Hi mf1,
I should provide a bit more detail.
There are currently two bispecific antibody treatments which have been approved in the UK: Elranatamab and Teclistamab. They are similar in that they both target part of a myeloma cell called BCMA. Therefore the side effects are broadly similar.
A third bispecific antibody may be approved soon, called Talquetamab. This targets a completely different part of a myeloma cell called GPRC5D. The side effects are therefore pretty different.
Other bispecific antibody treatments are in development. You haven’t provided detail, so for all I know your husband may be going into a clinical trial for one of these.