A clinical proof of concept study (Clinicaltrials.gov identifier: NCT0302577) was designed to study the effects of reducing the levels of γ-secretase cleaved soluble BCMA in MM patients by using a γ-secretase inhibitor because soluble BCMA interferes with the mechanism of action of BCMA-targeting bispecific antibodies. This evidence concerns the gene TNFRSF17 and Miyoshi myopathy.