Exhibit 99.1

Sutro Biopharma Announces Interim Data from Dose-Expansion Cohort of STRO-002 Phase 1 Study for Patients with Advanced Ovarian Cancer

- 33% Objective Response Rate (ORR) was observed in 33 RECIST evaluable patients across all FolRα expression levels and both dose levels.

- Dose response was observed, with a 47% ORR in 17 patients who started at the 5.2 mg/kg dose level.

- Tumor proportion score (TPS) was selected as an appropriate scoring algorithm for identifying an enriched target patient population based on FolRa expression levels.

- An ORR of 40% was observed for patients with TPS >25%, which, based on our patient data, represents about 70% of the advanced ovarian cancer patient population.

- Emerging safety profile was generally consistent with prior STRO-002 data, with no new safety signals observed, including the absence of keratopathy.

- Co-principal investigator, Dr. Naumann, and Sutro management will present data at a STRO-002 virtual event at 2 pm PT/5 pm ET today.

SOUTH SAN FRANCISCO, Calif., Jan. 5, 2022 – Sutro Biopharma, Inc. (“Sutro” or the “Company”) (NASDAQ: STRO), a clinical-stage drug discovery, development and manufacturing company focused on the application of precise protein engineering and rational design to create next-generation cancer and autoimmune therapeutics, today provided a clinical update from the Company’s ongoing, fully enrolled, dose-expansion Phase 1 study of STRO-002, a folate receptor alpha (FolRα)-targeting antibody-drug conjugate (ADC), for patients with advanced ovarian cancer. Discussion of these data will be held at a STRO-002 Virtual Event at 2 pm PT/5 pm ET today.

“These interim data in the dose-expansion cohort showing deep responders in ovarian cancer patients treated with STRO-002 are compelling,” said Dr. R. Wendel Naumann, Professor & Director of Gynecologic Oncology Research, Associate Medical Director of Clinical Trials at Levine Cancer Institute, and an investigator on the STRO-002 study. “Patients entered the study with progressive disease and were a heavily pre-treated population and had experienced up to three lines of prior treatment. The interim data show that STRO-002 could potentially improve the lives of an underserved ovarian cancer patient population.”

The dose-expansion cohort for ovarian cancer enrolled 44 patients who had experienced up to three prior lines of therapy. As of the interim data cutoff date of Nov. 8, 2021, 43 patients had been randomized into dose levels starting at 4.3 mg/kg and 5.2 mg/kg, and one patient had not yet been dosed. 81% of the patients were platinum-resistant, and 63% and 65% of the patients had been treated previously with bevacizumab and PARP inhibitors, respectively. Of the 43 patients, 33 had at least one post-baseline scan and, therefore, were evaluable for RECIST v1.1 responses.

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Exhibit 99.1

Dr. Arturo Molina, Chief Medical Officer of Sutro, added, “We are encouraged by the investigator interest in STRO-002 in the dose-expansion cohort, with full patient enrollment in under a year. These interim data underscore our confidence in STRO-002 as a potential therapeutic for patients with ovarian cancer, and we will continue to follow the patients who remain on treatment. With additional data continuing to mature, we expect to confirm our dosing regimen and our patient selection strategy based on FolRα expression. We plan to advance STRO-002 into the next phase of clinical development and leverage our Fast Track designation for continuous engagement with the FDA.”

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Exhibit 99.1

In addition to the STRO-002-GM1 Phase 1 clinical trial, a STRO-002 study for patients with ovarian cancer in combination with bevacizumab and a study for patients with endometrial cancer are both enrolling at sites in the United States and Europe. Nonclinical work to expand STRO-002 to non-small cell lung cancer (NSCLC) and potentially into other FolRα-expressing solid tumors is also ongoing.

STRO-002 Virtual Event Information

The data will be presented by Sutro management and Dr. R. Wendel Naumann, Co-Principal Investigator in the STRO-002-GM1 studies. Dr. Naumann is a professor and Director of Gynecologic Oncology Research and Associate Medical Director of Clinical Trials at the Levine Cancer Institute, Atrium Health in Charlotte, North Carolina. Dr. Naumann is also a member of Sutro's Clinical Advisory Board.

