PART I. FINANCIAL INFORMATION [Financial Statements (Unaudited)](index=2&type=section&id=Item%201.%20Financial%20Statements%20(Unaudited)) The company's interim financials show increased assets and liabilities due to a royalty sale, alongside a wider net loss [Condensed Balance Sheets](index=3&type=section&id=Condensed%20Balance%20Sheets) Total assets grew to $464.9 million while liabilities rose to $310.2 million, driven by a new deferred royalty obligation Condensed Balance Sheet Highlights (in thousands) | Account | June 30, 2023 | December 31, 2022 | | :--- | :--- | :--- | | **Assets** | | | | Cash and cash equivalents | $235,095 | $47,254 | | Marketable securities | $123,198 | $255,090 | | Total current assets | $411,985 | $353,153 | | Total assets | $464,899 | $406,944 | | **Liabilities & Stockholders' Equity** | | | | Total current liabilities | $67,125 | $66,547 | | Deferred royalty obligation | $136,653 | $0 | | Total liabilities | $310,184 | $189,896 | | Total stockholders' equity | $154,715 | $217,048 | [Condensed Statements of Operations](index=4&type=section&id=Condensed%20Statements%20of%20Operations) Revenues decreased while R&D expenses increased, resulting in a higher net loss of $88.6 million for the first half of 2023 Statement of Operations Summary (in thousands, except per share data) | Metric | Q2 2023 | Q2 2022 | 6 Months 2023 | 6 Months 2022 | | :--- | :--- | :--- | :--- | :--- | | Revenues | $10,412 | $28,096 | $23,086 | $33,993 | | Research and development | $41,592 | $32,332 | $80,991 | $62,322 | | General and administrative | $14,999 | $15,143 | $30,511 | $30,182 | | Loss from operations | ($46,179) | ($19,379) | ($88,416) | ($58,511) | | Net loss | ($38,524) | ($26,012) | ($88,574) | ($65,122) | | Net loss per share | ($0.64) | ($0.55) | ($1.49) | ($1.39) | [Condensed Statements of Comprehensive Loss](index=5&type=section&id=Condensed%20Statements%20of%20Comprehensive%20Loss) The company reported a comprehensive loss of $87.9 million for the first six months of 2023, including the net loss and unrealized gains Comprehensive Loss Summary (in thousands) | Metric | 6 Months 2023 | 6 Months 2022 | | :--- | :--- | :--- | | Net loss | $(88,574) | $(65,122) | | Net unrealized income (loss) on securities | $634 | $(1,042) | | **Comprehensive loss** | **$(87,940)** | **$(66,164)** | [Condensed Statements of Stockholders' Equity](index=6&type=section&id=Condensed%20Statements%20of%20Stockholders%27%20Equity) Stockholders' equity decreased to $154.7 million by June 30, 2023, primarily due to the period's net loss - Stockholders' equity declined to **$154.7 million** at June 30, 2023, from **$217.0 million** at the end of 2022, mainly due to the net loss incurred during the first half of the year[16](index=16&type=chunk) - During the first six months of 2023, the company issued 1,857,410 shares through its At-The-Market (ATM) facility, raising net proceeds of approximately **$12.0 million**[16](index=16&type=chunk)[22](index=22&type=chunk)[23](index=23&type=chunk) [Condensed Statements of Cash Flows](index=7&type=section&id=Condensed%20Statements%20of%20Cash%20Flows) Financing activities, led by a $139.7 million royalty sale, drove a net cash increase despite negative operating cash flow Cash Flow Summary (in thousands) | Activity | 6 Months 2023 | 6 Months 2022 | | :--- | :--- | :--- | | Net cash used in operating activities | $(92,186) | $(38,441) | | Net cash provided by investing activities | $133,608 | $80,897 | | Net cash provided by financing activities | $146,419 | $6,245 | | **Net increase in cash** | **$187,841** | **$48,701** | - The primary source of financing cash flow was **$139.7 million** in net proceeds from the sale of future royalties to Blackstone[19](index=19&type=chunk) [Notes to Unaudited Interim Condensed Financial Statements](index=8&type=section&id=Notes%20to%20Unaudited%20Interim%20Condensed%20Financial%20Statements) Key notes detail a $140.0 million royalty sale to Blackstone, revenue shifts between collaborators, and the termination of the BMS deal - In June 2023, the company sold its 4% royalty interest in future net sales of Vaxcyte products to Blackstone for an upfront payment of **$140.0 million**, recorded as a deferred royalty obligation[31](index=31&type=chunk)[108](index=108&type=chunk)[109](index=109&type=chunk) - The company believes its unrestricted cash, cash equivalents, and