Tricida (TCDAQ) 10-K 2 Mar 20 2019 FY Annual report Financial data

Cover page

Cover page - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2019	Feb. 27, 2020	Jun. 28, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
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, Suite 201
Entity Address, Postal Zip Code	94080
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
City Area Code	415
Local Phone Number	429-7800
Title of 12(b) Security	Common stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
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		49,855,335
Documents Incorporated by Reference	Certain portions of the registrant's definitive proxy statement relating to the Company's Annual Meeting of Stockholders, to be filed with the Securities and Exchange Commission within 120 days of the registrant's fiscal year ended December 31, 2019, are incorporated by reference into Part III of this Annual Report on Form 10-K where indicated.
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Central Index Key	0001595585
Current Fiscal Year End Date	--12-31
Entity Public Float			$ 1.1
Trading Symbol	TCDA

BALANCE SHEETS

BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 18,574	$ 37,172
Short-term investments	289,424	203,906
Prepaid expenses and other current assets	4,744	3,269
Total current assets	312,742	244,347
Long-term investments	46,980	2,287
Property and equipment, net	2,728	1,215
Operating lease right-of-use assets	9,376
Total assets	371,826	247,849
Current liabilities:
Accounts payable	5,911	8,460
Current operating lease liabilities	1,072
Accrued expenses and other current liabilities	32,780	6,344
Total current liabilities	39,763	14,804
Liabilities, Noncurrent [Abstract]
Term Loan	58,374	38,071
Non-current operating lease liabilities	8,783
Other long-term liabilities	1,023	449
Total liabilities	107,943	53,324
Commitments and contingencies (Note 7)
Convertible preferred stock	0	0
Stockholders’ equity:
Preferred stock	0	0
Common stock	50	42
Additional paid-in capital	632,647	386,830
Accumulated other comprehensive income (loss)	193	(153)
Accumulated deficit	(369,007)	(192,194)
Total stockholders’ equity	263,883	194,525
Total liabilities and stockholders’ equity	$ 371,826	$ 247,849

CONDENSED BALANCE SHEETS (Paren

CONDENSED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
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 outstanding (in shares)	49,763,176	42,148,247
Common stock, shares issued (in shares)	49,763,176	42,148,247

STATEMENTS OF OPERATIONS AND CO

STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating expenses:
Research and development	$ 133,028	$ 85,594	$ 35,906
General and administrative	45,796	18,001	11,216
Total operating expenses	178,824	103,595	47,122
Loss from operations	(178,824)	(103,595)	(47,122)
Change in fair value—preferred stock tranche obligation	0	0	5,649
Other income (expense), net	7,663	3,924	183
Interest expense	(5,744)	(3,137)	0
Loss before income taxes	(176,905)	(102,808)	(41,290)
Income tax benefit	(92)	0	0
Net loss	(176,813)	(102,808)	(41,290)
Other comprehensive income (loss):
Net unrealized gain (loss) on available-for-sale-investments, net of tax	346	(140)	(13)
Total comprehensive loss	$ (176,467)	$ (102,948)	$ (41,303)
Net loss per share, basic and diluted (in USD per share)	$ (3.72)	$ (4.64)	$ (19.32)
Weighted-average number of shares outstanding, basic and diluted (in shares)	47,521,237	22,146,192	2,137,690

STATEMENTS OF CONVERTIBLE PREFE

STATEMENTS OF CONVERTIBLE PREFERRED SHARES AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Series C Preferred Stock	Series D Preferred Stock	Series A Preferred Stock	Common Stock	Additional Paid-in Capital	AOCI Attributable to Parent	Retained Earnings
Beginning balance (in shares) at Dec. 31, 2016	63,361,895
Beginning balance at Dec. 31, 2016	$ 66,883
Beginning balance (in shares) at Dec. 31, 2016					2,256,530
Beginning balance at Dec. 31, 2016	(47,628)				$ 2	$ 466	$ 0	$ (48,096)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of convertible preferred stock –subsequent closing, for cash, net of issuance cost and settlement of the preferred stock obligation (in shares)		16,274,192	24,493,615
Issuance of convertible preferred stock –subsequent closing, for cash, net of issuance cost and settlement of the preferred stock obligation		$ 22,882	$ 57,305
Issuance of common stock upon exercise of stock options (in shares)					16,079
Issuance of common stock upon exercise of stock options	14					14
Stock-based compensation	876					876
Net unrealized gain (loss) on available-for-sale-investments, net of tax	(13)						(13)
Net loss	$ (41,290)							(41,290)
Ending balance (in shares) at Dec. 31, 2017	104,129,702
Ending balance at Dec. 31, 2017	$ 147,070
Ending balance (in shares) at Dec. 31, 2017					2,272,609
Ending balance at Dec. 31, 2017	(88,041)				$ 2	1,356	(13)	(89,386)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	$ 5,152					5,152
Issuance of Series A warrant for cash (in shares)	95,936
Issuance of Series A convertible preferred stock upon exercise of warrant	$ 458
Conversion of convertible preferred shares to common stock (in shares)				(104,225,638)
Conversion of convertible preferred shares to common stock				$ (147,528)
Common stock issued in conversion of convertible preferred stock (in shares)					26,187,321
Conversion of convertible preferred stock to common stock	147,528				$ 26	147,502
Issuance of common stock in connection with initial public offering, net of underwriter discounts and issuance costs (in shares0					13,455,000
Issuance of common stock in connection with initial public offering, net of underwriter discounts and issuance costs	231,186				$ 13	231,173
Reclassification of common stock warrant liability to equity	194					194
Issuance of warrant in connection with Term Loan	884					884
Issuance of common stock upon exercise of stock options, warrants and employee stock purchase plan (in shares)					233,317
Issuance of common stock under equity incentive plans	570				$ 1	569
Net unrealized gain (loss) on available-for-sale-investments, net of tax	(140)						(140)
Net loss	$ (102,808)							(102,808)
Ending balance (in shares) at Dec. 31, 2018	0
Ending balance at Dec. 31, 2018	$ 0
Ending balance (in shares) at Dec. 31, 2018	42,148,247				42,148,247
Ending balance at Dec. 31, 2018	$ 194,525				$ 42	386,830	(153)	(192,194)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)	1,108,700
Issuance of common stock in connection with initial public offering, net of underwriter discounts and issuance costs (in shares0					6,440,000
Issuance of common stock in connection with initial public offering, net of underwriter discounts and issuance costs	$ 217,009				$ 6	217,003
Issuance of warrant in connection with Term Loan	535					535
Issuance of common stock under equity incentive plans (in shares)					1,174,929
Issuance of common stock under equity incentive plans	3,113				$ 2	3,111
Stock-based compensation	25,168					25,168
Net unrealized gain (loss) on available-for-sale-investments, net of tax	346						346
Net loss	$ (176,813)							(176,813)
Ending balance (in shares) at Dec. 31, 2019	0
Ending balance at Dec. 31, 2019	$ 0
Ending balance (in shares) at Dec. 31, 2019	49,763,176				49,763,176
Ending balance at Dec. 31, 2019	$ 263,883				$ 50	$ 632,647	$ 193	$ (369,007)

STATEMENTS OF CONVERTIBLE PRE_2

STATEMENTS OF CONVERTIBLE PREFERRED SHARES AND STOCKHOLDERS' EQUITY (DEFICIT) - (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)$ / shares
Series C Preferred Stock
Settlement of preferred stock obligation	$ 2,278
Preferred Stock | Series C Preferred Stock
Issued at | $ / shares	$ 1.55
Issuance costs	$ 65
Settlement of preferred stock obligation	$ 2,278
Preferred Stock | Series D Preferred Stock
Issued at | $ / shares	$ 2.35
Issuance costs	$ 255

STATEMENTS OF CASH FLOWS

STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities:
Net loss	$ (176,813)	$ (102,808)	$ (41,290)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	757	618	335
Amortization of operating lease right-of-use assets	964
Accretion (amortization) of premiums and discounts on investments	(3,698)	(1,094)	(42)
Amortization of Term Loan discount and issuance costs	2,173	1,316	0
Stock-based compensation	25,168	5,152	876
Changes in fair value of compound derivative liability and warrants	816	(188)	0
Changes in fair value of preferred stock tranche obligation	0	0	(5,649)
Other non-cash items	(92)	0	0
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(1,492)	(1,338)	(1,157)
Accounts payable	(2,621)	4,573	1,757
Accrued expenses and other liabilities	25,955	(1,087)	4,769
Operating lease liabilities	(707)
Net cash used in operating activities	(129,590)	(94,856)	(40,401)
Investing activities:
Purchase of investments	(497,492)	(233,928)	(76,846)
Maturities of investments	371,417	86,429	39,903
Purchase of property and equipment	(1,423)	(855)	(1,004)
Net cash used in investing activities	(127,498)	(148,354)	(37,947)
Financing activities:
Proceeds from equity offerings, net	217,930	237,750	0
Payments of offering costs	(921)	(6,564)	0
Proceeds from exercise of common stock under equity incentive plans	3,036	632	14
Proceeds from issuance of convertible preferred stock, net	0	85	82,465
Proceeds from leasehold improvement loan	0	276	0
Repayments of leasehold improvement loan	106	113	39
Proceeds (payments) under Term Loan, net	18,551	38,542	0
Net cash provided by financing activities	238,490	270,608	82,440
Net increase (decrease) in cash and cash equivalents	(18,598)	27,398	4,092
Cash and cash equivalents at beginning of year	37,172	9,774	5,682
Cash and cash equivalents at end of year	18,574	37,172	9,774
Supplemental disclosures
Cash paid for interest	3,348	1,612	0
Supplemental disclosures of non-cash investing and financing activities
Right-of-use assets obtained in exchange for lease obligations	8,084
Warrants and compound derivative liability related to Term Loan	535	1,693	0
Purchase of property and equipment in accounts payable and accrued expenses	820	27	0
Series C Preferred Stock
Supplemental disclosures of non-cash investing and financing activities
Series C fair value of preferred stock obligation upon closing	$ 0	$ 0	$ 2,278

