Sutro Biopharma (NASDAQ: STRO) prices $110M stock sale to extend cash runway
Rhea-AI Filing Summary
Sutro Biopharma, Inc. entered an underwriting agreement on February 9, 2026 to sell 7,868,383 shares of common stock at $13.98 per share in an underwritten public offering under its existing shelf registration. The company estimates gross proceeds of about $110.0 million, which, combined with its cash, cash equivalents and marketable securities as of January 1, 2026, is expected to bring total capital resources to approximately $251.4 million.
Sutro plans to use the net proceeds primarily for general corporate purposes, including research, clinical and process development and manufacturing of product candidates, working capital, potential acquisitions or investments, capital expenditures and other corporate needs. Based on its planned use of funds, Sutro estimates this capital will fund operating and capital needs into the second quarter of 2028. The offering is expected to close on February 11, 2026, subject to customary conditions. Sutro is also releasing an updated corporate presentation, which will be available on its website and furnished as an exhibit.
Positive
- Extended cash runway: Gross proceeds of approximately $110.0 million, together with existing cash and investments, are expected to provide about $251.4 million in capital, which the company estimates will fund operating and capital needs into the second quarter of 2028.
- Financing supports broad development plans: Proceeds are earmarked for general corporate purposes, including research, clinical and process development, manufacturing of product candidates, working capital, and potential acquisitions or investments, helping sustain Sutro’s ADC pipeline execution.
Negative
- Equity dilution from new share issuance: The company is issuing and selling 7,868,383 new common shares in an underwritten offering, which increases the share count and dilutes existing stockholders’ ownership percentages.
Insights
Sutro raises $110M equity, extending cash runway into Q2 2028.
Sutro Biopharma has structured a primary equity offering of 7,868,383 shares at $13.98 per share, targeting gross proceeds of about $110.0 million. This capital is layered on top of existing cash, cash equivalents and marketable securities as of January 1, 2026, for an expected total of roughly $251.4 million.
The company states that this funding should cover operating expenses and capital expenditures into the second quarter of 2028. For a clinical-stage biotech with several ADC programs and projected IND milestones in 2026, a multi-year runway can support continued development without immediate reliance on additional financing, though it comes via equity issuance.
Use of proceeds is broad—general corporate purposes, including research, clinical and process development, manufacturing, working capital, and potential acquisitions or investments. The impact on shareholders balances dilution from 7.9 million new shares against reduced near-term financing risk, leaving the overall event as strategically important but mixed rather than clearly favorable or adverse.
8-K Event Classification
UNITED STATES
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Item 1.01 Entry into a Material Definitive Agreement
On February 9, 2026, Sutro Biopharma, Inc. (the “Company”) entered into an underwriting agreement (the “Underwriting Agreement”) with Leerink Partners LLC and TD Securities (USA) LLC, as representatives of the several underwriters named therein (the “Underwriters”), pursuant to which the Company agreed to issue and sell 7,868,383 shares of its common stock (the “Shares”) to the Underwriters (the “Offering”). The Shares will be sold at an offering price of $13.98 per share. The Underwriting Agreement contains customary representations and warranties, conditions to closing, market standoff provisions, termination provisions and indemnification obligations, including for liabilities under the Securities Act of 1933, as amended. The Offering is being made pursuant to the shelf registration statement on Form S-3 (File No. 333-275525) that was filed by the Company with the Securities and Exchange Commission (“SEC”) on November 13, 2023 and declared effective by the SEC on November 21, 2023, and a related prospectus supplement.
