NASDAQ: IDYA Certain statements in this presentation and the accompanying oral commentary are forward-looking statements. These statements relate to future events or the future financial performance of IDEAYA Biosciences

IDEAYA Biosciences Improving Lives Through Transformative Precision Medicines JPM Healthcare Conference

January 2021 Exhibit 99.1 NASDAQ: IDYA

Certain statements in this presentation and the accompanying oral commentary are forward-looking statements. These statements relate to future events or the future financial performance of IDEAYA Biosciences, Inc. (the "Company") and involve known and unknown risks, uncertainties and other factors that may cause the actual results, levels of activity, performance or achievements of the Company or its industry to be materially different from those expressed or implied by any forward-looking statements. In some cases, forward-looking statements can be identified by terminology such as "may," "will," "could," "would," "should," "expect," "plan," "anticipate," "intend," "believe," "estimate," "predict," "potential" or other comparable terminology. All statements other than statements of historical fact could be deemed forward-looking, including any expectations regarding the Company's target discovery platform or new target validation efforts as creating opportunities for research and development initiatives; any projections of financial information, market opportunities, cash runway or profitability; any statements about historical results that may suggest trends for the Company's business; any statements of the plans, strategies, and objectives of management for development programs or future operations; any statements about the timing of preclinical research, clinical development, regulatory filings, manufacturing or release of data; any statements of expectation or belief regarding future events, potential markets or market size, technology developments, or receipt of cash milestones, option exercise fees or royalties; and any statements of assumptions underlying any of the items mentioned. The Company has based these forward-looking statements on its current expectations, assumptions, estimates and projections. While the Company believes these expectations, assumptions, estimates and projections are reasonable, such forward-looking statements are only predictions and involve known and unknown risks and uncertainties, many of which are beyond the Company's control. These and other important factors may cause actual results, performance or achievements to differ materially from those expressed or implied by these forward-looking statements. The forward-looking statements in this presentation are made only as of the date hereof. 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 the Company in general, see the Company's periodic filings with the Securities and Exchange Commission (the "SEC"), including its Annual Report on Form 10-K for the year ended December 31, 2019, its Quarterly Report on Form 10-Q for the quarter ended September 30, 2020, and any current and periodic reports filed thereafter. Except as required by law, the Company assumes no obligation and does not intend to update these forward-looking statements or to conform these statements to actual results or to changes in the Company's expectations.

This presentation concerns anticipated products that are under clinical investigation and which have not yet been approved for marketing by the U.S. Food and Drug Administration (FDA). It is currently limited by Federal law to investigational use, and no representation is made as to its safety or effectiveness for the purposes for which it is being investigated. Safe Harbor Statement 2

Target 2021 Synthetic Lethality Catalysts

IDE397 IND-filed, Best-in-Class Profile

Present +40 MTAP-deletion PDX Study data

Phase 1 FPI and Clinical Pharmacodynamic Data

Enable Clinical Combo w/ GSK Type I PRMT

Select PARG Development Candidate

Select Pol Theta Development Candidate

IDEAYA SL Investor Day hosted with GSK 3 IDEAYA Biosciences Highlights Broad potential First-in-Class SL Pipeline advancing to the clinic and development candidate stage, including IDE397 (MAT2A), PARG, & Pol Theta

Pharma Collaborations with Pfizer & GSK, with over ~$3 billion in potential milestones

Strong Balance Sheet with ~$288M in cash anticipated to fund operations into 2024 1

NASDAQ: IDYA Leading Synthetic Lethality (SL) focused biotechnology company advancing transformative precision medicine therapies for cancer patients (1) IDEAYA Form 10Q - Q3 2020 Financials

Synthetic lethality occurs when the simultaneous perturbation of two genes results in cell death

Synthetic lethal interactions with tumor-specific mutations (biomarker) may be exploited to develop anticancer therapies

Large-scale screening for synthetic lethal targets has progressed through advances in molecular biology (e.g., RNA interference, CRISPR-Cas9 editing) Synthetic Lethality 4 The Next Frontier in Precision Medicine Oncology Synthetic Lethality provides a powerful approach to discover novel precision medicine therapies with patient biomarkers, including MTAP-deletion (~15% of solid tumors), BRCA/HRD (Breast, Prostate, Ovarian), and high-MSI (15% GI Cancers) Reference: Charles Boone Nature Reviews Genetics, Vol. 18, 2017, Hieter, et al Nature REVIEWS GENETICS Mitochondria Ribosome & translation RNA processing Chromatin & transcription Nuclear-cytoplasmic transport Nuclear migration & protein degradation Mitosis & chr. segregation Cell polarity & morphogenesis Protein folding & glycosylation Cell wall biosynthesis Secretion & vesicle transport Metabolism & amino acid biosynthesis Peroxisome

