Kodiak Sciences (KOD) 10-Q 10 Aug 20 2020 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Jul. 31, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Trading Symbol	KOD
Entity Registrant Name	KODIAK SCIENCES INC.
Entity Central Index Key	0001468748
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		44,712,259
Entity File Number	001-38682
Entity Tax Identification Number	27-0476525
Entity Address, Address Line One	2631 Hanover Street
Entity Address, City or Town	Palo Alto
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94304
City Area Code	650
Local Phone Number	281-0850
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common stock, par value $0.0001
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 269,836	$ 211,797
Marketable securities	147,298	124,684
Prepaid expenses and other current assets	1,880	2,749
Total current assets	419,014	339,230
Marketable securities		11,696
Restricted cash	140	140
Property and equipment, net	1,106	996
Operating lease right-of-use asset	1,591	1,790
Other assets	7,517	5,014
Total assets	429,368	358,866
Current liabilities:
Accounts payable	7,034	2,619
Accrued and other current liabilities	11,273	8,658
Operating lease liability	462	434
Total current liabilities	18,769	11,711
Operating lease liability, net of current portion	1,263	1,501
Liability related to sale of future royalties	99,863
Other liabilities	276	295
Total liabilities	120,171	13,507
Commitments and contingencies (Note 6)
Stockholders’ equity:
Preferred stock, $0.0001 par value, 10,000,000 shares authorized; 0 shares issued and outstanding at June 30, 2020 and December 31, 2019
Common stock, $0.0001 par value, 490,000,000 shares authorized at June 30, 2020 and December 31, 2019; 44,667,016 and 44,413,404 shares issued and outstanding at June 30, 2020 and December 31, 2019, respectively	5	5
Additional paid-in capital	517,120	503,475
Accumulated other comprehensive income	594	10
Accumulated deficit	(208,522)	(158,131)
Total stockholders’ equity	309,197	345,359
Total liabilities and stockholders’ equity	$ 429,368	$ 358,866

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) (unaudited) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred Stock, shares issued	0	0
Preferred Stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	490,000,000	490,000,000
Common stock, shares issued	44,667,016	44,413,404
Common stock, shares outstanding	44,667,016	44,413,404

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating expenses
Research and development	$ 20,557	$ 8,838	$ 40,727	$ 14,561
General and administrative	6,222	2,976	11,775	5,713
Total operating expenses	26,779	11,814	52,502	20,274
Loss from operations	(26,779)	(11,814)	(52,502)	(20,274)
Interest income	698	331	1,906	793
Interest expense	(6)	(2)	(13)	(6)
Other income (expense), net	88	100	218	118
Net loss	$ (25,999)	$ (11,385)	$ (50,391)	$ (19,369)
Net loss per common share, basic and diluted	$ (0.58)	$ (0.31)	$ (1.12)	$ (0.52)
Weighted-average common shares outstanding used in computing net loss per common share, basic and diluted	44,969,795	37,294,853	44,897,269	37,271,638
Other comprehensive income
Change in unrealized gains related to available-for-sale debt securities, net of tax	$ 105	$ 6	$ 584	$ 12
Total other comprehensive income	105	6	584	12
Comprehensive loss	$ (25,894)	$ (11,379)	$ (49,807)	$ (19,357)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Beginning Balance at Dec. 31, 2018	$ 86,833	$ 4	$ 197,595		$ (110,766)
Beginning balance, shares at Dec. 31, 2018		36,829,857
Issuance of common stock upon exercise of stock options	83		83
Issuance of common stock upon exercise of stock options, shares		80,000
Stock-based compensation expense	1,157		1,157
Other comprehensive income	6			$ 6
Net loss	(7,984)				(7,984)
Ending Balance at Mar. 31, 2019	80,095	$ 4	198,835	6	(118,750)
Ending balance, shares at Mar. 31, 2019		36,909,857
Beginning Balance at Dec. 31, 2018	86,833	$ 4	197,595		(110,766)
Beginning balance, shares at Dec. 31, 2018		36,829,857
Other comprehensive income	12
Net loss	(19,369)
Ending Balance at Jun. 30, 2019	70,019	$ 4	200,138	12	(130,135)
Ending balance, shares at Jun. 30, 2019		36,931,141
Beginning Balance at Mar. 31, 2019	80,095	$ 4	198,835	6	(118,750)
Beginning balance, shares at Mar. 31, 2019		36,909,857
Issuance of common stock upon exercise of stock options	59		59
Issuance of common stock upon exercise of stock options, shares		21,284
Stock-based compensation expense	1,244		1,244
Other comprehensive income	6			6
Net loss	(11,385)				(11,385)
Ending Balance at Jun. 30, 2019	70,019	$ 4	200,138	12	(130,135)
Ending balance, shares at Jun. 30, 2019		36,931,141
Beginning Balance at Dec. 31, 2019	345,359	$ 5	503,475	10	(158,131)
Beginning balance, shares at Dec. 31, 2019		44,413,404
Issuance of common stock upon exercise of stock options	159		159
Issuance of common stock upon exercise of stock options, shares		39,297
Stock-based compensation expense	6,082		6,082
Other comprehensive income	479			479
Net loss	(24,392)				(24,392)
Ending Balance at Mar. 31, 2020	327,687	$ 5	509,716	489	(182,523)
Ending balance, shares at Mar. 31, 2020		44,452,701
Beginning Balance at Dec. 31, 2019	345,359	$ 5	503,475	10	(158,131)
Beginning balance, shares at Dec. 31, 2019		44,413,404
Other comprehensive income	584
Net loss	(50,391)
Ending Balance at Jun. 30, 2020	309,197	$ 5	517,120	594	(208,522)
Ending balance, shares at Jun. 30, 2020		44,667,016
Beginning Balance at Mar. 31, 2020	327,687	$ 5	509,716	489	(182,523)
Beginning balance, shares at Mar. 31, 2020		44,452,701
Issuance of common stock upon exercise of stock options	720		720
Issuance of common stock upon exercise of stock options, shares		203,373
Issuance of common stock upon vesting of restricted stock units, net of taxes withheld	(206)		(206)
Issuance of common stock upon vesting of restricted stock units, net of taxes withheld, shares		10,942
Stock-based compensation expense	6,890		6,890
Other comprehensive income	105			105
Net loss	(25,999)				(25,999)
Ending Balance at Jun. 30, 2020	$ 309,197	$ 5	$ 517,120	$ 594	$ (208,522)
Ending balance, shares at Jun. 30, 2020		44,667,016

