FDA Grants RMAT Designation to Allogeneic CAR T for R/R Multiple Myeloma

The FDA has granted regenerative medicine advanced therapy (RMAT) designation to CB-011, an allogeneic anti–B-cell maturation antigen (BCMA) chimeric antigen receptor (CAR) T-cell therapy for the treatment of relapsed or refractory multiple myeloma (R/R MM).¹ The designation is based on promising early clinical data from the ongoing CaMMouflage phase 1 trial (NCT05722418).

Clinical Efficacy

The FDA’s decision was supported by data from the 12-patient cohort of anti-BCMA therapy–naive patients treated at the recommended dose for expansion (RDE) of 450 × 10⁶ CAR T cells in the dose-escalation phase. As of the September 24, 2025, data cutoff, this cohort demonstrated a 92% overall response rate (ORR), a rate of complete response (CR) or better of 75%, and minimal residual disease (MRD) negativity in 91% of evaluable patients. One patient had a stringent CR maintained at 15 months postinfusion as of this follow-up.

These results represent a clinically meaningful signal in a patient population with significant unmet need.

Among all 48 patients treated, CB-011 has demonstrated a manageable safety profile across all dose levels evaluated. No cases of graft-vs-host disease, immune effector cell–associated enterocolitis, parkinsonism, or cranial nerve palsies were observed. Among the 35 patients treated with the selected cyclophosphamide/fludarabine lymphodepletion regimen, the most common treatment-emergent adverse events were neutropenia (80%), anemia (60%), thrombocytopenia (49%), infections (49%), dizziness (31%), and cytokine release syndrome (31%).

RMAT Designation Addresses Unmet Need

RMAT designation is intended to expedite the development and regulatory review of regenerative medicine therapies that address unmet medical needs in serious conditions. It confers eligibility for priority and rolling reviews, as well as potential accelerated approval. CB-011 previously received fast track and orphan drug designations from the FDA for R/R MM in 2023, underscoring the agency’s recognition of the critical gap in treatment access for this patient population.²

“The FDA’s RMAT designation for CB-011 recognizes both the significant unmet need in multiple myeloma and the encouraging clinical data we have seen so far in the CaMMouflage trial,” Tina Albertson, MD, PhD, chief medical officer at Caribou Biosciences, stated in a news release.¹

Allogeneic Approach Promotes CAR T Access

Access to CAR T-cell therapy remains a profound barrier in myeloma care.

“Only 1 in 10 people with multiple myeloma in the US are able to receive CAR T-cell therapies due to long wait times and manufacturing limitations,” Adriana Rossi, MD, director of the CAR T and stem cell transplant clinical program at the Center of Excellence for Multiple Myeloma at Mount Sinai and an investigator on the CaMMouflage trial, stated in a news release.

CB-011 is designed as an off-the-shelf, allogeneic product intended to address these limitations. It incorporates a B2M knockout and insertion of a B2M–HLA-E fusion protein to blunt immune-mediated rejection and enable successful allogeneic cell therapy. It was engineered from healthy donor-derived T cells and modified with 4 genomic alterations using Cas12a CRISPR hybrid RNA-DNA technology.³

Trial Design and Next Steps

The CaMMouflage trial (NCT05722418) is a multicenter, open-label phase 1 study enrolling adults with R/R MM who have received 3 or more prior lines of therapy. The dose-escalation phase enrolled 48 patients across multiple dose levels and 2 lymphodepletion regimens. The ongoing dose expansion phase is evaluating CB-011 at 450 × 10⁶ CAR-T cells in both anti-BCMA therapy–naive and –exposed cohorts with a lymphodepletion regimen of 500 mg/m² cyclophosphamide and 30 mg/m² fludarabine daily for 3 days.¹

Caribou Biosciences, the sponsor, anticipates reporting initial dose expansion data and longer follow-up from the dose-escalation cohort in 2026. The company also plans to initiate discussions with the FDA regarding the future clinical development pathway for CB-011.

REFERENCES

1. Caribou Biosciences Announces the FDA Granted Regenerative Medicine Advanced Therapy (RMAT) Designation to CB-011, an Allogeneic Anti-BCMA CAR-T Cell Therapy. News release. Caribou Biosciences. March 31, 2026. Accessed April 1, 2026. https://tinyurl.com/2nydsybh

2. Caribou Biosciences announces FDA granted fast track designation to CB-011, an allogeneic CAR-T cell therapy for relapsed or refractory multiple myeloma. News release. Caribou Biosciences. April 4, 2023. Accessed April 1, 2026. https://tinyurl.com/36n5fkyy

3. Degagné É, Donohoue PD, Roy S, et al. High-specificity CRISPR-mediated genome engineering in anti-BCMA allogeneic CAR T cells suppresses allograft rejection in preclinical models. Cancer Immunol Res. 2024;12(4):462-477. doi:10.1158/2326-6066.CIR-23-0679