Adicet Bio Reports Positive Prula-cel Phase 1 Lupus Data as Pivotal Study Plans Advance

Adicet Bio (NASDAQ:ACET) reported 12-month DORIS remission in 54% of evaluable systemic lupus erythematosus patients and complete renal response in 50% of evaluable lupus nephritis patients, supporting plans to begin pivotal study start-up activities in the fourth quarter of 2026.

Key Investor Takeaways

• Adicet Bio (NASDAQ:ACET) reported positive prula-cel Phase 1 lupus data from 22 efficacy-evaluable patients, including 16 with lupus nephritis and six with extra-renal SLE.
• At 12 months, 54% of evaluable patients achieved DORIS remission, while 50% of evaluable lupus nephritis patients achieved complete renal response.
• All patients discontinued immunosuppressants, while all but one reduced background steroids to no more than 5 mg of prednisone equivalent per day.
• Among 24 safety-evaluable patients, there were no cases of CRS above Grade 2, IEC-HS, ICANS, dose-limiting toxicities or graft-versus-host disease.
• Adicet plans to initiate pivotal lupus nephritis study start-up activities in the fourth quarter, with potential inclusion of SLE patients without nephritis subject to further FDA alignment.

Why ACET Stock Is in Focus

Adicet Bio released updated Phase 1 results for prulacabtagene leucel, or prula-cel, its investigational allogeneic CAR-T therapy targeting B cells through an anti-CD20 CAR.

The August 28 data cut included 22 efficacy-evaluable patients followed for between six and 21 months. Thirteen had reached at least 12 months of follow-up. The population was heavily pretreated, with every patient having received at least three prior therapies and 71% receiving four or more.

At 12 months, 54% of evaluable patients achieved DORIS remission. Among evaluable patients with lupus nephritis, 50% achieved complete renal response. Adicet said the 12-month responses remained ongoing through 12 to 21 months of follow-up except in one patient, who had a UPCR of 0.65 g/g and remained off immunosuppressants.

Mean SLEDAI-2K and Physician’s Global Assessment scores declined rapidly and remained lower during follow-up. Among patients reaching 12 months, 85% recorded a PGA score below 0.5.

All 22 efficacy-evaluable patients achieved undetectable CD19-positive B cells followed by naïve-dominant B-cell reconstitution. Anti-dsDNA antibodies declined in 10 of 11 baseline-positive patients, while nine of 10 patients with low baseline complement experienced complement recovery.

Why This Matters for Investors

The clinical response data move prula-cel closer to a potential pivotal-stage programme in lupus nephritis. Adicet said it has aligned with the FDA on a single-arm study enrolling lupus nephritis patients who have had an inadequate response to at least two immunosuppressants.

The planned study is expected to enroll a double-digit number of patients, with complete renal response at 12 months serving as the primary efficacy endpoint. This provides investors with a defined regulatory development pathway and an endpoint against which future results can be assessed.

Safety is another important consideration for the programme. Among 24 safety-evaluable patients, Grade 1 or 2 cytokine release syndrome occurred in 25%, but there was no CRS above Grade 2. Infections occurred in 54%, including Grade 3 or higher infections in 8.3%. No IEC-HS, ICANS, dose-limiting toxicities or graft-versus-host disease were reported.

Adicet said its alignment with the FDA supports outpatient administration. If maintained in larger studies, the combination of an off-the-shelf allogeneic approach and outpatient administration could affect how prula-cel is positioned operationally, although the current findings come from an early-stage study with a limited patient population.

The discontinuation of immunosuppressants across all patients is also relevant to the treatment profile being investigated. However, durability and reproducibility of remission will require assessment with longer follow-up and additional patients.

What to Watch Next

Adicet plans to begin pivotal lupus nephritis study start-up activities during the fourth quarter of 2026. The company also intends to discuss with the FDA whether patients with lupus without nephritis can be included in the pivotal programme, with any expansion subject to regulatory alignment.

The next scheduled clinical readouts include a systemic sclerosis update in the first half of 2027 and further lupus nephritis/SLE data around mid-2027.

For the lupus programme, the main measures to watch will be durability of DORIS remission and complete renal responses, the safety profile as patient numbers increase, and the final design and patient population for the pivotal study.

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