8-K
Sutro Biopharma, Inc. (STRO)
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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 8-K
CURRENT REPORT
Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934
Date of Report (Date of earliest event reported): November 10, 2021
SUTRO BIOPHARMA, INC.
(Exact name of registrant as specified in its charter)
| Delaware | 001-38662 | 47-0926186 |
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| (State or other jurisdiction<br><br><br>of Incorporation) | (Commission<br><br><br>File Number) | (IRS Employer<br><br><br>Identification No.) |
111 Oyster Point Blvd,
South San Francisco, California, 94080
(Address of principal executive offices) (Zip Code)
(650) 392-8412
(Registrant’s telephone number, including area code)
Not Applicable
(Former name or former address, if changed since last report)
Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:
| ☐ | Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) |
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| ☐ | Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) |
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| ☐ | Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) |
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| ☐ | Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c)) |
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Securities registered pursuant to Section 12(b) of the Act:
| Title of each class | Trading Symbol(s) | Name of each exchange on which registered |
|---|---|---|
| Common Stock, $0.001 par value | STRO | The Nasdaq Global Market |
Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).
Emerging growth company ☒
If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐
| Item 2.02. | Results of Operations and Financial Condition. |
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On November 10, 2021, Sutro Biopharma, Inc.(the “Company”) issued a press release announcing its financial results for the quarter ended September 30, 2021. A copy of the press release is attached as Exhibit 99.1 to this report.
The information furnished with Item 2.02 of this report, including Exhibit 99.1, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any other filing under the Exchange Act or under the Securities Act of 1933, as amended (the “Securities Act”), except as expressly set forth by specific reference in such a filing.
| Item 7.01. | Regulation FD Disclosure. |
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On November 10, 2021, the Company also updated its corporate presentation. A copy of the corporate presentation is attached as Exhibit 99.2 to this Current Report on Form 8-K. The corporate presentation will also be available on the Company’s website in the Events & Presentations section at https://www.sutrobio.com/corporate-presentation/.
The information furnished in this Item 7.01, including Exhibit 99.2, shall not be deemed “filed” for purposes of Section 18 of the Exchange Act, or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any other filing under the Exchange Act or the Securities Act, except as expressly set forth by specific reference in such a filing.
| Item 9.01. | Financial Statements and Exhibits |
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(d) Exhibits.
| Exhibit<br>No. | Description |
|---|---|
| 99.1 | Press release issued by Sutro Biopharma, Inc. regarding its financial results for the period ended September 30, 2021, dated November 10, 2021. |
| 99.2 | Company Overview Presentation. |
| 104 | Cover Page Interactive Data File (embedded within the Inline XBRL document) |
SIGNATURE
Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.
| Sutro Biopharma, Inc. | ||
|---|---|---|
| Date: November 10, 2021 | By: | /s/ Edward Albini |
| Edward Albini | ||
| Chief Financial Officer |
stro-ex991_61.htm
Exhibit 99.1
Sutro Biopharma Reports Third Quarter 2021 Financial Results, Business Highlights, and Anticipated 2021 Milestones
| - | Patient enrollment has been completed for the STRO-002 Phase 1 ovarian cancer dose-expansion cohort, and an interim data update is expected in the second half of 2021 – |
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| - | STRO-001 Phase 1 dose escalation for non-Hodgkin’s lymphoma and multiple myeloma is ongoing to achieve a recommended Phase 2 dose – |
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| - | Cash, cash equivalents and marketable securities totaled $254.2 million as of September 30, 2021, with projected cash runway into the second half of 2023 – |
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SOUTH SAN FRANCISCO, Calif., Nov. 10, 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 quarter ended September 30, 2021, its recent business highlights, and a preview of anticipated select milestones in the remainder of 2021.