To access the event by webcast, please click here: https://event.webcasts.com/starthere.jsp?ei=1520589&tp_key=62ffe993bc

To access the event by phone, please dial: (877) 405-1224 or (201) 389-0848

The webcast and dial-in information will also be available through the News and Events page of the Investor Relations section on the Company’s website at www.sutrobio.com. An archived replay will be available for at least 30 days after the event.

About Sutro Biopharma

Sutro Biopharma, Inc., located in South San Francisco, is a clinical-stage drug discovery, development and manufacturing company. Using precise protein engineering and rational design, Sutro is advancing next-generation oncology therapeutics.

Sutro’s proprietary and integrated cell-free protein synthesis platform XpressCF® and site-specific conjugation platform XpressCF+™ led to the discovery of STRO-001 and STRO-002, Sutro’s first two internally-developed ADCs. STRO-001 is a CD74-targeting ADC currently under investigation in a Phase 1 clinical trial for patients with advanced B-cell malignancies and was granted Orphan Drug Designation by the FDA for multiple myeloma. STRO-002, a folate receptor alpha (FolRα)-targeting ADC, is currently being investigated in a Phase 1 clinical trial for patients with ovarian and endometrial cancers and was granted Fast Track designation by the FDA for ovarian cancer. A third product candidate, CC-99712, a BCMA-targeting ADC, which is part of Sutro’s collaboration with Bristol Myers Squibb, formerly Celgene Corporation, is enrolling patients for its Phase 1 clinical trial of patients with multiple myeloma and has received Orphan Drug Designation from the FDA. A fourth product candidate, M1231, a MUC1-EGFR, bispecific ADC, which is part of Sutro’s collaboration with Merck KGaA, Darmstadt, Germany, known as EMD Serono in the U.S. and Canada (EMD Serono), is enrolling patients for its Phase 1 clinical trial of patients with metastatic solid tumors, non-small cell lung cancer (NSCLC) and esophageal squamous cell carcinoma. These four product candidates resulted from Sutro’s XpressCF® and XpressCF+™ technology platforms. Bristol Myers Squibb and EMD Serono have worldwide development and commercialization

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Exhibit 99.1

rights for CC-99712 and M1231, respectively, for which Sutro is entitled to milestone or contingent payments and tiered royalties.

Sutro is dedicated to transforming the lives of cancer patients by creating medicines with improved therapeutic profiles for areas of unmet need. To date, Sutro’s platform has led to ADCs, bispecific antibodies, cytokine-based immuno-oncology therapies, and vaccines directed at precedented targets in clinical indications where the current standard of care is suboptimal.

Sutro’s platform allows it to accelerate discovery and development of potential first-in-class and best-in-class molecules through rapid and systematic evaluation of protein structure-activity relationships to create optimized homogeneous product candidates. In addition to developing its own oncology pipeline, Sutro is collaborating with select pharmaceutical and biotechnology companies to discover and develop novel, next-generation therapeutics.

Follow Sutro on Twitter, @Sutrobio, and at www.sutrobio.com to learn more about our passion for changing the future of oncology.

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 clinical results, potential benefits of STRO-002 and the Company’s other product candidates and platform, potential future milestone and royalty payments, and potential market opportunities for STRO-002 and the Company’s other product candidates. 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 and the Company’s ability to successfully leverage Fast Track designation, the market size for the Company’s product candidates to be smaller than anticipated, the impact of the COVID-19 pandemic on the Company’s business, clinical trial sites, supply chain and manufacturing facilities, the Company’s ability to 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 value of the Company’s holdings of Vaxcyte common stock, 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

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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

Annie J. Chang

Sutro Biopharma

(650) 801-5728

[email protected]

Media Contact

Maggie Beller

Russo Partners

(646) 942-5631

[email protected]

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NON-CONFIDENTIAL 2022 KOL Discussion of STRO-002 Phase 1 Interim Dose Expansion Data January 5, 20225:00pm ET / 2:00pm PT Sutro Biopharma “NASDAQ: STRO Exhibit 99.2

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, current and future clinical activities, timing and success of our ongoing and planned clinical trials and related data, updates and results of our clinical trials and related data, timing and success of our planned development activities, our ability to obtain and maintain regulatory approval, the potential therapeutic benefits and economic value of our product candidates, potential growth opportunities, financing plans, competitive position, industry environment and potential market opportunities. 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 and timing of potential regulatory submissions, designations, approvals and commercialization of product candidates, the timing and results of preclinical and clinical trials, and the expected impact of the COVID-19 pandemic on our operations. 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.

