GPRC5D and Miyoshi myopathy: To define the frequency of antigen loss before therapy initiation and at the time of relapse after targeted CAR T or TCE therapy, we assembled a cohort of 40 patients who had relapsed refractory MM (RRMM) treated with anti-BCMA CAR T and/or anti-BCMA and/or anti-GPRC5D TCE therapy, or other non-anti-BCMA/GPRC5D salvage therapies (patients who were anti-BCMA/GPRC5D naive) (Extended Data Fig. 1).