“We are pleased to announce that enrollment has been completed for the STRO‑002 Phase 1 dose-expansion cohort for patients with advanced ovarian cancer. Additionally, we are prioritizing the STRO-002 franchise through additional studies, given the potential for this to be an important treatment option for patients with FolRα-expressing tumors,” said Bill Newell, Sutro’s Chief Executive Officer. “For our STRO-001 program, we continue with dose escalation to achieve a recommended Phase 2 dose and support the work of our partner, BioNova, in Greater China, to explore the therapeutic potential in less heavily pretreated patients with multiple myeloma, non-Hodgkin’s lymphoma, and acute myeloid leukemia.”
Recent Business Highlights and Anticipated 2021 Select Milestones
STRO-002, FolRα-Targeting Antibody-Drug Conjugate (ADC): STRO-002 is being studied in patients with ovarian cancer and endometrial cancer.
| • | The patient enrollment of 40 patients has been completed for the Phase 1 dose-expansion cohort for advanced ovarian cancer, with participation from clinical sites across the U.S. and in Spain. |
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| • | Sutro is expected to report initial data for the dose-expansion cohort in the second half of 2021; the data are expected to inform regulatory discussions and registration strategy, including the planned identification of patient populations that may benefit optimally from treatment with STRO‑002. |
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| • | Sutro has opened a new cohort of the Phase 1 dose-expansion study of STRO-002 for endometrial cancer and is currently enrolling patients. A STRO-002 study in combination with bevacizumab has cleared protocol and the first patient is expected later this year. |
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| 111 Oyster Point Blvd. South San Francisco, CA 94080 | T: 650.392.8412 F: 650.872.8924 W: sutrobio.com |
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| • | Nonclinical data on STRO-002 as a potential therapeutic targeting a rare pediatric acute myeloid leukemia (AML) subtype expressing FolRα will be presented by investigators at the Fred Hutchinson Cancer Research Center (Fred Hutch) as an oral presentation at the 63^rd^ American Society of Hematology Annual Meeting (ASH 2021). Details are as follows: |
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| Publication Number: | 209 |
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| Presentation Title: | Targeting FOLR1 in High-Risk CBF2AT3-GLIS2 AML with STRO-002 FOLR1-Directed Antibody-Drug Conjugate |
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| Presentation Time: | Saturday, December 11, 2021, at 3:00 PM ET |
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| Session Name: | 604. Molecular Pharmacology and Drug Resistance: Myeloid Neoplasms: Novel Molecular Therapies in AML |
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STRO-001, CD74-Targeting ADC: The Phase 1 study for patients with B‑cell malignancies, including patients with non-Hodgkin's lymphoma and multiple myeloma, continues with dose escalation.
| • | Dose escalation is ongoing to achieve a recommended phase 2 dose (RP2D), with the last reported doses of 5.0 mg/kg in the multiple myeloma (MM) cohort and 4.2 mg/kg in the non-Hodgkin's lymphoma (NHL) cohort. |
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| • | Nonclinical data on STRO-001 as a potential therapeutic targeting AML and acute lymphoblastic leukemia (ALL) will be presented by investigators at the Fred Hutch as an oral presentation at ASH 2021. Details are as follows: |
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| Publication Number: | 509 |
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| Presentation Title: | Therapeutic Targeting of CD74 with STRO-001 Antibody-Drug Conjugate in AML and ALL |
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| Presentation Time: | Sunday, December 12, 2021, at 5:30 PM ET |
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| Session Name: | 604. Molecular Pharmacology and Drug Resistance: Myeloid Neoplasms: Novel Strategies to Overcome Resistance to BCL-2 Inhibition |
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Additional Pipeline: Research and preclinical development are underway for several internal candidates.
| • | Sutro announced multiple discovery and preclinical candidates, including ADCs targeting ROR1 and Tissue Factor, a 5T4-CD3 bispecific T-Cell Engager (TCE), and cytokine derivatives, including IFNα and IL-12. |
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| • | Discovery and preclinical work on these programs are underway to determine Sutro’s next program to advance to the clinic. |
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| 111 Oyster Point Blvd. South San Francisco, CA 94080 | T: 650.392.8412 F: 650.872.8924 W: sutrobio.com |
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Collaboration Updates: Sutro continues to seek to maximize the value of its cell-free platform by working with partners on programs in multiple disease spaces and geographies.
