STRO

– Encouraging early clinical activity including confirmed and ongoing unconfirmed partial responses with favorable tolerability, and pharmacokinetics (PK) observed in ongoing STRO-004 Phase 1 study – – Strong execution of STRO-004 STRIVE-01 study with rapid enrollment of initial dose escalation cohorts within 7 months; dose optimization ongoing between 4-5 mg/kg – –   STRO-006, next-generation integrin 6 (ITGB6)-targeting ADC, is on track to enter the clinic in the third quarter of 2026 – – Second dual-payload iADC program from Sutro’s platform under Astellas collaboration expected to enter the clinic in the second half of 2026 – – Strong balance sheet with $164.3 million in cash, cash equivalents and marketable securities as of June 30, 2026, expected to support operations into at least the second quarter of 2028 – SOUTH SAN FRANCISCO, Calif., Aug. 12, 2026 (GLOBE NEWSWIRE) -- Sutro Biopharma, Inc. (Sutro or the Company) (NASDAQ: STRO), a clinical-stage oncology company pioneering site-specific and novel-format antibody drug conjugates (ADCs), today reported its financial results for the second quarter ended June 30, 2026 and recent business highlights. Sutro also provided data showing a favorable tolerability profile and early signals of clinical activity from its ongoing Phase 1 study of STRO-004, the Company’s potential best-in-class Tissue Factor (TF)-targeting DAR8 exatecan ADC, in heavily pretreated patients with advanced solid tumors. “During the second quarter, we continued to execute swiftly across our next-generation ADC portfolio, highlighted by encouraging early clinical data from our ongoing Phase 1 study of STRO-004, having rapidly enrolled our initial dose escalation cohorts in just seven months and now optimizing our go-forward dose,” said Jane Chung, Sutro’s Chief Executive Officer. “We have observed early clinical responses alongside favorable safety, tolerability, and a differentiated pharmacokinetic (PK) profile in patients with few remaining treatment options. The favorable tolerability profile and wider therapeutic index of our DAR8 exatecan ADC allows us to dose higher than other TF-targeting ADCs. These findings strengthen our confidence in STRO-004’s potential to deliver meaningful clinical benefit and provide the opportunity to safely combine with other therapies, while further validating our proprietary ADC platform.” “Additionally, we are excited to enter the clinic with STRO-006 in the near future, our second clinical program in less than a year, reflecting the continued acceleration of our pipeline strategy. We also look forward to advancing STRO-227, our first wholly-owned dual-payload ADC, toward IND submission later this year, joining our partner Astellas’ dual-payload iADC programs in the clinic. Our progress this quarter underscores the continued advancement of our portfolio and our commitment to delivering differentiated therapies for patients while creating long-term value for shareholders.” Wholly-Owned Pipeline STRO-004 Early Safety and Signals of Clinical Activity Highlights: Dose escalation continues with strong execution, with dose levels 1–5 mg/kg (n=49) enrolled faster than expected. The study, called STRIVE-01, is currently optimizing between doses of 4 and 5 mg/kg, and the maximum tolerated dose has not yet been defined. This US-only based trial, which began in November 2025, includes heavily pretreated patients (median of 3 prior lines of therapy [range 1–7]) across eight tumor types unselected for TF expression. In pancreatic and colorectal cancer patients, 100% of patients received one or more prior irinotecan-containing regimens, which has been associated with reduced activity of topoisomerase 1 inhibitor payloads. Key observations as of the data cutoff date of July 24, 2026 include: Multiple responses, including confirmed and ongoing unconfirmed partial responses, across three tumor types in RECIST-evaluable patients to date; including pancreatic cancer, head and neck cancer, and non-small cell lung cancer at dose levels 3-4 mg/kg Favorable tolerability profile, with mostly low-grade adverse events (AEs) observed Overall discontinuation rate due to AEs was low at 6%. Predictable PK in patients, consistent with preclinical data, demonstrating dose-proportional ADC exposures at all doses, with no evidence of Target Mediated Drug Disposition “We are encouraged by the emerging STRO-004 clinical PK profile, which demonstrate the stability of our ADC construct and validate the design principles of our platform,” said Hans-Peter Gerber, Ph.D., Sutro’s Chief Scientific Officer. “Compared with conventional DAR8 exatecan ADCs, STRO-004 delivered 25-50% more ADC exposure with at least 50% less circulating payload concentration, allowing us to dose at the highest end of the dosing range for the class. We observed comparable PK with STRO-006 (Topo1i) and our dual payload ADC STRO-227 (Topo1i x MMAE) in preclinical experiments, which gives us confidence in the potential of our advanced design capabilities to widen the therapeutic index across our ADC pipeline.” The next STRIVE-01 study update is targeted for the first half of 2027. Initiation of expansion cohorts is planned for the first half of 2027. STRO-006: Sutro’s next-generation, highly selective integrin β6 (ITGB6)-targeting ADC with a DAR8 exatecan payload, is designed for the treatment of multiple solid tumors. The Company expects to initiate a Phase 1 clinical trial in the third quarter of 2026. STRO-227: Sutro’s wholly-owned DAR10 dual-payload ADC targeting PTK7, consisting of MMAE (DAR2) and exatecan (DAR8) payloads to enable complementary mechanisms of action within a single molecule. The program remains on track for IND submission in 2026 and represents a key component of Sutro’s strategy to expand its pipeline of novel-format dual-payload ADCs. Next-Generation ADC Collaborations Astellas: Two research and development programs are progressing under Sutro’s collaboration with Astellas focused on dual-payload immunostimulatory ADCs (iADCs). The first program, which targets TROP2, continues to actively dose patients, resulting in a $10 million milestone payment received by Sutro in April 2026. The second program continues to progress under the collaboration, and based on current development timelines, Sutro expects Astellas to enter the clinic by the end of 2026. Investor Conferences Management will participate in the following upcoming healthcare investor conferences. When available, the webcasts of the presentations will be accessible through the News & Events page of the Investor Relations section of the Company’s website at www.sutrobio.com. Archived replays will be available for at least 30 days after the event. Wells Fargo 21st Annual Healthcare Conference (Boston, MA • September 8–10) Cantor Global Healthcare Conference (New York, NY • September 9–11) H.C. Wainwright 28th Annual Global Investment Conference (New York, NY • September 14–16) Second Quarter 2026 Financial Highlights Cash, Cash Equivalents and Marketable Securities As of June 30, 2026, Sutro had cash, cash equivalents and marketable securities of $164.3 million, as compared to $202.6 million as of March 31, 2026. Revenue Revenue was $9.8 million for the quarter ended June 30, 2026, as compared to $63.7 million for the quarter ended June 30, 2025, with the 2026 amount related principally to the Astellas collaboration. Research & Development (R&D) and General & Administrative (G&A) Expenses Total R&D and G&A expenses for the quarter ended June 30, 2026 were $39.5 million, as compared to $48.7 million for the quarter ended June 30, 2025. About Sutro Biopharma Sutro Biopharma, Inc. is a clinical-stage biotechnology company advancing a next-generation antibody-drug conjugate (ADC) platform designed to deliver single- and dual-payload ADCs that enable meaningful breakthroughs for patients with cancer. By fully optimizing the antibody, linker, and payload, Sutro’s cell-free platform produces ADCs that are engineered to improve drug exposure, reduce side effects, and expand the range of treatable tumor types. With unique capabilities in dual-payload ADCs, Sutro aims to overcome treatment resistance and redefine what’s possible in cancer therapy. The Company’s pipeline of single- and dual-payload ADCs targets large oncology markets with limited treatment options and significant need for improved therapies. For more information, follow Sutro on social media @Sutrobio or visit www.sutrobio.com. Forward-Looking Statements This press release contains forward-looking statements within the meaning of the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995, including, but not limited to, anticipated preclinical and clinical development activities; timing of announcements of IND submissions, trial initiation, clinical results, and other regulatory filings; outcome of discussions with regulatory authorities; potential benefits, efficacy and safety profile of the Company’s product candidates and platform; potential business development and partnering transactions; potential market opportunities for the Company’s product candidates; the positing of the Company’s product candidates in the competitive landscape; the timing and receipt of anticipated future milestone and royalty payments; and the Company’s expected cash runway. All statements other than statements of historical fact are statements that could be deemed forward-looking statements. Although the Company believes that the expectations reflected in such forward-looking statements are reasonable, the Company cannot guarantee future events, results, actions, levels of activity, performance or achievements, and the timing and results of biotechnology development and potential regulatory approval is inherently uncertain. Forward-looking statements are subject to risks and uncertainties that may cause the Company’s actual activities or results to differ significantly from those expressed in any forward-looking statement, including risks and uncertainties related to the Company’s ability to advance its product candidates, the receipt and timing of potential regulatory designations, approvals and commercialization of product candidates, the market size for the Company’s product candidates to be smaller than anticipated, clinical trial sites, supply chain and manufacturing facilities, the Company’s ability to obtain, maintain and recognize the benefits of certain designations received by product candidates, the timing and results of preclinical and clinical trials, the Company’s ability to fund development activities and achieve development goals, the Company’s ability to protect intellectual property, the Company’s commercial collaborations with third parties, the impact of health pandemics, tariffs, regional geopolitical conflicts, changes in interest rates, inflation, potential uncertainty with respect to the debt ceiling and government shutdowns, and other risks and uncertainties described under the heading “Risk Factors” in documents the Company files from time to time with the Securities and Exchange Commission. These forward-looking statements speak only as of the date of this press release, and the Company undertakes no obligation to revise or update any forward-looking statements to reflect events or circumstances after the date hereof. Investor ContactEmily WhiteSutro Biopharma(650) [email protected] Media ContactAmy BonannoLyra Strategic [email protected] (1) The condensed balance sheet as of June 30, 2026 was derived from the unaudited financial statements included in the Company's Quarterly Report on Form 10-Q for the quarter ended June 30, 2026, filed with the Securities and Exchange Commission on August 12, 2026. (2) The condensed balance sheet as of December 31, 2025 was derived from the audited financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2025, filed with the Securities and Exchange Commission on March 23, 2026.

