• B7H3 and PTK7 is co-expressed in multiple solid tumor types, including lung, colorectal, and head and neck cancers, at approximately 30%, 46%, and 27%, respectively
• Deep and durable regressions observed with IDE034 monotherapy in multiple preclinical in-vivo models with B7H3 and PTK7 co-expression
• Enhanced durability with IDE034 and IDE161 PARG inhibitor combination in preclinical in vivo models; targeting to share additional preclinical data supporting mechanistic rationale at a medical conference in H1 2026

IDEAYA Biosciences, Inc. (NASDAQ: IDYA), a precision medicine oncology company committed to the discovery and development of targeted therapeutics, announced the clearance of an investigational new drug (IND) application with the U.S. Food and Drug Administration (FDA) for the initiation of a Phase 1 clinical trial to evaluate IDE034, a potential first-in-class bispecific B7H3/PTK7 TOP1 antibody-drug conjugate (ADC).  IDEAYA expects to begin enrolling the study in Q1 2026, initially evaluating patients with solid tumors known to express B7H3 and PTK7, including lung, colorectal, head and neck and ovarian/gynecological cancers.  Based on the Human Protein Atlas database, B7H3/PTK7 has been reported to be co-expressed in lung, colorectal, and head and neck cancers at approximately 30%, 46% and 27%, respectively.

"IND clearance for IDE034 is an important step in expanding our potential first-in-class TOP1 ADC clinical pipeline into bispecific, precision-guided approaches," said Darrin M. Beaupre, M.D., Ph.D., Chief Medical Officer of IDEAYA Biosciences. "IDE034 has demonstrated robust antitumor activity and selective targeting of B7H3- and PTK7-expressing solid tumor models. The high prevalence of B7H3/PTK7 co-expression in solid tumors such as lung, colorectal, and head and neck cancers underscores its broad indication potential."

"We are excited to advance our differentiated clinical strategy with now three potentially first-in-class clinical-stage programs focused on enhancing the efficacy of TOP1 ADCs through the PARG DDR combination mechanism.  We believe this approach addresses a key unmet need by improving the durability of response to TOP1 payload-based ADC therapies.  We are targeting to share additional preclinical data to support the PARG and TOP1 ADC combination rationale at a major medical conference in H1 2026," said Yujiro S. Hata, President and Chief Executive Officer of IDEAYA Biosciences.

Preclinical studies have demonstrated strong anti-tumor activity in B7H3/PTK7-positive tumor models, including deep and durable tumor regressions with IDE034 monotherapy, supporting advancement into clinical development. This co-expression pattern supports the potential for broad monotherapy activity, while the TOP1 payload provides a strong mechanistic rationale for combining IDE034 with IDEAYA's PARG inhibitor, IDE161.  TOP1 inhibition induces replication stress and DNA damage, which can increase reliance on the PARG pathway; therefore, a IDE034 and IDE161 combination approach may enhance anti-tumor activity in patients with solid tumors that co-express B7H3 and PTK7, consistent with the results that were observed preclinically with this combination.