Trial of an Investigational Drug After Rejecting the Relapse of an Allogeneic Transplant (CARTemis-1)

Inclusion Criteria: Patients > 18 years old with a diagnosis of post-allogeneic transplant relapse multiple myeloma. Measurable disease at the time of screening Previous treatment with ≥2 lines before and/or after allogeneic transplant. Patients who are not receiving immunosuppressants at least 1 month before inclusion and who do not have active graft-versus-host disease. Eastern Cooperative Oncology Group functional status from 0 to 1. Life expectancy greater than 3 months (at the time of screening) Patients who give their consent by signing the Informed Consent document. Exclusion Criteria: Active systemic immunosuppressive treatment Patients who have previously received treatment with CAR-T Anti-BCMA. Absolute lymphocyte count <0.2x109/L Previous neoplasm, except if it has been in complete remission >3 years, with the exception of skin carcinoma (non-melanoma) Active infection requiring treatment. Active HIV, hepatitis B virus or hepatitis C virus infection. Uncontrolled medical illness. Severe organic disease that meets any of the following criteria: left ventricular ejection fraction <40%, carbon monoxide diffusion test <40%, glomerular filtration rate <50 ml/min, bilirubin >3 normal value (except Gilbert syndrome). Previous diagnosis of symptomatic amyloid light chain or primary amyloidosis or POEMS Syndrome. Pregnant or lactating women. Women of childbearing age, unable or unwilling to use highly effective contraceptive methods. Men who cannot or do not wish to use highly effective contraceptive methods. Contraindication to receive lymphodepleting chemotherapy.