marketable securities of **$358.3 million** as of June 30, 2023, will fund operations for at least the next 12 months[25](index=25&type=chunk)[26](index=26&type=chunk) - BMS provided a notice of termination for the development of CC-99712, effective October 7, 2023, after which Sutro will regain sole worldwide rights[67](index=67&type=chunk) Revenue by Collaborator (Six Months Ended June 30, in thousands) | Collaborator | 2023 | 2022 | | :--- | :--- | :--- | | Astellas Pharma Inc. | $13,605 | $0 | | Bristol Myers Squibb (BMS) | $5,402 | $4,431 | | Merck Sharp & Dohme (Merck) | $2,693 | $1,210 | | Tasly Biopharmaceuticals | $0 | $25,000 | | EMD Serono | $8 | $2,034 | | Vaxcyte | $1,378 | $1,318 | | **Total Revenue** | **$23,086** | **$33,993** | [Management's Discussion and Analysis of Financial Condition and Results of Operations](index=26&type=section&id=Item%202.%20Management%27s%20Discussion%20and%20Analysis%20of%20Financial%20Condition%20and%20Results%20of%20Operations) Management discusses its ADC pipeline focus, decreased revenue, increased R&D costs, and improved liquidity from a royalty sale [Overview](index=26&type=section&id=Overview) Sutro Biopharma is advancing its lead ADC candidate, luvelta, into a registration-directed trial for ovarian cancer - The company's most advanced product candidate, luvelta, has entered a registration-directed Phase 2/3 trial (REFRaME) for patients with platinum-resistant ovarian cancer, with the first patient enrolled in July 2023[135](index=135&type=chunk)[138](index=138&type=chunk) - The company's second candidate, STRO-001, has completed dose escalation in its Phase 1 trial, with future development decisions to be informed by data from BioNova's trial in Greater China[140](index=140&type=chunk)[141](index=141&type=chunk) - In June 2023, Sutro entered into an agreement with Blackstone, selling its **4% revenue interest** in Vaxcyte's future products for a significant upfront payment[143](index=143&type=chunk) [Results of Operations](index=31&type=section&id=Results%20of%20Operations) Revenue for the first half of 2023 fell 32% due to a non-recurring prior-year payment, while R&D expenses rose 30% Comparison of Six Months Ended June 30, 2023 and 2022 (in thousands) | Metric | 6 Months 2023 | 6 Months 2022 | Change | Change (%) | | :--- | :--- | :--- | :--- | :--- | | Revenues | $23,086 | $33,993 | $(10,907) | (32)% | | Research and development | $80,991 | $62,322 | $18,669 | 30% | | General and administrative | $30,511 | $30,182 | $329 | 1% | | Loss from operations | $(88,416) | $(58,511) | $(29,905) | 51% | | Net loss | $(88,574) | $(65,122) | $(23,452) | 36% | - The decrease in revenue was primarily due to a **$25.0 million** upfront payment from Tasly recognized in 2022, partially offset by **$13.6 million** in new revenue from the Astellas collaboration[172](index=172&type=chunk) - The **30% increase in R&D expenses** was mainly due to an **$8.9 million** increase in personnel-related costs and a **$5.7 million** increase in lab and clinical development expenses[173](index=173&type=chunk) [Liquidity and Capital Resources](index=34&type=section&id=Liquidity%20and%20Capital%20Resources) The company's capital of $358.3 million, bolstered by a $140.0 million royalty sale, is sufficient for the next twelve months - In June 2023, the company received a **$140.0 million** upfront payment from Blackstone for the sale of its 4% royalty interest in potential future net sales of Vaxcyte products[181](index=181&type=chunk)[182](index=182&type=chunk) - During the six months ended June 30, 2023, the company raised net proceeds of approximately **$12.0 million** from the sale of common stock through its At-the-Market (ATM) facility[183](index=183&type=chunk) - The company believes its existing capital resources are sufficient to fund operating expenses and capital expenditure requirements for **at least the next twelve months** from the filing date[194](index=194&type=chunk) [Critical Accounting Policies and Estimates](index=37&type=section&id=Critical%20Accounting%20Policies%20and%20Estimates) A new policy was adopted to account for the deferred royalty obligation from the Blackstone transaction as imputed debt - A new critical accounting policy was established for the deferred royalty obligation related to the sale of future Vaxcyte royalties to Blackstone[208](index=208&type=chunk) - The proceeds from the Blackstone transaction are recorded as a liability and will be amortized to interest expense using the effective interest rate method based on estimated future royalties[208](index=208&type=chunk) [Quantitative and Qualitative Disclosures About Market Risk](index=39&type=section&id=Item%203.