Exhibit 99.1

Sutro Biopharma Reports Full Year 2020 Financial Results

and Provides Business Highlights and 2021 Anticipated Milestones

- Year-end 2020 cash, cash equivalents and marketable securities of $326.5 million, with projected runway into the second half of 2023

- Four antibody-drug conjugate programs are now in the clinic that were discovered through Sutro’s proprietary and integrated cell-free protein synthesis platform

- Advancement of partner EMD Serono’s novel bispecific MUC1-EGFR ADC, M1231, into the clinic

-  Dosing of initial patients in dose-expansion of the Phase 1 STRO-002 study initiated January 2021

- STRO-002 data presented at Company-hosted KOL event and STRO-001 data presented at ASH in December 2020

SOUTH SAN FRANCISCO, Calif., March 18, 2021 – Sutro Biopharma, Inc. (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 reported its financial results for the year ended December 31, 2020, its recent business highlights, and provided a preview of anticipated selected milestones in 2021.

“2020 was a highly productive year for Sutro as we advanced the clinical development of our programs and navigated through the pandemic. Four product candidates that have now entered the clinic, two of which are partnered programs, were discovered and developed using our cell-free protein synthesis platform, showcasing its strength and versatility,” said Bill Newell, Sutro’s Chief Executive Officer. “We were particularly encouraged to see meaningful clinical benefit for women with advanced platinum-resistant and refractory ovarian cancer who were part of the Phase 1 dose-escalation study for STRO-002, our FolRα-targeted ADC. We dosed the first patient in dose-expansion in January 2021 and are rapidly moving this program forward. Additionally, we are progressing well on our partnerships – our Bristol Myers Squibb and EMD Serono collaboration programs are enrolling patients in Phase 1 studies and we are continuing to work with Merck on the cytokine derivatives collaboration to bring its first program to the clinic. We look forward to continued progress on our clinical programs and utilizing our industry leading cell-free platform to advance additional product candidates to benefit patients with unmet medical needs.”  

Recent Business Highlights and Expected 2021 Milestones

STRO-002: Continued progress in Phase 1 trial of STRO-002, folate receptor-alpha (FolRα)-targeted antibody-drug conjugate (ADC) for patients with recurrent platinum resistant or refractory ovarian cancer.

STRO-001: Phase 1 dose-escalation continues for STRO-001, a CD74-targeted ADC for development in B-cell malignancies.

Merck collaboration: Working collaboratively with Merck to advance two cytokine derivative programs towards the clinic.

Bristol Myers Squibb (BMS) collaboration: Phase 1 trial for CC-99712, a BCMA-targeted ADC, is continuing to enroll multiple myeloma patients.

Merck KGaA, EMD Serono (EMD Serono) collaboration: Phase 1 trial for M1231, a first-in-class bispecific ADC targeting MUC1‑EGFR for development in solid tumors, was initiated in the first quarter of 2021.

Vaxcyte relationship: Potential vaccine application demonstrates the power of Sutro’s cell-free technology in conjugated vaccines.

Key 2020 financings

Full Year 2020 Financial Highlights

Cash, Cash Equivalents and Marketable Securities

As of December 31, 2020, Sutro had cash, cash equivalents and marketable securities of $326.5 million, as compared to $133.5 million as of December 31, 2019, which represents a net cash increase of $193.0 million during 2020. The cash, cash equivalents and marketable securities balance noted above does not include the value associated with Sutro’s holdings of approximately 1.6 million shares of Vaxcyte common stock. As of December 31, 2020, the fair value of the Vaxcyte common stock held by Sutro was $41.6 million.

Unrealized Gain from Increase in Value of Vaxcyte Common Stock

The non-operating, unrealized gain of $41.5 million in 2020 consisted of $41.6 million due to the increase in the estimated fair value of Sutro’s holdings of approximately 1.6 million shares of Vaxcyte common stock, partially offset by approximately $0.1 million in adjustments related to revaluations of certain Vaxcyte equity items. Vaxcyte common stock held by Sutro will be measured at fair value based on the closing price of Vaxcyte’s common stock on the last trading day of each reporting period, with any non-operating, unrealized gains and losses recorded in Sutro’s statements of operations.

Revenue

Revenue was $42.7 million in each of the year ended December 31, 2020 and the year ended December 31, 2019, related principally to the Merck, BMS, and EMD Serono collaborations. Future collaboration revenue from Merck, BMS, and EMD Serono, and from any future collaboration partners, will fluctuate as a result of the amount and timing of revenue recognition of upfront, milestones and other collaboration agreement payments.  

Operating Expenses

Total operating expenses for the year ended December 31, 2020 were $113.8 million, as compared to $98.2 million in 2019, including non-cash stock-based compensation of $11.9 million and $10.3 million, and depreciation and amortization expense of $4.3 million and $4.8 million, in 2020 and 2019, respectively. Total operating expenses for 2020 were comprised of research and development expenses of $77.0 million and general and administrative expenses of $36.8 million, which are expected to increase in future periods as Sutro’s internal product candidates advance in clinical development and additional general and administrative expenses are incurred as a public company.

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 being investigated in a Phase 1 clinical trial of patients with advanced B-cell malignancies, including multiple myeloma and non-Hodgkin lymphoma. STRO-001 was granted Orphan Drug Designation by the FDA for multiple myeloma in October 2018. STRO-002 is a folate receptor alpha (FolRα)-targeting ADC, currently being investigated in a Phase 1 clinical trial of patients with ovarian and endometrial cancers. A third product candidate, CC-99712 (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 for multiple myeloma. A fourth product candidate, M1231, (MUC1-EGFR, first-in-class bispecific ADC), which is part of Sutro’s collaboration with Merck KGaA, EMD Serono (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.  The four product candidates above being evaluated in clinical trials resulted from Sutro’s XpressCF^® and XpressCF+™ technology platforms. Bristol Myers Squibb and EMD Serono have worldwide development and commercialization 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 cytokine-based immuno-oncology therapies, ADCs, vaccines and bispecific antibodies directed at precedented targets in clinical indications where the current standard of care is suboptimal.

The 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 biotech companies to discover and develop novel, next-generation therapeutics. As the pace of clinical development accelerates, Sutro and its partners are developing therapeutics designed to more efficiently kill tumors without harming healthy cells.

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 the company’s product candidates and platform and potential market opportunities for the company’s 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, 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 release, and the company undertakes no obligation to revise or update any forward-looking statements to reflect events or circumstances after the date hereof.

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Investor Contact

Annie J. Chang

Sutro Biopharma

(650) 801-5728

ajchang@sutrobio.com

Media Contact

David Schull

Russo Partners

(212) 845-4271

david.schull@russopartnersllc.com

Sutro Biopharma, Inc.

Selected Statements of Operations Financial Data

(Unaudited)

(In thousands, except share and per share amounts)

Sutro Biopharma, Inc.

Selected Balance Sheet Financial Data

(Unaudited)

(In thousands)