Tricida (TCDAQ) 10-Q 6 Aug 20 2020 Q2 Quarterly report Financial data

Cover Page

Cover Page - $ / shares	6 Months Ended
	Jun. 30, 2020	Jul. 31, 2020	Dec. 31, 2019	Jul. 02, 2018
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2020
Document Transition Report	false
Entity File Number	001-38558
Entity Registrant Name	TRICIDA, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-3372526
Entity Address, Address Line One	7000 Shoreline Court
Entity Address, Address Line Two	Suite 201
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	415
Local Phone Number	429-7800
Title of 12(b) Security	Common stock, par value $0.001 per share
Trading Symbol	TCDA
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		50,048,972
Common stock, par value (in USD per share)	$ 0.001		$ 0.001	$ 0.001
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Entity Central Index Key	0001595585
Current Fiscal Year End Date	--12-31

CONDENSED BALANCE SHEETS (Unaud

CONDENSED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 41,900	$ 18,574
Short-term investments	345,632	289,424
Prepaid expenses and other current assets	9,830	4,744
Total current assets	397,362	312,742
Long-term investments	49,371	46,980
Property and equipment, net	1,432	2,728
Operating lease right-of-use assets	8,734	9,376
Total assets	456,899	371,826
Current liabilities:
Accounts payable	5,839	5,911
Current operating lease liabilities	1,088	1,072
Current Term Loan	6,784	0
Accrued expenses and other current liabilities	20,769	32,780
Total current liabilities	34,480	39,763
Non-current Term Loan, net	67,952	58,374
Convertible Senior Notes, net	114,645	0
Non-current operating lease liabilities	8,515	8,783
Other long-term liabilities	327	1,023
Total liabilities	225,919	107,943
Commitments and contingencies (Note 7)
Stockholders’ equity:
Preferred stock, $0.001 par value; 40,000,000 shares authorized, no shares issued or outstanding as of June 30, 2020 and December 31, 2019	0	0
Common stock, $0.001 par value; 400,000,000 shares authorized as of June 30, 2020 and December 31, 2019; 50,039,587 and 49,763,176 shares issued and outstanding as of June 30, 2020 and December 31, 2019, respectively.	50	50
Additional paid-in capital	731,358	632,647
Accumulated other comprehensive income (loss)	863	193
Accumulated deficit	(501,291)	(369,007)
Total stockholders’ equity	230,980	263,883
Total liabilities and stockholders’ equity	$ 456,899	$ 371,826

CONDENSED BALANCE SHEETS (Paren

CONDENSED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Preferred stock, par value (in USD per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	40,000,000	40,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (in USD per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	400,000,000	400,000,000
Common stock, shares issued (in shares)	50,039,587	49,763,176
Common stock, shares outstanding (in shares)	50,039,587	49,763,176

CONDENSED STATEMENTS OF OPERATI

CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating expenses:
Research and development	$ 28,757	$ 28,976	$ 78,138	$ 60,399
General and administrative	28,418	8,861	51,944	15,213
Total operating expenses	57,175	37,837	130,082	75,612
Loss from operations	(57,175)	(37,837)	(130,082)	(75,612)
Other income (expense), net	2,675	2,602	3,488	3,869
Interest expense	(3,756)	(1,391)	(5,776)	(2,780)
Loss before income taxes	(58,256)	(36,626)	(132,370)	(74,523)
Income Tax Expense (Benefit)	86	0	86	0
Net loss	(58,170)	(36,626)	(132,284)	(74,523)
Other comprehensive income (loss):
Net unrealized gain (loss) on available-for-sale investments, net of tax	902	480	670	782
Total comprehensive loss	$ (57,268)	$ (36,146)	$ (131,614)	$ (73,741)
Net loss per share, basic and diluted (in USD per share)	$ (1.16)	$ (0.75)	$ (2.65)	$ (1.64)
Weighted-average number of shares outstanding, basic and diluted (in shares)	49,960,072	48,674,238	49,900,739	45,489,861

CONDENSED STATEMENTS STOCKHOLDE

CONDENSED STATEMENTS STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2018		42,148,247
Beginning balance at Dec. 31, 2018	$ 194,525	$ 42	$ 386,830	$ (153)	$ (192,194)
Total Stockholders’ Equity
Issuance of warrant in connection with Term Loan	284		284
Issuance of common stock under equity incentive plans (in shares)		527,859
Issuance of common stock under equity incentive plans	737	$ 1	736
Stock-based compensation	2,658		2,658
Net unrealized gain (loss) on available-for-sale investments	302			302
Net loss	(37,897)				(37,897)
Ending balance (in shares) at Mar. 31, 2019		42,676,106
Ending balance at Mar. 31, 2019	160,609	$ 43	390,508	149	(230,091)
Beginning balance (in shares) at Dec. 31, 2018		42,148,247
Beginning balance at Dec. 31, 2018	194,525	$ 42	386,830	(153)	(192,194)
Total Stockholders’ Equity
Net unrealized gain (loss) on available-for-sale investments	782
Net loss	(74,523)
Ending balance (in shares) at Jun. 30, 2019		49,276,445
Ending balance at Jun. 30, 2019	346,844	$ 49	612,883	629	(266,717)
Beginning balance (in shares) at Mar. 31, 2019		42,676,106
Beginning balance at Mar. 31, 2019	160,609	$ 43	390,508	149	(230,091)
Total Stockholders’ Equity
Issuance of common stock in connection with public offering, net of underwriter discounts and issue costs (in shares)		6,440,000
Issuance of common stock in connection with public offering, net of underwriter discounts and issuance costs	217,009	$ 6	217,003
Issuance of common stock under equity incentive plans (in shares)		160,339
Issuance of common stock under equity incentive plans	959		959
Stock-based compensation	4,413		4,413
Net unrealized gain (loss) on available-for-sale investments	480			480
Net loss	(36,626)				(36,626)
Ending balance (in shares) at Jun. 30, 2019		49,276,445
Ending balance at Jun. 30, 2019	$ 346,844	$ 49	612,883	629	(266,717)
Beginning balance (in shares) at Dec. 31, 2019	49,763,176	49,763,176
Beginning balance at Dec. 31, 2019	$ 263,883	$ 50	632,647	193	(369,007)
Total Stockholders’ Equity
Issuance of common stock under equity incentive plans (in shares)		150,056
Issuance of common stock under equity incentive plans	550	$ 0	550
Stock-based compensation	8,374		8,374
Net unrealized gain (loss) on available-for-sale investments	(232)			(232)
Net loss	(74,114)				(74,114)
Ending balance (in shares) at Mar. 31, 2020		49,913,232
Ending balance at Mar. 31, 2020	$ 198,461	$ 50	641,571	(39)	(443,121)
Beginning balance (in shares) at Dec. 31, 2019	49,763,176	49,763,176
Beginning balance at Dec. 31, 2019	$ 263,883	$ 50	632,647	193	(369,007)
Total Stockholders’ Equity
Net unrealized gain (loss) on available-for-sale investments	670
Net loss	$ (132,284)
Ending balance (in shares) at Jun. 30, 2020	50,039,587	50,039,587
Ending balance at Jun. 30, 2020	$ 230,980	$ 50	731,358	863	(501,291)
Beginning balance (in shares) at Mar. 31, 2020		49,913,232
Beginning balance at Mar. 31, 2020	198,461	$ 50	641,571	(39)	(443,121)
Total Stockholders’ Equity
Issuance of warrant in connection with Term Loan	112		112
Issuance of common stock under equity incentive plans (in shares)		126,355
Issuance of common stock under equity incentive plans	1,098		1,098
Stock-based compensation	9,079		9,079
Net unrealized gain (loss) on available-for-sale investments	902			902
Net loss	$ (58,170)				(58,170)
Ending balance (in shares) at Jun. 30, 2020	50,039,587	50,039,587
Ending balance at Jun. 30, 2020	$ 230,980	$ 50	731,358	$ 863	$ (501,291)
Total Stockholders’ Equity
Adjustments to Additional Paid in Capital, Convertible Debt with Conversion Feature	$ 79,498		$ 79,498

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Operating activities:
Net loss	$ (132,284)	$ (74,523)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	474	341
Non-cash operating lease costs	390	413
Accretion (amortization) of premiums and discounts on investments	(417)	(2,031)
Accretion of Term Loan and Convertible Senior Notes	2,331	1,011
Stock-based compensation	17,453	7,071
Changes in fair value of compound derivative liability	(650)	165
Other non-cash items	(86)	0
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(5,113)	(1,393)
Accounts payable	(113)	(3,785)
Accrued expenses and other liabilities	(10,623)	16,240
Operating lease liabilities	0	(438)
Net cash used in operating activities	(128,638)	(56,929)
Investing activities:
Purchases of investments	(229,289)	(299,085)
Maturities of investments	171,955	127,557
Purchases of property and equipment	(600)	(1,021)
Net cash used in investing activities	(57,934)	(172,549)
Financing activities:
Proceeds from equity offerings, net	0	217,930
Payments of equity offering costs	0	(921)
Proceeds from issuance of common stock under equity incentive plans	1,670	1,608
Proceeds from Convertible Senior Notes, net	193,285	0
Repayment of leasehold improvement loan	(28)	(65)
Proceeds (payments) under Term Loan, net	14,971	(1,449)
Net cash provided by financing activities	209,898	217,103
Net increase (decrease) in cash and cash equivalents	23,326	(12,375)
Cash and cash equivalents at beginning of period	18,574	37,172
Cash and cash equivalents at end of period	41,900	24,797
Supplemental disclosures
Cash paid for interest	2,536	1,650
Supplemental disclosures of non-cash investing and financing activities
Warrants related to Term Loan	112	284
Purchases of property and equipment included in accounts payable and accrued expenses	$ 428	$ 24