%20Quantitative%20and%20Qualitative%20Disclosures%20About%20Market%20Risk) The company is primarily exposed to equity price risk from its Vaxcyte stock holdings and minor interest rate risk - The company is exposed to equity price risk from its holdings of Vaxcyte common stock, valued at **$33.3 million** as of June 30, 2023, where a 10% price decrease would result in a $3.3 million loss in fair value[212](index=212&type=chunk)[213](index=213&type=chunk) - The company's debt of **$10.2 million** bears a floating interest rate, but management states that a 100 basis point change in rates would not have a material impact on interest expense[215](index=215&type=chunk) [Controls and Procedures](index=40&type=section&id=Item%204.%20Controls%20and%20Procedures) Management concluded that disclosure controls and procedures were effective, with no material changes to internal controls - Management concluded that the company's disclosure controls and procedures were **effective** as of June 30, 2023[218](index=218&type=chunk) - **No material changes** to the company's internal control over financial reporting occurred during the quarter ended June 30, 2023[219](index=219&type=chunk) PART II. OTHER INFORMATION [Legal Proceedings](index=41&type=section&id=Item%201.%20Legal%20Proceedings) The company is not currently a party to any material legal proceedings - Sutro Biopharma is not presently a party to any **material legal proceedings**[222](index=222&type=chunk) [Risk Factors](index=41&type=section&id=Item%201A.%20Risk%20Factors) The company faces risks from its history of losses, dependence on early-stage candidates, and reliance on third parties - The company has a history of significant losses (**$541.2 million accumulated deficit**) and will need substantial additional funds to advance its product candidates[225](index=225&type=chunk)[227](index=227&type=chunk) - The business is dependent on the success of its early-stage product candidates, particularly luvelta, which are based on **novel and unproven** XpressCF® and XpressCF+® platforms[225](index=225&type=chunk)[239](index=239&type=chunk) - The company relies on third-party collaborations (like Astellas and Merck) and contract manufacturers, and the failure of these partners could **materially harm the business**[226](index=226&type=chunk)[265](index=265&type=chunk)[283](index=283&type=chunk) [Unregistered Sales of Equity Securities and Use of Proceeds](index=96&type=section&id=Item%202.%20Unregistered%20Sales%20of%20Equity%20Securities%20and%20Use%20of%20Proceeds) There were no unregistered sales of equity securities during the period - None[463](index=463&type=chunk) [Defaults Upon Senior Securities](index=96&type=section&id=Item%203.%20Defaults%20Upon%20Senior%20Securities) There were no defaults upon senior securities during the period - None[463](index=463&type=chunk) [Mine Safety Disclosures](index=96&type=section&id=Item%204.%20Mine%20Safety%20Disclosures) This item is not applicable to the company - Not applicable[464](index=464&type=chunk) [Other Information](index=96&type=section&id=Item%205.%20Other%20Information) There was no other information to report for the period - None[465](index=465&type=chunk) [Exhibits](index=97&type=section&id=Item%206.%20Exhibits) Key exhibits include the Blackstone royalty purchase agreement and an amendment to the Oxford Finance loan agreement - Exhibit 10.1 is the Purchase Agreement with an affiliate of Blackstone Life Sciences, related to the sale of future royalties[467](index=467&type=chunk) - Exhibit 10.2 is the Fifth Amendment to the Loan and Security Agreement with Oxford Finance LLC[467](index=467&type=chunk) [Signatures](index=98&type=section&id=Signatures)

Company Overview 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, design and success ...

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, 2023 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 ...

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, 2022 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 jurisdiction of (I.R.S. Employer i ...