IDEAYA's Precision Medicine Oncology Pipeline 5 Building the Industry Leading Synthetic Lethality Focused Biotechnology Company Precision Medicine Pipeline Pursuant to GSK Collaboration, Option and License Agreement: MAT2A and WRN: 50/50 US Profits + ex-US Royalties; Polq: Global Royalties

Pursuant to CRUK Evaluation, Option and License Agreement, with ongoing Collaborative Research; IDEAYA controls all Commercial Rights

Pursuant to Pfizer Clinical Trial Collaboration and Supply Agreement; IDEAYA retains all IDE196 Commercial Rights

DDT = DNA Damage Target, WRN = Werner Helicase, Polq = DNA Polymerase Theta, HRD = homologous recombination deficiency, MSI = microsatellite instability

PKC = protein kinase C, MUM = metastatic uveal melanoma (1) (1) (1) (2) (3) Synthetic Lethality Kinase Target Program Milestone through 2021 Modality/Indication Biomarker Preclinical IND Enabling Phase 1 Phase 2021 Goals Collaboration IDE397 MAT2A PARG Pol Theta WRN Platform IDE196 PKC Solid Tumors Monotherapy Solid Tumors Type I PRMT Combo Solid Tumors Additional Combos Breast Cancer Small Molecule Solid Tumors Protein Degrader Solid Tumors GI Cancers Solid Tumors Basket non-MUM Monotherapy MUM MEK & cMET Combo MTAP MTAP MTAP Defined Biomarker HRD HRD High-MSI Novel Biomarker GNAQ/11 GNAQ/11 Phase 1 FPI and Clinical Pharmacodynamic Data Preclinical Data to enable GSK3368715 Combo Preclinical Data to enable additional Combos Select Development Candidate Select Development Candidate Chemistry Lead Optimization Chemistry Lead Optimization Lead Series ID (DNA Damage Targets) New Target / Biomarker Validation Interim Clinical Data MEK Combo Interim Clinical Data (1) (2) (1) (1) Pfizer (3) gsk CANCER RESEARCH UK gsk gsk

IDEAYA Team and Scientific Advisory Board 6 Proven Team & Scientific Thought Leaders in Precision Medicine Oncology IDEAYA Executives & R&D Leadership IDEAYA Scientific Advisory Board Yujiro Hata, M.B.A. President, Chief Executive Officer, Director Paul Stone, J.D. SVP, Chief Financial Officer Michael Dillon, Ph.D. SVP, Chief Scientific Officer Head of Research Mark Lackner, Ph.D. SVP, Head of Biology & Translational Sciences Mick O'Quigley, M.B.A. VP, Development Operations Paul Barsanti, Ph.D. VP, Head of Drug Discovery Jason Throne, J.D. SVP, General Counsel

Alan D'Andrea, M.D. IDEAYA SAB Chair Harvard Medical School, Professor

Director, Center of DNA Damage and Repair, Dana Farber William Sellers, M.D. Broad Institute, Dana Farber, and Harvard, Professor

Novartis, Former Head Oncology Research, SL Project Drive initiative Frank McCormick, Ph.D. UCSF, Professor and former Director, Helen Diller Cancer Center

Former President AACR; Founder and CSO, Onyx Trey Ideker, Ph.D. UCSD, Professor, Co-Director Cancer Genomes & Networks Program, Research in Dual-CRISPR and SL interaction maps Jeffrey Hager, Ph.D. Former Chief Technology Officer, IDEAYA Elizabeth Swisher, M.D. University of Washington, Professor; Co-Leader, Breast and Ovarian Cancer Research Program, Seattle Cancer Care Alliance

Principal Investigator on multiple PARP inhibitor trials Brian Daniels, M.D. Bristol Myers Squibb, Former SVP Global Development & Medical Affairs

IDEAYA and GSK Strategic Partnership 7 Landmark Partnership in Synthetic Lethality Validates IDEAYA Synthetic Lethality platform

Creates 3 strategic combination opportunities

Advancing small molecules & protein degraders Transformative Strategic Partnership

$20M equity investment as direct private placement

$50M option exercise fee for MAT2A

Over $3 billion in potential Milestone Payments, including approximately $1 billion per program

