Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 58,666	$ 102,003
Short-term investments	15,253	225
Other receivables	4,766	3,871
Contract asset		1,500
Prepaid expenses	1,403	1,154
Total current assets	80,088	108,753
Property, plant and equipment, net	2,761	1,139
Intangible assets, net	86	98
Long-term receivables	710	428
Total assets	83,645	110,418
Current liabilities:
Accounts payable	2,914	3,304
Accrued expense and other current liabilities	11,202	14,502
Total current liabilities	14,116	17,806
Non-current liabilities
Long-term debt	24,306	23,718
Other non-current liabilities	1,818	264
Total non-current liabilities	26,124	23,982
Total liabilities	40,240	41,788
Commitments and contingencies (Note 13)
Stockholders' Equity:
Ordinary shares, nominal value $0.01, 1,000,000,000 ordinary shares authorized at June 30, 2019; 67,019,094 and 72,906,293 issued and outstanding at December 31, 2018 and June 30, 2019, respectively	729	670
Preferred shares, par value $0.01, 100,000,000 shares authorized at June 30, 2019; None issued and outstanding
Additional paid in capital	478,551	461,911
Accumulated other comprehensive income	27	27
Accumulated deficit	(435,902)	(393,978)
Total stockholders' equity	43,405	68,630
Total liabilities and stockholders' equity	$ 83,645	$ 110,418