Favorable early safety profile with preliminary clinical and mechanistic evidence of therapeutic activity in refractory rheumatoid arthritis
Data to be presented in a late-breaking oral presentation today 8:00 a.m. CT at the 2025 American College of Rheumatology (ACR) Convergence
SOUTH SAN FRANCISCO, Calif. & SEATTLE--(BUSINESS WIRE)--Sonoma Biotherapeutics, Inc., a clinical-stage biotechnology company developing engineered regulatory T cell (Treg) therapies for autoimmune and inflammatory diseases, today announced interim safety and efficacy data from the Phase 1 Regulate-RA clinical trial. The results will be featured as a late-breaking oral presentation today at 8:00 a.m. CT at the 2025 American College of Rheumatology (ACR) Convergence, taking place in Chicago, IL.
“We are very encouraged by these positive interim results from a first-in-human study of our proprietary program SBT-77-7101 in patients with refractory rheumatoid arthritis (RA), a severe form of RA that persists despite treatment with multiple conventional, biologic, and targeted synthetic therapies,” said Jeff Bluestone, PhD, Chief Executive Officer and President. “The study is providing clinical and mechanistic evidence of therapeutic activity alongside emerging signs of durability and a favorable safety profile. We look forward to completion of the ongoing dose escalation of SBT-77-7101 and its advancement into the dose expansion phase.”
Trial Overview and Interim Findings:
REGULATE-RA is an ongoing first-in-human, phase 1 study evaluating the safety and tolerability of three ascending doses of SBT-77-7101 in patients with refractory rheumatoid arthritis (RA). Exploratory endpoints include assessment of SBT-77-7101’s pharmacokinetic (PK) profile, pharmacodynamic (PD) parameters, mechanism of action (MOA), and potential efficacy.
The data presented include 6 participants with refractory RA—3 participants in Cohort 1, the lowest dosing cohort, and 3 participants in Cohort 2, the medium dosing cohort—who have received SBT-77-7101. SBT-77-7101 has a favorable safety profile in the first two cohorts, with no dose-limiting toxicities (DLTs), cytokine release syndrome (CRS), or immune effector cell-associated neurotoxicity syndrome (ICANS).
- By Week 4, across both dose levels, 4 out of 6 participants (67%) experienced ≥50% reduction in swollen and tender joint counts from baseline. Additionally, 5 out of 6 participants (83%) showed a reduction in both DAS28-CRP and CDAI, with 4 out of 6 participants (67%) achieving a reduction of DAS28-CRP score ≥2 and a reduction of CDAI ≥25.5.
- Participants in Cohort 2, who received a higher dose of SBT-77-7101, demonstrated deeper and more consistent reductions in joint counts compared to those in Cohort 1.
- Baseline disease activity was higher in Cohort 2, in which all participants showed clinically meaningful improvements in disease activity by Week 4, including 1 participant with a durable response through Week 24. Data for the remaining participants are still maturing, and follow-up is ongoing.
- All post-infusion biopsies collected from Cohort 2 participants showed a reduction in inflammatory scores.
- Additionally, CAR+ Tregs were detectable in both synovial tissue and peripheral blood, indicating local and systemic presence of SBT-77-7101.
“It is gratifying to see the preliminary safety, PK/PD, and efficacy data in the Phase 1 REGULATE-RA clinical trial, as it validates the potential for antigen-directed Tregs to treat autoimmunity, even in highly refractory patients with high levels of baseline disease,” stated Joe Arron, MD, PhD, Chief Scientific Officer of Sonoma Biotherapeutics. “In addition, to do so without the need for 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.”
Further details on the late-breaking oral presentation below:
- Title: “A Phase 1 Study of Autologous CAR-Treg Cells in Refractory Rheumatoid Arthritis: Interim Report of Safety and Efficacy”
- Presenting Author: Minna Kohler, MD
- Abstract Number: 2213281
- Session: Late-Breaking Abstracts
- Date/ Time: Wednesday, October 29th, 8:00-9:30 a.m. CT
- Location: W375C
In addition, SonomaBio had two poster presentations earlier in the meeting.
Abstract: 0501
- In an interim demographics and safety review of Regulate-RA, participants with highly refractory RA demonstrated a favorable safety profile in the first two cohorts. SBT-77-7101 also shown favorable safety in the first cohort of Regulate-HS, a phase 1 study in hidradenitis suppurativa. Ongoing evaluation of safety, efficacy, PK, and PD will continue across escalating doses in Regulate-RA and Regulate-HS.
Abstract: 2277
- In a study of cellular biomarkers in RA, RA patients were shown to have significantly reduced frequency of Tregs with an effector phenotype and a higher proportion of CD4+ central memory T cells, compared to healthy donors. Effector Tregs have been shown to be the more functional subset of Tregs with high suppressive capacity, which correlates with a relationship between these immune subsets to the pathogenesis of RA.
About SBT-77-7101
SBT-77-7101 is an autologous Treg product transduced with a chimeric antigen receptor (CAR) specific for citrullinated proteins (CitP), which are present in the inflamed synovium of rheumatoid arthritis (RA) patients. Unlike cytotoxic CAR-T therapies, SBT-77-7101 may restore balance to the immune system without target cell destruction and commonly associated serious adverse events. Critically, SBT-77-7101 requires no lymphodepletion or chronic administration. SBT-77-7101 is currently being evaluated in Phase 1 clinical trials for patients with rheumatoid arthritis (RA) and hidradenitis suppurativa.
About Sonoma Biotherapeutics
Sonoma Biotherapeutics is a clinical-stage biotechnology company developing engineered regulatory T cell (Treg) therapies to treat serious autoimmune and inflammatory diseases by restoring immune system balance. Founded by pioneers in Treg biology and cell therapy, including Dr. Fred Ramsdell, whose foundational research in Treg biology was recognized with a 2025 Nobel Prize, Sonoma Biotherapeutics combines deep scientific expertise with proprietary platform technologies to advance a new generation of targeted and durable Treg cell therapies.
In addition to its lead, proprietary Treg program, SBT-77-7101, Sonoma Biotherapeutics is collaborating with Regeneron to advance a pipeline of Treg cell therapies for autoimmune diseases.
For more information, visit sonomabio.com and follow Sonoma Biotherapeutics on X (formerly Twitter) and LinkedIn.
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