ORGANIZATION AND BASIS OF PRESE

ORGANIZATION AND BASIS OF PRESENTATION	6 Months Ended
	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION AND BASIS OF PRESENTATION	ORGANIZATION AND BASIS OF PRESENTATION Organization —Tricida, Inc., or the Company, was incorporated in the state of Delaware on May 22, 2013 and was granted its certification of qualification in the state of California on August 5, 2013, or inception. The Company is focused on the development and commercialization of its drug candidate, veverimer (also known as TRC101), a non-absorbed, orally-administered polymer designed to treat metabolic acidosis in patients with chronic kidney disease. The Company has sustained operating losses and expects such annual losses to continue over the next several years. The Company’s ultimate success depends on the outcome of its research and development and commercialization activities for veverimer, for which it expects to incur additional losses in the future. Through June 30, 2020, the Company has relied primarily on the proceeds from equity offerings and debt financing to finance its operations. The Company recognizes that it may need to raise additional capital to fully implement its business plan, and if market conditions are favorable or if the Company identifies specific strategic opportunities or needs, intends to do so through the issuance of equity, borrowings, or strategic alliances with partner companies. However, if such financing is not available at adequate levels or on reasonable terms, the Company will need to reevaluate its operating plans and could be required to significantly reduce operating expenses and delay, reduce the scope of or eliminate some of its development programs or its future commercialization efforts, out-license intellectual property rights to its product candidates and sell unsecured assets, or a combination of the above, any of which may have a material adverse effect on its business, results of operations, financial condition and/or its ability to fund its scheduled obligations on a timely basis or at all. Basis of Presentation —The accompanying unaudited condensed financial statements have been prepared in accordance with accounting principles generally accepted in the United States, or U.S. GAAP, for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. The condensed balance sheet as of June 30, 2020, the condensed statements of operations and comprehensive loss for the three and six months ended June 30, 2020 and 2019, the condensed statements of stockholders' equity for the three and six months ended June 30, 2020 and 2019 and the condensed statements of cash flows for the six months ended June 30, 2020 and 2019 are unaudited, but include all adjustments, consisting only of normal recurring adjustments, which the Company considers necessary for a fair presentation of the financial position, operating results and cash flows for the periods presented. The condensed balance sheet at December 31, 2019 has been derived from audited financial statements. Although the Company believes that the disclosures in these financial statements are adequate to make the information presented not misleading, certain information and footnote information normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to the rules and regulations of the Securities and Exchange Commission.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES With the exception of the change for the accounting of credit losses as a result of the adoption of Accounting Standards Update, or ASU, 2016-13, Financial Instruments - Credit Losses (Topic 326) : Measurement of Credit Losses on Financial Instruments, or ASU 2016-13, there have been no new or material changes to the significant accounting policies discussed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, that are of significance, or potential significance, to the Company. Credit Losses The Company is exposed to credit losses primarily through its available-for-sale investments. The Company invests excess cash in marketable securities with high credit ratings that are classified in Level 1 and Level 2 of the fair value hierarchy. The Company's investment portfolio at any point in time contains investments in U.S. treasury and U.S. government agency securities, taxable and tax-exempt municipal notes, corporate notes and bonds, commercial paper, non-U.S. government agency securities and money market funds, and are classified as available-for-sale. The Company assesses whether its available-for sale investments are impaired at each reporting period. Unrealized losses or impairments resulting from the fair value of the available-for-sale debt security being below the amortized cost basis are evaluated for identification of credit losses and non-credit related losses. Any credit losses are charged to earnings against the allowance for credit losses of the debt security, limited to the difference between the fair value and the amortized cost basis of the debt security. Any difference between the fair value of the debt security and the amortized cost basis, less the allowance for credit losses, are reported in other comprehensive income (loss). Expected cash inflows due to improvements in credit are recognized through a reversal of the allowance for credit losses subject to the total allowance previously recognized. The Company’s expected loss allowance methodology for the debt securities is developed by reviewing the extent of the unrealized loss, the size, term, geographical location, and industry of the issuer, the issuers’ credit ratings and any changes in those ratings, as well as reviewing current and future economic market conditions and the issuers’ current status and financial condition. The Company considered the current and expected future economic and market conditions surrounding the COVID-19 pandemic and determined that the estimate of credit losses was not significantly impacted. As of June 30, 2020, the Company has not recognized an allowance for expected credit losses related to available-for-sale investments as the Company has not identified any unrealized losses for these investments attributable to credit factors. Recent Accounting Pronouncements Adopted Standards Effective January 1, 2020, the Company adopted ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which changed the impairment model for most financial assets and certain other instruments. The Company adopted ASU 2016-13 on January 1, 2020, using a modified retrospective transition method, which requires a cumulative-effect adjustment, if any, to the opening balance of retained earnings to be recognized on the date of adoption with prior periods not restated. The adoption of ASU 2016-13 did not have a significant impact on the Company's condensed financial statements. See "Credit Losses" above for a description of the Company's credit losses accounting policy. Standards Not Yet Effective In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes , or ASU 2019-12, which simplifies the accounting for income taxes. ASU 2019-12 is effective for public business entities for annual reporting periods, and interim periods within those annual periods, beginning after December 15, 2020 on a prospective basis, and early adoption is permitted. The Company does not expect the adoption of ASU 2019-12 will have a significant impact on its financial statements.

FAIR VALUE MEASUREMENTS AND FAI

FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS	FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS The fair value of the Company’s financial assets and liabilities are determined in accordance with the fair value hierarchy established in the FASB's Accounting Standards Codification Topic 820, Fair Value Measurements and Disclosures, or Topic 820. Topic 820 defines 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 orderly transaction between market participants on the measurement date. The fair value hierarchy of Topic 820 requires an entity to maximize the use of observable inputs when measuring fair value and classifies those inputs into three levels: Level 1 —Observable inputs, such as quoted prices in active markets; Level 2 —Inputs, other than the quoted prices in active markets, which are observable either directly or indirectly such as quoted prices for similar assets or liabilities; quoted prices 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 instrument’s anticipated life; and Level 3 —Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions. Our financial instruments consist primarily of cash and cash equivalents, short-term and long-term investments, accounts payable, the Loan and Security Agreement, or Term Loan, entered into with Hercules Capital Inc., or Hercules, and the Convertible Senior Notes. Cash, cash equivalents and investments are reported at their respective fair values on the Company's condensed balance sheets. Where quoted prices are available in an active market, securities are classified as Level 1. The Company classifies money market funds and U.S. Treasury securities as Level 1. When quoted market prices are not available for the specific security, then the Company estimates fair value by using quoted prices for identical or similar instruments in markets that are not active and model-based valuation techniques for which all significant inputs are observable in the market or can be corroborated by observable market data for substantially the full term of the assets. Where applicable, these models project future cash flows and discount the future amounts to a present value using market-based observable inputs obtained from various third-party data providers, including but not limited to benchmark yields, reported trades and broker/dealer quotes. Where applicable the market approach utilizes prices and information from market transactions for similar or identical assets. The Company classifies U.S. government agency securities, commercial paper, corporate debt securities and asset-backed securities as Level 2. The Company's short-term and long-term investments are classified as available-for-sale. The following tables set forth the value of the Company's financial assets remeasured on a recurring basis based on the three-tier fair value hierarchy by significant investment category as of June 30, 2020 and December 31, 2019. June 30, 2020 Reported as: (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Cash and Cash Equivalents Short-Term Investments Long-Term Investments Cash $ 2,428 $ — $ — $ 2,428 $ 2,428 $ — $ — Level 1: Money market funds 28,476 — — 28,476 28,476 — — U.S. Treasury securities 29,896 3 — 29,899 — 18,654 11,245 Subtotal 58,372 3 — 58,375 28,476 18,654 11,245 Level 2: U.S. government agency securities 43,883 3 (11) 43,875 — 5,749 38,126 Commercial paper 181,997 351 (11) 182,337 10,996 171,341 — Corporate debt securities 149,088 806 (6) 149,888 — 149,888 — Subtotal 374,968 1,160 (28) 376,100 10,996 326,978 38,126 Total assets measured at fair value $ 435,768 $ 1,163 $ (28) $ 436,903 $ 41,900 $ 345,632 $ 49,371

LEASES

LEASES	6 Months Ended
	Jun. 30, 2020
Leases [Abstract]
LEASES	LEASES The Company accounts for leases under ASU No. 2016-02, Leases (Topic 842) , adopted as of January 1, 2019. In July 2014, the Company entered into a five-year noncancelable operating lease for its offices and laboratory space in South San Francisco, California that was scheduled to expire in June 2019, with an option for the Company to extend the lease for an additional three years. In August 2017, the Company entered into an amendment which extended the existing operating lease to June 2021 and added 13,258 square feet of additional lease space resulting in a total of 26,987 square feet being leased in the aggregate under the amended lease. In November 2017, the Company entered into a second amendment which reduced the common areas resulting in a total of 26,897 square feet being leased in aggregate under the second amendment. On August 14, 2019, the Company entered into a third amendment to the existing operating lease which will extend the leased space by an additional 19,177 square feet, or Second Expansion Premises, which will result in a total of 46,074 square feet being leased in aggregate. The operating lease for the Second Expansion Premises will commence on the date they are delivered to the Company, which is expected to be September 1, 2020, or the Second Expansion Premises Commencement Date. In conjunction with the third amendment, the Company also agreed to lease 5,569 square feet of temporary office space effective August 15, 2019 to the Second Expansion Premises Commencement Date. The third amendment will extend the lease by 84 months from the Second Expansion Premises Commencement Date, with an option to extend the lease for an additional 36 months subject to certain conditions. The Company determined that the Second Expansion Premises shall be accounted for as a new lease at the Second Expansion Premises Commencement Date. Further, the Company determined that the amendment to the existing operating lease and temporary office space shall be accounted as a lease modification upon execution of the third amendment. The Company recognized an operating lease ROU asset of $8.1 million and operating lease liability of $8.1 million on its condensed balance sheet upon the execution of the third amendment on August 14, 2019, and will measure and record an additional ROU asset and operating lease liability for the Second Expansion Premises upon the Second Expansion Premises Commencement Date. Operating lease cost was $0.4 million and $0.3 million for the three months ended June 30, 2020 and 2019, respectively, and $0.9 million and $0.5 million for the six months ended June 30, 2020 and 2019, respectively. Variable lease cost was $0.1 million and $0.2 million for the three months ended June 30, 2020 and 2019, respectively, and $0.3 million and $0.4 million for the six months ended June 30, 2020 and 2019, respectively. Operating cash flows for both the six months ended June 30, 2020 and 2019 included $0.5 million in cash payments for operating leases. Expenses related to short-term leases were not significant for the three and six months ended June 30, 2020 and 2019. The following table presents the maturity analysis of the Company's operating lease liabilities showing the aggregate lease payments as of June 30, 2020. (in thousands) June 30, 2020 (remaining six months) 562 2021 1,377 2022 1,662 2023 1,712 2024 1,763 2025 and thereafter 4,959 Total lease payments (1) 12,035 Less: imputed interest (2,432) Total operating lease liabilities $ 9,603 (1) As noted above, the operating lease for the Second Expansion Premises is expected to commence on September 1, 2020 and therefore the lease related to the Second Expansion Premises is not recognized on the condensed balance sheet as of June 30, 2020. As of June 30, 2020, future minimum lease payments related to the Second Expansion Premises are expected to be $8.2 million over the lease term of 7.0 years. Operating lease liabilities are based on the net present value of the remaining lease payments over the remaining lease term. In determining the present value of lease payments, the Company uses its incremental borrowing rate. The weighted-average incremental borrowing rate used to determine the operating lease liabilities was 6.0% as of June 30, 2020 and December 31, 2019. The Company's weighted-average remaining lease term was 7.2 years and 7.7 years as of June 30, 2020 and December 31, 2019, respectively.

