Aimmune Therapeutics (AIMT) 10-Q 8 Aug 19 2019 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Jul. 31, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Trading Symbol	AIMT
Entity Registrant Name	AIMMUNE THERAPEUTICS, INC.
Entity Central Index Key	0001631650
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		62,668,957
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-37519
Entity Tax Identification Number	452748244
Entity Address, Address Line One	8000 Marina Blvd.
Entity Address, Address Line Two	Suite 300
Entity Address, City or Town	Brisbane
Entity Address, State or Province	California
Entity Address, Postal Zip Code	94005
City Area Code	650
Local Phone Number	614-5220

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 72,564	$ 107,511
Short-term investments	171,108	196,421
Prepaid expenses and other current assets	6,859	8,687
Total current assets	250,531	312,619
Long-term investments	6,584
Property and equipment, net	29,414	26,328
Operating lease right-of-use assets	11,736
Prepaid expenses and other assets	511	608
Total assets	298,776	339,555
Current liabilities:
Accounts payable	14,086	8,833
Accrued liabilities	27,083	29,144
Operating lease liabilities, current	2,022
Other current liabilities	20	35
Total current liabilities	43,211	38,012
Long term debt, net of discount	38,526
Operating lease liabilities, non-current	11,036
Other liabilities	1,029	2,596
Total liabilities	93,802	40,608
Stockholders’ equity:
Preferred stock, par value $0.0001 per share— 10,000 shares authorized at June 30, 2019 and December 31, 2018; 0 shares issued and outstanding at June 30, 2019 and December 31, 2018
Common stock, par value $0.0001 per share—290,000 shares authorized as of June 30, 2019, and December 31, 2018; 62,660 and 62,142 shares issued and outstanding as of June 30, 2019, and December 31, 2018, respectively	6	6
Additional paid-in capital	798,058	775,283
Accumulated other comprehensive gain(loss)	236	(108)
Accumulated deficit	(593,326)	(476,234)
Total stockholders’ equity	204,974	298,947
Total liabilities and stockholders’ equity	$ 298,776	$ 339,555

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	290,000,000	290,000,000
Common stock, shares issued	62,660,000	62,142,000
Common stock, shares outstanding	62,660,000	62,142,000

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating expenses
Research and development	$ 31,988	$ 35,254	$ 63,304	$ 68,700
General and administrative	31,200	18,559	54,912	35,232
Total operating expenses	63,188	53,813	118,216	103,932
Loss from operations	(63,188)	(53,813)	(118,216)	(103,932)
Interest income, net	358	1,294	1,149	1,930
Loss before provision for income taxes	(62,830)	(52,519)	(117,067)	(102,002)
Provision for income taxes	48	33	77	50
Net loss	(62,878)	(52,552)	(117,144)	(102,052)
Other comprehensive loss, net of tax:
Unrealized gains (losses) on investments	174	2	345	(15)
Comprehensive loss	$ (62,704)	$ (52,550)	$ (116,799)	$ (102,067)
Net loss per common share, basic and diluted	$ (1.01)	$ (0.91)	$ (1.88)	$ (1.83)
Weighted average shares used in computing net loss per common share, basic and diluted	62,332	57,903	62,178	55,752

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive (Loss)/Gain	Accumulated deficit
Beginning balance at Dec. 31, 2017	$ 177,805	$ 5	$ 443,390	$ (108)	$ (265,482)
Beginning balances (in shares) at Dec. 31, 2017		51,091
Issuance of common stock upon exercise of vested options	2,743		2,743
Issuance of common stock upon exercise of vested options (in shares)		308
Issuance of common stock upon securities agreement (in shares)		300
Issuance of common stock upon public offering	190,454	$ 1	190,453
Issuance common stock upon initial public offering (in shares)		6,325
Stock-based compensation expense	7,607		7,607
Other comprehensive gain (loss)	(17)			(17)
Net loss	(49,500)				(49,500)
Ending balances at Mar. 31, 2018	329,092	$ 6	644,193	(125)	(314,982)
Ending balances (in shares) at Mar. 31, 2018		58,024
Beginning balance at Dec. 31, 2017	177,805	$ 5	443,390	(108)	(265,482)
Beginning balances (in shares) at Dec. 31, 2017		51,091
Other comprehensive gain (loss)	(15)
Net loss	(102,052)
Ending balances at Jun. 30, 2018	287,838	$ 6	655,490	(123)	(367,535)
Ending balances (in shares) at Jun. 30, 2018		58,461
Beginning balance at Mar. 31, 2018	329,092	$ 6	644,193	(125)	(314,982)
Beginning balances (in shares) at Mar. 31, 2018		58,024
Issuance of common stock upon exercise of vested options and vesting of restricted stock units	2,641		2,641
Issuance of common stock upon exercise of vested options and vesting of restricted stock units (in shares)		437
Issuance of common stock upon public offering	(19)		(18)		(1)
Stock-based compensation expense	8,674		8,674
Other comprehensive gain (loss)	2			2
Net loss	(52,552)				(52,552)
Ending balances at Jun. 30, 2018	287,838	$ 6	655,490	(123)	(367,535)
Ending balances (in shares) at Jun. 30, 2018		58,461
Beginning balance at Dec. 31, 2018	298,947	$ 6	775,283	(108)	(476,234)
Beginning balances (in shares) at Dec. 31, 2018		62,142
Issuance of common stock upon exercise of vested options	3,633		3,633
Issuance of common stock upon exercise of vested options (in shares)		328
Stock-based compensation expense	7,765		7,765
Other comprehensive gain (loss)	171			171
Accumulated depreciation upon adoption of ASU Topic 842	51				51
Net loss	(54,266)				(54,266)
Ending balances at Mar. 31, 2019	256,301	$ 6	786,681	63	(530,449)
Ending balances (in shares) at Mar. 31, 2019		62,470
Beginning balance at Dec. 31, 2018	298,947	$ 6	775,283	(108)	(476,234)
Beginning balances (in shares) at Dec. 31, 2018		62,142
Other comprehensive gain (loss)	345
Net loss	(117,144)
Ending balances at Jun. 30, 2019	204,974	$ 6	798,058	236	(593,326)
Ending balances (in shares) at Jun. 30, 2019		62,659
Beginning balance at Mar. 31, 2019	256,301	$ 6	786,681	63	(530,449)
Beginning balances (in shares) at Mar. 31, 2019		62,470
Issuance of common stock upon exercise of vested options and vesting of restricted stock units	2,637		2,637
Issuance of common stock upon exercise of vested options and vesting of restricted stock units (in shares)		189
Stock-based compensation expense	8,740		8,740
Other comprehensive gain (loss)	174			173	1
Net loss	(62,878)				(62,878)
Ending balances at Jun. 30, 2019	$ 204,974	$ 6	$ 798,058	$ 236	$ (593,326)
Ending balances (in shares) at Jun. 30, 2019		62,659

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net loss	$ (117,144)	$ (102,052)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation expense	1,751	738
Stock-based compensation expense	16,505	16,281
Non-cash interest expense	2,259
Amortization of premium on investment securities	(1,094)	(225)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	2,596	(191)
Accounts payable	5,466	2,559
Accrued liabilities	(2,887)	6,366
Other liabilities	553	207
Net cash used in operating activities	(91,995)	(76,317)
Cash flows from investing activities:
Purchase of property and equipment	(4,860)	(6,243)
Purchase of investments	(106,980)	(133,208)
Maturities of investments	127,146	88,618
Net cash provided by (used in) investing activities	15,306	(50,833)
Cash flows from financing activities:
Borrowings under debt agreement	40,000
Debt issuance costs	(3,856)
Proceeds from underwritten public offering, net of offering costs		190,435
Net cash proceeds from exercise of stock options, including early exercise	6,270	5,385
Tax withholdings related to net share settlements of restricted stock units	(672)
Net cash provided by financing activities	41,742	195,820
Net increase (decrease) in cash and cash equivalents	(34,947)	68,670
Cash and cash equivalents at the beginning of the period	107,511	73,487
Cash and cash equivalents at the end of the period	72,564	142,157
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment purchases included in accounts payable and accrued liabilities	1,916	$ 556
Debt issuance costs, discount and interest payable	$ 2,259

