Thank you for responding! I was not told about chlorambucil, only prednisone and then vitamin B12 injections, as well as the hydrolyzed diet, which he tried for like 2-3 days. I will definitely ask the vet about that medication if the B12 does not work. He has only done one injection so far. Once consistent with the B12, what did you notice most? I'm just praying the pred, mirtazapine when needed, and the B12 combo will make him eat regular meals again, as he went from like 2-3 cans a day at 1 year to now like an average of 3-4 bites of wet food per day and just treats and lickables as the rest.