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities
Net loss	$ (50,391)	$ (19,369)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	216	260
Stock-based compensation	12,972	2,401
Amortization (accretion) of premium (discount) on marketable securities	(231)	(118)
Amortization of operating lease right-of-use asset	199	182
Amortization of issuance costs	22
Changes in assets and liabilities:
Prepaid expenses and other current assets	933	(152)
Other assets	(2,305)	(4,059)
Accounts payable	4,338	1,342
Accrued and other current liabilities	2,620	(459)
Operating lease liability	(210)	(185)
Net cash used in operating activities	(31,837)	(20,157)
Cash flows from investing activities
Purchase of property and equipment	(249)	(126)
Purchase of marketable securities	(86,317)	(35,066)
Maturities of marketable securities	76,150	12,000
Net cash used in investing activities	(10,416)	(23,192)
Cash flows from financing activities
Proceeds from issuance of common stock upon options exercise	879	114
Payments for restricted stock units, net of taxes withheld	(206)
Proceeds from sale of future royalties, net of issuance costs	99,643
Principal payments of capital lease	(5)	(34)
Principal payments of tenant improvement allowance payable	(19)	(18)
Net cash provided by financing activities	100,292	62
Net increase (decrease) in cash, cash equivalents and restricted cash	58,039	(43,287)
Cash, cash equivalents and restricted cash, at beginning of period	211,937	88,394
Cash, cash equivalents and restricted cash, at end of period	269,976	45,107
Reconciliation of cash, cash equivalents and restricted cash to consolidated balance sheets
Cash and cash equivalents	269,836	44,967
Restricted cash	140	140
Cash, cash equivalents and restricted cash, at end of period	269,976	45,107
Supplemental disclosures of non-cash investing and financing information:
Operating lease right-of-use asset obtained in exchange for operating lease liability		2,163
Purchase of property and equipment under accounts payable	$ 77	$ 137

The Company

The Company	6 Months Ended
	Jun. 30, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
The Company	1. The Company Kodiak Sciences Inc. (the “Company”) is a biopharmaceutical company committed to researching, developing and commercializing transformative therapeutics to treat high prevalence retinal diseases in the United States and additional international markets. The Company devotes substantially all of its resources to the research and development of its product candidates including activities to conduct clinical studies of its product candidates, manufacture product candidates and provide general and administrative support for these operations. Liquidity As of June 30, 2020, the Company had cash, cash equivalents and marketable securities of $417.1 million. Although the Company has incurred significant operating losses since inception and expects to continue to incur operating losses and negative operating cash flows for the foreseeable future, the Company believes that the cash, cash equivalents and marketable securities will be sufficient to meet the anticipated operating and capital expenditure requirements for the 12 months following the date of this Form 10-Q.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation The accompanying condensed consolidated financial statements are unaudited and have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) applicable to interim periods. The condensed consolidated financial statements These condensed consolidated financial statements have been prepared on a basis substantially consistent with, and should be read in conjunction with the audited financial statements for the year ended December 31, 2019 and notes thereto, included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on March 16, 2020. Certain information and note disclosures normally included in the audited financial statements prepared in accordance with GAAP have been condensed or omitted from this report. The results of operations for any interim period are not necessarily indicative of the results for the year ending December 31, 2020, or for any future period. The accompanying condensed consolidated financial statements reflect the operations of the Company and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated. Reclassification Certain prior period amounts have been reclassified to conform to the current period presentation. Such reclassifications had no impact on subtotals in the prior year condensed consolidated financial statements. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities as of the date of the condensed consolidated financial statements and expenses during the reporting period. The impact of the ongoing COVID-19 pandemic continues to evolve. As a result, certain estimates and assumptions required increased judgment and carried a higher degree of variability and volatility, including but not limited to, the fair value of marketable securities, performance-based equity awards, and research and development accruals for the three and six months ended June 30, 2020. As events continue to unfold and additional information becomes available, these estimates may change materially in future periods. Actual results could differ from those estimates. Risks and Uncertainties In March 2020, the World Health Organization declared a pandemic due to the global COVID-19 outbreak. The significant uncertainties caused by the ongoing COVID-19 pandemic may negatively impact the Company’s operations, liquidity, and capital resources, and will depend on certain evolving developments, including the duration and spread of the outbreak, regulatory and private sector responses and the impact on employees and vendors including supply chain and clinical partners, all of which are uncertain and cannot be predicted. During this pandemic, the Company continues to work closely with clinical sites towards maximal patient safety and the lowest number of missed visits and study discontinuations. The Company has taken and continues to take proactive measures to maintain the integrity of its ongoing clinical studies. Despite these efforts, the ongoing COVID-19 pandemic could significantly impact clinical trial enrollment and completion of its clinical studies. The Company will continue to monitor the COVID-19 situation and its impact on the ability to continue the development of, and seek regulatory approvals for, the Company’s product candidates, and begin to commercialize any approved products. Summary of Significant Accounting Policies The significant accounting policies used in preparation of these condensed consolidated financial statements for the three and six months ended June 30, 2020 are consistent with those discussed in Note 2 to the consolidated financial statements in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, except as noted below with respect to the Company’s liability related to sale of future royalties and as noted within the “Recent Accounting Pronouncements – Recently Adopted Accounting Pronouncements” section. Liability related to Sale of Future Royalties On December 1, 2019, the Company and its subsidiary Kodiak Sciences GmbH entered into a funding agreement with Baker Bros. Advisors, LP (“BBA”), which holds more than 5% of the Company’s stock, pursuant to which BBA purchased the right to receive a capped 4.5% royalty on future net sales of KSI-301, the Company’s anti-VEGF antibody biopolymer conjugate therapy, in exchange for $225.0 million. Under the terms of the funding agreement, there is no obligation to repay any funding amount received, other than through the capped royalty payments on future product revenues. The Company recorded the funding amount paid by BBA as a liability on the consolidated balance sheet net of issuance costs , in accordance with ASC 730, Research and Development . Under ASC 730, the significant related party relationship between the Company and BBA creates an implicit obligation to repay the funding amount paid to the Company. Once royalty payments to BBA are determined to be probable and estimable, and if such amounts exceed the liability balance, the Company will impute interest to accrete the liability on a prospective basis based on such estimates. If and when the Company makes royalty payments under the funding agreement, it would reduce the liability balance at such time. Refer to Note 7. Credit Losses – Available-for-Sale Debt Securities For available-for-sale debt securities in an unrealized loss position, the Company will periodically assess its portfolio for impairment. The assessment first considers the intent or requirement to sell the security. If either of these criteria are met, the amortized cost basis will be written down to fair value through earnings. If not met, the Company will evaluate whether the decline resulted from credit losses or other factors by considering the extent to which fair value is less than amortized cost, any changes to the rating of the security by a rating agency, and any adverse conditions specifically related to the security, among other factors. If this assessment indicates that a credit loss exists, the present value of cash flows expected to be collected from the security is compared to the amortized cost basis of the security. If the present value of cash flows expected to be collected is less than the amortized cost basis, a credit loss exists and an allowance for credit losses will be recorded, limited by the amount that the fair value is less than the amortized cost basis. Any impairment that has not been recorded through an allowance for credit losses is recognized in other comprehensive income or loss, as applicable. Recent a p From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) ASC Recently Adopted Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Statements which intends to improve financial reporting by requiring earlier recognition of credit losses on certain financial assets, such as available-for-sale debt securities. The Company assessed the In August 2018, the FASB issued ASU 2018-13, Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurements Among the changes, entities will no longer be required to disclose the amount of and reasons for transfers between Levels 1 and 2 of the fair value hierarchy, but will be required to disclose the range and weighted average used to develop significant unobservable inputs for Level 3 fair value measurements. In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, New Accounting Pronouncements Not Yet Adopted In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes

