IDEAYA’s IDE849 Advances Toward Phase 3 in Lung Cancer

South San Francisco, California, August 31, 2026

FDA Aligns on Phase 3 Registrational Strategy

The FDA Type C meeting focused on the proposed Phase 3 registrational trial design for IDE849. Type C meetings are formal interactions between sponsors and the FDA that can address questions related to an investigational product’s development program, including clinical trial design, regulatory strategy and other issues that may influence the path toward a future marketing application. According to IDEAYA, the company achieved alignment with the FDA on important aspects of the proposed Phase 3 program. The planned study is intended to evaluate IDE849 in patients with extensive-stage small cell lung cancer, with the development strategy designed to potentially generate evidence supporting both an accelerated approval route and subsequent confirmation for full approval. The regulatory discussion is particularly relevant because ES-SCLC is an aggressive form of lung cancer in which disease progression can occur rapidly despite available treatments. Establishing an appropriately designed registrational study is therefore a critical step in determining whether IDE849 can demonstrate sufficient efficacy and safety to support future regulatory submissions.

IDE849 Targets DLL3 With TOP1 Payload

IDE849 is being developed as a DLL3-targeted TOP1 antibody-drug conjugate, combining targeted antibody delivery with a topoisomerase I (TOP1) inhibitor payload. The ADC approach is designed to use an antibody component to recognize DLL3, a protein associated with small cell lung cancer, and deliver the cytotoxic payload to tumor cells. The use of a targeted ADC represents a strategy intended to improve the selective delivery of anticancer therapy to malignant cells. Following target engagement, the ADC is designed to internalize and release its payload, enabling the TOP1 inhibitor to interfere with DNA replication and induce tumor-cell damage. IDEAYA is advancing IDE849 as a potential treatment option for patients with ES-SCLC, where DLL3 represents a therapeutically relevant target. The Phase 3 strategy follows earlier development work evaluating the investigational therapy and seeks to determine whether the candidate can produce clinically meaningful outcomes in a larger, controlled patient population. While the FDA meeting provides regulatory alignment on the proposed development approach, IDE849 remains investigational and has not been approved by the FDA. Its safety and efficacy will need to be established through the planned clinical development program and regulatory review.

Potential Accelerated and Full Approval Path

A central element of the regulatory discussion was the potential for IDE849 development to support accelerated approval and full approval. Accelerated approval can allow certain therapies addressing serious conditions to reach patients based on surrogate endpoints that are reasonably likely to predict clinical benefit, while confirmatory evidence is subsequently required to verify that benefit. For IDE849, the proposed Phase 3 registrational strategy is intended to address the requirements associated with these potential regulatory pathways. The approach could allow the company to evaluate a clinically relevant treatment effect while generating evidence needed for longer-term regulatory confirmation. The successful FDA Type C meeting represents a key milestone for IDEAYA as it prepares for the next stage of clinical development. The company will now continue work toward initiation of the proposed Phase 3 registrational trial, including finalizing operational and regulatory requirements. If the Phase 3 program demonstrates favorable efficacy and an acceptable safety profile, the results could potentially support future regulatory submissions for patients with extensive-stage small cell lung cancer. For the broader oncology field, the development of DLL3-targeted ADCs reflects continued efforts to use tumor-associated targets to deliver potent cytotoxic therapies more selectively. IDEAYA’s regulatory progress with IDE849 therefore marks an important step toward pivotal-stage development of a next-generation ADC for ES-SCLC, while the upcoming clinical data will ultimately determine whether the investigational therapy can advance toward potential approval.

Source: IDEAYA Biosciences press relese