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Summary of Significant Accounting Policies (Tables) | 12 Months Ended
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Dec. 31, 2019
Accounting Policies [Abstract] |
Summary of Fair Value Measurement Financial Assets | Financial assets measured at fair value on a recurring basis were as follows (in thousands):
| Fair Value Measurement at December 31, 2019 |  |  |  |  |  |
|  |  | Quoted Prices in Active Markets for Identical Assets |  | Significant Other Observable Inputs |  | Significant Unobservable Inputs
| Total |  | Level 1 |  | Level 2 |  | Level 3
Assets: |  |  |  |  |  |  |
Money market funds | $ | 46,149 |  |  | $ | 46,149 |  |  | $ | — |  |  | $ | — |
Government-sponsored enterprises | 13,222 |  |  | — |  |  | 13,222 |  |  | — |
Corporate debt securities | 103,135 |  |  | — |  |  | 103,135 |  |  | — |
Total assets measured at fair value (a) | $ | 162,506 |  |  | $ | 46,149 |  |  | $ | 116,357 |  |  | $ | — |
| Fair Value Measurement at December 31, 2018 |  |  |  |  |  |
|  |  | Quoted Prices in Active Markets for Identical Assets |  | Significant Other Observable Inputs |  | Significant Unobservable Inputs
| Total |  | Level 1 |  | Level 2 |  | Level 3
Assets: |  |  |  |  |  |  |
Money market funds | $ | 46,257 |  |  | $ | 46,257 |  |  | $ | — |  |  | $ | — |
U.S Treasury securities | 12,488 |  |  | — |  |  | 12,488 |  |  | — |
Corporate debt securities | 100,214 |  |  | — |  |  | 100,214 |  |  | — |
Common stock warrants | 1,890 |  |  | — |  |  | — |  |  | $ | 1,890 |
Total assets measured at fair value (b) | $ | 160,849 |  |  | $ | 46,257 |  |  | $ | 112,702 |  |  | $ | 1,890 |
(a) Total assets measured at fair value at December 31, 2019 includes approximately $73.2 million reported in cash and cash equivalents on the balance sheet. (b) Total assets measured at fair value at December 31, 2018 includes approximately $146.2 million reported in cash and cash equivalents on the balance sheet.
Summary of Percentage of Customer Concentration | The following table includes those collaborators that represent more than 10% of total revenue earned in the periods indicated:
| Year Ended December 31, |  |  |  |
| 2019 |  | 2018 |  | 2017
Incyte Corporation (Incyte) | 35% |  |  | 68% |  |  | 96% |
Zai Lab Limited (Zai Lab) | 29% |  |  | * |  |  | * |
Les Laboratoires Servier and Institut de Recherches Servier (Servier) | 18% |  |  | * |  |  | * |
* Balance is less than 10% The following table includes those counterparties that represent more than 10% of accounts receivable at the date indicated:
| December 31, |  |
| 2019 |  | 2018
Incyte | 62% |  |  | 16% |
Zai Lab | 23% |  |  | 76% |
Estimated Useful Lives | Depreciation and amortization are computed using the straight-line method over the following estimated useful lives:
Computer equipment | 3 years
Software | 3 years
Furniture | 10 years
Laboratory and office equipment | 5 years
Leasehold improvements | Shorter of lease term or useful life
Schedule of Stock Options and RSUs Excluded from the Calculation of Net Loss Per Share | The following table presents the number of stock options and RSUs that were excluded from the calculation of net loss per share:
| Year Ended December 31, |  |  |  |
| 2019 |  | 2018 |  | 2017
Stock options and RSUs | 7,159,494 |  |  |  | 5,273,964 |  |  |  | 4,504,642 |
Schedule of New Accounting Pronouncements and Changes in Accounting Principles | As a result of applying the modified retrospective method to adopt the new guidance, the following adjustments were made to accounts on the consolidated balance sheet as of January 1, 2018 (in thousands):
| Pre-Adoption |  | ASC 606 Adjustment |  | Post-Adoption
Deferred revenue, current | $ | 7,202 |  |  | $ | 540 |  |  | $ | 7,742 |
Deferred revenue, net of current portion | 13,637 |  |  | 5,939 |  |  | 19,576 |
Accumulated deficit | (312,340) |  |  | (6,478) |  |  | (318,818) |
The transition adjustment resulted primarily from changes in the pattern of revenue recognition for upfront fees and license grant fees. The following table shows the impact of adoption to the consolidated statement of income and balance sheet (in thousands):
| Year Ended December 31, 2018 |  |  |  |
| As Reported |  | Balances Without Adoption of ASC 606 |  | Effect of Change Higher/(Lower)
Revenue from collaborative agreements | $ | 58,644 |  |  | $ | 58,104 |  |  | $ | 540 |
Net loss | (171,453) |  |  | (171,993) |  |  | (540) |
Basic and diluted net loss per common share | $ | (4.19) |  |  | $ | (4.20) |  |  | $ | 0.01 |
| As of December 31, 2018 |  |  |  |
| As Reported |  | Balances Without Adoption of ASC 606 |  | Effect of Change Higher/(Lower)
Deferred revenue, current | $ | 21,721 |  |  | $ | 22,210 |  |  | $ | (489) |
Deferred revenue, net of current portion | 19,001 |  |  | 12,573 |  |  | 6,428 |
Accumulated deficit | (490,271) |  |  | $ | (484,332) |  |  | $ | (5,939) |
Rollforward of Contract Liabilities | The following table presents changes in the Company’s contract liabilities during the year ended December 31, 2018 (in thousands):
| Balance at Beginning of Period |  | Additions |  | Deductions |  | Balance at End of Period
Deferred revenue (current and non-current) | $ | 27,318 |  |  | $ | 22,992 |  |  | $ | (9,588) |  |  | $ | 40,722 |

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