Purple Biotech Announced Its Second CAPTN-3 Trispecific Antibody, IM1305, Targeting TROP2 In Development, FDA Investigational New Drug Submission Planned For 2026

Author: Benzinga Newsdesk | September 03, 2025 07:14am

• IM1305 (capped-CD3xTROP2xNKG2A) contains a masked anti-CD3 arm, as well as an anti-NKG2A arm, and an anti-TROP2 arm. The potent anti-CD3 arm is masked at the periphery with a cleavable cap, designed to be removed specifically in the TME, which is expected to reduce the risk of off-target cytokine release and potentially enables higher dosing to achieve increased efficacy.
• Encouraging preclinical results targeting TROP2 have demonstrated sustained tumor regression of human triple negative breast cancer (TNBC) in a mouse model, with no detectable tumor recurrence following treatment completion. Significant cell death induction was demonstrated in multiple tumor types, including TNBC, tongue and hypopharyngeal cancers, pancreatic and gastric cancers, at remarkably low doses (EC50 1-5 pM).
• TROP2 is broadly expressed across major solid tumors (e.g., breast, lung, gastrointestinal, ovarian) and is associated with poor prognosis. Supported by prior clinical validation from approved TROP2-directed antibody-drug conjugates (ADCs), the broad potential of targeting TROP2 makes it a compelling target for the CAPTN-3 platform.
• Unlike ADCs or monospecific antibodies, CAPTN-3 combines selective TROP2 binding with multi-effector immune recruitment (T and NK cells). This immune synapse–driven cytotoxicity is expected to potentially be independent of TROP2 density, providing a strong rationale for activity in non-ADC settings and across diverse tumor types.

Posted In: PPBT