On February 25, 2026 IDEAYA Biosciences, Inc. (NASDAQ: IDYA), a leading precision medicine oncology company, reported that the first patient has been enrolled in its Phase 1 dose escalation/expansion trial evaluating IDE034, an investigational PTK7/B7H3 bispecific TOP1 ADC. The company is planning to evaluate safety, tolerability and PK of IDE034 as a monotherapy in the Phase 1 trial, and also plans to test combinations with agents that target the DNA damage response (DDR) pathway, such as their proprietary PARG inhibitor, IDE161. Dosing of the first patient with IDE034 triggers a $5 million milestone payment from IDEAYA to Biocytogen, pursuant to the Option and License Agreement between the companies.
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"This is an important milestone for IDE034 as well as our broader ADC/DDR portfolio focused on exploring combinations of highly selective TOP1 ADCs with agents targeting the DDR pathway. We are excited to begin dosing patients with IDE034, a B7H3/PTK7 bispecific ADC that has demonstrated promising signs of efficacy as a monotherapy and synergy in combination with IDE161 across several preclinical tumor cell models. IDE034 is our second proprietary TOP1 ADC, building on the progress we have made with IDE849, our DLL3 TOP1 ADC currently in Phase 1 for SCLC and NEC, and represents another potentially first-in-class therapy for cancer patients in need of new and improved treatment options," said Yujiro S. Hata, President and Chief Executive Officer of IDEAYA Biosciences.
IDE034 is a potentially first-in-class B7H3/PTK7 bispecific TOP 1 ADC designed to be internalized only when its target antigens are co-expressed on the same tumor cell, which may enhance its selectivity and tolerability profile relative to monovalent antibody formats. IDEAYA estimates that B7H3/PTK7 are co-expressed in approximately 30-40% of certain large solid tumor types, including lung, breast, ovarian and colorectal cancers, while exhibiting minimal dual antigen expression in normal tissue. In preclinical tumor models, IDE034 has also demonstrated compelling combination potential with IDE161, the company’s oral PARG inhibitor, that suggests these mechanisms may synergize to enhance the efficacy and durability of TOP1 ADCs.
(Press release, Ideaya Biosciences, FEB 25, 2026, View Source [SID1234663012])