Study of IgPro20 to Prevent Infection in People With Multiple Myeloma and Hypogammaglobulinemia

The main purpose of this study is to see if IgPro20 can prevent infection in people with multiple myeloma (MM) who have hypogammaglobulinemia from receiving bispecific monoclonal antibodies (BsAbs).

Inclusion Criteria: * Diagnosis of RRMM receiving a commercially available bispecific antibody * Received at least 1 but no more than 4 cycles of BsAb * Males or females greater than or equal to 18 years old at the time of consent * ECOG ≤ 3 * Life expectancy \> 12 months Exclusion Criteria: * HSCT within 3 months before enrollment * Planned CAR-T therapy in the next 6 months * \>1 major (deep-seated) infection within the preceding 3 months * HIV infection, Active HCV, or Active HBV infection * Pregnancy * Neutrophils \< 500 x 10\^3 per mL, Platelets \< 30 x 10\^9 per mL * History of cancer other than MM in the last 3 years requiring active chemotherapy or radiation * Known reaction/allergy to IgG products * Intracranial hemorrhage or embolic CVA in the last 6 months * Hyperproteinemia * Protein-losing enteropathy * Creatinine Cl \