Adicet Bio Announces Positive Phase 1 Prula‑cel Data in SLE/LN

What Happened
Adicet Bio (ACET) announced on September 28, 2026 positive preliminary Phase 1 results for prula‑cel (formerly ADI‑001) in patients with systemic lupus erythematosus (SLE) with or without lupus nephritis (LN). As of an August 28, 2026 cut‑off, 22 efficacy‑evaluable patients (16 LN, 6 extra‑renal SLE) were followed 6–21 months. Among evaluable LN patients at 12 months, 50% achieved a complete renal response (CRR) and 54% achieved DORIS remission; most 12‑month responses remained ongoing through 12–21 months. Safety across 24 dosed, safety‑evaluable patients showed no cytokine release syndrome (CRS) above Grade 2, Grade 1–2 CRS in 25%, no dose‑limiting toxicities, no IEC‑HS, no ICANS, and infections in 54% (Grade ≥3 in 8.3%). All patients discontinued background immunosuppressants and all but one tapered steroids to ≤5 mg prednisone equivalent. Biomarkers showed an “immune reset”: all 22 efficacy‑evaluable patients had undetectable CD19+ B cells followed by naïve‑dominant B‑cell reconstitution; anti‑dsDNA decreased in 91% (10/11) of baseline‑positive patients and complement recovered in 90% (9/10) with low baseline.

Key Details

• Filing date and disclosure: 8‑K filed Sept 28, 2026; press release and investor presentation furnished.
• Patients and follow‑up: 22 efficacy‑evaluable patients (16 LN, 6 non‑renal SLE); follow‑up 6–21 months.
• Efficacy: 50% CRR at 12 months (evaluable LN patients); 54% DORIS remission at 12 months.
• Safety & dosing: 24 safety‑evaluable dosed; no CRS > Grade 2; Grade 1–2 CRS in 25%; infections in 54% (Grade ≥3 = 8.3%); supports outpatient administration per FDA alignment.
• Regulatory path & timeline: Company aligned with FDA on a single‑arm pivotal LN study (primary endpoint: CRR at 12 months); start‑up activities expected Q4 2026; potential expansion to include non‑renal SLE subject to FDA discussions. Anticipated data milestones: SSc update H1 2027; LN/SLE update mid‑2027.

Why It Matters
This 8‑K signals that prula‑cel produced encouraging clinical responses and a manageable safety profile in a heavily pretreated SLE/LN population, and that Adicet is preparing a regulatory path toward a pivotal single‑arm LN study. For investors, the filing highlights potential near‑term program catalysts (pivotal start‑up in Q4 2026 and upcoming data readouts) and underscores key risks noted in the filing—results are preliminary and forward‑looking statements depend on further clinical, regulatory, and operational factors.