OTHER BALANCE SHEET COMPONENTS

OTHER BALANCE SHEET COMPONENTS	6 Months Ended
	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
OTHER BALANCE SHEET COMPONENTS	OTHER BALANCE SHEET COMPONENTS Property and Equipment, Net The following table presents the components of property and equipment, net as of June 30, 2020 and December 31, 2019. (in thousands) June 30, December 31, Furniture and fixtures $ 273 $ 265 Computer and lab equipment 3,037 3,867 Leasehold improvements 1,244 1,244 4,554 5,376 Less: accumulated depreciation and amortization (3,122) (2,648) Total property and equipment, net $ 1,432 $ 2,728 Depreciation and amortization expense was approximately $0.2 million for both the three months ended June 30, 2020 and 2019, and $0.5 million and $0.3 million for the six months ended June 30, 2020 and 2019, respectively. Accrued Expenses and Other Current Liabilities The following table presents the components of accrued expenses and other current liabilities as of June 30, 2020 and December 31, 2019. (in thousands) June 30, December 31, Accrued clinical and nonclinical study costs $ 4,189 $ 8,343 Accrued contract manufacturing 5,004 17,343 Accrued compensation 5,202 3,367 Accrued professional fees and other 6,374 3,727 Total accrued expenses and other current liabilities $ 20,769 $ 32,780