The Company estimates that the gross proceeds from the Offering will be approximately $110.0 million, before deducting underwriting discounts and commissions and estimated Offering expenses. Combined with the Company’s cash, cash equivalents and marketable securities as of January 1, 2026, the additional $110.0 million will provide for capital resources of approximately $251.4 million. The Company intends to use the net proceeds from the Offering, together with its existing cash, cash equivalents and marketable securities, primarily for general corporate purposes, which may include funding research, clinical and process development and manufacturing of its product candidates, increasing its working capital, acquisitions or investments in businesses, products or technologies that are complementary to the Company, capital expenditures and other general corporate purposes. Based on our planned use of the net proceeds from this offering, the Company estimates such funds will be sufficient to fund to the Company’s operating expenses and capital expenditures into the second quarter of 2028. The Company expects the Offering to close on February 11, 2026, subject to the satisfaction of customary closing conditions.
The Underwriting Agreement is filed as Exhibit 1.1 to this report and the foregoing description of the terms of the Underwriting Agreement is qualified in its entirety by reference to such exhibit, which is incorporated herein by reference. A copy of the opinion of Fenwick & West LLP, relating to the validity of the Shares in connection with the Offering, is filed with this Current Report on Form 8-K as Exhibit 5.1.
Item 7.01 Regulation FD Disclosure
On February 10, 2026, the Company will be disclosing an updated corporate presentation. A copy of the corporate presentation is attached as Exhibit 99.1 to this Current Report on Form 8-K. The corporate presentation will also be available on the Company’s website in the Investors section at https://www.sutrobio.com/corporate-presentation/.
The information in this Item 7.01 of this report, including Exhibit 99.1, shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (“Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any other filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such a filing.
Item 9.01. Financial Statements and Exhibits.
(d) Exhibits.
| Exhibit Number | Description | |
| 1.1 | Underwriting Agreement dated February 9, 2026 | |
| 5.1 | Opinion of Fenwick & West LLP | |
| 23.1 | Consent of Fenwick & West LLP (contained in Exhibit 5.1) | |
| 99.1 | Corporate Presentation | |
| 104 | Cover Page Interactive Data File (embedded within the Inline XBRL document) | |
Forward-Looking Statements
This Current Report on Form 8-K contains forward-looking statements within the meaning of the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995, and other federal securities laws. Any statements contained herein that do not describe historical facts, including, but not limited to, statements regarding the Company’s preliminary estimates of cash, cash equivalent and marketable securities as of January 1, 2026, the expected net proceeds of the Offering, the Company’s estimated cash runway following the Offering; the anticipated use of proceeds of the Offering, and the satisfaction of customary closing conditions related to the Offering, are forward-looking statements that involve risks and uncertainties that could cause actual results to differ materially from those discussed in such forward-looking statements. Such risks and uncertainties include, among others, the risks identified in the Company’s filings with the SEC, including its Quarterly Report on Form 10-Q for the fiscal period ended September 30, 2025, filed with the SEC on November 6, 2025, the prospectus supplement related to the Offering, and subsequent filings with the SEC. Any of these risks and uncertainties could materially and adversely affect the Company’s results of operations, which would, in turn, have a significant and adverse impact on the Company’s stock price. The Company cautions you not to place undue reliance on any forward-looking statements, which speak only as of the date they are made. The Company undertakes no obligation to update publicly any forward-looking statements to reflect new information, events or circumstances after the date they were made or to reflect the occurrence of unanticipated events.
SIGNATURES
Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.
