This study focuses on a new medicine for people with relapsed (came back) or refractory (not responding) multiple myeloma, a type of blood cancer. The goal is to compare how the body absorbs and processes two versions of the same medication, teclistamab, made differently. To join, participants must have multiple myeloma, tried 1 to 3 other treatments, and show disease progression. They will need to have blood tests and may undergo other medical checks to ensure safety. Some people cannot participate, such as those who had certain vaccines or treatments recently, or those with brain involvement of their myeloma.

• The study may involve multiple visits and medical tests.
• Participants may receive compensation for their time and travel.
• Potential risks include side effects from the medication or procedures.