Accrued and Other Current Liabi

Accrued and Other Current Liabilities	6 Months Ended
	Jun. 30, 2020
Accounts Payable And Accrued Liabilities Current [Abstract]
Accrued and Other Current Liabilities	3. Accrued and Other Current Liabilities Accrued and other current liabilities consist of the following (in thousands): June 30, 2020 December 31, 2019 Accrued research and development $ 8,353 $ 4,894 Accrued salaries and benefits 2,165 3,108 Accrued legal fees 246 302 Accrued professional fees 175 195 Accrued other liabilities 334 159 Total accrued and other current liabilities $ 11,273 $ 8,658

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	4. Fair Value Measurements The following tables present the Company’s fair value hierarchy for assets measured at fair value on a recurring basis (in thousands): Fair Value Measurements at June 30, 2020 Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 227,060 $ — $ — $ 227,060 Marketable securities: U.S. treasury securities — 60,410 — 60,410 Commercial paper — 43,877 — 43,877 Corporate notes — 43,011 — 43,011 Total $ 227,060 $ 147,298 $ — $ 374,358 Fair Value Measurements at December 31, 2019 Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 155,276 $ — $ — $ 155,276 Repurchase agreements 50,000 — — 50,000 Commercial paper — 5,987 — 5,987 Marketable securities: U.S. treasury securities — 50,185 — 50,185 Commercial paper — 34,533 — 34,533 Corporate notes — 51,662 — 51,662 Total $ 205,276 $ 142,367 $ — $ 347,643

Marketable Securities

Marketable Securities	6 Months Ended
	Jun. 30, 2020
Investments Debt And Equity Securities [Abstract]
Marketable Securities	5. Marketable Securities The marketable securities are classified as available-for-sale and consist of U.S. treasury securities, commercial paper and corporate notes. The fair value measurement data for marketable securities is obtained from independent pricing services. The Company validates the prices provided by the third-party pricing services by understanding the valuation methods and data sources used and analyzing the pricing data in certain instances. The following table summarizes the marketable securities held at June 30, 2020 and December 31, 2019 (in thousands): As of June 30, 2020 Amortized Cost Unrealized Gains Unrealized Losses Fair Value U.S. treasury securities $ 60,120 $ 290 $ — $ 60,410 Commercial paper 43,877 — — 43,877 Corporate notes 42,707 304 — 43,011 Total marketable securities, current $ 146,704 $ 594 $ — $ 147,298 As of December 31, 2019 Amortized Cost Unrealized Gains Unrealized Losses Fair Value U.S. treasury securities $ 50,190 $ — $ (5 ) $ 50,185 Commercial paper 34,532 1 — 34,533 Corporate notes 39,956 13 (3 ) 39,966 Total marketable securities, current $ 124,678 $ 14 $ (8 ) $ 124,684 Corporate notes $ 11,692 $ 4 $ — $ 11,696 Total marketable securities, noncurrent $ 11,692 $ 4 $ — $ 11,696 All marketable securities held at June 30, 2020 and December 31, 2019 had contractual maturities of less than 18 months

