UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 ☐ 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. 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, 2024 OR (Exact Name of Registrant as Specified in its Charter) Delaware 47-0926186 (State ...

[Business Highlights and Outlook](index=1&type=section&id=Business%20Highlights%20and%20Outlook) Sutro Biopharma advanced its luvelta clinical program, secured a major Ipsen licensing deal, and strengthened its financial position in Q1 2024, positioning for key data readouts - The company advanced its luvelta clinical program, progressed its pipeline, and established a new licensing relationship with Ipsen, augmenting its cash position[2](index=2&type=chunk) - Key catalysts for 2024 include expanded patient data for luvelta with bevacizumab, a registrational trial for pediatric AML, and a Phase 2 trial in NSCLC[2](index=2&type=chunk) [Luveltamab Tazevibulin (luvelta) Program Updates](index=1&type=section&id=Luveltamab%20Tazevibulin%20%28luvelta%29%20Program%20Updates) The luvelta program is advancing with active enrollment in REFRαME-O1, planned initiation of REFRαME-P1 for pediatric AML, and an FDA-cleared IND for NSCLC - The randomized portion (Part 2) of the REFRαME-O1 registration-enabling study for platinum-resistant ovarian cancer is actively enrolling[1](index=1&type=chunk)[3](index=3&type=chunk) - An IND for a Phase 2 trial of luvelta in non-small cell lung cancer (NSCLC) has been cleared by the FDA, with patient dosing expected in H2 2024[1](index=1&type=chunk)[3](index=3&type=chunk) - Enrollment for REFRαME-P1, a registration-enabling trial for pediatric AML, is expected to be initiated in H2 2024[2](index=2&type=chunk)[3](index=3&type=chunk) - The Phase 2 expansion study of luvelta in combination with bevacizumab is nearing completion, with enrollment expected to conclude in H1 2024[1](index=1&type=chunk)[3](index=3&type=chunk) [Pipeline and Collaboration Updates](index=2&type=section&id=Pipeline%20and%20Collaboration%20Updates) Sutro secured a global licensing agreement for STRO-003, plans an IND for STRO-004 in 2025, and generated **$864 million** from collaborations - A global licensing agreement for STRO-003 with Ipsen could yield up to **$899 million** in payments plus tiered royalties, with **$75 million** upfront received in April[1](index=1&type=chunk)[9](index=9&type=chunk) - Sutro plans to submit an IND for STRO-004, a tissue factor-targeting ADC, in 2025[9](index=9&type=chunk) - The company has generated approximately **$864 million** in aggregate payments from collaborators through March 31, 2024, leveraging its proprietary cell-free platform[9](index=9&type=chunk) [Corporate Updates and Events](index=2&type=section&id=Corporate%20Updates%20and%20Events) Sutro strengthened its cash position by raising **$75 million** through an equity offering in April and will participate in two investor conferences - Strengthened cash position with an underwritten common stock offering, generating **$75.0 million** in gross proceeds[1](index=1&type=chunk)[5](index=5&type=chunk) - Sutro will participate in the Citizens JMP Life Sciences Conference (May 13-14, 2024) and the Jefferies Healthcare Conference (June 5-6, 2024)[10](index=10&type=chunk) [First Quarter 2024 Financial Performance](index=2&type=section&id=First%20Quarter%202024%20Financial%20Performance) Sutro reported Q1 2024 revenues of **$13.0 million**, a net loss of **$58.2 million**, and increased operating expenses, with a **$267.6 million** cash position bolstered post-quarter - As of March 31, 2024, Sutro held **$267.6 million** in cash and investments, plus **$45.6 million** in Vaxcyte common stock[1](index=1&type=chunk)[6](index=6&type=chunk) - Post-quarter, Sutro's cash position was bolstered by **$75 million** from the Ipsen licensing deal and **$75 million** from an underwritten stock offering in