| • | In October of this year, Sutro entered into a collaboration with BioNova Pharmaceuticals Limited (BioNova) to assess the therapeutic potential for STRO-001 in potentially less heavily pretreated patient populations with MM, NHL, and AML within Greater China, including mainland China, Hong Kong, Macau, and Taiwan. |
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| • | Merck extended the first cytokine derivative research program by up to two years to continue the work on an additional candidate. Sutro received an initial payment of $2.5 million and is eligible to receive up to a total of $10 million in connection with the research program extension. |
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| • | Sutro continues to manufacture clinical trial material for Bristol Myers Squibb’s (BMS) CC-99712, a BCMA‑targeting ADC, for treatment of patients with multiple myeloma. |
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Third Quarter 2021 Financial Highlights
Cash, Cash Equivalents and Marketable Securities
As of September 30, 2021, Sutro had cash, cash equivalents and marketable securities of $254.2 million, as compared to $326.5 million as of December 31, 2020, with projected runway into the second half of 2023, based on current business plans and assumptions. The above balance does not include the value associated with Sutro’s holdings of Vaxcyte common stock.
Unrealized Gain from Increase in Value of Vaxcyte Common Stock
As of September 30, 2021, Sutro held approximately 1.6 million shares of Vaxcyte common stock, with a fair value of $39.8 million. The non-operating, unrealized gain of $4.5 million for the three months ended September 30, 2021 was due to the increase since June 30, 2021 in the estimated fair value of Sutro’s holdings of Vaxcyte common stock. Vaxcyte common stock held by Sutro will be remeasured 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 $8.5 million for the three months ended September 30, 2021, as compared to $17.8 million for the same period in 2020, related principally to the Merck, BMS, and EMD Serono collaborations. Future collaboration revenue from Merck, BMS, EMD Serono, BioNova, and from any additional 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 three months ended September 30, 2021 were $43.2 million, as compared to $28.4 million for the same period in 2020. The 2021 period includes non-cash expenses for stock-based compensation of $6.5 million and depreciation and amortization of $1.1 million, as compared to $3.1 million and $1.0 million, respectively, in the comparable 2020 period. Total operating expenses for the three months ended September 30, 2021 were comprised of research and development expenses of $26.6 million and general and administrative expenses of $16.6 million, which are expected to increase in 2021
| 111 Oyster Point Blvd. South San Francisco, CA 94080 | T: 650.392.8412 F: 650.872.8924 W: sutrobio.com |
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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 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, first-in-class 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 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.
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 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.
| 111 Oyster Point Blvd. South San Francisco, CA 94080 | T: 650.392.8412 F: 650.872.8924 W: sutrobio.com |
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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, potential future milestone and royalty payments, 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.
Investor Contact
Annie J. Chang
Sutro Biopharma
(650) 801-5728
ajchang@sutrobio.com
Media Contact
Maggie Beller
Russo Partners
(646) 942-5631
Maggie.beller@russopartnersllc.com
| 111 Oyster Point Blvd. South San Francisco, CA 94080 | T: 650.392.8412 F: 650.872.8924 W: sutrobio.com |
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Sutro Biopharma, Inc.
