Splenic irradiation within the last 6 months History of prior or current splenectomy or splenic irradiation Splenic irradiation within 12 months prior to screening, or prior splenectomy. History of or current immunodeficiency disease, splenectomy or splenic irradiation Splenic irradiation within 3 months prior to the first dose of study drug History of or plan for splenectomy or splenic irradiation Splenic irradiation within 3 months prior to Randomization Splenic irradiation 3 months prior to enrollment. At least 6 months from prior splenic irradiation History of or current immunodeficiency disease (e.g. splenectomy or splenic irradiation) Splenic irradiation within 3 months prior to the first dose of MMB Phase 2 Part: Patients who have had prior splenectomy or have had splenic irradiation within 3 months of starting study drug