Sutro Biopharma, Inc. (NASDAQ:STRO) just released its latest first-quarter results and things are looking bullish. Results clearly exceeded expectations, with a substantial revenue beat leading to smaller losses in what looks like a definite win for investors. Revenues were US$15m and the statutory loss per share was US$2.94, smaller than the analysts had forecast. Following the result, the analysts have updated their earnings model, and it would be good to know whether they think there's been a strong change in the company's prospects, or if it's business as usual. With this in mind, we've gathered the latest statutory forecasts to see what the analysts are expecting for next year. AI is about to change healthcare. These 20 stocks are working on everything from early diagnostics to drug discovery. The best part - they are all under $10bn in marketcap - there is still time to get in early. Following the recent earnings report, the consensus from eleven analysts covering Sutro Biopharma is for revenues of US$41.4m in 2026. This implies a concerning 58% decline in revenue compared to the last 12 months. Losses are expected to hold steady at around US$9.12. Yet prior to the latest earnings, the analysts had been forecasting revenues of US$32.4m and losses of US$8.14 per share in 2026. Ergo, there's been a clear change in sentiment, with the analysts lifting this year's revenue estimates, while at the same time increasing their loss per share numbers to reflect the cost of achieving this growth. View our latest analysis for Sutro Biopharma It will come as a surprise to learn that the consensus price target rose 32% to US$47.10, with the analysts clearly more interested in growing revenue, even as losses intensify. Fixating on a single price target can be unwise though, since the consensus target is effectively the average of analyst price targets. As a result, some investors like to look at the range of estimates to see if there are any diverging opinions on the company's valuation. Currently, the most bullish analyst values Sutro Biopharma at US$61.00 per share, while the most bearish prices it at US$9.00. So we wouldn't be assigning too much credibility to analyst price targets in this case, because there are clearly some widely different views on what kind of performance this business can generate. With this in mind, we wouldn't rely too heavily the consensus price target, as it is just an average and analysts clearly have some deeply divergent views on the business. Taking a look at the bigger picture now, one of the ways we can understand these forecasts is to see how they compare to both past performance and industry growth estimates. We would highlight that revenue is expected to reverse, with a forecast 69% annualised decline to the end of 2026. That is a notable change from historical growth of 15% over the last five years. Compare this with our data, which suggests that other companies in the same industry are, in aggregate, expected to see their revenue grow 22% per year. So although its revenues are forecast to shrink, this cloud does not come with a silver lining - Sutro Biopharma is expected to lag the wider industry. The most important thing to note is the forecast of increased losses next year, suggesting all may not be well at Sutro Biopharma. Fortunately, they also upgraded their revenue estimates, although our data indicates it is expected to perform worse than the wider industry. There was also a nice increase in the price target, with the analysts clearly feeling that the intrinsic value of the business is improving. Keeping that in mind, we still think that the longer term trajectory of the business is much more important for investors to consider. At Simply Wall St, we have a full range of analyst estimates for Sutro Biopharma going out to 2028, and you can see them free on our platform here.. You still need to take note of risks, for example - Sutro Biopharma has 4 warning signs (and 3 which are potentially serious) we think you should know about. Have feedback on this article? Concerned about the content? Get in touch with us directly. Alternatively, email editorial-team (at) simplywallst.com.This article by Simply Wall St is general in nature. We provide commentary based on historical data and analyst forecasts only using an unbiased methodology and our articles are not intended to be financial advice. It does not constitute a recommendation to buy or sell any stock, and does not take account of your objectives, or your financial situation. We aim to bring you long-term focused analysis driven by fundamental data. Note that our analysis may not factor in the latest price-sensitive company announcements or qualitative material. Simply Wall St has no position in any stocks mentioned.

– On track to report initial safety, PK and early activity from Phase 1 dose-escalation trial of STRO-004, potential best-in-class Tissue Factor ADC, in mid-2026 – – Continued advancement of wholly-owned pipeline, including ITGB6 ADC STRO-006 and dual-payload PTK7 program STRO-227, with IND submissions planned in 2026 – – First dual-payload iADC from Sutro’s platform entered the clinic under Astellas collaboration; patient dosing underway – – Strong balance sheet with $202.6 million in cash, cash equivalents and marketable securities as of March 31, 2026; including gross proceeds from the recent capital raise, supporting operations into at least the second quarter of 2028 – SOUTH SAN FRANCISCO, Calif., May 14, 2026 (GLOBE NEWSWIRE) -- Sutro Biopharma, Inc. (Sutro or the Company) (NASDAQ: STRO), a clinical-stage oncology company pioneering site-specific and novel-format antibody drug conjugates (ADCs), today reported its financial results for the first quarter of 2026 and recent business highlights. “During the first quarter, we continued to execute across our clinical and preclinical portfolio, positioning Sutro for key data readouts later this year,” said Jane Chung, Sutro’s Chief Executive Officer. “Dose escalation is rapidly progressing in our Phase 1 trial of STRO-004, and we remain on track to report initial safety, pharmacokinetic and early activity data in mid-2026, which we believe will provide important insights into its clinical profile and our platform as a whole. This clinical momentum is reinforced by preclinical data we presented at the recent AACR Annual Meeting, which highlighted the robust and consistent antitumor activity of STRO-004, as well as continued progress across our broader ADC pipeline.” “In parallel, we are advancing our next-generation ADC candidates, STRO-006, targeting ITGB6, and STRO-227, our first wholly-owned dual-payload ADC targeting PTK7, as we work toward IND submissions this year. We are also pleased to see our first partnered dual-payload iADC with Astellas entering the clinic, marking an important validation of our platform’s ability to generate differentiated multi-payload ADCs. With a strengthened balance sheet and continued disciplined execution, we believe we are well positioned to deliver meaningful progress across our programs in 2026.” Wholly-Owned Pipeline STRO-004: Sutro continues to advance its ongoing first-in-human Phase 1 dose-escalation trial of STRO-004, a Tissue Factor (TF)-targeting ADC with a DAR8 Topo1 payload, in patients with advanced solid tumors. The Company expects to report initial clinical data in mid-2026, including safety and tolerability, pharmacokinetic exposure, and early activity data. In preclinical studies, STRO-004 demonstrated a favorable safety profile, including a highest non-severely toxic dose (HNSTD) of 50 mg/kg in non-human primates, supporting the clinical starting dose of 1 mg/kg. STRO-006: Sutro’s next-generation, highly selective integrin β6 (ITGB6)-targeting ADC with a DAR8 Topo1 payload, designed for the treatment of multiple solid tumors. The program continues to advance toward clinical development, with an IND submission anticipated in 2026. STRO-227: Sutro’s wholly-owned DAR10 dual-payload ADC targeting PTK7, combining MMAE (DAR2) and a Topo1 payload (DAR8) to enable complementary mechanisms of action within a single molecule. The program remains on track for IND submission in 2026 and represents a key component of Sutro’s strategy