Leads Biolabs completes enrolment in Phase II BTC study of opamtistomig
Leads Biolabs has completed enrolment of 70 patients in its Phase II study of opamtistomig (LBL-024), a PD-L1/4-1BB bispecific antibody, as a first-line treatment for advanced biliary tract cancer (BTC). The Hong Kong-listed company said enrolment closed rapidly after the trial entered its expansion phase in April 2026, following a safety run-in that showed a favourable tolerability profile and early efficacy signals described as exceeding expectations.
Full clinical data from the study will be presented at the European Society for Medical Oncology (ESMO) Annual Meeting in Madrid, scheduled for 23 to 27 October 2026. The multicenter trial is being conducted at hospitals across China and is led by Academician Zhou Jian of Zhongshan Hospital, Fudan University.
The clinical rationale
BTC is a particularly difficult-to-treat malignancy. Around 419,100 new cases were recorded globally in 2024, with the highest burden in Asian countries. The five-year survival rate for advanced disease sits below 5%. The current first-line standard of care pairs a PD-(L)1 checkpoint inhibitor with chemotherapy: approved regimens including pembrolizumab plus chemotherapy and durvalumab plus chemotherapy achieve objective response rates below 30% and median overall survival of roughly 12 to 13 months. That limited clinical uplift over chemotherapy alone has left an acknowledged gap in the treatment landscape.
BTC is classified as an immune-cold tumour, meaning it exhibits low baseline immune infiltration that blunts conventional PD-1/PD-L1 responses. Leads Biolabs is positioning opamtistomig as a potential solution to this problem through its dual mechanism: blocking the PD-L1 inhibitory axis while conditionally agonising 4-1BB, a co-stimulatory receptor that can reactivate exhausted T cells. The company says preliminary data show encouraging tumour shrinkage in BTC patients, though it has not disclosed response-rate figures ahead of the ESMO presentation.
Charles Cai, Chief Medical Officer of Leads Biolabs, said the speed of enrolment reflected "strong confidence investigators and patients have placed in the encouraging efficacy signals generated by Opamtistomig to date," adding that immune-cold tumours represent "one of the most important frontiers for next generation immunotherapy."
Competitive and regulatory context
Opamtistomig has already received Breakthrough Therapy Designation from China's National Medical Products Administration for an unspecified indication, and in November 2024 the US FDA granted it Orphan Drug Designation for neuroendocrine carcinoma. A Fast Track Designation and European Commission Orphan Designation for extrapulmonary neuroendocrine carcinoma followed in January 2026. The company describes opamtistomig as the first 4-1BB–targeting bispecific to advance to a single-arm pivotal trial as monotherapy, a claim it has not yet had to defend in a head-to-head regulatory setting.
The broader bispecific antibody field has grown crowded, particularly in immuno-oncology. Several 4-1BB programmes from larger developers, including earlier-generation monospecific agonists that encountered hepatotoxicity concerns, have informed a design shift toward conditional activation strategies that require tumour-localised engagement to limit systemic toxicity. Opamtistomig's PD-L1 anchor is one such approach and is shared with assets from other developers, making differentiation on safety profile and durable response data critical at the ESMO readout.
Leads Biolabs has evaluated opamtistomig across 13 solid tumour indications in China. Investors will be watching the BTC dataset closely, both as a standalone commercial opportunity and as a read-across for the broader pan-tumour ambitions the company has outlined for the asset.