Formation and Business of the C

Formation and Business of the Company	6 Months Ended
	Jun. 30, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Formation and Business of the Company	1. Formation and Business of the Company Aimmune Therapeutics, Inc., is a clinical-stage biopharmaceutical company advancing a new therapeutic approach, including the development of proprietary product candidates, to reduce the frequency and severity of allergic reactions, including anaphylaxis, upon exposure to peanut and other food allergens TM Since inception, we have incurred net losses and negative cash flows from operations. During the quarter and six months ended June 30, 2019, we incurred a net loss of $62.9 million and $117.1 million, respectively, and we used $92.0 million of cash in operations. As of June 30, 2019, we had an accumulated deficit of $593.3 million, and we do not expect to experience positive cash flows in the near future. As of June 30, 2019, we had cash, cash equivalents and investments of $250.3 million. We believe that our existing capital resources will be sufficient to fund our planned operations for at least the next 12 months and through expected regulatory approval and potential commercial launch in the United States and Europe for AR101, our lead CODIT TM

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Preparation The accompanying condensed consolidated financial statements have been prepared in accordance with Generally Accepted Accounting Principles, or GAAP, in the United States and applicable rules and regulations of the Securities and Exchange Commission, or SEC, regarding interim financial reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP have been condensed or omitted, and accordingly the balance sheet as of December 31, 2018, has been derived from audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements. These condensed consolidated financial statements have been prepared on the same basis as our annual financial statements and, in the opinion of management, reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair presentation of our financial information. The results of operations for the quarter and six months ended June 30, 2019, are not necessarily indicative of the results to be expected for the year ending December 31, 2019, or for any other interim period or for any other future year. We operate in one reportable segment. The accompanying condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2018, included in our Annual Report on Form 10-K filed with the SEC. Basis of Consolidation The accompanying condensed consolidated financial statements include the accounts of our wholly-owned subsidiaries. All significant intercompany transactions have been eliminated. Use of Estimates The preparation of the accompanying condensed consolidated financial statements in accordance with U.S. GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements, and the reported amounts of costs and expenses during the reporting period. 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. Significant Accounting Policies There have been no significant changes to the accounting policies during the six months ended June 30, 2019, as compared to the significant accounting policies described in Note 2 of the “Notes to Consolidated Financial Statements” in our audited consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2018, except as noted below. Recently Adopted Accounting Pronouncements We adopted Accounting Standards Update, or ASU No. 2016-02, Leases (Topic 842) Lease (Topic 841): Targeted Improvements Adoption of this standard has resulted in the recognition of operating lease right-of-use assets of $11.7 million and lease liabilities of $13.1 million as of June 30, 2019. The standard did not materially impact our consolidated statement of operations or our consolidated statements of cash flows. We adopted ASU No. 2018-07, Improvements to Nonemployee Share-Based Payment Accounting (Topic 718) Recently Issued Accounting Pronouncements Not Yet Adopted In August 2018, the Financial Accounting Standards Board, or the FASB, issued ASU 2018-13, Fair Value Measurement: Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement In June 2016, the FASB issued ASU 2016-13, Financial Instruments — Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments .

Available-for-Sale Securities a

Available-for-Sale Securities and Fair Value Measurements	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Available-for-Sale Securities and Fair Value Measurements	3. Available-for-Sale Securities and Fair Value Measurements We define fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an Our valuation techniques are based on observable and unobservable inputs. Observable inputs reflect readily obtainable data from independent sources, while unobservable inputs reflect our market assumptions. We classify these inputs into the following hierarchy: • Level 1—Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date; • 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 significant to the measurement of the fair value of the assets or liabilities that are supported by little or no market data. The following tables set forth our financial instrumen ts that were measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands): June 30, 2019 Level 1 Level 2 Level 3 Total Cash and cash equivalents: Cash and money market funds $ 72,564 $ — $ — $ 72,564 Total cash and cash equivalents $ 72,564 $ — $ — $ 72,564 Investments: Agency securities $ — $ 21,256 $ — $ 21,256 Corporate securities — 44,153 — 44,153 Commercial paper — 11,033 — 11,033 U.S. government securities — 101,250 — 101,250 Total investments $ — $ 177,692 $ — $ 177,692 December 31, 2018 Level 1 Level 2 Level 3 Total Cash and cash equivalents: Cash and money market funds $ 107,511 $ — $ — $ 107,511 Total cash and cash equivalents $ 107,511 $ — $ — $ 107,511 Investments: Agency securities — 17,352 — 17,352 Corporate securities — 54,474 — 54,474 Commercial paper — 5,965 — 5,965 U.S. government securities — 118,630 — 118,630 Total investments $ — $ 196,421 $ — $ 196,421 Our valuation techniques used to measure the fair value of money market funds were derived from quoted prices in active markets for identical assets. The valuation techniques used to measure the fair value of investments, all of which have counterparties with high credit ratings, were valued based on quoted market prices or model-driven valuations using significant inputs derived from or corroborated by observable market data. Investments are carried at fair value. During the quarters and six months ended June 30, 2019 and 2018, there were no transfers between Level 1 and Level 2 of the fair value hierarchy. Available-for-sale 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 and investments, as of June 30, 2019 and December 31, 2018, are as follows June 30, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Total Fair Value Agency securities $ 21,243 $ 13 $ — $ 21,256 Corporate securities 44,051 102 — 44,153 Commercial paper 11,033 — — 11,033 U.S. government securities 101,129 121 — 101,250 Total available-for-sale investments $ 177,456 $ 236 $ — $ 177,692 December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Total Fair Value Agency securities $ 17,361 $ — $ (9 ) $ 17,352 Corporate securities 54,536 — (62 ) 54,474 Commercial paper 5,965 — — 5,965 U.S. government securities 118,667 14 (51 ) 118,630 Total available-for-sale investments $ 196,529 $ 14 $ (122 ) $ 196,421 At June 30, 2019, all of the available-for-sale securities have contractual maturities within eighteen months. We periodically review our available-for-sale investments for other-than-temporary impairment loss. We consider factors such as the duration, severity and the reason for the decline in value, the potential recovery period and our intent to sell. For debt securities, we also consider whether (i) it is more likely than not that we will be required to sell the debt securities before recovery of their amortized cost basis, and (ii) the amortized cost basis cannot be recovered as a result of credit losses. During the quarters and six months ended June 30, 2019 and 2018 The carrying value of our long-term debt approximates its fair value at each balance sheet date due to its variable interest rate, which approximates a market interest rate.

Balance Sheet Components

Balance Sheet Components	6 Months Ended
	Jun. 30, 2019
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	4. Balance Sheet Components Property and Equipment, Net Property and equipment, net consists of the following (in thousands): June 30, 2019 December 31, 2018 Furniture and equipment $ 2,642 $ 2,221 Computer equipment 2,603 2,073 Manufacturing equipment 6,473 1,733 Leased equipment 100 100 Leasehold improvements 14,506 4,469 Buildings — 688 Construction in progress 7,918 18,295 Property and equipment, gross 34,242 29,579 Less: accumulated depreciation (4,828 ) (3,251 ) Property and equipment, net $ 29,414 $ 26,328 Accrued Liabilities Accrued liabilities consisted of the following (in thousands): June 30, 2019 December 31, 2018 Compensation and benefits $ 7,054 $ 8,912 Research and development 8,721 15,504 Professional and consulting 10,829 4,691 Other 479 37 Total accrued liabilities $ 27,083 $ 29,144

