IDEAYA Biosciences has enrolled the first patient in its Phase 1 dose-escalation and expansion trial of IDE034. The trial will determine safety, tolerability and pharmacokinetics of the bispecific ADC in monotherapy and planned combination cohorts. Enrollment of the initial patient marks the start of dose-finding in patients with advanced solid tumors.

IDE034 binds both B7H3 and PTK7, internalizing only where both antigens are co-expressed, potentially enhancing selectivity and tolerability. B7H3 and PTK7 co-expression occurs in approximately 30-40% of lung, breast, ovarian and colorectal cancers, with minimal dual expression in normal tissues. As a TOP1 ADC, IDE034 delivers cytotoxic payload selectively to tumor cells bearing both targets.

IDEAYA plans to test IDE034 in combination with its oral PARG inhibitor IDE161 to exploit DNA damage response pathways. Preclinical models showed enhanced efficacy and durability when TOP1 ADCs are paired with DDR-targeting agents. This combination approach reflects IDEAYA’s strategy to overcome resistance and improve clinical outcomes in solid tumors.

Dosing of the first patient with IDE034 triggered a $5 million milestone payment from IDEAYA to Biocytogen under their option and license agreement. This payment underscores progress in the collaboration and funds continued development of IDE034. Additional milestone payments are anticipated as the trial advances through clinical and regulatory stages.