CONDENSED CONSOLIDATED BALANCE SHEETS (unaudited) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 25,042	$ 55,046
Short-term investments	80,191	73,243
Accounts receivable, net	5,375	3,300
Inventory and other deferred costs	6,524	4,606
Prepaid expenses and other current assets	2,989	3,383
Total current assets	120,121	139,578
Property and equipment, net	12,650	14,106
Operating lease right-of-use assets	10,991	1,845
Other long-term assets	1,760	1,762
Total assets	145,522	157,291
Current liabilities
Accounts payable	7,491	7,337
Accrued and other current liabilities	6,594	6,648
Contract liabilities	28,952	35,977
Total current liabilities	43,037	49,962
Long-term operating lease liabilities	9,233	639
Other long-term liabilities	129
Total liabilities	52,399	50,601
Commitments and Contingencies (Note 12)
Stockholders’ equity
Common stock, $0.0001 par value — 200,000,000 shares authorized; 31,872,122 and 31,243,029 shares issued and outstanding at June 30, 2020 and December 31, 2019, respectively	3	3
Additional paid-in capital	251,997	247,282
Accumulated other comprehensive income (loss)	106	(6)
Accumulated deficit	(158,983)	(140,589)
Total stockholders’ equity	93,123	106,690
Total liabilities and stockholders’ equity	$ 145,522	$ 157,291