Sonoma Biotherapeutics’ Treg Cell Therapy Shows Therapeutic Activity in Refractory Rheumatoid Arthritis

SOUTH SAN FRANCISCO, CA & SEATTLE, WA — October 29, 2025 — Sonoma Biotherapeutics, Inc., a clinical-stage company developing engineered regulatory T cell (Treg) therapies, today announced positive interim safety and efficacy data from the Phase 1 REGULATE-RA clinical trial of its lead program, SBT-77-7101, in patients with refractory rheumatoid arthritis (RA). The results are being presented today in a late-breaking oral presentation at the American College of Rheumatology (ACR) Convergence 2025.

The data, from a first-in-human study, indicate the potential for SBT-77-7101 to restore immune balance without the need for toxic conditioning chemotherapy.

Encouraging Safety and Efficacy Signals

The Phase 1 REGULATE-RA study is evaluating three ascending doses of the autologous Treg product in patients whose severe RA has resisted multiple prior conventional and biologic treatments. The interim findings include data from the first two low-to-medium dosing cohorts (n=6).

• Safety Profile: SBT-77-7101 demonstrated a favorable safety profile with no dose-limiting toxicities (DLTs), cytokine release syndrome (CRS), or immune effector cell-associated neurotoxicity syndrome (ICANS) observed.
• Clinical Activity: By Week 4, 4 out of 6 participants (67%) experienced a ≥50% reduction in swollen and tender joint counts from baseline. Furthermore, 83% of participants showed a reduction in disease activity scores (DAS28-CRP and CDAI).
• Dose Response: Participants in the higher-dose Cohort 2 showed deeper and more consistent reductions in joint counts and overall disease activity, including one patient with a durable response maintained through Week 24.
• Mechanistic Validation: Post-infusion biopsies from Cohort 2 participants showed a reduction in inflammatory scores. Crucially, the therapeutic cells (CAR+ Tregs) were detectable in both synovial tissue and peripheral blood, confirming local and systemic presence.

Treg Approach Offers Low-Toxicity Potential

SBT-77-7101 is a chimeric antigen receptor (CAR) Treg product engineered to target citrullinated proteins (CitP), which are abundant in the inflamed joint tissue of RA patients. Unlike cytotoxic CAR T-cell therapies used in oncology, this product is designed to restore immune system balance without destroying target cells, thereby avoiding commonly associated serious adverse events.

“The study is providing clinical and mechanistic evidence of therapeutic activity alongside emerging signs of durability and a favorable safety profile,” said Jeff Bluestone, PhD, CEO and President of Sonoma Biotherapeutics.

Joe Arron, MD, PhD, Chief Scientific Officer, added that achieving these results without conditioning chemotherapy “further supports the approach we have pioneered here at SonomaBio as we work to develop a new generation of targeted and durable Treg cell therapies.”

Sonoma Biotherapeutics plans to complete the ongoing dose escalation before advancing SBT-77-7101 into the dose expansion phase.