This study will investigate the safety, tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) of RLYB116 (with an improved impurity profile) following repeated administration of RLYB116 in healthy participants.

Inclusion Criteria:

1. Male and female participants, 18 to 55 years of age.

2. Able to provide written informed consent.

3. Body mass index (BMI) of 18.0 to 32.0 kg/m2.

4. Must have been vaccinated against N. meningitidis and S. pneumoniae with approved vaccine according to product label. All participants considered eligible for enrollment will be vaccinated or willing to receive vaccination according to the following:

   1. Vaccination with Meningococcal Group A, C, W135, and Y conjugate vaccine (Menveo® or an acceptable alternative) + Pneumococcal Polysaccharide Vaccine (Pneumovax® 23 or an acceptable alternative) at least 28 days prior to receiving the first dose of RLYB116.
   2. Vaccination with Meningococcal Group B (Bexsero®) at least 14 days prior to receiving the first dose of RLYB116.

Exclusion Criteria:

1. Participants that smoke more than 10 cigarettes per week
2. Positive serology for HIV or active infection with hepatitis B virus or hepatitis C virus.
3. Pregnant or nursing
4. Donation or loss of greater than 400 mL of blood within 56 days of study enrollment
5. History of severe hypersensitivity to any drug, including penicillin or ciprofloxacin, or to N. meningitidis or S. pneumoniae vaccines.