A Study of MBS314 in Participants With Relapsed/Refractory Multiple Myeloma.

"Phase Ia: The patients confirming to the eligibility criteria will be assigned to 1 of the 7 dose groups (0.03/0.09/0.3/0.9 mg \~ 0.3/1.5/9.0/60 mg, respectively) based on the sequence of inclusion. Each patient will receive MBS314 as per the schedule specified in the respective arms.~Phase Ib/Ⅱ: Based on the results of Phase Ⅰa, 1 or 2 recommended doses will be selected for Phase Ⅰb. Recommended Phase II Dose (RP2D) will be selected for Phase Ⅱ."