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	6. Commitments and Contingencies Leases As of June 30, 2020, the Company has a lease agreement for office and laboratory space at 2631 Hanover Street in Palo Alto, California through October 2023. In April 2020, the Company entered into a lease agreement for office and laboratory space at Rottenstrasse 5 in Visp, Switzerland. The space is approximately 1,000 square meters. The monthly rent during the initial 5-year term will be approximately 0.03 million Swiss Francs. In June 2020, the Company entered into lease agreements for two buildings at 1200 and 1250 Page Mill Road in Palo Alto, California, which are expected to serve as its corporate headquarters. The facilities are approximately 82,662 As of June 30, 2020, the Company did not have control of these spaces at Rottenstrasse 5 and 1200 and 1250 Page Mill Road and therefore, did not record right-of-use assets and corresponding lease liabilities. These commitments are not included in the below table. The maturities of the operating lease liabilities as of June 30, 2020 were as follows (in thousands): Year ending December 31, As of June 30, 2020 2020 $ 244 2021 $ 598 2022 $ 616 2023 $ 526 Total undiscounted lease payments $ 1,984 Less: imputed interest $ (259 ) Total operating lease liabilities $ 1,725 Other Commitments and Contingencies The Company has entered into service agreements with a variety of service providers, pursuant to which such service providers agreed to perform activities in connection with the manufacturing of certain materials. Such agreements, and related amendments, state that planned activities that are included in the signed work orders are, in some cases, binding and, hence, obligate the Company to pay the full price of the work order upon satisfactory delivery of products and services or obligate the Company to the binding amount regardless of whether such planned activities are in fact performed. Per the terms of the agreements, the Company has the option to cancel signed orders at any time upon written notice, which may or may not be subject to payment of a cancellation fee. The level of cancellation fees may be dependent on the timing of the written notice in relation to the commencement date of the work, with the maximum cancellation amount dependent on the agreement or the work order. As of June 30, 2020 and December 31, 2019, the total amount of cancelable and/or non-cancelable purchase obligations, including accrued amounts, under these agreements were $38.6 million and $4.7 million, respectively. Expense recognized under these agreements during the period, including amounts paid and accrued, for the three and six months ended June 30, 2020 were $3.5 million and $7.6 million, respectively, and for the three and six months ended June 30, 2019 were $2.4 million and $3.4 million, respectively. As of June 30, 2020, the Company had not incurred any cancellation fees. The Company has also entered into various cancellable license agreements for certain technology. The Company may be obligated to make payments on future sales of specified products associated with such license agreements. Such payments are dependent on future product sales and are not estimable. Legal Proceedings From time to time, the Company may become involved in legal proceedings arising from the ordinary course of its business. Management is currently not aware of any matters that could have a material adverse effect on the Company’s financial position, results of operations or cash flows. The Company records a legal liability when it believes that it is both probable that a liability may be imputed, and the amount of the liability can be reasonably estimated. Significant judgment by the Company is required to determine both probability and the estimated amount. Indemnification To the extent permitted under Delaware law, the Company has agreed to indemnify its directors and officers for certain events or occurrences while the director or officer is, or was serving, at the Company’s request in such capacity. The indemnification period covers all pertinent events and occurrences during the director’s or officer’s service. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is not specified in the agreements; however, the Company has director and officer insurance coverage that reduces its exposure and enables the Company to recover a portion of any future amounts paid. The Company believes the estimated fair value of these indemnification agreements in excess of applicable insurance coverage is minimal.

Liability Related to Sale of Fu

Liability Related to Sale of Future Royalties	6 Months Ended
	Jun. 30, 2020
Liability Related To Sale Of Future Royalties [Abstract]
Liability related to Sale of Future Royalties	7. Liability related to Sale of Future Royalties On December 1, 2019, the Company and its subsidiary Kodiak Sciences GmbH entered into a funding agreement with Baker Bros. Advisors, LP (“BBA”), which holds more than 5% of the Company’s stock, pursuant to which BBA purchased the right to receive a capped 4.5% royalty on future net sales of KSI-301, the Company’s anti-VEGF antibody biopolymer conjugate therapy, in exchange for $225.0 million. The royalty terminates upon the date that BBA has received an aggregate amount equal to 4.5 times the funding amount paid to the Company, unless earlier terminated or repurchased by the Company. Under the terms of the funding agreement, there is no obligation to repay any funding amount received, other than through the capped royalty payments on future product revenues. The Company has the option, exercisable at any point during the term of the funding agreement, to repurchase 100% of the royalties due to BBA for a purchase price equal to 4.5 times the funding amount paid to the Company as of such time, less amounts paid by the Company to BBA. The closing of the funding agreement was subject to certain conditions and occurred in February 2020. The Company received $100.0 million of the funding on February 4, 2020. The remaining $125.0 million shall be payable to the Company upon enrollment of 50% of the patients in the planned RVO clinical program. The Company recorded the initial $100.0 million payment as a liability on the consolidated balance sheet net of issuance costs , in accordance with ASC 730, Research and Development . Under ASC 730, the significant related party relationship between the Company and BBA creates an implicit obligation to repay the funding amount paid to the Company. Once royalty payments to BBA are determined to be probable and estimable, and if such amounts exceed the liability balance, the Company will impute interest to accrete the liability on a prospective basis based on such estimates. If and when the Company makes royalty payments under the funding agreement, it would reduce the liability balance at such time.