| Sutro Biopharma, Inc. | ||||||
| Date: February 10, 2026 | By: | /s/ Greg Chow | ||||
| Greg Chow | ||||||
| Chief Financial Officer | ||||||
Exhibit 99.1 February 2026 NASDAQ: STRO
Forward-Looking Statements This presentation and the accompanying oral presentation contain “forward-looking” statements that are based on our management’s beliefs and assumptions and on information currently available to management. Forward-looking statements include all statements other than statements of historical fact contained in this presentation, including information concerning our future financial performance; business plans and objectives; anticipated preclinical and clinical development activities, including enrollment and site activation; timing of announcements of clinical results, trial initiation, and regulatory filings; outcome of regulatory decisions; and our expectations about our cash runway; potential benefits of our product candidates and platform; potential expansion into other indications and combinations, including the timing and development activities related to such expansion; potential growth opportunities, financing plans, potential future milestone and royalty payments, competitive position, industry environment and potential market opportunities for our product candidates. Forward-looking statements are subject to known and unknown risks, uncertainties, assumptions and other factors, including risks and uncertainties related to our cash forecasts, our and our collaborators’ ability to advance our product candidates, the receipt, feedback and timing of potential regulatory submissions, designations, approvals and commercialization of product candidates and the design, timing and results of preclinical and clinical trials and our ability to fund development activities and achieve development goals. It is not possible for our management to predict all risks, nor can we assess the impact of all factors on our business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements we may make. These factors, together with those that may be described in greater detail under the heading “Risk Factors” contained in our most recent Annual Report on Form 10-K, Quarterly Report on Form 10-Q and other reports the company files from time to time with the Securities and Exchange Commission, may cause our actual results, performance or achievements to differ materially and adversely from those anticipated or implied by our forward-looking statements. You should not rely upon forward-looking statements as predictions of future events. Although our management believes that the expectations reflected in our forward-looking statements are reasonable, we cannot guarantee that the future results, levels of activity, performance or events and circumstances described in the forward-looking statements will be achieved or occur. Moreover, neither we nor our management assume responsibility for the accuracy and completeness of the forward-looking statements. We undertake no obligation to publicly update any forward-looking statements for any reason after the date of this presentation to conform these statements to actual results or to changes in our expectations, except as required by law. This presentation also contains estimates and other statistical data made by independent parties and by us relating to market size and growth and other data about our industry. This data involves a number of assumptions and limitations, and you are cautioned not to give undue weight to such estimates. In addition, projections, assumptions, and estimates of our future performance and the future performance of the markets in which we operate are necessarily subject to a high degree of uncertainty and risk. NON-CONFIDENTIAL 2
