Inclusion Criteria:  Documented diagnosis of PH1 or PH2 confirmed by genotyping (historically available genotype information is acceptable for study eligibility).  Average spot Uox to creatinine ratio at Screening above 2 times the 95th percentile for age (Matos et al, 1999):  > 0.44 mol/mol in participants < 6 months > 0.34 mol/mol in participants from 6 months to < 12 months > 0.26 mol/mol in participants 12 months to < 2 years > 0.20 mol/mol in participants from 2 to < 3 years and > 0.16 mol/mol in participants from 3 to 5 years Estimated GFR at Screening ≥ 30 mL/min normalized to 1.73 m2 BSA. See Section 8.2.6.1 for equations. For infants aged less than 12 months, serum creatinine below the 97th percentile of a healthy population (Boer et al., 2010). Participants must have been on a stable treatment regimen for PH for 3 months prior to Day 1 and parent(s)/legal guardian should be willing to ensure participant remains on the same stable treatment regimen during the study. Body weight >10 kg Male or Female Participant's parent or legal guardian is capable of giving signed informed consent, which includes compliance with the requirements and restrictions listed in the ICF and in this protocol. A legal guardian or primary caregiver must be available to help the study-site personnel ensure follow up; accompany the participant to the study site on each assessment day according to the SoA (e.g., able to comply with scheduled visits, treatment plan, laboratory tests and other study procedures); consistently and consecutively be available to provide information on the participant using the rating scales during the scheduled study visits; accurately and reliably dispense study intervention as directed. Affiliated with or is a beneficiary of a health insurance system (if applicable per national regulations)  Exclusion Criteria:  Prior renal or hepatic transplantation; or planned transplantation within the study period Currently receiving dialysis or anticipating requirement for dialysis during the study period Plasma oxalate (Pox) > 30 μmol/L at Screening Documented evidence of clinical manifestations of severe systemic oxalosis (including preexisting retinal, heart, or skin calcifications, or history of severe bone pain, pathological fractures, or bone deformations)  Presence of any condition or comorbidities that would interfere with study compliance or data interpretation or potentially impact participant's safety including, but not restricted to:  Severe intercurrent illness Known causes of active liver disease/injury or transaminase elevation (e.g., alcoholic liver disease, nonalcoholic fatty liver disease/steatohepatitis [NAFLD/NASH]) History of serious mental illness that includes, but is not limited to, schizophrenia, bipolar disorder, or severe depression requiring hospitalization or pharmacological intervention Clinically relevant history or presence of cardiovascular, respiratory, gastrointestinal, hematological, lymphatic, neurological, musculoskeletal, genitourinary, immunological diseases, including dermatological including rash, severe eczema or dermatitis, or connective tissue diseases or disorders Use of an RNAi drug within the last 6 months  History of 1 or more of the following reactions to an oligonucleotide-based therapy:  Severe thrombocytopenia (platelet count ≤ 100,000/μL) Hepatotoxicity, defined as ALT or AST > 3 times the upper ULN and total bilirubin > 2 × ULN or 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 IMP within 4 months or 5 times the half-life of the drug (whichever is longer) before Screening  a. For IMPs with the potential to reduce urine and/or plasma oxalate concentrations, these concentrations must have returned to historical baseline levels prior to Screening  Liver function test (LFT) abnormalities: ALT and/or AST > 1.5 × ULN for age and gender Known hypersensitivity to nedosiran, or any of its ingredients Inability or unwillingness to comply with the specified study procedures, including the lifestyle considerations