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

The aim of this study is to evaluate nedosiran in participants 11 years of age and younger who have Primary Hyperoxaluria with relatively intact renal function.

This is an open-label, repeat-dose, Phase 2 study of nedosiran in participants 11 years of age or younger who have PH1, PH2 or PH 3 and relatively intact renal function.

Following the up-to-35- day screening period, participants will return to the clinic for monthly dosing visits through Day 180.

The total duration of this study is approximately 15 months from first participant, first visit, until last participant, last visit.

Eligibility Criteria:
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 (historically available genotype information is acceptable for study eligibility).
3. 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 \> 0.14 mol/mol in participants from 5 to \<7 years \> 0.12 mol/mol in participants from 7 to 11 years
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 below the 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 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. Dose adjustments for interval weight gain are acceptable.
6. Male or Female

   Male participants:

   A male participant with a female partner of childbearing potential must agree to use contraception, as detailed in Section 10.5.2, 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 (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 A WOCBP who agrees to follow the contraceptive guidance in Section 10.5.2 during the treatment period and for at least 12 weeks after the last dose of study intervention.

   Contraceptive use by men or women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies.

   Note: If the childbearing potential changes after start of the study (e.g., a premenarchal female participant experiences menarche) or the risk of pregnancy changes (e.g., a female participant who is not heterosexually active becomes active), the participant must discuss this with the Investigator, who should determine if a female participant must begin a highly effective method of contraception or a male participant must use a condom. If reproductive status is questionable, 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 ICF and in this protocol.

   a. For children younger than 12 years of age, assent will be based on local regulation. If assent is required, participant must be able to provide written assent for participation.
8. 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.
9. Affiliated with or is a beneficiary of a health insurance system (if applicable per national regulations)

Exclusion Criteria:

1. Prior renal or hepatic transplantation; or planned transplantation within the study period
2. Currently receiving dialysis or anticipating requirement for dialysis during the study 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 severe bone pain, pathological fractures, or bone deformations)
5. 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:

   1. Severe intercurrent illness
   2. Known causes of active liver disease/injury or transaminase elevation (e.g., alcoholic liver disease, nonalcoholic fatty liver disease/steatohepatitis \[NAFLD/NASH\])
   3. History of serious mental illness that includes, but is not limited to, schizophrenia, bipolar disorder, or severe depression requiring hospitalization or pharmacological intervention
   4. 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
6. Use of an RNAi drug within the last 6 months
7. History of 1 or more of the following reactions to an oligonucleotide-based therapy:

   1. Severe thrombocytopenia (platelet count ≤ 100,000/µL)
   2. Hepatotoxicity, defined as ALT or AST \> 3 times the upper ULN and total bilirubin \> 2 × ULN or INR \> 1.5
   3. Severe flu-like symptoms leading to discontinuation of therapy
   4. Localized skin reaction from the injection (graded severe) leading to discontinuation of therapy
   5. Coagulopathy/clinically significant prolongation of clotting time
8. 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
9. Liver function test (LFT) abnormalities: ALT and/or AST \> 1.5 × ULN for age and gender
10. Known hypersensitivity to nedosiran, or any of its ingredients
11. Inability or unwillingness to comply with the specified study procedures, including the lifestyle considerations detailed in Section 5.3.