Hello Carol, what an awful situation to be in.
If I was faced with this I would seek advice from Brian Durie of the International Myeloma Foundation. Other possible sources of information (but which may need your husband to upload all of his medical history) are Healthtree (Myeloma Crowd) and Tony Blau at All4Cure. (He is a haematologist with myeloma).Both of these are myeloma patient databases which aim to help identify treatments which have been successful in patients with similar myelomas.
I know another patient who is in a similar predicament to your husband has just started Blenrep as compassionate use although it’s not NICE approved yet. His consultant had to go through a few hoops for this, but GSK the pharma company are supplying it, I believe without charge. Myeloma UK may know more about getting drugs under this scheme so that you could then ask the doctor to pursue this, and myeloma UK should also know if there are any suitable trials underway yet.
Please do let me know how you & your husband get on. Thinking of you
Jane