ORGANIZATION AND BASIS OF PRESE

ORGANIZATION AND BASIS OF PRESENTATION	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGAINZATION 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 December 31, 2019, 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.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation — The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States (U.S. GAAP). Use of Estimates —The preparation of financial statements in conformity with U.S. GAAP requires the Company to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates. Cash and Cash Equivalents —All highly liquid investments with maturities at the date of purchase of three months or less are classified as cash equivalents. There are no restrictions on cash and cash equivalents. Investments —The Company's investments are in U.S. government securities, commercial paper, corporate debt securities and asset-backed securities. All investments with maturities of greater than three months at the date of purchase and maturities of less than one year at the reporting date are classified as short-term investments, while investments with maturities of a year or more at the reporting date are classified as long-term investments. The Company has classified its investments as available-for-sale in the accompanying financial statements. Available-for-sale investments are carried at fair value, with unrealized gains and losses reported as a component of accumulated other comprehensive income (loss). Realized gains and losses on the sale of all such securities are reported in other income (expense), net and are computed using the specific identification method. All of the Company's investments are subject to a periodic impairment review. The Company recognizes an impairment charge when a decline in the fair value of investments below the cost basis is judged to be other-than-temporary and would mark the security to market through a change to the statement of operations and comprehensive loss. In determining whether a decline in market value is other-than-temporary, various factors are considered, including the cause, duration of time and severity of the impairment, any adverse changes in the investees’ financial condition, and the Company’s intent and ability to hold the security for a period of time sufficient to allow for an anticipated recovery in market value. There were no investments deemed to be impaired as of December 31, 2019. Concentration of Credit Risk and Other Risks and Uncertainties —Financial instruments that potentially subject the Company to a concentration of credit risk, consist primarily of cash, cash equivalents, short-term and long-term investments. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. Management believes that these financial institutions are financially sound, and, accordingly, minimal credit risk exists with respect to those financial institutions. The Company is exposed to credit risk in the event of default by the financial institutions holding its cash, cash equivalents, short-term and long-term investments and by the issuers of the securities to the extent recorded in the balance sheet. The Company is dependent on third-party manufacturers to supply products for research and development activities in its programs and prepare for the commercial launch of veverimer. In particular, the Company relies and expects to continue to rely on a small number of manufacturers to supply it with its requirements for the active pharmaceutical ingredient and drug product related to these programs. These programs could be adversely affected by a significant interruption in the supply of active pharmaceutical ingredients and formulated drugs. Property and Equipment —Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is determined using the straight-line method over the estimated useful lives of the respective assets, which is three years. Leasehold improvements are amortized using the straight-line method over the shorter of the lease term or their estimated useful economic lives. Impairment of Long-Lived Assets —Long-lived assets consist of property and equipment. The Company assesses potential impairment losses on long-lived assets used in operations when events and circumstances indicate that assets might be impaired. If such events or changes in circumstances arise, the Company compares the carrying amount of the long-lived assets to the estimated future undiscounted cash flows expected to be generated by the long-lived assets. If the estimated aggregate undiscounted cash flows are less than the carrying amount of the long-lived assets, an impairment charge, calculated as the amount by which the carrying amount of the assets exceeds the fair value of the assets, is recorded. The fair value of the long-lived assets is determined based on the estimated discounted cash flows expected to be generated from the long-lived assets. The Company has not recognized any impairment losses in the years ended December 31, 2019, 2018 and 2017. Deferred Offering Costs —The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in the statements of convertible preferred stock and stockholders’ equity (deficit) as a reduction of additional paid-in capital generated as a result of the equity financing. Clinical and Manufacturing Accruals —The Company records accruals for the estimated costs of research, nonclinical and clinical studies and manufacturing development, which are a significant component of research and development expenses. A substantial portion of the Company’s ongoing research and development activities is conducted by third-party service providers, including clinical research organizations, or CROs, and contract manufacturing organizations, or CMOs. The Company’s contracts with CROs generally include pass-through fees such as regulatory expenses, investigator fees, travel costs and other miscellaneous costs, including shipping and printing fees. The financial terms of these contracts are subject to negotiations, which vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided to the Company under such contracts. The Company accrues the costs incurred under agreements with these third parties based on estimates of actual work completed in accordance with the respective agreements. The Company determines the estimated costs through the review of contracts and subsequent discussions with internal personnel and external service providers as to the progress or stage of completion of the services and the agreed-upon fees to be paid for such services. The Company makes significant judgments and estimates in determining the accrual balance in each reporting period. As actual costs become known, the Company adjusts its accruals. Although the Company does not expect its estimates to be materially different from amounts actually incurred, the Company’s understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and could result in the Company reporting amounts that are too high or too low in any particular period. The Company’s accrual is dependent, in part, upon the receipt of timely and accurate reporting from information provided as part of its clinical and nonclinical studies and other third-party vendors. For the three years ended December 31, 2019, 2018, and 2017, there have been no material differences from the Company’s accrued estimated expenses to the actual clinical trial and manufacturing expenses. However, variations in the assumptions used to estimate accruals, including, but not limited to the number of patients enrolled, the rate of patient enrollment, the actual services performed, and the amount of manufactured drug substance and/or drug product, and related costs may vary from the Company’s estimates, resulting in adjustments to research and development expense in future periods. Changes in these estimates that result in material changes to the Company’s accruals could materially affect its financial position and results of operations. Leases —The Company determines if an arrangement contains a lease at inception. For arrangements where the Company is the lessee, operating leases are included in operating lease right-of-use, or ROU, assets; current operating lease liabilities; and non-current operating lease liabilities on its balance sheets. The Company currently does not have any finance leases. Operating lease ROU assets and operating lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at the commencement date. ROU assets also include any initial direct costs incurred and any lease payments made on or before the lease commencement date, less lease incentives received. The Company uses its incremental borrowing rate based on the information available at the commencement date in determining the lease liabilities as the Company’s leases generally do not provide an implicit rate. The incremental borrowing rate is reevaluated upon a lease modification. The operating lease ROU asset also includes any initial direct costs and prepaid lease payments made less any lease incentives. The Company considered information available at the adoption date of Topic 842 to determine the incremental borrowing rate for leases in existence as of this date. Lease terms may include options to extend or terminate the lease when the Company is reasonably certain that the option will be exercised. Lease expense is recognized on a straight-line basis over the lease term. The Company elected to apply each of the practical expedients described in Accounting Standards Codification (ASC) Topic 842-10-65-1(f) which allow companies not to reassess: (i) whether any expired or existing agreements contain leases, (ii) the classification of any expired or existing leases, and (iii) the capitalization of initial direct costs for any existing leases. The Company also elected to apply the short-term lease measurement and recognition exemption in which ROU assets and lease liabilities are not recognized for short-term operating leases. A short-term is a lease that, at the commencement date, has a lease term of 12 months or less and does not include an option to purchase the underlying asset that the lessee is reasonably certain to exercise. Term Loan —The Company accounts for the Loan and Security Agreement, or Term Loan, with Hercules Capital, Inc., or Hercules, as a liability measured at net proceeds less debt discount and is accreted to the face value of the Term Loan over its expected term using the effective interest method. The Company considers whether there are any embedded features in its debt instruments that require bifurcation and separate accounting as derivative financial instruments pursuant to Accounting Standards Codification, or ASC, Topic 815, Derivatives and Hedging . Convertible Preferred Stock —The Company recorded all shares of convertible preferred stock at their respective fair values, net of issuance costs, on the dates of issuance. Upon the closing of the Initial Public Offering, or IPO, on July 2, 2018, the 104,225,638 shares of convertible preferred stock outstanding were automatically converted into 26,187,321 shares of common stock. Warrants —The Company issued freestanding warrants to purchase shares of common stock in connection with its Term Loan. The warrants are recorded at fair value using the Black-Scholes option pricing model. See Note 6 "Borrowings" to these financial statements for additional details. Preferred Stock Tranche Obligation —The Company entered into convertible preferred stock financings where, in addition to the initial closing, investors agreed to buy, and the Company agreed to sell, additional shares of that convertible preferred stock at a set price in the event that certain agreed milestones are achieved (a tranched financing). The Company evaluated this tranche obligation and determined that it met the definition of a freestanding instrument, and accordingly, determined the fair value of this obligation and recorded it on the balance sheet with the residual of the proceeds raised being allocated to convertible preferred stock. The preferred stock tranche obligation was revalued each reporting period with changes in the fair value of the obligation recorded as a component of other income (expense), net in the statements of operations and comprehensive loss. The preferred stock tranche obligation was revalued at settlement and the resultant fair value was then reclassified to convertible preferred stock at that time. Research and Development Expense —Research and development expense is charged to the statements of operations and comprehensive loss in the period in which they are incurred. Research and development expense consists primarily of salaries and related costs, including stock-based compensation expense, for personnel and consultants in our research and development functions; fees paid to clinical consultants, clinical trial sites and vendors, including CROs, costs related to pre-commercialization manufacturing activities including payments to CMOs and other vendors and consultants, costs related to regulatory activities, expenses related to lab supplies and services and depreciation and other allocated facility-related and overhead expenses. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are deferred and capitalized. The capitalized amounts are expensed as the related goods are delivered or the services are performed. Stock-Based Compensation —Stock-based compensation expense represents the grant-date fair value of awards recognized on a straight-line basis or by using an accelerated attribution method for awards with performance conditions over the employee's requisite service period (generally the vesting period). The Black-Scholes option-pricing model is used to calculate stock-based compensation expense for stock option awards and shares purchased under the Employee Stock Purchase Plan, or ESPP. For restricted stock units, or RSUs, the grant-date fair value is the closing price of the Company's common stock on the date of grant as reported on The Nasdaq Global Select Market. Because stock compensation expense is an estimate of awards ultimately expected to vest, it is reduced by an estimate for future forfeitures. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from estimates. The Company records the expense attributed to nonemployee services paid with stock option awards based on the estimated fair value of the awards determined using the Black-Scholes option pricing model. The measurement of stock-based compensation for nonemployees was previously subject to remeasurement as the options vested. As of July 1, 2018, the Company adopted ASU 2018-07, Improvements to Nonemployee Share-Based Payment Accounting , which no longer subjects nonemployee awards to remeasurement. The expense is recognized over the period during which services are received. Income Taxes —The Company accounts for income taxes using the liability method, whereby deferred tax asset and liability account balances are determined based on differences between the financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. The Company provides a valuation allowance when it is more likely than not that some portion or all of its deferred tax assets will not be realized. The Company accounts for income tax contingencies using a benefit recognition model. If it considers that a tax position is more likely than not to be sustained upon audit, based solely on the technical merits of the position, it recognizes the benefit. The Company measures the benefit by determining the amount that is greater than 50% likely of being realized upon settlement, presuming that the tax position is examined by the appropriate taxing authority that has full knowledge of all relevant information. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense or benefit. To date, there have been no interest or penalties charged in relation to the unrecognized tax benefits. Comprehensive Loss —Comprehensive loss is comprised of net loss and other comprehensive income (loss). Other comprehensive loss includes changes in stockholders’ equity (deficit) that are excluded from net loss, primarily unrealized gains or losses on the Company’s available-for-sale investments. These changes in stockholders' equity are reflected net of tax. Net Loss per Share —Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive given the net loss for each period presented. Segment Reporting —The Company manages its operations as a single operating segment for the purposes of assessing performance and making operating decisions. All of the Company's assets are maintained in the United States. Recent Accounting Pronouncements Adopted Standards In February 2016, the Financial Accounting Standards Board (FASB) issued Topic 842, which amended prior accounting standards for leases. The Company adopted Topic 842 on January 1, 2019, using the alternative modified transition method, which applies the standard as of the effective date and therefore, the Company has not applied the standard to the comparative periods presented on the Company's financial statements. The Company elected the following practical expedients when assessing the transition impact available to lessees: (i) not to reassess whether any expired or existing contracts as of January 1, 2019, are or contain leases; (ii) not to reassess the lease classification for any expired or existing leases as of January 1, 2019; and (iii) not to reassess initial direct costs for any existing leases as of January 1, 2019. As a lessee, the primary impact of the adoption of Topic 842 was the recognition of operating lease ROU assets of $2.3 million and operating lease liabilities of $2.5 million on its balance sheet as of January 1, 2019. See Note 4 "Leases" for additional details. Standards Not Yet Effective In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, or ASU 2016-13. ASU 2016-13 implements an impairment model, known as the current expected credit loss model, based on expected losses rather than incurred losses. Under the new guidance, an entity will recognize, as an allowance, its estimate of expected credit losses. The ASU is effective for interim and annual periods beginning after December 15, 2019, with early adoption permitted. The Company does not expect the adoption of ASU 2016-13 will have a significant impact on its financial statements. In September 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement, which amends ASC Topic 820, Fair Value Measurement and Disclosures, or ASU 2018-13. The FASB issued final guidance that eliminates, adds and modifies certain disclosure requirements for fair value measurements as part of its disclosure framework project. Under the ASU, entities will no longer be required to disclose the amount of transfers between Level 1 and Level 2 of the fair value hierarchy. Public companies will be required to disclose changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 fair value measurements held at the end of the reporting period and the range and weighted average used to develop significant unobservable inputs for Level 3 fair value measurements. ASU 2018-13 is effective for public business entities for annual reporting periods, and interim periods within those annual periods, beginning after December 15, 2019, with early adoption permitted. The Company plans to adopt this guidance on January 1, 2020. The Company does not expect the adoption of ASU 2018-13 will have a significant impact on its financial statements. 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	12 Months Ended
	Dec. 31, 2019
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 Topic 820 issued by the FASB. 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. The Company's policy is to recognize transfers in and out of Level 1, 2 and 3 as of the end of the reporting period. There were no transfers of assets or liabilities between the fair value measurement levels during the years ended December 31, 2019 and 2018. Our financial instruments consist primarily of cash and cash equivalents, short-term and long-term investments, accounts payable and the Term Loan with Hercules. Cash, cash equivalents and investments are reported at their respective fair values on Company's balance sheets. Where quoted prices are available in an active market, securities are classified as Level 1. The Company classifies money market funds 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 December 31, 2019 and 2018. December 31, 2019 Reported as: (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Cash and Cash Equivalents Short-term Investments Long-term investments Cash $ 1,393 $ — $ — $ 1,393 $ 1,393 $ — $ — Level 1: Money market fund 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 December 31, 2018 Reported as: (in thousands) Amortized cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Cash and Cash Equivalents Short-term Investments Long-term investments Cash $ 3,021 $ — $ — $ 3,021 $ 3,021 $ — $ — Level 1: Money market fund 33,154 — — 33,154 33,154 — — Level 2: Commercial paper 68,467 — (63) 68,404 997 67,407 — Corporate debt securities 89,038 4 (63) 88,979 — 86,692 2,287 Asset-backed securities 49,838 3 (34) 49,807 — 49,807 — Subtotal 207,343 7 (160) 207,190 997 203,906 2,287 Total assets measured at fair value $ 243,518 $ 7 $ (160) $ 243,365 $ 37,172 $ 203,906 $ 2,287 Interest income related to the Company's cash, cash equivalents and available-for-sale investments included in other income (expense), net was approximately $8.7 million, $3.5 million and $0.4 million for the years ended December 31, 2019, 2018 and 2017, respectively. There were no gross realized gains and gross realized losses for the years presented. The following table summarizes the Company's available-for-sale investments that were in a continuous unrealized loss position but were not deemed to be other-than-temporarily impaired, as of December 31, 2019 and 2018. December 31, 2019 December 31, 2018 (in thousands) Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. government agency securities $ 24,235 $ (14) $ — $ — Commercial paper 5,426 (2) 67,407 (63) Corporate debt securities 38,668 (20) 85,699 (63) Asset-backed securities — — 36,730 (34) Total $ 68,329 $ (36) $ 189,836 $ (160) The Company held a total of 18 and 48 positions which were in an unrealized loss position as of December 31, 2019 and 2018, respectively. All available-for-sale investments in an unrealized loss position were in a continuous loss position for less than 12 months. As of December 31, 2019, unrealized losses on available-for-sale investments were not attributable to credit risk. The Company determined that there were no other-than-temporary impairments as of December 31, 2019 and 2018 because the Company does not intend to sell these securities nor does the Company believe that it will be required to sell these securities before the recovery of their amortized cost basis. The following table summarizes the maturities of the Company’s cash equivalents (excluding money market funds) and available-for-sale investments, as of December 31, 2019. (in thousands) Amortized Cost Fair Value Mature in less than one year $ 289,156 $ 289,424 Mature in one to five years 46,963 46,980 Total $ 336,119 $ 336,404 The following table presents a reconciliation of financial liabilities measured at fair value on a recurring basis using Level 3 unobservable inputs for the years ended December 31, 2019 and 2018. 2019 2018 (in thousands) Compound Derivative Liability Compound Derivative Liability Warrant Fair value at beginning of year $ 161 $ — $ 106 Additions — 654 156 Change in fair value 816 (493) 305 Reclassification to equity — — (194) Issuance of convertible preferred stock on exercise of warrant — — (373) Fair value at end of year $ 977 $ 161 $ — The following table presents information about significant unobservable inputs related to the Company's Level 3 financial liabilities as of December 31, 2019. December 31, 2019 (in thousands) Fair Value Valuation Technique Significant Unobservable Input Input Compound derivative liability $977 Discounted cash flow Discount rate 10.7 % Probability of the occurrence of certain events 20.0 % Term Loan The estimated fair value of the Term Loan was $59.2 million and $37.8 million as of December 31, 2019 and 2018, respectively, and is classified as Level 3. The key valuation assumptions used to calculate the fair value of the Term Loan as of December 31, 2019 consist of the discount rate of 10.7% and the probability of occurrence of certain events of 20.0%.

