Sutro Biopharma Highlights Next-Generation ADC Innovation and Near-term Pipeline at Research Forum

High DAR Dual-Payload ADC

Proprietary cell-free platform enables the design of next-generation ADCs intended to broaden addressable patient populations

STRO-004 (tissue factor ADC) preclinical data has demonstrated greater anti-tumor activity and lower toxicity compared to a benchmark tissue factor ADC

Preclinical models highlight potent anti-tumor activity of Sutro dual-payload (ADC²) and immunostimulatory (iADC) ADCs

Expects to deliver three Investigational New Drug (IND) applications over the next three years with potential for best in class

Investor webcast today at 1:30 p.m. PT / 4:30 p.m. ET; https://ir.sutrobio.com/news-events/ir-calendar

SOUTH SAN FRANCISCO, Calif., Oct. 10, 2024 – Sutro Biopharma, Inc. (Sutro or the Company) (NASDAQ: STRO), a clinical-stage oncology company pioneering site-specific and novel-format antibody drug conjugates (ADCs), is hosting an investor webcast today highlighting its proprietary cell-free platform and its use to design and develop next-generation ADC innovation, including a near-term pipeline of differentiated programs with potential across a broad range of tumor types. The presentation will include an overview of Sutro’s strategic approach with the goal of improving the therapeutic index of ADCs. It will also provide details on the Company’s early-stage ADC pipeline, including STRO-004 (tissue factor-targeting ADC), dual-payload ADCs (ADC²) and immunostimulatory ADCs (iADC).

“The precise design enabled by Sutro’s cell-free platform has allowed us to develop ADCs with a wide range of features that are not currently possible with other cell-bound approaches,” said Hans-Peter Gerber, Ph.D., Sutro’s Chief Scientific Officer. “This includes the ability to safely increase potency and combine different payloads to overcome specific limitations such as tumor resistance. Today we are highlighting key data supporting our advancements in these areas, along with the long-term potential of our platform to deliver new ADC innovation. This includes plans for three IND filings for wholly owned programs over the next three years and the advancement of additional differentiated preclinical programs for internal development or external partnering.”

The event will feature presentations by members of Sutro’s senior management team, functional leaders and Peter Sandor, M.D., EVP and Head of Corporate Strategy at Astellas Pharma (previously SVP, Primary Focus Lead Immuno-Oncology at Astellas, with responsibility for the Sutro-Astellas strategic collaboration to advance iADCs). Sutro management will participate in a Q&A session at the end of the presentation.

Next-Generation ADC Innovation:

• Making ADCs better outside the tumor: Sutro’s proprietary cell-free platform enables key elements of ADC design that are intended to reduce platform toxicities associated with current-generation ADCs, including interstitial lung disease; skin, eye, liver and kidney toxicities; and thrombocytopenia. This includes transformational technology across the design of antibodies, payloads, linker and conjugation chemistry that have been demonstrated in preclinical models to reduce toxicities and improve pharmacokinetics.
• Making ADCs better inside the tumor: Sutro highlights three approaches enabled by its cell-free platform: 1) increasing potency safely with higher drug-antibody ratio (DAR) exatecan ADCs; 2) combining payloads to overcome tumor resistance with dual-payload ADCs (ADC²); and 3) delivering next-generation immuno-oncology therapeutics with immunostimulatory ADCs (iADC) that combine immune activation with cytotoxic payloads.

Data Highlights and Near-Term Pipeline Milestones:

• STRO-004, a tissue factor-targeting ADC, which features a DAR8 exatecan payload and site-specific linker design, demonstrated greater anti-tumor activity and lower toxicities than a tissue factor benchmark ADC in preclinical models. Sutro anticipates filing an IND for STRO-004 with the U.S. Food & Drug Administration in the second half of 2025.
• Dual-payload ADCs (ADC²) provide therapeutic benefits compared to standard ADCs, including overcoming tumor resistance mechanisms, showing increased anti-tumor activity and desirable properties in preclinical models.
• iADCs provide a novel mechanism of action, bridging innate and adaptive immunity to enable broad protection in a single molecule, and show increased and durable anti-tumor activity in a preclinical model compared to standalone ADCs or immune-stimulating antibody conjugates.
• Sutro’s proprietary and partnered preclinical ADC portfolio has potential across a broad range of tumor types and the Company plans to deliver three INDs over the next three years, including for STRO-004 in the second half of 2025. The Company also intends to advance a deep pipeline of preclinical programs, providing further potential for internal development and/or partnering.