Nedosiran in Pediatric Patients From Birth to 11 Years of Age With PH and Relatively Intact Renal Function

Inclusion Criteria:

1. Birth to 11 years of age inclusive, at the time of signing the informed consent.

2. Documented diagnosis of PH1 or PH2 or PH3 confirmed by genotyping (historicallyavailable genotype information is acceptable for study eligibility).

3. Average spot Uox to creatinine ratio at Screening above 2 times the 95th percentilefor 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 > 0.14 mol/mol inparticipants from 5 to <7 years > 0.12 mol/mol in participants from 7 to 11years

4. 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 belowthe 97th percentile of a healthy population (Boer et al., 2010).

5. Participants must have been on a stable treatment regimen for PH for 3 months priorto Day 1 and parent(s)/legal guardian should be willing to ensure participantremains on the same stable treatment regimen during the study. Dose adjustments forinterval weight gain are acceptable.

6. Male or Female Male participants: A male participant with a female partner of childbearing potential must agree to usecontraception, as detailed in Section 10.5.2, during the treatment period and for atleast 12 weeks after the last dose of study intervention and refrain from donatingsperm during this period. Female participants: A female participant is eligible to participate if she is not pregnant (see Section 10.5.1), not breastfeeding, and at least 1 of the following conditions applies: Not a woman of childbearing potential (WOCBP) as defined in Section 10.5.1 OR AWOCBP who agrees to follow the contraceptive guidance in Section 10.5.2 during thetreatment period and for at least 12 weeks after the last dose of studyintervention. Contraceptive use by men or women should be consistent with local regulationsregarding the methods of contraception for those participating in clinical studies. Note: If the childbearing potential changes after start of the study (e.g., apremenarchal female participant experiences menarche) or the risk of pregnancychanges (e.g., a female participant who is not heterosexually active becomesactive), the participant must discuss this with the Investigator, who shoulddetermine if a female participant must begin a highly effective method ofcontraception or a male participant must use a condom. If reproductive status isquestionable, additional evaluation should be considered.

7. Participant's parent or legal guardian is capable of giving signed informed consent,which includes compliance with the requirements and restrictions listed in the ICFand in this protocol. a. For children younger than 12 years of age, assent will be based on localregulation. If assent is required, participant must be able to provide writtenassent for participation.

8. A legal guardian or primary caregiver must be available to help the study-sitepersonnel ensure follow up; accompany the participant to the study site on eachassessment day according to the SoA (e.g., able to comply with scheduled visits,treatment plan, laboratory tests and other study procedures); consistently andconsecutively be available to provide information on the participant using therating scales during the scheduled study visits; accurately and reliably dispensestudy intervention as directed.

9. Affiliated with or is a beneficiary of a health insurance system (if applicable pernational regulations)

Exclusion Criteria:

1. Prior renal or hepatic transplantation; or planned transplantation within the studyperiod

2. Currently receiving dialysis or anticipating requirement for dialysis during thestudy period

3. Plasma oxalate (Pox) > 30 μmol/L at Screening

4. Documented evidence of clinical manifestations of severe systemic oxalosis (including preexisting retinal, heart, or skin calcifications, or history of severebone pain, pathological fractures, or bone deformations)

5. Presence of any condition or comorbidities that would interfere with studycompliance or data interpretation or potentially impact participant's safetyincluding, but not restricted to:

6. Severe intercurrent illness

7. Known causes of active liver disease/injury or transaminase elevation (e.g.,alcoholic liver disease, nonalcoholic fatty liver disease/steatohepatitis [NAFLD/NASH])

8. History of serious mental illness that includes, but is not limited to,schizophrenia, bipolar disorder, or severe depression requiring hospitalizationor pharmacological intervention

9. 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

10. Use of an RNAi drug within the last 6 months

11. History of 1 or more of the following reactions to an oligonucleotide-based therapy:

12. Severe thrombocytopenia (platelet count ≤ 100,000/µL)

13. Hepatotoxicity, defined as ALT or AST > 3 times the upper ULN and totalbilirubin > 2 × ULN or INR > 1.5

14. Severe flu-like symptoms leading to discontinuation of therapy

15. Localized skin reaction from the injection (graded severe) leading todiscontinuation of therapy

16. Coagulopathy/clinically significant prolongation of clotting time

17. 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 toScreening

18. Liver function test (LFT) abnormalities: ALT and/or AST > 1.5 × ULN for age andgender

19. Known hypersensitivity to nedosiran, or any of its ingredients

20. Inability or unwillingness to comply with the specified study procedures, includingthe lifestyle considerations detailed in Section 5.3.