Os Therapies Incorporated · AMEX:OSTX
Os Therapies — Biomarker-focused Conference Call (April 2026)
35 slides from Os Therapies's conference presentation, Apr 30, 2026
Slide 1: Biomarker-focused Conference Call
Biomarker-focused Conference Call April 30, 2026 NYSE American: OSTX
Slide 2: Safe Harbor Statement
Safe Harbor Statement This document contains forward-looking statements. In addition, from time to time, we or our representatives may make forward-looking statements orally or in writing. We base these forward-looking statements on our expectations and projections about future events, which we deri
Slide 3: Agenda
Agenda 1. Introduction – Harrison Seidner, PhD 2. Corporate Update – Paul Romness, MPH 3. Biotech Innovation Curve – Dr. Robert Langer 4. Clinical, Biomarker and Safety Data – Andrew Exley, MD, FRCP, FRCPath 5. Regulatory status by Jurisdiction (Europe, Australia, U.K. and U.S.) – David Brindley, Ph
Slide 4: Agenda
Agenda 1. Introduction – Harrison Seidner, PhD 2. Corporate Update – Paul Romness, MPH 3. Biotech Innovation Curve – Dr. Robert Langer 4. Clinical, Biomarker and Safety Data – Andrew Exley, MD, FRCP, FRCPath 5. Regulatory status by Jurisdiction (Europe, Australia, U.K. and U.S.) – David Brindley, Ph
Slide 5: Agenda
Agenda 1. Introduction – Harrison Seidner, PhD 2. Corporate Update – Paul Romness, MPH 3. Biotech Innovation Curve – Dr. Robert Langer 4. Clinical, Biomarker and Safety Data – Andrew Exley, MD, FRCP, FRCPath 5. Regulatory status by Jurisdiction (Europe, Australia, U.K. and U.S.) – David Brindley, Ph
Slide 6: Agenda
Agenda 1. Introduction – Harrison Seidner, PhD 2. Corporate Update – Paul Romness, MPH 3. Biotech Innovation Curve – Dr. Robert Langer 4. Clinical, Biomarker and Safety Data – Andrew Exley, MD, FRCP, FRCPath 5. Regulatory status by Jurisdiction (Europe, Australia, U.K. and U.S.) – David Brindley, Ph
Slide 7: Osteosarcoma: Clinical Outline
Osteosarcoma: Clinical Outline • Major form of pediatric bone cancer • ~1,000 cases diagnosed annually in US • Primarily affects adolescents & young adults: 12 – 39 yrs • Localized disease • Chemotherapy & Surgery can sometimes achieve remission • Recurrent / Metastatic disease e.g. in Lungs • No FD
Slide 8: Age-Related Incidence of Primary & Subsequent Osteosarcoma
Age-Related Incidence of Primary & Subsequent Osteosarcoma Cole 2022
Slide 9: Overall Survival in Primary Osteosarcoma: No Improvement in 30 years
Overall Survival in Primary Osteosarcoma: No Improvement in 30 years Cole 2022
Slide 10: Overall Survival in Metastatic Osteosarcoma: No Improvement in 30 years
Overall Survival in Metastatic Osteosarcoma: No Improvement in 30 years Cole 2022
Slide 11: OST31-164: Innovation – Novel Immunotherapy
OST31-164: Innovation – Novel Immunotherapy 1. 1st in class microbial vector gene therapy (MVGT) • Attenuated Listeria (Lm) bearing plasmids encoding chimeric fusion protein • Truncated Listerolysin: promotes Ag presentation & acts as adjuvant * • Tumour-associated antigen (TAA): Her2 2. Triggers a
Slide 12: How OST-HER2 works
How OST-HER2 works Her2 Expression in BREAST & OVARIAN CANCER Her2 Expression in OSTEOSARCOMA (BONE CANCER) A Cell membrane cytoplasm Few Her2 molecules at cell surface cytoplasm HER2 receptor: Upregulated NUCLEUS NUCLEUS HER2 expressed in cell cytoplasm Nucleus Processed into peptides, captured by
Slide 13: How OST-HER2 works