Proprietary Platform Creates Best-in-Class ADCs At the forefront of next-gen ADCs, with improved antibody, linker, and payload for superior safety and efficacy Dual-payload ADCs, with partnered and Single-payload ADCs for complex targets where wholly-owned programs, to overcome competition is limited ADC resistance and delay progression Delivering the Three INDs in Three Years Next-Generation Multiple candidates advancing in parallel for large market opportunities of ADC 2H 2025 2026 2026 Therapeutics ✓ STRO-004: STRO-006: STRO-227: TF-Targeting ADC ITGB6-Targeting ADC PTK7-Targeting dpADC Well-Capitalized Runway into at least the second quarter of 2028 ITGB6 – Integrin-beta 6; IND – Investigational new drug; TF – Tissue factor NON-CONFIDENTIAL 3
Differentiated Pipeline of Single- and Dual-Payload ADCs SINGLE-PAYLOAD ADCs: DUAL-PAYLOAD ADCs: Focused on Complex Targets Overcome Resistance and Expressed Across Many Tumor Types Delay Progression STRO-227: STRO-004: STRO-006: PTK7-Targeting dpADC TF-Targeting ADC ITGB6-Targeting ADC Supercharged ADCs with best-in-class Best-in-class potential, designed for Best-in-class potential, designed for potential, combining different payloads to improved clinical benefit, stability, improved clinical benefit, stability, achieve improved clinical benefit, potency, and tumor selectivity potency, and tumor selectivity tolerability, and duration of response IND submission IND submission Ph 1 ongoing; 2026 Mid-2026 2026 expected expected initial data expected Well-tolerated at 50 mg/kg in NHPs Well-tolerated at 25 mg/kg in NHPs Well-tolerated at 25 mg/kg in NHPs dpADC – Dual-payload ADC; NHP – Non-human primate; IND – Investigational new drug; ITGB6 – Integrin-beta 6; PTK7 – Protein Tyrosine Kinase 7; TF – Tissue factor NON-CONFIDENTIAL 4
Next-Generation ADCs Enabled by Sutro’s Proprietary Platform
Designed to Deliver: Proprietary platform enables enhanced ADCs Precision Versatility Scalability Same cell-free system from Site-specific conjugation Increased flexibility on linker- discovery to commercial using non-natural amino acids payload number, placement, scale with consistent quality and click chemistry or combinations enables for uniform and stable industry-leading PK and molecules safety profile PK – Pharmacokinetics NON-CONFIDENTIAL 6
Sutro’s Platform Designed to Optimize Every Component of the ADC Expanding the therapeutic window to minimize toxicity and maximize efficacy 1 ANTIBODY ▸High throughput screening identifies Ab with ideal attributes 1 ▸Reduced ILD risk enabled by Fc-silent design PAYLOAD 2 ▸High DAR exatecans; stable PK ▸Multiple payload combinations with novel modalities 3 LINKER 3 2 ▸Stabilized β-glu linker with non-natural amino acids; optimized linker-payload number and placement ▸Tumor-selective cleavage reduces off-target toxicity OBJECTIVE Increasing ADC drug exposure leads to greater safety and efficacy Ab – Antibody; DAR – Drug to antibody ratio; ILD – Interstitial lung disease; PK – Pharmacokinetic NON-CONFIDENTIAL 7
