It is very simple. Recall that the MDM2 drugs got into trouble for immune suppression. Just review hematopoesis. How long does a neutrophil live? Days. The bone marrow produces billions of WBCs every day. If you give Kevetrin with a very short half life-HOURS- once a week then you gain some info about side effects but what about giving the same drug many times a week? Will there be any impact on WBC? Of course i do not know, but Dana Farber and Menon and Leo do not know either.
that is why of course that the additional dosing regimens were announced- to answer the question of side effects that might develop under different dose intervals.