to expand its pipeline of novel-format dual-payload ADCs. Next-Generation ADC Collaborations Astellas: Two research and development programs are progressing under Sutro’s collaboration with Astellas focused on dual-payload immunostimulatory ADCs (iADCs). The first program, targeting TROP2, has entered the clinic and is actively dosing patients, resulting in a $10 million milestone payment received by Sutro in April 2026. The second program continues to progress in an IND-enabling toxicology study. Medical Conferences American Association for Cancer Research (AACR), April 17-22, 2026, San Diego, California Sutro presented new preclinical data at AACR from across its pipeline of ADC discovery programs, including an oral presentation on STRO-004. Among the highlights, STRO-004 demonstrated robust and consistent antitumor activity across multiple TF-expressing solid tumor PDX models, with improved anti-tumor activity versus benchmark ADCs. Additionally, STRO-006 and STRO-227 showed meaningful, dose-dependent antitumor activity across solid tumor models. More details can be found in the press release here. In addition to these presentations, Sutro’s strategic partner, Astellas Pharma, also reviewed preclinical results from its TROP2-targeted iADC program, ASP2998, at AACR. The oral presentation, titled “ASP2998, a TROP2-targeted immunostimulatory antibody-drug conjugate (iADC) with dual payloads, demonstrates potent efficacy and a favorable safety profile in nonclinical models,” highlighted the progress in development of next-generation iADCs leveraging Sutro’s cell-free protein synthesis platform. ASP2998 is a first-in-class iADC that combines cytotoxic and immune-stimulatory mechanisms to enhance antitumor efficacy. Inclusion of a STING agonist augments the antitumor efficacy, immune activation and durable tumor immunity of ASP2998, supporting its superior activity over toxin-only anti-TROP2 ADCs. Preclinically, ASP2998 demonstrated a favorable safety profile, supporting a promising therapeutic index. Investor Conferences Management will participate in the following upcoming healthcare investor conferences. When available, the webcasts of the presentations will be accessible through the News & Events page of the Investor Relations section of the Company’s website at www.sutrobio.com. Archived replays will be available for at least 30 days after the event. H.C. Wainwright 4th Annual BioConnect Investor Conference (New York, NY • May 19) TD Cowen 7th Annual Oncology Innovation Summit (Virtual • May 26 – 27) Jefferies Global Healthcare Conference (New York, NY • June 2-4) Corporate Updates Sutro strengthened its cash position with an underwritten offering of 7,868,383 shares of its common stock at a price of $13.98 per share, resulting in gross proceeds of $110.0 million, before deducting underwriting discounts and commissions and other offering expenses. The Company’s cash runway is now expected into at least the second quarter of 2028, excluding additional anticipated milestones from our existing collaborations. The luvelta program has been closed and there will be no additional investment in the program. Sutro is not currently pursuing further business development opportunities for the program. First Quarter 2026 Financial Highlights Cash, Cash Equivalents and Marketable Securities As of March 31, 2026, Sutro had cash, cash equivalents and marketable securities of $202.6 million, as compared to $141.4 million as of December 31, 2025. Revenue Revenue was $14.5 million for the quarter ended March 31, 2026, as compared to $17.4 million for the quarter ended March 31, 2025, with the 2026 amount related principally to the Astellas collaboration. Research & Development (R&D) and General & Administrative (G&A) Expenses Total R&D and G&A expenses for the quarter ended March 31, 2026 were $44.1 million, as compared to $64.9 million for the quarter ended March 31, 2025. About Sutro Biopharma Sutro Biopharma, Inc. is a clinical-stage biotechnology company advancing a next-generation antibody-drug conjugate (ADC) platform designed to deliver single- and dual-payload ADCs that enable meaningful breakthroughs for patients with cancer. By fully optimizing the antibody, linker, and payload, Sutro’s cell-free platform produces ADCs that are engineered to improve drug exposure, reduce side effects, and expand the range of treatable tumor types. With unique capabilities in dual-payload ADCs, Sutro aims to overcome treatment resistance and redefine what’s possible in cancer therapy. The Company’s pipeline of single- and dual-payload ADCs targets large oncology markets with limited treatment options and significant need for improved therapies. For more information, follow Sutro on social media @Sutrobio or visit www.sutrobio.com. Forward-Looking Statements This press release contains forward-looking statements within the meaning of the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995, including, but not limited to, anticipated preclinical and clinical development activities; timing of announcements of IND submissions, trial initiation, clinical results, and other regulatory filings; outcome of discussions with regulatory authorities; potential benefits, efficacy and safety profile of the Company’s product candidates and platform; potential business development and partnering transactions; potential market opportunities for the Company’s product candidates; the timing and receipt of anticipated future milestone and royalty payments; the Company’s expected cash runway; and the expected costs and cost reductions associated with the restructuring. All statements other than statements of historical fact are statements that could be deemed forward-looking statements. Although the Company believes that the expectations reflected in such forward-looking statements are reasonable, the Company cannot guarantee future events, results, actions, levels of activity, performance or achievements, and the timing and results of biotechnology development and potential regulatory approval is inherently uncertain. Forward-looking statements are subject to risks and uncertainties that may cause the Company’s actual activities or results to differ significantly from those expressed in any forward-looking statement, including risks and uncertainties related to the Company’s ability to advance its product candidates, the receipt and timing of potential regulatory designations, approvals and commercialization of product candidates, the market size for the Company’s product candidates to be smaller than anticipated, clinical trial sites, supply chain and manufacturing facilities, the Company’s ability to obtain, maintain and recognize the benefits of certain designations received by product candidates, the timing and results of preclinical and clinical trials, the Company’s ability to fund development activities and achieve development goals, the Company’s ability to protect intellectual property, the Company’s commercial collaborations with third parties, the impact of health pandemics, tariffs, regional geopolitical conflicts, changes in interest rates, inflation, potential uncertainty with respect to the debt ceiling and government shutdowns, and other risks and uncertainties described under the heading “Risk Factors” in documents the Company files from time to time with the Securities and Exchange Commission. These forward-looking statements speak only as of the date of this press release, and the Company undertakes no obligation to revise or update any forward-looking statements to reflect events or circumstances after the date hereof. Investor Contact Emily White Sutro Biopharma (650) 823-7681 [email protected] Media Contact Amy Bonanno Lyra Strategic Advisory [email protected] (1) The condensed balance sheet as of March 31, 2026 was derived from the unaudited financial statements included in the Company's Quarterly Report on Form 10-Q for the quarter ended March 31, 2026, filed with the Securities and Exchange Commission on May 14, 2026. (2) The condensed balance sheet as of December 31, 2025 was derived from the audited financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2025, filed with the Securities and Exchange Commission on March 23, 2026.

