Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025
Current assets:
Cash and cash equivalents	$ 469,928	$ 628,110
Prepaid expenses and other current assets	15,270	19,181
Research and development incentives receivable	52,358	35,594
Total current assets	537,556	682,885
Property and equipment, net	4,214	6,021
Operating lease right-of-use assets	13,433	15,886
Other assets	11,976	12,805
Total assets	567,179	717,597
Current liabilities:
Accounts payable	9,588	9,669
Accrued expenses and other current liabilities	34,871	44,354
Deferred revenue, current portion		2,961
Total current liabilities	44,459	56,984
Operating lease liabilities, net of current portion	12,864	14,096
Deferred revenue, net of current portion	3,692	35,508
Other long-term liabilities	887	1,032
Total liabilities	61,902	107,620
Commitments and contingencies (Note 10)
Shareholders' equity:
Ordinary shares, including non-voting ordinary shares, £0.01 nominal value; 163,360,109 and 159,685,229 shares authorized on September 30, 2026 and December 31, 2025, respectively; 69,993,013 and 69,367,896 shares issued and outstanding at September 30, 2026 and December 31, 2025, respectively	903	894
Additional paid-in capital	1,531,098	1,512,339
Accumulated other comprehensive loss	(5,337)	(3,505)
Accumulated deficit	(1,021,387)	(899,751)
Total shareholders' equity	505,277	609,977
Total liabilities and shareholders' equity	$ 567,179	$ 717,597

Amount of research and development incentives receivables, classified as current.

No definition available.

Name:	bcyc_ResearchAndDevelopmentIncentivesReceivableCurrent
Namespace Prefix:	bcyc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).