Selected Statements of Operations Financial Data
(Unaudited)
(In thousands, except per share amounts)
| Three Months Ended | Nine Months Ended | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| September 30, | September 30, | |||||||||||
| 2021 | 2020 | 2021 | 2020 | |||||||||
| Revenues | $ | 8,517 | $ | 17,823 | $ | 51,226 | $ | 34,444 | ||||
| Operating expenses | ||||||||||||
| Research and development | 26,602 | 19,361 | 74,473 | 54,223 | ||||||||
| General and administrative | 16,589 | 9,079 | 40,241 | 26,435 | ||||||||
| Total operating expenses | 43,191 | 28,440 | 114,714 | 80,658 | ||||||||
| Loss from operations | (34,674 | ) | (10,617 | ) | (63,488 | ) | (46,214 | ) | ||||
| Interest income | 109 | 295 | 481 | 1,320 | ||||||||
| Unrealized gain (loss) on equity securities | 4,483 | 29,778 | (1,881 | ) | 78,638 | |||||||
| Interest and other expense, net | (820 | ) | (2,317 | ) | (2,525 | ) | (6,328 | ) | ||||
| Net (loss) income | $ | (30,902 | ) | $ | 17,139 | $ | (67,413 | ) | $ | 27,416 | ||
| Net (loss) income per share, basic | $ | (0.67 | ) | $ | 0.46 | $ | (1.46 | ) | $ | 0.91 | ||
| Net (loss) income per share, diluted | $ | (0.67 | ) | $ | 0.45 | $ | (1.46 | ) | $ | 0.90 | ||
| 111 Oyster Point Blvd. South San Francisco, CA 94080 | T: 650.392.8412 F: 650.872.8924 W: sutrobio.com | |||||||||||
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Sutro Biopharma, Inc.
Selected Balance Sheet Financial Data
(Unaudited)
(In thousands)
| September 30, | December 31, | |||
|---|---|---|---|---|
| 2021 ^(1)^ | 2020 ^(2)^ | |||
| Assets | ||||
| Cash, cash equivalents and marketable securities | $ | 254,217 | $ | 326,493 |
| Investment in equity securities | 39,763 | 41,644 | ||
| Accounts receivable | 12,330 | 5,559 | ||
| Property and equipment, net | 23,319 | 12,935 | ||
| Operating lease right-of-use assets | 30,129 | — | ||
| Other assets | 11,714 | 7,480 | ||
| Total Assets | $ | 371,472 | $ | 394,111 |
| Liabilities and Stockholders’ Equity | ||||
| Accounts payable and other liabilities | $ | 21,461 | $ | 16,815 |
| Deferred revenue | 7,949 | 20,703 | ||
| Debt | 24,964 | 24,545 | ||
| Operating lease liability | 33,518 | — | ||
| Total liabilities | 87,892 | 62,063 | ||
| Total stockholders’ equity | 283,580 | 332,048 | ||
| Total Liabilities and Stockholders’ Equity | $ | 371,472 | $ | 394,111 |
(1)The condensed balance sheet as of September 30, 2021 was derived from the unaudited financial statements included in the Company's Quarterly Report on Form 10-Q for the quarter ended September 30, 2021, filed with the Securities and Exchange Commission on November 10, 2021.
(2)The condensed balance sheet as of December 31, 2020 was derived from the audited financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2020, filed with the Securities and Exchange Commission on March 18, 2021.
| 111 Oyster Point Blvd. South San Francisco, CA 94080 | T: 650.392.8412 F: 650.872.8924 W: sutrobio.com |
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NON-CONFIDENTIAL Company Overview November 2021 Sutro Biopharma NASDAQ: STRO Exhibit 99.2
Forward Looking Statements NON-CONFIDENTIAL 2 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. This presentation shall not constitute an offer to sell or the solicitation of an offer to buy, nor shall there be any sale of these securities in any state or other jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or other jurisdiction.