Long-Term Debt, Net of Discount

Long-Term Debt, Net of Discounts	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Long-Term Debt, Net of Discounts	5. Long-term Debt, Net of Discounts In January 2019, we entered into a loan agreement with an affiliate of KKR for up to $170.0 million in three tranches, or the KKR Loans. Of the total loan amount, $40.0 million was funded upon closing of the transaction, with $85.0 million to be funded upon FDA approval of AR101, or the Regulatory Approval and satisfaction of other customary borrowing conditions, and $45.0 million to be made available at our option in 2020 upon the satisfaction of certain borrowing conditions. The KKR Loans have a maturity date being the earliest of (a) January 3, 2025, or if Regulatory Approval has not occurred on or before December 31, 2020, January 15, 2021 and (b) the date that is 91 days prior to the earliest current maturity date of any other loans we might have in excess of $ 15.0 million prior to the funding of the third tranche of the KKR Loans or $ 25.0 million following the funding of the third tranche of the KKR Loans. The KKR Loans bear interest through maturity, at our election with respect to (a) Alternate Base Rate , or ABR Loans, ABR plus 6.50 % per annum and (b) London Interbank Offered Rate , or LIBOR Loans, 30-day LIBOR plus 7.50 % per annum. We have the option to elect to make interest payments from available funds or make interest payments in kind by capitalizing such interest amounts on the applicable interest payment date by adding the amounts to the outstanding principal amount of the loan. Any capitalized amounts also bear interest. To date, w e have selected to pay in kind and capitalized the interest for the six months e nding June 30, 2019 . We will begin paying accrued interest on outstanding KKR Loans on the last business day of each March, June, September and December thereafter while any KKR Loans are outstanding, as well as on the final maturity date of the KKR Loans , with each such date being referred to herein as an Interest Payment Date. Principal payments on the KKR Loans are paid according to the following schedule: (i) on December 31, 2023, 50.0% of the outstanding principal amount of the loans as of such date, including any capitalized interest, (ii) on each Interest Payment Date thereafter, 12.5% of the outstanding principal amount of the KKR Loans as of December 31, 2023 and (iii) on January 3, 2025, or the Maturity Date, any remaining outstanding balance of the KKR Loans. We are also required to make mandatory prepayments of the KKR Loans under the Agreement, subject to specified exceptions, with the proceeds of asset sales, debt issuances, royalty transactions, collaboration transactions, and specified other events. In addition, upon the occurrence of a change of control, we must prepay, the outstanding amount of the KKR Loans. The KKR Loans can be prepaid at our discretion, at any time, subject to prepayment fees. If all or any of the KKR Loans are prepaid or required to be prepaid, then we must pay, in addition to such prepayment, a prepayment premium (the “Prepayment Premium”) equal to (i) with respect to any such prepayment paid on or prior to January 3, 2021, the amount, if any, by which (a) the present value as of such date of determination of (x) 105.00% of the principal amount of the KKR Loans prepaid plus (y) all required interest payments that would have been due on the principal amount of the KKR Loans prepaid through and including January 3, 2021, computed using a discount rate equal to the treasury rate most nearly equal to the period from such date of prepayment to January 3, 2021 plus 50 basis points exceeds (b) the principal amount of the KKR Loans prepaid, (ii) with respect to any prepayment paid or required to be paid after January 3, 2021 but on or prior to January 3, 2022, 5.00% of the principal amount of the KKR Loans prepaid, (iii) with respect to any prepayment paid or required to be paid after January 3, 2022 but on or prior to January 3, 2023, 2.00% of the principal amount of the KKR Loans prepaid and (iv) with respect to any prepayment paid or required to be prepaid thereafter, 0.00% of the principal amount of the KKR Loans prepaid. If we receive Regulatory Approval and do not draw the $85 million, then we would have to pay on the earlier of (i) the date on which commitments have been terminated and no KKR Loans are outstanding and (ii) the Interest Payment Date falling in the first full fiscal quarter after receipt of Regulatory Approval, a premium in an amount equal to $3.4 million and the Prepayment Premium for such date on a principal amount equal to $85.0 million. The premium with respect to the Regulatory Approval described in the immediately preceding sentence is not due if we draw the additional (after the first $40.00 million on the closing date) $85.0 million of the KKR Loans. In addition, upon the occurrence of a change of control, we must prepay, the outstanding amount of the KKR Loans. Upon the prepayment or repayment of all or any of the KKR Loans, we must pay an additional (in addition to the Prepayment Premium) exit fee in an amount equal to 4.00% of the principal amount of the KKR Loans prepaid or repaid. In connection with the KKR Loans, we paid direct fees of $3.9 million, including debt issuance costs. The fees are being amortized as interest expense over the term of the debt. As of June 30, 2019 and December 31, 2018, $41.9 million and $0, respectively, was outstanding under the KKR Loans. As of June 30, 2019, the interest rate on the KKR Loans was 9.94%. The following table represents our short-term and long-term debt obligations (in thousands): June 30, 2019 Principal amount of long-term debt $ 41,961 Less: Current portion of long-term debt - Long-term debt, net of current portion 41,961 Unamortized discount relating to deferred financing costs, net (3,559 ) Accrued exit fee payment 124 Long-term debt, net of discount and current portion $ 38,526 Future principal payments of our long-term debt as of June 30, 2019 are as follows: Fiscal year ending December 31: 2019 $ - 2020 - 2021 - 2022 - 2023 20,981 Thereafter 20,980 Total $ 41,961

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	6. Commitments and Contingencies Leases We lease facilities for office and manufacturing space under various operating leases and a security system under a financing lease. Operating lease right-of-use assets and liabilities on our condensed consolidated balance sheets represent the present value of our remaining lease payments over the remaining lease terms. We do not allocate lease payments to non-lease components. We use our incremental borrowing rate to calculate the present value of our lease payments, as the implicit rates in our leases are not readily determinable. As of June 30, 2019, the maturities of our operating lease liabilities were as follows (in thousands): Remaining Lease Payments June 30, 2019 Operating Financing Total 2019 $ 1,567 $ 17 $ 1,584 2020 3,330 34 3,364 2021 3,413 35 3,448 2022 3,497 9 3,506 2023 3,378 - 3,378 Thereafter 1,744 - 1,744 Total lease payments $ 16,929 $ 95 $ 17,024 Less: Effects of discounting (3,871 ) (29 ) (3,900 ) Present value of lease liabilities $ 13,058 $ 66 $ 13,124 Less: current portion (2,022 ) (19 ) (2,041 ) Long-term lease liabilities $ 11,036 $ 47 $ 11,083 Weighted-average remaining lease term 5 years 2.8 years Weighted-average incremental borrowing rate 11 % 23 % As of June 30, 2019, we have additional operating leases, primarily for our manufacturing facility, that have not yet commenced of $0.7 million. These operating leases will commence in the third quarter of 2019 with a lease term of 6.25 years. The component of our lease costs included in our condensed consolidated statements of income were as follows (in thousands): Quarter Ended Six Months Ended Lease Cost June 30, 2019 Operating lease cost $ 914 $ 1,879 Finance lease cost Amortization of leased assets 8 16 Interest on lease liabilities 4 8 Net lease cost $ 926 $ 1,903 Other information related to our operating lease was as follows (in thousands): Other Information Six Months Ended June 30, 2019 Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 1,879 Operating cash flows from finance leases $ 24 Total future aggregate minimum lease payments calculated under ASC 840 at December 31, 2018 were as follows (in thousands): Remaining Lease Payments December 31, 2018 Operating Financing Total 2019 $ 3,133 $ 33 $ 3,166 2020 3,330 34 3,364 2021 3,413 35 3,448 2022 3,497 9 3,506 2023 3,378 - 3,378 Thereafter 1,744 - 1,744 Total lease payments $ 18,495 $ 111 $ 18,606 Less: amount representing interest - (33 ) (33 ) Value of lease liabilities under ASC 840 $ 18,495 $ 78 $ 18,573 Less: current portion (3,133 ) (17 ) (3,150 ) Long-term lease liabilities $ 15,362 $ 61 $ 15,423 Purchase Commitments We purchase food-grade peanut flour from Golden Peanut Company, or GPC, pursuant to a long-term exclusive commercial supply agreement, which was expanded and extended in January 2018. GPC is precluded from selling several peanut flour products to any third party worldwide for use in oral immunotherapy, or OIT, for the treatment or cure of peanut allergy, provided that we are in compliance with our exclusive purchase obligation and meet specified annual purchase commitments. The restated agreement remains in effect until ten years five years In connection with the expansion and extension of the agreement, we issued Archer Daniels Midland Company 300,000 Pursuant with the restated agreement, our purchase obligation commences with the first delivery of peanut flour for commercial use, which we currently anticipate will occur in 2019, and the aggregate purchase commitment under this agreement would be $3.3 million over a term of ten years. In December 2018, we entered into an exclusive supply agreement for egg protein with Michael Foods, Inc. Pursuant to the agreement, we have exclusive access to the clinical and commercial use of Michael Foods’ egg products for any egg allergy treatment, prevention or cure for a period of up to 15 years beyond the potential approval of AR201. In May 2019, we entered into a Commercial Supply Agreement, or the Commercial Supply Agreement, pursuant to which CoreRx, Inc. agreed to manufacture commercial supply of AR101, if approved. Indemnifications We indemnify each of our officers and directors for certain events or occurrences, subject to certain limits, while the officer or director is or was serving at our request in such capacity, as permitted under Delaware law and in accordance with its certificate of incorporation and bylaws. The term of the indemnification period lasts as long as an officer or a director may be subject to any proceeding arising out of acts or omissions of such officer or director in such capacity. The maximum amount of potential future indemnification is unlimited; however, we currently hold director and officer liability insurance. This insurance allows the transfer of risk associated with our exposure and may enable us to recover a portion of any future amounts paid. We believe that the fair value of these indemnification obligations is minimal. Accordingly, we have not recognized any liabilities relating to these obligations for any period. Legal We are currently not a party to any material legal proceedings. During the normal course of business, we may be a party to legal claims that may not be covered by insurance. We do not believe that any such claims would have a material impact on our consolidated financial statements.