| --- | --- | --- | |---------------------------------------------------------------|-------|-------| | | | | | | | | | | | | | Company Overview November 2022 Sutro Biopharma NASDAQ: STRO | | | Forward-Looking Statements This presentation and the accompanying oral presentation contain "forward-looking" statements that are based on our management's beliefs and assumptions and on information currently available to management. Forward-looking statements include all statements other than statements of historica ...

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, 2022 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 Overview June 2022 Sutro Biopharma NASDAQ: STRO | | | Forward Looking Statements This presentation and the accompanying oral presentation contain "forward-looking" statements that are based on our management's beliefs and assumptions and on information currently available to management. Forward-looking statements include all statements other than statements of historical fact c ...

PART I. FINANCIAL INFORMATION [Financial Statements (Unaudited)](index=3&type=section&id=Item%201.%20Financial%20Statements%20%28Unaudited%29) Sutro Biopharma reported a net loss of **$39.1 million** for Q1 2022, an increase from **$30.4 million** in Q1 2021, due to decreased revenue and higher operating expenses [Condensed Balance Sheets](index=3&type=section&id=Condensed%20Balance%20Sheets) As of March 31, 2022, total assets decreased to **$303.7 million** from **$341.4 million** at year-end 2021, primarily due to reduced marketable securities and stockholders' equity Condensed Balance Sheet Highlights (in thousands) | Account | March 31, 2022 | December 31, 2021 | | :--- | :--- | :--- | | **Assets** | | | | Cash and cash equivalents | $28,901 | $30,414 | | Marketable securities (current & non-current) | $163,199 | $199,118 | | Total current assets | $228,742 | $218,515 | | Total assets | $303,675 | $341,408 | | **Liabilities & Stockholders' Equity** | | | | Total current liabilities | $38,760 | $41,736 | | Total liabilities | $83,303 | $88,844 | | Total stockholders' equity | $220,372 | $252,564 | | Total Liabilities and Stockholders' Equity | $303,675 | $341,408 | [Condensed Statements of Operations](index=4&type=section&id=Condensed%20Statements%20of%20Operations) For Q1 2022, revenues significantly decreased to **$5.9 million** from **$14.7 million** year-over-year, leading to a wider net loss of **$39.1 million** Statement of Operations Summary (in thousands, except per share data) | Metric | Q1 2022 | Q1 2021 | | :--- | :--- | :--- | | Revenues | $5,897 | $14,660 | | Research and development | $29,990 | $22,562 | | General and administrative | $15,039 | $11,107 | | Loss from operations | ($39,132) | ($19,009) | | Net loss | ($39,110) | ($30,359) | | Net loss per share, basic and diluted | ($0.84) | ($0.66) | [Condensed Statements of Comprehensive Loss](index=5&type=section&id=Condensed%20Statements%20of%20Comprehensive%20Loss) Comprehensive loss for Q1 2022 increased to **$39.9 million** from **$30.5 million** in Q1 2021, driven by a higher net loss and unrealized losses on securities Comprehensive Loss Summary (in thousands) | Metric | Q1 2022 | Q1 2021 | | :--- | :--- | :--- | | Net loss | $(39,110) | $(30,359) | | Unrealized loss on available-for-sale securities | $(838) | $(129) | | **Comprehensive loss** | **$(39,948)** | **$(30,488)** | [Condensed Statements of Stockholders' Equity](index=6&type=section&id=Condensed%20Statements%20of%20Stockholders%27%20Equity) Total stockholders' equity decreased by **$32.2 million** to **$220.4 million** as of March 31, 2022, primarily due to the net loss for the quarter - Stockholders' equity declined by **$32.2 million** during Q1 2022, mainly due to a net loss of **$39.1 million**[15](index=15&type=chunk) [Condensed Statements of Cash Flows](index=7&type=section&id=Condensed%20Statements%20of%20Cash%20Flows) Net cash used in operating activities was **$35.3 million** in Q1 2022, resulting in a **$1.5 million** net decrease in cash and equivalents Cash Flow Summary (in thousands) | Activity | Q1 2022 | Q1 2021 | | :--- | :--- | :--- | | Net cash used in operating activities | $(35,255) | $(30,430) | | Net cash provided by (used in) investing activities | $32,982 | $(121,730) | | Net cash provided by financing activities | $760 | $1,826 | | **Net decrease in cash, cash equivalents and restricted cash** | **$(1,513)** | **$(150,334)** | [Notes to Unaudited Condensed Financial Statements](index=8&type=section&id=Notes%20to%20Unaudited%20Condensed%20Financial%20Statements) The notes detail the company's accumulated