– Dosed three cohorts in Phase 1 trial of STRO-004, potential best-in-class Tissue Factor (TF) ADC; on track to report initial clinical data in mid-2026 – – Company announced first wholly owned dual-payload program targeting PTK7, STRO-227, accelerating IND submission to 2026 – – Astellas-partnered iADC dual-payload program enters the clinic; patient dosing underway – – Cash, cash equivalents and marketable securities as of December 31, 2025 of $141.4 million, excluding proceeds from the recent capital raise of approximately $110 million which extended cash runway into at least the second quarter of 2028 – SOUTH SAN FRANCISCO, Calif., March 23, 2026 (GLOBE NEWSWIRE) -- Sutro Biopharma, Inc. (Sutro or the Company) (NASDAQ: STRO), a clinical-stage oncology company pioneering site-specific and novel-format antibody drug conjugates (ADCs), today reported its financial results for the full year 2025 and recent business highlights. “2026 is poised to be a pivotal year, propelled by disciplined clinical execution and initial data that we believe will showcase the vast potential of our proprietary ADC platform,” said Jane Chung, Sutro’s Chief Executive Officer. “We recently completed dosing the third cohort in the Phase 1 trial of STRO-004, our potential best-in-class Tissue Factor ADC, and look forward to reporting initial data mid-year. In parallel, we are advancing STRO-006, our ITGB6 ADC, and accelerating STRO-227, our wholly owned dual-payload program targeting PTK7, toward IND submission this year. In addition, patient dosing has commenced under our collaboration with Astellas Pharma for our first partnered dual-payload iADC — marking the first dual-payload program from Sutro’s platform to enter the clinic. Supported by our recent financing, continued financial stewardship, and sharpened strategic focus, we believe we are well positioned to execute across all our programs and deliver differentiated ADCs with best-in-class potential that could redefine standards of care in oncology.” Wholly Owned Pipeline STRO-004: The Company has completed dosing across three cohorts in the first-in-human Phase 1 trial evaluating STRO-004, a DAR8 Topo1 ADC targeting Tissue Factor (TF), with potential as best-in-class TF ADC. Initial clinical data are expected in mid-2026, including safety and tolerability. Sutro also expects to share pharmacokinetic exposure and potentially early signs of activity. In non-human primate studies, STRO-004 demonstrated a favorable preclinical safety profile, with a highest non-severely toxic dose (HNSTD) of 50 mg/kg — supporting a clinical starting dose of 1mg/kg. STRO-006: A highly selective, DAR 8 Topo1 ADC targeting integrin β6 (ITGB6), STRO-006 is expected to enter clinical development in 2026 for the treatment of multiple solid tumors. STRO-227: Sutro’s PTK7-targeting dual-payload ADC program, consisting of MMAE (DAR2) and Topo1 (DAR8), remains on track, with an IND submission targeted for 2026. Next-Generation ADC Collaborations Astellas: Two research and development programs are progressing under Sutro’s collaboration with Astellas focused on dual-payload immunostimulatory ADCs (iADCs). The first program, targeting TROP2, has entered the clinic and is actively dosing patients, triggering a $10 million milestone payment with receipt expected in the second quarter of 2026. The second program entered an IND-enabling toxicology study in the fourth quarter of 2025, triggering a $7.5 million milestone payment to Sutro. Upcoming and Recent Industry/Medical Conferences American Association for Cancer Research (AACR), April 17-22, 2026, San Diego California Sutro’s strategic partner, Astellas Pharma, will present preclinical results from its TROP2-targeted iADC program in an oral presentation on Sunday, April 19, 2026 at 4:35-4:50 PM PT. The presentation, titled “ASP2998, a TROP2-targeted immunostimulatory antibody-drug conjugate (iADC) with dual payloads, demonstrates potent efficacy and a favorable safety profile in nonclinical models,” highlights progress in the development of next-generation iADCs leveraging Sutro’s cell-free protein synthesis platform. Additionally, Sutro will present an oral presentation and multiple posters highlighting advances across its ADC pipeline and discovery platforms at AACR. The presentation details are as follows: Presentation: “STRO-004, an exatecan-based next-generation tissue factor (TF)-targeted ADC, demonstrates superior efficacy across TF-expressing solid tumors in a comprehensive single-mouse PDX trial” Presentation Date and Time: Sunday, April 19, 2026; 4:35-4:50 PM PT Poster: “Phase 1 open-label study to evaluate safety, pharmacokinetics, and preliminary anti-tumor activity of STRO-004 in adults with refractory/recurrent metastatic solid tumors” Session Date and Time: Monday, April 20, 2026; 9:00 AM-12:00 PM PT Poster: “STRO-006: An Integrin beta-6–targeting ADC demonstrates favorable safety profile and potent antitumor activity in preclinical solid tumors” Session Date and Time: Monday, April 20, 2026; 9:00 AM-12:00 PM PT Poster: “Preclinical characterization of STRO-227: A PTK7-targeting dual-payload ADC with topoisomerase 1 and tubulin inhibitors” Session Date and Time: Monday, April 20, 2026; 9:00 AM-12:00 PM PT Poster: “The HER2-targeting dual-payload antibody-drug conjugate combining a topoisomerase I inhibitor and a microtubule inhibitor demonstrates superior efficacy and overcomes resistance to single-payload ADCs in xenograft models” Session Date and Time: Monday, April 20, 2026; 9:00 AM-12:00 PM PT Poster: “Sutro’s Site-Specific Dual-Payload ADCs Combining TOPO1i and DNA Damage Response Inhibitors to Enhance Efficacy, Overcome Resistance, and Improve Safety” Session Date and Time: Tuesday, April 21, 2026; 9:00 AM-12:00 PM PT 16th World ADC London Summit, February 23-26, 2026, London, UK ·Sutro participated in a plenary and two panel discussions at the conference, covering topics including dual-payload innovation, key drivers of ADC differentiation, and ADC collaborations. For more details, read the full press release here. Corporate Updates Sutro strengthened its cash position with an underwritten offering of 7,868,383 shares of its common stock at a price of $13.98 per share, resulting in gross proceeds of $110.0 million, before deducting underwriting discounts and commissions and other offering expenses payable by Sutro. The Company’s cash runway is now expected into at least the second quarter of 2028, excluding additional anticipated milestones from Sutro's existing collaboration. Sutro management, joined by KOL Anthony Tolcher, M.D., FRCPC, FACP, hosted a virtual R&D Day on Wednesday, November 12, highlighting the Company’s platform innovations and next-generation ADC pipeline. Key updates included the initiation of the Phase 1 study with STRO-004 and the selection of PTK7 as the target for its initial dual-payload candidate, STRO-227. Full Year 2025 Financial Highlights Cash, Cash Equivalents and Marketable Securities As of December 31, 2025, Sutro had cash, cash equivalents and marketable securities of $141.4 million, as compared to $167.6 million as of September 30, 2025. With gross proceeds from the recent financing totaling $110.0 million, the Company’s cash runway is expected into at least the second quarter of 2028, excluding anticipated milestones from Sutro's existing collaborations. Revenue Revenue was $102.5 million for the year ended December 31, 2025, as compared to $62.0 million for the year ended December 31, 2024, with the 2025 amount related principally to the Astellas and Ipsen collaborations. Future collaboration and license revenue under existing agreements, and from any additional collaboration and license partners, will fluctuate as a result of the amount and timing of revenue recognition of upfront, milestones, and other agreement payments. Research & Development (R&D) and General & Administrative (G&A) Expenses Total R&D and G&A expenses for the year ended December 31, 2025 were $207.4 million, as compared to $300.5 million for the year ended December 31, 2024. The 2025 year includes non-cash expenses for stock-based compensation of $14.0 million and depreciation and amortization of $7.3 million, as compared to $24.7 million and $7.2 million, respectively, in the comparable 2024 period. Restructuring Costs The total cash payments and costs related to the further operational restructuring announced on September 29, 2025 are estimated to be approximately $4.1 million to $4.3 million, with a majority of these amounts paid in the fourth quarter of 2025. These estimates are subject to a number of assumptions and actual results may differ. The Company may also incur additional costs not currently contemplated due to events that may occur as a result of, or that are associated with, the corporate restructuring. About Sutro Biopharma Sutro Biopharma, Inc. is a clinical-stage biotechnology company advancing a next-generation antibody-drug conjugate (ADC) platform designed to deliver single- and dual-payload ADCs that enable meaningful breakthroughs for patients with cancer. By fully optimizing the antibody, linker, and payload, Sutro’s cell-free platform produces ADCs that are engineered to improve drug exposure, reduce side effects, and expand the range of treatable tumor types. With unique capabilities in dual-payload ADCs, Sutro aims to overcome treatment resistance and redefine what’s possible in cancer therapy. The Company’s pipeline of single- and dual-payload ADCs targets large oncology markets with limited treatment options and significant need for improved therapies. For more information, follow Sutro on social media @Sutrobio or visit www.sutrobio.com. Forward-Looking Statements This press release contains forward-looking statements within the meaning of the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995, including, but not limited to, anticipated preclinical and clinical development activities; timing of announcements of IND submissions, trial initiation, clinical results, and other regulatory filings; outcome of discussions with regulatory authorities; potential benefits of the Company’s product candidates and platform; potential business development and partnering transactions; potential market opportunities for the Company’s product candidates; the timing and receipt of anticipated future milestone payments; the Company’s expected cash runway; and the expected costs and cost reductions associated with the restructuring. All statements other than statements of historical fact are statements that could be deemed forward-looking statements. Although the Company believes that the expectations reflected in such forward-looking statements are reasonable, the Company cannot guarantee future events, results, actions, levels of activity, performance or achievements, and the timing and results of biotechnology development and potential regulatory approval is inherently uncertain. Forward-looking statements are subject to risks and uncertainties that may cause the Company’s actual activities or results to differ significantly from those expressed in any forward-looking statement, including risks and uncertainties related to the Company’s ability to advance its product candidates, the receipt and timing of potential regulatory designations, approvals and commercialization of product candidates, the market size for the Company’s product candidates to be smaller than anticipated, clinical trial sites, supply chain and manufacturing facilities, the Company’s ability to obtain, maintain and recognize the benefits of certain designations received by product candidates, the timing and results of preclinical and clinical trials, the Company’s ability to fund development activities and achieve development goals, the Company’s ability to protect intellectual property, and the Company’s commercial collaborations with third parties and other risks and uncertainties described under the heading “Risk Factors” in documents the Company files from time to time with the Securities and Exchange Commission. These forward-looking statements speak only as of the date of this press release, and the Company undertakes no obligation to revise or update any forward-looking statements to reflect events or circumstances after the date hereof. Sutro Biopharma, Inc. Selected Statements of Operations Financial Data (Unaudited) (In thousands, except share and per share amounts) Sutro Biopharma, Inc. Selected Balance Sheets Financial Data (Unaudited) (In thousands) CONTACT: Investor Contact Emily White Sutro Biopharma (650) 823-7681 [email protected] Media Contact Amy Bonanno Lyra Strategic Advisory [email protected]

