A Study of Gammagard Liquid (Immune Globulin Infusion, 10%) to Prevent Infections in Adults With Multiple Myeloma

Prior treatment

• The participant has a current serious infection or greater than (\>) 1 serious infection in the past 3 months before screening.
• The participant is currently receiving immunoglobulin products or has received immunoglobulin products within 16 weeks before screening.
• The participant has received a hyperimmune or specialty high-titer immunoglobulin product (example, cytomegalovirus immune globulin, varicella-zoster immune globulin, hepatitis B immune globulin) within 30 days before screening.
• The participant has received live viral vaccines within 30 days before screening.
• The participant has an active viral or bacterial infection or symptoms/signs of such an infection requiring treatment with anti-infectives within 1 week before enrollment.
• The participant has received other B Cell Maturation Antigen (BCMA)\*Cluster of Differentiation (CD3)-directed Bispecific Antibody therapy (BsAb), BCMA-targeted chimeric antigen receptor T-cell (CAR T-cell), or BCMA-targeted antibody drug conjugate (ADC) therapy within 1 year prior to screening.
• The participant is scheduled to undergo plasmapheresis during the course of study or has undergone plasmapheresis in the last 16 weeks before screening.
• The participant has major surgery scheduled during the study, or the participant has not fully recovered from a recent major surgery (as judged by the investigator) during screening (participants with planned surgical procedures to be conducted under local anesthesia may participate).
• The participant has a known history or current diagnosis of thromboembolic episodes such as deep vein thrombosis, pulmonary embolism, myocardial infarction, ischemic stroke, transient ischemic attack, peripheral artery disease within 6 months before screening.
• The participant has a documented diagnosis of a form of primary immunodeficiency (PID) involving a defect in antibody formation and requiring IgG replacement, as defined according to the International Union of Immunological Societies Committee.
• Known substance abuse including opiates, psychostimulant agents, or other illicit drugs with the exception of cannabinoids within 12 months of screening.
• The participant is receiving immunosuppressive treatment (other than for MM or corticosteroids) at screening or plans to receive immunosuppressive treatment after study enrollment.
• The participant has participated or is scheduled to participate in another clinical study involving an investigational product (IP) or investigational device within 30 days before screening and during the course of the study.

Other illness

• The participant may be excluded from the study if, in the opinion of the investigator, the participant is at high risk for symptomatic hyperviscosity syndrome.
• The participant has an active secondary (non-MM) malignancy or other medical condition with life-expectancy of less than (\<) 2 years.
• The participant has moderate to severe renal dysfunction based on an estimated glomerular filtration rate less than (\<) 30 milliliters per minute per 1.73 square meters (mL/min/1.73 m\^2), as defined by kidney disease: Improving Global Outcomes Clinical Practice Guideline for the Management of Glomerular Diseases, 2021 at the time of screening.
• The participant has a known history of or is positive at screening for one or more of the following: hepatitis B surface antigen, Polymerase Chain Reaction (PCR) for hepatitis C virus, PCR for Human Immunodeficiency Virus (HIV) Type 1 and Type 2. Cured participants with a history of hepatitis C infection who have a negative PCR test at screening are eligible.
• Participant with a known systemic hypersensitivity to any of the excipients of IGI, 10% in accordance with the investigator's brochure/package insert/Summary of Product Characteristics.

Lab values

• The participant has a documented polyclonal IgG level less than (\<) 150 milligrams per deciliter (mg/dL) at the most recent assessment before teclistamab initiation (within 4 weeks) as assessed by the investigator according to the site's standard practice.
• The participant has a known history of hypersensitivity or persistent reactions (urticaria, breathing difficulty, severe hypotension, or anaphylaxis) after Intravenous Immunoglobulin (IVIG) and/or immune serum globulin infusions.
• The participant has a persistent serum aspartate aminotransferase and alanine aminotransferase \>3.0 times the upper limit of normal (ULN) at screening (may be repeated once to determine if it is persistent).
• The participant has an immunoglobulin A (IgA) deficiency (\<0.07 grams per liter \[g/L\]) with antibodies to IgA and a history of hypersensitivity reaction to IVIG.
• The participant has anemia that would preclude phlebotomy for laboratory studies, according to standard practice at the site, at the discretion of the investigator (may be repeated once to determine if it has resolved).
• The participant has a medical condition, laboratory finding, or physical examination finding that precludes participation or with clinical evidence of any significant acute or chronic disease that, in the opinion of the investigator, may interfere with the successful completion of the study or place the participant at undue medical risk.

Other

• The participant has not achieved at least a minimal response to teclistamab during the screening period after signing the ICF and within 8 weeks of the first step-up dose of teclistamab.
• The participant has an Eastern Cooperative Oncology Group performance status score of \>2.
• The participant is not willing and able to comply with the protocol requirements.
• The participant is a family member or employee of the investigator or the investigator's site staff.
• The participant is pregnant or has a positive pregnancy test or is lactating at the time of screening or enrollment.

• The participants must have a documented diagnosis of Multiple Myeloma (MM) according to the guidelines by the International Myeloma Working Group (IMWG) before enrollment.
• Participant who recently started teclistamab monotherapy within the first 8 weeks of their planned treatment schedule and are planned to receive teclistamab for the next 12 months.
• The participant has provided informed consent (that is, in writing, documented via a signed and dated Informed Consent Form \[ICF\]) and any required privacy authorization before the initiation of any study procedures.
• The participant is at least 18 years of age at the time of signing the ICF.
• If a person of childbearing potential engages in sexual relations that carry risk of pregnancy, they agree to the following for the period from screening until 30 days after the last dose of study drug:
  • To use a highly effective contraceptive method.
  • To avoid donating ova.