A Safety Study of SGN-CD48A in Patients With Multiple Myeloma

This study is designed to evaluate the safety, tolerability, and antitumor activity of SGN-CD48A in patients with relapsed or refractory multiple myeloma. This study will be conducted in 2 parts: 1. Dose escalation: This part will evaluate increasing doses of SGN-CD48A to identify the maximum tolerated dose. The first group of patients enrolled on the study will receive the lowest dose of SGN-CD48A. Once this dose is shown to be safe, a second group of patients will be enrolled at the next higher dose. Patients will continue to be enrolled in groups receiving increasing doses until the maximum tolerated dose level is reached. Patients can only be enrolled into a higher dose level once the lower doses have been demonstrated safe. Dose escalation will be conducted using a modified toxicity probability interval (mTPI) study design. 2. Dose expansion: This part will further evaluate the safety, tolerability, and antitumor activity of up to 2 dose levels of SGN-CD48A shown to be safe in the first part of the trial.