Key Inclusion Criteria for Parts A and B

• Documentation of PH1 as determined by genetic analysis confirming pathogenic mutations in the alanine-glyoxylate aminotransferase (AGXT) gene (valid historical laboratory data will be reviewed and approved by the Sponsor)

• Age at time of signing the informed consent/assent form:

  • Part A: ≥18 years to ≤64 years
  • Part B: ≥6 years to <18 years

• 24-hour UOx ≥0.7 mmol/24 hours/1.73 m²

• eGFR ≥30 mL/min/1.73m²

• Weight ≤90 kg

Key Exclusion Criteria for Parts A and B

• Confirmed diagnosis of primary hyperoxaluria type 2 or type 3
• History of a liver, kidney or combined liver/kidney transplant
• Currently on dialysis
• Participant has previously used (within past 24 months) or is currently receiving an approved or investigational urinary oxalate lowering RNA interference (RNAi) or siRNA therapy
• Female participants who are pregnant or breastfeeding (or are planning either during the first 12 months)