LEASES

LEASES	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
LEASES	LEASES In July 2014, the Company entered into a five 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, and 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 (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 as of September 30, 2019. The Company recognized an operating lease ROU asset of $8.1 million and operating lease liability of $8.1 million on its 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 expense was $1.3 million, $1.0 million and $0.7 million for the years ended December 31, 2019, 2018 and 2017. Operating cash flows for the year ended December 31, 2019 included $1.1 million in cash payments for operating leases. Expense related to short-term leases was not significant for the year ended December 31, 2019. The following table presents the maturity analysis of the Company's operating lease liabilities showing the aggregate lease payments as of December 31, 2019. (in thousands) December 31, 2019 2020 $ 1,108 2021 1,377 2022 1,662 2023 and thereafter 8,434 Total lease payments (1) 12,581 Less: imputed interest (2,726) Total operating lease liabilities $ 9,855 (1) As noted above, the operating lease for the Second Expansion Premises will commence in fiscal year 2020 and therefore the lease related to the Second Expansion Premises is not recognized on the balance sheet as of December 31, 2019. As of December 31, 2019, 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 as of December 31, 2019 was 6.0%. The Company's weighted average remaining lease term was 7.7 years as of December 31, 2019. ASC Topic 840 Disclosures The Company elected the alternative modified transition method. The following table presents the future minimum lease commitments under the Company’s operating leases as of December 31, 2018 as previously disclosed under prior lease accounting standards. (in thousands) December 31, 2018 2019 $ 1,076 2020 1,108 2021 562 2022 and thereafter — Total future minimum lease payments $ 2,746

OTHER BALANCE SHEET COMPONENTS

OTHER BALANCE SHEET COMPONENTS	12 Months Ended
	Dec. 31, 2019
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 December 31, 2019 and 2018. (in thousands) December 31, 2019 December 31, 2018 Furniture and fixtures $ 265 $ 193 Computer and lab equipment 3,867 1,888 Leasehold improvements 1,244 1,055 5,376 3,136 Less: accumulated depreciation and amortization (2,648) (1,921) Total property and equipment, net $ 2,728 $ 1,215 Depreciation and amortization expense was approximately $0.8 million, $0.6 million and $0.3 million for the years ended December 31, 2019, 2018 and 2017, respectively. Accrued Expenses and Other Current Liabilities The following table presents the components of accrued expenses and other current liabilities as of December 31, 2019 and 2018. (in thousands) December 31, 2019 December 31, 2018 Accrued clinical and nonclinical study costs $ 8,343 $ 2,168 Accrued contract manufacturing 17,343 1,676 Accrued compensation 3,367 1,565 Accrued professional fees and other 3,727 935 Total accrued expenses and other current liabilities $ 32,780 $ 6,344

BORROWINGS

BORROWINGS	12 Months Ended
	Dec. 31, 2019
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 is increased from up to $100.0 million to up to $200.00 million to be funded in tranches, subject to certain performance-based milestones, and the maturity of the Term Loan is extended. Under the terms of the Term Loan, as amended by the third amendment, the $40.0 million principal outstanding under the Term Loan at the date of the modification remains outstanding, and additional tranches of $20.0 million and $15.0 million will be available for draw down prior to December 15, 2019 and December 15, 2020, respectively. An additional tranche of $75.0 million 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 U.S. Food and Drug Administration, or FDA, for 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. 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 extended to April 1, 2023 and may be extended to April 1, 2024 if the tranche of $75.0 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 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 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 (deficit) 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 (deficit) 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 (deficit) 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 (deficit) at their fair value of approximately $0.3 million on March 27, 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 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, or the issuance date, 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 (deficit) at its fair value of approximately $0.3 million on the issuance date. 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 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 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 December 31, 2019, 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 10.7% and the probability of the occurrence of certain events of 20%. 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 statements of operations and comprehensive loss. The fair value of the compound derivative liability was approximately $1.0 million and was classified as other long-term liabilities on the 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 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 December 31, 2019 and 2018, there were unamortized issuance costs and debt discounts of $3.6 million and $2.7 million, respectively, which were recorded as a direct deduction from the Term Loan on the balance sheets. The following table presents future payments of principal and interest on the Term Loan as of December 31, 2019. (in thousands) December 31, 2019 2020 $ 5,038 2021 21,259 2022 26,675 2023 19,893 72,865 Less: amount representing interest (12,865) Present value of Term Loan 60,000 Less: current portion — Long-term portion of Term Loan $ 60,000

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2019
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 December 31, 2019. December 31, 2019 (in thousands) Total Less than One Year One to Three Years Three to Five Years More than Five Years Term Loan (1) $ 72,865 $ 5,038 $ 47,934 $ 19,893 $ — Lease obligations (2) 20,774 1,309 5,018 5,953 8,494 Tenant improvement loan 140 93 47 — — Manufacturing and service contracts (3) 600,269 64,354 83,107 113,202 339,606 Total contractual obligations and commitments $ 694,048 $ 70,794 $ 136,106 $ 139,048 $ 348,100 (1) The long-term debt obligation is comprised of the Third Amended to the Loan and Security Agreement that was executed during March 2019. (2) These amounts are 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. (3) 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. Facilities On August 14, 2019, the Company extended the 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 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 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 legal proceedings the Company is aware of, the Company may become party to various claims and complaints arising in the ordinary course of business. Management 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, management 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 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	12 Months Ended
	Dec. 31, 2019
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 December 31, 2019 and 2018, the Company had 49,763,176 and 42,148,247 shares of common stock outstanding, respectively. As of December 31, 2019 and 2018, the Company had no shares of preferred stock outstanding. Common Stock On July 2, 2018, the Company completed its IPO and issued 13,455,000 shares of common stock at an offering price of $19.00 per share for net proceeds of approximately $237.7 million, after deducting underwriting discounts and commissions of $17.9 million. Upon the closing of the IPO, all of the 104,225,638 shares of convertible preferred stock outstanding were automatically converted on a 1:3.98 basis into 26,187,321 shares of 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 December 31, 2019 and 2018, consisted of the following. December 31, 2019 December 31, 2018 Stock options and RSUs issued and outstanding 6,809,257 4,599,307 Stock options, RSUs and ESPP shares authorized for future issuance 3,257,316 4,534,784 Total 10,066,573 9,134,091

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION Equity Incentive Plans During 2013, the Company adopted an equity compensation plan, the 2013 Equity Incentive Plan, or 2013 Plan, for eligible employees, officers, directors, advisors, and consultants. The 2013 Plan provided for the grant of incentive and non-statutory stock options. In June 2018, the Company's board of directors and stockholders approved the 2018 Equity Incentive Plan, or 2018 Plan. Any shares of common stock covered by awards granted under the 2013 Plan that terminated after June 22, 2018 by expiration, forfeiture, or cancellation were added to the 2018 Plan reserve and shares available for future issuance under the 2013 Plan were canceled. The initial number of shares of common stock available for issuance under the 2018 Plan was 4,000,000. Unless our board of directors provides otherwise, beginning on January 1, 2019 and continuing until the expiration of the 2018 Plan, the total number of shares of common stock available for issuance under the 2018 Plan will automatically increase annually on January 1 by the lesser of (i) 3,200,000 shares of Common Stock, (ii) 4% of the total number of issued and outstanding shares of common stock as of December 31 of the immediately preceding year and (iii) an amount determined by the board of directors. Under the 2018 Plan, any shares that are forfeited or expired are added back to the shares available for issuance. In the year ended December 31, 2019, the number of shares of common stock reserved for issuance under the 2018 Plan was increased by 1,685,929 shares. As of December 31, 2019, 2,098,380 shares of common stock were available for future issuance of options and restricted stock and other stock-based awards under the 2018 Plan. The terms of the stock option agreements, including vesting requirements, are determined by the board of directors, subject to the provisions of the plans. Options granted by the Company vest over a period of one four three The 2013 Plan and the 2018 Plan allow for early exercise where the option holders may exercise their options prior to vesting. Common stock that is issued upon the early exercise of options is subject to repurchase by the Company at the original exercise price at the option of the Company. As of December 31, 2019 and 2018, there were 5,040 shares and 20,193 shares, respectively, of common stock that were subject to repurchase with an aggregate purchase price of approximately $17 thousand and $89 thousand reflecting a weighted average price of $3.47 and $4.40 per share, respectively. The following table summarizes stock option activity under the plans for the year ended December 31, 2019. Shares Weighted- Weighted- Average Remaining Contractual Term (years) Aggregate Intrinsic Value (thousands) Balance at December 31, 2018 4,577,515 $ 5.99 8.0 $ 84,290 Granted 3,720,091 29.71 Exercised (1,108,700) 1.77 Forfeited or canceled (390,923) 28.29 Balance at December 31, 2019 6,797,983 $ 18.38 8.4 $ 133,892 Vested and expected to vest at December 31, 2019 6,471,442 $ 17.96 8.3 $ 129,998 All outstanding options can be early exercised. Beginning in the year ended December 31, 2018, the Company began to issue restricted stock units, or RSUs, to directors under the 2018 Plan. Awards granted to directors vest on the earlier of the one The following table summarizes RSU activity under the 2018 Plan for the year ended December 31, 2019. Shares Weighted- Unvested balance at December 31, 2018 21,792 $ 19.00 Granted 11,274 36.74 Vested (21,792) 19.00 Forfeited — Unvested balance at December 31, 2019 11,274 $ 36.74 The total vest date fair value of RSUs vested in the year ended December 31, 2019 was $0.8 million. There were no RSUs that vested during the years ended December 31, 2018 and 2017. Employee Stock Purchase Plan In June 2018, the Company's board of directors and stockholders approved the Tricida Inc. ESPP, or ESPP. The ESPP allows eligible employees to have up to 15.0% of their eligible compensation withheld and used to purchase common stock, subject to a maximum of $25,000 worth of stock purchased in a calendar year or no more than 2,500 shares in an offering period, whichever is less. An offering period consists of a six The initial number of shares of common stock available for issuance under the ESPP, was 800,000. Unless the Company's board of directors provides otherwise, beginning on January 1, 2019, the maximum number of shares which shall be made available for sale under the ESPP will automatically increase on the first trading day in January of each calendar year during the term of the ESPP by an amount equal to the lesser of (i) one percent (1.0%) of the total number of shares issued and outstanding on December 31 of the immediately preceding calendar year, (ii) 800,000 shares or (iii) an amount determined by the board of directors. In the year ended December 31, 2019, the number of shares of common stock reserved for issuance under the ESPP was increased by 421,482 shares. The Company issued 44,437 shares under the ESPP, representing approximately $1.1 million in employee contributions, for the year ended December 31, 2019. As of December 31, 2019, there were 1,158,936 shares of commons stock were available for future issuance under the ESPP. Performance Awards In August 2019, the Company granted 594,000 stock options under its 2018 Plan with a performance based milestone with graded vesting over 18 months. Compensation expense for the performance-based awards is recorded over the estimated service period when the performance conditions are deemed probable of achievement. For the year ended December 31, 2019, the stock compensation expense recorded during the period was for service-based awards and performance conditions deemed probable of achievement and/or achieved. Stock Option Valuation Assumptions As stock-based compensation recognized is based on options ultimately expected to vest, the expense has been reduced for estimated forfeitures. The Company uses the Black-Scholes option pricing model to determine the estimated fair value of stock options at the date of the grant. The Black-Scholes model includes inputs that require the input of subjective assumptions, including expected volatility, expected dividend yield, expected term, risk-free rate of return, and the estimated fair value of the underlying common stock on the date of grant. Expected Term: The expected term of the options represents the average period the stock options are expected to remain outstanding. As the Company does not have sufficient historical information to develop reasonable expectations about future exercise patterns and post-vesting employment termination behavior, the expected term of options granted is derived from the average midpoint between the weighted average vesting term and the contractual term, also known as the simplified method. Expected Volatility: Beginning in the fourth fiscal quarter of 2019, expected volatility is estimated using a weighted-average historical volatility for our common stock and the historical volatility of the common stock of a representative group of comparable publicly traded companies over a period equal to the expected term of the stock option grants. Prior to the fourth fiscal quarter of 2019, since the Company did not have sufficient trading history for its common stock, the expected volatility was based on the historical volatility of the common stock of comparable publicly traded companies. The Company selected companies with comparable characteristics, including enterprise value, risk profiles, position within the industry, and with historical share price information sufficient to meet the expected life of the Company's stock-based awards. Risk-Free Interest Rate: The risk-free interest rate is based on the yield of U.S. Treasury notes as of the grant date with terms commensurate with the expected term of the option. Expected Dividends: The expected dividends assumption is based on the Company’s expectation of not paying dividends in the foreseeable future. The fair value of the stock options granted to employees for the years ended December 31, 2019, 2018 and 2017 was calculated with the following assumptions. Years Ended December 31, 2019 2018 2017 Risk-free interest rate 2.1 % 2.7 % 1.7 % Expected volatility 73.6 % 64.6 % 72.7% - 78.5% Expected term (in years) 5.9 5.8 6.2 - 6.3 Expected dividends — % — % — % The fair value of the stock options granted to nonemployees for the years ended December 31, 2019, 2018 and 2017 was calculated with the following assumptions. Years Ended December 31, 2019 2018 2017 Risk-free interest rate 2.5 % 2.7 % 1.7% - 2.2% Expected volatility 76.4 % 68.4 % 70.8% - 73.1% Expected term (in years) 6.4 10.0 6.5 - 8.9 Expected dividends — % — % — % The following table summarizes the weighted-average fair value per share of stock options granted and the total intrinsic value of stock options exercised for the years ended December 31, 2019, 2018 and 2017. Years Ended December 31, (in thousands, except per share amounts) 2019 2018 2017 Stock options granted - weighted-average grant date fair value per share $ 19.28 $ 10.39 $ 1.67 Stock options exercised - intrinsic value 34,416 1,935 30 Stock-Based Compensation The following table presents stock-based compensation expense as reported in the Company’s statements of operations and comprehensive loss for the years ended December 31, 2019, 2018 and 2017. Years Ended December 31, (in thousands) 2019 2018 2017 Research and development $ 13,547 $ 2,643 $ 379 General and administrative 11,621 2,509 497 Total $ 25,168 $ 5,152 $ 876 The following table presents stock-based compensation expense by award type as reported in the Company’s statements of operations and comprehensive loss for the years ended December 31, 2019, 2018 and 2017. Years Ended December 31, (in thousands) 2019 2018 2017 Stock options $ 24,271 $ 4,806 $ 876 RSUs 447 202 — ESPP 450 144 — Total $ 25,168 $ 5,152 $ 876 As of December 31, 2019, there was approximately $54.6 million of unrecognized stock-based compensation associated with stock options which the Company expects to recognize over a weighted-average period of 2.6 years. As of December 31, 2019, there was approximately $0.2 million of unrecognized stock-based compensation associated with RSUs which the Company expects to recognize over a weighted-average period of 0.4 years.