Pioneer and Leader in Cell-Free Technology Optimizing cell-free platform for ADCs and beyond Establish cell-free ecosystem Building ecosystem through strategic partnerships Multiple ADC programs showcasing platform breadth Additional value creation through spinout New modalities and extended value creation Establishing Validating Growing NON-CONFIDENTIAL 3
Industry Leading Cell-Free Protein Synthesis Platform GMP production yields consistent and scalable end-products 1 2 3 4 5 6 Stockpiled Extract Grow Cells from E. Coli Cell Lysis Cellular Extract Cell-Free Protein Synthesis 7 IgG with Non- Natural Amino Acids Linker-Warhead Click Chemistry Homogenous ADC Extract Spray-dried A B Discovery scale (< 1ml) NON-CONFIDENTIAL 4 Exploratory tox and GLP tox scale cGMP production (1,000L) Commercial scale (5-10,000L) Specific to protein design
Advantages of Precision Protein Therapeutics Homogenous, precisely designed complex biologics with optimized performance Months to discover lead drug candidates using transient stable cell lines evaluating a handful of candidates Heterogeneous mixtures have less favorable therapeutic window due to varying performance of each species Click chemistry and non-natural amino acids completely conjugate at precise positions, without loss of efficiency even with increasing complexity Create in parallel, in weeks, hundreds of protein variants to empirically select the best lead candidate based on in vivo performance Conjugations incomplete and unstable creating poorly optimized products, especially with increasing complexity in conjugations Challenges in Traditional Cell-Based Complex Biologics Discovery and Manufacturing Advantages of Sutro’s Cell-Free Synthesis Platform for Best-in-Class Biologics Cell-based production requires different process with scale, causing complexity and unreliability with CMC and manufacturing Precisely designed proteins in a homogeneous product widens therapeutic window due to the selection of the best single species Cell-free production is scalable – the same process in lead discovery as at commercial scale DAR NON-CONFIDENTIAL 5
Deep Arsenal of Tools in the R&D Pipeline Available to Attack Cancer (1) Novel and precise design to drive adaptive and protective immune responses Cytokine Derivative Enhanced tumor targeting of cytotoxic payloads Prodrug cytokine targeting functional cytokine to tumor Bispecific ADC Prodrug Cytokine Derivative ISAC: Immune- stimulating ADC: targeting novel payloads Bispecific Antibody Tumor or Stromal Antigen Immune Cell Engager Optimized format and affinity Improved specificity for optimized therapeutic window Tumor Antigen Dual Tumor Antigens Tumor Selective Mask Conjugated Antibody
ADC or ISAC iADC Tumor Antigen Site-specific dual drug conjugate with complementary modalities (TME modulator +/- immune modulator) Immune Cell Engager Modality Drug Properties (1) Molecules are designed and enabled using Sutro’s XpressCF+TM platform NON-CONFIDENTIAL 6 Target Structure Releasable mask cytokine
Cell-Free Platform Delivering Robust Pipeline Four product candidates in the clinic and late-stage discovery programs STRO-001 is partnered with BioNova Pharmaceuticals Limited for development in Greater China, including mainland China, Hong Kong, Macau, and Taiwan EMD Serono is the biopharmaceutical business of Merck KGaA, Darmstadt Germany in the US Program includes two molecules going after an undisclosed cytokine target NON-CONFIDENTIAL 7 Fast Track Designation Orphan Drug Designation Orphan Drug Designation
NON-CONFIDENTIAL FolRα-Targeting ADC Potential Best-in-Class ADC for Ovarian and Endometrial Cancers STRO 002