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	8. Stock-Based Compensation In January 2020 and 2019, the number of shares of common stock available for issuance under the 2018 Equity Incentive Plan was increased by approximately by 1.8 million and 1.5 million shares, respectively, as a result of the automatic increase provision in the 2018 Plan. Stock Options Stock option activity under the 2018 Plan and 2015 Equity Incentive Plan is summarized as follows: Number of Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2019 6,671,542 $ 25.22 8.73 $ 362,081 Granted 948,560 $ 53.78 Exercised (242,670 ) $ 3.65 Forfeited or canceled (73,144 ) $ 20.48 Outstanding at June 30, 2020 7,304,288 $ 23.01 8.51 $ 246,301 Restricted Shares Restricted share activity, including restricted stock awards, restricted stock units, and performance-based restricted stock units, under the 2018 Plan and 2015 Plan is summarized as follows: Number of Restricted Shares Weighted Average Grant Date Fair Value Unvested at December 31, 2019 160,747 $ 60.81 Granted 179,345 $ 49.52 Vested (12,789 ) $ 8.62 Shares withheld related to net share settlement of RSUs (4,058 ) $ 9.90 Canceled (4,250 ) $ 73.51 Unvested at June 30, 2020 318,995 $ 57.03 Performance-Based Stock Options and Restricted Stock Units The Company granted 170,150 performance-based stock options and 128,900 performance-based restricted stock units (“RSUs”) to employees in 2019. These performance-based equity awards will vest one-quarter None of these performance-based equity awards vested during 2019. The Company believes that the achievement of the requisite performance condition continues to be probable. Stock-based compensation expense recognized was $1.8 million and $3.6 million during the three and six months ended June 30, 2020, respectively, and none during the three and six months ended June 30, 2019, respectively. Stock-Based Compensation Expense Stock-based compensation for options and restricted shares is classified in the condensed consolidated statements of operations and comprehensive loss as follows (in thousands): Three Months Ended Six Months Ended June 30, June 30, 2020 2019 2020 2019 Research and development $ 3,776 $ 703 $ 7,224 $ 1,409 General and administrative 3,114 541 5,748 992 Total stock-based compensation $ 6,890 $ 1,244 $ 12,972 $ 2,401 As of June 30, 2020, the unrecognized stock-based compensation of unvested stock options, restricted stock units, and performance-based options and restricted stock units was $103.0 million and it is expected to be recognized over a weighted-average period of 3.48 years.

Net Loss per Common Share

Net Loss per Common Share	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Net Loss per Common Share	9. Net Loss per Common Share The following common share equivalents were excluded from the computation of diluted net loss per common share for the periods presented because their inclusion would have been antidilutive: As of June 30, 2020 2019 Outstanding stock options 7,304,288 5,468,167 Unvested restricted shares 318,995 16,320 Total 7,623,283 5,484,487

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The accompanying condensed consolidated financial statements are unaudited and have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) applicable to interim periods. The condensed consolidated financial statements These condensed consolidated financial statements have been prepared on a basis substantially consistent with, and should be read in conjunction with the audited financial statements for the year ended December 31, 2019 and notes thereto, included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (“SEC”) on March 16, 2020. Certain information and note disclosures normally included in the audited financial statements prepared in accordance with GAAP have been condensed or omitted from this report. The results of operations for any interim period are not necessarily indicative of the results for the year ending December 31, 2020, or for any future period. The accompanying condensed consolidated financial statements reflect the operations of the Company and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated.
Reclassification	Reclassification Certain prior period amounts have been reclassified to conform to the current period presentation. Such reclassifications had no impact on subtotals in the prior year condensed consolidated financial statements.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities as of the date of the condensed consolidated financial statements and expenses during the reporting period. The impact of the ongoing COVID-19 pandemic continues to evolve. As a result, certain estimates and assumptions required increased judgment and carried a higher degree of variability and volatility, including but not limited to, the fair value of marketable securities, performance-based equity awards, and research and development accruals for the three and six months ended June 30, 2020. As events continue to unfold and additional information becomes available, these estimates may change materially in future periods. Actual results could differ from those estimates.
Risks and Uncertainties	Risks and Uncertainties In March 2020, the World Health Organization declared a pandemic due to the global COVID-19 outbreak. The significant uncertainties caused by the ongoing COVID-19 pandemic may negatively impact the Company’s operations, liquidity, and capital resources, and will depend on certain evolving developments, including the duration and spread of the outbreak, regulatory and private sector responses and the impact on employees and vendors including supply chain and clinical partners, all of which are uncertain and cannot be predicted. During this pandemic, the Company continues to work closely with clinical sites towards maximal patient safety and the lowest number of missed visits and study discontinuations. The Company has taken and continues to take proactive measures to maintain the integrity of its ongoing clinical studies. Despite these efforts, the ongoing COVID-19 pandemic could significantly impact clinical trial enrollment and completion of its clinical studies. The Company will continue to monitor the COVID-19 situation and its impact on the ability to continue the development of, and seek regulatory approvals for, the Company’s product candidates, and begin to commercialize any approved products.
Liability related to Sale of Future Royalties	Liability related to Sale of Future Royalties On December 1, 2019, the Company and its subsidiary Kodiak Sciences GmbH entered into a funding agreement with Baker Bros. Advisors, LP (“BBA”), which holds more than 5% of the Company’s stock, pursuant to which BBA purchased the right to receive a capped 4.5% royalty on future net sales of KSI-301, the Company’s anti-VEGF antibody biopolymer conjugate therapy, in exchange for $225.0 million. Under the terms of the funding agreement, there is no obligation to repay any funding amount received, other than through the capped royalty payments on future product revenues. The Company recorded the funding amount paid by BBA as a liability on the consolidated balance sheet net of issuance costs , in accordance with ASC 730, Research and Development . Under ASC 730, the significant related party relationship between the Company and BBA creates an implicit obligation to repay the funding amount paid to the Company. Once royalty payments to BBA are determined to be probable and estimable, and if such amounts exceed the liability balance, the Company will impute interest to accrete the liability on a prospective basis based on such estimates. If and when the Company makes royalty payments under the funding agreement, it would reduce the liability balance at such time. Refer to Note 7.
Credit Losses – Available-for-Sale Debt Securities	Credit Losses – Available-for-Sale Debt Securities For available-for-sale debt securities in an unrealized loss position, the Company will periodically assess its portfolio for impairment. The assessment first considers the intent or requirement to sell the security. If either of these criteria are met, the amortized cost basis will be written down to fair value through earnings. If not met, the Company will evaluate whether the decline resulted from credit losses or other factors by considering the extent to which fair value is less than amortized cost, any changes to the rating of the security by a rating agency, and any adverse conditions specifically related to the security, among other factors. If this assessment indicates that a credit loss exists, the present value of cash flows expected to be collected from the security is compared to the amortized cost basis of the security. If the present value of cash flows expected to be collected is less than the amortized cost basis, a credit loss exists and an allowance for credit losses will be recorded, limited by the amount that the fair value is less than the amortized cost basis. Any impairment that has not been recorded through an allowance for credit losses is recognized in other comprehensive income or loss, as applicable.
Recent Accounting Pronouncements	Recent a p From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) ASC Recently Adopted Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Statements which intends to improve financial reporting by requiring earlier recognition of credit losses on certain financial assets, such as available-for-sale debt securities. The Company assessed the In August 2018, the FASB issued ASU 2018-13, Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurements Among the changes, entities will no longer be required to disclose the amount of and reasons for transfers between Levels 1 and 2 of the fair value hierarchy, but will be required to disclose the range and weighted average used to develop significant unobservable inputs for Level 3 fair value measurements. In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, New Accounting Pronouncements Not Yet Adopted In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes

