IDEAYA Biosciences Announces Successful FDA Type C Meeting for IDE849, DLL3 TOP1 ADC, on Phase 3 Registrational Trial Design for Potential Accelerated and Full Approval in Extensive Stage Small Cell Lung Cancer

PR Newswire

SOUTH SAN FRANCISCO, Calif., Aug. 31, 2026

SOUTH SAN FRANCISCO, Calif., Aug. 31, 2026 /PRNewswire/ -- IDEAYA Biosciences, Inc. (NASDAQ: IDYA), a precision medicine oncology company committed to the discovery and development of targeted therapeutics, announced a successful FDA Type C meeting to determine the Phase 3 registrational trial design for IDE849, a potential best-in-class delta-like ligand 3 (DLL3)-targeting Topo-I-payload antibody drug conjugate (ADC), in extensive stage small cell lung cancer (ES-SCLC). IDEAYA is targeting to initiate the Phase 3 registrational study in ES-SCLC by year-end 2026.

"Based on the FDA Type C meeting, we are targeting to initiate a randomized Phase 3 registrational study for IDE849 monotherapy in extensive stage small cell lung cancer to enable a potential accelerated approval and full approval in one seamless study design," said Yujiro S. Hata, President and Chief Executive Officer, IDEAYA Biosciences. "We also look forward to the clinical data updates at ESMO 2026 and later this year from our company sponsored clinical trial in ES-SCLC and NEC to support a potential best-in-class profile."

The anticipated enrollment target for the IDEAYA-sponsored global Phase 3 registrational study is approximately 400 ES-SCLC patients with prior tarlatamab treatment. The study will be randomized 1:1 between the treatment and an investigator's choice control arm that will include topotecan and ambrucin. The primary endpoint for accelerated approval will be overall response rate (ORR) by blinded independent central review (BICR) and the primary endpoint for full approval will be median overall survival. The secondary endpoints will include median duration of response by BICR, progression free survival, safety, among others.

IDEAYA has an ongoing multi-site global Phase 1 clinical trial for IDE849 in DLL3 upregulated solid tumor indications, including SCLC, and neuroendocrine carcinomas (NEC) (NCT07174583). The study is enrolling patients globally, including in North America, Europe, Australia, South America, and Asia. In this ongoing Phase 1 dose escalation study, IDE849 is currently evaluating the expansion doses of 2.4 mg/kg and 3.5 mg/kg IV once every 3-weeks (Q3W) to determine the recommended Phase 3 dose (RP3D).

In addition, IDE849 is being evaluated in clinical combination study with AstraZeneca's PDL1 inhibitor Imfinzi, and IDEAYA's potential first-in-class Phase 1 PARG inhibitor, IDE161, to determine a potential first-line (1L) SCLC Phase 3 registrational trial design. IDE161 prevents the removal of poly(ADP-ribose) chains generated by PARP during the DNA damage response, leading to persistent PARylation and impaired resolution of DNA repair complexes. Together with TOP1-payload ADCs, this unique mechanism-of-action results in sustained TOP1 cleavage complexes and the accumulation of DNA damage that delivers enhanced anti-tumor activity. We believe this potential first-in-class combination has the potential to enhance durability of IDEAYA's TOP1-payload based ADC pipeline, including IDE849 and IDE034 (Phase 1 B7H3/PTK7 Bispecific TOP1 ADC).

DLL3 has been reported to be upregulated in multiple solid tumor types, including in SCLC, NEC and melanoma, among others. IDEAYA estimates the annual incidence of SCLC and NEC in the United States is approximately 34,000 and 19,000 patients, respectively. DLL3 has limited extracellular expression in normal tissues, making it a promising potential therapeutic target in these solid tumors, for which there remains significant unmet medical need.

