IDEAYA Biosciences, Inc. Reports Second Quarter 2024 Financial Results

and Provides Business Update

South San Francisco, CA, August 6, 2024– IDEAYA Biosciences, Inc. (Nasdaq: IDYA), a precision medicine oncology company committed to the discovery and development of targeted therapeutics, provided a business update, and announced financial results for the second quarter ended June 30, 2024.

“We made significant progress advancing four potential first-in-class precision medicine oncology clinical programs this past quarter, and we are on-track to deliver our fifth potential first-in-class program to the clinic this year in Werner Helicase. Importantly, we presented preliminary clinical proof of concept data for IDE397 monotherapy in MTAP-deletion urothelial and lung cancer, demonstrating the ability to deliver confirmed RECIST responses with a favorable AE profile. The IDE397 combination therapy trials in MTAP-deletion solid tumors with our collaborators continue to progress, with the first patient dosed in the Phase 1 trial evaluating IDE397 with Gilead’s Trodelvy, and continued dose escalation in the AMG 193 clinical combination with Amgen. We look forward to hosting an investor R&D Day that will profile our rapidly advancing potential first-in-class precision medicine oncology pipeline, where we are targeting multiple additional development candidates by the end of this year,” said Yujiro S. Hata, President and Chief Executive Officer, IDEAYA Biosciences.

“We were excited to share the compelling interim clinical data from the investigator- and company-sponsored Phase 2 trials of darovasertib in neoadjuvant UM, and look forward to discussing the registrational path forward with the FDA and providing our company-sponsored Phase 2 trial update in over 30 patients during the second half of this year. In addition, the most recent positive interim results observed with IDE397 monotherapy, in addition to the ongoing combination trials, bring us closer to potentially addressing a high unmet need in MTAP-deletion NSCLC, urothelial cancer and other solid tumors, and we are targeting developing a registrational plan in 2025. Separately, we anticipate initiating both the Phase 2 IDE161 monotherapy expansion cohort and the IDE161 in combination with KEYTRUDA cohort in the second half of 2024,” said Darrin Beaupre, M.D., Ph.D., Chief Medical Officer, IDEAYA Biosciences.

Summary of Q2 and Recent Key Developments

Research and Clinical Development

Corporate Development

Clinical Programs and Upcoming Milestones

Darovasertib (IDE196) Program in Tumors with GNAQ or GNA11 Mutations

Darovasertib is a potent and selective protein kinase C (PKC) inhibitor being developed to broadly address primary and metastatic UM. Darovasertib is currently being evaluated in four ongoing clinical trials. The darovasertib and crizotinib combination in MUM has FDA Fast Track designation:

IDE397 Program in Tumors with MTAP Deletion

IDE397 is a potent and selective small molecule inhibitor targeting methionine adenosyltransferase 2 alpha (MAT2A) in patients having solid tumors with methylthioadenosine phosphorylase (MTAP) deletion. IDEAYA continues to focus on evaluating IDE397 in two trials in select monotherapy indications and in high conviction clinical combinations:

IDE161 Program in Tumors with Homologous Recombination Deficiency

IDE161 is a potential first-in-class inhibitor of poly(ADP-ribose) glycohydrolase (PARG), a novel, mechanistically distinct target in the same clinically validated biological pathway as poly(ADP-ribose) polymerase (PARP). IDE161 received two FDA Fast Track designations in platinum-resistant advanced or metastatic ovarian cancer patients having tumors with BRCA1/2 mutations, and in pretreated advanced or metastatic HR+, Her2-, BRACA1/2 mutant breast cancer. IDE161 is currently being evaluated as a monotherapy in IDE161-001 (NCT05787587), a Phase 1 trial of IDE161 in solid tumors with homologous recombination deficiency (HRD). Selection of an initial Phase 1/2 monotherapy expansion dose in HRD solid tumors remains on track for the second half of 2024. IDEAYA is currently validating IDE161 combination opportunities preclinically and targeting identification of additional combination(s) in 2024.

