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Consolidated Statements of Cash Flows - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES |  |  |
Net loss | $ (66,150) | $ (77,187) | $ (38,924)
Adjustments to reconcile net loss to net cash used in operating activities: |  |  |
Stock-based compensation | 7,899 | 8,353 | 6,919
Operating lease right-of-use asset amortization | 1,775 | 1,792 |
Depreciation and amortization | 789 | 703 | 527
Loss on early repayment of debt | 585 |  |
Net amortization of premium (accretion of discount) on marketable securities | 37 | (594) | 206
Amortization of debt issuance costs and accretion of debt discount | 159 | 29 |
Gain on disposal of property and equipment |  | 8 |
Change in deferred tax asset | 1,438 | (775) | (658)
Changes in operating assets and liabilities: |  |  |
Research and development tax incentive receivable | (990) | 1,411 | (236)
Receivable from collaboration partner - related party | 4,329 | (2,168) | (2,771)
Prepaid expenses and other assets | (1,102) | (2,820) | 1,117
Accounts payable | 309 | (3,000) | 4,430
Payable to collaboration partner - related party | 1,471 | 201 | 1,061
Accrued expenses and other payables | 5,840 | 1,098 | 1,911
Deferred revenue - related party | (27,053) | 33,307 | (23,529)
Operating lease liability | (1,941) | (1,885) |
Other liability | 121 |  |
Net cash used in operating activities | (72,484) | (41,527) | (49,947)
CASH FLOWS FROM INVESTING ACTIVITIES |  |  |
Purchase of marketable securities | (280,027) | (166,936) | (71,060)
Proceeds from maturities of marketable securities | 189,533 | 114,193 | 73,759
Purchases of property and equipment | (471) | (967) | (486)
Net cash (used in) provided by investing activities | (90,965) | (53,710) | 2,213
CASH FLOWS FROM FINANCING ACTIVITIES |  |  |
Proceeds from public offering of common stock, net of issuance costs | 213,303 |  |
Proceeds from issuance of common stock and warrants in private placement, net of issuance costs |  |  | 21,673
Proceeds from at-the-market offering, net of issuance costs | 42,062 | 34,492 | 1,508
Proceeds from issuance of common stock upon exercise of stock options and purchases under employee stock purchase plan | 2,799 | 1,779 | 934
Proceeds from issuance of long-term debt, net of issuance costs |  | 9,765 |
Issuance costs related to long-term debt | (14) |  |
Early repayment of long-term debt | (10,524) |  |
Net cash provided by financing activities | 247,626 | 46,036 | 24,115
Effect of exchange rate changes on cash, cash equivalents and restricted cash | 175 | (26) | (177)
Net increase (decrease) in cash, cash equivalents and restricted cash | 84,352 | (49,227) | (23,796)
Cash, cash equivalents and restricted cash, beginning of period | 33,466 | 82,693 | 106,489
Cash, cash equivalents and restricted cash, end of period | 117,818 | 33,466 | 82,693
SUPPLEMENTAL DISCLOSURE OF NON-CASH FINANCING AND INVESTING INFORMATION: |  |  |
Cash paid for interest | 438 | 70 |
SUPPLEMENTAL DISCLOSURE OF NON-CASH FINANCING AND INVESTING INFORMATION: |  |  |
Purchases of property and equipment in accounts payable and accrued liabilities | 85 | 100 | 24
Fair value of common stock retired in exchange for issuance of common stock warrant |  |  | $ 6,670
Public Offering | Accrued liabilities and other payables |  |  |
SUPPLEMENTAL DISCLOSURE OF NON-CASH FINANCING AND INVESTING INFORMATION: |  |  |
Issuance costs related to common stock | 205 | $ 80 |
Public Offering | Prepaid expenses and other assets |  |  |
SUPPLEMENTAL DISCLOSURE OF NON-CASH FINANCING AND INVESTING INFORMATION: |  |  |
Issuance costs related to common stock | 124 |  |
At-the-market offering | Prepaid expenses and other assets |  |  |
SUPPLEMENTAL DISCLOSURE OF NON-CASH FINANCING AND INVESTING INFORMATION: |  |  |
Issuance costs related to common stock | $ 191 |  |

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