Our Proprietary Platform Enables Industry-Leading ADC Exposure, a Key Driver of Safety and Efficacy Comparing ADC Exposure in NHPs at DAR16 ADCs Highest Non-Severely Toxic Dose 6,000 Total Ab (ng/mL) Site combo A Site combo B 100,000 5,000 Site combo C STRO-ADC DAR8 Site combo D STRO-ADC 10,000 4,000 DAR8 STRO-ADC DAR8 j 3,000 1,000 Enhertu DAR8 2,000 f 100 g 0 100 200 300 400 i d e h Time post-dose (hr) 1,000 a b c Choosing the right combination of sites can 0 result in optimized pharmacokinetics 0 0.5 1 1.5 2 Better Less ADC Less Systemic Exatecan/Topo1i ADCs PL Dose @ HNSTD [mg/kg] PK Toxicity Clearance Sutro ADC Therapeutics a. Dato-DXd (DAR4); b. AMT-562-T800 (DAR4); c. ETx-22 (DAR8); d. AMT-562-T1000 (DAR4); e. Ilfinitamab (DAR4); f. PL2201 (DAR6); g. DS-600 (DAR8); h. SKB264 (DAR8); i. DB-1310 (DAR8); j. MTX-13 (DAR8) Ab – Antibody; DAR – Drug to antibody ratio; MMAE – Monomethyl auristatin E; NHP – Non-human primate; ORR – Objective response rate; PK – Pharmacokinetic NON-CONFIDENTIAL 8 Conjugated PL Exposure [h ug/mL]
STRO-004 Potential Best-in-Class Exatecan ADC Targeting Tissue Factor
STRO-004: Potent TF-Targeting Exatecan ADC Engineered for Robust Exposure and Efficacy 50x preclinical exposure vs approved TF ADC 1 ANTIBODY 1 ▸Tumor targeting, does not interfere with TF biology ▸Fc-silent to reduce ILD risk 2 PAYLOAD ▸DAR 8; safely boosts potency ▸Drives efficacy in low-copy targets 3 3 LINKER 2 ▸β-glu linker with site-specific conjugation for stability and tumor-selective cleavage UPCOMING MILESTONES Phase 1 trial in a range of solid tumors, with initial data expected mid-2026 DAR – Drug to antibody ratio; ILD – Interstitial lung disease; IND – Investigational new drug; TF – Tissue factor NON-CONFIDENTIAL 10
Significant Unmet Need Across Large Oncology Patient Populations Incidence (U.S.) and relapsed/refractory ORR and OS benchmarks across select relevant tumor types Incidence (U.S.) and Relapsed/Refractory ORR and Current Standard of Care in R/R OS Benchmarks Across Select Relevant Tumor Types % ORR mOS 1 1 Cervical 15,000 18% 11-12 months 2 2 Pancreatic 65,000 8% ~6 months 3-5 3-5 HNSCC* 75,000 6-32% 5-8 months 6-8 6-8 CRC 150,000 6-40% 11-16 months 9-11 9-11 200,000 Lung 13-44% 10-12 months CRC – Colorectal cancer; HNSCC – Head and neck squamous cell carcinoma; ORR – Overall response rate; OS – Overall survival; TF – Tissue factor. *Includes ~60K oral cavity and pharynx plus ~15K larynx. Sources: 1. Vergote et al. 2024; 2. Wang-Gillam 2019; 3. Vermorken 2010; 4. Ferris et al. 2017; 5. Soulieres et al. 2022; 6. Prager et al., 2023; 7. Peeters et al., 2015; 8. Sobrero et al., 2020; 9. Paz-Ares et al. 2024; 10. Ahn et al. 2024; 11. Sands et al. 2025. NON-CONFIDENTIAL 11
STRO-004: Favorable In Vitro Tolerability Profile vs. Approved TF ADC Eye Inflammation Skin Toxicities STRO-004 Human Corneal Epithelial Cells Human Keratinocytes Reduced Bleeding Risk 50% 46% 40% 30% 20% 10% 1% 0% STRO-004 Tisotumab Up to 70% of Tivdak-treated STRO-004 (DAR8-exatecan) Approved TF ADC (DAR4-MMAE) patients have treatment-emergent bleeding adverse events Inhibition of coagulation, expressed as % inhibition DAR – Drug to antibody ratio; MMAE – Monomethyl auristatin E; TF – Tissue factor of Factor X (FX) conversion in an in vitro assay NON-CONFIDENTIAL 12
