IDEAYA Biosciences Announces First-Patient-In for Phase 1 Trial of IDE034, a Potential First-In-Class B7H3/PTK7 Bispecific TOP1 ADC

• Phase 1 dose escalation trial to determine safety, tolerability and PK of IDE034
• Potential as a monotherapy and in combination with proprietary PARG inhibitor, IDE161
• B7H3/PTK7 co-expressed in 30-40% of multiple solid tumor types, including lung, breast, ovarian and colorectal cancers

SOUTH SAN FRANCISCO, Calif., Feb. 25, 2026 /PRNewswire/ -- IDEAYA Biosciences, Inc. (NASDAQ: IDYA), a leading precision medicine oncology company, today announced 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.

"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. 

About IDEAYA Biosciences

IDEAYA is a precision medicine oncology company committed to the discovery, development, and commercialization of transformative therapies for cancer. Our approach integrates expertise in small-molecule drug discovery, structural biology and bioinformatics with robust internal capabilities in identifying and validating translational biomarkers to develop tailored, potentially first-in-class targeted therapies aligned to the genetic drivers of disease. We have built a deep pipeline of product candidates focused on synthetic lethality and antibody-drug conjugates, or ADCs, for molecularly defined solid tumor indications. Our mission is to bring forth the next wave of precision oncology therapies that are more selective, more effective, and deeply personalized with the goal of altering the course of disease and improving clinical outcomes for patients with cancer.

Forward-Looking Statements

This press release contains forward-looking statements, including, but not limited to, statements regarding the clinical development, potential safety, tolerability, pharmacokinetic profile, efficacy and therapeutic potential of IDE034, both as a monotherapy and in combination with IDEAYA's proprietary PARG inhibitor, IDE161; the design, conduct, timing and outcomes of the Phase 1 clinical trial of IDE034; the potential benefits of IDEAYA's ADC/DDR portfolio and combination strategies; and the prevalence of B7H3/PTK7 co-expression in certain tumor types. Such forward-looking statements are based on management's current expectations, assumptions and beliefs and involve substantial risks and uncertainties that could cause actual results, including, but not limited to, those related to IDEAYA's preclinical and clinical programs, commercial activities, and performance and/or achievements, to differ significantly and/or materially from those expressed or implied by the forward-looking statements. Such risks and uncertainties include, among others, the uncertainties inherent in the drug development process, including the process of designing and conducting preclinical and clinical trials,  enrollment rates, safety outcomes, efficacy results, regulatory interactions and decisions, and the ability to translate preclinical findings into clinical benefit, manufacturing and supply risks, competition, changes in standard of care, the timing and success of commercialization efforts, the outcome of collaborations and licensing arrangements,  IDEAYA's ability to successfully establish, protect and defend its intellectual property, and other matters that could affect the sufficiency of financial resources  to fund operations. IDEAYA undertakes no obligation to update or revise any forward-looking statements. A further description of  risks and uncertainties that could cause actual results to differ from those expressed in these forward-looking statements, as well as risks relating to the business of IDEAYA in general, are in IDEAYA's filings with the Securities and Exchange Commission, including IDEAYA's most recent Annual Report on Form 10-K  and any current and periodic reports filed with the U.S. Securities and Exchange Commission.

Investor and Media Contact

IDEAYA Biosciences
Joshua Bleharski, Ph.D.
Chief Financial Officer  
[email protected]

SOURCE IDEAYA Biosciences, Inc.