NET LOSS PER SHARE

NET LOSS PER SHARE	12 Months Ended
	Dec. 31, 2019
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 years ended December 31, 2019, 2018 and 2017. Years Ended December 31, (In thousands, except share and per share amounts) 2019 2018 2017 Numerator: Net loss $ (176,813) $ (102,808) $ (41,290) Denominator: Weighted average common shares outstanding 47,530,174 22,158,354 2,267,732 Less: weighted average shares subject to repurchase (8,937) (12,162) (130,042) Weighted average number of shares used in basic and diluted net loss per share 47,521,237 22,146,192 2,137,690 Net loss per share, basic and diluted $ (3.72) $ (4.64) $ (19.32) 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. December 31, 2019 2018 2017 Series A convertible preferred stock — — 2,839,886 Series B convertible preferred stock — — 8,172,579 Series C convertible preferred stock — — 8,996,586 Series D convertible preferred stock — — 6,154,166 Warrants to purchase convertible preferred or common stock 131,998 106,916 24,104 Common stock subject to repurchase 5,040 20,193 366 Options and RSUs issued and outstanding 6,809,257 4,599,307 3,588,663 Total 6,946,295 4,726,416 29,776,350

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The Company recorded a tax benefit of $0.1 million during the year ended December 31, 2019 and did not record a provision or benefit for income taxes during the years ended December 31, 2018 and 2017. The significant components of the Company’s net deferred tax assets as of December 31, 2019 and 2018 are shown below. December 31, (in thousands) 2019 2018 Deferred tax assets Net operating loss carryforwards $ 82,252 $ 45,215 Research and development credits 8,968 4,090 Capitalized assets 79 23 Accruals and reserves 651 390 Operating lease liabilities 2,070 806 Stock-based compensation 4,250 — Gross deferred tax assets 98,270 50,524 Deferred tax liabilities Operating lease right-of-use assets (1,969) — Gross deferred tax liabilities (1,969) — Total net deferred tax assets 96,301 50,524 Less: valuation allowance (96,301) (50,524) Net deferred tax assets $ — $ — A valuation allowance is established when it is more likely than not that a deferred tax asset will not be realized. As of December 31, 2019 and 2018, the Company's valuation allowance was $96.3 million and $50.5 million, respectively. The valuation allowance increased by $45.8 million for the year ended December 31, 2019. The increase in the 2019 valuation allowance was primarily due to the addition of the 2019 net operating loss carryforwards. The following is a reconciliation between the U.S. federal income statutory tax rate and the Company’s effective tax rate for the years ended December 31, 2019, 2018 and 2017. Years Ended December 31, 2019 2018 2017 U.S. federal statutory rate 21.0 % 21.0 % 34.0 % State income taxes, net of federal benefit — — 5.8 Stock-based compensation 2.2 (0.2) (0.7) Permanent adjustments (0.1) (0.1) 4.2 Change to valuation allowance (25.9) (21.9) (19.6) Tax Cuts and Jobs Act Impact — — (25.4) Research and development credits 2.8 1.3 1.6 Net unrealized gain on available-for-sale investments 0.1 — — Other — (0.1) — Effective tax rate 0.1 % — % — % On December 22, 2017, the Tax Cut and Jobs Act, or Tax Act, was signed into law. Among other changes under the Tax Act was a permanent reduction in the federal corporate income tax rate from 35% to 21% effective January 1, 2018. As a result of the reduction in the corporate income tax rate, the Company revalued its net deferred tax assets at December 31, 2018, as the changes in tax law are accounted for in the period of enactment, resulting in a reduction in the value of our net deferred tax assets of approximately $10.5 million, offset by a $10.5 million change in valuation allowance as of that date. As of December 31, 2019, the Company had approximately $361.9 million of federal net operating losses available for future use. Federal net operating losses incurred prior to January 1, 2018 of approximately $89.1 million expire beginning in 2033 while federal net operating losses incurred after December 31, 2017 of approximately $272.8 million will have an indefinite carryforward period, subject to annual limitations. Federal research credits of approximately $8.0 million that are available for future use expire beginning in 2033. At December 31, 2019, the Company also had approximately $89.6 million of state net operating losses available for future use that expire beginning in 2033 and state research credits of approximately $4.2 million that have no expiration date. Utilization of the net operating loss carryforwards and the research and development credits carryforwards may be subject to a substantial annual limitation due to ownership change limitations that may have occurred or that could occur in the future, as required by Sections 382 and 383 of the Internal Revenue Code of 1986, or the Code, as amended, as well as similar state and foreign provisions. The Company has not completed a study to assess whether an ownership change has occurred or whether there have been multiple ownership changes since the Company’s formation due to the complexity and cost associated with such a study and the fact that there may be additional such ownership changes in the future. If the Company has experienced an ownership change at any time since its formation, utilization of the net operating loss or research credit carryforwards would be subject to an annual limitation under Section 382 of the Code. Such limitation is determined by first multiplying the value of the Company’s stock at the time of the ownership change by the applicable long-term and tax-exempt rate, and then could be subject to additional adjustments, as required. Any limitation may result in expiration of a portion of the net operating loss or research credit carryforwards before utilization. Further, until a study is completed, and any limitation known, no amounts are being considered as an uncertain tax position or disclosed as an unrecognized tax benefit. Due to the existence of the valuation allowance, future changes in the Company’s unrecognized tax benefits will not impact its effective tax rate. Any carryforwards that will expire prior to utilization as a result of such limitations will be removed from deferred tax assets with a corresponding reduction of the valuation allowance. ASC Topic 740-10 prescribes a comprehensive model for the recognition, measurement, presentation and disclosure in financial statements of any uncertain tax positions that have been taken or expected to be taken on a tax return. As of December 31, 2019 and 2018, the Company had unrecognized tax benefits of $2.5 million and $1.3 million, respectively. The amount of unrecognized tax benefits is not expected to significantly change over the next twelve months. No amounts, outside of valuation allowance, would impact the effective tax rate on continuing operations. The beginning and ending gross unrecognized tax benefits amounts are as follows. Years Ended December 31, (in thousands) 2019 2018 2017 Gross unrecognized tax benefits at beginning of year $ 1,297 $ 819 $ 574 Additions for tax positions related to prior year — — 2 Decrease related to prior year tax provisions — — (92) Additions for tax positions related to current year 1,246 478 335 Gross unrecognized tax benefits at end of year $ 2,543 $ 1,297 $ 819 It is the Company’s policy to include penalties and interest expense related to income taxes as a component of income tax expense as necessary. Management determined that no accrual for interest and penalties was required as of December 31, 2019. The Company’s tax jurisdictions are the United States and California. The Company’s tax years from 2013 to 2019 will remain open for examination by the federal and state authorities for three and four years respectively, from the date of utilization of any net operating loss or tax credits. The Company is not currently subject to income tax examinations by any authority.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	12 Months Ended
	Dec. 31, 2019
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS In August 2019, in accordance with the Federal Food, Drug, and Cosmetic Act, or the Act, the Company paid a fee of $2.6 million to the FDA under the Prescription Drug User Fee Act in conjunction with the filing of its NDA for veverimer. The Company filed a request with the FDA to grant a waiver and refund of the application fee under the small business waiver provision of the Act. Due to the uncertainty regarding the collectability of this refund, the Company recorded this filing fee as a research and development expense in the quarter ended September 30, 2019. In January 2020, the FDA granted the Company’s request for a waiver and refunded the application fee in February 2020. The refund will be recorded as a gain in research and development expense for the three months ending March 31, 2020.

SELECTED QUARTERLY FINANCIAL DA

SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED)	12 Months Ended
	Dec. 31, 2019
Condensed Financial Information Disclosure [Abstract]
SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED)	SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) The following presents certain unaudited quarterly financial information for the years ended December 31, 2019 and 2018. This information has been prepared on the same basis as the audited financial statements and includes all adjustments (consisting only of normal recurring adjustments) necessary to present fairly the unaudited quarterly results of operations set forth herein. Net loss per share for all periods presented has been retroactively adjusted to reflect the 1-for-3.98 reverse stock split effected on June 15, 2018. 2019 (in thousands, except per share data) Q1 Q2 Q3 Q4 Operating expenses $ 37,775 $ 37,837 $ 45,096 $ 58,116 Net loss (37,897) (36,626) (44,119) (58,171) Net loss per share, basic and diluted $ (0.90) $ (0.75) $ (0.89) $ (1.17) 2018 (in thousands, except per share data) Q1 Q2 Q3 Q4 Operating expenses $ 20,098 $ 25,279 $ 29,408 $ 28,810 Net loss (20,504) (25,362) (29,098) (27,844) Net loss per share, basic and diluted $ (9.00) $ (10.89) $ (0.71) $ (0.66)