Accrued and Other Current Lia_2

Accrued and Other Current Liabilities (Tables)	6 Months Ended
	Jun. 30, 2020
Accounts Payable And Accrued Liabilities Current [Abstract]
Schedule of Accrued and Other Current Liabilities	Accrued and other current liabilities consist of the following (in thousands): June 30, 2020 December 31, 2019 Accrued research and development $ 8,353 $ 4,894 Accrued salaries and benefits 2,165 3,108 Accrued legal fees 246 302 Accrued professional fees 175 195 Accrued other liabilities 334 159 Total accrued and other current liabilities $ 11,273 $ 8,658

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Summary of Fair Value Hierarchy for Assets Measured at Fair Value on Recurring Basis	The following tables present the Company’s fair value hierarchy for assets measured at fair value on a recurring basis (in thousands): Fair Value Measurements at June 30, 2020 Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 227,060 $ — $ — $ 227,060 Marketable securities: U.S. treasury securities — 60,410 — 60,410 Commercial paper — 43,877 — 43,877 Corporate notes — 43,011 — 43,011 Total $ 227,060 $ 147,298 $ — $ 374,358 Fair Value Measurements at December 31, 2019 Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ 155,276 $ — $ — $ 155,276 Repurchase agreements 50,000 — — 50,000 Commercial paper — 5,987 — 5,987 Marketable securities: U.S. treasury securities — 50,185 — 50,185 Commercial paper — 34,533 — 34,533 Corporate notes — 51,662 — 51,662 Total $ 205,276 $ 142,367 $ — $ 347,643

Marketable Securities (Tables)

Marketable Securities (Tables)	6 Months Ended
	Jun. 30, 2020
Investments Debt And Equity Securities [Abstract]
Summary of Marketable Securities Held	The following table summarizes the marketable securities held at June 30, 2020 and December 31, 2019 (in thousands): As of June 30, 2020 Amortized Cost Unrealized Gains Unrealized Losses Fair Value U.S. treasury securities $ 60,120 $ 290 $ — $ 60,410 Commercial paper 43,877 — — 43,877 Corporate notes 42,707 304 — 43,011 Total marketable securities, current $ 146,704 $ 594 $ — $ 147,298 As of December 31, 2019 Amortized Cost Unrealized Gains Unrealized Losses Fair Value U.S. treasury securities $ 50,190 $ — $ (5 ) $ 50,185 Commercial paper 34,532 1 — 34,533 Corporate notes 39,956 13 (3 ) 39,966 Total marketable securities, current $ 124,678 $ 14 $ (8 ) $ 124,684 Corporate notes $ 11,692 $ 4 $ — $ 11,696 Total marketable securities, noncurrent $ 11,692 $ 4 $ — $ 11,696

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2020
Commitments And Contingencies Disclosure [Abstract]
Summary of Maturities of Operating Lease Liabilities	The maturities of the operating lease liabilities as of June 30, 2020 were as follows (in thousands): Year ending December 31, As of June 30, 2020 2020 $ 244 2021 $ 598 2022 $ 616 2023 $ 526 Total undiscounted lease payments $ 1,984 Less: imputed interest $ (259 ) Total operating lease liabilities $ 1,725

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Options Activity under 2018 Plan and 2015 Equity Incentive Plan	Stock option activity under the 2018 Plan and 2015 Equity Incentive Plan is summarized as follows: Number of Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2019 6,671,542 $ 25.22 8.73 $ 362,081 Granted 948,560 $ 53.78 Exercised (242,670 ) $ 3.65 Forfeited or canceled (73,144 ) $ 20.48 Outstanding at June 30, 2020 7,304,288 $ 23.01 8.51 $ 246,301
Summary of Restricted Shares	Restricted share activity, including restricted stock awards, restricted stock units, and performance-based restricted stock units, under the 2018 Plan and 2015 Plan is summarized as follows: Number of Restricted Shares Weighted Average Grant Date Fair Value Unvested at December 31, 2019 160,747 $ 60.81 Granted 179,345 $ 49.52 Vested (12,789 ) $ 8.62 Shares withheld related to net share settlement of RSUs (4,058 ) $ 9.90 Canceled (4,250 ) $ 73.51 Unvested at June 30, 2020 318,995 $ 57.03
Summary of Stock-based Compensation for Options and Restricted Shares Classified in Condensed Consolidated Statements of Operations and Comprehensive Loss	Stock-based compensation for options and restricted shares is classified in the condensed consolidated statements of operations and comprehensive loss as follows (in thousands): Three Months Ended Six Months Ended June 30, June 30, 2020 2019 2020 2019 Research and development $ 3,776 $ 703 $ 7,224 $ 1,409 General and administrative 3,114 541 5,748 992 Total stock-based compensation $ 6,890 $ 1,244 $ 12,972 $ 2,401

