 3,643	$ 2,548	$ 6,510	$ 4,808
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	1,649	899	2,889	1,655
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 1,994	$ 1,649	$ 3,621	$ 3,153

Australia Research and Development Tax Incentive (Details) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Tax Credit Carryforward [Line Items]
Australian tax incentive receivable		$ 0		$ 174,000
Australian Taxation Office
Tax Credit Carryforward [Line Items]
Research and development tax incentive credit received during the period		200,000	$ 1,500,000
Australian tax incentive receivable		$ 0
Australian Taxation Office \| Subsidiaries
Tax Credit Carryforward [Line Items]
Refundable tax incentive for qualified research and development activities (as a percent)		43.50%	43.50%
Research and development	$ 100,000	$ 0	$ 100,000

Commitments and Contingencies - Additional Information (Details)	6 Months Ended
	Jun. 30, 2019 lease renewal_option
Operating Leased Assets [Line Items]
Non-cancellable office leases \| lease	2
Operating lease, term of contract	2 years 3 months
Weighted-average discount rate	8.59%
One office lease
Operating Leased Assets [Line Items]
Number of one year renewal options \| renewal_option	3

Commitments and Contingencies - Classification on the Balance Sheet (Details) $ in Thousands	Jun. 30, 2019 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Operating ROU assets, Other long-term assets	$ 1,764
Operating lease liabilities, Other current liabilities	819
Operating lease liabilities, Other long-term liabilities	$ 1,105

Commitments and Contingencies - Costs Included in Cash Flow Statement (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Operating lease cost	$ 440
Cash paid for amounts included in the measurement of lease liabilities	$ 463

Commitments and Contingencies - Schedule of Future Minimum Annual Obligations (Details) $ in Thousands	Jun. 30, 2019 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2019	$ 474
2020	968
2021	677
2022	0
2023	0
Thereafter	0
Total minimum payments required	2,119
Less imputed interest	(195)
Total	$ 1,924

Commitments and Contingencies - Schedule of Future Minimum Annual Obligations Under Previous Lease Accounting Standard (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2019	$ 937
2020	969
2021	726
2022	0
2023	0
Thereafter	0
Total minimum payments required	$ 2,632

Fair Value Measurements and Available for Sale Investments - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	$ 326,422
U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	112,676
Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	6,155
Agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	61,684
Commercial and corporate obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	145,907
Fair Value, Measurements, Recurring \| U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	112,676	$ 164,245
Fair Value, Measurements, Recurring \| Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	6,155	4,784
Fair Value, Measurements, Recurring \| Agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	61,684	81,296
Fair Value, Measurements, Recurring \| Commercial and corporate obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	145,907	153,983
Fair Value, Measurements, Recurring \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	127,844	87,213
Fair Value, Measurements, Recurring \| Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	8,170	7,967
Fair Value, Measurements, Recurring \| Quoted Market Prices for Identical Assets (Level 1) \| U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	112,676	164,245
Fair Value, Measurements, Recurring \| Quoted Market Prices for Identical Assets (Level 1) \| Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	0	0
Fair Value, Measurements, Recurring \| Quoted Market Prices for Identical Assets (Level 1) \| Agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	0	0
Fair Value, Measurements, Recurring \| Quoted Market Prices for Identical Assets (Level 1) \| Commercial and corporate obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	0	0
Fair Value, Measurements, Recurring \| Quoted Market Prices for Identical Assets (Level 1) \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	127,844	87,213
Fair Value, Measurements, Recurring \| Quoted Market Prices for Identical Assets (Level 1) \| Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	8,170	7,967
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	0	0
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	6,155	4,784
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	61,684	81,296
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Commercial and corporate obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	145,907	153,983
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0	0
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Commercial and corporate obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	$ 0	$ 0