50/50 US profit share for MAT2A and Werner Helicase

20% development cost share for US profit share

Royalties high single-digit to sub-teen double digit % Key Partnership Terms Pol Theta (BRCA/HRD)

Werner Helicase (MSI High) MAT2A (MTAP Deletion) Combo with GSK's Zejula , a commercial PARP inhibitor

GSK covers all Costs

Global Royalties and ~$1B potential Milestone Payments Combo with GSK3368715 (Ph1), a Type I PRMT inhibitor

$50M Option Fee, 50/50 US Profit Share & ex-US Royalties

~$1B potential Milestone Payments IDEAYA Form 8-K current report filed with the U.S. Securities and Exchange Commission on June 16, 2020; GlaxoSmithKline Q2 2020 Earnings Presentation Combo with GSK's Dostarlimab, a PD-1 IO agent

50/50 US Profit Share and ex-US Royalties

~$1B potential Milestone Payments

8 SL Target & Biomarker Discovery and Validation Bioinformatics, including AI Algorithms

Dual CRISPR, CRISPR, siRNA

Genetically Engineered Models

Drug Discovery and Pharmacological Validation Structure Based Drug Design

Small Molecule Chemistry

Protein Degrader Capabilities 1st-in-class SL targets identified, such as Werner Helicase, Pol Theta and PARG

DECIPHER - Dual CRISPR SL Library in DDR in collaboration with UCSD

PAGEO - Paralogous Gene Evaluation in Ovarian in collaboration with Broad Institute Crystal structures for four SL programs obtained to enable structure-based design

Potential best-in-class molecules discovered, including IDE397

Protein degraders advancing for selected targets, including Pol Theta Translational Research and Opportunity Expansion Genomics - DNA and RNA Analysis

Proteomics - Protein Expression Profiling

Tissue (IHC, IF) and Liquid Biopsies Analysis IDEAYA Synthetic Lethality Platform Translational research to define clinical biomarkers

Opportunity expansion through broad cell panel screening

PD biomarker analysis to confirm target modulation and correlation with clinical activity Fully-Integrated Target, Biomarker, Drug Discovery and Translational Capabilities

Partnership Datasets

Cancer Dependency Map - Broad Institute

Foundation Insights - Foundation Medicine

9 IDEAYA Synthetic Lethality Platform Synthetic Lethality Target and Biomarker Discovery and Validation DECIPHER

Dual CRISPR SL Library in DNA Damage Repair (2) PAGEO

Paralogous Gene Evaluation in Ovarian Cancer (1)

IDEAYA data mining and analysis across data sets Evaluation of SL targets in context of functionally redundant paralogous genes in ovarian cancer Evaluation of DNA Damage Targets synthetic lethal with tumor suppressor or oncogenes Synthetic Lethality Target Discovery & Validation Platform

IDEAYA SL Platform integrates extensive proprietary and public data sets with orthogonal and complementary content

Bioinformatic analysis enables identification and validation of synthetic lethal target / biomarker interactions across vast datasets

Robust SL interactions validated genetically (Dual CRISPR, paralogues, isogenic pairs, CRISPR/siRNA), pharmacologically, & in vivo (1, 2) IDEAYA Proprietary Libraries and Datasets - Strategic Collaborations with Broad Institute(1) and UC San Diego(2)

10 IDEAYA Synthetic Lethality Platform Synthetic Lethality Target and Biomarker Discovery and Validation DECIPHER

Dual CRISPR SL Library in DNA Damage Repair (1) Evaluation of DNA Damage Targets synthetic lethal with tumor suppressor or oncogenes DECIPHER Dual CRISPR Proprietary Synthetic Lethality Library (1) Developed in Collaboration with UCSD, Principal Investigator - Dr. Trey Ideker DECIPHER

~225 Non-Overlapped Genes

~12,000 Gene Pairs per Cell Line 67 TSG/OG's and 176 DDR Targets

Curated Breast / Lung Cell Lines DECIPHER Genes

>20 Novel Drug Targets Identified

Target Validation Ongoing

IDE397 (MAT2A/MTAP) Lead SL Program IND Filed

Potential First-in-Class Monotherapy and First-in-Class / Best-in-Class Combination Therapies (Type I PRMT, Taxanes)

Targeting PARG and Pol Theta Development Candidates in 2021

PARG monotherapy efficacy in multiple tumor types; Pol Theta + PARPi combination regressions in BRCA2-/- xenograft