BORROWINGS

BORROWINGS	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
BORROWINGS	BORROWINGS Term Loan On February 28, 2018, the Company entered into the Term Loan with Hercules. The Term Loan provided for a loan in an aggregate principal amount of up to $100.0 million to be funded in five tranches subject to certain performance-based milestones. The first tranche, in the amount of $25.0 million, was funded on the closing date of the Term Loan. On October 15, 2018, the Company and Hercules entered into the second amendment to the Term Loan, which amended certain terms of the Term Loan. After giving effect to the second amendment, the Term Loan continued to provide for a loan in an aggregate principal amount of up to $100.0 million to be funded in five tranches subject to certain performance-based milestones. The second tranche was reduced from $25.0 million to $15.0 million and was funded on December 28, 2018. The Company accounted for the second amendment as a modification to the existing Term Loan. On March 27, 2019, the Company modified the Term Loan with Hercules by entering into the third amendment to the Term Loan. After giving effect to the third amendment, the amount available under the Term Loan was increased from up to $100.0 million to up to $200.0 million to be funded in tranches, subject to certain performance-based milestones, and the maturity of the Term Loan was extended. Under the terms of the Term Loan, as amended by the third amendment, the $40.0 million of principal outstanding under the Term Loan at the date of modification remained outstanding, and additional tranches of $20.0 million and $15.0 million were available for draw down prior to December 15, 2019 and December 15, 2020, respectively. An additional tranche of $75.0 million was to be available for draw down between January 1, 2020 and December 15, 2020, on the condition that the Company obtains final approval from the U.S. Food and Drug Administration, or FDA, of the New Drug Application, or NDA, for veverimer. A final tranche of $50.0 million will be available for draw down on or prior to December 15, 2021, upon request by the Company and the approval of Hercules' investment committee. The Company accounted for the third amendment as a modification to the existing Term Loan. On December 13, 2019, the third tranche of the Term Loan was funded in the amount of $20.0 million. On March 31, 2020, the Company and Hercules entered into the fourth amendment to the Term Loan. After giving effect to the fourth amendment, the fourth tranche of amount $15.0 million previously under Hercules Capital, Inc. was split between two lenders, $5.0 million under Hercules Capital, Inc. and $10.0 million under Hercules Technology III, L.P. The Company accounted for the fourth amendment as a modification to the existing Term Loan. On May 18, 2020, the Company and Hercules entered into the fifth amendment to the Term Loan. After giving effect to the fifth amendment, the additional tranche of $75.0 million was split into two separate tranches of $25.0 million and $50.0 million. The $25.0 million tranche will be available for draw down between January 1, 2020 and December 15, 2020, on the condition that the Company obtains final approval from the FDA of the NDA for veverimer on or before December 15, 2020. The $50.0 million tranche will be available for draw down between January 1, 2021 and June 30, 2021, on the condition that the $25.0 million tranche has been drawn and final approval has been received for the NDA for veverimer on or before December 15, 2020. A final tranche of $50.0 million will be available for draw down on or prior to December 15, 2021, upon request by the Company and the approval of Hercules' investment committee. The fifth amendment also permits the issuance by the Company of certain convertible notes and cash payments to redeem or settle such convertible notes in accordance with the terms thereof. Such cash settlement or redemption is subject to a requirement that the Company maintain unrestricted cash in an amount not less than 100% of the outstanding obligations under the Term Loan from and after any such cash settlement or redemption, and that there be no default or event of default under the Term Loan at the time of such cash settlement or redemption. The fifth amendment also provides for an extension of the maturity date of the Term Loan from April 1, 2023, to April 1, 2024 if the $25.0 million tranche is drawn down. The Company accounted for the fifth amendment as a modification to the existing Term Loan. On May 19, 2020, the fourth tranche of the Term Loan was funded in the amount of $15.0 million. The Term Loan bears interest at a floating per annum interest rate equal to the greater of either (i) 8.35% or (ii) the lesser of (x) 8.35% plus the prime rate as reported in The Wall Street Journal minus 6.00% and (y) 9.85%. The maturity date is April 1, 2023 and may be extended to April 1, 2024 if the tranche of $25.0 million described above is drawn. The Company will initially be making interest-only payments until April 1, 2021. If the Company achieves certain performance milestones, including that the Company obtains final approval from the FDA of the NDA for veverimer on or before December 15, 2020, and financial covenants, the interest-only period could be extended for up to an additional 24 months. Upon expiration of the interest-only period, the Company will repay the Term Loan in equal monthly installments comprised of principal and interest, based on a 30-month amortization schedule, through maturity. The Company will pay an additional amount of (a) $2.6 million due on March 1, 2022 and (b) the product of 7.55% and the aggregate loans funded under the Term Loan due at maturity or on any earlier date on which the loans become due. If the Company prepays the Term Loan, the Company will be required to pay a prepayment charge equal to (i) 2.00% of the amount being prepaid at any time during the first 12 months following the effective date of the third amendment (ii) 1.50% of the amount being prepaid after 12 months but prior to 24 months following the effective date of the third amendment (iii) 1.00% of the amount being prepaid after 24 months but prior to 36 months following the effective date of the third amendment and (iv) zero if prepaid any time after 36 months following the effective date of the third amendment but prior to the maturity. The Term Loan is secured by substantially all of the Company's assets, except its intellectual property, which is the subject of a negative pledge; however, the collateral does consist of rights to payments and proceeds from the sale, licensing or disposition of all or any part of, or rights in, its intellectual property. Under the Term Loan, the Company is subject to certain covenants, including but not limited to requirements to deliver financial reports at designated times of the year and maintain a minimum level of cash. These covenants also limit or restrict the Company's ability to incur additional indebtedness or liens, acquire, own or make any investments, pay cash dividends, repurchase stock or enter into certain corporate transactions, including mergers and changes of control. Warrants In conjunction with the Term Loan entered into on February 28, 2018, the Company issued a warrant to Hercules to purchase 53,458 shares of its common stock with an exercise price of $9.35 per share. The estimated fair value of the warrant at the date of issuance was approximately $0.2 million. The fair value of the common stock warrant liability was determined using the probability-weighted expected return method. It was recorded at its fair value at inception and was remeasured at each financial reporting period with any changes in fair value being recognized as a component of other income (expense), net in the accompanying condensed statements of operations and comprehensive loss. On April 10, 2018, the Company entered into amendments with Hercules that resulted in the reclassification of the warrant liability to stockholders' equity as the amended terms of the warrants qualified for them to be accounted for as equity instruments and, as such, were no longer subject to remeasurement. The fair value of the common stock warrants of approximately $0.2 million was reclassified to stockholders' equity upon execution of the amendment. In connection with the funding of the second tranche on December 28, 2018, the Company issued to Hercules a warrant to purchase 53,458 shares of its common stock at an exercise price of $9.35 per share. The common stock warrant was recorded in stockholders' equity at its fair value of approximately $0.9 million on December 28, 2018. In conjunction with the third amendment, the Company issued warrants to Hercules to purchase 16,721 shares of its common stock with an exercise price of $23.92 per share. The common stock warrants were recorded in stockholders' equity at their fair value of approximately $0.3 million on March 27, 2019. The fair value of the common stock warrants was determined using an option-pricing model with the following assumptions: time to liquidity of 7.0 years, volatility of 75.0%, risk-free rate of 2.3% and stock price based on the March 27, 2019 closing price of the Company's common stock reported by The Nasdaq Global Select Market. In connection with the funding of the third tranche on December 13, 2019, the Company issued to Hercules a warrant to purchase 8,361 shares of its common stock at an exercise price of $23.92 per share. The common stock warrant was recorded in stockholders' equity at its fair value of approximately $0.3 million on December 13, 2019. The fair value of the common stock warrants were determined using an option-pricing model with the following assumptions: time to liquidity of 7.0 years, volatility of 72.7%, risk-free rate of 1.8% and stock price based on the December 13, 2019 closing price of the Company's common stock reported by The Nasdaq Global Select Market. In connection with the funding of the fourth tranche on May 19, 2020, the Company issued Hercules and Hercules Technology III, L.P. warrants to purchase a total of 6,270 shares of its common stock at an exercise price of $23.92 per share. The common stock warrant was recorded in stockholders' equity at its fair value of approximately $0.1 million on May 19, 2020. The fair value of the common stock warrants was determined using an option-pricing model with the following assumptions: time to liquidity of 7.0 years, volatility of 69.9%, risk-free rate of 0.5% and stock price based on the May 19, 2020 closing price of the Company's common stock reported by The Nasdaq Global Select Market. In connection with each subsequent draw down under the tranches described above, the Company is obligated to issue additional warrants to purchase a number of shares of the Company's common stock determined by dividing (x) an amount equal to 1.0% of the principal amount of the applicable tranche by (y) $23.92 subject to adjustments following certain corporate events. Embedded Derivatives and Other Debt Issuance Costs The Company determined that certain loan features were embedded derivatives requiring bifurcation and separate accounting. Those embedded derivatives were bundled together as a single, compound embedded derivative and then bifurcated and accounted for separately from the host contract. The Company initially recorded a compound derivative liability of $0.7 million, which is required to be marked to market in future periods. As of June 30, 2020, the Company calculated the fair values of the compound derivative using the “with and without” method under the income approach by computing the difference between the fair value of the Term Loan with the compound derivative, and the fair value of the Term Loan without the compound derivative. The Company calculated the fair values using a probability-weighted discounted cash flow analysis. The key valuation assumptions used consist of the discount rate of 8.4% and the probability of the occurrence of certain events of 20.0%. The compound derivative liability is being remeasured at each financial reporting period with any changes in fair value being recognized as a component of other income (expense), net in the condensed statements of operations and comprehensive loss. The fair value of the compound derivative liability was approximately $0.3 million as of June 30, 2020 and was classified as other long-term liabilities on the condensed balance sheet. The facility fee, fair value of warrants at issuance, fair value of embedded derivatives which were bifurcated, and other debt issuance costs have been treated as debt discounts on the Company’s condensed balance sheet and together with the additional payment are being amortized to interest expense throughout the life of the Term Loan using the effective interest rate method. As of June 30, 2020 and December 31, 2019, there were unamortized issuance costs and debt discounts of $3.0 million and $3.6 million, respectively, which were recorded as a direct deduction from the Term Loan on the condensed balance sheets. The following table presents future payments of principal and interest on the Term Loan as of June 30, 2020. (in thousands) June 30, 2020 (remaining six months) $ 3,183 2021 26,574 2022 33,344 2023 24,867 87,968 Less: amount representing interest (12,968) Present value of Term Loan 75,000 Less: current portion (6,784) Long-term portion of Term Loan $ 68,216 Convertible Senior Notes On May 22, 2020, the Company issued $200.0 million aggregate principal amount of 3.50% convertible senior notes due 2027, or Convertible Senior Notes, pursuant to an indenture, dated as of May 22, 2020, or the Indenture, between the Company and U.S. Bank National Association, as trustee, or the Trustee. The offering and sale of the Convertible Senior Notes were made by the Company to the initial purchasers in reliance on the exemption from registration provided by Section 4(a)(2) of the Securities Act of 1933, as amended, or the Securities Act, for resale by the initial purchasers to qualified institutional buyers (as defined in the Securities Act) pursuant to the exemption from registration provided by Rule 144A under the Securities Act. The issuance includes the exercise in full by the initial purchasers of their option to purchase an additional $25.0 million aggregate principal amount of Convertible Senior Notes. Net proceeds from the offering were $193.3 million after deducting underwriting discounts and commissions and other offering costs of approximately $6.7 million. The Convertible Senior Notes are senior unsecured obligations of the Company, and interest is payable semi-annually in arrears on May 15 and November 15 of each year, beginning on November 15, 2020. The Convertible Senior Notes mature on May 15, 2027, unless earlier repurchased, redeemed or converted and are not redeemable prior to May 20, 2024. The Company may redeem for cash all or any portion of the Convertible Senior Notes, at the Company’s option, on or after May 20, 2024 and on or before the 40th scheduled trading day immediately prior to the maturity date, if the last reported sale price of the Company’s common stock has been at least 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive), including the trading day immediately preceding the date on which the Company provides notice of redemption, during any 30 consecutive trading day period ending on, and including, the trading day immediately preceding the date on which the Company provides notice of redemption at a redemption price equal to 100% of the principal amount of the Convertible Senior Notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date. The Company is not required to and no sinking fund is provided for the Convertible Senior Notes. The Convertible Senior Notes are convertible into cash, shares of the Company’s common stock or a combination of cash and shares of the Company’s common stock at the Company’s election at an initial conversion rate of 30.0978 shares of the Company’s common stock per $1,000 principal amount of the Convertible Senior Notes, which is equivalent to an initial conversion price of approximately $33.23 per share of the Company’s common stock. The conversion rate is subject to customary adjustments for certain events as described in the Indenture. It is the Company’s current intent to settle conversions through combination settlement, which involves repayment of the principal portion in cash and any excess of the conversion value over the principal amount in shares of its common stock. As of June 30, 2020, the “if-converted value” did not exceed the remaining principal amount of the Convertible Senior Notes. Holders may convert their Convertible Senior Notes, at their option, prior to the close of business on the business day immediately preceding February 15, 2027, only under the following circumstances: • during any fiscal quarter commencing after the calendar quarter ending on September 30, 2020, if the last reported sale price of the Company’s common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day; • during the five consecutive business day period immediately following any ten consecutive trading day period, or the Measurement Period, in which the trading price per $1,000 principal amount of the Convertible Senior Notes, as determined following a request by a holder of notes in accordance with certain procedures described in the Indenture, for each trading day of the Measurement Period was less than 98% of the product of the last reported sales price of the Company’s common stock and the conversion rate on each such trading day; • upon the occurrence of certain corporate events or distributions of the Company’s common stock, as described in the Indenture; • after the Company’s issuance of a notice of redemption; or • at any time from, and including, February 15, 2027 until the close of business on the trading day immediately before the maturity date. If the Company undergoes a fundamental change, as described in the Indenture, subject to certain conditions, holders may require the Company to repurchase for cash all or any portion of their Convertible Senior Notes. The fundamental change repurchase price is equal to 100% of the principal amount of the Convertible Senior Notes to be repurchased, plus accrued and unpaid interest up to, but excluding, the fundamental change repurchase date. In addition, following certain corporate events that occur prior to the maturity date or if the Company delivers a notice of redemption, the Company will increase, in certain circumstances, the conversion rate for a holder who elects to convert its Convertible Senior Notes in connection with such a corporate event or notice of redemption, as the case may be. The Convertible Senior Notes are the Company’s senior unsecured obligations and rank senior in right of payment to any of the Company's indebtedness that is expressly subordinated in right of payment to the Convertible Senior Notes; equal in right of payment to any of the Company's unsecured indebtedness that is not so subordinated; effectively subordinated in right of payment to any of the Company’s secured indebtedness, including secured indebtedness under the Term Loan, to the extent of the value of the assets securing such indebtedness; and structurally subordinated to all indebtedness and other liabilities (including trade payables) of the Company’s future subsidiaries, if any. The Indenture contains customary events of default with respect to the Convertible Senior Notes and provides that upon certain events of default occurring and continuing, the trustee may, and the trustee at the request of holders of at least 25% in principal amount of the Convertible Senior Notes shall declare all principal and accrued and unpaid interest, if any, of the Convertible Senior Notes to be due and payable. In case of certain events of bankruptcy, insolvency or reorganization, involving the Company or a significant subsidiary, all of the principal of and accrued and unpaid interest on the Convertible Senior Notes will automatically become due and payable. At issuance, the Convertible Senior Notes were bifurcated into liability and equity components and accounted for separately. The carrying amount of the liability component was calculated to be $117.7 million by measuring the fair value of similar debt instruments that do not have an associated convertible feature. The carrying amount of the equity component, representing the conversion option, was determined by deducting the fair value of the liability component from the par value of the Convertible Senior Notes. The carrying amount of the equity component was calculated to be $82.3 million and was recorded in additional paid-in capital. The equity component is not remeasured as long as it continues to meet the conditions for equity classification. The allocation of proceeds into the equity component resulted in a debt discount for the Convertible Senior Notes that is amortized to interest expense at an effective interest rate of 13.5% over the effective life of the Convertible Senior Notes of 7.0 years, using the effective interest method. Underwriter discounts and issuance costs of $6.7 million were allocated to the liability and equity components based on the proportion of proceeds allocated to the debt and equity components. Underwriter discounts and issuance costs allocated to the liability component were $4.0 million and are amortized to interest expense over the term of the Convertible Senior Notes using the effective interest method. Underwriter discounts and issuance costs attributable to the equity component were $2.7 million and are netted against the equity component in additional paid-in capital.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	6 Months Ended
	Jun. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES The Company has contractual obligations from its operating lease, manufacturing and service contracts, Term Loan and tenant improvement loan, and other research and development activities. The following table aggregates the Company’s material expected contractual obligations and commitments as of June 30, 2020. June 30, 2020 (in thousands) Total 2020 (5) 2021 - 2022 2023 - 2024 Thereafter Term Loan (1) $ 96,250 $ 3,183 $ 62,538 $ 30,529 $ — Convertible Senior Notes (2) 248,864 3,364 14,000 14,000 217,500 Lease obligations (3) 20,229 764 5,018 5,953 8,494 Tenant improvement loan 93 47 46 — — Manufacturing and service contracts (4) 557,770 23,652 81,310 113,202 339,606 Total contractual obligations and commitments $ 923,206 $ 31,010 $ 162,912 $ 163,684 $ 565,600 (1) Comprised of amounts due under the fifth amendment to the Term Loan executed on May 18, 2020. (2) Comprised of interest payable and principal repayment due under the Convertible Senior Notes' Indenture. (3) Comprised of the rent payments on our existing lease and on the Second Expansion Premises which will commence on September 2020 under our amended lease that was executed on August 14, 2019. (4) The purchase obligations are comprised of our non-cancelable purchase commitments under our Manufacturing and Commercial Supply Agreement with Patheon. These amounts are based on forecasts that may include estimates of our future market demand, quantity discounts and manufacturing efficiencies. (5) Remaining six months. Facilities The Company has an operating lease for its offices and laboratory space in South San Francisco. See Note 4. "Leases" for additional information about this lease. Other Commitments On October 4, 2019, the Company and Patheon Austria GmbH & Co KG, or Patheon, entered into a multi-year Manufacturing and Commercial Supply Agreement, or the Supply Agreement, under which Patheon agreed to manufacture and supply veverimer to support the Company's commercialization efforts. Patheon has also agreed to manufacture and supply veverimer to support the Company’s drug development and clinical trial activities. Under the Supply Agreement, the Company is obligated to make certain purchases of API. The Company and Patheon are also parties to a Master Development/Validation Services and Clinical/Launch Supply Agreement, or the MDA, pursuant to which Patheon agreed to manufacture and supply veverimer. Certain manufacturing activities previously governed by the MDA are now subject to the Supply Agreement, whereas other ongoing manufacturing activities under the MDA will continue to be governed by the MDA until such activities are complete. The Supply Agreement may be terminated by either party following an uncured material breach by the other party, in the event the other party becomes insolvent or subject to bankruptcy proceedings, or in connection with a force majeure event that continues beyond 12 months. In addition, the Supply Agreement may be terminated by the Company upon the occurrence of certain regulatory events or actions, including: (i) if the Company does not obtain regulatory approval for veverimer by a specified date or (ii) if the Company terminates its commercialization of veverimer or fails to launch veverimer by a specified date. The Company’s obligation to purchase veverimer is subject to minimum and maximum annual commitments, with the minimum commitments subject to modest reduction in certain circumstances. Patheon has agreed to make facility improvements under the Supply Agreement and will be the exclusive owner of the purchased equipment and facility improvements. Patheon may manufacture other products with the facility improvements when not occupied by manufacturing veverimer. Under the Supply Agreement, the Company has agreed to reimburse Patheon up to a specified amount for plant modifications. These payments will be expensed to research and development prior to FDA approval of veverimer. The Company also enters into other contracts in the normal course of business with contract research organizations, contract development and manufacturing organizations and other service providers and vendors. These contracts generally provide for termination on short notice and are cancelable contracts and accordingly, are not included in the contractual obligations and disclosures summarized above. Contingencies While there are no material legal proceedings the Company is aware of, the Company may become party to various claims and complaints arising in the ordinary course of business. The Company does not believe that any ultimate liability resulting from any of these claims will have a material adverse effect on its results of operations, financial position, or liquidity. However, the Company cannot give any assurance regarding the ultimate outcome of these claims, and their resolution could be material to operating results for any particular period, depending upon the level of income for the period. Guarantees and Indemnifications The Company indemnifies each of its directors and officers for certain events or occurrences, subject to certain limits, while the director is or was serving at the Company’s 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 a director may be subject to any proceeding arising out of acts or omissions of such director in such capacity. The maximum amount of potential future indemnification is unlimited; however, the Company currently holds director and officer liability insurance. This insurance allows the transfer of risk associated with the Company’s exposure and may enable it to recover a portion of any future amounts paid. The Company believes that the fair value of these indemnification obligations is minimal. Accordingly, it has not recognized any liabilities relating to these obligations for any period presented.