STRO-002 Potentially Best-in-Class ADC for Ovarian Cancers STRO 002 STRO-002 is a homogeneous antibody drug conjugate (ADC) with a drug-antibody ratio (DAR) of 4, targeting folate- receptor alpha (FolRα): 1 FolRα is overexpressed in certain cancers including ovarian cancer and endometrial cancer 2 Precisely positioned non-natural amino acids, p-azidomethyl-L-phenylalanine, at positions Y180 and F404 on the heavy chain 3 Stable protease-cleavable linkers, with rapid clearance of toxic catabolite after release and cell killing 4 Warhead is hemiasterlin-derivative(1) with potentially dual mechanism against the tumor – tubulin-inhibitor cytotoxin, less sensitive to P-gp transport and induces immunogenic response upon cell death(2) FolRα targeting ADC with tubulin inhibitor cytotoxin potentially induces immunogenic cell death
1 Sutro-proprietary tubulin-targeting 3-aminophenol hemiasterlin warhead, SC209 Based on STRO-002 pre-clinical models showing immune stimulation at site of tumor upon cell death FolRα Y180 F404 pAMF 3 Protease-cleavable linker 4 Hemiasterlin-derivative warhead 2 NON-CONFIDENTIAL 9
Study Update: Dose-escalation enrollment completed August 2020 Updated dose-escalation data as of April 23, 2021 was presented at 2021 ASCO Annual Meeting in June 2021 STRO 002 Part 1: Dose-Escalation Cohort in Ovarian STRO-002-GM1 Dose-Escalation Cohort Has Been Completed Heavily pre-treated ovarian cancer patients with six median line of prior therapies All-Comers Ovarian Cancer N=39 STRO-002 5.2 mg/kg STRO-002 6.4 mg/kg STRO-002 5.6 mg/kg STRO-002 6.0 mg/kg STRO-002 4.3 mg/kg STRO-002 2.9 mg/kg STRO-002 0.5-1.8 mg/kg 34 patients treated at clinically active dose (≥ 2.9 mg/kg Q3W) Of which, 31 patients were evaluable for RECIST Go-forward doses for expansion cohorts Note: Dose-escalation data as of April 23, 2021 and was presented at the 2021 ASCO Annual Meeting NON-CONFIDENTIAL 10
STRO-002 Was Generally Well Tolerated 86% of TEAEs remain Grade 1-2 and no observed ocular toxicity signal
Dose Levels in Dose-Escalation Common TEAEs > 25% By Grade (2) MTD was not reached; DLTs occurred in 2 patients: Grade 2 neuropathy/Grade 3 arthralgia at 6.0 mg/kg and Grade 3 bone pain at 6.4 mg/kg Not included in table are two Grade 5 events, both previously reported and unrelated to study drug by investigator assessment: death not otherwise specified and acute GI bleed Neutropenia included the following preferred terms: neutropenia, febrile neutropenia, and neutrophil count decreased Neuropathy included the following preferred terms: neuropathy peripheral and peripheral sensory neuropathy STRO 002 Note: Dose-escalation data as of April 23, 2021 and was presented at the 2021 ASCO Annual Meeting NON-CONFIDENTIAL 11
STRO 002 (1) Maximum % change from baseline in sum of longest diameter in evaluable patients treated with STRO-002 at ≥ 2.9 mg/kg Objective Response was observed in 10 patients Treatment ongoing as of April 23, 2021 -30% Partial Response Maximum Change (1) in Tumor Target Lesions (N=31)
20%
0% Starting Dose, Q3W 2.9 mg/kg 4.3 mg/kg 5.2 mg/kg 5.6 mg/kg 6.0 mg/kg 6.4 mg/kg CR (2) (2) CR in patient treated at 2.9 mg/kg with resolution of peritoneal disease Note: Dose-escalation data as of April 23, 2021 and was presented at the 2021 ASCO Annual Meeting NON-CONFIDENTIAL 12 PR PR PRu PRu PRu PRu PRu PR PR Tumor Reduction Observed in Majority of Patients 10 patients met criteria for RECIST response including one CR
20 -30 -100 0 0 13 26 65 78 Weeks since first treatment 39 52 Change from baseline (%) Best Overall Response (BOR)
PD SD PRu PR CR Treatment ongoing as of April 23, 2021 CR (1) Tumor Regression and Control Over Time Deepening of responses and two patients with prolonged stable disease remaining on study Change in Sum of Diameters for Target Lesions Over Time (N=31) STRO 002 (1) CR in patient treated at 2.9 mg/kg with resolution of peritoneal disease Note: Dose-escalation data as of April 23, 2021 and was presented at the 2021 ASCO Annual Meeting NON-CONFIDENTIAL 13