How OST-HER2 works 1 2 3 4 5 CD8+ NK MHC I CD4+ NK CD8+ HER2 Helper T NK cell Killer T MHC I DC MHC II TUMOUR Mono DC CELL L. monocytogenes (Lm) Attenuated Macro- phage Monocyte Dendritic cell HER2-tLLO payload HER2 peptide Treg MDSC The Construct Trojan Horse Entry Peptide-MHC Array Suppressors neu
Slide 14: Biomarker strategy and trial findings
Biomarker strategy and trial findings Gene transcript modulation as the preferred biomarker of response to OST-HER2 (OST31-164) ✕ ✓ Why Gene Transcript Modulation? Why Not ELiSpot Alone? 1 3 Canine trials: clinical benefit but no correlation 2 with HER2-specific T cells by ELiSpot Captures full resp
Slide 15: Her2 Expression by ImmunoHistoChemistry in Relapsed Osteosarcoma
Her2 Expression by ImmunoHistoChemistry (CB11 murine mAb to intracellular domain AA 1244–1249) in Relapsed Osteosarcoma Osteosarcoma 85% Tumour Cells Her2 +ve Her2 positive (Percent) Her2 -ve Reed 2025 EMA UPDATES – APRIL 2026 15
Slide 16: OST31-164: Proof of Principle: Comparative Oncology
OST31-164: Proof of Principle: Comparative Oncology 3. NIH supported collaboration with comparative oncology experts demonstrates efficacy of OST31-164 in spontaneous osteosarcoma in canines
Slide 17: Canine Osteosarcoma: Parallels with Human Osteosarcoma
Canine Osteosarcoma: Parallels with Human Osteosarcoma I. Spontaneous onset in immunocompetent dogs: rate >10x human rate II. Many clinical, biological, and molecular features in common i. Primary lesion: typically, high-grade tumours in long bones ii. Standard treatment: chemotherapy & radical surg
Slide 18: Immunological responses and clinical outcomes in dogs with osteosarcoma
Immunological responses and clinical outcomes in dogs with osteosarcoma receiving SOC + ADXS31-164 Mason NJ 2025
Slide 19: Canine Osteosarcoma Elite vs Short-term Survivors: Differentially Expressed Genes
Canine Osteosarcoma Elite vs Short-term Survivors: PBMCs Differentially Expressed Genes – Baseline vs last ADXS31-164 # # Up-regulation of Cytotoxic T cell, NK cell, & Ag presenting cell gene transcripts Mason NJ 2025
Slide 20: OST31-164-01: Clinical Trial in Recurrent (Pulmonary) Osteosarcoma
OST31-164-01: Clinical Trial in Recurrent (Pulmonary) Osteosarcoma Primary Relapse Disease surveillance Diagnosis Diagnosis imaging every 12 weeks Resection of Resection of Primary Tumor Metastasis & Screening ~ Week 11 Lm Surveillance & Survival follow up for Variable 3 yrs from last OST31-164 inte
Slide 21: OST31-164: Innovation – Historic Controls
OST31-164: Innovation – Historic Controls 4. Justification for use of Historic Controls i. Lack of improvement in OS (Cole 2022) i. Reduces risk of bias thru improvements in Standard Of Care (SOC) ii. Systematic identification of published trials iii. Systematic screening for comparable populations
Slide 22: Rationale for EFS vs Objective Response Rate (ORR)
Rationale for EFS vs Objective Response Rate (ORR) I. Radiographic response may not reflect critical cellular effect II. Surgical resection is standard approach to pulmonary recurrence i.e. no lesion to determine ORR III. Likely difference in drug activity in microscopic vs macroscopic disease IV. P
Slide 23: Rationale for Preferring Overall Survival to Event Free Survival
