Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 89,195	$ 111,355
Investments	151,366	94,375
Prepaid expenses and other assets	5,030	3,358
Total current assets	245,591	209,088
Property and equipment, net	19,270	2,027
Goodwill	30,815	30,815
Restricted cash	1,525	1,436
Deposits	455	545
Operating lease right-of-use assets	2,254	0
Investments	0	7,402
Total assets	299,910	251,313
Current liabilities:
Accounts payable and accrued expenses	21,246	15,372
Operating lease liabilities, current	935	0
Total current liabilities	22,181	15,372
Convertible notes, net of unamortized discount	44,097	41,447
Operating lease liabilities, non-current	1,691	0
Other liabilities	23	457
Total liabilities	67,992	57,276
Commitments and contingencies (Note 11)
Stockholders' equity:
Common stock, $0.01 par value, 120,000,000 shares authorized; 50,376,030 and 45,194,736 shares issued at September 30, 2019 and December 31, 2018, respectively	503	452
Treasury stock, at cost, 22,308 and 50,000 common shares at September 30, 2019 and December 31, 2018, respectively	(344)	(668)
Additional paid-in capital	394,930	300,253
Accumulated other comprehensive income (loss)	117	(127)
Accumulated deficit	(163,288)	(105,873)
Total stockholders' equity	231,918	194,037
Total liabilities and stockholders' equity	299,910	251,313
Series A Convertible Preferred Shares [Member]
Stockholders' equity:
Preferred shares	0	0
Series B Convertible Preferred Shares [Member]
Stockholders' equity:
Preferred shares	$ 0	$ 0