Weeks since first treatment Individual patients treated with STRO-002 Treatment Duration (1) and Response, Based on Evaluable Patients (N=31) Clinical Benefit Seen in Heavily Pre-Treated Patient Population Median duration of response is 5.8 months and three patients remained on study at over 18 months STRO 002 Dose Level Treatment ongoing as of April 23, 2021 Dose adjustment PR CR Calculated as date of PD or time from first dose to last dose given (including 4 patients deriving clinical benefit post progression per investigator assessment) DOR is on 5 confirmed responders (1 CR and 4 PRs) Note: Dose-escalation data as of April 23, 2021 and was presented at the 2021 ASCO Annual Meeting 2.9 mg/kg3.5 mg/kg4.3 mg/kg5.2 mg/kg5.6 mg/kg6.0 mg/kg6.4 mg/kg 14 Median Duration of Response (DOR) (2) is 5.8 months (95% CI: 2.0 months, not evaluable)
STRO 002 Favorable PFS Compared to Chemotherapy and Other Agents Based on Kaplan-Meier estimates, median PFS was 7.2 months PFS is calculated on 39 patients from the time from the first dose of study treatment until the time of death or progressive disease (PD) whichever occurs first. If no death or PD, PFS is censored at last disease assessment DOR is on 5 patients on confirmed responses (1 CR and 4 PRs) Note: Dose-escalation data as of April 23, 2021 and was presented at the 2021 ASCO Annual Meeting FORWARD I study showed median PFS of 4.1 months for mirvetuximab and 4.4 months for chemotherapy (HR 0.98, p=0.897) Source: Moore, K.N., et al. (2021) Phase III, randomized trial of mirvetuximab soravtansine versus chemotherapy in patients with platinum-resistant ovarian cancer: primary analysis of FORWARD I. Annals of Oncology. https://doi.org/10.1016/j.annonc.2021.02.017 Durability at a Median Study Follow-up of 8.4 Months NON-CONFIDENTIAL 15
STRO 002 FolRα-Expression by Immunohistochemistry Responses and anti-tumor activity observed across various FolRα-expression levels Best Overall Response (BOR) PR PRu SD PD (1) Assessed by Ventana FOLR1 expression assay based on available archival tissue from dose-escalation patients and scored using H-score and PS2 methods Note: Dose-escalation data as of April 23, 2021 and was presented at the 2021 ASCO Annual Meeting 1 NON-CONFIDENTIAL 16 12 45 90 105 105 125 125 134 135 155 165 190 185 210 235 245 295 0 100 200 300 H-score (Ventana FOLR1 assay) Immunohistochemistry Data (1) for Patients Treated at ≥ 2.9 mg/kg Individual Patients (N=18)
STRO 002 Expanding the STRO-002 Franchise Enrollment completed in Dose-Expansion Cohort and new studies initiated 39 patients, 31 evaluable at active doses Enrollment completed Aug 2020 Unselected for FolRα-expression levels Median of 6 prior lines of therapy Updated at ASCO 2021 1 CR, 4 PRs and 5 unconfirmed PRs DoR of 5.8 months 86% of TEAEs Grade 1-2 and no observed ocular toxicity signal > 40 patients enrolled in US and Spain sites Enrollment completed Nov 2021, FPI in Jan 2021 Unselected for FolRα; tissue required for analysis 1-3 prior lines of therapy, platinum resistant and ≥ 2 prior lines of platinum therapy Interim data expected 2H 2021 Dose-Expansion Cohort Preselected for FolRα-expression levels Initial enrollment planned for ~15 patients Cohort is open and enrolling patients Other Solid Tumor Indications Endometrial Cancer Cohort Combo Trial with Bevacizumab STRO-002 in combination with bevacizumab Protocol cleared by FDA; FPI planned for 2H 2021 Potential for a basket study design with other FolRα expressing cancers Preclinical work ongoing NSCLC Precedent from single-arm registration-directed trial in advanced ovarian cancer Registration-Directed Trial Ovarian Cancer Dose-Escalation Cohort Pending FDA EOP1/2 Meeting NON-CONFIDENTIAL 17