Agenda for Today Topic Speakers Opening Comments Welcome & Agenda Review Forward-Looking Statements Ed Albini, Chief Financial Officer CEO Opening Comments Study Objectives and Overview Bill Newell, Chief Executive Officer Data Presentation Study Objectives and Overview STRO-002 Phase 1 Dose Expansion Interim Data R. Wendel Naumann, M.D., Professor & Director of Gynecologic Oncology Research, Associate Medical Director of Clinical Trials, at Levine Cancer Institute, Atrium Health Arturo Molina, M.D., MS, FACP, Chief Medical Officer Summary Next Steps for STRO-002 Arturo Molina, M.D., MS, FACP Closing Bill Newell Q&A R. Wendel Naumann, M.D. Bill Newell Arturo Molina, M.D., MS, FACP Trevor Hallam, Ph.D., President of Research and Chief Scientific Officer Ed Albini Today’s Agenda January 5, 2022

Agenda for Today Welcome Dr. R. Wendel Naumann Phase 1 STRO-002-GM1 Co-Principal Investigator Dr. Naumann is currently the Director of Minimally Invasive Surgery in Gynecologic Oncology and Professor in the Department of Ob/Gyn at the Levine Cancer Institute, Atrium Health. Dr. Naumann did his residency in Obstetrics and Gynecology as well as his fellowship in Gynecologic Oncology at the University of Alabama School of Medicine in Birmingham. Dr. Naumann has served as a board member on the Executive Council of the Society of Gynecologic Oncology (SGO) and the Chair of Education Committee and is currently the co-director of the SGO Winter meeting. He has an interest in chemotherapy development including targeted therapies and immune therapies and runs the phase I trials in gynecologic oncology at the Levine Cancer Institute. He has served as a member of the GOG/NRG corpus committee and the Developmental Therapeutics committee. R. Wendel Naumann, M.D. Professor & Director of Gynecologic Oncology Research Associate Medical Director of Clinical Trials,Levine Cancer Institute, Atrium Health Sutro Biopharma Clinical Advisory Board

5 Dose Expansion STRO 002 Patient Characteristics in Dose Expansion Cohort Interim data for dose expansion are as of November 8, 2021 Patients Randomized & Dosed Safety Evaluable (as of Nov 8, 2021) N=43 RECIST v1.1 Evaluable One Post-Baseline Scan N=33 Not Yet Evaluable No Post Baseline Scan N=8 Discontinued Prior to Receiving Scan N=2 Tumor Proportion Score (TPS) > 25% N=25 TPS ≤ 25% N=8 Total Patients Enrolled N=44 Not dosed by Nov. 8 N=1 Randomized Dose Levels Total N=43 Ovarian Cancer Patients 4.3 mg/kg N=23 5.2 mg/kg N=20 Total N=43 Median age, years (range) 63 (39–91) 56 (40–72) 60 (39–91) Median time since diagnosis, years (range) 1.8 (0.9–4.4) 2.9 (0.7–5.1) 2.8 (0.7–5.1) Number of prior lines of therapy Median 3.0 2.0 2.0 Mean (St. Dev.) 2.5 (0.95) 2.5 (1.05) 2.5 (0.98) Previous Therapies, n (%) bevacizumab 13 (57%) 14 (70%) 27 (63%) PARP Inhibitor 15 (65%) 13 (65%) 28 (65%) Patient Status as of November 8, 2021 Patient Baseline Characteristics

6 20% -30% 2 pts had 0% Δ Maximum Change in Tumor Target Lesions (N=33) Partial Response 4.3 mg/kg 5.2 mg/kg Treatment ongoingas of Nov 8, 2021 PR confirmed by next scheduled scan (after Nov. 8, 2021) Dose Expansion STRO 002 Dose Response Demonstrated Interim data suggest that 5.2 mg/kg starting dose leads to higher response rates PRu* PRu PRu* PR PR PR PR PRu* PRu* PR PR PR Starting Dose, Q3W Note: Data as of Nov. 8, 2021. 5 PRu were of interest and followed up subsequent to the data cutoff date. 4 PR confirmed at their next scheduled scan and 1 was SD. *

