Condensed Consolidated Balance Sheets - USD ($)	Sep. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 572,086,000	$ 339,154,000
Accounts receivable	0	2,045,000
Prepaid expenses and other current assets	13,673,000	9,022,000
Research and development incentives receivable	17,277,000	19,162,000
Total current assets	603,036,000	369,383,000
Property and equipment, net	15,599,000	19,110,000
Operating lease right-of-use assets	14,597,000	13,658,000
Other assets	5,451,000	8,458,000
Total assets	638,683,000	410,609,000
Current liabilities:
Accounts payable	8,493,000	6,472,000
Accrued expenses and other current liabilities	34,053,000	26,452,000
Deferred revenue, current portion	27,190,000	20,418,000
Total current liabilities	69,736,000	53,342,000
Long-term debt, net of discount	30,604,000	30,315,000
Operating lease liabilities, net of current portion	10,423,000	10,885,000
Deferred revenue, net of current portion	107,582,000	41,455,000
Other longterm liabilities	4,316,000	3,829,000
Total liabilities	222,661,000	139,826,000
Commitments and contingencies (Note 11)
Shareholders' equity:
Ordinary shares including non-voting shares, £0.01 nominal value; 59,612,613 and 57,820,181 shares authorized at September 30, 2023 and December 31, 2022, respectively; 42,384,799 and 29,873,893 shares issued and outstanding at September 30, 2023 and December 31, 2022, respectively	550,000	387,000
Additional paid-in capital	875,248,000	601,105,000
Accumulated other comprehensive income	2,885,000	387,000
Accumulated deficit	(462,661,000)	(331,096,000)
Total shareholders' equity	416,022,000	270,783,000
Total liabilities and shareholders' equity	$ 638,683,000	$ 410,609,000