NON-CONFIDENTIAL CD74-Targeting ADC Potential First and Best-in-Class ADC for B-Cell Malignancies STRO 001
Stable CD74 targeting ADC for hematological cancers designed to minimize bystander effects
1 Potential First-in-Class Molecule for Patients with NHL and MM STRO 001 STRO-001 is a homogeneous antibody drug conjugate (ADC) with a drug-antibody ratio (DAR) of 2, targeting CD74: Comprises two non-cleavable linker-warheads that are stable in circulation CD74 F404 pAMF 2 3 Non-cleavable linker CD74 is expressed in many hematological cancers and rapidly internalized The active catabolite, Maytansinoid derivative, efficiently kills tumor cells following internalization of the ADC and was designed to minimize bystander effects Maytansinoid warhead 4 NON-CONFIDENTIAL 19 1 2 Conjugation through precisely positioned non-natural amino acids. p-azidomethyl-L- phenylalanine, at positions F404 on the heavy chain 4 3
R/R multiple myeloma (N=30) R/R NHL (N=30) Cohort A Cohort B RP2D RP2D STRO-001-BCM1 Dose-Escalation Study STRO-001-BCM1 Study Design and Updates Ongoing Phase 1 dose-escalation study with NHL update at ASH 2020 STRO 001 NHL Cohort Update at ASH 2020 0.91 mg/kg† 1.27 mg/kg† 1.78 mg/kg† 2.5 mg/kg† 3.5 mg/kg† MTD X mg/kg 0.075–0.65 mg/kg Single-dose cohorts N=6 total None Patients treated DLTs (1) DLT disclosed in 2019, patient with bulky lymphadenopathy and concurrent DVT receiving 0.91 mg/kg Q3W Note: Data as of October 30, 2020 from data reported at ASH 2020. As of October 2021, the last reported doses levels were of 5.0 mg/kg in the multiple myeloma (MM) cohort and 4.2 mg/kg in the non-Hodgkin's lymphoma (NHL) cohort. NON-CONFIDENTIAL 20 Cohort B, NHL Dosing Schedule (ASH 2020)
ASH 2020 Update in NHL Cohort Heavily pre-treated patient population with 5 median lines of prior therapies STRO 001 Note: Data as of October 30, 2020 from ASH 2020 NON-CONFIDENTIAL 21
Responses to STRO-001 Treatment Duration Encouraging Interim Treatment Duration and Responses Partial responses in two DLBCL patients who had progressed on CAR-T STRO 001 (1) 18 patients are evaluable for response as of October 30, 2020 Note: Data as of October 30, 2020 from ASH 2020 0 50 100 * Patient had a prolonged dose delay (cycle 2 to cycle 3) due to COVID-19
200 250 300 150 Study day Individual patients with NHL treated with STRO-001 (N=18)(1) 0.075 to 0.65 mg/kg Q2W 0.91 mg/kg Q3W 1.27 mg/kg Q3W 1.78 mg/kg Q3W 2.5 mg/kg Q3W Continuing study treatment NON-CONFIDENTIAL 22 SD* PR SD SD PR CR
Financial Overview Well-capitalized through cash and other financial sources NON-CONFIDENTIAL 23 $254.2M in cash, cash equivalents & marketable securities as of Sept. 30, 2021 Projected cash runway into 2H 2023, based on current business plans and assumptions ~1.6M shares of Vaxcyte (Nasdaq: PCVX) not included in the above reported cash Funding received from our collaborators of ~$434M through Sept. 30, 2021
Driving Value Through Advancing Programs Prioritizing expanding the STRO-002 franchise NON-CONFIDENTIAL 24
Experienced Leadership Team William Newell, JD Chief Executive Officer and Member of the Board of Directors Trevor Hallam, PhD President of Research and Chief Scientific Officer Arturo Molina, MD, MS, FACP Chief Medical Officer Ed Albini, MBA Chief Financial Officer Shabbir Anik, PhD Chief Technical Operations Officer Linda Fitzpatrick Chief People and Communications Officer Nicki Vasquez, PhD Chief Portfolio Strategy and Alliance Officer Neurex Lynx Jane Chung, RPh Chief Commercial Officer NON-CONFIDENTIAL 25