STRO-004: Promising Anti-Tumor Activity in Multiple TF-Expressing Cancer Models STRO-004 % Best Response in PDX Models of Solid Tumors 100 DCR: 28/30 ORR: 22/30 DCR: 28/30 (93%) STRO-004 ORR: 22/30 (73%) ORR CR PR SD 50 Cancer N (%) 11 11 4 HNSCC 17 0 0 (65) (65) (24) 5 3 2 2 NSCLC 7 (71) (43) (29) (29) -50 5 1 4 PDAC 5 0 (100) (20) (25) 1 1 CRC 1 0 0 (100) (100) -100 STRO-004 5 mg/kg HNSCC NSCLC Pancreatic cancer CRC *Interim Best Overall Response (BOR), model ongoing CR – Complete response; CRC – Colorectal cancer; DCR – Disease control rate; HNSCC – Head and neck squamous cell carcinoma; NSCLC – Non-small cell lung cancer; ORR – Overall response rate; PDX – Patient-derived xenograft; PR – Partial response; SD – stable disease; TF – Tissue Factor NON-CONFIDENTIAL 13 % tumor volume change from baseline
Detailed Monotherapy Development Strategy: Phase 1 Trial Ongoing Dose level 2 cleared; cohort 3 dosed as of February 2026 Initial data expected in mid-2026 Move Forward with Dose Escalation Tumor type eligibility Recommended Dose(s) Advanced Solid Tumors with Tissue Factor Expression Selected for TF expression: • Early detection of activity HNSCC • Early characterisation of safety profile NSCLC Dose Level 5 • Early transition to registrational development path Colorectal PDAC Dose Level 4 Recommended Bladder Cervical Dose Level 3 Dose 2 Endometrial Dose Level 2 Recommended • Better for patients HNSTD of 50 mg/kg permits high entry into dose Dose 1 escalation ladder • Early signs of activity Dose Level 1 - Shortens time to observing activity • Relevant to look at safety in - Increases probability of wide therapeutic window potential-forward indications – facilitates dose optimization HNSCC – Head and neck squamous cell carcinoma; HNSTD – Highest non-severely toxic dose; NSCLC – Non-small cell lung cancer; PDAC - Pancreatic ductal adenocarcinoma; TF – Tissue factor NON-CONFIDENTIAL 14
STRO-006 Potential Best-in-Class Exatecan ADC Targeting Integrin-Beta 6
STRO-006: Selective ITGB6-Targeting Exatecan ADC for Leading Tolerability and PK STRO-006 is designed for superior selectivity, safety and stability 1 ANTIBODY 1 ▸High affinity to ITGB6 without effect on TGFβ signaling ▸Fc-silent to reduce ILD risk 2 PAYLOAD ▸ High stable DAR (8) ▸ Potent anti-tumor activity with bystander effect 3 3 LINKER 2 ▸β-glu linker with robust in vivo stability to minimize premature release and enhance PK and tolerability UPCOMING MILESTONES IND filing planned for 2026 DAR – Drug to antibody ratio; ILD – Interstitial lung disease; IND – Investigational new drug; ITGB6 – Integrin-beta 6; PK – Pharmacokinetic; TGFβ – Transforming growth factor-beta NON-CONFIDENTIAL 16
ITGB6 Expression has Unique Promise in NSCLC as well as Other Common Solid Tumors STRO-006 is designed for monotherapy and combination use, expanding its therapeutic reach Incidence (U.S.) Across Select Relevant Tumor Types 40,000 75,000 150,000 200,000 TNBC HNSCC CRC Lung ITGβ6 expression assumptions are based on a weighted average of expression as reported in publicly available literature and triangulated with internal Sutro data on file. Criteria for positivity differs across studies, overall positive staining/overexpression % is used CRC – Colorectal cancer; HNSCC – Head and neck squamous cell carcinoma; ITGB6 – Integrin beta 6; NSCLC – Non-small cell lung cancer; TNBC – Triple-negative breast cancer NON-CONFIDENTIAL 17