Net Loss per Common Share (Tabl

Net Loss per Common Share (Tables)	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Summary of Anti-dilutive Securities Excluded from Computation of Diluted Net Loss per Common Share	The following common share equivalents were excluded from the computation of diluted net loss per common share for the periods presented because their inclusion would have been antidilutive: As of June 30, 2020 2019 Outstanding stock options 7,304,288 5,468,167 Unvested restricted shares 318,995 16,320 Total 7,623,283 5,484,487

The Company - Additional Inform

The Company - Additional Information (Details) $ in Millions	Jun. 30, 2020USD ($)
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Cash and cash equivalents and marketable securities	$ 417.1

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	Dec. 01, 2019	Jun. 30, 2020	Feb. 04, 2020	Dec. 31, 2019
Summary of Significant Accounting Policies [Line Items]
Allowance for credit losses for available-for-sale debt securities		$ 0		$ 0
ASU 2016-13
Summary of Significant Accounting Policies [Line Items]
Allowance for credit losses for available-for-sale debt securities		$ 0
Baker Bros. Advisors LP | Funding Agreement
Summary of Significant Accounting Policies [Line Items]
Capped percentage of royalty on future net sales	4.50%
Amount under funding agreement	$ 225,000,000		$ 100,000,000
Baker Bros. Advisors LP | Minimum | Funding Agreement
Summary of Significant Accounting Policies [Line Items]
Ownership percentage threshold	5.00%

Accrued and Other Current Lia_3

Accrued and Other Current Liabilities - Schedule of Accrued and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Accounts Payable And Accrued Liabilities Current [Abstract]
Accrued research and development	$ 8,353	$ 4,894
Accrued salaries and benefits	2,165	3,108
Accrued legal fees	246	302
Accrued professional fees	175	195
Accrued other liabilities	334	159
Total accrued and other current liabilities	$ 11,273	$ 8,658

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Fair Value Hierarchy for Assets Measured at Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	$ 374,358	$ 347,643
Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	227,060	155,276
U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	60,410	50,185
Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		5,987
Marketable securities	43,877	34,533
Corporate Notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	43,011	51,662
Repurchase Agreements
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		50,000
Quoted Price in Active Markets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	227,060	205,276
Quoted Price in Active Markets (Level 1) | Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	227,060	155,276
Quoted Price in Active Markets (Level 1) | U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	0	0
Quoted Price in Active Markets (Level 1) | Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		0
Marketable securities	0	0
Quoted Price in Active Markets (Level 1) | Corporate Notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	0	0
Quoted Price in Active Markets (Level 1) | Repurchase Agreements
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		50,000
Significant Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	147,298	142,367
Significant Observable Inputs (Level 2) | Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Significant Observable Inputs (Level 2) | U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	60,410	50,185
Significant Observable Inputs (Level 2) | Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		5,987
Marketable securities	43,877	34,533
Significant Observable Inputs (Level 2) | Corporate Notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	43,011	51,662
Significant Observable Inputs (Level 2) | Repurchase Agreements
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		0
Significant Unobservable Inputs (Level 3)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	0	0
Significant Unobservable Inputs (Level 3) | Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Significant Unobservable Inputs (Level 3) | U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	0	0
Significant Unobservable Inputs (Level 3) | Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		0
Marketable securities	0	0
Significant Unobservable Inputs (Level 3) | Corporate Notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	$ 0	0
Significant Unobservable Inputs (Level 3) | Repurchase Agreements
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents		$ 0

Marketable Securities - Summary

Marketable Securities - Summary of Marketable Securities Held (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Marketable Securities [Line Items]
Amortized Cost, current	$ 146,704	$ 124,678
Unrealized Gains, current	594	14
Unrealized Losses, current		(8)
Fair Value, current	147,298	124,684
Amortized Cost, noncurrent		11,692
Unrealized Gains, noncurrent		4
Fair Value, noncurrent		11,696
U.S. Treasury Securities
Marketable Securities [Line Items]
Amortized Cost, current	60,120	50,190
Unrealized Gains, current	290
Unrealized Losses, current		(5)
Fair Value, current	60,410	50,185
Commercial Paper
Marketable Securities [Line Items]
Amortized Cost, current	43,877	34,532
Unrealized Gains, current		1
Fair Value, current	43,877	34,533
Corporate Notes
Marketable Securities [Line Items]
Amortized Cost, current	42,707	39,956
Unrealized Gains, current	304	13
Unrealized Losses, current		(3)
Fair Value, current	$ 43,011	39,966
Amortized Cost, noncurrent		11,692
Unrealized Gains, noncurrent		4
Fair Value, noncurrent		$ 11,696

Marketable Securities - Additio

Marketable Securities - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Marketable Securities [Line Items]
Realized gains or losses recognized on sale or maturity of available-for-sale debt securities	$ 0	$ 0	$ 0	$ 0
Allowance for credit losses for available-for-sale debt securities	0		0		$ 0
Impairment charges or recoveries related to marketable securities	$ 0	$ 0	$ 0	$ 0
Maximum
Marketable Securities [Line Items]
Marketable securities, contractual maturities	18 months		18 months		18 months

