CD9 and plasma cell myeloma: One is a phase I clinical trial assessing the safety and efficacy of KBA1412 human monoclonal antibody targeting CD9 in patients with advanced solid tumors (NCT05501821), and the other one is the cell therapy approach based on CT0594CP, that combines CAR-T cells targeting BCMA and CD9 in patients with relapsed and/or refractory multiple myeloma or plasma cell leukemia (NCT05822037).