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	7. Stock-Based Compensation Equity Incentive Plan In July 2015, we adopted the 2015 Stock Plan, or the 2015 Plan. Under the 2015 Plan, 4,681,544 shares of our common stock were initially reserved for the issuance of stock options and restricted stock to employees, directors, and consultants under terms and provisions established by the Board of Directors, or the Board, and approved by our stockholders. As of June 30, 2019 and December 31, 2018, there were 4,625,878 and 4,364,963 shares available for future grant, respectively. Under the terms of the 2015 Plan, options may be granted at an exercise price not less than fair market value. For employees holding more than 10% of the voting rights of all classes of stock, the exercise prices for incentive stock options may not be less than 110% of fair market value, as determined by the Board. The terms of options granted under the 2015 Plan may not exceed ten years. All options issued to date have had a ten-year life. To date, options granted generally vest in three ways: 1) over four years at a rate of 25% upon the first anniversary of the issuance date and 1/48 th th th In August 2015, we adopted the 2015 ESPP, which commenced on January 1, 2018. Under the 2015 ESPP our employees may purchase common stock through payroll deductions at a price equal to 85% of the lower of the fair market value of the stock at the beginning of the offering period or at the end of each applicable purchase period. The 2015 ESPP generally provides for offering periods of six months in duration with purchase periods ending on either May 15 or November 15. Contributions under the 2015 ESPP are limited to a maximum of 15% of an employee’s eligible compensation. ESPP purchases are settled with common stock from the ESPP’s previously authorized and available pool of shares. We issued 41,030 shares at a weighted average price of $25.28 per share during the year ended December 31, 2018. As of June 30, 2019, we had issued 59,722 shares under the ESPP at a weighted average price of $17.75 per share and 2,346,064 shares under the ESPP remain available for purchase. Our 2013 Stock Plan, or the 2013 Plan, which was originally adopted during January 2013, was terminated upon consummation of our IPO in August 2015. As a terminated plan, no further options can be granted from the 2013 Plan, and no further shares are reserved for issuance under the 2013 Plan. Option activity under the 2015 Plan and 2013 Plan is set forth below: Options Outstanding Number Options Weighted- Average Exercise Price Weighted Average Remaining Contractual Life (in years) Aggregate Intrinsic Value (in thousands) Balance, December 31, 2018 7,133,113 $ 20.08 7.6 $ 27,413 Options granted 2,318,442 22.52 Options exercised and shares vested (366,221 ) 14.23 Options cancelled (515,002 ) 28.19 Balance, June 30, 2019 8,570,332 20.50 7.6 $ 28,934 Options vested and expected to vest as of June 30, 2019 8,017,038 20.22 7.5 $ 28,771 Options exercisable as of June 30, 2019 3,891,087 $ 15.93 6.3 $ 26,175 The aggregate intrinsic values of options outstanding, exercisable, and vested and expected to vest were calculated as the difference between the exercise price of the options and the market price for shares of our common stock as of June 30, 2019. The 2013 Plan provided for early exercise, therefore, all our outstanding stock options issued under that plan are exercisable. Restricted stock unit, or RSU, activity under the 2015 Plan is set forth below: Shares Weighted Average Grant Date Fair Value Unvested Balance, December 31, 2018 309,847 $ 33.37 Awarded 476,127 23.06 Released (91,354 ) 33.28 Forfeited (54,791 ) 29.72 Unvested Balance, June 30, 2019 639,829 $ 26.02 RSUs are measured based on the fair market value of the underlying stock on the date of grant and recognized as expense on a straight-line basis over the employee’s requisite service period (generally the vesting period). In connection with the expansion and extension of our long-term exclusive commercial supply agreement with GPC, we issued 300,000 shares of restricted common stock in January 2018. The restricted common stock vests in four tranches over a 3.5 year period and is measured based on the fair market value of the underlying stock as the shares vest. As of June 30, 2019, 75,000 shares had vested, and the remaining shares were restricted. As of June 30, 2019, total estimated unrecognized expense related to these restricted shares was $3.6 million based upon the fair market value of our common stock on December 31, 2018, which is expected to be recognized over the remaining vesting period of 2.03 years as general and administrative expense. Stock-based compensation expense recognized during the quarters and six months ended June 30, 2019 and 2018 related to these shares was as follows (in thousands): 2019 2018 Quarter ended June 30 $ 532 $ 830 Six months ended June 30 890 1,907 In February 2019, we issued 52,000 RSUs with a grant date fair value of approximately $1.3 million, to certain key employees that include service and performance vesting conditions related to the achievement of certain regulatory approvals for AR101. Stock-based compensation expense will be recognized when we conclude that it is probable that the performance conditions will be achieved. We will reassess the probability of vesting at each reporting period and adjust stock-based compensation expense based on this probability assessment. As the vesting is contingent upon specific performance conditions, stock-based compensation expense related to the grant will not be recognized until the specified conditions are determined to be probable of achievement. As none of the performance criteria were met during the six months ended June 30, 2019, we have not recognized any stock-based compensation related to these RSUs. Valuation Assumptions The weighted-average assumptions used to estimate the fair value of stock options using the Black-Scholes option valuation model and the resulting weighted average fair value of stock options granted were as follows : Quarter Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Expected term (in years) 6.0 6.0 6.0 6.0 Expected volatility 62.2 % 68.3 % 63.2 % 68.4 % Risk free interest rate 2.3 % 2.6 % 2.5 % 2.4 % Dividend yield — % — % — % — % Weighted average estimated fair value $ 11.93 $ 19.10 $ 13.38 $ 20.51 The weighted-average assumptions used to estimate the fair value of ESPP using the Black-Scholes option valuation model were as follows: Quarter Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Expected term (in years) 0.5 0.5 0.5 0.9 Expected volatility 50.7 % 47.0 % 50.7 % 50.4 % Risk free interest rate 2.4 % 2.1 % 2.4 % 1.8 % Dividend yield — % — % — % — % Weighted average estimated fair value $ 6.00 $ 8.41 $ 6.00 $ 12.42 Stock-Based Compensation Expense Stock-based compensation expense, net of estimated forfeitures, reflected in the condensed consolidated statements of comprehensive loss is as follows (in thousands): Quarter Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Research and development $ 2,957 $ 2,923 $ 5,700 $ 4,970 General and administrative 5,783 5,751 10,805 11,311 Total stock-based compensation expense $ 8,740 $ 8,674 $ 16,505 $ 16,281 During the quarter and six months ended June 30, 2019, we recorded approximately $0.5 million and $1.0 million, respectively, of stock-based compensation expense related to the acceleration of certain former executives’ stock options. Such expense was approximately $0.9 million and $2.1 million for the quarter and six months ended June 30, 2018, respectively. As of June 30, 2019, total unrecognized stock-based compensation expense and expected period over which such compensation will be recognized were as follows ($ in thousands): As of June 30, 2019 Stock-option Unrecognized stock compensation expense $ 60,246 Weighted-average remaining vesting period (years) 2.8 RSU Unrecognized stock compensation expense $ 11,753 Weighted-average remaining vesting period (years) 2.94 ESPP Unrecognized stock compensation expense $ 237 Weighted-average remaining vesting period (years) 0.38

Net Loss per Share

Net Loss per Share	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Net Loss per Share	8. Net Loss per Share Basic net loss per share is calculated based on the weighted-average number of common shares outstanding during the periods presented. For periods in which we have generated a net loss, basic and diluted net loss per share are the same due to the requirement to exclude potentially dilutive securities, consisting of common shares underlying outstanding stock options and restricted stock units, which would have an anti-dilutive effect on net loss per share. The following common stock equivalents were excluded from the computation of diluted net loss per share for the periods presented because their inclusion would have been antidilutive: Quarter Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Stock options 8,570,332 7,516,362 8,570,332 7,516,362 RSUs 639,829 360,574 639,829 360,574

Related Party Transaction

Related Party Transaction	6 Months Ended
	Jun. 30, 2019
Related Party Transactions [Abstract]
Related Party Transaction	9. Related Party Transaction In June 2017, Mark McDade, a member of our Board of Directors, joined the Board of Directors of MyHealthTeams, a private company that creates social networks for people living with chronic conditions by partnering with pharmaceutical and healthcare companies. We entered into an agreement with MyHealthTeams in 2015 under which they provide services to us. During the quarters and six months ended June 30, 2019 and 2018, there were payments of $0.1 million in each period to MyHealthTeams pursuant to such agreement At June 30, 2019 and December 31, 2018, t here were no accrued liabilities due under the MyHealthTeams agreement

