Shanghai Henlius Biotech Inc. (HENLIUS) has initiated patient dosing in a first-in-human, open-label phase 1 study of HLX3901, a DLL3xDLL3xCD3xCD28 tetra-specific antibody, targeting advanced small cell lung cancer (SCLC) and neuroendocrine carcinoma (NEC) in mainland China.
The study comprises two stages. Phase 1a follows a dose-escalation and backfill design across seven dose levels (0.10 mg–30 mg) on a 4-week cycle, combining accelerated titration at the lowest dose with a conventional “3+3” escalation for the remaining cohorts. Phase 1b will expand three dose cohorts at 10 mg, 20 mg and 30 mg under the same dosing schedule.
Primary objectives are to evaluate safety and tolerability, determine the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D), and generate preliminary efficacy signals. Key endpoints include dose-limiting toxicities, MTD/RP2D determination and investigator-assessed objective response rate.
HLX3901 is designed to enhance T-cell-mediated tumour lysis by simultaneously engaging dual DLL3 epitopes on tumour cells and co-activating CD3 and CD28 on T cells. Pre-clinical data indicated favourable anti-tumour activity and safety. The National Medical Products Administration cleared the investigational new drug application for HLX3901 in March 2026.
To date, no tetra-specific antibodies with the same dual DLL3, CD3 and CD28 targets have received marketing approval globally. HENLIUS cautions that successful development and commercialisation are not guaranteed, in line with Hong Kong Listing Rule 18A.05.
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