Adicet Bio (ACET) Study update summary

Study design and patient population

• Phase 1 basket study evaluated prula-cel in 24 lupus patients (16 with nephritis, 8 with non-nephritis/extra-renal SLE), all heavily pre-treated, with most having at least three prior therapies and a mean age of 35.

• All patients had inadequate responses to at least two or three prior immunosuppressants; 71% had four or more prior therapies.

• Single infusion was administered after lymphodepletion, with safety and efficacy assessments up to 24 months.

• 22 patients were efficacy-evaluable and 24 were safety-evaluable as of August 28, 2026.

• All patients discontinued immunosuppressants, and all but one tapered steroids to ≤5 mg prednisone equivalent per day.

Efficacy results

• At 12 months, 50% of lupus nephritis patients achieved complete renal response (CRR), and 54% of evaluable patients achieved DORIS remission, with responses ongoing up to 21 months.

• Rapid and sustained reductions in SLEDAI and Physician Global Assessment scores were observed, with 85% of patients achieving a PGA score below 0.5 at 12 months.

• 21 of 22 efficacy-evaluable patients remained off immunosuppressants throughout the study.

• Additional 20% of nephritis patients had at least 50% reduction in proteinuria (partial renal response).

• All but one patient tapered steroids to ≤5 mg prednisone equivalent.

Safety profile

• Prula-cel was generally well-tolerated: no dose-limiting toxicities, no IEC-HS, no ICANS, and no CRS above Grade 2.

• Grade 1/2 CRS occurred in 25% of patients; infections occurred in 54%, with Grade 3 or higher in 8.3%.

• No cases of GvHD; safety profile consistent across broader autoimmune cohorts.

• Favorable safety profile attributed to gamma delta T-cell biology and differentiated cytokine profile.

• Safety data enabled FDA alignment for outpatient dosing.