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Basis of Preparation	Basis of Preparation The accompanying condensed consolidated financial statements have been prepared in accordance with Generally Accepted Accounting Principles, or GAAP, in the United States and applicable rules and regulations of the Securities and Exchange Commission, or SEC, regarding interim financial reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP have been condensed or omitted, and accordingly the balance sheet as of December 31, 2018, has been derived from audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements. These condensed consolidated financial statements have been prepared on the same basis as our annual financial statements and, in the opinion of management, reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair presentation of our financial information. The results of operations for the quarter and six months ended June 30, 2019, are not necessarily indicative of the results to be expected for the year ending December 31, 2019, or for any other interim period or for any other future year. We operate in one reportable segment. The accompanying condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2018, included in our Annual Report on Form 10-K filed with the SEC.
Basis of Consolidation	Basis of Consolidation The accompanying condensed consolidated financial statements include the accounts of our wholly-owned subsidiaries. All significant intercompany transactions have been eliminated.
Use of Estimates	Use of Estimates The preparation of the accompanying condensed consolidated financial statements in accordance with U.S. GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements, and the reported amounts of costs and expenses during the reporting period. 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.
Significant Accounting Policies	Significant Accounting Policies There have been no significant changes to the accounting policies during the six months ended June 30, 2019, as compared to the significant accounting policies described in Note 2 of the “Notes to Consolidated Financial Statements” in our audited consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2018, except as noted below.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements We adopted Accounting Standards Update, or ASU No. 2016-02, Leases (Topic 842) Lease (Topic 841): Targeted Improvements Adoption of this standard has resulted in the recognition of operating lease right-of-use assets of $11.7 million and lease liabilities of $13.1 million as of June 30, 2019. The standard did not materially impact our consolidated statement of operations or our consolidated statements of cash flows. We adopted ASU No. 2018-07, Improvements to Nonemployee Share-Based Payment Accounting (Topic 718)
Recently Issued Accounting Pronouncements Not Yet Adopted	Recently Issued Accounting Pronouncements Not Yet Adopted In August 2018, the Financial Accounting Standards Board, or the FASB, issued ASU 2018-13, Fair Value Measurement: Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement In June 2016, the FASB issued ASU 2016-13, Financial Instruments — Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments .
Fair Value Measurements	We define fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an Our valuation techniques are based on observable and unobservable inputs. Observable inputs reflect readily obtainable data from independent sources, while unobservable inputs reflect our market assumptions. We classify these inputs into the following hierarchy: • Level 1—Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date; • 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 significant to the measurement of the fair value of the assets or liabilities that are supported by little or no market data.

Available-for-Sale Securities_2

Available-for-Sale Securities and Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Summary of Financial Instruments Measured at Fair Value on a Recurring Basis	The following tables set forth our financial instrumen ts that were measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands): June 30, 2019 Level 1 Level 2 Level 3 Total Cash and cash equivalents: Cash and money market funds $ 72,564 $ — $ — $ 72,564 Total cash and cash equivalents $ 72,564 $ — $ — $ 72,564 Investments: Agency securities $ — $ 21,256 $ — $ 21,256 Corporate securities — 44,153 — 44,153 Commercial paper — 11,033 — 11,033 U.S. government securities — 101,250 — 101,250 Total investments $ — $ 177,692 $ — $ 177,692 December 31, 2018 Level 1 Level 2 Level 3 Total Cash and cash equivalents: Cash and money market funds $ 107,511 $ — $ — $ 107,511 Total cash and cash equivalents $ 107,511 $ — $ — $ 107,511 Investments: Agency securities — 17,352 — 17,352 Corporate securities — 54,474 — 54,474 Commercial paper — 5,965 — 5,965 U.S. government securities — 118,630 — 118,630 Total investments $ — $ 196,421 $ — $ 196,421
Summary of Aggregate Market Value, Cost Basis and Gross Unrealized Gains and Losses of Available-for-Sale Investments by Security Type	The aggregate market value, cost basis, and gross unrealized gains and losses of available-for-sale investments by security type, classified in cash equivalents and investments, as of June 30, 2019 and December 31, 2018, are as follows June 30, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Total Fair Value Agency securities $ 21,243 $ 13 $ — $ 21,256 Corporate securities 44,051 102 — 44,153 Commercial paper 11,033 — — 11,033 U.S. government securities 101,129 121 — 101,250 Total available-for-sale investments $ 177,456 $ 236 $ — $ 177,692 December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Total Fair Value Agency securities $ 17,361 $ — $ (9 ) $ 17,352 Corporate securities 54,536 — (62 ) 54,474 Commercial paper 5,965 — — 5,965 U.S. government securities 118,667 14 (51 ) 118,630 Total available-for-sale investments $ 196,529 $ 14 $ (122 ) $ 196,421

Balance Sheet Components (Table

Balance Sheet Components (Tables)	6 Months Ended
	Jun. 30, 2019
Balance Sheet Related Disclosures [Abstract]
Summary of Property And Equipment, Net	Property and equipment, net consists of the following (in thousands): June 30, 2019 December 31, 2018 Furniture and equipment $ 2,642 $ 2,221 Computer equipment 2,603 2,073 Manufacturing equipment 6,473 1,733 Leased equipment 100 100 Leasehold improvements 14,506 4,469 Buildings — 688 Construction in progress 7,918 18,295 Property and equipment, gross 34,242 29,579 Less: accumulated depreciation (4,828 ) (3,251 ) Property and equipment, net $ 29,414 $ 26,328
Summary of Accrued Liabilities	Accrued liabilities consisted of the following (in thousands): June 30, 2019 December 31, 2018 Compensation and benefits $ 7,054 $ 8,912 Research and development 8,721 15,504 Professional and consulting 10,829 4,691 Other 479 37 Total accrued liabilities $ 27,083 $ 29,144

Long-Term Debt, Net of Discou_2

Long-Term Debt, Net of Discounts (Tables)	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Schedule of Short-term and Long-term Debt Obligations	The following table represents our short-term and long-term debt obligations (in thousands): June 30, 2019 Principal amount of long-term debt $ 41,961 Less: Current portion of long-term debt - Long-term debt, net of current portion 41,961 Unamortized discount relating to deferred financing costs, net (3,559 ) Accrued exit fee payment 124 Long-term debt, net of discount and current portion $ 38,526
Schedule of Future Principal Payments of Long-term Debt	Future principal payments of our long-term debt as of June 30, 2019 are as follows: Fiscal year ending December 31: 2019 $ - 2020 - 2021 - 2022 - 2023 20,981 Thereafter 20,980 Total $ 41,961

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2019
Commitments And Contingencies Disclosure [Abstract]
Schedule of Maturities of Operating Lease Liabilities	As of June 30, 2019, the maturities of our operating lease liabilities were as follows (in thousands): Remaining Lease Payments June 30, 2019 Operating Financing Total 2019 $ 1,567 $ 17 $ 1,584 2020 3,330 34 3,364 2021 3,413 35 3,448 2022 3,497 9 3,506 2023 3,378 - 3,378 Thereafter 1,744 - 1,744 Total lease payments $ 16,929 $ 95 $ 17,024 Less: Effects of discounting (3,871 ) (29 ) (3,900 ) Present value of lease liabilities $ 13,058 $ 66 $ 13,124 Less: current portion (2,022 ) (19 ) (2,041 ) Long-term lease liabilities $ 11,036 $ 47 $ 11,083 Weighted-average remaining lease term 5 years 2.8 years Weighted-average incremental borrowing rate 11 % 23 %
Component of Lease Costs Included in Condensed Consolidated Statements of Income	The component of our lease costs included in our condensed consolidated statements of income were as follows (in thousands): Quarter Ended Six Months Ended Lease Cost June 30, 2019 Operating lease cost $ 914 $ 1,879 Finance lease cost Amortization of leased assets 8 16 Interest on lease liabilities 4 8 Net lease cost $ 926 $ 1,903
Schedule of Other Information Related to Operating Lease	Other information related to our operating lease was as follows (in thousands): Other Information Six Months Ended June 30, 2019 Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating leases $ 1,879 Operating cash flows from finance leases $ 24
Schedule of Future Aggregate Minimum Lease Payments Calculated under ASC 840	Total future aggregate minimum lease payments calculated under ASC 840 at December 31, 2018 were as follows (in thousands): Remaining Lease Payments December 31, 2018 Operating Financing Total 2019 $ 3,133 $ 33 $ 3,166 2020 3,330 34 3,364 2021 3,413 35 3,448 2022 3,497 9 3,506 2023 3,378 - 3,378 Thereafter 1,744 - 1,744 Total lease payments $ 18,495 $ 111 $ 18,606 Less: amount representing interest - (33 ) (33 ) Value of lease liabilities under ASC 840 $ 18,495 $ 78 $ 18,573 Less: current portion (3,133 ) (17 ) (3,150 ) Long-term lease liabilities $ 15,362 $ 61 $ 15,423

