A clinical trial to learn about the long-term safety of FUB523 (zigakibart) in people with immunoglobulin A (IgA) nephropathy who have completed previous zigakibart trials

Prior treatment

• Participants who at the time of first study treatment administration in the OLE are receiving chronic dialysis (≥ 30 days) or who require kidney transplantation.
• Received a live vaccination within 12 weeks prior to first study treatment administration in the OLE study or plan to have a live vaccination within 6 months after the last dose of study treatment.
• Use of systemic corticosteroid therapy (including budesonide) or other immunosuppressive therapy such as but not limited to mycophenolate, azathioprine, cyclosporine, tacrolimus, cyclophosphamide, etc., and herbs such as Tripterygium Wilfordii Hook F, Caulis sinomenii, and Sinomenium acutum for > 2 weeks in the 12 weeks prior to first study treatment administration in the OLE study; use of rituximab within 180-days of first study treatment administration in the OLE study.

Other illness

• Current severe infection at the time of first study treatment in the OLE study or history of recurrent, severe, infections as determined by the Investigator.
• Newly diagnosed positive serology for hepatitis A virus IgM antibodies (anti-HAV IgM), hepatitis B surface antigen (HBsAg), detectable hepatitis B virus (HBV) DNA, hepatitis C virus (HCV) antibodies (participants who completed treatment and are persistently antibody positive but have documentation of negative HCV polymerase chain reaction [PCR] will be allowed), or antibodies to HIV-1 and/or HIV-2.
• Newly diagnosed malignancy (participants with basal cell carcinoma that was completely resected or curatively treated cervical carcinoma in situ or low-risk prostate cancer (i.e., Gleason score < 7 and prostate specific antigen < 10 ng/mL) are eligible for the study).

Lab values

• History or evidence of any other clinically significant medical or psychiatric disorder, condition, disease, or laboratory finding that, in the discretion of the Investigator, constitutes an uncertain or unfavorable benefit-risk for continued long-term therapy with zigakibart.
• Confirmed IgG levels < 3 g/L prior to first study treatment administration in the OLE study.

Age

• Women of child-bearing potential, defined as all women physiologically capable of becoming pregnant, from menarche until becoming post-menopausal unless they are using highly effective methods of contraception (failure rate < 1% per year) while taking study treatment and for 24 weeks after stopping study treatment. Women are considered post-menopausal if they have had 12 months of natural (spontaneous) amenorrhea with an appropriate clinical profile (e.g., hormonal profile confirming menopause and/or age-appropriate history of vasomotor symptoms).

Other

• Participants who prematurely withdrew from zigakibart parent studies in IgAN for any reason
• Pregnancy or breastfeeding or intent to become pregnant or to donate sperm during the study period and until 24 weeks after last dose.
• Sexually active males unwilling to use a highly effective methods of contraception during intercourse while taking study treatment and for 24 weeks after stopping study treatment. In addition, male participants must not donate sperm for the time period specified above.
• Acute kidney injury (AKI), defined by AKIN criteria (Mehta et al 2007) within 4 weeks of first study treatment administration in the OLE study.
• Clinical suspicion or diagnosis of rapidly progressive glomerulonephritis (RPGN), defined by KDIGO guidelines, or another glomerulopathy at the time of first study treatment administration in the OLE study.

• Signed informed consent must be obtained prior to participation in the OLE study.
• Completion of the parent study (both participants assigned to receive the investigational product and placebo) as defined by the respective protocol
• Per Investigator’s clinical judgment, the participant may benefit from receiving open-label treatment of zigakibart 600 mg s.c. Q2W.