Starting Dose Best Overall Response (BOR) 4.3 mg/kg 5.2 mg/kg All Comers Evaluable patients N=16 N=17 N=33 PR 3 4 7 PR confirmed by next scheduled scan post Nov. 8, 2021 0 4 4 Total PR 3 8 11 ORR (%) 18.8% 47.1% 33.3% SD 10 4 14 PD 3 5 8 7 Dose Expansion STRO 002 Objective Response by RECIST v1.1 33% ORR rate in all 33 evaluable patients, unenriched for FolRα expression 47.1% ORR in patients starting at the 5.2 mg/kg dose level 33.3% ORR in all patients Interim data suggests that 5.2 mg/kg starting dose leads to higher response rates All 4 patients with PRu treated at 5.2 mg/kg were subsequently confirmed at the next scheduled scan Note: Data as of Nov. 8, 2021. 5 PRu were of interest and followed up subsequent to the data cutoff date. 4 PR confirmed at their next scheduled scan and 1 was SD.

Dose Expansion STRO 002 Robust Anti-tumor Activity and Disease Control Demonstrated Responders experienced rapid tumor reduction or a steady deepening of response Change from baseline (%) Weeks since first treatment 20 -30 -100 0 Change in Sum of Diameters for Target Lesions Over Time (N=33) Starting Dose, Q3W 4.3 mg/kg 5.2 mg/kg Treatment ongoingas of Nov 8, 2021 Note: Data as of Nov. 8, 2021.

Encouraging Response Rates and Preliminary Data on Durability Interim data suggests initiating with 5.2 mg/kg followed by a dose adjustment Treatment Duration on Patients with at Least One Dose (N=43) Dose Expansion STRO 002 Median Duration of Response has not been reached and 23 patients remain on study Data to inform RP2D with final decision pending more data maturity + Weeks since first treatment Individual patients treated with STRO-002 Dose Level, Q3W 3.5 mg/kg 4.3 mg/kg 5.2 mg/kg + + + + Treatment ongoing as of Nov 8, 2021 (N=23) Dose adjustment PR No post-baseline scan as of data cut-off + + + Note: Data as of Nov. 8, 2021. + + +

Platinum-Resistant Ovarian Cancer Patient Treated at 4.3 mg/kg Dose Level Ongoing Partial Response with 72% reduction in tumor burden Dose Expansion STRO 002 Initial diagnosis: Stage IV ovarian cancer, Jan 2020 3 Prior Regimens: Resistant to 1st Neoadjuvant / adjuvant Carbo / Taxol / Taxotere Refractory to 2nd and 3rd with progressive disease Liposomal doxorubicin Gemcitabine Lateral Abdominal Wall Axillary Lymph Node Inter-aortocaval LN External Iliac LN Baseline Screening of Target Lesions – May 17, 2021 Scans at Cycle 5 Target Lesions – September 8, 2021 Lateral Abdominal Wall Axillary Lymph Node Inter-aortocaval LN External Iliac LN

11 TPS > 25% suggests ~70% of the patient population may benefit from STRO-002 ORR by TPS Expression Levels (Total Samples N=33) Dose Expansion STRO 002 TPS Overall TPS ≤ 25% TPS > 25% TPS > 50% TPS> 75% ORR 33.3% 12.5% 40.0% 42.1% 43.8% Number of patient samples N=33 N=8 N=25 N=19 N=16 PR(1) 11 1 10 8 7 Potential Market Size (%) 100% ~ 30% ~ 70% (1) PR classification includes the 4 of 5 patients who were confirmed by their next scheduled scan after Nov. 8, 2021. Note: Data as of Nov. 8, 2021. TPS Identified as Scoring Algorithm Appropriate for STRO-002 Exploratory analysis suggests TPS > 25% correlated with higher response Tumor Proportion Score (TPS) Percent of tumor cells showing staining of any intensity Does not require analysis of intensity levels and easy to score Commonly used in clinical practice Established reproducibility across different biomarkers (e.g., PD-L1)