– Company announces U.S. FDA clearance of Investigational New Drug (IND) application for STRO-004, its potential best-in-class Tissue Factor ADC; Expects to dose first patient before year-end – – Company presented new preclinical data at World ADC and SITC, highlighting novel dual-payload ADCs designed to overcome resistance and delay progression – – Company to host a virtual R&D Day on Wednesday, November 12, 2025 at 10:00AM ET – – Cash, cash equivalents and marketable securities as of September 30, 2025 of $167.6 million, with cash runway into at least mid-2027, including certain expected near-term milestone payments – SOUTH SAN FRANCISCO, Calif., Nov. 06, 2025 (GLOBE NEWSWIRE) -- Sutro Biopharma, Inc. (Sutro or the Company) (NASDAQ: STRO), an oncology company pioneering site-specific and novel-format antibody drug conjugates (ADCs), today reported its financial results for the third quarter of 2025 and recent business highlights. “We’ve made strong progress this quarter as we continue to build momentum across our next-generation ADC portfolio,” said Jane Chung, Sutro’s Chief Executive Officer. “STRO-004, our Tissue Factor ADC, has received IND clearance ahead of our projections and remains on track to enter the clinic this year, backed by compelling preclinical data that highlight its strong safety profile and potential best-in-class differentiation. In parallel, we’re strengthening our leadership in dual-payload ADCs by showcasing positive new preclinical data from our wholly owned programs and advancing our collaboration with Astellas. This collaboration focuses on developing dual-payload ADCs that combine a cytotoxic payload with a novel immunostimulatory payload, designed to enhance the therapeutic index and overcome tumor resistance. We look forward to sharing updates on each of our next-generation ADC programs at our virtual R&D Day on November 12.” Ms. Chung continued: “Following our recent organizational restructuring, we are well positioned to focus resources on the programs and partnerships that offer the greatest potential for near-term value creation. The resulting operational efficiencies, combined with expected near-term milestone payments, extend our cash runway into at least mid-2027—allowing us to advance key programs through meaningful clinical milestones. With a sharpened strategic focus and a robust scientific foundation, we believe Sutro is poised to deliver differentiated best-in-class ADCs that have the potential to redefine standards of care in oncology.” Wholly Owned Pipeline STRO-004: The Company received U.S. FDA clearance of its IND application for STRO-004, its potential best-in-class Tissue Factor ADC. Sutro remains on track to dose the first patient in the first-in-human basket trial with STRO-004 before year-end. STRO-004 has a favorable preclinical safety profile in non-human primate studies up to 50 mg/kg, the highest dose tested. STRO-006: A highly selective integrin β6 (ITGB6) ADC, STRO-006 is expected to enter clinical development in 2026 for the treatment of multiple solid tumors. Dual-Payload Program: Sutro’s wholly owned dual-payload ADC program remains on track, with an IND submission targeted for 2027. Next-Generation ADC Collaborations Astellas: Two research and development programs are progressing under Sutro’s collaboration with Astellas focused on dual-payload immunostimulatory ADCs (iADCs), including one program that entered an IND-enabling toxicology study in the first quarter of 2025. Industry/Medical Conferences 16th Annual World ADC Conference, November 3-6, 2025, San Diego, CA Sutro conducted five presentations and participated in three panel sessions at the conference, demonstrating its continued leadership in ADC innovation. For additional details, read the full press release here. Society for Immunotherapy of Cancer (SITC) 2025 Annual Meeting, November 7-9, 2025, National Harbor, MD Sutro will have a poster presentation at the conference, highlighting preclinical results that demonstrate the ability of novel immunostimulatory dual-payload ADCs to enhance therapeutic index and overcome patient resistance. The posters will be made available on the Presentation & Publication section of Company’s website. Upcoming Investor Conferences Management will participate in the following upcoming healthcare investor conference. A webcast of the presentation will be accessible through the News & Events page of the Investor Relations section of the Company’s website at www.sutrobio.com. An archived replay will be available for at least 30 days after the event. 37th Annual Piper Sandler Healthcare Conference, December 2-4, 2025, New York, NY Corporate Updates Sutro management will host a virtual R&D Day on Wednesday, November 12 at 10:00AM ET, including presentations from Sutro management and a guest speaker. To access the live audio webcast, please go to https://ir.sutrobio.com/news-events/ir-calendar. An archived replay of the webcast will be available on the Company’s website following the event. In September, Sutro announced an organizational restructuring to prioritize the advancement of its ADC programs and research and development collaborations. Along with certain near-term milestone payments, the restructuring is expected to extend the Company’s runway into at least mid-2027, following the planned release of initial clinical data from STRO-004, its next-generation Tissue Factor–targeting exatecan ADC, and initiation of clinical studies for at least one other ADC program. Third Quarter 2025 Financial Highlights Cash, Cash Equivalents and Marketable Securities As of September 30, 2025, Sutro had cash, cash equivalents and marketable securities of $167.6 million, as compared to $388.3 million as of September 30, 2024. Cost reductions subsequently realized from the restructuring, combined with refocused clinical development priorities and certain expected near-term milestone payments give the Company an expected cash runway into at least mid-2027. Revenue Revenue was $9.7 million for the quarter ended September 30, 2025, as compared to $8.5 million for the quarter ended September 30, 2024, with the 2025 amount related principally to the Astellas collaboration. Future collaboration and license revenue under existing agreements, and from any additional collaboration and license partners, will fluctuate as a result of the amount and timing of revenue recognition of upfront, milestones, and other agreement payments. Research & Development (R&D) and General & Administrative (G&A) Expenses Total R&D and G&A expenses for the quarter ended September 30, 2025 were $48.6 million, as compared to $76.4 million for the quarter ended September 30, 2024. The 2025 quarter includes non-cash expenses for stock-based compensation of $1.9 million and depreciation and amortization of $1.9 million, as compared to $6.5 million and $1.8 million, respectively, in the comparable 2024 period. Restructuring Costs The total cash payments and costs related to the further operational restructuring announced on September 29, 2025 are estimated to be approximately $4.1 million to $4.3 million, with a significant majority of these amounts expected to be paid in the fourth quarter of 2025. These estimates are subject to a number of assumptions and actual results may differ. The Company may also incur additional costs not currently contemplated due to events that may occur as a result of, or that are associated with, the corporate restructuring. About Sutro Biopharma Sutro Biopharma, Inc. is advancing a next-generation antibody-drug conjugate (ADC) platform designed to deliver single- and dual-payload ADCs that enable meaningful breakthroughs for patients with cancer. By fully optimizing the antibody, linker, and payload, Sutro’s cell-free platform produces ADCs that are engineered to improve drug exposure, reduce side effects, and expand the range of treatable tumor types. With unique capabilities in dual-payload ADCs, Sutro aims to overcome treatment resistance and redefine what’s possible in cancer therapy. The Company’s pipeline of single- and dual-payload ADCs targets large oncology markets with limited treatment options and significant need for improved therapies. For more information, follow Sutro on social media @Sutrobio or visit www.sutrobio.com. Forward-Looking Statements This press release contains forward-looking statements within the meaning of the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995, including, but not limited to, anticipated preclinical and clinical development activities; timing of announcements of IND submissions, trial initiation, clinical results, and other regulatory filings; outcome of discussions with regulatory authorities; potential benefits of the Company’s product candidates and platform; potential business development and partnering transactions; potential market opportunities for the Company’s product candidates; the timing and receipt of anticipated future milestone payments; the Company’s expected cash runway; and the expected costs and cost reductions associated with the restructuring. All statements other than statements of historical fact are statements that could be deemed forward-looking statements. Although the Company believes that the expectations reflected in such forward-looking statements are reasonable, the Company cannot guarantee future events, results, actions, levels of activity, performance or achievements, and the timing and results of biotechnology development and potential regulatory approval is inherently uncertain. Forward-looking statements are subject to risks and uncertainties that may cause the Company’s actual activities or results to differ significantly from those expressed in any forward-looking statement, including risks and uncertainties related to the Company’s ability to advance its product candidates, the receipt and timing of potential regulatory designations, approvals and commercialization of product candidates, the market size for the Company’s product candidates to be smaller than anticipated, clinical trial sites, supply chain and manufacturing facilities, the Company’s ability to obtain, maintain and recognize the benefits of certain designations received by product candidates, the timing and results of preclinical and clinical trials, the Company’s ability to fund development activities and achieve development goals, the Company’s ability to protect intellectual property, and the Company’s commercial collaborations with third parties and other risks and uncertainties described under the heading “Risk Factors” in documents the Company files from time to time with the Securities and Exchange Commission. These forward-looking statements speak only as of the date of this press release, and the Company undertakes no obligation to revise or update any forward-looking statements to reflect events or circumstances after the date hereof. Investor Contact Emily White Sutro Biopharma (650) 823-7681 [email protected] Media Contact Amy Bonanno Lyra Strategic Advisory [email protected] Sutro Biopharma, Inc. Selected Statements of Operations Financial Data (Unaudited) (In thousands, except share and per share amounts) Sutro Biopharma, Inc. Selected Balance Sheets Financial Data (Unaudited) (In thousands) (1) The condensed balance sheet as of September 30, 2025 was derived from the unaudited financial statements included in the Company's Quarterly Report on Form 10-Q for the quarter ended September 30, 2025, filed with the Securities and Exchange Commission on November 6, 2025. (2) The condensed balance sheet as of December 31, 2024 was derived from the audited financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2024, filed with the Securities and Exchange Commission on March 13, 2025.

