Efficacy, Safety, Pharmacokinetics, and Pharmacodynamics of KP104 to Treat Glomerulonephritis

Inclusion criteria

• Weight of >35 kilograms (kg) at Screening
• Body mass index (BMI) of <35 kilograms per square meter (kg/m^2)
• UPCR >1.0 grams per gram (g/g) by 24-hour urine collection at Screening
• Documented diagnosis and clinical status of IgAN or C3G as follows:

IgAN:

• Diagnosis of IgAN verified by biopsy taken within the past 3 years prior to enrolment.
• On stable regimen of angiotensin converting enzyme or angiotensin blocking agents for 12 weeks and/or sodium-glucose cotransporter-2 (SGLT2) inhibitors for 6 weeks at Screening

C3G:

• Diagnosis of C3G verified by biopsy taken within the past 3 years prior to enrolment.
• On stable regimen of angiotensin converting enzyme or angiotensin blocking agents for 12 weeks and/or SGLT2 inhibitors for 6 weeks at Screening

• Females of childbearing potential and males must practice effective contraception from Screening until 28 days after the end of study (EOS) visit.
• Females of childbearing potential must have a negative pregnancy test at Screening and within 1 day prior to dosing of study drug

Exclusion criteria

• Any clinically significant, poorly controlled underlying illness other than IgAN or C3G, as determined by the investigator
• Treatment of any infection with IV (within 30 days of Screening) or oral (within 14 days of Screening) antibiotics, antivirals, or antifungals
• History of infections with encapsulated organisms
• History of untreated tuberculosis
• Positive serology for hepatitis C virus (HCV) ribonucleic acid (RNA) or human immunodeficiency virus (HIV) at Screening
• History of bone marrow or stem cell transplantation
• Absolute neutrophil count (ANC) <500 cells per microliter (cells/μL)
• eGFR <30 milliliters per minute per 1.73 square meter (mL/min/1.73 m^2) using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula
• Presence of crescent formation in >50 percent (%) of glomeruli assessed on renal biopsy
• Nephrotic syndrome defined as presence of substantial proteinuria (> 3.5 g/24 hours), hypoalbuminemia (< 30 grams per liter [g/L]), and edema/hyperlipidemia. Nephrotic range proteinuria alone is acceptable.
• Rapidly progressive glomerulonephritis, defined as a fall in eGFR of > 30 mL/min/1.73 m^2 within 24 weeks prior to the Screening Visit
• Receiving renal replacement therapy or anticipated to require renal replacement therapy during the duration of the study

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.