Emerging Safety Profile is Manageable and Consistent with Prior Studies No new safety signals were observed, including the absence of keratopathy 4.3 mg/Kg (N=23) 5.2 mg/Kg (N=20) Total (N=43) Grade 3 n (%) Grade 4 n (%) Grade 5 n (%) Grade 3 n (%) Grade 4 n (%) Grade 5 n (%) Grade 3 n (%) Grade 4 n (%) Grade 5 n (%) Subjects reporting at least 1 event 13 (57) 4 (17) 0 8 (40) 8 (40) 1 (5) 21 (48) 12 (28) 1 (2) Neutropenia (1) 10 (44) 4 (17) 0 6 (30) 8 (40) 1 (5) 16 (37) 12 (28) 1 (2) Febrile Neutropenia 1 (2) 0 0 0 0 1 (5) 1 (2) 0 1 (2) White blood cell count decreased 4 (17) 1 (4) 0 1 (5) 2 (10) 0 5 (12) 3 (7) 0 Anemia 1 (4) 0 0 3 (15) 0 0 4 (9) 0 0 Arthralgia 4 (17) 0 0 0 0 0 4 (9) 0 0 Diarrhea 2 (9) 0 0 0 1 (5) 0 2 (5) 1 (2) 0 Platelet count decreased 2 (9) 0 0 1 (5) 0 0 3 (7) 0 0 Thrombocytopenia 0 0 0 2 (10) 0 0 2 (8) 0 0 Vomiting 0 0 0 2 (10) 0 0 2 (8) 0 0 Fatigue 2 (9) 0 0 0 0 0 2 (8) 0 0 Activated partial thromboplastin time prolonged 2 (9) 0 0 0 0 0 2 (8) 0 0 Hyponatremia 2 (9) 0 0 0 0 0 2 (8) 0 0 Neuralgia 2 (9) 0 0 0 0 0 2 (8) 0 0 Acute kidney injury 0 0 0 2 (10) 0 0 2 (8) 0 0 Neutropenia included the following preferred terms: neutropenia, febrile neutropenia, and neutrophil count decreased. Note: Data as of Nov. 8, 2021. 12 Dose Expansion STRO 002 Most Common G3+ TEAEs (≥2 Subjects) by Dose Neutropenia was the leading TEAE, resulting in treatment delay or dose reduction Neutropenia resolved with 1 week delay ± G-CSF, in the majority of cases Febrile neutropenia is rare One Grade 5 event at the 5.2 mg/kg dose cohort One Grade 3 event at the 4.3 mg/kg dose cohort Protocol was updated to require dose reduction for Grade 4 neutropenia Dose reductions ameliorated neutropenia

13 Dose Expansion STRO 002 Dose Expansion Data Provide Initial Insights on Go-Forward Strategy Emerging data show dose response and a path for potential enrichment strategy Total of 11 confirmed PR (1) out of 33 RECIST v1.1 evaluable patients 33% ORR, across all FolRα expression levels and both dose levels Dose response was demonstrated 47% ORR (8/17)(1) in unenriched patients starting at the 5.2 mg/kg dose level Initial data suggests responses at 5.2 mg/kg are maintained, even when subsequent dose reductions are implemented Using TPS, interim data suggests > 25% expression levels are correlated with higher clinically meaningful response rate, with 40% ORR (10/25)(1) observed in both dose levels and an enriched patient population Based on our patient observations, we believe STRO-002 may be an appropriate therapy for ~70% of these patients No new safety signals were observed, including the absence of keratopathy Neutropenia was the leading TEAE, resulting in treatment delay or dose reduction Protocol was updated to require dose reduction for Grade 4 neutropenia Overall Efficacy Dose Response Biomarker Safety (1) PR classification includes the 4 of 5 patients who were confirmed by their next scheduled scan after Nov. 8, 2021. Note: Data as of Nov. 8, 2021.

Dose-escalation cohort 39 patients, enrollment completed August 2020 Dose-expansion cohort44 patients enrolled in US and Spain sites, enrollment completed November 2021 Combo study with bevacizumab Trial is open and enrolling patients FPI planned for early 2022 Registration-directed trial Pending FDA EOP1 meeting Precedent from single-arm registration-directed trial in advanced ovarian cancer Ovarian Cancer Other Solid Tumors Endometrial cancer cohort Initial enrollment planned for ~15 patients FPI December 2021 Cohort is open and enrolling patients NSCLC and Other Tumors Potential for a basket study design with other FolRα expressing cancers Nonclinical work ongoing 14 STRO 002 Expanding the STRO-002 Franchise Additional clinical studies in ovarian & endometrial, and nonclinical work on other tumor types

NON-CONFIDENTIAL 2022 KOL Discussion of STRO-002 Phase 1 Interim Dose Expansion Data Q&A Session January 5, 20225:00pm ET / 2:00pm PT