– On track to initiate FIH study with STRO-004, potential best-in-class Tissue Factor ADC, in the second half of 2025 – – Expanded breadth of preclinical data across pipeline, including STRO-006 and dual-payload ADCs – – Entered research collaboration with the FDA to advance regulatory standards for ADCs – – Industry veteran Greg Chow appointed as Chief Financial Officer – – Cash, cash equivalents and marketable securities as of June 30, 2025 of $205.1 million, with cash runway into early 2027 – SOUTH SAN FRANCISCO, Calif., Aug. 07, 2025 (GLOBE NEWSWIRE) -- Sutro Biopharma, Inc. (Sutro or the Company) (NASDAQ: STRO), an oncology company pioneering site-specific and novel-format antibody drug conjugates (ADCs), today reported its financial results for the second quarter of 2025 and recent business highlights. “In the second quarter, we made strong progress advancing our pipeline of novel ADCs, including preparing to initiate a clinical trial for STRO-004—our next-generation, Tissue Factor-targeting exatecan ADC—planned for the second half of this year,” said Jane Chung, Sutro’s Chief Executive Officer. “Over the past several months, we’ve generated compelling preclinical data across our entire pipeline, further supporting our candidates’ best-in-class potential as well as highlighting the unique capabilities of our platform technology.” Ms. Chung continued: “We are especially excited about our dual-payload ADCs—an area where we are at the forefront of innovation and see significant potential to transform cancer treatment by unlocking durable efficacy. We are already seeing early validation through our strategic collaboration with Astellas, underscored by the initiation of an IND-enabling toxicology study for the first dual-payload immunostimulatory ADC. As we look to the second half of the year, we are well capitalized to meet our top priority of pipeline execution which we believe is critical to increasing shareholder value and we continue to look for ways to implement operating efficiencies and further extend our cash runway.” Wholly-Owned Pipeline STRO-004: IND preparations are well underway, with a first-in-human basket trial on track to begin in the second half of 2025, initially focused on solid tumors. STRO-004 has a favorable preclinical safety profile in cynomolgus monkeys up to 50 mg/kg, the highest dose tested. STRO-006: Sutro’s differentiated integrin beta-6 (ITGB6) ADC is expected to enter clinical development in 2026 for the treatment of multiple solid tumors. Dual-Payload Program: Sutro continues to progress its wholly-owned dual-payload ADC platform, with an IND filing anticipated in 2027. Next-Generation ADC Collaborations Astellas: Two research and development programs are progressing under Sutro’s collaboration with Astellas focused on dual-payload immunostimulatory ADCs (iADCs), including one program that recently entered an IND-enabling toxicology study—triggering a $7.5 million milestone payment to Sutro. Ipsen: Ipsen made a strategic decision not to advance the STRO-003 program under its partnership with Sutro, following the review of new data and developments in the ROR1 landscape. STRO-003 continues to be recognized as a well-engineered ADC candidate. This decision does not have any impact on the Company’s previous guidance on cash runway. Medical Conferences 4th World ADC Asia Summit: In June, Sutro shared preclinical data demonstrating the potential for dual-payload ADCs to overcome prior ADC resistance in tumor models. The Company also shared encouraging safety data in non-human primates for dual-payload ADC DAR8 exatecan + DAR4 MMAE at a dose of 12.5 mg/kg. 21st Annual PEGS Boston: The Essential Protein Engineering & Cell Therapy Summit: In May, Sutro shared preclinical data on STRO-006, demonstrating superior anti-tumor activity compared to first-generation ITGB6 ADCs at clinically relevant dose levels. The data also highlighted a favorable pharmacokinetic and tolerability profile at 25 mg/kg dose. 2025 AACR Annual Meeting: In April, Sutro presented encouraging preclinical results from STRO-004 and its dual-payload ADC programs. Notably, a single dose of STRO-004 produced promising overall response and disease control rates in Tissue Factor-positive patient-derived xenograft models across multiple tumor types. Upcoming Investor Conference Management will participate in the following upcoming healthcare investor conference. A webcast of the presentation will be accessible through the News & Events page of the Investor Relations section of the Company’s website at www.sutrobio.com. An archived replay will be available for at least 30 days after the event. Wells Fargo Healthcare Conference, September 3-5, 2025, in Boston Corporate Updates In July, Sutro announced a research collaboration with the U.S. Food and Drug Administration (FDA) to develop reference materials to improve regulatory standards and enhance analytical methods for ADC drug development. In June, Sutro appointed Greg Chow as Chief Financial Officer. Second Quarter 2025 Financial Highlights Cash, Cash Equivalents and Marketable Securities As of June 30, 2025, Sutro had cash, cash equivalents and marketable securities of $205.1 million, as compared to $249.0 million as of March 31, 2025. Cost reductions subsequently realized from the restructuring, combined with refocused clinical development priorities give the Company an expected cash runway into early 2027, excluding additional anticipated milestones from existing collaborations. Revenue Revenue was $63.7 million for the quarter ended June 30, 2025, as compared to $25.7 million for the quarter ended June 30, 2024, with the 2025 amount related principally to the Astellas collaboration and the recognition of previously deferred revenue as a result of Ipsen’s decision not to advance the STRO-003 program under its partnership with Sutro. Future collaboration and license revenue under existing agreements, and from any additional collaboration and license partners, will fluctuate as a result of the amount and timing of revenue recognition of upfront, milestones, and other agreement payments. Research & Development (R&D) and General & Administrative (G&A) Expenses Total R&D and G&A expenses for the quarter ended June 30, 2025 were $48.7 million, as compared to $74.4 million for the quarter ended June 30, 2024. The 2025 period includes non-cash expenses for stock-based compensation of $2.8 million and depreciation and amortization of $1.9 million, as compared to $6.2 million and $1.8 million, respectively, in the 2024 period. For the quarter ended June 30, 2025, R&D expenses were $38.4 million and G&A expenses were $10.3 million. Restructuring and Related Costs Restructuring and related costs for the quarter ended June 30, 2025 were $18.4 million. Sutro will continue to recognize restructuring and related costs in future periods for the deprioritization of the luvelta program, of which it expects to recognize a significant portion in 2025. The ultimate amount of expense will be affected by the timing to complete Sutro’s cost commitments to its third-party CROs and CMOs and the full wind-down of the clinical trials. Sutro will revise its estimates of the costs to deprioritize these studies for the luvelta program and the amount of severance and benefits paid to employees as new information becomes available to the Company in future periods. About Sutro Biopharma Sutro Biopharma, Inc., is relentlessly focused on the discovery and development of precisely designed cancer therapeutics to transform what science can do for patients. Sutro’s fit-for-purpose technology, including cell-free XpressCF®, provides the opportunity for broader patient benefit and an improved patient experience. Sutro is advancing a robust early-stage pipeline of novel exatecan and dual-payload antibody drug conjugates (ADCs), coupled with high-value collaborations and industry partnerships, which validate its continuous product innovation. Sutro is headquartered in South San Francisco. For more information, follow Sutro on social media @Sutrobio, or visit www.sutrobio.com. Forward-Looking Statements This press release contains forward-looking statements within the meaning of the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995, including, but not limited to, anticipated preclinical and clinical development activities; timing of announcements of IND submissions, clinical results, trial initiation, and other regulatory filings; outcome of discussions with regulatory authorities; potential benefits of the Company’s product candidates and platform; potential business development and partnering transactions; potential market opportunities for the Company’s product candidates; the timing of exiting the manufacturing facility in San Carlos; the timing and receipt of anticipated future milestone payments; the Company’s expected cash runway; and the expected costs and cost reductions associated with the restructuring. All statements other than statements of historical fact are statements that could be deemed forward-looking statements. Although the Company believes that the expectations reflected in such forward-looking statements are reasonable, the Company cannot guarantee future events, results, actions, levels of activity, performance or