Additionally, IDEAYA is planning to evaluate IDE161 in combination with KEYTRUDA® in patients with microsatellite instability (MSI)-high and microsatellite stable (MSS) endometrial cancer. Clinical first-patient-in for the IDE161 and KEYTRUDA® combination is targeted in the second half of 2024.

KEYTRUDA® is a registered trademark of Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, USA.

GSK-Partnered Programs

GSK101 (IDE705) Program in Tumors with HRD

GSK101 (IDE705) is a potential first-in-class small molecule inhibitor of Pol Theta Helicase being developed as a combination treatment with niraparib for advanced solid tumors with HRD. The

dose escalation portion of the GSK-sponsored Phase 1/2 clinical trial to evaluate GSK101 in combination with niraparib, the GSK small molecule inhibitor of PARP, for patients having solid tumors with BRCA or other HR mutations, or with HRD is currently ongoing.

Upon initiation of the Phase 1 dose expansion, IDEAYA will be eligible to receive a $10.0 million milestone payment, with the collaboration having a potential further aggregate later-stage development and regulatory milestones of up to $465.0 million. GSK is responsible for all research and development costs for the program. Upon commercialization, IDEAYA will be eligible to receive up to $475 million of commercial milestones, and tiered royalties on global net sales of GSK101 – ranging from high single-digit to sub-teen double-digit percentages, subject to certain customary reductions.

Werner Helicase Inhibitor in Tumors with High MSI

IDEAYA and GSK remain on track for an IND filing in the second half of 2024 for the selected Werner Helicase inhibitor announced in December 2023. The IND-enabling Good Laboratory Practice (GLP) toxicology studies have been completed for the Werner Helicase inhibitor development candidate. IDEAYA has the potential to earn up to an additional $17.0 million in aggregate milestones through early Phase 1, including $7.0 million upon IND clearance, and is entitled to receive up to $465.0 million in further later-stage development and regulatory milestones. GSK is responsible for 80% of global research and development costs and IDEAYA is responsible for 20% of such costs. Upon commercialization, IDEAYA will be eligible to receive up to $475 million of commercial milestones, 50% of U.S. net profits and tiered royalties on global non-U.S. net sales of the Werner Helicase inhibitor development candidate (DC) – ranging from high single-digit to sub-teen double-digit percentages, subject to certain customary reductions.

B7H3/PTK7 Topo-Payload BsADC Program

IDEAYA entered into an option and license agreement for a potential first-in-class B7H3/PTK7 Topo-Payload BsADC program with Biocytogen in July 2024. The agreement grants IDEAYA an option for an exclusive worldwide license from Biocytogen for a potential first-in-class B7H3/PTK7 Topo-Payload BsADC program. B7H3/PTK7 has been found to be co-expressed in multiple solid tumor types, including double-digit percent prevalence in lung, colorectal, and head and neck cancers, among others. Based on preclinical data, the potential first-in-class B7H3/PTK7 Topo-Payload BsADC program has the potential to be developed as a monotherapy agent and used in combination with multiple programs in IDEAYA’s pipeline targeting DDR-based therapies, including PARG inhibitor IDE161. A development candidate nomination for the B7H3/PTK7 Topo-Payload BsADC program is targeted for the second half of 2024.

Under the terms of the agreement, Biocytogen will receive an upfront fee and, upon an option exercise by IDEAYA, be entitled to receive an option exercise fee, development and regulatory milestones and commercial milestone payments, as well as single-digit royalties on net sales. Total potential upfront, option exercise and milestone payments equal an aggregate of $406.5 million, including development and regulatory milestones of $100.0 million.

Next-Generation Precision Medicine Pipeline Programs

Early preclinical research programs focused on pharmacological inhibition of several new targets for patients with solid tumors characterized by defined biomarkers based on genetic mutations and/or molecular signatures are ongoing. These programs have the potential for discovery and development of first-in-class or best-in-class therapeutics with multiple wholly owned DC nominations targeted in the second half of 2024, including in MTAP-deletion solid tumors indications to enable a potential wholly-owned clinical combination with IDE397 and the lysine acetyltransferase 6 (KAT6) pathway.

