Exhibit 99.1

 

		An Open-Label, Multicenter Phase 1/2 Dose Escalation and Expansion Study of THOR-707 as a Single Agent and in Combination with Pembrolizumab in Adult Subjects with Advanced or Metastatic Solid Tumors David Luo;1 Raghad Abdul-Karim;2 Arun Azad;3 Joanna Bendell;4 Hui Gan;5 Filip Janku;6 Shiraj Sen;7 Tira Tan;8 Judy Wang;9 Lisa Schechet;1 Lauren Baker;1 Joseph Leveque;1 Tarek Meniawy10 1Synthorx, Inc., La Jolla, CA; 2NEXT Oncology, Texas Oncology, San Antonio, Tx; 3Peter MacCallum Cancer Centre, Melbourne, Victoria, Aus; 4Sarah Cannon Research Institute/Tennessee Oncology, Nashville, TN; 5Austin Health, Olivia Newton-John Cancer Research Institute, Melbourne, Victoria, Aus; 6Investigational Cancer Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, TX; 7Sarah Cannon Research Institute at HealthONE, Denver, CO; 8Division of Medical Oncology, National Cancer Centre Singapore; 9Sarah Cannon Research Institute/Florida Cancer Specialists, Sarasota FL; 10Linear Clinical Research, Nedlands, Western Australia, Australia

BACKGROUND Synthorx Expanded Genetic Code Platform: A Synthetic DNA Base Pair Encodes Novel Amino Acids to Create Optimized Biologics X-Y Base Pair Creates New Codons That Specifically Encode Novel Amino Acid Chemistry Into Proteins Site-Specific Bioconjugation " Novel amino acid installation creates a dedicated, specific and stable chemical attachment site " Designed to bioconjugate moieties for improved properties: e.g. PEG Specificity " Improved target selectivity through altered receptor binding Polymer-Conjugates " Increased half-life " Epitope shielding through covalent and stable PEG attachment via bio-orthogonal chemistry Engineered Cells Install a Novel Amino Acid Utilizing X-Y to Produce Therapeutic Proteins with Optimized Properties Production System for Synthorins in E. coli Novel Amino Acid enters cells; used X and YTPs enter via by aminoacyl tRNA synthetase to transporter charge X-Y tRNAs X-Y containing plasmids encode product with X-Y codon and matching X-Y tRNA gene mRNA with X-Y codon matches with tRNA displaying anticodon Translation machinery decodes X-Y codons to introduce nAA into Synthorin proteins Dual Pharmacology of IL-2 is Mediated by 23 and 23 Receptor Sub-Types Receptor Immune Cells Immune Type Activated Response 2 3 Suppression High affinity Treg -11 CD4+ Treg up-regulation a (Kd ~ 10 M) Tcon Suppression Primarily Treg IL-2 2 3 Stimulation Intermediate affinity Tcon Proliferation of Tcon (K ~ 10-9M) reactive to Auto-antigens d Broadly expressed CD4 Th, CD8+ T, and NK cells

THOR-707 Strong Preclinical Rationale for Moving THOR-707 into Clinical Drives CD8+ Teff Cell Expansion and Tumor Infiltration at Levels Comparable to Tumor Microenvironment Re-Programmed Following Treatment Development Immune Checkpoint Inhibitors With THOR-707; Enhanced When Combined with Anti-PD-1 " THOR-707, as a single agent, elicits CD8 T cell activation and tumor infiltration, Select Immune Checkpoint Inhibitors THOR-707 including effector and memory subtypes, and improved survival. In combination with anti-PD-1, THOR-707 leads to durable anti-tumor responses and rejection * * * * * * upon re-challenge 80 Predose Predose TIL 60 " THOR-707 does not significantly expand Tregs, nor does it lead to increases in 3 mg/kg T of 60 eosinophils in NHPs % These results suggest that THOR-707 may CD3+ 40 " THOR-707 + anti-PD1 increases T Cell Receptor-mediated IFN-3 release which 40 in reprogram the tumor microenvironment to suggests that the combination strongly activates effector T cells; IFN-3 is a key Teff% express checkpoint inhibitory receptors (PD-1, in inducer of tumor antigen presentation CTLA-4) and ligands (PD-L1, PD-L2), 20 8+ 20 " On the other hand, anti-PD-1 did not increase IFN-3 release observed with THOR- CD8+ CD potentially reversing PD-1i/PD-L1i resistance 707 ex vivo, suggesting a low risk to exacerbate auto-immune effects of anti-PD-1s These results suggest that an IFN-3 mediated 0 0 " THOR-707 +/- anti-PD-1 does not induce release of cytokines associated with VLS Untreated Fvax CTLA-4 PD-1 PD-L1 PD-1 + Day 0 Day 1 Day 2 Day 3 Day 5 Day 7 Day 10 effect from the combination of THOR-707 and a CTLA-4 PD-1i may potentiate antigen-driven TCR or cytokine release syndrome (CRS) Following 3 Doses IV of CPIs Following Single Dose of THOR-707 responses in T effector cells and neoantigen " Similar exposure levels observed vs re-dosing in non-human primates: no B16F10 Model1 B16F10 model presentation via MHC expression to overcome indication of anti-drug antibodies PD-1i resistance in some refractory phenotypes

