To assess the safety and efficacy of CARTBCMA ARI0002h in patients with relapsed/refractory multiple myeloma who have received treatment with proteasome inhibitor, immunomodulatory drug and anti-CD38 monoclonal antibody.

Inclusion Criteria:

• Patients between the age of 18 and 75 years with diagnosis of multiple myeloma
• Disease measurable by monoclonal component in serum and/or urine or by free light chains in serum according to the eligibility criteria for clinical trials of the International Myeloma Working Group
• Previous two or more lines of treatment. Patients must have received at least a proteasome inhibitor (such as bortezomib or carfilzomib), an immunomodulatory drug (lenalidomide or pomalidomide) and an anti-CD38 monoclonal antibody (such as daratumumab)
• Refractory to the last line of treatment
• ECOG functional status ranging from 0 to 2
• Life expectancy over 3 months
• Patients who, after being informed, give their consent by signing the Informed Consent document.

Exclusion Criteria:

• Previous allogeneic transplant in the prior 6 months to inclusion or GVHD that requires active systemic immunosuppressive treatment
• Absolute lymphocyte count <0.1x10^9/ L
• Previous neoplasia, except if patients have been in complete remission > 3 years, except for cutaneous carcinoma (non-melanoma)
• Active infection that requires treatment
• Active infection by HIV, HBV or HCV.
• Uncontrolled medical disease
• Severe organic condition that meets any of the following criteria: EF <40%, DLCO <40%, EGFR <50 ml / min, bilirubin> 3 times normal value (except Gilbert syndrome)
• Previous diagnosis of symptomatic AL amyloidosis
• Pregnant or lactating women. Women of childbearing age should have a negative pregnancy test in the screening phase
• Women of childbearing age, including those whose last menstrual cycle was in the year prior to screening, who cannot or do not wish to use highly effective contraceptive methods from the beginning until the end of the study.
• Men who cannot or do not wish to use highly effective contraceptive methods from the beginning to the end of the study.
• Contraindication to receive conditioning chemotherapy