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation — The accompanying financial statements have been prepared in accordance with accounting principles generally accepted in the United States (U.S. GAAP).
Use of Estimates	Use of Estimates —The preparation of financial statements in conformity with U.S. GAAP requires the Company to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents —All highly liquid investments with maturities at the date of purchase of three months or less are classified as cash equivalents. There are no restrictions on cash and cash equivalents.
Investments	Investments —The Company's investments are in U.S. government securities, commercial paper, corporate debt securities and asset-backed securities. All investments with maturities of greater than three months at the date of purchase and maturities of less than one year at the reporting date are classified as short-term investments, while investments with maturities of a year or more at the reporting date are classified as long-term investments. The Company has classified its investments as available-for-sale in the accompanying financial statements. Available-for-sale investments are carried at fair value, with unrealized gains and losses reported as a component of accumulated other comprehensive income (loss). Realized gains and losses on the sale of all such securities are reported in other income (expense), net and are computed using the specific identification method. All of the Company's investments are subject to a periodic impairment review. The Company recognizes an impairment charge when a decline in the fair value of investments below the cost basis is judged to be other-than-temporary and would mark the security to market through a change to the statement of operations and comprehensive loss. In determining whether a decline in market value is other-than-temporary, various factors are considered, including the cause, duration of time and severity of the impairment, any adverse changes in the investees’ financial condition, and the Company’s intent and ability to hold the security for a period of time sufficient to allow for an anticipated recovery in market value. There were no investments deemed to be impaired as of December 31, 2019.
Concentration of Credit Risk and Other Risks and Uncertainties	Concentration of Credit Risk and Other Risks and Uncertainties —Financial instruments that potentially subject the Company to a concentration of credit risk, consist primarily of cash, cash equivalents, short-term and long-term investments. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. Management believes that these financial institutions are financially sound, and, accordingly, minimal credit risk exists with respect to those financial institutions. The Company is exposed to credit risk in the event of default by the financial institutions holding its cash, cash equivalents, short-term and long-term investments and by the issuers of the securities to the extent recorded in the balance sheet. The Company is dependent on third-party manufacturers to supply products for research and development activities in its programs and prepare for the commercial launch of veverimer. In particular, the Company relies and expects to continue to rely on a small number of manufacturers to supply it with its requirements for the active pharmaceutical ingredient and drug product related to these programs. These programs could be adversely affected by a significant interruption in the supply of active pharmaceutical ingredients and formulated drugs.
Property and Equipment	Property and Equipment —Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is determined using the straight-line method over the estimated useful lives of the respective assets, which is three years. Leasehold improvements are amortized using the straight-line method over the shorter of the lease term or their estimated useful economic lives.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets—Long-lived assets consist of property and equipment. The Company assesses potential impairment losses on long-lived assets used in operations when events and circumstances indicate that assets might be impaired. If such events or changes in circumstances arise, the Company compares the carrying amount of the long-lived assets to the estimated future undiscounted cash flows expected to be generated by the long-lived assets. If the estimated aggregate undiscounted cash flows are less than the carrying amount of the long-lived assets, an impairment charge, calculated as the amount by which the carrying amount of the assets exceeds the fair value of the assets, is recorded. The fair value of the long-lived assets is determined based on the estimated discounted cash flows expected to be generated from the long-lived assets.
Deferred Offering Costs	Deferred Offering Costs—The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in the statements of convertible preferred stock and stockholders’ equity (deficit) as a reduction of additional paid-in capital generated as a result of the equity financing.
Clinical and Manufacturing Accruals	Clinical and Manufacturing Accruals —The Company records accruals for the estimated costs of research, nonclinical and clinical studies and manufacturing development, which are a significant component of research and development expenses. A substantial portion of the Company’s ongoing research and development activities is conducted by third-party service providers, including clinical research organizations, or CROs, and contract manufacturing organizations, or CMOs. The Company’s contracts with CROs generally include pass-through fees such as regulatory expenses, investigator fees, travel costs and other miscellaneous costs, including shipping and printing fees. The financial terms of these contracts are subject to negotiations, which vary from contract to contract and may result in payment flows that do not match the periods over which materials or services are provided to the Company under such contracts. The Company accrues the costs incurred under agreements with these third parties based on estimates of actual work completed in accordance with the respective agreements. The Company determines the estimated costs through the review of contracts and subsequent discussions with internal personnel and external service providers as to the progress or stage of completion of the services and the agreed-upon fees to be paid for such services. The Company makes significant judgments and estimates in determining the accrual balance in each reporting period. As actual costs become known, the Company adjusts its accruals. Although the Company does not expect its estimates to be materially different from amounts actually incurred, the Company’s understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and could result in the Company reporting amounts that are too high or too low in any particular period. The Company’s accrual is dependent, in part, upon the receipt of timely and accurate reporting from information provided as part of its clinical and nonclinical studies and other third-party vendors. For the three years ended December 31, 2019, 2018, and 2017, there have been no material differences from the Company’s accrued estimated expenses to the actual clinical trial and manufacturing expenses. However, variations in the assumptions used to estimate accruals, including, but not limited to the number of patients enrolled, the rate of patient enrollment, the actual services performed, and the amount of manufactured drug substance and/or drug product, and related costs may vary from the Company’s estimates, resulting in adjustments to research and development expense in future periods. Changes in these estimates that result in material changes to the Company’s accruals could materially affect its financial position and results of operations.
Lease	Leases —The Company determines if an arrangement contains a lease at inception. For arrangements where the Company is the lessee, operating leases are included in operating lease right-of-use, or ROU, assets; current operating lease liabilities; and non-current operating lease liabilities on its balance sheets. The Company currently does not have any finance leases. Operating lease ROU assets and operating lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at the commencement date. ROU assets also include any initial direct costs incurred and any lease payments made on or before the lease commencement date, less lease incentives received. The Company uses its incremental borrowing rate based on the information available at the commencement date in determining the lease liabilities as the Company’s leases generally do not provide an implicit rate. The incremental borrowing rate is reevaluated upon a lease modification. The operating lease ROU asset also includes any initial direct costs and prepaid lease payments made less any lease incentives. The Company considered information available at the adoption date of Topic 842 to determine the incremental borrowing rate for leases in existence as of this date. Lease terms may include options to extend or terminate the lease when the Company is reasonably certain that the option will be exercised. Lease expense is recognized on a straight-line basis over the lease term. The Company elected to apply each of the practical expedients described in Accounting Standards Codification (ASC) Topic 842-10-65-1(f) which allow companies not to reassess: (i) whether any expired or existing agreements contain leases, (ii) the classification of any expired or existing leases, and (iii) the capitalization of initial direct costs for any existing leases. The Company also elected to apply the short-term lease measurement and recognition exemption in which ROU assets and lease liabilities are not recognized for short-term operating leases. A short-term is a lease that, at the commencement date, has a lease term of 12 months or less and does not include an option to purchase the underlying asset that the lessee is reasonably certain to exercise.
Term Loan	Term Loan —The Company accounts for the Loan and Security Agreement, or Term Loan, with Hercules Capital, Inc., or Hercules, as a liability measured at net proceeds less debt discount and is accreted to the face value of the Term Loan over its expected term using the effective interest method. The Company considers whether there are any embedded features in its debt instruments that require bifurcation and separate accounting as derivative financial instruments pursuant to Accounting Standards Codification, or ASC, Topic 815, Derivatives and Hedging .
Convertible Preferred Stock	Convertible Preferred Stock—The Company recorded all shares of convertible preferred stock at their respective fair values, net of issuance costs, on the dates of issuance.
Warrants	Warrants —The Company issued freestanding warrants to purchase shares of common stock in connection with its Term Loan. The warrants are recorded at fair value using the Black-Scholes option pricing model. See Note 6 "Borrowings" to these financial statements for additional details.
Preferred Stock Tranche Obligation	Preferred Stock Tranche Obligation —The Company entered into convertible preferred stock financings where, in addition to the initial closing, investors agreed to buy, and the Company agreed to sell, additional shares of that convertible preferred stock at a set price in the event that certain agreed milestones are achieved (a tranched financing). The Company evaluated this tranche obligation and determined that it met the definition of a freestanding instrument, and accordingly, determined the fair value of this obligation and recorded it on the balance sheet with the residual of the proceeds raised being allocated to convertible preferred stock. The preferred stock tranche obligation was revalued each reporting period with changes in the fair value of the obligation recorded as a component of other income (expense), net in the statements of operations and comprehensive loss. The preferred stock tranche obligation was revalued at settlement and the resultant fair value was then reclassified to convertible preferred stock at that time.
Research and Development Expense	Research and Development Expense —Research and development expense is charged to the statements of operations and comprehensive loss in the period in which they are incurred. Research and development expense consists primarily of salaries and related costs, including stock-based compensation expense, for personnel and consultants in our research and development functions; fees paid to clinical consultants, clinical trial sites and vendors, including CROs, costs related to pre-commercialization manufacturing activities including payments to CMOs and other vendors and consultants, costs related to regulatory activities, expenses related to lab supplies and services and depreciation and other allocated facility-related and overhead expenses. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are
Stock-Based Compensation	Stock-Based Compensation —Stock-based compensation expense represents the grant-date fair value of awards recognized on a straight-line basis or by using an accelerated attribution method for awards with performance conditions over the employee's requisite service period (generally the vesting period). The Black-Scholes option-pricing model is used to calculate stock-based compensation expense for stock option awards and shares purchased under the Employee Stock Purchase Plan, or ESPP. For restricted stock units, or RSUs, the grant-date fair value is the closing price of the Company's common stock on the date of grant as reported on The Nasdaq Global Select Market. Because stock compensation expense is an estimate of awards ultimately expected to vest, it is reduced by an estimate for future forfeitures. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from estimates. The Company records the expense attributed to nonemployee services paid with stock option awards based on the estimated fair value of the awards determined using the Black-Scholes option pricing model. The measurement of stock-based compensation for nonemployees was previously subject to remeasurement as the options vested. As of July 1, 2018, the Company adopted ASU 2018-07, Improvements to Nonemployee Share-Based Payment Accounting , which no longer subjects nonemployee awards to remeasurement. The expense is recognized over the period during which services are received.
Income Taxes	Income Taxes —The Company accounts for income taxes using the liability method, whereby deferred tax asset and liability account balances are determined based on differences between the financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. The Company provides a valuation allowance when it is more likely than not that some portion or all of its deferred tax assets will not be realized.
Comprehensive Loss	Comprehensive Loss —Comprehensive loss is comprised of net loss and other comprehensive income (loss). Other comprehensive loss includes changes in stockholders’ equity (deficit) that are excluded from net loss, primarily unrealized gains or losses on the Company’s available-for-sale investments. These changes in stockholders' equity are reflected net of tax.
Net Loss per Share	Net Loss per Share —Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive given the net loss for each period presented.
Segment Reporting	Segment Reporting —The Company manages its operations as a single operating segment for the purposes of assessing performance and making operating decisions. All of the Company's assets are maintained in the United States.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Adopted Standards In February 2016, the Financial Accounting Standards Board (FASB) issued Topic 842, which amended prior accounting standards for leases. The Company adopted Topic 842 on January 1, 2019, using the alternative modified transition method, which applies the standard as of the effective date and therefore, the Company has not applied the standard to the comparative periods presented on the Company's financial statements. The Company elected the following practical expedients when assessing the transition impact available to lessees: (i) not to reassess whether any expired or existing contracts as of January 1, 2019, are or contain leases; (ii) not to reassess the lease classification for any expired or existing leases as of January 1, 2019; and (iii) not to reassess initial direct costs for any existing leases as of January 1, 2019. As a lessee, the primary impact of the adoption of Topic 842 was the recognition of operating lease ROU assets of $2.3 million and operating lease liabilities of $2.5 million on its balance sheet as of January 1, 2019. See Note 4 "Leases" for additional details. Standards Not Yet Effective In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, or ASU 2016-13. ASU 2016-13 implements an impairment model, known as the current expected credit loss model, based on expected losses rather than incurred losses. Under the new guidance, an entity will recognize, as an allowance, its estimate of expected credit losses. The ASU is effective for interim and annual periods beginning after December 15, 2019, with early adoption permitted. The Company does not expect the adoption of ASU 2016-13 will have a significant impact on its financial statements. In September 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement, which amends ASC Topic 820, Fair Value Measurement and Disclosures, or ASU 2018-13. The FASB issued final guidance that eliminates, adds and modifies certain disclosure requirements for fair value measurements as part of its disclosure framework project. Under the ASU, entities will no longer be required to disclose the amount of transfers between Level 1 and Level 2 of the fair value hierarchy. Public companies will be required to disclose changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 fair value measurements held at the end of the reporting period and the range and weighted average used to develop significant unobservable inputs for Level 3 fair value measurements. ASU 2018-13 is effective for public business entities for annual reporting periods, and interim periods within those annual periods, beginning after December 15, 2019, with early adoption permitted. The Company plans to adopt this guidance on January 1, 2020. The Company does not expect the adoption of ASU 2018-13 will have a significant impact on its financial statements. 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 F_2

FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Financial Assets and Liabilities Measured on a Recurring Basis	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 December 31, 2019 and 2018. December 31, 2019 Reported as: (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Cash and Cash Equivalents Short-term Investments Long-term investments Cash $ 1,393 $ — $ — $ 1,393 $ 1,393 $ — $ — Level 1: Money market fund 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 December 31, 2018 Reported as: (in thousands) Amortized cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Cash and Cash Equivalents Short-term Investments Long-term investments Cash $ 3,021 $ — $ — $ 3,021 $ 3,021 $ — $ — Level 1: Money market fund 33,154 — — 33,154 33,154 — — Level 2: Commercial paper 68,467 — (63) 68,404 997 67,407 — Corporate debt securities 89,038 4 (63) 88,979 — 86,692 2,287 Asset-backed securities 49,838 3 (34) 49,807 — 49,807 — Subtotal 207,343 7 (160) 207,190 997 203,906 2,287 Total assets measured at fair value $ 243,518 $ 7 $ (160) $ 243,365 $ 37,172 $ 203,906 $ 2,287
Amortized Cost, Unrealized Holding Gains or Losses, and Fair Value of Marketable Securities	The following table summarizes the Company's available-for-sale investments that were in a continuous unrealized loss position but were not deemed to be other-than-temporarily impaired, as of December 31, 2019 and 2018. December 31, 2019 December 31, 2018 (in thousands) Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. government agency securities $ 24,235 $ (14) $ — $ — Commercial paper 5,426 (2) 67,407 (63) Corporate debt securities 38,668 (20) 85,699 (63) Asset-backed securities — — 36,730 (34) Total $ 68,329 $ (36) $ 189,836 $ (160)
Contractual Maturities of Cash Equivalents (Excluding Money Market Funds)	The following table summarizes the maturities of the Company’s cash equivalents (excluding money market funds) and available-for-sale investments, as of December 31, 2019. (in thousands) Amortized Cost Fair Value Mature in less than one year $ 289,156 $ 289,424 Mature in one to five years 46,963 46,980 Total $ 336,119 $ 336,404
Reconciliation of Liabilities Using Level 3 Unobservable Inputs	The following table presents a reconciliation of financial liabilities measured at fair value on a recurring basis using Level 3 unobservable inputs for the years ended December 31, 2019 and 2018. 2019 2018 (in thousands) Compound Derivative Liability Compound Derivative Liability Warrant Fair value at beginning of year $ 161 $ — $ 106 Additions — 654 156 Change in fair value 816 (493) 305 Reclassification to equity — — (194) Issuance of convertible preferred stock on exercise of warrant — — (373) Fair value at end of year $ 977 $ 161 $ —
Significant Unobservable Inputs Related to Level 3 Assets and Liabilities	The following table presents information about significant unobservable inputs related to the Company's Level 3 financial liabilities as of December 31, 2019. December 31, 2019 (in thousands) Fair Value Valuation Technique Significant Unobservable Input Input Compound derivative liability $977 Discounted cash flow Discount rate 10.7 % Probability of the occurrence of certain events 20.0 %