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2019
Summary of Stock Option Activity	Option activity under the 2015 Plan and 2013 Plan is set forth below: Options Outstanding Number Options Weighted- Average Exercise Price Weighted Average Remaining Contractual Life (in years) Aggregate Intrinsic Value (in thousands) Balance, December 31, 2018 7,133,113 $ 20.08 7.6 $ 27,413 Options granted 2,318,442 22.52 Options exercised and shares vested (366,221 ) 14.23 Options cancelled (515,002 ) 28.19 Balance, June 30, 2019 8,570,332 20.50 7.6 $ 28,934 Options vested and expected to vest as of June 30, 2019 8,017,038 20.22 7.5 $ 28,771 Options exercisable as of June 30, 2019 3,891,087 $ 15.93 6.3 $ 26,175
Restricted Stock Unit Activity	Restricted stock unit, or RSU, activity under the 2015 Plan is set forth below: Shares Weighted Average Grant Date Fair Value Unvested Balance, December 31, 2018 309,847 $ 33.37 Awarded 476,127 23.06 Released (91,354 ) 33.28 Forfeited (54,791 ) 29.72 Unvested Balance, June 30, 2019 639,829 $ 26.02
Summary of Stock-based Compensation Expense	Stock-Based Compensation Expense Stock-based compensation expense, net of estimated forfeitures, reflected in the condensed consolidated statements of comprehensive loss is as follows (in thousands): Quarter Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Research and development $ 2,957 $ 2,923 $ 5,700 $ 4,970 General and administrative 5,783 5,751 10,805 11,311 Total stock-based compensation expense $ 8,740 $ 8,674 $ 16,505 $ 16,281
Schedule of Weighted Average Assumptions to Fair Value of Stock Options	The weighted-average assumptions used to estimate the fair value of stock options using the Black-Scholes option valuation model and the resulting weighted average fair value of stock options granted were as follows : Quarter Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Expected term (in years) 6.0 6.0 6.0 6.0 Expected volatility 62.2 % 68.3 % 63.2 % 68.4 % Risk free interest rate 2.3 % 2.6 % 2.5 % 2.4 % Dividend yield — % — % — % — % Weighted average estimated fair value $ 11.93 $ 19.10 $ 13.38 $ 20.51
Summary of Unrecognized Stock-Based Compensation Expense and Expected Period	As of June 30, 2019, total unrecognized stock-based compensation expense and expected period over which such compensation will be recognized were as follows ($ in thousands): As of June 30, 2019 Stock-option Unrecognized stock compensation expense $ 60,246 Weighted-average remaining vesting period (years) 2.8 RSU Unrecognized stock compensation expense $ 11,753 Weighted-average remaining vesting period (years) 2.94 ESPP Unrecognized stock compensation expense $ 237 Weighted-average remaining vesting period (years) 0.38
Employee Stock Purchase Plan
Schedule of Weighted Average Assumptions to Fair Value of Stock Options	The weighted-average assumptions used to estimate the fair value of ESPP using the Black-Scholes option valuation model were as follows: Quarter Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Expected term (in years) 0.5 0.5 0.5 0.9 Expected volatility 50.7 % 47.0 % 50.7 % 50.4 % Risk free interest rate 2.4 % 2.1 % 2.4 % 1.8 % Dividend yield — % — % — % — % Weighted average estimated fair value $ 6.00 $ 8.41 $ 6.00 $ 12.42
Restricted Stock
Summary of Stock-based Compensation Expense	Stock-based compensation expense recognized during the quarters and six months ended June 30, 2019 and 2018 related to these shares was as follows (in thousands): 2019 2018 Quarter ended June 30 $ 532 $ 830 Six months ended June 30 890 1,907

Net Loss per Share (Tables)

Net Loss per Share (Tables)	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Schedule of Antidilutive Securities Excluded from Computation of Diluted Net Loss per Share	The following common stock equivalents were excluded from the computation of diluted net loss per share for the periods presented because their inclusion would have been antidilutive: Quarter Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Stock options 8,570,332 7,516,362 8,570,332 7,516,362 RSUs 639,829 360,574 639,829 360,574

Formation and Business of the_2

Formation and Business of the Company - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Net loss	$ 62,878	$ 54,266	$ 52,552	$ 49,500	$ 117,144	$ 102,052
Net cash used in operating activities	92,000				91,995	$ 76,317
Accumulated deficit	593,326				593,326		$ 476,234
Cash, cash equivalents and investments	$ 250,300				$ 250,300

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)Segment
Significant Accounting Policies [Line Items]
Number of reportable segments | Segment	1
Operating lease, right-of-use asset	$ 11,736
Operating lease, liability	13,058
ASU 2016-02
Significant Accounting Policies [Line Items]
Operating lease, right-of-use asset	11,700
Operating lease, liability	$ 13,100

Available-for-Sale Securities_3

Available-for-Sale Securities and Fair Value Measurements - Summary of Financial Instruments Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Investments:
Total investments	$ 177,692	$ 196,421
Agency Securities
Investments:
Total investments	21,256	17,352
Corporate Debt Securities
Investments:
Total investments	44,153	54,474
Commercial Paper
Investments:
Total investments	11,033	5,965
U.S. Government Securities
Investments:
Total investments	101,250	118,630
Fair Value Measurements Recurring
Cash and cash equivalents
Total cash and cash equivalents	72,564	107,511
Investments:
Total investments	177,692	196,421
Fair Value Measurements Recurring | Cash and Money Market Funds
Cash and cash equivalents
Total cash and cash equivalents	72,564	107,511
Fair Value Measurements Recurring | Agency Securities
Investments:
Total investments	21,256	17,352
Fair Value Measurements Recurring | Corporate Debt Securities
Investments:
Total investments	44,153	54,474
Fair Value Measurements Recurring | Commercial Paper
Investments:
Total investments	11,033	5,965
Fair Value Measurements Recurring | U.S. Government Securities
Investments:
Total investments	101,250	118,630
Level 1 | Fair Value Measurements Recurring
Cash and cash equivalents
Total cash and cash equivalents	72,564	107,511
Level 1 | Fair Value Measurements Recurring | Cash and Money Market Funds
Cash and cash equivalents
Total cash and cash equivalents	72,564	107,511
Level 2 | Fair Value Measurements Recurring
Investments:
Total investments	177,692	196,421
Level 2 | Fair Value Measurements Recurring | Agency Securities
Investments:
Total investments	21,256	17,352
Level 2 | Fair Value Measurements Recurring | Corporate Debt Securities
Investments:
Total investments	44,153	54,474
Level 2 | Fair Value Measurements Recurring | Commercial Paper
Investments:
Total investments	11,033	5,965
Level 2 | Fair Value Measurements Recurring | U.S. Government Securities
Investments:
Total investments	$ 101,250	$ 118,630

Available-for-Sale Securities_4

Available-for-Sale Securities and Fair Value Measurements - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Fair value assets transfers between level 1 to level 2	$ 0	$ 0	$ 0	$ 0
Fair value assets transfers between level 2 to level 1	0	0	$ 0	0
Available-for-sale securities, maturities period			18 months
Other than temporary impairment losses	$ 0	$ 0	$ 0	$ 0
Marketable securities unrealized losses position maximum period			12 months

Available-for-Sale Securities_5

Available-for-Sale Securities and Fair Value Measurements - Summary of Aggregate Market Value, Cost Basis, and Gross Unrealized Gains and Losses of Available for Sale Investments by Security Type (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	$ 177,456	$ 196,529
Gross Unrealized Gains	236	14
Gross Unrealized Losses		(122)
Total investments	177,692	196,421
Agency Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	21,243	17,361
Gross Unrealized Gains	13
Gross Unrealized Losses		(9)
Total investments	21,256	17,352
Corporate Debt Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	44,051	54,536
Gross Unrealized Gains	102
Gross Unrealized Losses		(62)
Total investments	44,153	54,474
Commercial Paper
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	11,033	5,965
Total investments	11,033	5,965
U.S. Government Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	101,129	118,667
Gross Unrealized Gains	121	14
Gross Unrealized Losses		(51)
Total investments	$ 101,250	$ 118,630

Balance Sheet Components - Summ

Balance Sheet Components - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 34,242	$ 29,579
Less: accumulated depreciation	(4,828)	(3,251)
Property and equipment, net	29,414	26,328
Furniture and Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	2,642	2,221
Computer Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	2,603	2,073
Manufacturing Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	6,473	1,733
Leased Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	100	100
Leasehold improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	14,506	4,469
Buildings
Property Plant And Equipment [Line Items]
Property and equipment, gross		688
Construction in Progress
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 7,918	$ 18,295

Balance Sheet Components - Su_2

Balance Sheet Components - Summary of Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accrued Liabilities Current [Abstract]
Compensation and benefits	$ 7,054	$ 8,912
Research and development	8,721	15,504
Professional and consulting	10,829	4,691
Other	479	37
Total accrued liabilities	$ 27,083	$ 29,144