STRO-006 Has Shown Superior Activity to Competitor ADCs in Preclinical Models Expressing ITGB6 adeno NSCLC PDX (CTG-0743) Non-squamous NSCLC PDX, mut-EGFR Squamous NSCLC PDX, WT-EGFR Bladder CDX, SW780 H score: 136 (Seagen) SW780 (UCC) 1500 2500 2000 ITGB6-moderate 2000 1500 1000 1500 1000 1000 500 500 500 0 0 0 0 10 20 30 0 10 20 30 40 50 0 10 20 30 Days post dose initiation Days post dose Days post dose initiation Vehicle Vehicle Vehicle aITGB6 ADC (DAR4 MMAE), 3 mg/kg aITGB6 ADC (DAR4 MMAE), 3 mg/kg aITGB6 ADC (DAR8 AMDCPT), 1 mg/kg STRO-006, 1 mg/kg STRO-006, 3 mg/kg STRO-006, 3 mg/kg STRO-006, 10 mg/kg STRO-006, 10 mg/kg CDX – Cell-line derived xenograft; DAR – Drug to antibody ratio; ITGB6 – Integrin beta-6; MMAE – Monomethyl Auristatin E (tubulin inhibitor); NSCLC – Non-small cell lung cancer; PDX – Patient-derived xenograft NON-CONFIDENTIAL 18 3 Tumor volume (mm ) 3 Tumor volume (mm ) Relative Tumor Volume (%)
Superior Anti-Tumor Activity and Greater Duration of Response Following a Single Dose of STRO-006 in HNSCC PDX Models 200 % Best Response PDX Models of HNSCC 150 100 200 50 % Best Response in PDX Models of HNSCC 0 STRO-006 aITGB6 DAR4 MMAE ADC 150 20 40 60 DCR: 14/17 DCR: 11/17 -50 ORR: 12/17 * ORR: 8/17 Days 100 -100 *interim BOR, model ongoing 50 200 19 150 0 100 * * * * -50 * * * 50 * * * 0 -100 20 40 60 *: interim readout, model ongoing STRO-006 5 mg/kg aITGB6 ADC (DAR4 MMAa ElTGB6 ) 5 mg/kg ADC (DAR4 MMAE) 5 mg/kg -50 Days STRO-006 5 mg/kg -100 Response (below baseline) STRO-006 aITGB6 ADC, DAR4 MMAE ADC at end of study Cancer n ORR CR PR SD ORR CR PR SD STRO-006 7/11 (64%) HNSCC, n 12 12 2 8 8 3 17 0 0 aITGB6 DAR4 MMAE 3/11 (27%) (%) (71) (71) (12) (47) (47) (18) BOR – Best overall response; DAR – Drug to antibody ratio; DCR – Disease control rate; HNSCC – Head and neck squamous cell carcinoma; ITGB6 – Integrin beta 6; ORR – Overall response rate; PDX – Patient-derived xenograft NON-CONFIDENTIAL 19 % tumor volume change from baseline aITGB6 ADC Landmark STRO-006 5 (DAR4. MMAE) 5 Response mg/kg mg/kg Change from Baseline (%) Change from Baseline (%)
Delivering Dual-Payloads: The Next Revolution in ADCs
Dual-Payload ADCs: Targeted Combination Therapy to Improve Outcomes Combination treatment approaches have been shown to improve outcomes in oncology vs single agent chemotherapy and remain standard of care in many therapeutic areas Dual-Payload ADCs: Potential to Become Future Standard of Care • Overcomes resistance resulting from conventional ADCs • Reduces toxicity over ADC combination approaches • Unique benefits from simultaneous delivery of payloads within the tumor cells • Simplified development path compared to combination treatment regimens • Unlocks broader market potential across tumor types NON-CONFIDENTIAL 21
Proprietary Cell-Free Platform Positions Sutro at the Forefront of Dual-Payload Innovation Topo1 x Tubulin Enables novel drug combinations and tuning of ratios with Multiple the broadest payload diversity to overcome tumor resistance Topo1 x DDRi Modalities and improve tolerability Topo1 x IO Tailored Ratios DAR 4+4 DAR 4+2 DAR 8+4 DAR 8+2 Safety Well-tolerated in non-human primates at 25 mg/kg (2XQ3W) with dual cytotoxin ADC DAR – Drug to antibody ratio; DDRi – DNA damage response inhibitors; IO – Immuno-oncology NON-CONFIDENTIAL 22
Sutro’s First Wholly-Owned Dual-Payload ADC Targeting PTK7 A clinically validated, pan-tumor target enriched on tumor-initiating cells • Broad expression across high-need indications and Breast Cancer Xenograft Model associated with poor prognosis • Anti-tumor clinical activity of an anti-PTK7 ADC has been demonstrated across multiple tumor types • First-generation anti-PTK7 ADC was constrained by dose-limiting safety, underscoring need for next- generation ADC with greater specificity and a wider therapeutic index UPCOMING MILESTONES IND filing anticipated in 2026 *1: https://pmc.ncbi.nlm.nih.gov/articles/PMC9401513/ 2: *for Ovarian (Pt-resistant)/TNBC/NSCLC 3: The most common, treatment-related adverse events for PF-06647020 administered every 3 weeks were nausea, alopecia, fatigue, headache, neutropenia, and vomiting (45%–25%); 25% of patients had grade ≥ 3 neutropenia. Two patients experienced dose-limiting toxicities (grade 3 headache and fatigue) at the highest every 3 weeks dose evaluated. NON-CONFIDENTIAL 23
