The primary objective of the study is to evaluate the safety and tolerability of ascending doses of subcutaneous (SC) pozelimab and SC cemdisiran when administered on the same day or sequentially 28 days apart.

The secondary objectives of the study are:

• To assess the concentration-time profiles of total pozelimab, total complement component 5 (C5), cemdisiran, and cemdisiran metabolite(s) following single ascending doses of SC pozelimab and SC cemdisiran when administered on the same day or sequentially 28 days apart
• To assess the pharmacodynamic (PD) profile of ascending doses of SC pozelimab and SC cemdisiran, as well as when administered on the same day or sequentially 28 days apart
• To assess the immunogenicity of pozelimab and cemdisiran

Key Inclusion Criteria:

1. Has a body mass index less than 30 kg/m2 at the screening visit
2. Judged to be in good health as defined in the protocol
3. Is in good health based on laboratory safety testing obtained at the screening visit NOTE: Subject with a history of Gilbert's disease can be enrolled in the study
4. Willing to undergo vaccination against Neisseria meningitidis unless subjects have documentation of completed series of vaccinations within the past 2 years of the screening visit
5. Must have two negative COVID-19 tests taken 48 hours apart and within 7 days prior to study drug administration

Key Exclusion Criteria:

1. History of clinically significant cardiovascular, respiratory, hepatic, renal, gastrointestinal, endocrine, hematological, psychiatric or neurological disease, as assessed by the investigator that may confound the results of the study or poses an additional risk to the subject by study participation
2. Hospitalization (>24 h) for any reason within 30 days of the screening visit
3. Has a confirmed positive drug test result at the screening visit and/or prior to enrollment; or a history of recreational drug use (eg, marijuana) and/or drug or alcohol abuse within a year prior to the screening visit
4. Is positive for HIV, hepatitis B surface antigen (HBsAg), or hepatitis B core antibody (HBcAb), hepatitis C antibody and positive for qualitative (ie, detected) HCV RNA test at the screening visit
5. Within the previous 2 months of the screening visit has a history of bacterial, protozoal, parasitic or viral infection (including COVID-19) and/or persistent chronic or active recurring infection which requires treatment with antibiotics, antivirals, or antifungals
6. Known or suspected COVID-19 disease
7. Known allergy or intolerance to penicillin class antibiotics or macrolides

NOTE: Other protocol-defined Inclusion/ Exclusion criteria apply

All Individual Patient Data (IPD) that underlie publicly available results will be considered for sharing

When Regeneron has received marketing authorization from major health authorities (e.g., FDA, European Medicines Agency (EMA), Pharmaceuticals and Medical Devices Agency (PMDA), etc.) for the product and indication, has made the study results publicly available (e.g., scientific publication, scientific conference, clinical trial registry), has the legal authority to share the data, and has ensured the ability to protect participant privacy.

Qualified researchers can submit a proposal for access to individual patient or aggregate level data from a Regeneron-sponsored clinical trial through Vivli. Regeneron's Independent Research Request Evaluation Criteria can be found at: https://www.regeneron.com/sites/default/files/Regeneron-External-Data-Sharing-Policy-and-Independent-Research-Request-Evaluation-Criteria.pdf