CD28 and plasma cell myeloma: Moreover, the reduced nonspecific activity of IgG4 potentially improves the safety of IgG-like bsAbs, and the recent CD38/CD3/CD28 tsAb developed by Sanofi efficiently induces myeloma growth suppression and T-cell stimulation 19; however, we did not expect timely cessation of the potential toxic activity due to the prolonged half-life.