Sutro Biopharma, Inc. · NASDAQ:STRO

Sutro Biopharma — SGO 2025 Annual Meeting on Women's Cancer

13 slides from Sutro Biopharma's conference presentation, March 2025

1. Slide 1: Efficacy and safety of luveltamab tazevibulin in platinum-resistant ovarian cancer: dose-optimization results

   Efficacy and safety of luveltamab tazevibulin in patients with recurrent platinum-resistant ovarian cancer: results from the dose-optimization stage of the REFRαME-O1 (GOG-3086, ENGOT-79OV, and APGOT-OV9) phase 2/3 study Jung-Yun Lee1, Ana Oaknin2, Domenica Lorusso3, Kidong Kim4, Lucy Gilbert5, Yeh

2. Slide 2: Financial Disclosure for: Prof Jung-Yun Lee

   Financial Disclosure for: Prof Jung-Yun Lee I have the following financial relationships with ACCME defined ineligible companies to report over the past 24 months: ❖ Personal financial interests • Lectures – AstraZeneca, Eisai, GSK, MSD, Roche, Takeda • Role as Advisory board positions – AstraZeneca

3. Slide 3: Unlabeled / Investigational Uses

   Unlabeled / Investigational Uses I will be discussing an investigational use of a pharmaceutical product. This presentation describes the outcomes from Phase 2 (dose optimization) of a phase 2/3 study of luveltamab tazevibulin currently under investigation for use in platinum-resistant ovarian cance

4. Slide 4: Background

   Background Luveltamab tazevibulin (luvelta) is a novel tubulin-ADC designed to target cancers with broad range of FRα expression, including recurrent PROC ❖ STRO-002-GM1: promising clinical efficacy with manageable safety profile • ORR of 43.8% (5.2 mg/kg) and 31.3% (4.3 mg/kg) in patients with recu

5. Slide 5: Study Design

   (GOG-3086, ENGOT-79OV, and APGOT-OV9) Study Design Phase 3: Currently enrolling Phase 2: Phase 3: Eligibility Key Endpoints Dose Optimization Randomized Trial • PROC Luvelta dose A: Luvelta 5.2 • Primary analysis 5.2 mg/kg IV Q3W + N= mg/kg IV Q3W + – Primary endpoint: PFS • 1–3 prior lines N=25 pro

6. Slide 6: Phase 2 Patient Disposition

   Phase 2 Patient Disposition Screening FRα expression Enrolled (N=57) • ≥25% by TPS: 82% • ≥75% by PS2+: 42% Tx Luvelta 4.3 mg/kg Tx Luvelta 5.2 mg/kg n=29 n=28 Tx discontinued Tx discontinued n=25 (86%) n=22 (79%) Tx discontinuation ❖ Progressive disease: 68.4% • 4.3 mg/kg: 65.5% • 5.2 mg/kg: 71.4%

7. Slide 7: Patients: Baseline Characteristics

   Patients: Baseline Characteristics Starting dose 4.3 mg/kg Starting dose 5.2 mg/kg Characteristic N=29 N=28 Median age, years (range) 59.0 (42–81) 60.5 (41–81) ECOG PS, n (%) 0 17 (58.6) 14 (50.0) 1 12 (41.4) 14 (50.0) Baseline characteristics were Median lines of prior 2 (1–3) 2 (1–3) generally bal

8. Slide 8: Efficacy: Selected Dose of 5.2 mg/kg + G-CSF Followed by 4.3 mg/kg Showed Higher Response Rate

   Efficacy: Selected Dose of 5.2 mg/kg + G-CSF Followed by 4.3 mg/kg Showed Higher Response Rate Starting Dose Starting Dose Tumor response 5.2 mg/kg 4.3 mg/kg (efficacy evaluable)* N=25* N=29 Change in tumor size from baseline ,% Best response, n (%) CR 1(4.0) 0 PR 7 (28.0)** 4 (13.8) SD 17 (68.0) 16

9. Slide 9: Early Onset of Responses After 2 Cycles of 5.2mg/kg and Sustained Treatment at 4.3 mg/kg

   Early Onset of Responses After 2 Cycles of 5.2mg/kg and Sustained Treatment at 4.3 mg/kg Dose Data set: REFRαME-O1 Part 1, 5.2 mg/kg, ITT, n=28 CR, complete response; PR, partial response; Q3W, every 3 weeks.

10. Slide 10: Luvelta Demonstrated Consistent Efficacy in PROC for High and Low/Medium FRα Expression

    Luvelta Demonstrated Consistent Efficacy in Patients with PROC for High and Low/Medium FRα Expression * Data Set REFRαME-O1 Phase 2 (Efficacy Evaluable) (FRα ≥ 25% by TPS) Dose Cohort 5.2 mg/kg (N=25) PS2+ ≥75% PS2+ <75% n=13 n=12 ORR 30.8% 33.3%** (95% CI) (9.1%, 61.4%) (12.3%, 60.9%) DCR 100% 91.7

11. Slide 11: Most Common TEAEs Were Grade 1-2 Arthralgia, Nausea, and Constipation

    Most Common TEAEs Were Grade 1-2 Arthralgia, Nausea, and Constipation Starting dose 4.3 mg/kg Starting dose 5.2 mg/kg Total population TEAE, n (%) N=29 N=28 N=57 All grade Grade ≥3 All grade Grade ≥3 All grade Grade ≥3 Patients with ≥1 TEAE 29 (100) 19 (65.5) 28 (100) 22 (78.6) 57 (100) 41 (71.9) Ar

12. Slide 12: Conclusions

    Conclusions ❖ The optimized dose of luvelta was selected as 5.2 mg/kg + G-CSF x 2 cycles then 4.3 mg/kg • Improved ORR, low discontinuation rate, and similar safety profile compared to 4.3 mg/kg starting dose ❖ Luvelta demonstrated clinical anti-tumor activity in PROC with FRα ≥25% • Consistent in d

13. Slide 13: Acknowledgements and Disclosures

    Acknowledgements and Disclosures ❖ The authors and Sutro Biopharma thank all the patients participating in this trial ❖ Sutro Biopharma funded this study and participated in the study design, research, analysis, data collection, interpretation of data, review, and approval of the presentation ❖ Medi

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