LEASES (Tables)

LEASES (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Operating lease maturity analysis	The following table presents the maturity analysis of the Company's operating lease liabilities showing the aggregate lease payments as of December 31, 2019. (in thousands) December 31, 2019 2020 $ 1,108 2021 1,377 2022 1,662 2023 and thereafter 8,434 Total lease payments (1) 12,581 Less: imputed interest (2,726) Total operating lease liabilities $ 9,855
ASC Topic 840 Disclosures	The following table presents the future minimum lease commitments under the Company’s operating leases as of December 31, 2018 as previously disclosed under prior lease accounting standards. (in thousands) December 31, 2018 2019 $ 1,076 2020 1,108 2021 562 2022 and thereafter — Total future minimum lease payments $ 2,746

OTHER BALANCE SHEET COMPONENTS

OTHER BALANCE SHEET COMPONENTS (Tables)	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Property and Equipment, Net	Property and Equipment, Net The following table presents the components of property and equipment, net as of December 31, 2019 and 2018. (in thousands) December 31, 2019 December 31, 2018 Furniture and fixtures $ 265 $ 193 Computer and lab equipment 3,867 1,888 Leasehold improvements 1,244 1,055 5,376 3,136 Less: accumulated depreciation and amortization (2,648) (1,921) Total property and equipment, net $ 2,728 $ 1,215
Schedule of Accrued Expenses and Other Current Liabilities	Accrued Expenses and Other Current Liabilities The following table presents the components of accrued expenses and other current liabilities as of December 31, 2019 and 2018. (in thousands) December 31, 2019 December 31, 2018 Accrued clinical and nonclinical study costs $ 8,343 $ 2,168 Accrued contract manufacturing 17,343 1,676 Accrued compensation 3,367 1,565 Accrued professional fees and other 3,727 935 Total accrued expenses and other current liabilities $ 32,780 $ 6,344

BORROWINGS (Tables)

BORROWINGS (Tables)	12 Months Ended
	Dec. 31, 2019
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 December 31, 2019. (in thousands) December 31, 2019 2020 $ 5,038 2021 21,259 2022 26,675 2023 19,893 72,865 Less: amount representing interest (12,865) Present value of Term Loan 60,000 Less: current portion — Long-term portion of Term Loan $ 60,000

COMMITMENT AND CONTINGENCIES (T

COMMITMENT AND CONTINGENCIES (Tables)	12 Months Ended
	Dec. 31, 2019
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 December 31, 2019. December 31, 2019 (in thousands) Total Less than One Year One to Three Years Three to Five Years More than Five Years Term Loan (1) $ 72,865 $ 5,038 $ 47,934 $ 19,893 $ — Lease obligations (2) 20,774 1,309 5,018 5,953 8,494 Tenant improvement loan 140 93 47 — — Manufacturing and service contracts (3) 600,269 64,354 83,107 113,202 339,606 Total contractual obligations and commitments $ 694,048 $ 70,794 $ 136,106 $ 139,048 $ 348,100 (1) The long-term debt obligation is comprised of the Third Amended to the Loan and Security Agreement that was executed during March 2019. (2) These amounts are 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. (3) 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.

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Schedule of Common Stock Reserved for Future Issuance	Common stock reserved for future issuance as of December 31, 2019 and 2018, consisted of the following. December 31, 2019 December 31, 2018 Stock options and RSUs issued and outstanding 6,809,257 4,599,307 Stock options, RSUs and ESPP shares authorized for future issuance 3,257,316 4,534,784 Total 10,066,573 9,134,091

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Schedule of Stock Option Activity	The following table summarizes stock option activity under the plans for the year ended December 31, 2019. Shares Weighted- Weighted- Average Remaining Contractual Term (years) Aggregate Intrinsic Value (thousands) Balance at December 31, 2018 4,577,515 $ 5.99 8.0 $ 84,290 Granted 3,720,091 29.71 Exercised (1,108,700) 1.77 Forfeited or canceled (390,923) 28.29 Balance at December 31, 2019 6,797,983 $ 18.38 8.4 $ 133,892 Vested and expected to vest at December 31, 2019 6,471,442 $ 17.96 8.3 $ 129,998
Schedule of Restricted Stock Activity	The following table summarizes RSU activity under the 2018 Plan for the year ended December 31, 2019. Shares Weighted- Unvested balance at December 31, 2018 21,792 $ 19.00 Granted 11,274 36.74 Vested (21,792) 19.00 Forfeited — Unvested balance at December 31, 2019 11,274 $ 36.74
Schedule of Stock Options, Valuation Assumptions	The fair value of the stock options granted to employees for the years ended December 31, 2019, 2018 and 2017 was calculated with the following assumptions. Years Ended December 31, 2019 2018 2017 Risk-free interest rate 2.1 % 2.7 % 1.7 % Expected volatility 73.6 % 64.6 % 72.7% - 78.5% Expected term (in years) 5.9 5.8 6.2 - 6.3 Expected dividends — % — % — % The fair value of the stock options granted to nonemployees for the years ended December 31, 2019, 2018 and 2017 was calculated with the following assumptions. Years Ended December 31, 2019 2018 2017 Risk-free interest rate 2.5 % 2.7 % 1.7% - 2.2% Expected volatility 76.4 % 68.4 % 70.8% - 73.1% Expected term (in years) 6.4 10.0 6.5 - 8.9 Expected dividends — % — % — %
Schedule of Weighted Average Fair Value and Intrinsic Value	The following table summarizes the weighted-average fair value per share of stock options granted and the total intrinsic value of stock options exercised for the years ended December 31, 2019, 2018 and 2017. Years Ended December 31, (in thousands, except per share amounts) 2019 2018 2017 Stock options granted - weighted-average grant date fair value per share $ 19.28 $ 10.39 $ 1.67 Stock options exercised - intrinsic value 34,416 1,935 30
Schedule of Stock-based Compensation Expense	The following table presents stock-based compensation expense as reported in the Company’s statements of operations and comprehensive loss for the years ended December 31, 2019, 2018 and 2017. Years Ended December 31, (in thousands) 2019 2018 2017 Research and development $ 13,547 $ 2,643 $ 379 General and administrative 11,621 2,509 497 Total $ 25,168 $ 5,152 $ 876 The following table presents stock-based compensation expense by award type as reported in the Company’s statements of operations and comprehensive loss for the years ended December 31, 2019, 2018 and 2017. Years Ended December 31, (in thousands) 2019 2018 2017 Stock options $ 24,271 $ 4,806 $ 876 RSUs 447 202 — ESPP 450 144 — Total $ 25,168 $ 5,152 $ 876

NET LOSS PER SHARE (Tables)

NET LOSS PER SHARE (Tables)	12 Months Ended
	Dec. 31, 2019
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 years ended December 31, 2019, 2018 and 2017. Years Ended December 31, (In thousands, except share and per share amounts) 2019 2018 2017 Numerator: Net loss $ (176,813) $ (102,808) $ (41,290) Denominator: Weighted average common shares outstanding 47,530,174 22,158,354 2,267,732 Less: weighted average shares subject to repurchase (8,937) (12,162) (130,042) Weighted average number of shares used in basic and diluted net loss per share 47,521,237 22,146,192 2,137,690 Net loss per share, basic and diluted $ (3.72) $ (4.64) $ (19.32)
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. December 31, 2019 2018 2017 Series A convertible preferred stock — — 2,839,886 Series B convertible preferred stock — — 8,172,579 Series C convertible preferred stock — — 8,996,586 Series D convertible preferred stock — — 6,154,166 Warrants to purchase convertible preferred or common stock 131,998 106,916 24,104 Common stock subject to repurchase 5,040 20,193 366 Options and RSUs issued and outstanding 6,809,257 4,599,307 3,588,663 Total 6,946,295 4,726,416 29,776,350

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of Deferred Tax Assets	The significant components of the Company’s net deferred tax assets as of December 31, 2019 and 2018 are shown below. December 31, (in thousands) 2019 2018 Deferred tax assets Net operating loss carryforwards $ 82,252 $ 45,215 Research and development credits 8,968 4,090 Capitalized assets 79 23 Accruals and reserves 651 390 Operating lease liabilities 2,070 806 Stock-based compensation 4,250 — Gross deferred tax assets 98,270 50,524 Deferred tax liabilities Operating lease right-of-use assets (1,969) — Gross deferred tax liabilities (1,969) — Total net deferred tax assets 96,301 50,524 Less: valuation allowance (96,301) (50,524) Net deferred tax assets $ — $ —
Schedule of Effective Income Tax Rate Reconciliation	The following is a reconciliation between the U.S. federal income statutory tax rate and the Company’s effective tax rate for the years ended December 31, 2019, 2018 and 2017. Years Ended December 31, 2019 2018 2017 U.S. federal statutory rate 21.0 % 21.0 % 34.0 % State income taxes, net of federal benefit — — 5.8 Stock-based compensation 2.2 (0.2) (0.7) Permanent adjustments (0.1) (0.1) 4.2 Change to valuation allowance (25.9) (21.9) (19.6) Tax Cuts and Jobs Act Impact — — (25.4) Research and development credits 2.8 1.3 1.6 Net unrealized gain on available-for-sale investments 0.1 — — Other — (0.1) — Effective tax rate 0.1 % — % — %
Schedule of Unrecognized Tax Benefits	The beginning and ending gross unrecognized tax benefits amounts are as follows. Years Ended December 31, (in thousands) 2019 2018 2017 Gross unrecognized tax benefits at beginning of year $ 1,297 $ 819 $ 574 Additions for tax positions related to prior year — — 2 Decrease related to prior year tax provisions — — (92) Additions for tax positions related to current year 1,246 478 335 Gross unrecognized tax benefits at end of year $ 2,543 $ 1,297 $ 819

SELECTED QUARTERLY FINANCIAL _2

SELECTED QUARTERLY FINANCIAL DATE (UNAUDITED) (Tables)	12 Months Ended
	Dec. 31, 2019
Condensed Financial Information Disclosure [Abstract]
Selected Quarterly Financial Information	Net loss per share for all periods presented has been retroactively adjusted to reflect the 1-for-3.98 reverse stock split effected on June 15, 2018. 2019 (in thousands, except per share data) Q1 Q2 Q3 Q4 Operating expenses $ 37,775 $ 37,837 $ 45,096 $ 58,116 Net loss (37,897) (36,626) (44,119) (58,171) Net loss per share, basic and diluted $ (0.90) $ (0.75) $ (0.89) $ (1.17) 2018 (in thousands, except per share data) Q1 Q2 Q3 Q4 Operating expenses $ 20,098 $ 25,279 $ 29,408 $ 28,810 Net loss (20,504) (25,362) (29,098) (27,844) Net loss per share, basic and diluted $ (9.00) $ (10.89) $ (0.71) $ (0.66)

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Aug. 14, 2019	Jan. 01, 2019	Jul. 02, 2018
Class of Stock [Line Items]
Property and equipment, useful life	3 years
Operating lease ROU assets	$ 9,376	$ 8,100	$ 2,300
Operating lease liabilities	$ 9,855	$ 8,100	$ 2,500
Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, shares outstanding (in shares)				104,225,638
Common Stock
Class of Stock [Line Items]
Number of common stock issued upon conversion (in shares)				26,187,321

FAIR VALUE MEASUREMENTS AND F_3

FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)Position	Dec. 31, 2018USD ($)Position	Dec. 31, 2017USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Income	$ 8.7	$ 3.5	$ 0.4
Securities positions in an unrealized loss position | Position	18	48
Discount rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input	0.107
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
Level 3 | Term Loan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated fair value of term loan	$ 59.2	$ 37.8
Level 3 | Discount rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input	0.107
Level 3 | 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