achievements, and the timing and results of biotechnology development and potential regulatory approval is inherently uncertain. Forward-looking statements are subject to risks and uncertainties that may cause the Company’s actual activities or results to differ significantly from those expressed in any forward-looking statement, including risks and uncertainties related to the Company’s ability to advance its product candidates, the receipt and timing of potential regulatory designations, approvals and commercialization of product candidates, the market size for the Company’s product candidates to be smaller than anticipated, clinical trial sites, supply chain and manufacturing facilities, the Company’s ability to obtain, maintain and recognize the benefits of certain designations received by product candidates, the timing and results of preclinical and clinical trials, the Company’s ability to fund development activities and achieve development goals, the Company’s ability to protect intellectual property, and the Company’s commercial collaborations with third parties and other risks and uncertainties described under the heading “Risk Factors” in documents the Company files from time to time with the Securities and Exchange Commission. These forward-looking statements speak only as of the date of this press release, and the Company undertakes no obligation to revise or update any forward-looking statements to reflect events or circumstances after the date hereof. Investor Contact Emily White Sutro Biopharma (650) 823-7681 [email protected] Media Contact Amy Bonanno Lyra Strategic Advisory [email protected] (1) The condensed balance sheet as of June 30, 2025 was derived from the unaudited financial statements included in the Company's Quarterly Report on Form 10-Q for the quarter ended June 30, 2025, filed with the Securities and Exchange Commission on August 7, 2025. (2) The condensed balance sheet as of December 31, 2024 was derived from the audited financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2024, filed with the Securities and Exchange Commission on March 13, 2025.

- Sharpened product candidate focus on its next-generation ADC portfolio, following strategic review and pipeline reprioritization - - Promising preclinical results with STRO-004 and dual-payload ADC, as well as STRO-006 programs presented at AACR 2025 and PEGS, respectively - - Three INDs for wholly-owned programs anticipated in next 3 years, beginning with potential best-in-class Tissue Factor ADC, STRO-004, planned for 2H 2025 - - IND-enabling toxicology study ongoing for one program within Astellas iADC collaboration, triggering $7.5 million milestone payment to Sutro - - Cash, cash equivalents and marketable securities as of March 31, 2025 of $249.0 million, with cash runway expected into early 2027, excluding additional anticipated milestones from existing collaborations - SOUTH SAN FRANCISCO, Calif., May 08, 2025 (GLOBE NEWSWIRE) -- Sutro Biopharma, Inc. (Sutro or the Company) (NASDAQ: STRO), an oncology company pioneering site-specific and novel-format antibody drug conjugates (ADCs), today reported its financial results for the first quarter of 2025 and recent business highlights. “In the first quarter, we announced a strategic decision to shift Sutro’s product candidate focus from luvelta to our pipeline of wholly-owned novel exatecan and dual-payload ADCs. As part of this review, we selected STRO-004—a next-generation Tissue Factor-targeting exatecan/Topo 1 ADC—as our lead clinical candidate, supported by strong preclinical data that point to its best-in-class potential,” said Jane Chung, Sutro’s Chief Executive Officer. “At AACR, we presented on STRO-004’s potent, dose-dependent anti-tumor activity and favorable safety profile across multiple dose levels and highlighted the unique capabilities of our XpressCF+® cell-free platform to develop novel dual-payload ADCs—an approach that holds significant promise for some of the most difficult-to-treat cancers. Additionally, next week, we have the opportunity to present preclinical data on STRO-006 for the first time, demonstrating encouraging pharmacokinetics (PK) and anti-tumor activity.” Ms. Chung continued: “We currently are on track to deliver three new INDs over the next three years, starting with STRO-004, which is expected to enter clinical studies in the second half of this year. Our rich pipeline, made possible by our optimized cell-free platform, is designed to engage complex, hard-to-drug targets with next-generation single- and dual-payloads. We are also already seeing the extraordinary capabilities of our platform yield important advances in our collaboration with Astellas, with the recent initiation of an IND-enabling toxicology study for the first dual-payload immunostimulatory ADC program under our collaboration, triggering a milestone payment to Sutro. Our team remains inspired by the immense potential of our platform and pipeline, and the substantial benefit it can bring to patients and to our partners.” Corporate and Program Updates In March, Sutro announced completion of a strategic portfolio review resulting in the prioritization of its wholly-owned next-generation ADC programs. While Sutro will not continue the development of luveltamab tazevibulin (luvelta) on its own, it remains open to partnership opportunities. Wholly-Owned Pipeline STRO-004: Sutro’s novel exatecan Tissue Factor ADC has been prioritized as the Company’s lead program, with an initial focus on solid tumors. The Company is preparing to submit an IND and initiate a first-in-human study in the second half of 2025. STRO-006: Sutro’s differentiated integrin beta-6 (ITGB6) ADC is expected to enter clinical development in 2026, aimed at multiple solid tumors. Dual-Payload Program: An IND for Sutro’s first wholly-owned dual-payload ADC is anticipated to be filed in 2027. Existing Collaborations for Next-Generation ADCs Ipsen: A drug development program is ongoing with Ipsen for STRO-003, a ROR1 ADC. Astellas: Two research and development programs are ongoing with Astellas for dual-payload immunostimulatory ADCs (iADCs), one of which has initiated an IND-enabling toxicology study triggering a milestone payment to Sutro. These collaborations remain a strategic priority given their long-term value creation potential and the increasing relevance of specialized ADCs in the treatment of cancer. Medical Conferences 21st Annual PEGS Boston: The Essential Proteins Engineering & Cell Therapy Summit: In May, Sutro will present promising preclinical data with STRO-006, highlighting its superior anti-tumor activity compared to first generation ITGB6 ADCs at clinically relevant dose levels, as well as its favorable PK and tolerability profile. 2025 American Association for Cancer Research (AACR) Annual Meeting: In April, Sutro presented encouraging preclinical results with STRO-004 and its dual-payload ADC programs. Among the highlights, a single dose of STRO-004 led to promising overall response and disease control rates in Tissue Factor-positive patient-derived xenograft models spanning multiple cancer types. Additionally, STRO-004 has a favorable safety profile in cynomolgus monkeys up to 50 mg/kg, the highest dose tested. Society of Gynecologic Oncology (SGO) Annual Meeting on Women’s Cancer®: In March, expanded data were presented in a late-breaking oral presentation from the dose-optimization portion of the REFRαME-O1 trial with luvelta in patients with platinum resistant ovarian cancer. In the study, luvelta demonstrated encouraging antitumor activity in patients with late-stage ovarian cancer across all levels of Folate Receptor-α expression of 25% or greater, including an improved overall response rate, a low discontinuation rate, and a consistent safety profile across dose levels. Upcoming Investor Conferences Management will participate in the following upcoming healthcare investor conferences. Webcasts of the presentations will be accessible through the News & Events page of the Investor Relations section of the Company’s website at www.sutrobio.com. Archived replays will be available for at least 30 days after the event. TD Cowen’s 6th Annual Oncology Innovation Summit, May 27-28, 2025, Virtual Jefferies 2025 Global Healthcare Conference, June 3-5, 2025, in New York Organization As part of the restructuring, Jane Chung, President and Chief Operating Officer, assumed the responsibilities as Chief Executive Officer and was appointed as a member of the Sutro Board. The Company is also reducing its organizational headcount by nearly 50 percent and decommissioning its manufacturing facility by year-end 2025. Manufacturing capabilities to support the next-generation ADC pipeline have been fully established and scaled up externally. First Quarter 2025 Financial Highlights Cash, Cash Equivalents and Marketable Securities As of March 31, 2025, Sutro had cash, cash equivalents and marketable securities of $249.0 million, as compared to $316.9 million as of December 31, 2024. Cost reductions subsequently realized from the restructuring, combined with refocused clinical development priorities give the Company an expected cash runway into early 2027, excluding additional anticipated milestones from existing collaborations. Revenue Revenue was $17.4 million