BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 76,117	$ 22,860
Investments, short-term	59,608	126,605
Accounts receivable, net of allowance for credit losses of $35 and $48, respectively	11,032	13,131
Inventories	7,245	5,834
Prepaid expenses and other current assets	1,429	2,206
Total current assets	155,431	170,636
Investments, long-term	6,139	6,276
Property and equipment, net	3,113	3,045
Operating lease right-of-use asset	672	915
Other non-current asset	381	381
Total assets	165,736	181,253
Current liabilities:
Accounts payable	5,821	4,459
Accrued expenses	7,896	12,397
Total current liabilities	13,717	16,856
Notes payable	24,576	24,522
Other non-current liability	40	40
Total liabilities	38,333	41,418
Stockholders' equity:
Preferred Stock, $0.001 par value, 10,000,000 shares authorized; no shares issued and outstanding at March 31, 2020 and December 31, 2019	0	0
Common Stock, $0.001 par value per share; 200,000,000 shares authorized at March 31, 2020 and December 31, 2019; 24,362,389 and 24,107,350 issued and outstanding at March 31, 2020 and December 31, 2019, respectively	24	24
Additional paid-in capital	323,473	319,865
Accumulated other comprehensive income	295	102
Accumulated deficit	(196,389)	(180,156)
Total stockholders' equity	127,403	139,835
Total liabilities and stockholders' equity	$ 165,736	$ 181,253