deficit, liquidity, revenue sources, and the renegotiation of the Tasly License Agreement post-quarter end - The company has an accumulated deficit of **$372.5 million** as of March 31, 2022, but believes its unrestricted cash, cash equivalents, and marketable securities of **$192.1 million** are sufficient to fund operations for at least the next 12 months[23](index=23&type=chunk)[24](index=24&type=chunk)[25](index=25&type=chunk) Revenue by Collaborator (in thousands) | Collaborator | Q1 2022 | Q1 2021 | | :--- | :--- | :--- | | Bristol Myers Squibb Company ("BMS") | $2,165 | $1,239 | | Merck Sharp & Dohme Corporation ("Merck") | $1,064 | $11,883 | | EMD Serono | $1,897 | $220 | | Vaxcyte | $771 | $1,318 | | **Total revenue** | **$5,897** | **$14,660** | - The company did not recognize the **$40.0 million** upfront payment from the Tasly License Agreement as of March 31, 2022, because Tasly requested to renegotiate terms in February 2022[97](index=97&type=chunk) - Subsequent to the quarter end, on April 18, 2022, the Tasly agreement was amended, changing the upfront payment to **$25.0 million** with an additional **$15.0 million** in escrow contingent on regulatory milestones[128](index=128&type=chunk) [Management's Discussion and Analysis of Financial Condition and Results of Operations](index=26&type=section&id=Item%202.%20Management%27s%20Discussion%20and%20Analysis%20of%20Financial%20Condition%20and%20Results%20of%20Operations) Management attributes the Q1 2022 revenue decrease to lower Merck collaboration revenue and explains increased operating expenses due to higher headcount and clinical development activities - The company's two most advanced wholly-owned product candidates are STRO-002 for ovarian and endometrial cancers, and STRO-001 for B-cell malignancies[133](index=133&type=chunk) Financial Results Comparison (in thousands) | Metric | Q1 2022 | Q1 2021 | Change (%) | | :--- | :--- | :--- | :--- | | Revenues | $5,897 | $14,660 | (60)% | | Research and development | $29,990 | $22,562 | 33% | | General and administrative | $15,039 | $11,107 | 35% | | Loss from operations | $(39,132) | $(19,009) | 106% | - The decrease in revenue was primarily due to a **$10.8 million** decrease from Merck, related to the completion of performance obligations under the 2018 agreement[156](index=156&type=chunk) - As of March 31, 2022, the company had **$192.1 million** in cash, cash equivalents, and marketable securities, which is believed sufficient to fund operations for at least the next twelve months[162](index=162&type=chunk)[169](index=169&type=chunk) - The COVID-19 pandemic is causing increased costs and delays in material availability, though patient enrollment and treatment remain on track[141](index=141&type=chunk) [Quantitative and Qualitative Disclosures About Market Risk](index=35&type=section&id=Item%203.%20Quantitative%20and%20Qualitative%20Disclosures%20About%20Market%20Risk) The company is exposed to market risks, primarily interest rate sensitivities on its investment portfolio and equity price risk from its Vaxcyte common stock holding - The company's primary market risks are interest rate sensitivity and equity price risk from its investment in Vaxcyte common stock[185](index=185&type=chunk) - As of March 31, 2022, the company held **$37.7 million** in Vaxcyte common stock, where a hypothetical 10% decrease in market price would reduce fair value by **$3.8 million**[186](index=186&type=chunk)[187](index=187&type=chunk) - The company's outstanding debt of **$25.3 million** bears a floating interest rate, but a 100 basis point change would not materially impact interest expense[189](index=189&type=chunk) [Controls and Procedures](index=35&type=section&id=Item%204.%20Controls%20and%20Procedures) Management concluded that the company's disclosure controls and procedures were effective as of March 31, 2022, with no material changes in internal control over financial reporting - The CEO and CFO concluded that as of March 31, 2022, the company's disclosure controls and procedures were effective at a reasonable assurance level[191](index=191&type=chunk) - No changes in internal control over financial reporting occurred during Q1 2022 that materially affected, or are reasonably likely to materially affect, internal controls[192](index=192&type=chunk) PART II. OTHER INFORMATION [Legal Proceedings](index=36&type=section&id=Item%201.%20Legal%20Proceedings) The company is not currently a party to any legal proceedings that management believes would have a material adverse effect on its business - The company is not presently a party to any legal proceedings that would have a material adverse effect on its business[194](index=194&type=chunk) [Risk Factors](index=36&type=section&id=Item%201A.