CX13-608

Primary objective: To evaluate the overall response rate (ORR) after treatment with CX13-608 in subjects with multiple myeloma who have previously received alkylating agents or anthracyclines, bortezomib, and immunomodulatory agents (IMiDs), relapsed after 2 or more lines of therapy, and were refractory to the most recent therapy. The overall response rate (ORR) is defined as the proportion of subjects with a strict complete response (sCR), complete response (CR), very good partial response (VGPR), or partial response (PR). The ORR will be determined using the best overall response assessed by an independent review committee (IRC) according to the International Uniform Criteria for Multiple Myeloma (IMWG?URC). Secondary objectives: 1) ORR of CX13-608 treatment per cycle based on investigator assessment; 2) evaluate the clinical benefit rate (CBR, defined as the proportion of subjects whose best overall response was minimal response [MR] or better); 3) evaluate the duration of response (DOR); 4) evaluate the duration of clinical benefit (DCB); 5) evaluate progression-free survival (PFS); 6) evaluate overall survival (OS); 7) evaluate the time to response (TTR); 8) describe the pharmacokinetic (PK) characteristics of CX13-608.