Rationale for Preferring Overall Survival to Event Free Survival in the Assessment of Immunotherapies for Osteosarcoma 1. Patients value Overall survival over Event Free Survival (Tregear 2024) 2. Regulators prefer Overall Survival as a Hard Endpoint 3. Delayed effect of immunotherapies reduces disc
Slide 24: Measures Reducing Potential Bias in Single Arm Trial of OST31-164
Measures Reducing Potential Bias in Single Arm Trial of OST31-164 Parameter Measures Adopted to Reduce Potential bias 1. Assessment bias Hard endpoints: Overall survival (OS) 2. Attrition bias Overall survival preferred to Event-Free Survival; Sensitivity analyses 3. Pre-planning Statistical analysi
Slide 25: EFS vs OS after Immunotherapy: Single Arm Trial of Denosumab
EFS vs OS after Immunotherapy: Single Arm Trial of Denosumab (RANKL mAb) in Patients with Recurrent / Refractory Osteosarcoma EFS OS Janeway 2026
Slide 26: OS: OST-HER2 Phase 2b Trial vs. Historical Control
OS: OST-HER2 Phase 2b Trial vs. Historical Control
Slide 27: OS: OST-HER2 Phase 2b Trial vs. Pooled Historical Control
OS: OST-HER2 Phase 2b Trial vs. Pooled Historical Control P=0.0344
Slide 28: Isolation of Treatment Effect
Isolation of Treatment Effect • Clinically significant improvement in Overall Survival & EFS I. Highly significant link between Overall Survival & Immune Response Gene Signature (IRGS) after 3rd dose of OST31-164 II. IRGS includes cytotoxic effectors (NK/T cells) & T cell memory, and modulators of T
Slide 29: Immune Response Gene Signatures after 3rd Dose of OST31-164
Immune Response Gene Signatures after 3rd Dose of OST31-164 Link Mechanism of Action to OS in Canine & Human Osteosarcoma • Cox Proportional Hazards Model • Canine IRGS (optimized): p=10e-8 for Overall Survival • Beneficial: Ag presentation, NK cell activation, T cell activation • Detrimental: Type
Slide 30: Kaplan Meier Analysis of Overall Survival by Immune Response Gene Composite
Kaplan Meier Analysis of Overall Survival by Immune Response Gene Composite (Baseline vs Post 3rd Dose) Overall Survival Probability Days from 1st dose (Arrow ~ 2yrs)
Slide 31: Safety Profile
Safety Profile I. Infusion related cytokine release syndrome • Frequency & severity reduced by pre-infusion regimen; no Rx discontinued • IV fluids, antihistamine, NSAID, antiemetic, H2-receptor antagonist Cytokine release syndrome: maximum grade 2 intensity, 1st cycle II. Infection risk • Single ep
Slide 32: Agenda
Agenda 1. Introduction – Harrison Seidner, PhD 2. Corporate Update – Paul Romness, MPH 3. Biotech Innovation Curve – Dr. Robert Langer 4. Clinical, Biomarker and Safety Data – Andrew Exley, MD, FRCP, FRCPath 5. Regulatory status by Jurisdiction (Europe, Australia, U.K. and U.S.) – David Brindley, Ph
Slide 33: Agenda
Agenda 1. Introduction – Harrison Seidner, PhD 2. Corporate Update – Paul Romness, MPH 3. Biotech Innovation Curve – Dr. Robert Langer 4. Clinical, Biomarker and Safety Data – Andrew Exley, MD, FRCP, FRCPath 5. Regulatory status by Jurisdiction (Europe, Australia, U.K. and U.S.) – David Brindley, Ph
Slide 34: Agenda
Agenda 1. Introduction – Harrison Seidner, PhD 2. Corporate Update – Paul Romness, MPH 3. Biotech Innovation Curve – Dr. Robert Langer 4. Clinical, Biomarker and Safety Data – Andrew Exley, MD, FRCP, FRCPath 5. Regulatory status by Jurisdiction (Europe, Australia, U.K. and U.S.) – David Brindley, Ph
Slide 35: Thank you for attending!
Thank you for attending! OS Therapies, Inc. (NYSE American: OSTX)
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