CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 62,260	$ 74,867
Short term investments	41,894	53,240
Accounts receivable	6,787	2,701
Prepaid expenses and other current assets	4,072	4,574
Total current assets	115,013	135,382
Property and equipment, net	19,502	5,049
Operating lease right-of-use assets	3,436	0
Other non-current assets	3,146	910
Total assets	141,097	141,341
Current liabilities:
Accounts payable	5,803	3,350
Accrued expenses and other current liabilities	9,944	9,114
Deferred revenues, current portion	11,256	35,612
Total current liabilities	27,003	48,076
Deferred revenue, net of current portion	47,258	53,303
Operating lease liabilities	15,484	0
Other long-term liabilities	0	27
Total liabilities	89,745	101,406
Stockholders’ equity:
Common stock, $0.001 par value per share, 300,000,000 shares authorized and 55,212,437 and 54,151,219 issued and outstanding at December 31, 2019 and 2018, respectively	55	54
Additional paid-in capital	227,468	189,929
Accumulated other comprehensive loss	(1,995)	(2,982)
Accumulated deficit	(174,176)	(147,066)
Total stockholders’ equity	51,352	39,935
Total liabilities and stockholders’ equity	141,097	141,341
Series A Convertible Preferred Stock
Stockholders’ equity:
Preferred stock, $0.001 par value per share, 10,000,000 shares authorized at December 31, 2019 and 2018, respectively	0	0
Series B Convertible Preferred Stock
Stockholders’ equity:
Preferred stock, $0.001 par value per share, 10,000,000 shares authorized at December 31, 2019 and 2018, respectively	0	0
Series C Convertible Preferred Stock
Stockholders’ equity:
Preferred stock, $0.001 par value per share, 10,000,000 shares authorized at December 31, 2019 and 2018, respectively	$ 0	$ 0