On August 7, 2025 Sutro Biopharma, Inc. (Sutro or the Company) (NASDAQ: STRO), an oncology company pioneering site-specific and novel-format antibody drug conjugates (ADCs), reported its financial results for the second quarter of 2025 and recent business highlights (Press release, Sutro Biopharma, AUG 7, 2025, View Source [SID1234655000]).

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"In the second quarter, we made strong progress advancing our pipeline of novel ADCs, including preparing to initiate a clinical trial for STRO-004—our next-generation, Tissue Factor-targeting exatecan ADC—planned for the second half of this year," said Jane Chung, Sutro’s Chief Executive Officer. "Over the past several months, we’ve generated compelling preclinical data across our entire pipeline, further supporting our candidates’ best-in-class potential as well as highlighting the unique capabilities of our platform technology."

Ms. Chung continued: "We are especially excited about our dual-payload ADCs—an area where we are at the forefront of innovation and see significant potential to transform cancer treatment by unlocking durable efficacy. We are already seeing early validation through our strategic collaboration with Astellas, underscored by the initiation of an IND-enabling toxicology study for the first dual-payload immunostimulatory ADC. As we look to the second half of the year, we are well capitalized to meet our top priority of pipeline execution which we believe is critical to increasing shareholder value and we continue to look for ways to implement operating efficiencies and further extend our cash runway."

Wholly-Owned Pipeline

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STRO-004: IND preparations are well underway, with a first-in-human basket trial on track to begin in the second half of 2025, initially focused on solid tumors. STRO-004 has a favorable preclinical safety profile in cynomolgus monkeys up to 50 mg/kg, the highest dose tested.
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STRO-006: Sutro’s differentiated integrin beta-6 (ITGB6) ADC is expected to enter clinical development in 2026 for the treatment of multiple solid tumors.
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Dual-Payload Program: Sutro continues to progress its wholly-owned dual-payload ADC platform, with an IND filing anticipated in 2027.

Next-Generation ADC Collaborations

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Astellas: Two research and development programs are progressing under Sutro’s collaboration with Astellas focused on dual-payload immunostimulatory ADCs (iADCs), including one program that recently entered an IND-enabling toxicology study—triggering a $7.5 million milestone payment to Sutro.
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Ipsen: Ipsen made a strategic decision not to advance the STRO-003 program under its partnership with Sutro, following the review of new data and developments in the ROR1 landscape. STRO-003 continues to be recognized as a well-engineered ADC candidate. This decision does not have any impact on the Company’s previous guidance on cash runway.

Medical Conferences

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4th World ADC Asia Summit: In June, Sutro shared preclinical data demonstrating the potential for dual-payload ADCs to overcome prior ADC resistance in tumor models. The Company also shared encouraging safety data in non-human primates for dual-payload ADC DAR8 exatecan + DAR4 MMAE at a dose of 12.5 mg/kg.
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21st Annual PEGS Boston: The Essential Protein Engineering & Cell Therapy Summit: In May, Sutro shared preclinical data on STRO-006, demonstrating superior anti-tumor activity compared to first-generation ITGB6 ADCs at clinically relevant dose levels. The data also highlighted a favorable pharmacokinetic and tolerability profile at 25 mg/kg dose.
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2025 AACR (Free AACR Whitepaper) Annual Meeting: In April, Sutro presented encouraging preclinical results from STRO-004 and its dual-payload ADC programs. Notably, a single dose of STRO-004 produced promising overall response and disease control rates in Tissue Factor-positive patient-derived xenograft models across multiple tumor types.

Upcoming Investor Conference

Management will participate in the following upcoming healthcare investor conference. A webcast of the presentation will be accessible through the News & Events page of the Investor Relations section of the Company’s website at www.sutrobio.com. An archived replay will be available for at least 30 days after the event.

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Wells Fargo Healthcare Conference, September 3-5, 2025, in Boston

Corporate Updates

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In July, Sutro announced a research collaboration with the U.S. Food and Drug Administration (FDA) to develop reference materials to improve regulatory standards and enhance analytical methods for ADC drug development.
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In June, Sutro appointed Greg Chow as Chief Financial Officer.

Second Quarter 2025 Financial Highlights

Cash, Cash Equivalents and Marketable Securities

As of June 30, 2025, Sutro had cash, cash equivalents and marketable securities of $205.1 million, as compared to $249.0 million as of March 31, 2025. Cost reductions subsequently realized from the restructuring, combined with refocused clinical development priorities give the Company an expected cash runway into early 2027, excluding additional anticipated milestones from existing collaborations.

Revenue

Revenue was $63.7 million for the quarter ended June 30, 2025, as compared to $25.7 million for the quarter ended June 30, 2024, with the 2025 amount related principally to the Astellas collaboration and the recognition of previously deferred revenue as a result of Ipsen’s decision not to advance the STRO-003 program under its partnership with Sutro. Future collaboration and license revenue under existing agreements, and from any additional collaboration and license partners, will fluctuate as a result of the amount and timing of revenue recognition of upfront, milestones, and other agreement payments.

Research & Development (R&D) and General & Administrative (G&A) Expenses

Total R&D and G&A expenses for the quarter ended June 30, 2025 were $48.7 million, as compared to $74.4 million for the quarter ended June 30, 2024. The 2025 period includes non-cash expenses for stock-based compensation of $2.8 million and depreciation and amortization of $1.9 million, as compared to $6.2 million and $1.8 million, respectively, in the 2024 period. For the quarter ended June 30, 2025, R&D expenses were $38.4 million and G&A expenses were $10.3 million.

Restructuring and Related Costs

Restructuring and related costs for the quarter ended June 30, 2025 were $18.4 million. Sutro will continue to recognize restructuring and related costs in future periods for the deprioritization of the luvelta program, of which it expects to recognize a significant portion in 2025. The ultimate amount of expense will be affected by the timing to complete Sutro’s cost commitments to its third-party CROs and CMOs and the full wind-down of the clinical trials. Sutro will revise its estimates of the costs to deprioritize these studies for the luvelta program and the amount of severance and benefits paid to employees as new information becomes available to the Company in future periods.