Study of SIM0500 Alone in Participants With Relapsed or Refractory Multiple Myeloma

This is an early-phase study testing a new drug called SIM0500 in people with relapsed or refractory multiple myeloma (a blood cancer in the bone marrow) who have already tried all available standard treatments without success. **You may be eligible if...** - You are 18 or older with a confirmed diagnosis of multiple myeloma - Your myeloma has come back or stopped responding to all standard treatments - Your overall health status is adequate (ECOG 0 or 1) - Your blood counts and organ function meet minimum thresholds - Your life expectancy is at least 12 weeks **You may NOT be eligible if...** - You have active hepatitis B or C - You have side effects from prior treatments that have not resolved to mild levels (Grade 1 or less) - You have had certain prior therapies or conditions that conflict with this study Talk to your doctor to see if this trial is right for you.