Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 169,598	$ 187,986
Prepaid expenses	7,247	4,538
Tax and tax incentive receivables	10,272	8,260
Other current assets	1,484	1,720
Total current assets	188,601	202,504
Non-current assets:
Furniture and equipment, net	98	107
Goodwill	545	545
Right-of-use assets	906	1,050
Total non-current assets	1,549	1,702
Total assets	190,150	204,206
Current liabilities:
Accounts payable	541	178
Accrued expenses	8,514	10,863
Operating lease liability	757	798
Warrants	2,753	2,246
Other current liabilities	133	118
Total current liabilities	12,698	14,203
Non-current liabilities:
Term loan	4,685	4,635
Operating Lease, Liability, Noncurrent	353	514
Total non-current liabilities	5,038	5,149
Total liabilities	17,736	19,352
Commitments and contingencies
Shareholders' equity:
Ordinary £0.05 par value shares; 488,304,446 and 488,304,446 issued, and 463,745,750 and 463,304,446 outstanding, at March 31, 2021 and December 31, 2020, respectively	31,794	31,794
Additional paid-in capital	375,261	366,411
Ordinary shares held in treasury	(1,670)	(1,700)
Accumulated other comprehensive loss	(4,601)	(4,601)
Accumulated deficit	(228,370)	(207,050)
Total shareholders' equity	172,414	184,854
Total liabilities and shareholders' equity	$ 190,150	$ 204,206