Long-Term Debt, Net of Discou_3

Long-Term Debt, Net of Discounts - Additional Information (Details)	Dec. 31, 2023	Jan. 03, 2021	Jan. 31, 2019USD ($)Tranche	Jun. 30, 2019USD ($)	Jan. 01, 2021USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2018USD ($)
Debt Instrument [Line Items]
Payment of fees including debt issuance costs				$ 3,856,000
Long term debt, outstanding				$ 41,961,000
KKR Loans
Debt Instrument [Line Items]
Loan agreement, maximum borrowing capacity			$ 170,000,000
Debt instrument number of tranches | Tranche			3
Loan agreement, proceeds receivable upon closing of transaction			$ 40,000,000
Loan agreement, proceeds receivable upon FDA approval			85,000,000
Loan agreement, remaining borrowing capacity upon certain conditions			$ 45,000,000
Line of credit facility maturity date			Jan. 3, 2025
Regulatory approval last date			Dec. 31, 2020
Line of credit facility without regulatory approval expiration date			Jan. 15, 2021
Loan prepayment fee percentage, after January 3, 2021 but on or prior to January 3, 2022				5.00%
Loan prepayment fee percentage, after January 3, 2022 but on or prior to January 3, 2023				2.00%
Loan prepayment fee percentage, thereafter				0.00%
Line of credit facility, prepayment premium amount				$ 3,400,000
Loan exit fee percentage				4.00%
Payment of fees including debt issuance costs				$ 3,900,000
Long term debt, outstanding				$ 41,900,000			$ 0
Debt instrument, interest rate				9.94%
KKR Loans | Scenario, Forecast
Debt Instrument [Line Items]
Other loans trigger amount to reduce 91 days maturity of credit facility					$ 25,000,000	$ 15,000,000
Loan, spread on variable rate		0.50%
Loan redemption price, percentage	50.00%
Line of credit facility, interest rate	12.50%
Percentage of principal amount of loans prepayment paid on or prior to January 3, 2021		105.00%
KKR Loans | Alternate Base Rate
Debt Instrument [Line Items]
Loan, spread on variable rate			6.50%
KKR Loans | 30-day LIBOR
Debt Instrument [Line Items]
Loan, spread on variable rate			7.50%

Long-Term Debt, Net of Discou_4

Long-Term Debt, Net of Discounts - Schedule of Short-term and Long-term Debt Obligations (Details) $ in Thousands	Jun. 30, 2019USD ($)
Debt Disclosure [Abstract]
Principal amount of long-term debt	$ 41,961
Long-term debt, net of current portion	41,961
Unamortized discount relating to deferred financing costs, net	(3,559)
Accrued exit fee payment	124
Long-term debt, net of discount and current portion	$ 38,526

Long-Term Debt, Net of Discou_5

Long-Term Debt, Net of Discounts - Schedule of Future Principal Payments of Long-Term Debt (Details) $ in Thousands	Jun. 30, 2019USD ($)
Debt Disclosure [Abstract]
2023	$ 20,981
Thereafter	20,980
Total	$ 41,961

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Millions	1 Months Ended		6 Months Ended
	May 31, 2019	Jan. 31, 2018USD ($)Trancheshares	Jun. 30, 2019USD ($)
Commitments And Contingencies [Line Items]
Operating lease, description			We lease facilities for office and manufacturing space under various operating leases and a security system under a financing lease.
Finance Lease, Description			We lease facilities for office and manufacturing space under various operating leases and a security system under a financing lease.
Operating lease, existence of option to extend			true
Operating lease, option to extend			Our leases have remaining lease terms of approximately 1 year to 6 years, which represent the non-cancellable periods of the leases and include extension options that we determined are reasonably certain to be exercised. We exclude extension options that are not reasonably certain to be exercised from our lease terms.
Finance lease, existence of option to extend			true
Finance lease, option to extend			Our leases have remaining lease terms of approximately 1 year to 6 years, which represent the non-cancellable periods of the leases and include extension options that we determined are reasonably certain to be exercised. We exclude extension options that are not reasonably certain to be exercised from our lease terms.
Operating lease, variable lease payment, terms and conditions			We use our incremental borrowing rate to calculate the present value of our lease payments, as the implicit rates in our leases are not readily determinable.
Finance lease, variable lease payment, terms and conditions			We use our incremental borrowing rate to calculate the present value of our lease payments, as the implicit rates in our leases are not readily determinable.
Archer Daniels Midland Company
Commitments And Contingencies [Line Items]
Long-term purchase commitment, restated agreement effective period after first delivery		10 years
Long-term purchase commitment, optional extension period		5 years
Long-term purchase commitment amount			$ 3.3
Long-term purchase commitment period			10 years
Archer Daniels Midland Company | Restricted Stock | Common Stock
Commitments And Contingencies [Line Items]
Long-term purchase commitment, shares issued | shares		300,000
Long-term purchase commitment, shares issued, vesting period		3 years 6 months
Long-term purchase commitment, fair value		$ 11.7
Number of tranches for vesting of shares | Tranche		4
CoreRx, Inc.
Commitments And Contingencies [Line Items]
Long-term purchase commitment amount			$ 4.3
Long-term purchase commitment expiration date	Dec. 31, 2024
Long-term purchase commitment renewal term	2 years
CoreRx, Inc. | AR101 Commercial Supply Requirements
Commitments And Contingencies [Line Items]
Percentage of long term purchase commitment minimum required quantity	100.00%
Number of years for minimum supply percentage after approval	6 years
Annual purchase commitments beginning year	2019
Annual purchase commitments ending year	2024
CoreRx, Inc. | AR101 Commercial Supply Requirements for Release Testing
Commitments And Contingencies [Line Items]
Percentage of long term purchase commitment minimum required quantity	100.00%
Number of years for minimum supply percentage after approval	6 years
Annual purchase commitments beginning year	2019
Annual purchase commitments ending year	2024
Manufacturing Facility
Commitments And Contingencies [Line Items]
Additional operating leases, not yet commenced, amount			$ 0.7
Additional operating leases, not yet commenced, description			we have additional operating leases, primarily for our manufacturing facility
Additional operating leases, not yet commenced, term			6 years 3 months
Minimum
Commitments And Contingencies [Line Items]
Remaining lease terms			1 year
Maximum
Commitments And Contingencies [Line Items]
Remaining lease terms			6 years
Maximum | Michael Foods, Inc.
Commitments And Contingencies [Line Items]
Long-term purchase commitment period			15 years

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Maturities of Operating Lease Liabilities (Details) $ in Thousands	Jun. 30, 2019USD ($)
Commitments And Contingencies Disclosure [Abstract]
Operating lease, 2019	$ 1,567
Operating lease, 2020	3,330
Operating lease, 2021	3,413
Operating lease, 2022	3,497
Operating lease, 2023	3,378
Operating lease, Thereafter	1,744
Operating Lease, Total lease payments	16,929
Less: Operating lease, Effects of discounting	(3,871)
Operating lease, Present value of lease liabilities	13,058
Less: Operating lease, current portion	(2,022)
Operating lease, Long-term lease liabilities	$ 11,036
Operating Lease, Weighted-average remaining lease term	5 years
Operating Lease, Weighted-average incremental borrowing rate	11.00%
Financing lease, 2019	$ 17
Financing lease, 2020	34
Financing lease, 2021	35
Financing lease, 2022	9
Financing lease, Total lease payments	95
Less: Financing lease, Effects of discounting	(29)
Financing lease, Present value of lease liabilities	66
Less: Financing lease, current portion	(19)
Financing lease, Long-term lease liabilities	$ 47
Financing lease, Weighted-average remaining lease term	2 years 9 months 18 days
Financing lease, Weighted-average incremental borrowing rate	23.00%
Remaining Lease Payments, 2019	$ 1,584
Remaining Lease Payments, 2020	3,364
Remaining Lease Payments, 2021	3,448
Remaining Lease Payments, 2022	3,506
Remaining Lease Payments, 2023	3,378
Remaining Lease Payments, Thereafter	1,744
Total lease payments	17,024
Less: Effects of discounting	(3,900)
Present value of lease liabilities	13,124
Less: current portion	(2,041)
Long-term lease liabilities	$ 11,083

Commitments and Contingencies_3

Commitments and Contingencies - Component of Lease Costs Included in Condensed Consolidated Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Lease Cost
Operating lease cost	$ 914	$ 1,879
Finance lease cost
Amortization of leased assets	8	16
Interest on lease liabilities	4	8
Net lease cost	$ 926	$ 1,903

Commitments and Contingencies_4

Commitments and Contingencies - Schedule of Other Information Related to Operating Lease (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases	$ 1,879
Operating cash flows from finance leases	$ 24