April[1](index=1&type=chunk) Q1 2024 Key Financial Results | Metric | Q1 2024 | Q1 2023 | | :--- | :--- | :--- | | Revenue | $13.0M | $12.7M | | Total Operating Expenses | $69.6M | $54.9M | | Net Loss | ($58.2M) | ($50.1M) | | Net Loss Per Share | ($0.95) | ($0.85) | [Financial Position](index=2&type=section&id=Financial%20Position) As of March 31, 2024, Sutro held **$267.6 million** in cash and equivalents, **$45.6 million** in Vaxcyte stock, with total assets of **$403.4 million** - As of March 31, 2024, Sutro held **$267.6 million** in cash, cash equivalents, and marketable securities[6](index=6&type=chunk) - The company held Vaxcyte common stock valued at **$45.6 million**, resulting in a **$3.7 million** non-operating, unrealized gain for the quarter[6](index=6&type=chunk)[7](index=7&type=chunk) Balance Sheet Summary (in thousands) | Account | March 31, 2024 | December 31, 2023 | | :--- | :--- | :--- | | Total Assets | $403,402 | $470,736 | | Total Liabilities | $305,378 | $321,087 | | Total Stockholders' Equity | $98,024 | $149,649 | [Operating Results](index=2&type=section&id=Operating%20Results) Q1 2024 revenue was **$13.0 million**, total operating expenses increased to **$69.6 million** due to R&D, resulting in a net loss of **$58.2 million** - Revenue for Q1 2024 was **$13.0 million**, a slight increase from **$12.7 million** in Q1 2023, primarily from collaborations[8](index=8&type=chunk) Operating Expenses Comparison (in thousands) | Expense Category | Q1 2024 | Q1 2023 | | :--- | :--- | :--- | | Research and development | $56,878 | $39,399 | | General and administrative | $12,721 | $15,512 | | **Total operating expenses** | **$69,599** | **$54,911** | - Net loss for Q1 2024 was **$58.2 million**, or **($0.95)** per share, compared to **$50.1 million**, or **($0.85)** per share, in Q1 2023[16](index=16&type=chunk) [Financial Statements](index=4&type=section&id=Financial%20Statements) The unaudited Q1 2024 financial statements detail a net loss of **$58.2 million**, total assets of **$403.4 million**, and stockholders' equity of **$98.0 million** [Selected Statements of Operations](index=4&type=section&id=Selected%20Statements%20of%20Operations) Sutro Biopharma reported Q1 2024 revenues of **$13.0 million**, total operating expenses of **$69.6 million**, and a net loss of **$58.2 million** or **($0.95)** per share Q1 2024 vs Q1 2023 Statement of Operations (in thousands, except per share data) | | Three Months Ended March 31, | | :--- | :--- | :--- | | | **2024** | **2023** | | Revenue | $13,008 | $12,674 | | Total operating expenses | $69,599 | $54,911 | | Loss from operations | ($56,591) | ($42,237) | | Net loss | ($58,213) | ($50,050) | | Net loss per share, basic and diluted | ($0.95) | ($0.85) | [Selected Balance Sheets](index=4&type=section&id=Selected%20Balance%20Sheets) As of March 31, 2024, the balance sheet showed **$267.6 million** in cash and equivalents, total assets of **$403.4 million**, and stockholders' equity of **$98.0 million** Balance Sheet as of March 31, 2024 vs December 31, 2023 (in thousands) | | March 31, 2024 | December 31, 2023 | | :--- | :--- | :--- | | **Assets** | | | | Cash, cash equivalents and marketable securities | $267,602 | $333,681 | | Investment in equity securities | $45,616 | $41,937 | | **Total Assets** | **$403,402** | **$470,736** | | **Liabilities and Stockholders' Equity** | | | | Total liabilities | $305,378 | $321,087 | | Total stockholders' equity | $98,024 | $149,649 | | **Total Liabilities and Stockholders' Equity** | **$403,402** | **$470,736** |

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, 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) (State or other jurisdiction of (I.R.S. Employer i ...

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, 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 (S ...

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 ...