This is a prospective, multicenter, open-label, single-arm study to assess the efficacy, safety, and pharmacokinetics (PK) of IgPro20 in adults with hematologic malignancies treated with B-cell targeting Chimeric antigen receptor T-cell (CAR T-cell) and T-cell redirecting therapies (such as T-cell engager bispecific antibody \[TCE BsAb\] therapy). The primary objective is to demonstrate that true annualized rate of serious bacterial infection (SBIs) is less than (\<) 1.0.
This study includes two cohorts:
1. Loading Cohort: Participants with serum immunoglobulin G (IgG) \< 500 milligrams per deciliter (mg/dL) at Screening, with or without ongoing immunoglobulin replacement therapy (IgRT) during Screening, who must have received five doses of IgPro20 during the Initial Treatment Period. 2. Maintenance-only Cohort: Participants with serum IgG greater than or equal to (≥) 500 mg/dL and ongoing IgRT at Screening, who must have received one dose of IgPro20 during the Initial Treatment Period.
Participants greater than or equal to (≥) 18 years of age at the time of providing written informed consent.
Confirmed diagnosis of B-cell hematologic malignancy (ie, Multiple myeloma [MM], Chronic lymphocytic leukemia [CLL], Non-Hodgkin lymphoma [NHL], or BALL) according to applicable diagnostic criteria.
At least 2 months after receipt of an approved CAR T-cell therapy for the B-cell hematologic malignancy at the time of Screening, or
At least 1 month after initiation of an approved TCE BsAb therapy for the B-cell hematologic malignancy at the time of Screening and expected to continue with the therapy.
Documented history of diseases for which IgRT may be indicated: primary immune deficiency, chronic inflammatory demyelinating polyneuropathy, Guillain-Barré syndrome, immune thrombocytopenia, Kawasaki disease, Lambert-Eaton myasthenic syndrome, multifocal motor neuropathy, myasthenia gravis, stiff person syndrome, solid organ transplant, and rejection prior to Screening.
History of thromboembolic event (TEE) within 6 months before Screening.
Eastern Cooperative Oncology Group performance status > 1.
Presence of any systemic active infection at Screening.