Sutro Dual-Payload ADC: Preclinical Tolerability Meets Single- Payload Benchmarks Even with Added MMAE Payload Area Target Linker Payload DAR NHP HNSTD Highest Clinical Phase a Enhertu HER-2 GGFG Deruxtecan 8 30 mg/kg (Q3Wx3) Approved b Datroway Trop-2 GGFG Deruxtecan 4 10 mg/kg (Q3Wx5) Approved c MK-1022 HER-3 GGFG Deruxtecan 8 30 mg/kg (Q3Wx5) 3 d 30 mg/kg MK-2400 B7-H3 GGFG Deruxtecan 4 3 (Q2Wx3) e 30 mg/kg MK-5909 CDH6 GGFG Deruxtecan 8 2/3 (Q3Wx3) f 30 mg/kg Rina-S FOLR1 Val-Cit Exatecan 8 3 (Q3Wx2) 25 mg/kg Sutro dpADC PTK7β-Glu Exatecan + MMAE 8 + 2 Preclinical (Q3Wx2) a b c d e f PMID: 27026201 PMID: 34413126 PMID: 31471314 PMID: 35149548 PMID: 38205802 DOI:10.1158/1538-7445.AM2023-CT244 NON-CONFIDENTIAL 24
Dual-Payload ADCs Have Overcome Resistance and Driven Tumor Regression in Preclinical Models Dual-Payload ADC Induces Tumor Dual-Payload ADCs Have Improved In Vivo Regression After Sequential ADC Resistance Efficacy in an MTI-Resistant CRC Xenograft Model HCT-116 Tumor Growth Curves 10 mg/kg Enhertu 10 mg/kg STRO-002 10 mg/kg SP12576 CRC Xenograft Tumor Growth Curve 1500 1000 500 0 0 10 20 30 40 Days Post Dose Vehicle control Mice with Enhertu-resistant tumors were switched onto STRO-002 treatment Trastuzumab DAR4 MTI (MMAE) ADC (5 mg/kg) Trastuzumab DAR8 Topo1i ADC (5 mg/kg) and subsequently onto dual-payload ADC after exhibiting STRO-002 resistance Trastuzumab DAR8 Topo1i + DAR4 MTI (MMAE) dpADC (5 mg/kg) CRC – Colorectal cancer; DAR – Drug to antibody ratio; MMAE – Monomethyl auristatin E; MTI – Microtubule inhibitor NON-CONFIDENTIAL 25 Relative Tumor Volume (%)
iADC: Dual-Payload ADC Combining Tumor-Targeted Delivery of a Cytotoxin and Immune Stimulator Strategic partnership with Astellas to deliver new treatment options for cold tumors and patients unresponsive to existing cancer immunotherapies Combining a cytotoxin and immune modulator gives potential to: ▸Act alone by stimulating the immune system and priming new populations of immune cells ▸Synergize with other immune therapies that remove inhibitory signals on the immune system (e.g. checkpoint inhibitors) ▸Address hard-to-treat cancers by activating a robust anti-tumor immune response PARTNERSHIP UPDATE First program expected to enter the clinic in early 2026 iADC -- Immunostimulatory ADC; IND – Investigational new drug NON-CONFIDENTIAL 26
Pipeline of Next-Generation Single- and Dual-Payload ADCs PHASE 3/ PROGRAM MODALITY/TARGET INDICATION DISCOVERY PRECLINICAL PHASE 1/1B PHASE 2 REGISTRATIONAL MILESTONES Initial Phase 1 data STRO-004 Tissue Factor ADC Solid Tumors expected mid-2026 IND submission STRO-006 Integrin αvβ6 Solid Tumors expected 2026 PTK7 Dual-Payload IND submission STRO-227 Solid Tumors expected 2026 ADC STRO-00Y Dual-Payload ADC Solid Tumors Invasive VAX-24 24-Valent Pneumococcal Conjugate Vaccine Disease Invasive VAX-31 31-Valent Pneumococcal Conjugate Vaccine Disease st Undisclosed 1 program expected Immunostimulatory Programs Cancers to enter clinic in ADCs (iADCs) early 2026 NON-CONFIDENTIAL 27 PARTNERED PROGRAMS WHOLLY-OWNED PROGRAMS