STUDY DESIGN Dose Escalation (3+3 Design) Dose Expansion Part 1 Part 3 THOR-707 Single Agent Single Agent and Combination Basket Studies in Select Populations All Comers Population Additional Optimal Single THOR-707 Q3W RP2D Dose Levels Agent and Dose Level N Cohort D Cohort A up to the Combination Dose 16 ug/kg MTD and Frequency - THOR-707 Single Agent RP2D THOR-707 8 ug/kg Recommended Q2W or Q3W Q3W Additional Phase 2 Dose THOR-707 Q2W RP2D Dose Levels Dose Level N (RP2D) up to the Cohort B MTD Dose Level 2 THOR-707 8 ug/kg Q2W Part 2 Cohort E THOR-707 + Anti-PD-1 Combo Combo RP2D Anti-PD-1 Sensitive Populations Combo RP2D Additional Q3W Dose Levels Q3W Dose Level N up to Cohort C Dose Level 2 the MTD Combo Q3W Dose Level 1 Clinical Sites Key Biomarkers CD8+ T effector cell counts in the periphery Ki67 expression levels CD4+ T regulatory cell counts NK cell counts in the and in the tumor microenvironment in peripheral blood immune cells in the periphery and in the periphery and in the tumor (Expansion to 1.5x above baseline the threshold for considering (Expression level between 40% and 60% the threshold for tumor microenvironment microenvironment a combination with a PD-1i) considering a combination with a PD-1i)

STUDY OBJECTIVES Primary Objectives: Secondary Objectives: " Evaluate the safety and tolerability of THOR-707 as a " Evaluate preliminary anti-tumor activity of THOR-707 as a single agent and in combination with a checkpoint inhibitor single agent and in combination with a checkpoint inhibitor (identify DLTs, AEs/serious adverse event profile) by determination of the ORR defined according to RECIST " Define the MTD and/or the RP2D of THOR-707 as a single Version 1.1 agent and in combination with a checkpoint inhibitor " Determine TTR, DOR,PFS, OS, and DCR of THOR-707 as a single agent and in combination with a checkpoint inhibitor STUDY ENROLLMENT " Each cohort will enroll approximately 3-6 subjects as per protocol. Up to 3 cohorts (dose schedules) may be open simultaneously " Once a dose level is declared safe and adequate PD activity is demonstrated at that dose level, up to 10 additional subjects may be enrolled into a Safety Expansion Cohort at the discretion of the Safety Review Committee (SRC) " After reaching the MTD and/or defining the RP2D, up to 15 additional subjects may be enrolled at the RP2D of the respective dosing schedule to further evaluate safety, pharmacodynamic effects, and anti-tumor activity Key Inclusion Criteria: Key Exclusion Criteria: " Males or females aged e18 years at " Inadequate washout from prior systemic anti-cancer therapy, surgery, and/or radiation screening " Primary central nervous system or leptomeningeal disease " ECOG performance status of 0 or 1 " Active autoimmune disease requiring systemic treatment within the past 3 months or " Life expectancy greater than or equal documented history of clinically severe autoimmune disease that requires systemic to 12 weeks as determined by the steroids or immunosuppressive agents Investigator " Abnormal pulmonary function " Histologically or cytologically confirmed " Active second malignancy, or history of previous malignancy that would impact the diagnosis of advanced and/or metastatic assessment of any study endpoints solid tumors with at least one tumor History " of allogenic or solid organ transplant lesion with location accessible to safely " Uncontrolled diabetes mellitus or other uncontrolled immune-related endocrinopathies biopsy per clinical judgment of the " Known HIV or active infection with hepatitis B or C Investigator " Clinically significant bleeding d2 weeks prior to initial THOR-707 dose " Measurable disease per RECIST v1.1 " Refusal of SOC, no reasonable SOC " Deep vein thrombosis or pulmonary embolism d3 months available, or standard therapy intolerable, " Severe or unstable cardiac condition d6 months prior to study treatment not effective, not accessible " Grade 3 or higher immune-related toxicity from prior immuno-oncology therapy " Prior anti-cancer therapy is allowed, " Is pregnant or breastfeeding, or expecting to conceive or father children within the including prior immunotherapy treatment, projected duration of the trial as long as any treatment related toxicity " History of non-pharmacologically induced prolonged corrected QT interval is resolved to an appropriate level. " Any serious medical condition (including pre-existing autoimmune disease or " Adequate cardiovascular, hematological, inflammatory disorder), laboratory abnormality, psychiatric condition, or any other liver, and renal function significant or unstable concurrent medical illness that in the opinion of the Investigator " Adequate laboratory parameters would preclude protocol therapy or would make the subject inappropriate for the study SAFETY SUMMARY " AEs (type, incidence, severity, HAMMER is a three-part global Phase 1/2 dose escalation and expansion timing, seriousness, and study evaluating the safety and anti-tumor activity of THOR-707, our Synthorin relatedness) not-alpha IL-2, in patients with advanced or metastatic solid tumors: " Vital sign measurements (blood " Part 1 of the study will determine the RP2D of THOR-707 as a single agent pressure, pulse, respiratory rate, " Part 2 of the study will determine the RP2D of THOR-707 in combination body temperature, pulse oximetry) with a PD-1 inhibitor " Physical examinations " Part 3 of the study will continue to evaluate safety along with the efficacy of " Clinical laboratory tests THOR-707 alone or in combination with a PD-1 or PD-L1 inhibitor as well as " Electrocardiograms in combination or sequenced with other established and emerging " Concomitant medications and immunooncology therapies via dose expansion procedures, including all supportive Safety and tolerability data at the 8 ug/kg Q3W starting dose were reviewed care provided by the Safety Review Committee and the study is currently enrolling subjects at 16 ug/kg Q3W and 8 ug/kg Q2W; the threshold for advancing Part 2 of the study in combination with a PD-1i was exceeded in the first cohort.