About IDEAYA Biosciences

IDEAYA is a precision medicine oncology company committed to the discovery and development of targeted therapeutics for patient populations selected using molecular diagnostics. IDEAYA's approach integrates capabilities in identifying and validating translational biomarkers with drug discovery to select patient populations most likely to benefit from its targeted therapies. IDEAYA is applying its research and drug discovery capabilities to synthetic lethality – which represents an emerging class of precision medicine targets.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 and other applicable securities laws. All statements contained in this press release that do not relate to matters of historical fact should be considered forward-looking statements, including, but not limited to, statements regarding IDEAYA's interpretation of, and the anticipated regulatory implications arising from, feedback received during the FDA Type C meeting for IDE849; the potential design, initiation, timing, enrollment, conduct and completion of a randomized Phase 3 registrational trial evaluating IDE849 monotherapy in patients with extensive-stage small cell lung cancer previously treated with tarlatamab (Imdelltra); the potential for such trial to support accelerated approval based on overall response rate by blinded independent central review and subsequent full approval based on median overall survival; the anticipated size, randomization, treatment arms, control therapies and endpoints of the Phase 3 trial; the evaluation of doses and the timing and selection of a recommended Phase 3 dose; the timing, availability, content and significance of clinical data updates from Hengrui and IDEAYA-sponsored clinical trials, including anticipated presentations at ESMO 2026 and clinical data updates in the fourth quarter of 2026; the potential safety, efficacy, tolerability, durability, clinical activity and therapeutic benefits of IDE849, including its potential best-in-class profile; the development and evaluation of IDE849 in combination with Imfinzi and IDE161; the potential design and initiation of a Phase 3 registrational trial in first-line small cell lung cancer; the potential first-in-class profile and mechanism of action of IDE161; the potential for IDE161 to enhance the activity or durability of IDEAYA's TOP1-payload ADC pipeline, including IDE849 and IDE034; the prevalence and therapeutic relevance of DLL3 expression across solid tumors; and the potential clinical and regulatory development of IDE849, IDE161 and IDE034.

Such forward-looking statements are based on IDEAYA's management's current expectations, assumptions and beliefs and involve risks, uncertainties, and other factors that could cause actual results, including those related to IDEAYA's clinical programs, regulatory activities, commercial activities and performance or achievements, to differ significantly or materially from those expressed or implied by the forward-looking statements.

Such risks and uncertainties include, among others, risks relating to the FDA's feedback from regulatory meetings is preliminary and nonbinding, and the FDA may subsequently require modifications to the proposed Phase 3 trial design, endpoints, patient population, statistical analysis plan or regulatory strategy, or may require additional clinical or nonclinical data or one or more additional trials; the FDA may determine that overall response rate does not support accelerated approval or that the trial results do not verify clinical benefit or support full approval; IDEAYA may experience delays in selecting a recommended Phase 3 dose or initiating, enrolling, conducting or completing clinical trials; clinical trial results, including interim, preliminary or topline results, may not be reproduced in later trials or may not support further development or regulatory approval; IDE849, IDE161 or IDE034 may not demonstrate the safety, efficacy, tolerability, durability, clinical activity or differentiated profile anticipated; combination therapies may result in unexpected toxicities or may not demonstrate additive or synergistic clinical benefit; data may be delayed, incomplete, inconsistent or unfavorable; regulatory authorities may not accept IDEAYA's proposed development or approval strategies; and IDEAYA may encounter difficulties arising from patient enrollment, clinical-site activation, drug supply, manufacturing, competition, reliance on third parties and other factors. For a further description of risks and uncertainties that could cause actual results to differ from those expressed in or implied by these forward-looking statements, as well as risks relating to IDEAYA's business generally, is included in IDEAYA's filings with the Securities and Exchange Commission, including its most recent Annual Report on Form 10-K, filed on February 17, 2026, subsequent Quarterly Reports on Form 10-Q and Current Reports on Form 8-K.

Forward-looking statements speak only as of the date of this press release, and IDEAYA undertakes no obligation to update or revise any forward-looking statements contained herein to reflect any change in expectations, new information, subsequent events or circumstances, or otherwise, except as required by law.

Investor and Media Contact
IDEAYA Biosciences
Joshua Bleharski, Ph.D.
Chief Financial Officer
investor@ideayabio.com

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