for the quarter ended March 31, 2025, as compared to $13.0 million for the quarter ended March 31, 2024, with the 2025 amount related principally to the Astellas collaboration. Future collaboration and license revenue under existing agreements, and from any additional collaboration and license partners, will fluctuate as a result of the amount and timing of revenue recognition of upfront, milestones, and other agreement payments. Research & Development (R&D) and General & Administrative (G&A) Expenses Total R&D and G&A expenses for the quarter ended March 31, 2025 were $64.9 million, as compared to $69.6 million for the quarter ended March 31, 2024. The 2025 period includes non-cash expenses for stock-based compensation of $5.5 million and depreciation and amortization of $1.9 million, as compared to $6.1 million and $1.8 million, respectively, in the 2024 period. For the quarter ended March 31, 2025, R&D expenses were $51.6 million and G&A expenses were $13.3 million. Restructuring and Related Costs Restructuring and related costs for the quarter ended March 31, 2025 were $21.0 million. Sutro will continue to recognize restructuring and related costs in future periods for the deprioritization of the luvelta program, of which it expects to recognize a significant portion in 2025. The ultimate amount of expense will be affected by the timing to complete Sutro’s cost commitments to its third-party CROs and CMOs and the full wind-down of the clinical trials. Sutro will revise its estimates of the costs to deprioritize these studies for the luvelta program and the amount of severance and benefits paid to employees as new information becomes available to the Company in future periods. About Sutro Biopharma Sutro Biopharma, Inc., is relentlessly focused on the discovery and development of precisely designed cancer therapeutics to transform what science can do for patients. Sutro’s fit-for-purpose technology, including cell-free XpressCF®, provides the opportunity for broader patient benefit and an improved patient experience. Sutro is advancing a robust early-stage pipeline of novel exatecan and dual-payload antibody drug conjugates (ADCs), coupled with high-value collaborations and industry partnerships, which validate its continuous product innovation. Sutro is headquartered in South San Francisco. For more information, follow Sutro on social media @Sutrobio, or visit www.sutrobio.com. Forward-Looking Statements This press release contains forward-looking statements within the meaning of the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995, including, but not limited to, anticipated preclinical and clinical development activities, including enrollment and site activation; timing of announcements of clinical results, trial initiation, and regulatory filings; outcome of discussions with regulatory authorities; potential benefits of the Company’s product candidates and platform; potential business development and partnering transactions; potential market opportunities for the Company’s product candidates; the timing of exiting the manufacturing facility in San Carlos; the timing and receipt of anticipated future milestone payments; the Company’s expected cash runway; and the expected costs and cost reductions associated with the restructuring. All statements other than statements of historical fact are statements that could be deemed forward-looking statements. Although the Company believes that the expectations reflected in such forward-looking statements are reasonable, the Company cannot guarantee future events, results, actions, levels of activity, performance or achievements, and the timing and results of biotechnology development and potential regulatory approval is inherently uncertain. Forward-looking statements are subject to risks and uncertainties that may cause the Company’s actual activities or results to differ significantly from those expressed in any forward-looking statement, including risks and uncertainties related to the Company’s ability to advance its product candidates, the receipt and timing of potential regulatory designations, approvals and commercialization of product candidates, the market size for the Company’s product candidates to be smaller than anticipated, clinical trial sites, supply chain and manufacturing facilities, the Company’s ability to obtain, maintain and recognize the benefits of certain designations received by product candidates, the timing and results of preclinical and clinical trials, the Company’s ability to fund development activities and achieve development goals, the Company’s ability to protect intellectual property, and the Company’s commercial collaborations with third parties and other risks and uncertainties described under the heading “Risk Factors” in documents the Company files from time to time with the Securities and Exchange Commission. These forward-looking statements speak only as of the date of this press release, and the Company undertakes no obligation to revise or update any forward-looking statements to reflect events or circumstances after the date hereof. (1) The condensed balance sheet as of March 31, 2025 was derived from the unaudited financial statements included in the Company's Quarterly Report on Form 10-Q for the quarter ended March 31, 2025, filed with the Securities and Exchange Commission on May 8, 2025. (2) The condensed balance sheet as of December 31, 2024 was derived from the audited financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2024, filed with the Securities and Exchange Commission on March 13, 2025. CONTACT: Investor Contact Emily White Sutro Biopharma (650) 823-7681 [email protected] Media Contact Amy Bonanno Lyra Strategic Advisory [email protected]

Release Date: March 13, 2025 For the complete transcript of the earnings call, please refer to the full earnings call transcript. Sutro Biopharma Inc (NASDAQ:STRO) has prioritized three wholly owned pre-clinical programs in its next-generation ADC pipeline, indicating a focused strategic direction. The company's cash runway has been extended into at least Q4 of 2026, providing financial stability for the near future. Sutro Biopharma Inc (NASDAQ:STRO) has established external manufacturing partnerships, allowing for scalable production capabilities. The company's proprietary technology enables precise design of ADCs, offering unique advantages over conventional methods. Sutro Biopharma Inc (NASDAQ:STRO) has attracted world-class partners such as Astellas and Ipsen, highlighting the potential and credibility of its platform. Sutro Biopharma Inc (NASDAQ:STRO) is reducing its workforce by nearly 50%, which may impact employee morale and operational capacity. The company has deprioritized the development of Levelta due to limited resources, potentially missing out on its full potential. There is a challenging macro environment affecting Sutro Biopharma Inc (NASDAQ:STRO)'s ability to advance certain programs independently. The decision to externalize manufacturing capabilities may lead to dependency on external partners for production. The company faces competition from other firms, such as Pfizer, in the ADC space, which could impact its market position. Warning! GuruFocus has detected 3 Warning Signs with STRO. Q: How should we see the value of Levelta being realized through partnerships, and what is the ideal next step? A: We are deprioritizing Levelta but are in active discussions with potential partners to realize its full potential. We have exciting data to share at SGO, and our decision is not due to a lack of belief in Levelta but rather to find a partner who can fully realize its potential. - Jane Chung, CEO Q: What data can we expect this year to support the R&D of the tissue factor program, and what should we expect next year? A: We are encouraged by preclinical data showing best-in-class potential for Stro 4. We plan to file an IND and start first-in-human trials this year, with initial clinical data expected by 2026 and 2027. - Jane Chung, CEO, and Dr. Hans Peter Gerber, CSO Q: Regarding the layoffs, were they mostly in the discovery area, and is there still a clinical effort in place for ADCs? A: The majority of layoffs are tied to Levelta workstreams. We are reallocating resources to align with new strategic priorities and externalizing manufacturing. We continue to engage in partnership discussions for Levelta and other pipeline candidates. - Jane Chung, CEO Q: How will the deprioritization of Levelta affect study enrollment and expenses, and what are the partnership expectations? A: We are winding down expenses related to Levelta while seeking a partner to take over its development. The goal is for the partner to lead future development efforts. - Jane Chung, CEO Q: Can you discuss the differentiation of your integrin beta 6 ADC program compared to Pfizer's competing program? A: Our ADC targets a specific conformation of integrin beta 6 present on tumor cells, allowing effective payload delivery without interfering with target biology. We believe our ADC has competitive attributes, particularly with our choice of payload. - Dr. Hans Peter Gerber, CSO For the complete transcript of the earnings call, please refer to the full earnings call transcript. This article first appeared on GuruFocus.