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
STOCKHOLDERS' EQUITY	STOCKHOLDERS' EQUITY On July 2, 2018, the Company’s amended and restated certificate of incorporation became effective, authorizing the Company to issue a total of 440,000,000 shares of all classes of capital stock, consisting of 400,000,000 shares of common stock, par value $0.001 per share, and 40,000,000 shares of preferred stock, par value $0.001 per share. As of June 30, 2020 and December 31, 2019, the Company had 50,039,587 and 49,763,176 shares of common stock outstanding, respectively. As of June 30, 2020, and December 31, 2019, the Company had no shares of preferred stock outstanding. Common Stock On April 8, 2019, the Company consummated an underwritten public offering and issued 6,440,000 shares of common stock, which included the exercise in full by the underwriters of their option to purchase 840,000 additional shares of common stock at an offering price of $36.00 per share for net proceeds of approximately $217.9 million, after deducting underwriting discounts and commissions of $13.9 million. Common stock reserved for future issuance as of June 30, 2020 and December 31, 2019, consisted of the following. June 30, December 31, Stock options and RSUs issued and outstanding 9,557,072 6,809,257 Stock options, RSUs and ESPP shares authorized for future issuance 2,719,321 3,257,316 Total 12,276,393 10,066,573

NET LOSS PER SHARE

NET LOSS PER SHARE	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
NET LOSS PER SHARE	NET LOSS PER SHARE The following table sets forth the computation of the basic and diluted net loss per share attributable to common stockholders for the three and six months ended June 30, 2020 and 2019. Three Months Ended Six Months Ended (In thousands, except share and per share amounts) 2020 2019 2020 2019 Numerator: Net loss $ (58,170) $ (36,626) $ (132,284) $ (74,523) Denominator: Weighted-average common shares outstanding 49,963,026 48,684,744 49,904,323 45,501,818 Less: weighted-average shares subject to repurchase (2,954) (10,506) (3,584) (11,957) Weighted-average number of shares used in basic and diluted net loss per share 49,960,072 48,674,238 49,900,739 45,489,861 Net loss per share, basic and diluted $ (1.16) $ (0.75) $ (2.65) $ (1.64) Since the Company was in a loss position for all periods presented, basic net loss per share is the same as diluted net loss per share for all periods as the inclusion of all potential common shares outstanding would have been anti-dilutive. The following weighted-average outstanding common stock equivalents were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been antidilutive. June 30, 2020 2019 Warrants to purchase common stock 138,268 123,637 Assumed conversion of Convertible Senior Notes 6,019,560 — Common stock subject to repurchase 2,520 8,707 Options and RSUs issued and outstanding 9,557,072 6,723,332 Total potential common shares excluded from the computation of diluted net loss per share 15,717,420 6,855,676

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	6 Months Ended
	Jun. 30, 2020
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTSOn July 14, 2020, the Company received a notification from the FDA stating that, as part of its ongoing review of the Company’s NDA, the FDA has identified deficiencies that preclude discussion of labeling and postmarketing requirements/commitments at this time. The FDA stated that the notification does not reflect a final decision on the information under review. The notification does not specify the deficiencies identified by the FDA.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation —The accompanying unaudited condensed financial statements have been prepared in accordance with accounting principles generally accepted in the United States, or U.S. GAAP, for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. The condensed balance sheet as of June 30, 2020, the condensed statements of operations and comprehensive loss for the three and six months ended June 30, 2020 and 2019, the condensed statements of stockholders' equity for the three and six months ended June 30, 2020 and 2019 and the condensed statements of cash flows for the six months ended June 30, 2020 and 2019 are unaudited, but include all adjustments, consisting only of normal recurring adjustments, which the Company considers necessary for a fair presentation of the financial position, operating results and cash flows for the periods presented. The condensed balance sheet at December 31, 2019 has been derived from audited financial statements.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Adopted Standards Effective January 1, 2020, the Company adopted ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which changed the impairment model for most financial assets and certain other instruments. The Company adopted ASU 2016-13 on January 1, 2020, using a modified retrospective transition method, which requires a cumulative-effect adjustment, if any, to the opening balance of retained earnings to be recognized on the date of adoption with prior periods not restated. The adoption of ASU 2016-13 did not have a significant impact on the Company's condensed financial statements. See "Credit Losses" above for a description of the Company's credit losses accounting policy. Standards Not Yet Effective

FAIR VALUE MEASUREMENTS AND F_2

FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIALINSTRUMENTS (Tables)	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Cash and financial assets remeasured on a recurring basis by hierarchy	The following tables set forth the value of the Company's financial assets remeasured on a recurring basis based on the three-tier fair value hierarchy by significant investment category as of June 30, 2020 and December 31, 2019. June 30, 2020 Reported as: (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Cash and Cash Equivalents Short-Term Investments Long-Term Investments Cash $ 2,428 $ — $ — $ 2,428 $ 2,428 $ — $ — Level 1: Money market funds 28,476 — — 28,476 28,476 — — U.S. Treasury securities 29,896 3 — 29,899 — 18,654 11,245 Subtotal 58,372 3 — 58,375 28,476 18,654 11,245 Level 2: U.S. government agency securities 43,883 3 (11) 43,875 — 5,749 38,126 Commercial paper 181,997 351 (11) 182,337 10,996 171,341 — Corporate debt securities 149,088 806 (6) 149,888 — 149,888 — Subtotal 374,968 1,160 (28) 376,100 10,996 326,978 38,126 Total assets measured at fair value $ 435,768 $ 1,163 $ (28) $ 436,903 $ 41,900 $ 345,632 $ 49,371 December 31, 2019 Reported as: (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Cash and Cash Equivalents Short-Term Investments Long-Term Investments Cash $ 1,393 $ — $ — $ 1,393 $ 1,393 $ — $ — Level 1: Money market funds 17,181 — — 17,181 17,181 — — Level 2: U.S. government agency securities 40,741 6 (14) 40,733 — 19,990 20,743 Commercial paper 108,248 107 (2) 108,353 — 108,353 — Corporate debt securities 185,569 205 (20) 185,754 — 159,517 26,237 Asset-backed securities 1,561 3 — 1,564 — 1,564 — Subtotal 336,119 321 (36) 336,404 — 289,424 46,980 Total assets measured at fair value $ 354,693 $ 321 $ (36) $ 354,978 $ 18,574 $ 289,424 $ 46,980
Available-for-sale investment in a continuous unrealized loss position but not deemed OTTI	The following table summarizes the Company's available-for-sale investments that were in a continuous unrealized loss position but not deemed due to credit losses and therefore not required to be charged to earnings against the allowance for expected credit losses, as of June 30, 2020 and December 31, 2019. June 30, 2020 December 31, 2019 (in thousands) Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. Treasury securities $ 11,245 $ — $ — $ — U.S. government agency securities 27,125 (11) 24,235 (14) Commercial paper 69,920 (11) 5,426 (2) Corporate debt securities 8,494 (6) 38,668 (20) Total $ 116,784 $ (28) $ 68,329 $ (36)
Maturities of cash equivalents and available-for-sale investments	The following table summarizes the maturities of the Company’s cash equivalents (excluding money market funds) and available-for-sale investments, as of June 30, 2020. (in thousands) Amortized Cost Fair Value Mature in less than one year $ 355,483 $ 356,628 Mature in one to five years 49,381 49,371 Total $ 404,864 $ 405,999
Reconciliation of liabilities using Level 3 unobservable inputs	The following table presents a reconciliation of financial liabilities related to the compound derivative liability associated with the Term Loan measured at fair value on a recurring basis using Level 3 unobservable inputs for the six months ended June 30, 2020 and 2019. Six Months Ended June 30, 2020 2019 (in thousands) Compound Derivative Liability Compound Derivative Liability Fair value at beginning of period $ 977 $ 161 Change in fair value (650) 165 Fair value at end of period $ 327 $ 326
Significant fair value unobservable inputs	The following table presents information about significant unobservable inputs related to the Company's Level 3 financial liabilities as of June 30, 2020. June 30, 2020 (in thousands) Fair Value Valuation Technique Significant Unobservable Input Input Compound derivative liability $ 327 Discounted cash flow Discount rate 8.4 % Probability of the occurrence of certain events 20.0 %

LEASES (Tables)

LEASES (Tables)	6 Months Ended
	Jun. 30, 2020
Leases [Abstract]
Operating lease maturity schedule	The following table presents the maturity analysis of the Company's operating lease liabilities showing the aggregate lease payments as of June 30, 2020. (in thousands) June 30, 2020 (remaining six months) 562 2021 1,377 2022 1,662 2023 1,712 2024 1,763 2025 and thereafter 4,959 Total lease payments (1) 12,035 Less: imputed interest (2,432) Total operating lease liabilities $ 9,603 (1) As noted above, the operating lease for the Second Expansion Premises is expected to commence on September 1, 2020 and therefore the lease related to the Second Expansion Premises is not recognized on the condensed balance sheet as of June 30, 2020. As of June 30, 2020, future minimum lease payments related to the Second Expansion Premises are expected to be $8.2 million over the lease term of 7.0 years.