IDEAYA Synthetic Lethality Investor Day 2021

IDEAYA to host with GlaxoSmithKline IDEAYA is Advancing the Next Generation of Potential First-in-Class Synthetic Lethality Programs 11 IDEAYA Synthetic Lethality Pipeline IDE397 (MAT2A)

High-MSI SL Platform

SL Targets Pol Theta

Novel Biomarker HRD = Homologous Recombination Deficiency, MSI = Microsatellite Instability

MTAP Deletion Prevalence MTAP-MAT2A Synthetic Lethality Biology MAT2A Inhibition is Synthetic Lethal with MTAP Deletion 12 MTAP Deletion Prevalence ~15% of all Solid Tumors Data from The Cancer Genome Atlas in cBioPortal MAT2A MAT2A inhibitor MAT2A Methionine MAT2A is key enzyme that produces SAM in cells SAM PRMT5 MTAP Protein Methylation MTAP deletion leads to MTA accumulation MTA accumulation partially inhibits PRMT5 Loss of methylation function of PRMT5 results in defects in RNA splicing, gene expression and genome integrity Inhibition of MAT2A results in reduction of SAM, starving PRMT5 of its substrate Cancer Type N MTAP Deletions (%) Glioblastoma 592 41 Mesothelioma 87 32 Esophageal 95 28 Bladder 411 26 Pancreatic 184 22 Melanoma 448 16 Lung Cancer (NSCLC) 1053 15 Head and Neck 523 14 Sarcoma 255 10 Esophagogastric 514 10 Diffuse Glioma 513 9 Breast 1084 3 Ovarian 585 3 Adrenocortical 92 3 Thymic 123 3 Hepatocellular 369 3 Renal non-clear cell 348 2

IDE397: MAT2A Development Candidate 13 Clinical Evaluation of IDE397 - Differentiated Profile and Selective for MTAP-/- Cell Lines

IDE397 demonstrates in vivo efficacy and PD modulation at 5 to 30mg/kg

AG270 published preclinical dose typically 200mg/kg 1

IDE397 has not caused preclinical liver injury or increased bilirubin

Liver injury not observed in tox studies

Not an inhibitor of UGT1A1 (AG270 noted to inhibit UGT1A1) 1

IDE397 has favorable physical properties, including solubility

AG-270 observed non-linear exposure >200mg QD (GI absorption)

IDE397 Target Product Profile IDE397 is Selective for MTAP-/- Cell Lines IDEAYA Data MTAP-/- cell lines are sensitive to IDE397

MTAP WT cell lines are insensitive

Pharmacological inhibition correlates with MAT2A genetic knockdown Log10 GI50 ( M) Log10 IC50 ( M) (1) Agios, AACR 2019, Keystone 2019, Triple Meeting 2019 (Webcast Call Q&A) Increased sensitivity to IDE397 treatment Increased dependence on MAT2A gene knockdown MTAP WT MTAP-/- SW1573 COLO741 BxPC3 SKMEL5 HuPT3 LMSU SW780 KP4 SNU449 RT 112 NCIH 833 BFTC909 -1.0 -0.5 0.0 0.5

14 Monotherapy Tumor Regressions & Significant TGI Across Multiple Solid Tumor Types 1 Esophageal PDX Model Gastric PDX Model Bladder PDX Model IDE397 PDX Study of >40 MTAP-/- Models in Multiple Indications IDE397 evaluation in Patient Derived Xenograft (PDX) models with homozygous MTAP deletions in Solid Tumors

Tumor Regressions (> 100% TGI) observed in multiple PDX models and across multiple indications

> 75% Tumor Growth Inhibition (TGI) observed in ~ 50% of models and across major solid tumor types IDEAYA Data IDEAYA Data IDEAYA Data (1) IDEAYA PDX Study data targeted to be presented in peer-reviewed setting in 2021 Mean Tumor Volume (mm3) S.E.M. 1200 1000 800 600 400 200 0 7 14 21 28 1st dose Day 0 Study Day Vehicle IDE397 30mg/kg QD Mean Tumor Volume (mm3) S.E.M. 1200 1000 800 600 400 200 0 7 14 21 28 35 1st dose Day 0 Study Day Vehicle IDE397 30mg/kg QD Mean Tumor Volume (mm3) S.E.M. 1200 1000 800 600 400 200 0 7 14 21 28 1st dose Day 0 Study Day Vehicle IDE397 30mg/kg QD