%20Risk%20Factors) The company outlines significant risks including its history of losses, dependence on early-stage product candidates, need for additional funding, and challenges with its unproven platform and manufacturing - The company has a history of significant losses (**$372.5 million** accumulated deficit as of March 31, 2022) and may never achieve profitability[197](index=197&type=chunk)[200](index=200&type=chunk) - The business is highly dependent on the success of its proprietary product candidates, STRO-001 and STRO-002, which are in early stages of clinical development[197](index=197&type=chunk)[217](index=217&type=chunk) - The COVID-19 pandemic is impacting the availability of routine materials, causing sourcing difficulties and modified manufacturing schedules, which could potentially delay clinical trials[197](index=197&type=chunk)[201](index=201&type=chunk)[205](index=205&type=chunk) - The company's approach is based on novel XpressCF® and XpressCF+® platforms, which are unproven and may not result in marketable products, as no cell-free platform product has FDA approval[223](index=223&type=chunk)[239](index=239&type=chunk) - The company relies on third-party manufacturers for components and faces risks related to their compliance, quality, and supply capacity, as well as risks in scaling its own internal manufacturing[201](index=201&type=chunk)[253](index=253&type=chunk) [Unregistered Sales of Equity Securities and Use of Proceeds](index=88&type=section&id=Item%202.%20Unregistered%20Sales%20of%20Equity%20Securities%20and%20Use%20of%20Proceeds) The company reported no unregistered sales of equity securities during the period - There were no unregistered sales of equity securities in the quarter[427](index=427&type=chunk) [Defaults Upon Senior Securities](index=88&type=section&id=Item%203.%20Defaults%20Upon%20Senior%20Securities) The company reported no defaults upon senior securities - There were no defaults upon senior securities[427](index=427&type=chunk) [Mine Safety Disclosures](index=88&type=section&id=Item%204.%20Mine%20Safety%20Disclosures) This item is not applicable to the company - Not applicable[428](index=428&type=chunk) [Other Information](index=88&type=section&id=Item%205.%20Other%20Information) The company reported no other information for the period - None[429](index=429&type=chunk) [Exhibits](index=89&type=section&id=Item%206.%20Exhibits) This section lists the exhibits filed with the Quarterly Report on Form 10-Q, including CEO and CFO certifications and Inline XBRL data files - The exhibits include certifications from the Principal Executive Officer and Principal Financial Officer pursuant to Sarbanes-Oxley Act Sections 302 and 906, as well as Inline XBRL documents[432](index=432&type=chunk)

STRO-002 Clinical Trial Results and Strategy - In the dose expansion cohort of the STRO-002 trial for ovarian cancer, an overall response rate (ORR) of 333% was observed in all 33 evaluable patients[52] - A higher ORR of 471% was seen in patients starting at the 52 mg/kg dose level[52] - Exploratory analysis suggests that a tumor proportion score (TPS) > 25% correlated with higher response, demonstrating a 400% ORR (10 out of 25 patients)[68, 76] and 538% ORR (7/13) in patients at the 52 mg/kg starting dose[76] - 855% of treatment-emergent adverse events (TEAEs) were Grade 1-2, indicating a manageable safety profile[72, 76] - The company plans to initiate a pivotal trial in ovarian cancer by year-end 2022 and has dosed the first patient in the endometrial cancer cohort in November 2021[13] STRO-001 Clinical Trial and Development - STRO-001 is undergoing Phase 1 dose escalation studies, with the latest reported dose levels at 50 mg/kg in both multiple myeloma (MM) and non-Hodgkin's lymphoma (NHL) cohorts[91] - In the NHL cohort, the median number of prior therapies was 5 (range 1-12)[94] - Interim data from the NHL cohort showed partial responses in two DLBCL patients who had progressed on CAR-T therapy[96] Financial Position and Partnerships - The company reported $2295 million in cash, cash equivalents, and marketable securities as of December 31, 2021[99] - Projected cash runway extends into the second half of 2023, based on current business plans and assumptions[99] - Funding received from collaborators totaled approximately $446 million through December 31, 2021[99]

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, 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 or other jurisdiction o ...