OTHER BALANCE SHEET COMPONENTS

OTHER BALANCE SHEET COMPONENTS (Tables)	6 Months Ended
	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Property and Equipment, Net	The following table presents the components of property and equipment, net as of June 30, 2020 and December 31, 2019. (in thousands) June 30, December 31, Furniture and fixtures $ 273 $ 265 Computer and lab equipment 3,037 3,867 Leasehold improvements 1,244 1,244 4,554 5,376 Less: accumulated depreciation and amortization (3,122) (2,648) Total property and equipment, net $ 1,432 $ 2,728
Schedule of Accrued Expenses and Other Current Liabilities	The following table presents the components of accrued expenses and other current liabilities as of June 30, 2020 and December 31, 2019. (in thousands) June 30, December 31, Accrued clinical and nonclinical study costs $ 4,189 $ 8,343 Accrued contract manufacturing 5,004 17,343 Accrued compensation 5,202 3,367 Accrued professional fees and other 6,374 3,727 Total accrued expenses and other current liabilities $ 20,769 $ 32,780

BORROWINGS (Tables)

BORROWINGS (Tables)	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
Schedule of Future Payments of Principal and Interest	The following table presents future payments of principal and interest on the Term Loan as of June 30, 2020. (in thousands) June 30, 2020 (remaining six months) $ 3,183 2021 26,574 2022 33,344 2023 24,867 87,968 Less: amount representing interest (12,968) Present value of Term Loan 75,000 Less: current portion (6,784) Long-term portion of Term Loan $ 68,216
Schedule of component carrying values of convertible senior notes	The following table presents the carrying amount of the liability and equity components of the Convertible Senior Notes as of June 30, 2020. (in thousands) June 30, Liability component: Principal $ 200,000 Unamortized discount - equity component (81,423) Unamortized underwriter discounts and issuance costs (3,932) Net carrying amount $ 114,645 Equity component, net of underwriter discounts and issuance costs $ 79,498
Schedule of interest expense on convertible debt	The following table presents the interest expense related to the Convertible Senior Notes for the three and six months ended June 30, 2020. (in thousands) Contractual interest expense $ 758 Amortization of debt discount 837 Amortization of underwriter discounts and issuance costs 22 Total interest expense $ 1,617

Commitment and Contingencies (T

Commitment and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Contractual Obligation, Fiscal Year Maturity	The following table aggregates the Company’s material expected contractual obligations and commitments as of June 30, 2020. June 30, 2020 (in thousands) Total 2020 (5) 2021 - 2022 2023 - 2024 Thereafter Term Loan (1) $ 96,250 $ 3,183 $ 62,538 $ 30,529 $ — Convertible Senior Notes (2) 248,864 3,364 14,000 14,000 217,500 Lease obligations (3) 20,229 764 5,018 5,953 8,494 Tenant improvement loan 93 47 46 — — Manufacturing and service contracts (4) 557,770 23,652 81,310 113,202 339,606 Total contractual obligations and commitments $ 923,206 $ 31,010 $ 162,912 $ 163,684 $ 565,600 (1) Comprised of amounts due under the fifth amendment to the Term Loan executed on May 18, 2020. (2) Comprised of interest payable and principal repayment due under the Convertible Senior Notes' Indenture. (3) Comprised of the rent payments on our existing lease and on the Second Expansion Premises which will commence on September 2020 under our amended lease that was executed on August 14, 2019. (4) The purchase obligations are comprised of our non-cancelable purchase commitments under our Manufacturing and Commercial Supply Agreement with Patheon. These amounts are based on forecasts that may include estimates of our future market demand, quantity discounts and manufacturing efficiencies. (5) Remaining six months.

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Schedule of Common Stock Reserved for Future Issuance	Common stock reserved for future issuance as of June 30, 2020 and December 31, 2019, consisted of the following. June 30, December 31, Stock options and RSUs issued and outstanding 9,557,072 6,809,257 Stock options, RSUs and ESPP shares authorized for future issuance 2,719,321 3,257,316 Total 12,276,393 10,066,573

NET LOSS PER SHARE (Tables)

NET LOSS PER SHARE (Tables)	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Basic and diluted net loss per share	The following table sets forth the computation of the basic and diluted net loss per share attributable to common stockholders for the three and six months ended June 30, 2020 and 2019. Three Months Ended Six Months Ended (In thousands, except share and per share amounts) 2020 2019 2020 2019 Numerator: Net loss $ (58,170) $ (36,626) $ (132,284) $ (74,523) Denominator: Weighted-average common shares outstanding 49,963,026 48,684,744 49,904,323 45,501,818 Less: weighted-average shares subject to repurchase (2,954) (10,506) (3,584) (11,957) Weighted-average number of shares used in basic and diluted net loss per share 49,960,072 48,674,238 49,900,739 45,489,861 Net loss per share, basic and diluted $ (1.16) $ (0.75) $ (2.65) $ (1.64)
Antidilutive securities excluded from computation	The following weighted-average outstanding common stock equivalents were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been antidilutive. June 30, 2020 2019 Warrants to purchase common stock 138,268 123,637 Assumed conversion of Convertible Senior Notes 6,019,560 — Common stock subject to repurchase 2,520 8,707 Options and RSUs issued and outstanding 9,557,072 6,723,332 Total potential common shares excluded from the computation of diluted net loss per share 15,717,420 6,855,676

FAIR VALUE MEASUREMENTS AND F_3

FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS - Marketable securities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Cash and Cash Equivalents	$ 41,900	$ 18,574
Level 2:
Short-term investments	345,632	289,424
Long-term investments	49,371	46,980
Fair Value, Measurements, Recurring
Total assets measured at fair value
Amortized Cost	435,768	354,693
Gross Unrealized Gains	1,163	321
Gross Unrealized Losses	(28)	(36)
Estimated Fair Value	436,903	354,978
Cash | Fair Value, Measurements, Recurring
Debt Securities, Available-for-sale [Line Items]
Cash and Cash Equivalents	2,428	1,393
Level 1:
Estimated Fair Value	2,428	1,393
Cash and Cash Equivalents | Fair Value, Measurements, Recurring
Debt Securities, Available-for-sale [Line Items]
Cash and Cash Equivalents	41,900	18,574
Cash and Cash Equivalents | Cash | Fair Value, Measurements, Recurring
Debt Securities, Available-for-sale [Line Items]
Cash and Cash Equivalents	2,428	1,393
Short-Term Investments | Fair Value, Measurements, Recurring
Level 2:
Short-term investments	345,632	289,424
Long-Term Investments | Fair Value, Measurements, Recurring
Level 2:
Long-term investments	49,371	46,980
Level 1: | Fair Value, Measurements, Recurring
Level 2:
Amortized Cost	58,372
Gross Unrealized Gains	3
Gross Unrealized Losses	0
Estimated Fair Value	58,375
Short-term investments	18,654
Long-term investments	11,245
Level 1: | Money market funds | Fair Value, Measurements, Recurring
Debt Securities, Available-for-sale [Line Items]
Cash and Cash Equivalents	28,476	17,181
Level 1:
Estimated Fair Value	28,476	17,181
Level 1: | U.S. Treasury securities | Fair Value, Measurements, Recurring
Level 2:
Amortized Cost	29,896
Gross Unrealized Gains	3
Gross Unrealized Losses	0
Estimated Fair Value	29,899
Short-term investments	18,654
Long-term investments	11,245
Level 1: | Cash and Cash Equivalents | Fair Value, Measurements, Recurring
Level 2:
Estimated Fair Value	28,476
Level 1: | Cash and Cash Equivalents | Money market funds | Fair Value, Measurements, Recurring
Debt Securities, Available-for-sale [Line Items]
Cash and Cash Equivalents	28,476	17,181
Level 1: | Cash and Cash Equivalents | U.S. Treasury securities | Fair Value, Measurements, Recurring
Level 2:
Estimated Fair Value	0
Level 2:
Level 2:
Gross Unrealized Losses	(28)	(36)
Level 2: | U.S. government agency securities
Level 2:
Gross Unrealized Losses	(11)	(14)
Level 2: | Commercial paper
Level 2:
Gross Unrealized Losses	(11)	(2)
Level 2: | Corporate debt securities
Level 2:
Gross Unrealized Losses	(6)	(20)
Level 2: | Fair Value, Measurements, Recurring
Level 2:
Amortized Cost	374,968	336,119
Gross Unrealized Gains	1,160	321
Gross Unrealized Losses	(28)	(36)
Estimated Fair Value	376,100	336,404
Level 2: | Fair Value, Measurements, Recurring | U.S. government agency securities
Level 2:
Amortized Cost	43,883	40,741
Gross Unrealized Gains	3	6
Gross Unrealized Losses	(11)	(14)
Estimated Fair Value	43,875	40,733
Level 2: | Fair Value, Measurements, Recurring | Commercial paper
Level 2:
Amortized Cost	181,997	108,248
Gross Unrealized Gains	351	107
Gross Unrealized Losses	(11)	(2)
Estimated Fair Value	182,337	108,353
Level 2: | Fair Value, Measurements, Recurring | Corporate debt securities
Level 2:
Amortized Cost	149,088	185,569
Gross Unrealized Gains	806	205
Gross Unrealized Losses	(6)	(20)
Estimated Fair Value	149,888	185,754
Level 2: | Fair Value, Measurements, Recurring | Asset-backed Securities
Level 2:
Amortized Cost		1,561
Gross Unrealized Gains		3
Gross Unrealized Losses		0
Estimated Fair Value		1,564
Level 2: | Cash and Cash Equivalents | Fair Value, Measurements, Recurring
Level 2:
Estimated Fair Value	10,996	0
Level 2: | Cash and Cash Equivalents | Fair Value, Measurements, Recurring | U.S. government agency securities
Level 2:
Estimated Fair Value	0	0
Level 2: | Cash and Cash Equivalents | Fair Value, Measurements, Recurring | Commercial paper
Level 2:
Estimated Fair Value	10,996	0
Level 2: | Cash and Cash Equivalents | Fair Value, Measurements, Recurring | Corporate debt securities
Level 2:
Estimated Fair Value	0	0
Level 2: | Cash and Cash Equivalents | Fair Value, Measurements, Recurring | Asset-backed Securities
Level 2:
Estimated Fair Value		0
Level 2: | Short-Term Investments | Fair Value, Measurements, Recurring
Level 2:
Short-term investments	326,978	289,424
Level 2: | Short-Term Investments | Fair Value, Measurements, Recurring | U.S. government agency securities
Level 2:
Short-term investments	5,749	19,990
Level 2: | Short-Term Investments | Fair Value, Measurements, Recurring | Commercial paper
Level 2:
Short-term investments	171,341	108,353
Level 2: | Short-Term Investments | Fair Value, Measurements, Recurring | Corporate debt securities
Level 2:
Short-term investments	149,888	159,517
Level 2: | Short-Term Investments | Fair Value, Measurements, Recurring | Asset-backed Securities
Level 2:
Short-term investments		1,564
Level 2: | Long-Term Investments | Fair Value, Measurements, Recurring
Level 2:
Long-term investments	38,126	46,980
Level 2: | Long-Term Investments | Fair Value, Measurements, Recurring | U.S. government agency securities
Level 2:
Long-term investments	38,126	20,743
Level 2: | Long-Term Investments | Fair Value, Measurements, Recurring | Commercial paper
Level 2:
Long-term investments	0	0
Level 2: | Long-Term Investments | Fair Value, Measurements, Recurring | Corporate debt securities
Level 2:
Long-term investments	$ 0	26,237
Level 2: | Long-Term Investments | Fair Value, Measurements, Recurring | Asset-backed Securities
Level 2:
Long-term investments		$ 0