Commitments and Contingencies_5

Commitments and Contingencies - Schedule of Future Aggregate Minimum Lease Payments Calculated under ASC 840 (Details) $ in Thousands	Dec. 31, 2018USD ($)
Commitments And Contingencies Disclosure [Abstract]
Operating Lease, 2019	$ 3,133
Operating Lease, 2020	3,330
Operating Lease, 2021	3,413
Operating Lease, 2022	3,497
Operating Lease, 2023	3,378
Operating Lease, Thereafter	1,744
Operating Lease, Total lease payments	18,495
Less: Operating Lease, current portion	(3,133)
Operating Lease, Long-term lease liabilities	15,362
Financing Lease, 2019	33
Financing Lease, 2020	34
Financing Lease, 2021	35
Financing Lease, 2022	9
Total financing lease payments	111
Less: Financing Lease, amount representing interest	(33)
Financing Lease Value of lease liabilities under ASC 840	78
Less: Financing Lease, current portion	(17)
Financing Lease, Long-term lease liabilities	61
Remaining Lease Payments, 2019	3,166
Remaining Lease Payments, 2020	3,364
Remaining Lease Payments, 2021	3,448
Remaining Lease Payments, 2022	3,506
Remaining Lease Payments, 2023	3,378
Remaining Lease Payments, Thereafter	1,744
Total lease payments	18,606
Less: amount representing interest	(33)
Value of lease liabilities under ASC 840	18,573
Less: current portion	(3,150)
Long-term lease liabilities	$ 15,423

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($)	1 Months Ended				3 Months Ended		6 Months Ended		12 Months Ended
	Feb. 28, 2019	Jan. 31, 2018	Aug. 31, 2015	Jul. 31, 2015	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Restricted Stock | Common Stock | Archer Daniels Midland Company
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options vesting period		3 years 6 months
Long-term purchase commitment, shares issued		300,000
Long-term purchase commitment, shares issued, vesting period		3 years 6 months
Stock-based compensation, shares vested							75,000
Unrecognized employee stock-based compensation					$ 3,600,000		$ 3,600,000
Expected recognized over weighted-average remaining vesting period							2 years 10 days
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Recognized stock-based compensation expense					11,753,000		$ 11,753,000
Certain Key Employees | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of restricted stock issued	52,000
Restricted stock units, aggregate grant date fair value	$ 1,300,000
Recognized stock-based compensation expense					0		0
Former Executive
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Accelerated stock compensation expense					$ 500,000	$ 900,000	$ 1,000,000	$ 2,100,000
2015 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares reserved for issuance				4,681,544
Number of shares available for future grant					4,625,878		4,625,878		4,364,963
Minimum percentage of voting rights of all classes of stock				10.00%
Percentage of statutory stock options				110.00%
Options expiration period				10 years
2015 Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options expiration period				10 years
2015 Plan | First Anniversary
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options vesting period				4 years
Option vesting rights, percentage				25.00%
2015 Plan | Thereafter
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option vesting rights, percentage				2.08%
2015 Plan | Over Two Years
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options vesting period				2 years
Option vesting rights, percentage				4.17%
2015 Plan | Over Four Years
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options vesting period				4 years
Option vesting rights, percentage				2.08%
2015 ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of statutory stock options			85.00%
Description of ESPP							Under the 2015 ESPP our employees may purchase common stock through payroll deductions at a price equal to 85% of the lower of the fair market value of the stock at the beginning of the offering period or at the end of each applicable purchase period. The 2015 ESPP generally provides for offering periods of six months in duration with purchase periods ending on either May 15 or November 15. Contributions under the 2015 ESPP are limited to a maximum of 15% of an employee’s eligible compensation.
Percentage of maximum contributions employee's eligible compensation			15.00%
ESPP offering period			6 months
Description of offering period closing dates							The 2015 ESPP generally provides for offering periods of six months in duration with purchase periods ending on either May 15 or November 15
Shares issued under the plan							59,722		41,030
Weighted average price per share					$ 17.75		$ 17.75		$ 25.28
Employee stock purchase plan remain available for purchase							2,346,064
2013 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares reserved for issuance					0		0
Number of shares available for future grant					0		0

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Number of Options
Number of Options, Beginning Balance	7,133,113
Number of Options, Options granted	2,318,442
Number of Options, Options exercised and shares vested	(366,221)
Number of Options, Options cancelled	(515,002)
Number of Options, Ending Balance	8,570,332	7,133,113
Number of Options, Options vested and expected to vest as of June 30, 2019	8,017,038
Number of Options, Options exercisable as of June 30, 2019	3,891,087
Weighted-Average Exercise Price
Weighted-Average Exercise Price, Beginning Balance	$ 20.08
Weighted-Average Exercise Price, Options granted	22.52
Weighted-Average Exercise Price, Options exercised and shares vested	14.23
Weighted-Average Exercise Price, Options cancelled	28.19
Weighted-Average Exercise Price, Ending Balance	20.50	$ 20.08
Weighted-Average Exercise Price, Options vested and expected to vest as of June 30, 2019	20.22
Weighted-Average Exercise Price, Options exercisable as of June 30, 2019	$ 15.93
Weighted Average Remaining Contractual Life (in years)
Weighted Average Remaining Contractual Life (in years), Balance	7 years 7 months 6 days	7 years 7 months 6 days
Weighted Average Remaining Contractual Life, Options vested and expected to vest as of June 30, 2019	7 years 6 months
Weighted Average Remaining Contractual Life, Options exercisable as of June 30, 2019	6 years 3 months 18 days
Aggregate Intrinsic Value, Balance	$ 28,934	$ 27,413
Aggregate Intrinsic Value, Options vested and expected to vest as of June 30, 2019	28,771
Aggregate Intrinsic Value, Options exercisable as of June 30, 2019	$ 26,175

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Stock Unit Activity (Details) - 2015 Plan - Restricted Stock Units (RSUs)	6 Months Ended
	Jun. 30, 2019$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested Shares, Beginning Balance | shares	309,847
Shares, Awarded | shares	476,127
Shares, Released | shares	(91,354)
Shares, Forfeited | shares	(54,791)
Unvested Shares, Ending Balance | shares	639,829
Unvested Weighted Average Grant Date Fair Value, Beginning Balance | $ / shares	$ 33.37
Weighted Average Grant Date Fair Value, Awarded | $ / shares	23.06
Weighted Average Grant Date Fair Value, Released | $ / shares	33.28
Weighted Average Grant Date Fair Value, Forfeited | $ / shares	29.72
Weighted Average Grant Date Fair Value, Ending Balance | $ / shares	$ 26.02

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Stock-based Compensation Expense Recognized (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Restricted Stock | Common Stock | Archer Daniels Midland Company
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 532	$ 830	$ 890	$ 1,907

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Weighted Average Assumptions to Fair Value of Stock Options (Details) - $ / shares	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]
Expected term (in years)	6 years	6 years	6 years	6 years
Expected volatility	62.20%	68.30%	63.20%	68.40%
Risk free interest rate	2.30%	2.60%	2.50%	2.40%
Weighted average estimated fair value	$ 11.93	$ 19.10	$ 13.38	$ 20.51
Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 months	6 months	6 months	10 months 24 days
Expected volatility	50.70%	47.00%	50.70%	50.40%
Risk free interest rate	2.40%	2.10%	2.40%	1.80%
Weighted average estimated fair value	$ 6	$ 8.41	$ 6	$ 12.42

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Stock-based Compensation Expense Net of Estimated Forfeitures (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 8,740	$ 8,674	$ 16,505	$ 16,281
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	2,957	2,923	5,700	4,970
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 5,783	$ 5,751	$ 10,805	$ 11,311

Stock-Based Compensation - Su_4

Stock-Based Compensation - Summary of Unrecognized Stock-Based Compensation Expense and Expected Period (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock compensation expense	$ 60,246
Weighted-average remaining vesting period (years)	2 years 9 months 18 days
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average remaining vesting period (years)	2 years 11 months 8 days
Unrecognized stock compensation expense	$ 11,753
ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average remaining vesting period (years)	4 months 17 days
Unrecognized stock compensation expense	$ 237

Net Loss per Share - Schedule o

Net Loss per Share - Schedule of Antidilutive Securities Excluded from Computation of Diluted Net Loss per Share (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	8,570,332	7,516,362	8,570,332	7,516,362
RSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	639,829	360,574	639,829	360,574

Related Party Transaction - Add

Related Party Transaction - Additional Information (Details) - MyHealth Teams - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Related Party Transaction [Line Items]
Payments to service agreement	$ 100,000	$ 100,000	$ 100,000	$ 100,000
Accrued liabilities due	$ 0		$ 0		$ 0