The purpose of this study is to evaluate the PK and safety of ublituximab SC at different sites of administration and relative bioavailability of ublituximab SC administered with an AI device versus syringe.

Inclusion Criteria:

1. Diagnosis of relapsing multiple sclerosis (RMS) (2017 Revised McDonald criteria).
2. Expanded Disability Status Scale (EDSS) score less than or equal to (≤) 5.5 at screening.
3. Neurologically stable for more than (>) 30 days prior to screening and Day 1.
4. Female participants of childbearing potential must consent to use an effective method of contraception from consent and for 6 months after the last dose of ublituximab.

Exclusion Criteria:

1. Primary-progressive multiple sclerosis (PPMS) or inactive secondary progressive multiple sclerosis (SPMS).
2. Active chronic disease of the immune system other than MS or immunodeficiency syndrome.
3. Participants with significantly impaired bone marrow function or significant leukopenia or thrombocytopenia.
4. Participants who received any approved therapy to treat MS within 5 half-lives of the medication prior to screening.
5. Treatment with any investigational agent within 5 half-lives of the investigational drug prior to screening.
6. Females who are pregnant or nursing.

Note: Other protocol-specified Inclusion/Exclusion criteria may apply.