FAIR VALUE MEASUREMENTS AND F_4

FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS - Financial assets and liabilities by hierarchy (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 18,574	$ 37,172
Level 2:
Amortized Cost	336,119
Debt Securities, Available-for-sale	336,404
Total assets measured at fair value
Short-term investments	289,424	203,906
Long-term investments	46,980	2,287
Fair Value, Inputs, Level 2
Level 2:
Gross Unrealized Losses	(36)	(160)
Fair Value, Inputs, Level 2 | U.S. government agency securities
Level 2:
Gross Unrealized Losses	(14)	0
Fair Value, Inputs, Level 2 | Commercial paper
Level 2:
Gross Unrealized Losses	(2)	(63)
Fair Value, Inputs, Level 2 | Corporate debt securities
Level 2:
Gross Unrealized Losses	(20)	(63)
Fair Value, Inputs, Level 2 | Asset-backed securities
Level 2:
Gross Unrealized Losses	0	(34)
Fair Value, Measurements, Recurring
Total assets measured at fair value
Amortized Cost	354,693	243,518
Gross Unrealized Gains	321	7
Gross Unrealized Losses	(36)	(160)
Fair Value	354,978	243,365
Fair Value, Measurements, Recurring | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	18,574	37,172
Fair Value, Measurements, Recurring | Short-term Investments
Total assets measured at fair value
Short-term investments	289,424	203,906
Fair Value, Measurements, Recurring | Long-term investments
Total assets measured at fair value
Long-term investments	46,980	2,287
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		33,154
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Level 2:
Amortized Cost	336,119	207,343
Gross Unrealized Gains	321	7
Gross Unrealized Losses	(36)	(160)
Debt Securities, Available-for-sale	336,404	207,190
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Cash and Cash Equivalents
Level 2:
Debt Securities, Available-for-sale	0	997
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Short-term Investments
Total assets measured at fair value
Short-term investments	289,424	203,906
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Long-term investments
Total assets measured at fair value
Long-term investments	46,980	2,287
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | U.S. government agency securities
Level 2:
Amortized Cost	40,741
Gross Unrealized Gains	6
Gross Unrealized Losses	(14)
Debt Securities, Available-for-sale	40,733
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | U.S. government agency securities | Cash and Cash Equivalents
Level 2:
Debt Securities, Available-for-sale	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | U.S. government agency securities | Short-term Investments
Total assets measured at fair value
Short-term investments	19,990
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | U.S. government agency securities | Long-term investments
Total assets measured at fair value
Long-term investments	20,743
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Commercial paper
Level 2:
Amortized Cost	108,248	68,467
Gross Unrealized Gains	107	0
Gross Unrealized Losses	(2)	(63)
Debt Securities, Available-for-sale	108,353	68,404
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Commercial paper | Cash and Cash Equivalents
Level 2:
Debt Securities, Available-for-sale	0	997
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Commercial paper | Short-term Investments
Total assets measured at fair value
Short-term investments	108,353	67,407
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Commercial paper | Long-term investments
Total assets measured at fair value
Long-term investments	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Corporate debt securities
Level 2:
Amortized Cost	185,569	89,038
Gross Unrealized Gains	205	4
Gross Unrealized Losses	(20)	(63)
Debt Securities, Available-for-sale	185,754	88,979
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Corporate debt securities | Cash and Cash Equivalents
Level 2:
Debt Securities, Available-for-sale	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Corporate debt securities | Short-term Investments
Total assets measured at fair value
Short-term investments	159,517	86,692
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Corporate debt securities | Long-term investments
Total assets measured at fair value
Long-term investments	26,237	2,287
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Asset-backed securities
Level 2:
Amortized Cost	1,561	49,838
Gross Unrealized Gains	3	3
Gross Unrealized Losses	0	(34)
Debt Securities, Available-for-sale	1,564	49,807
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Asset-backed securities | Cash and Cash Equivalents
Level 2:
Debt Securities, Available-for-sale	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Asset-backed securities | Short-term Investments
Total assets measured at fair value
Short-term investments	1,564	49,807
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Asset-backed securities | Long-term investments
Total assets measured at fair value
Long-term investments	0	0
Cash | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	1,393	3,021
Cash and Cash Equivalents, Fair Value Disclosure	1,393	3,021
Cash | Fair Value, Measurements, Recurring | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	1,393	3,021
Money market fund | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	17,181	33,154
Cash and Cash Equivalents, Fair Value Disclosure	17,181	$ 33,154
Money market fund | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 17,181

FAIR VALUE MEASUREMENTS AND F_5

FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS - Unrealized losses on Debt Securities, Available-For-Sale (Details) - Fair Value, Inputs, Level 2 - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 68,329	$ 189,836
Unrealized Losses	(36)	(160)
U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	24,235	0
Unrealized Losses	(14)	0
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	5,426	67,407
Unrealized Losses	(2)	(63)
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	38,668	85,699
Unrealized Losses	(20)	(63)
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	36,730
Unrealized Losses	$ 0	$ (34)

FAIR VALUE MEASUREMENTS AND F_6

FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS - Maturities of Debt Securities, Available-For-Sale (Details) $ in Thousands	Dec. 31, 2019USD ($)
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Cash equivalents, mature in less than one year, amortized cost	$ 289,156
Cash equivalents, mature in one to five years, amortized costs	46,963
Amortized Cost	336,119
Debt Securities, Available-for-sale [Abstract]
Cash equivalents, mature in less than one year, fair value	289,424
Cash equivalents, mature in one to five years, fair value	46,980
Fair Value	$ 336,404

FAIR VALUE MEASUREMENTS AND F_7

FAIR VALUE MEASUREMENTS AND FAIR VALUE OF FINANCIAL INSTRUMENTS - Reconciliation of liabilities measured using Level 3 (Details) - Level 3 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Compound Derivative Liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value at beginning of year	$ 161	$ 0
Additions	0	654
Change in fair value	816	(493)
Reclassification to equity	0	0
Issuance of convertible preferred stock on exercise of warrant	0	0
Fair value at end of year	977	161
Warrant
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value at beginning of year	$ 0	106
Additions		156
Change in fair value		305
Reclassification to equity		(194)
Issuance of convertible preferred stock on exercise of warrant		(373)
Fair value at end of year		$ 0

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)	Dec. 31, 2019
Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative liability, measurement input	0.107
Probability of the occurrence of certain events
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative liability, measurement input	0.200
Level 3 | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative liability, measurement input	0.107
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 - Additional Details (De

LEASES - Additional Details (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Sep. 01, 2020ft²	Aug. 15, 2019ft²	Aug. 14, 2019USD ($)ft²	Jan. 01, 2019USD ($)	Aug. 31, 2017ft²	Jul. 31, 2014
Lessee, Lease, Description [Line Items]
Term of noncancelable operating lease									5 years
Term of lease extension option									3 years
Extension of leased space (in square feet)						19,177
Temporary office space leased (in square feet)					5,569
Length of lease extension (in months)						84 months
Length of lease option to extend (in months)	36 months
Operating lease right-of-use assets | $	$ 9,376					$ 8,100	$ 2,300
Total operating lease liabilities | $	9,855					$ 8,100	$ 2,500
Operating lease expense | $	1,300	$ 1,000	$ 700
Cash payments for operating leases | $	$ 1,100
Weighted average discount rate	6.00%
Weighted average remaining lease term	7 years 8 months 12 days
Scenario, Forecast
Lessee, Lease, Description [Line Items]
Lease rentable area (in square feet)				46,074
Subject to Operating Lease
Lessee, Lease, Description [Line Items]
Lease rentable area (in square feet)								26,987
Subject to Operating Lease | Amended Lease
Lessee, Lease, Description [Line Items]
Lease rentable area (in square feet)								13,258
Subject to Operating Lease | Second Amendment To Lease
Lessee, Lease, Description [Line Items]
Lease rentable area (in square feet)								26,897

LEASES - Maturity Schedule (Det

LEASES - Maturity Schedule (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Aug. 14, 2019	Jan. 01, 2019
Leases, Operating [Abstract]
2020	$ 1,108
2021	1,377
2022	1,662
2023 and thereafter	8,434
Total lease payments	12,581
Less: imputed interest	(2,726)
Total operating lease liabilities	9,855	$ 8,100	$ 2,500
Expected payments on second expansion premises	$ 8,200
Lease term on second expansion premises	7 years

LEASES - ASC Topic 840 Disclosu

LEASES - ASC Topic 840 Disclosures (Details) $ in Thousands	Dec. 31, 2018USD ($)
Leases [Abstract]
2019	$ 1,076
2020	1,108
2021	562
2022 and Thereafter	0
Operating Leases, Future Minimum Payments Due, Total	$ 2,746

OTHER BALANCE SHEET COMPONENT_2

OTHER BALANCE SHEET COMPONENTS - Property and Equipment, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 5,376	$ 3,136
Less: accumulated depreciation and amortization	(2,648)	(1,921)
Total property and equipment, net	2,728	1,215
Depreciation and amortization expense	757	618	$ 335
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	265	193
Computer and lab equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,867	1,888
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,244	$ 1,055

OTHER BALANCE SHEET COMPONENT_3

OTHER BALANCE SHEET COMPONENTS - Accrued Expense and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued clinical and nonclinical study costs	$ 8,343	$ 2,168
Accrued contract manufacturing	17,343	1,676
Accrued compensation	3,367	1,565
Accrued professional fees and other	3,727	935
Total accrued expenses and other current liabilities	$ 32,780	$ 6,344

BORROWINGS - Additional Informa

BORROWINGS - Additional Information (Details)	Dec. 13, 2019USD ($)$ / sharesshares	Mar. 27, 2019USD ($)$ / sharesshares	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 28, 2018USD ($)$ / sharesshares	Oct. 15, 2018USD ($)tranche	Apr. 10, 2018USD ($)	Feb. 28, 2018USD ($)tranche$ / sharesshares
Debt Instrument [Line Items]
Principal outstanding			$ 58,374,000	$ 38,071,000
Increase (decrease) in equity due to warrants					$ 900,000
Percentage of principal amount			1.00%
Term Loan
Debt Instrument [Line Items]
Debt aggregate principal amount						$ 100,000,000		$ 100,000,000
Debt, number of tranches | tranche						5		5
Principal outstanding			$ 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
Warrant liability								$ 200,000
Increase (decrease) in equity due to warrants							$ 200,000
Fair value of embedded derivative liability			1,000,000				$ 700,000
Unamortized issuance costs and debt discounts			$ 3,600,000	$ 2,700,000
Term Loan | Minimum
Debt Instrument [Line Items]
Debt prepayment fee, percentage		2.00%
Term Loan | Tranche one, funded on closing date
Debt Instrument [Line Items]
Debt aggregate principal amount								25,000,000
Term Loan | Tranche two, funded on December 28, 2018
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]
Principal outstanding		$ 200,000,000
Additional payment of principal		$ 2,600,000
Prepayment fee, percentage after month 12 before month 24		1.50%
Prepayment fee, percentage after 24 months before 36 months		1.00%
Prepayment fee, percentage after 36 months until maturity		0.00%
Term of interest and principal payment		30 months
New Term Loan | Maximum
Debt Instrument [Line Items]
Extension period of interest only payment		24 months
New Term Loan | Tranche one, funded on closing date
Debt Instrument [Line Items]
Debt aggregate principal amount		$ 20,000,000
New Term Loan | Tranche two, funded on December 28, 2018
Debt Instrument [Line Items]
Debt aggregate principal amount		15,000,000
New Term Loan | Tranche three, funded on or before December 31, 2019
Debt Instrument [Line Items]
Debt aggregate principal amount		75,000,000
New Term Loan | Tranche four, funded on or before December 15, 2020
Debt Instrument [Line Items]
Debt aggregate principal amount		$ 50,000,000
Third Amendment To Term Loan
Debt Instrument [Line Items]
Exercise price of warrant (in USD per share) | $ / shares		$ 23.92
Value of common stock warrants recorded in stockholders' equity (deficit) at fair value	$ 300,000	$ 300,000
Third Amendment to Term Loan
Debt Instrument [Line Items]
Number of shares called by warrant (in shares) | shares	8,361	16,721
Exercise price of warrant (in USD per share) | $ / shares	$ 23.92	$ 23.92
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%
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 assumption, time to liquidity	7 years	7 years
Volatility | Third Amendment To Term Loan
Debt Instrument [Line Items]
Warrants measurement input	0.727	0.750
Risk-free interest rate | Third Amendment To Term Loan
Debt Instrument [Line Items]
Warrants measurement input	0.018	0.023
Discount rate
Debt Instrument [Line Items]
Measurement input assumption			0.107
Probability of the occurrence of certain events
Debt Instrument [Line Items]
Measurement input assumption			0.200

BORROWINGS - Debt Maturity Sche

BORROWINGS - Debt Maturity Schedule (Details) $ in Thousands	Dec. 31, 2019USD ($)
Debt Instrument [Line Items]
2020	$ 5,038
2021	21,259
2022	26,675
2023	19,893
Long-term debt including interest payable	72,865
Less: amount representing interest	(12,865)
Present value of Term Loan	60,000
Less: current portion	0
Long-term portion of Term Loan	$ 60,000

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Additional Information (Details) $ in Thousands	Dec. 31, 2019USD ($)
Long-term debt
Less than One Year	$ 5,038
Lease obligations
Total	20,774
Less than One Year	1,309
One to Three Years	5,018
Three to Five Years	5,953
More than Five Years	8,494
Manufacturing and service contracts
Total	600,269
Less than One Year	64,354
One to Three Years	83,107
Three to Five Years	113,202
Purchase Obligation, Due after Fifth Year	339,606
Total contractual obligations and commitments
Total	694,048
Less than One Year	70,794
One to Three Years	136,106
Three to Five Years	139,048
More than Five Years	348,100
Term Loan
Long-term debt
Total	72,865
Less than One Year	5,038
One to Three Years	47,934
Three to Five Years	19,893
More than Five Years	0
Tenant Improvement Loan
Long-term debt
Total	140
Less than One Year	93
One to Three Years	47
Three to Five Years	0
More than Five Years	$ 0

