Cartesian Therapeutics Reports Positive Phase 2 Data for mRNA CAR-T in Lupus

REDERICK, Md. – November 14, 2025 — Cartesian Therapeutics, Inc. (NASDAQ: RNAC), a clinical-stage biotechnology company pioneering cell therapy for autoimmune diseases, announced positive initial data from its ongoing Phase 2 open-label trial of Descartes-08 in patients with systemic lupus erythematosus (SLE).

Descartes-08, Cartesian’s lead cell therapy candidate, is an autologous anti-B cell maturation antigen (BCMA) chimeric antigen receptor T-cell therapy (CAR-T). The manufacture of this next-generation CAR-T uses mRNA to transiently express the receptor, allowing for outpatient administration without the need for lymphodepleting chemotherapy.

mRNA CAR-T Shows Efficacy and Favorable Safety in Lupus

The Phase 2 trial evaluated the outpatient administration of Descartes-08—an mRNA-engineered cell therapy—in patients with moderate or severe SLE refractory to immunosuppressants.

Key initial efficacy findings (n=3 patients reaching Month 3 follow-up) demonstrated:

• 100% achieved Lupus Low Disease Activity State (LLDAS) response, indicating low disease activity and sustained symptom improvement.
• Disease remission (DORIS response) was seen in 2 out of 3 participants at Month 3.

“The responses observed in all participants reaching Month 3 follow-up to date in the ongoing Phase 2 SLE trial serves as strong validation for our proprietary platform technology and supports the potential of Descartes-08 to expand the reach of cell therapy for the treatment of autoimmune diseases,” said Carsten Brunn, Ph.D., CEO of Cartesian.

The mRNA CAR-T continued to show a favorable safety profile. Notably, there were no cases of cytokine release syndrome (CRS) or immune effector cell-associated neurotoxicity syndrome (ICANS), supporting the use of the mRNA platform for outpatient administration without preconditioning chemotherapy. Correlative biomarker data also showed a statistically significant decrease in proinflammatory cytokines and plasmacytoid dendritic cells (pDCs).

Prioritization Shift to Myositis and Phase 3 MG

Following the positive efficacy and safety data, Cartesian announced a strategic decision to pause further enrollment in the SLE Phase 2 trial and development of Descartes-15 (a next-generation mRNA CAR-T) in multiple myeloma. The Company will prioritize opportunities for Descartes-08 in:

• Myasthenia Gravis (MG): Currently in the Phase 3 AURORA trial.
• Myositis: A significantly underserved market.

The Company plans to initiate a seamless adaptive clinical trial design in myositis, offering the potential for a single pivotal trial, planned to commence in the first half of 2026. This randomized, double-blind, placebo-controlled Phase 2 trial is expected to enroll up to 50 patients with multi-refractory dermatomyositis and antisynthetase syndrome. The Company expects to file the IND for this trial by the end of 2025.

The shift in focus to the Phase 3 MG and the planned Myositis trial is expected to extend the Company’s current cash runway through mid-2027.