UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2021 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from ________ to ________ Commission File Number: 001-38662 SUTRO BIOPHARMA, INC. (Exact Name of Registrant as Specified in its Charter) (State or other jurisd ...

Financial Performance - The company reported a net loss of $36.5 million for the six months ended June 30, 2021, with an accumulated deficit of $264.4 million as of the same date [138]. - The company reported a net loss of $6.2 million for the three months ended June 30, 2021, compared to a net income of $29.9 million in the same period in 2020, representing a decrease of $36.0 million [155]. - The company reported a net cash decrease of $149.8 million for the six months ended June 30, 2021 [192]. - Cash used in operating activities for the six months ended June 30, 2021, was $35.7 million, reflecting a net loss of $36.5 million [193]. - Cash provided by financing activities for the six months ended June 30, 2021, was $1.8 million, primarily from $1.4 million of proceeds from common stock options [197]. - Cash provided by financing activities for the six months ended June 30, 2020, was $107.1 million, mainly from $91.4 million of net proceeds from a public offering [198]. Revenue and Collaborations - The company has no products approved for commercial sale and has not generated any revenue from commercial product sales [140]. - The company derives revenue primarily from collaboration agreements, with no revenue from commercial product sales to date [141]. - Total revenue increased by $18.6 million, or 196%, during the three months ended June 30, 2021, compared to the same period in 2020, reaching $28.0 million [155]. - Total revenue increased by $26.1 million, or 157%, during the six months ended June 30, 2021, compared to the same period in 2020, driven by a $22.0 million increase from Merck [169]. - Revenue from Merck Sharp & Dohme Corporation increased by $12.9 million, or 184%, during the three months ended June 30, 2021, totaling $19.9 million [156]. - The company earned a $15.0 million contingent payment from Merck in Q2 2021 for initiating an IND enabling toxicology study [177]. - The company has entered into collaborations with Merck, Celgene (BMS), and EMD Serono to develop multi-target product candidates [131]. Expenses - Research and development expenses for the three months ended June 30, 2021, were $25.3 million, an increase of $8.1 million or 47% compared to $17.2 million in the same period in 2020 [160]. - Total operating expenses for the six months ended June 30, 2021, were $71.5 million, an increase of $19.3 million or 37% compared to $52.2 million in the same period in 2020 [166]. - Research and development expense rose by $13.0 million, or 37%, during the six months ended June 30, 2021, primarily due to higher personnel-related expenses and clinical trial costs [171]. - General and administrative expenses rose to $12.5 million for the three months ended June 30, 2021, reflecting an increase of $3.9 million or 45% compared to $8.6 million in the same period in 2020 [161]. - General and administrative expense increased by $6.3 million, or 36%, during the six months ended June 30, 2021, mainly due to higher personnel-related expenses and facility-related costs [172]. - The company expects significant increases in operating expenses as it continues to develop product candidates and seek regulatory approvals [138]. - The company expects research and development expenses to increase in the future as it advances product candidates through clinical trials and expands its pipeline [146]. Clinical Trials - The Phase 1 trial for STRO-001 has enrolled patients and is ongoing, with no ocular toxicity signals observed and the maximum tolerated dose not yet reached [132]. - As of April 23, 2021, the Phase 1 trial for STRO-002 had enrolled 39 ovarian cancer patients, with 31 patients evaluable for RECIST responses [133]. - In the STRO-002 trial, 10 out of 31 evaluable patients met criteria for response, including 1 complete response and 9 partial responses [136]. - The median duration of response for confirmed responders in the STRO-002 trial was 5.8 months, with a median progression-free survival of 7.2 months [136]. - The COVID-19 pandemic has caused minor delays in clinical trial enrollment but overall patient treatment remains on track [139]. Cash and Securities - As of June 30, 2021, the company had cash, cash equivalents, and marketable securities totaling $283.4 million, with an outstanding debt of $24.8 million [176]. - As of June 30, 2021, the company had cash, cash equivalents, and marketable securities totaling $283.4 million, down from $326.5 million as of December 31, 2020 [208]. - The company held equity securities valued at $35.3 million as of June 30, 2021, consisting solely of common stock of Vaxcyte [208]. - A hypothetical 10% decrease in the market price of equity investments as of June 30, 2021, would decrease the fair value by $3.5 million [209]. - The company had $24.8 million in debt outstanding as of June 30, 2021, with a floating interest rate that could be as high as 8.07% [211]. - The debt matures on March 1, 2024, and will be interest-only through March 1, 2022 [211]. Future Outlook - The company anticipates needing additional financing to advance its product candidates and fund operations in the foreseeable future [190]. - The company is classified as an emerging growth company and expects to cease this status by December 31, 2021 [202]. - The company has not entered into any off-balance sheet arrangements [199]. - There have been no material changes to critical accounting policies since the last annual report [204].

| --- | --- | --- | --- | |-------|-------|-------|-------| | | | | | | | | | | 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 ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2021 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from ________ to ________ Commission File Number: 001-38662 SUTRO BIOPHARMA, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 47-0926186 (State ...

Company Strategy & Technology - Sutro Biopharma is expanding cell-free technology beyond ADCs, building strategic partnerships, and creating new modalities for extended value creation[8] - The company utilizes an industry-leading cell-free protein synthesis platform with GMP production yields consistent and scalable end-products[12] - Sutro's cell-free synthesis platform allows for the creation of hundreds of protein variants in weeks, enabling empirical selection of the best lead candidate[18] STRO-002 Program (Ovarian and Endometrial Cancers) - STRO-002 is a FolRα-targeting ADC with a DAR of 4, designed with a potentially dual mechanism of action[28] - In a Phase 1 dose-escalation study, 34 patients were treated at clinically active doses (≥ 2.9 mg/kg Q3W) of STRO-002[30] - In the RECIST-evaluable population (N=31), 10 patients met the criteria for response, with an objective response rate of 20%[36] - Clinical benefit was observed in a heavily pre-treated patient population, with a disease control rate of 74% at 12 weeks in the RECIST-evaluable population[43] STRO-001 Program (Lymphomas and Multiple Myeloma) - STRO-001 is a CD74-targeting ADC with a DAR of 2, designed to minimize bystander effects in hematological cancers[57] - In the NHL cohort, a total of 21 patients have been treated with STRO-001, and 18 patients were evaluable for response as of October 30, 2020[62] - Interim data showed partial responses in two DLBCL patients who had progressed on CAR-T therapy[67] Financial Status - The company reported $326.5 million in cash, cash equivalents, and marketable securities as of year-end 2020[73] - The projected cash runway extends into 2H 2023, not including potential monetization of Vaxcyte shares or future business development[73] - Sutro Biopharma has received approximately $398 million in funding from collaborators through year-end 2020[73]

| --- | --- | |-------|-------| | | | | | | 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 f ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2020 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 001-38662 SUTRO BIOPHARMA, INC. (Exact Name of Registrant as Specified in Its Charter) Delaware 47-0926186 (State or other jurisdiction o ...

| --- | --- | |-------|-------| | | | | | | 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 and preclini ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2020 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from ________ to ________ Commission File Number: 001-38662 SUTRO BIOPHARMA, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 47-0926186 (S ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2020 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from ________ to ________ Commission File Number: 001-38662 SUTRO BIOPHARMA, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 47-0926186 (State ...