FAIR VALUE MEASUREMENTS AND F_4

FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS - Additional information (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2020USD ($)position	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)position	Jun. 30, 2019USD ($)	Dec. 31, 2019position
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment interest income	$ 1,200,000	$ 2,700,000	$ 2,900,000	$ 4,200,000
Debt securities, available-for-sale, allowance for credit loss	$ 0		$ 0
Debt instruments held in continuous unrealized loss position | position	13		13		18
Discount rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input	0.084		0.084
Discount rate | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input	0.084		0.084
Probability of the occurrence of certain events
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input	0.200		0.200
Probability of the occurrence of certain events | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input	0.200		0.200
Term Loan | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, fair value	$ 82,000,000		$ 82,000,000
Convertible Senior Notes | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, fair value	$ 209,900,000		$ 209,900,000
Convertible Senior Notes | Discount rate | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input	0.107		0.107
Convertible Senior Notes | Volatility | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input	0.480		0.480

FAIR VALUE MEASUREMENTS AND F_5

FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS - Available-for-sale investments in continuous unrealized loss position not deemed to be OTTI (Details) - Level 2 - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 116,784	$ 68,329
Unrealized Losses	(28)	(36)
U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	11,245	0
Unrealized Losses	0	0
U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	27,125	24,235
Unrealized Losses	(11)	(14)
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	69,920	5,426
Unrealized Losses	(11)	(2)
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	8,494	38,668
Unrealized Losses	$ (6)	$ (20)

FAIR VALUE MEASUREMENTS AND F_6

FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS - Maturities of cash equivalents and available-for-sale investments (Details) $ in Thousands	Jun. 30, 2020USD ($)
Amortized Cost
Mature in less than one year	$ 355,483
Mature in one to five years	49,381
Total	404,864
Fair Value
Mature in less than one year	356,628
Mature in one to five years	49,371
Total	$ 405,999

FAIR VALUE MEASUREMENTS AND F_7

FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS - Reconciliation of liabilities measured using Level 3 (Details) - Fair Value, Inputs, Level 3 - Compound Derivative Liability - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value at beginning of period	$ 977	$ 161
Change in fair value	(650)	165
Fair value at end of period	$ 327	$ 326

FAIR VALUE MEASUREMENTS AND F_8

FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS - Significant unobservable inputs related to level 3 assets and liabilities (Details) $ in Thousands	Jun. 30, 2020USD ($)
Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative liability, measurement input	0.084
Probability of the occurrence of certain events
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative liability, measurement input	0.200
Fair Value, Inputs, Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Compound derivative liability	$ 327
Fair Value, Inputs, Level 3 | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative liability, measurement input	0.084
Fair Value, Inputs, Level 3 | Probability of the occurrence of certain events
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative liability, measurement input	0.200

LEASES - Information related to

LEASES - Information related to operating lease cost (Details) $ in Thousands	Aug. 14, 2019USD ($)ft²	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Sep. 01, 2020ft²	Dec. 31, 2019USD ($)	Aug. 15, 2019ft²	Nov. 30, 2017ft²	Aug. 31, 2017ft²	Jul. 31, 2014
Lessee, Lease, Description [Line Items]
Term of operating lease											5 years
Operating lease renewal term											3 years
Lease rentable area (in square feet) | ft²										26,987
Extension of square footage leased | ft²	19,177
Temporary office space square footage | ft²								5,569
Term of third lease amendment lease	84 months
Term of operating lease not yet commenced	36 months
Operating lease ROU asset		$ 8,734		$ 8,734			$ 9,376
Total operating lease liabilities		9,603		9,603
Operating lease, cost		400	$ 300	900	$ 500
Variable lease cost		$ 100	$ 200	300	400
Cash payments for operating leases				$ 500	$ 500
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member
Accounting Standards Update 2016-02
Lessee, Lease, Description [Line Items]
Operating lease ROU asset	$ 8,100
Total operating lease liabilities	$ 8,100
Amended Lease
Lessee, Lease, Description [Line Items]
Lease rentable area (in square feet) | ft²										13,258
Second Amendment To Lease
Lessee, Lease, Description [Line Items]
Lease rentable area (in square feet) | ft²									26,897
Forecast
Lessee, Lease, Description [Line Items]
Lease rentable area (in square feet) | ft²						46,074

LEASES - Operating lease schedu

LEASES - Operating lease schedule of maturity (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2020USD ($)
Leases [Abstract]
2020 (remaining six months)	$ 562
2021	1,377
2022	1,662
2023	1,712
2024	1,763
2025 and thereafter	4,959
Total lease payments	12,035
Less: imputed interest	(2,432)
Total operating lease liabilities	9,603
Future minimum payments of operating lease	$ 8,200
Term of operating lease not yet commenced, second expansion premises	7 years

LEASES - Supplemental balance s

LEASES - Supplemental balance sheet information regarding operating leases (Details)	Jun. 30, 2020	Dec. 31, 2019
Leases [Abstract]
Weighted average discount rate	6.00%	6.00%
Weighted average remaining lease term	7 years 2 months 12 days	7 years 8 months 12 days

OTHER BALANCE SHEET COMPONENT_2

OTHER BALANCE SHEET COMPONENTS - Property and equipment, net (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 4,554		$ 4,554		$ 5,376
Less: accumulated depreciation and amortization	(3,122)		(3,122)		(2,648)
Total property and equipment, net	1,432		1,432		2,728
Depreciation and amortization expense	200	$ 200	474	$ 341
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	273		273		265
Computer and lab equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,037		3,037		3,867
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,244		$ 1,244		$ 1,244

OTHER BALANCE SHEET COMPONENT_3

OTHER BALANCE SHEET COMPONENTS - Accrued expense and other current liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued clinical and nonclinical study costs	$ 4,189	$ 8,343
Accrued contract manufacturing	5,004	17,343
Accrued compensation	5,202	3,367
Accrued professional fees and other	6,374	3,727
Total accrued expenses and other current liabilities	$ 20,769	$ 32,780

BORROWINGS - Additional informa

BORROWINGS - Additional information (Details)

May 22, 2020USD ($)dayslender$ / sharesRate

Mar. 27, 2019USD ($)shares

Jun. 30, 2020USD ($)$ / shares

Jun. 30, 2019USD ($)

Sep. 30, 2019

May 19, 2020USD ($)$ / sharesshares

May 18, 2020USD ($)tranche

Mar. 31, 2020USD ($)lender

Dec. 31, 2019USD ($)

Dec. 13, 2019USD ($)$ / sharesshares

Dec. 28, 2018USD ($)$ / sharesshares

Oct. 15, 2018USD ($)tranche

Apr. 10, 2018USD ($)

Feb. 28, 2018USD ($)tranche$ / sharesshares

Debt Instrument [Line Items]

Long-term portion of Term Loan

$ 67,952,000

$ 58,374,000

Percentage of principal

1.00%

Net proceeds from issuance of convertible debt

$ 193,285,000

$ 0

Repurchase price after fundamental change (as a percent)

100.00%

Tranche four

Debt Instrument [Line Items]

Number of Lenders | lender

2

Term Loan

Debt Instrument [Line Items]

Debt aggregate principal amount

$ 100,000,000

$ 100,000,000

Debt, number of tranches | tranche

5

5

Long-term portion of Term Loan

$ 40,000,000

Debt payment terms, multiplier

7.55%

Number of shares called by warrant (in shares) | shares

53,458

Exercise price of warrant (in USD per share) | $ / shares

$ 9.35

Estimated fair value of warrants

$ 200,000

Increase (decrease) in equity due to warrants

$ 900,000

$ 200,000

Fair value of embedded derivative liability

300,000

$ 700,000

Unamortized underwriter discounts and issuance costs

$ 3,000,000

$ 3,600,000

Term Loan | Minimum

Debt Instrument [Line Items]

Debt prepayment fee, percentage

2.00%

Term Loan | Tranche one

Debt Instrument [Line Items]

