A Study of YKST02 in Participants With Primary IgA Nephropathy

Prior treatment

• Requirement for systemic corticosteroids for concomitant conditions
• Use of immunosuppressive, targeted, or biologic therapies within a defined period prior to screening or anticipated use during the study
• Prior treatment with B-cell-depleting or other targeted biologic therapies within a defined period
• Clinically significant cardiovascular or cerebrovascular disease within 6 months prior to screening
• Major surgery within 4 weeks prior to screening or planned during the study
• Receipt of another investigational product within 4 weeks or 5 half-lives (whichever is longer) prior to screening
• Receipt of live or attenuated vaccines within 4 weeks prior to screening or planned during the study

Other illness

• Secondary IgA nephropathy (e.g., associated with liver disease, autoimmune disorders, infections, or other systemic conditions)
• Other clinically significant renal diseases unrelated to IgAN (e.g., diabetic nephropathy, lupus nephritis, vasculitis)
• Nephrotic syndrome considered unsuitable for study participation
• History of demyelinating disorders (e.g., multiple sclerosis)
• History of organ transplantation or planned transplantation during the study
• Active infection requiring systemic therapy, recent serious infection, or chronic/recurrent infections
• Known active hepatitis B, hepatitis C, or human immunodeficiency virus (HIV) infection
• Active or untreated latent tuberculosis
• History of splenectomy
• Uncontrolled comorbidities (e.g., poorly controlled hypertension or diabetes)
• Malignancy within the past 5 years, except adequately treated non-invasive cancers
• Known hypersensitivity to YKST02 or its components
• Any condition that, in the investigator's judgment, would make the participant unsuitable for the study

Lab values

• Estimated glomerular filtration rate (eGFR) \<45 mL/min/1.73 m²
• Clinically significant abnormal laboratory findings (e.g., hematologic, hepatic, or coagulation abnormalities)

Other

• Rapidly progressive glomerulonephritis or rapidly declining renal function
• Immunodeficiency or low immunoglobulin G (IgG) levels below normal
• Current dialysis or anticipated need for dialysis during the study

• Diagnosis of primary IgA nephropathy (IgAN)
• Proteinuria above a protocol-defined threshold at screening
• Receiving stable standard-of-care therapy for IgAN for an adequate duration prior to enrollment, unless contraindicated or not tolerated
• Women of childbearing potential must have a negative pregnancy test prior to study drug administration and agree to use effective contraception; male participants must agree to use effective contraception
• Able to understand the study procedures and provide written informed consent