A Phase 1/2, Multicenter Trial to Investigate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of BION-1301 in Healthy Volunteers and Adults With IgA Nephropathy

• Healthy male or female volunteers, 18 to 55 years old

• Females must be of non-childbearing potential

• Males must agree to follow the protocol-specified contraception guidance

• Body mass index (BMI) between 18 and 35 kg/m\^2, with a weight of at least 50 kg

• Non-smoker, defined as an individual who has not smoked previously and/or who has discontinued smoking or the use of nicotine/nicotine-containing products at least 3 months before Screening

• Able to provide signed informed consent

• Male or female ≥18 years old at Screening

• Women of child-bearing potential (WOCBP; per CTFG 2014) must agree to follow the protocol-specified contraception guidance throughout the study (from Screening through approximately 6 months after the final dose of study drug)

• Males must agree to follow the protocol-specified contraception guidance throughout the study (from Screening through approximately 6 months after the final dose of study drug)

• BMI between 18 and 40 kg/m\^2, inclusive, at Screening with a weight of at least 50 kg

• Diagnosis of IgAN verified by biopsy taken within the past 10 years

• Urine protein ≥ 0.5 g/24h; OR UPCR ≥ 0.5 g/g (or ≥ 50 mg/mmol)

• eGFR (per Chronic Kidney Disease Epidemiology Collaboration \[CKD-EPI\] formula) or measured GFR ≥ 30 mL/min per 1.73 m\^2

• Stable on an optimized dose of angiotensin converting enzyme (ACE) inhibitors and/or angiotensin-receptor blockers (ARBs) for at least 3 months prior to Screening or intolerant to ACE/ARB