Debt aggregate principal amount

25,000,000

Term Loan | Tranche two

Debt Instrument [Line Items]

Debt aggregate principal amount

$ 15,000,000

$ 25,000,000

Number of shares called by warrant (in shares) | shares

53,458

Exercise price of warrant (in USD per share) | $ / shares

$ 9.35

New Term Loan

Debt Instrument [Line Items]

Maximum borrowing capacity of term loan

$ 200,000,000

Term of principal and interest payments

30 months

One time payment of principal

$ 2,600,000

Debt prepayment fee, percentage year two

1.50%

Debt prepayment fee, percentage year three

1.00%

Debt prepayment fee, percentage after year three

0.00%

New Term Loan | Maximum

Debt Instrument [Line Items]

Extended period for payment of interest only

24 months

New Term Loan | Tranche one

Debt Instrument [Line Items]

Debt aggregate principal amount

$ 20,000,000

New Term Loan | Tranche four

Debt Instrument [Line Items]

Debt aggregate principal amount

$ 15,000,000

$ 15,000,000

New Term Loan | Tranche Five

Debt Instrument [Line Items]

Debt aggregate principal amount

$ 50,000,000

Debt covenant, percentage of unrestricted cash

100.00%

Third amendment to term loan

Debt Instrument [Line Items]

Number of shares called by warrant (in shares) | shares

16,721

6,270

8,361

Exercise price of warrant (in USD per share) | $ / shares

$ 23.92

$ 23.92

$ 23.92

Increase (decrease) in equity due to warrants

$ 300,000

$ 100,000

$ 300,000

Warrants measurement input

0.023

Fourth amendment to term loan | Tranche four | Hercules Capital, Inc.

Debt Instrument [Line Items]

Debt aggregate principal amount

5,000,000

Fourth amendment to term loan | Tranche four | Hercules Technology III, L.P.

Debt Instrument [Line Items]

Debt aggregate principal amount

$ 10,000,000

Fifth amendment to term loan | Tranche Five

Debt Instrument [Line Items]

Debt aggregate principal amount

$ 75,000,000

Debt, number of tranches | tranche

2

Fifth amendment to term loan | Tranche Six

Debt Instrument [Line Items]

Debt aggregate principal amount

$ 25,000,000

Fifth amendment to term loan | Tranche Seven

Debt Instrument [Line Items]

Debt aggregate principal amount

$ 50,000,000

Senior Notes | 3.50% Due 2027

Debt Instrument [Line Items]

Debt aggregate principal amount

$ 200,000,000

$ 200,000,000

Debt interest rate

0.035%

Unamortized underwriter discounts and issuance costs

(3,932,000)

Aggregate amount of additional purchase option

$ 25,000,000

Net proceeds from issuance of convertible debt

193,300,000

Underwriting discounts, commissions and other offering costs

$ 6,700,000

Percentage of principal

25.00%

Carrying amount of liability component

$ 117,700,000

114,645,000

Equity component, net of underwriter discounts and issuance costs

$ (82,300,000)

$ (79,498,000)

Effective interest rate

13.50%

Amortization period

7 years

6 years 10 months 24 days

Debt issuance costs allocated to liability component

$ (4,000,000)

Debt issuance costs allocated to equity component

$ 2,700,000

Senior Notes | 3.50% Due 2027 | Debt Instrument, Redemption, Period One

Debt Instrument [Line Items]

Number of trading days prior to maturity | days

40

Percentage of conversion price

130.00%

Number of trading days | lender

20

Number of consecutive trading days | lender

30

Redemption price percentage

100.00%

Conversion rate | Rate

3009.78%

Conversion price | $ / shares

$ 33.23

Senior Notes | 3.50% Due 2027 | Debt Instrument, Redemption, Period Two

Debt Instrument [Line Items]

Percentage of conversion price

130.00%

Number of trading days | lender

20

Number of consecutive trading days | lender

30

Redemption price percentage

98.00%

Number of consecutive business days | days

5

Consecutive trading days, measurement period | days

10

Debt Instrument, Convertible, Principal Amount Of Note

$ 1,000

Floating variable rate 1 | Term Loan

Debt Instrument [Line Items]

Debt interest rate

8.35%

Floating variable rate 2 | Term Loan | Prime rate

Debt Instrument [Line Items]

Debt, basis spread on variable rate

8.35%

Floating variable rate 2 | New Term Loan | Prime rate

Debt Instrument [Line Items]

Debt, basis spread on adjusted variable rate

6.00%

Floating variable rate 3 | Term Loan

Debt Instrument [Line Items]

Debt interest rate

9.85%

Time To Liquidity | Third amendment to term loan

Debt Instrument [Line Items]

Measurement input, time to liquidity

7 years

Volatility | Third amendment to term loan

Debt Instrument [Line Items]

Warrants measurement input

0.750

0.699

0.727

Risk-free interest rate | Third amendment to term loan

Debt Instrument [Line Items]

Warrants measurement input

0.005

0.018

Discount Rate

Debt Instrument [Line Items]

Derivative liability, measurement input

0.084

Measurement input, probability of occurrence of certain events

Debt Instrument [Line Items]

Derivative liability, measurement input

0.200

BORROWINGS - Debt maturity sche

BORROWINGS - Debt maturity schedule (Details) $ in Thousands	Jun. 30, 2020USD ($)
Debt Disclosure [Abstract]
2020 (remaining six months)	$ 3,183
2021	26,574
2022	33,344
2023	24,867
Long-term debt including interest payable	87,968
Less: amount representing interest	(12,968)
Present value of Term Loan	75,000
Less: current portion	(6,784)
Long-term portion of Term Loan	$ 68,216

BORROWINGS - Convertible Debt C

BORROWINGS - Convertible Debt Carrying Value (Details) - Senior Notes - 3.50% Due 2027 - USD ($) $ in Thousands	Jun. 30, 2020	May 22, 2020
Debt Instrument [Line Items]
Principal	$ 200,000	$ 200,000
Unamortized discount - equity component	(81,423)
Unamortized underwriter discounts and issuance costs	(3,932)
Net carrying amount	114,645	117,700
Equity component, net of underwriter discounts and issuance costs	$ 79,498	$ 82,300

BORROWINGS - Interest Expense (

BORROWINGS - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Debt Instrument [Line Items]
Total interest expense	$ 3,756	$ 1,391	$ 5,776	$ 2,780
Senior Notes | 3.50% Due 2027
Debt Instrument [Line Items]
Contractual interest expense			758
Amortization of debt discount			837
Amortization of underwriter discounts and issuance costs			22
Total interest expense			$ 1,617

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Details) $ in Thousands	Jun. 30, 2020USD ($)
Lease obligations
2020	$ 764
2021 - 2022	5,018
2023 - 2024	5,953
Thereafter	8,494
Manufacturing and service contracts
2020	23,652
2021 - 2022	81,310
2023 - 2024	113,202
Thereafter	339,606
Total contractual obligations and commitments
Total	923,206
2020	31,010
2021 - 2022	162,912
2023 - 2024	163,684
Thereafter	565,600
Term Loan
Term loan and tenant improvement loan
Total	96,250
2020	3,183
2021 - 2022	62,538
Long-term Debt, Maturing in Years Four and Five	30,529
Thereafter	0
Lease obligations
Total	20,229
Senior Notes
Total contractual obligations and commitments
Convertible Notes Payable	248,864
Convertible Notes Payable, Year One	3,364
Convertible Notes Payable, Maturity, Year Two	14,000
Convertible Notes Payable, Year Four And Five	14,000
Convertible Notes Payable, After Year Five	217,500
Tenant Improvement Loan
Term loan and tenant improvement loan
Total	93
2020	47
2021 - 2022	46
Long-term Debt, Maturing in Years Four and Five	0
Thereafter	0
Manufacturing and service contracts
Total	$ 557,770

STOCKHOLDERS' EQUITY - Addition

STOCKHOLDERS' EQUITY - Additional information (Details) - USD ($) $ / shares in Units, $ in Millions	Apr. 08, 2019	Jun. 30, 2020	Dec. 31, 2019	Jul. 02, 2018
Class of Stock [Line Items]
Total number of shares authorized for issue (in shares)				440,000,000
Common stock, shares authorized (in shares)		400,000,000	400,000,000	400,000,000
Common stock, par value (in USD per share)		$ 0.001	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)		40,000,000	40,000,000	40,000,000
Preferred stock, par value (in USD per share)		$ 0.001	$ 0.001	$ 0.001
Common stock, shares outstanding (in shares)		50,039,587	49,763,176
Preferred stock, outstanding (in shares)		0	0
Over-Allotment Option
Class of Stock [Line Items]
Number of common stock issued (in shares)	840,000
Underwritten Public Offering
Class of Stock [Line Items]
Number of common stock issued (in shares)	6,440,000
Share price (in USD per share)	$ 36
Proceeds from initial public offering, net of issuance costs	$ 217.9
Underwriting discounts and commissions	$ 13.9

STOCKHOLDERS' EQUITY - Common s

STOCKHOLDERS' EQUITY - Common stock (Details) - shares	Jun. 30, 2020	Dec. 31, 2019
Equity [Abstract]
Stock options and RSUs issued and outstanding (in shares)	9,557,072	6,809,257
Stock options, RSUs and ESPP shares authorized for future issuance (in shares)	2,719,321	3,257,316
Total (in shares)	12,276,393	10,066,573

NET LOSS PER SHARE - Basic and

NET LOSS PER SHARE - Basic and diluted net loss per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net loss	$ (58,170)	$ (74,114)	$ (36,626)	$ (37,897)	$ (132,284)	$ (74,523)
Denominator:
Weighted average common shares outstanding (in shares)	49,963,026		48,684,744		49,904,323	45,501,818
Less: weighted average shares subject to repurchase (in shares)	(2,954)		(10,506)		(3,584)	(11,957)
Weighted-average number of shares used in basic and diluted net loss per share (in shares)	49,960,072		48,674,238		49,900,739	45,489,861
Net loss per share, basic and diluted (in USD per share)	$ (1.16)		$ (0.75)		$ (2.65)	$ (1.64)

NET LOSS PER SHARE - Antidiluti

NET LOSS PER SHARE - Antidilutive securities (Details) - shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	15,717,420	6,855,676
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	138,268	123,637
Assumed conversion of Convertible Senior Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	6,019,560	0
Common stock subject to repurchase
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	2,520	8,707
Options and RSUs issued and outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	9,557,072	6,723,332