Sonoma’s SBT-77-7101 Shows Early Promise in Rheumatoid Arthritis Trial
Sonoma Biotherapeutics has reported positive interim findings from its ongoing phase 1 REGULATE-RA trial of SBT-77-7101, an investigational cell therapy for patients with refractory rheumatoid arthritis (RA).
The data was presented during a late-breaking oral session at the 2025 American College of Rheumatology (ACR) Convergence in Chicago, drawing attention to a programme designed for people whose disease persists despite multiple conventional, biologic and targeted synthetic treatments.
In remarks accompanying the presentation, the company’s Chief Executive Officer and President said Sonoma is very encouraged by these early, first-in-human results, noting that the study is providing clinical and mechanistic signals of therapeutic activity alongside emerging signs of durability and a favourable safety profile.
The company added that it looks forward to completing dose escalation and advancing into the dose-expansion phase.
The REGULATE-RA study is assessing three ascending dose levels of SBT-77-7101 in six participants across two cohorts. Importantly, investigators observed no dose-limiting toxicities, no cytokine release syndrome and no neurotoxicity.
By week 4, 67% of participants achieved a 50% or greater reduction in swollen and tender joint counts – an early clinical readout that matters to patients day to day. Additionally, 83% showed improvements on composite disease activity metrics, including DAS28-CRP (Disease Activity Score-28 using C-reactive protein) and CDAI (Clinical Disease Activity Index).
Signals of dose responsiveness are also emerging. Participants in the higher-dose cohort experienced deeper and more consistent responses, with one individual maintaining a durable effect through week 24.
Beyond symptom scores, the trial is capturing mechanistic evidence: CAR+ regulatory T cells (Tregs) were detected in both synovial tissue and peripheral blood, indicating activity at the site of disease as well as systemically – an encouraging sign for an antigen-directed Treg approach in autoimmunity.
The company’s Chief Scientific Officer called the preliminary safety, pharmacokinetic/pharmacodynamic and efficacy observations gratifying, arguing they help validate the potential of antigen-directed Tregs to treat autoimmune disease even in highly refractory patients with substantial baseline disease burden.
For a population often cycling through therapies with diminishing returns, the combination of early clinical improvement, biological on-target activity and a benign safety profile is precisely the blend of signals stakeholders hope to see at this stage.
Of course, these are interim, early-phase data from a small cohort, and the goals of a phase 1 trial centre on safety, dose finding and biological plausibility rather than definitive efficacy. Even so, the absence of acute safety concerns, the consistency of improvements across joint counts and composite indices, and the durability seen in at least one participant collectively set the stage for the next leg of development.
The pending completion of dose escalation – and the planned move into dose expansion – should provide a clearer view of the therapy’s potential breadth of benefit and inform future, larger studies powered to test clinical endpoints.
Conclusion
Presented in a late-breaking session at ACR Convergence 2025, Sonoma Biotherapeutics’ interim phase 1 results for SBT-77-7101 highlight encouraging safety, early efficacy signals and on-mechanism activity in refractory RA.
With no dose-limiting toxicities observed, meaningful week-4 improvements in joint counts and disease scores, deeper responses at higher doses, a durable effect through week 24 in one case, and CAR+ Tregs detected in both synovium and blood, the programme now advances toward dose expansion with cautious optimism and a clear rationale for continued study.
News Credits: Sonoma Biotherapeutics reports promising early data from phase 1 rheumatoid arthritis trial
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