STOCKHOLDERS' EQUITY - Addition

STOCKHOLDERS' EQUITY - Additional Information (Details) $ / shares in Units, $ in Millions	Apr. 08, 2019USD ($)$ / sharesshares	Jul. 02, 2018USD ($)$ / sharesshares	Jun. 15, 2018	Dec. 31, 2019$ / sharesshares	Dec. 31, 2018$ / sharesshares
Class of Stock [Line Items]
Number of all classes of stock authorized		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) | $ / shares				$ 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) | $ / shares				$ 0.001	$ 0.001
Common stock, shares issued (in shares)				49,763,176	42,148,247
Common stock, shares outstanding (in shares)				49,763,176	42,148,247
Preferred stock outstanding (in shares)				0	0
Reserve stock split ratio			0.2513
Convertible Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, shares outstanding (in shares)		104,225,638
Common Stock
Class of Stock [Line Items]
Number of common stock issued upon conversion (in shares)		26,187,321
IPO
Class of Stock [Line Items]
Number of common stock issued (in shares)		13,455,000
Share price (in USD per share) | $ / shares		$ 19
Proceeds from initial public offering, net of issuance costs | $		$ 237.7
Sale of Stock, Underwriting Discounts And Commissions | $		$ 17.9
Underwritten Public Offering
Class of Stock [Line Items]
Number of common stock issued (in shares)	6,440,000
Share price (in USD per share) | $ / shares	$ 36
Proceeds from initial public offering, net of issuance costs | $	$ 217.9
Sale Of Stock, Underwriting Discounts And Commissions | $	$ 13.9
Over-Allotment Option
Class of Stock [Line Items]
Number of common stock issued (in shares)	840,000

STOCKHOLDERS' EQUITY - Common S

STOCKHOLDERS' EQUITY - Common Stock (Details) - shares	Dec. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Stock options and RSUs issued and outstanding (in shares)	6,809,257	4,599,307
Stock options, RSUs and ESPP shares authorized for future issuance (in shares)	3,257,316	4,534,784
Total (in shares)	10,066,573	9,134,091

STOCK-BASED COMPENSATION - Addi

STOCK-BASED COMPENSATION - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Aug. 31, 2019	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, RSUs and ESPP shares authorized for future issuance (in shares)			3,257,316	4,534,784
Award expiration period			10 years
Expiration term of options after the termination of continuous service for reasons other than cause, death, or disability			3 months
Expiration term of options after the termination of continuous service for disability			12 months
Expiration term of options after the termination of continuous service for employee's death			18 months
Shares of common stock subject to repurchase (in shares)			5,040	20,193
Aggregate purchase price of shares available for repurchase			$ 17	$ 89
Average price per share of shares available for repurchase (in dollars per share)			$ 3.47	$ 4.40
Granted (in shares)			3,720,091
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			1 year
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			4 years
2018 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, RSUs and ESPP shares authorized for future issuance (in shares)				4,000,000
Annual increase in number of shares authorized (in shares)			3,200,000
Annual percentage increase in number of shares authorized						4.00%
Number of shares available for future issuance (in shares)			2,098,380	1,685,929
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation, period for recognition			4 months 24 days
Employee Stock | Tricida, Inc. ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, RSUs and ESPP shares authorized for future issuance (in shares)		800,000
Annual increase in number of shares authorized (in shares)						800,000
Annual percentage increase in number of shares authorized						1.00%
Number of shares available for future issuance (in shares)			1,158,936
Maximum percentage of employee pay to be withheld for employee stock purchase plan		15.00%
Maximum number of shares purchased by employee (in shares)		2,500
Employee purchase plan offering period		6 months
Employee stock purchase price, percentage of market closing price		85.00%
Increase in shares reserved for issuance under the ESPP			421,482
Shares issued under employee stock purchase plan (in shares)			44,437
ESPP cash contributions			$ 1,100
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation			$ 54,600
Unrecognized stock-based compensation, period for recognition			2 years 7 months 6 days
Employee Stock Option | Share-based Payment Arrangement, Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate			2.10%	2.70%	1.70%
Expected volatility			73.60%	64.60%
Expected term (in years)			5 years 10 months 24 days	5 years 9 months 18 days
Expected dividends			0.00%	0.00%	0.00%
Employee Stock Option | Minimum | Share-based Payment Arrangement, Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility					72.70%
Expected term (in years)					6 years 2 months 12 days
Employee Stock Option | Maximum | Share-based Payment Arrangement, Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility					78.50%
Expected term (in years)					6 years 3 months 18 days
PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation			$ 200
PSUs | 2018 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	18 months
Granted (in shares)	594,000
Director | Restricted Stock Units (RSUs) | 2018 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			1 year

STOCK-BASED COMPENSATION - Sche

STOCK-BASED COMPENSATION - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning balance (in shares)	4,577,515
Granted (in shares)	3,720,091
Exercised (in shares)	(1,108,700)
Forfeited (in shares)	(390,923)
Ending balance (in shares)	6,797,983	4,577,515
Vested and expected to vest at end of period, (in shares)	6,471,442
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Beginning balance (in USD per share)	$ 5.99
Granted (in USD per share)	29.71
Exercised (in USD per share)	1.77
Forfeited (in USD per share)	28.29
Ending balance (in USD per share)	18.38	$ 5.99
Vested and expected to vest at end of period (in USD per share)	$ 17.96
Weighted- Average Remaining Contractual Term (years)	8 years 4 months 24 days	8 years
Weighted-average remaining contractual term, vested and expected to vest	8 years 3 months 18 days
Aggregate intrinsic value	$ 133,892	$ 84,290
Aggregate intrinsic value, vested and expected to vest	$ 129,998

STOCK-BASED COMPENSATION - Sc_2

STOCK-BASED COMPENSATION - Schedule of Restricted Stock Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Weighted- Average Grant Date Fair Value
Unvested balance beginning of period	$ 19
Granted	36.74
Vested	19
Unvested balance end of period	$ 36.74	$ 19
Restricted Stock Units (RSUs)
Shares
Unvested balance beginning of period	21,792
Granted	11,274
Vested	(21,792)
Forfeited	0
Unvested balance end of period	11,274	21,792
Weighted- Average Grant Date Fair Value
Fair value of RSUs vested	$ 800	$ 0	$ 0

STOCK-BASED COMPENSATION - Stoc

STOCK-BASED COMPENSATION - Stock Options Valuation Assumptions (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Employee Stock Option | Share-based Payment Arrangement, Employee
Stock options granted to employees
Risk-free interest rate	2.10%	2.70%	1.70%
Expected volatility	73.60%	64.60%
Expected term (in years)	5 years 10 months 24 days	5 years 9 months 18 days
Expected dividends	0.00%	0.00%	0.00%
Non-Employee Stock Option | Share-based Payment Arrangement, Nonemployee
Stock options granted to employees
Risk-free interest rate	2.50%	2.70%
Expected volatility	76.40%	68.40%
Expected term (in years)	6 years 4 months 24 days	10 years
Expected dividends	0.00%	0.00%
Stock options granted to nonemployees
Expected dividends			0.00%
Minimum | Employee Stock Option | Share-based Payment Arrangement, Employee
Stock options granted to employees
Expected volatility			72.70%
Expected term (in years)			6 years 2 months 12 days
Minimum | Non-Employee Stock Option | Share-based Payment Arrangement, Nonemployee
Stock options granted to nonemployees
Risk-free interest rate			1.70%
Expected volatility			70.80%
Expected term (in years)			6 years 6 months
Maximum | Employee Stock Option | Share-based Payment Arrangement, Employee
Stock options granted to employees
Expected volatility			78.50%
Expected term (in years)			6 years 3 months 18 days
Maximum | Non-Employee Stock Option | Share-based Payment Arrangement, Nonemployee
Stock options granted to nonemployees
Risk-free interest rate			2.20%
Expected volatility			73.10%
Expected term (in years)			8 years 10 months 24 days

STOCK-BASED COMPENSATION - Weig

STOCK-BASED COMPENSATION - Weighted average fair value per share and intrinsic value (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Payment Arrangement [Abstract]
Stock options granted - weighted-average grant date fair value per share	$ 19.28	$ 10.39	$ 1.67
Stock options exercised - intrinsic value	$ 34,416	$ 1,935	$ 30

STOCK-BASED COMPENSATION - Sc_3

STOCK-BASED COMPENSATION - Schedule of Stock-based Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 25,168	$ 5,152	$ 876
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	24,271	4,806	876
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	447	202	0
Employee Stock Purchase Plan (ESPP)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	450	144	0
Research and Development Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	13,547	2,643	379
General and Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 11,621	$ 2,509	$ 497

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								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share Reconciliation [Abstract]
Net loss	$ (58,171)	$ (44,119)	$ (36,626)	$ (37,897)	$ (27,844)	$ (29,098)	$ (25,362)	$ (20,504)	$ (176,813)	$ (102,808)	$ (41,290)
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted average common shares outstanding (in shares)									47,530,174	22,158,354	2,267,732
Less: weighted average shares subject to repurchase (in shares)									(8,937)	(12,162)	(130,042)
Weighted-average number of shares used in basic and diluted net loss per share (in shares)									47,521,237	22,146,192	2,137,690
Net loss per share, basic and diluted (in USD per share)	$ (1.17)	$ (0.89)	$ (0.75)	$ (0.90)	$ (0.66)	$ (0.71)	$ (10.89)	$ (9)	$ (3.72)	$ (4.64)	$ (19.32)

NET LOSS PER SHARE - Antidiluti

NET LOSS PER SHARE - Antidilutive securities (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	6,946,295	4,726,416	29,776,350
Warrant
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	131,998	106,916	24,104
Common Stock Subject to Mandatory Redemption
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	5,040	20,193	366
Share-based Payment Arrangement, Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	6,809,257	4,599,307	3,588,663
Series A Preferred Stock | Convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	0	0	2,839,886
Series B Preferred Stock | Convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	0	0	8,172,579
Series C Preferred Stock | Convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	0	0	8,996,586
Series D Preferred Stock | Convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	0	0	6,154,166

INCOME TAXES - Additional Infor

INCOME TAXES - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Income tax benefit	$ (92)	$ 0	$ 0
Valuation allowance	96,301	50,524
Increase in valuation allowance		10,500
Reduction in the value of net deferred assets		10,500
Unrecognized tax benefits	2,543	$ 1,297	819	$ 574
Real Estate Owned, Valuation Allowance, Period Increase (Decrease)	45,800
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	272,800
Operating losses subject to expiration			$ 89,100
Research tax credit carryforward	8,000
Domestic Tax Authority | Internal Revenue Service (IRS)
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	361,900
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	89,600
Research tax credit carryforward	$ 4,200

INCOME TAXES - Schedule of Defe

INCOME TAXES - Schedule of Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 82,252	$ 45,215
Research and development credits	8,968	4,090
Capitalized assets	79	23
Accruals and reserves	651	390
Operating lease liabilities	2,070	806
Stock-based compensation	4,250	0
Gross deferred tax assets	98,270	50,524
Operating lease right-of-use assets	(1,969)	0
Gross deferred tax liabilities	(1,969)	0
Total net deferred tax assets	96,301	50,524
Less: valuation allowance	(96,301)	(50,524)
Net deferred tax assets	$ 0	$ 0

INCOME TAXES - Schedule of Inco

INCOME TAXES - Schedule of Income Tax Reconciliation (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
U.S. federal statutory rate	21.00%	21.00%	34.00%
State income taxes, net of federal benefit	0.00%	0.00%	5.80%
Stock-based compensation	2.20%	(0.20%)	(0.70%)
Permanent adjustments	(0.10%)	(0.10%)	4.20%
Change to valuation allowance	(25.90%)	(21.90%)	(19.60%)
Tax Cuts and Jobs Act Impact	0.00%	0.00%	(25.40%)
Research and development credits	2.80%	1.30%	1.60%
Net unrealized gain on available-for-sale investments	0.10%	0.00%	0.00%
Other	0.00%	(0.10%)	0.00%
Effective tax rate	0.10%	0.00%	0.00%

INCOME TAXES - Schedule of Unre

INCOME TAXES - Schedule of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Gross unrecognized tax benefits at beginning of year	$ 1,297	$ 819	$ 574
Additions for tax positions related to prior year	0	0	2
Decrease related to prior year tax provisions	0	0	(92)
Additions for tax positions related to current year	1,246	478	335
Gross unrecognized tax benefits at end of year	$ 2,543	$ 1,297	$ 819

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Subsequent Event [Line Items]
Research and development		$ 133,028	$ 85,594	$ 35,906
Subsequent Event | Scenario, Forecast
Subsequent Event [Line Items]
Research and development	$ 2,600

SELECTED QUARTERLY FINANCIAL _3

SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) $ / shares in Units, $ in Thousands	Jun. 15, 2018	Dec. 31, 2019USD ($)$ / shares	Sep. 30, 2019USD ($)$ / shares	Jun. 30, 2019USD ($)$ / shares	Mar. 31, 2019USD ($)$ / shares	Dec. 31, 2018USD ($)$ / shares	Sep. 30, 2018USD ($)$ / shares	Jun. 30, 2018USD ($)$ / shares	Mar. 31, 2018USD ($)$ / shares	Dec. 31, 2019USD ($)$ / shares	Dec. 31, 2018USD ($)$ / shares	Dec. 31, 2017USD ($)$ / shares
Condensed Financial Information Disclosure [Abstract]
Reserve stock split ratio	0.2513
Operating expenses		$ 58,116	$ 45,096	$ 37,837	$ 37,775	$ 28,810	$ 29,408	$ 25,279	$ 20,098	$ 178,824	$ 103,595	$ 47,122
Net loss		$ (58,171)	$ (44,119)	$ (36,626)	$ (37,897)	$ (27,844)	$ (29,098)	$ (25,362)	$ (20,504)	$ (176,813)	$ (102,808)	$ (41,290)
Net loss per share, basic and diluted (in USD per share) | $ / shares		$ (1.17)	$ (0.89)	$ (0.75)	$ (0.90)	$ (0.66)	$ (0.71)	$ (10.89)	$ (9)	$ (3.72)	$ (4.64)	$ (19.32)