Sonoma Biotherapeutics has reported encouraging interim safety and efficacy data from its ongoing Phase 1 REGULATE-RA clinical trial evaluating SBT-77-7101, an engineered regulatory T cell (Treg) therapy, in patients with refractory rheumatoid arthritis. The results were presented during a late-breaking oral session at the 2025 American College of Rheumatology (ACR) Convergence in Chicago.
Favorable Safety Profile in First-in-Human Study
The REGULATE-RA trial is evaluating three ascending doses of SBT-77-7101 in patients with refractory rheumatoid arthritis, a severe form of RA that persists despite treatment with multiple conventional, biologic, and targeted synthetic therapies. The interim data encompass six participants across two cohorts—three in the lowest dosing cohort and three in the medium dosing cohort.
"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," said Jeff Bluestone, PhD, Chief Executive Officer and President of Sonoma Biotherapeutics. "The study is providing clinical and mechanistic evidence of therapeutic activity alongside emerging signs of durability and a favorable safety profile."
The therapy demonstrated a favorable safety profile with no dose-limiting toxicities (DLTs), cytokine release syndrome (CRS), or immune effector cell-associated neurotoxicity syndrome (ICANS) observed in the first two cohorts.
Clinical Efficacy Signals
The interim efficacy data showed promising clinical activity. By week 4, 67% of participants achieved a 50% or greater reduction in swollen and tender joint counts. Additionally, 83% of participants showed improvements in DAS28-CRP and CDAI disease activity scores, key measures of rheumatoid arthritis severity.
Participants in the higher-dose cohort experienced deeper and more consistent responses, with one participant showing a durable effect through week 24. This suggests potential dose-dependent efficacy that may inform optimal dosing strategies for future development.
Mechanistic Evidence of Activity
The study provided mechanistic evidence supporting the therapeutic approach. CAR+ Tregs were detected in both synovial tissue and blood, indicating both systemic and local activity of the engineered cells. This finding validates the potential for antigen-directed Tregs to treat autoimmunity, even in highly refractory patients with high levels of baseline disease activity.
"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, Chief Scientific Officer.
Next Steps and Development Plans
The company plans to complete the ongoing dose escalation phase of SBT-77-7101 before advancing into the dose expansion phase. The trial's exploratory endpoints include assessment of SBT-77-7101's pharmacokinetic profile, pharmacodynamic parameters, mechanism of action, and potential efficacy.
Sonoma Biotherapeutics' proprietary platform technologies are built on Nobel Prize-winning science that changed the field of immunology, positioning the company to develop engineered regulatory T cell therapies for autoimmune and inflammatory diseases.
