Inclusion Criteria:

• Adults and adolescents (aged ≥ 12 years.
• Children 6 to 11 years of age.
• Children 2 to 5 years of age.
• Infants and newborns from birth to < 2 years of age.
• Documented diagnosis of PH1 or PH2, confirmed by genotyping (historically available genotype information is acceptable for study eligibility).
• Estimated GFR at Screening < 30 mL/min normalized to 1.73 m^2 BSA.  For infants aged less than 12 months, serum creatinine above the 97th percentile of a healthy population (Boer et al., 2010).
• Median of 3 plasma oxalate values > 30 µmol/L during Screening.
• Less than 20% variation from the median Screening period Pox value.
• For participants receiving hemodialysis or peritoneal dialysis, total duration of hemodialysis or peritoneal dialysis must be less than or equal to 18 months and hemodialysis or peritoneal dialysis regimen must have been stable for at least 3 months prior to Screening.
• Body weight of:
  • Adults and adolescents aged ≥ 12 years: ≥ 31.0 kg;
  • Children 6 to 11 years of age: to be determined;
  • Children 2 to 5 years of age: to be determined;
  • Infants and newborns from birth to < 2 years of age: to be determined.
• Male participants: A male participant with a female partner of childbearing potential must agree to use contraception during the treatment period and for at least 12 weeks after the last dose of study intervention and refrain from donating sperm during this period.
• Female participants: A female participant is eligible to participate if she is not pregnant, not breastfeeding, and at least one of the following conditions applies:
  • Not a woman of childbearing potential (WOCBP);OR
  • A WOCBP who agrees to follow the contraceptive guidance for the 4 weeks prior to randomization, during the treatment period, and for at least 12 weeks after the last dose of study intervention and agrees to refrain from harvesting/freezing eggs during this period. Contraceptive use by men or women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies.
• Participant (and/or participant’s parent or legal guardian if participant is a minor [defined as patient < 18 years of age, or younger than the age of majority according to local regulations]) is capable of giving signed informed consent, which includes compliance with the requirements and restrictions listed in the informed consent form (ICF) and in this protocol.
  • Adolescents (12 to < 18 years of age, or older than 12 years but younger than the age of majority according to local regulations) must be able to provide written assent for participation;
  • For children younger than 12 years of age, assent will be based on local regulations.
• Affiliated with or is a beneficiary of a health insurance system (if applicable per national regulations).

Exclusion Criteria:

• Prior hepatic transplantation; or scheduled transplantation within 6 months of Day 1. Renal transplantation planned in the 6 months from Day 1. Prior renal transplantation is allowed.
• Known history of severe systemic oxalosis.
• Presence of any condition or comorbidities that would interfere with study compliance or data interpretation or potentially impact patient safety including, but not restricted to:
  • Severe intercurrent illness;
  • Known causes of active liver disease/injury (e.g., alcoholic liver disease, nonalcoholic fatty liver disease/steatohepatitis);
  • Non-PH related conditions contributing to renal insufficiency;
  • Physician concerns about intake of drugs of abuse or excessive alcohol intake, or history of excessive alcohol intake in the 2 years prior to enrollment (defined as ≥ 21 units of alcohol per week in men and ≥ 14 units of alcohol per week in women; where a “unit” of alcohol is equivalent to a 12-ounce beer, 4-ounce glass of wine, or 1-ounce shot of hard liquor).
• Use of an RNAi drug, other than DCR-PHXC, within the last 6 months.
• History of one or more of the following reactions to an oligonucleotide-based therapy:
  • Severe thrombocytopenia (platelet count ≤ 100,000/µL);
  • Hepatotoxicity, defined as alanine transaminase (ALT) or aspartate transaminase (AST) > 3 times the upper limit of normal (ULN) and total bilirubin > 2 × ULN or international normalized ratio (INR) >1.5;
  • Severe flu-like symptoms leading to discontinuation of therapy;
  • Localized skin reaction from the injection (graded severe) leading to discontinuation of therapy;
  • Coagulopathy/clinically significant prolongation of clotting time.
• Participation in any clinical study in which they received an investigational medicinal product (IMP) other than DCR-PHXC within 4 months or 5 times the half-life of the drug (whichever is longer) before Screening.
• Liver function test abnormalities: ALT and/or AST >1.5 × ULN for age and gender.
• Positive anti-double-stranded deoxyribonucleic acid (anti-dsDNA) antibody test at Screening.
• Known hypersensitivity to DCR-PHXC or any of its ingredients.
• Inability or unwillingness to comply with the specified study procedures, including lifestyle considerations.