Supporting Weak Immune System During Autoimmune Therapy: Testing Panzyga to Prevent Infections

Inclusion Criteria: Patients who meet all of the following criteria will be eligible to participate in the study: 1. Are ≥18 years of age at time of informed consent, have been diagnosed with a rheumatic or autoimmune condition, received their last BCDT dose within 3 months of Screening, and have the intention to receive BCDT during study participation. Note: Patients with the following indications are eligible: MS, RA, vasculitis/myositis, SLE, SS, IIM, MCTD, UCTD, myasthenia gravis, autoimmune encephalitis, CIDP, and neuromyelitis optica spectrum disorder). Other rheumatic and autoimmune conditions may also be acceptable with approval from the Medical Monitor. 2. Have hypogammaglobulinemia (IgG levels \<5 g/L as confirmed by the central laboratory). 3. Are willing and able to provide voluntary written informed consent for participation in the study and to comply with all protocol requirements.. 4. Are willing and able to comply with a highly effective contraception method during and for 30 days after the treatment period. Contraceptive use by men and women of childbearing potential should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies. Exclusion Criteria: Patients who meet any of the following criteria will be excluded from participation in the study: 1. Have a history of anaphylaxis or severe systemic response to immunoglobulin, blood, or plasma-derived products, or any Panzyga component 2. Have a current major infection at Screening or had \>1 major infection within 6 months prior to Baseline 3. Have a history of thromboembolic events such as deep vein thrombosis, pulmonary embolism, myocardial infarction, ischemic stroke, transient ischemic attack, or peripheral artery disease (Fontaine IV) within 6 months prior to Baseline 4. Have a known IgA deficiency with antibodies to IgA 5. Have a known blood hyperviscosity or other hypercoagulable states 6. Have been diagnosed with primary immunodeficiency. 7. Have a severe liver disease, with signs of ascites or hepatic encephalopathy 8. Have a severe kidney disease (as defined by eGFR \<30 mL/min/1.73 m2) 9. Have a body weight \>140 kg 10. HIV infection at Screening (defined for the study as positive HIV NAT test or reactive HIV- 1/2 antigen/antibody immunoassay followed by positive HIV-1/HIV-2 antibody differentiation immunoassay) 11. Patients found to be chronic carriers of hepatitis B virus (HBV), defined by positive surface antigen (HBsAg), positive Hepatitis B core antibodies (HBcAb) and/or low HBV titers, who will not receive targeted antiviral therapy while participating in the study, and patients with active HBV, defined as high HBV titers. 12. Uncontrolled hepatitis C infection at Screening (defined for the study as positive HCV PCR). 13. Have received IgG treatment within 6 months prior to Screening or plan to receive IgG therapy, other than IMP, during the study 14. Are receiving or plan to receive immunosuppressive treatment (other than for underlying condition) or other forbidden medication during the entire study duration 15. Are participating or plan to participate in another study that is either blinded or involves an investigational medicinal product within 3 months prior to Baseline or during the course of this study. Participation in observational or open-label studies involving an approved product may be permitted after consultation with the Medical Monitor. 16. If female, are pregnant or lactating 17. Are likely to be non-compliant or uncooperative during the study, or unable to cooperate because of a language problem or poor mental development, in the opinion of the Investigator