Financial Results

As of June 30, 2024, IDEAYA had cash, cash equivalents and marketable securities totaling $952.7 million. This compared to cash, cash equivalents and marketable securities of $941.4 million as of March 31, 2024. The increase was primarily attributable to net proceeds of $36.5 million from the sale of common stock shares through IDEAYA’s at-the-market offering program during the period from April 1, 2024 to June 30, 2024, partially offset by net cash used in operations.

Subsequent to the reporting period for the quarter ended June 30, 2024, IDEAYA announced the closing in July 2024 of an underwritten public offering of common stock and pre-funded warrants to purchase common stock, generating net proceeds of approximately $283.8 million, after deducting the underwriting discounts and commissions and estimated offering expenses payable by IDEAYA.

There was no collaboration revenue recognized for the three months ended June 30, 2024 similar to the three months ended March 31, 2024. We completed all performance obligations related to the upfront payment under the GSK collaboration agreement as of December 31, 2023. Future collaboration revenue recognized under the GSK collaboration agreement will be related to future milestone payments as they are earned.

Research and development (R&D) expenses for the three months ended June 30, 2024 totaled $54.5 million compared to $42.8 million for the three months ended March 31, 2024. The increase was primarily due to higher stock-based compensation expenses, clinical trial expenses, professional and outside services and consulting expenses.

General and administrative (G&A) expenses for the three months ended June 30, 2024 totaled $10.4 million compared to $8.2 million for the three months ended March 31, 2024. The increase was primarily due to higher stock-based compensation expenses, audit fees and consulting expenses.

The net loss for the three months ended June 30, 2024 was $52.8 million compared to the net loss of $39.6 million for the three months ended March 31, 2024. Total stock compensation expense for the three months ended June 30, 2024 was $9.7 million compared to $6.3 million for the three months ended March 31, 2024.

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.

IDEAYA’s updated corporate presentation is available on its website, at its Investor Relations page: https://ir.ideayabio.com/.

Forward-Looking Statements

This press release contains forward-looking statements, including, but not limited to, statements related to (i) the timing, content and venue of clinical program updates, (ii) the timing for the development of a joint Amgen/IDEAYA publication strategy, (iii) the timing of an FDA Type C meeting for neoadjuvant UM, (iv) the timing of initial Phase 1/2 monotherapy expansion for IDE161 in HRD solid tumors, (v) the timing of a first-patient-in in the IDE161 and KEYTRUDA combination study, (vi) the timing of IND submission for the Werner Helicase inhibitor DC, (vii) the timing of designation of next generation development candidates, (viii) the extent to which IDEAYA’s existing cash, cash equivalents, and marketable securities will fund its planned operations, (ix) the estimate of patient populations, (x) additional clinical combinations, and (xi) the receipt of development and regulatory milestones. Such forward-looking statements involve substantial risks and uncertainties that could cause IDEAYA’s preclinical and clinical development programs, future results, performance or achievements to differ significantly 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 IDEAYA’s programs’ early stage of development, the process of designing and conducting preclinical and clinical trials, the regulatory approval processes, the timing of regulatory filings, the challenges associated with manufacturing drug products, IDEAYA’s ability to successfully establish, protect and defend its intellectual property, and other matters that could affect the sufficiency of existing cash to fund operations. IDEAYA undertakes no obligation to update or revise any forward-looking statements. For a further description of the 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, see IDEAYA’s Annual Report on Form 10-K dated February 20, 2024 and any current and periodic reports filed with the U.S. Securities and Exchange Commission.

Investor and Media Contact

IDEAYA Biosciences
Andres Ruiz Briseno

SVP, Head of Finance and Investor Relations
investor@ideayabio.com

IDEAYA Biosciences, Inc.

Condensed Statements of Operations and Comprehensive Loss

(in thousands, except share and per share amounts)

IDEAYA Biosciences, Inc.

Condensed Balance Sheet Data

(in thousands)