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) SFr in Thousands, m² in Millions, ft² in Millions	1 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2020USD ($)ft²Building	Apr. 30, 2020CHF (SFr)m²	Jun. 30, 2020USD ($)ft²	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)ft²	Jun. 30, 2019USD ($)	Dec. 31, 2019USD ($)
Commitments And Contingencies Disclosure [Line Items]
Operating lease right-of-use asset	$ 1,591,000		$ 1,591,000		$ 1,591,000		$ 1,790,000
Lease liabilities	1,725,000		1,725,000		1,725,000
Lonza | Service Agreements
Commitments And Contingencies Disclosure [Line Items]
Cancelable and/ or non-cancelable purchase obligations, total	$ 38,600,000		38,600,000		38,600,000		$ 4,700,000
Unrecorded unconditional purchase obligation, expenses recognized			$ 3,500,000	$ 2,400,000	7,600,000	$ 3,400,000
Unrecorded unconditional purchase obligation, cancellation fees					$ 0
Lease Agreement on April 2020 | Rottenstrasse 5 in Visp | Switzerland
Commitments And Contingencies Disclosure [Line Items]
Lease area | m²		1,000
Initial lease term		5 years
Monthly rent expense | SFr		SFr 30
Lease Agreement on June 2020 | California
Commitments And Contingencies Disclosure [Line Items]
Number of buildings leased | Building	2
Lease Agreement on June 2020 | 1200 Page Mill Road in Palo Alto | California
Commitments And Contingencies Disclosure [Line Items]
Lease area | ft²	82,662		82,662		82,662
Initial lease term	6 years 6 months
Monthly rent expense	$ 600,000
Annual rent year-over-year increase percentage	3.00%
Total rent abatement	$ 7,200,000
Lease Agreement on June 2020 | 1250 Page Mill Road in Palo Alto | California
Commitments And Contingencies Disclosure [Line Items]
Lease area | ft²	72,812		72,812		72,812
Initial lease term	13 years
Monthly rent expense	$ 500,000
Annual rent year-over-year increase percentage	3.00%
Total rent abatement	$ 6,300,000
Lease Agreement on April and June 2020
Commitments And Contingencies Disclosure [Line Items]
Operating lease right-of-use asset	0		$ 0		$ 0
Lease liabilities	$ 0		$ 0		$ 0

Commitments and Contingencies_2

Commitments and Contingencies -Summary of Maturities of Operating Lease Liabilities (Details) $ in Thousands	Jun. 30, 2020USD ($)
Operating Lease
2020	$ 244
2021	598
2022	616
2023	526
Total undiscounted lease payments	1,984
Less: imputed interest	(259)
Total operating lease liabilities	$ 1,725

Liability Related to Sale of _2

Liability Related to Sale of Future Royalties - Additional Information (Details) - USD ($) $ in Thousands	Dec. 01, 2019	Jun. 30, 2020	Feb. 29, 2020	Feb. 04, 2020
Related Party Transaction [Line Items]
Liability related to sale of future royalties		$ 99,863
Baker Bros. Advisors LP | Funding Agreement
Related Party Transaction [Line Items]
Capped percentage of royalty on future net sales	4.50%
Amount under funding agreement	$ 225,000			$ 100,000
Percentage of repurchase of royalties	100.00%
Funds to be payable upon enrollment of patients			$ 125,000
Percentage of patients to be enrolled			50.00%
Liability related to sale of future royalties		$ 100,000
Baker Bros. Advisors LP | Minimum | Funding Agreement
Related Party Transaction [Line Items]
Ownership percentage threshold	5.00%

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense recognized			$ 6,890,000	$ 1,244,000	$ 12,972,000	$ 2,401,000
Unrecognized stock-based compensation expense			103,000,000		$ 103,000,000
Unrecognized stock-based compensation weighted-average period expected for recognition					3 years 5 months 23 days
Performance-based Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options, granted							170,150
Performance-based Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock units, granted							128,900
Performance Based Equity Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period							3 months
Awards vested							0
Stock-based compensation expense recognized			$ 1,800,000	$ 0	$ 3,600,000	$ 0
2018 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of common stock available for issuance increased	1,800,000	1,500,000

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Options Activity Under 2018 Plan and 2015 Equity Incentive Plan (Details) - 2018 Plan and 2015 Equity Incentive Plan - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Number of Options
Beginning balance	6,671,542
Granted	948,560
Exercised	(242,670)
Forfeited or canceled	(73,144)
Ending balance	7,304,288	6,671,542
Weighted Average Exercise Price
Beginning balance	$ 25.22
Granted	53.78
Exercised	3.65
Forfeited or canceled	20.48
Ending balance	$ 23.01	$ 25.22
Weighted Average Remaining Contractual Term (in years)
Weighted Average Remaining Contractual Term (in years)	8 years 6 months 3 days	8 years 8 months 23 days
Aggregate Intrinsic Value
Beginning balance	$ 362,081
Ending balance	$ 246,301	$ 362,081

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Restricted Shares (Details) - Restricted Shares	6 Months Ended
	Jun. 30, 2020$ / sharesshares
Number of Restricted Shares
Unvested, beginning balance | shares	160,747
Granted | shares	179,345
Vested | shares	(12,789)
Shares withheld related to net share settlement of RSUs | shares	(4,058)
Canceled | shares	(4,250)
Unvested, ending balance | shares	318,995
Weighted Average Grant Date Fair Value
Unvested, beginning balance | $ / shares	$ 60.81
Granted | $ / shares	49.52
Vested | $ / shares	8.62
Shares withheld related to net share settlement of RSUs | $ / shares	9.90
Canceled | $ / shares	73.51
Unvested, ending balance | $ / shares	$ 57.03

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Stock-based Compensation for Options and Restricted Shares Classified in Condensed Consolidated Statements of Operations and Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 6,890	$ 1,244	$ 12,972	$ 2,401
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	3,776	703	7,224	1,409
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 3,114	$ 541	$ 5,748	$ 992

Net Loss per Common Share - Sum

Net Loss per Common Share - Summary of Anti-dilutive Securities Excluded from Computation of Diluted Net Loss per Common Share (Details) - shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted net loss per common share	7,623,283	5,484,487
Outstanding Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted net loss per common share	7,304,288	5,468,167
Unvested Restricted Shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted net loss per common share	318,995	16,320