Safety, Tolerability, and Pharmacokinetics of RSV Monoclonal Antibody RSM01 in Healthy Adults

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection (LRTI) among infants and young children, resulting in annual epidemics worldwide.

RSM01, a monoclonal antibody targeting RSV, may potentially provide an effective method to protect infants from RSV disease based on its potency and an extended half-life that is expected to support once-per-RSV-season administration.

This study was a first-in-human evaluation of RSM01 in healthy male and female adults with the goal of characterizing the safety and tolerability of a range of single doses of RSM01 to enable determination of appropriate dose(s) to be administered to infants in a future study. Enrollment was planned at a single study center in the United States. 56 participants were enrolled; 48 participants received RSM01 and 8 participants received Placebo. Participants were followed for approximately 5 months (151 days) after dosing.

Inclusion criteria

• Participant must be 18 to 49 years of age (inclusive), at the time of signing the informed consent.
• Participant is healthy as determined by medical evaluation including medical history, physical examination and laboratory tests.
• Body mass index (BMI) 18 to 29.9 kg/m2 (inclusive)
• Both males and females are eligible to participate. Female participants must not be pregnant, breastfeeding, or attempting to become pregnant for 28 days prior to screening and throughout the duration of the study. Females must be willing to comply with protocol-specified contraception for the duration of their participation in the study and for 90 days following the completion of the study. Male participants with partners of childbearing potential must be willing to comply with protocol specific contraception for the duration of their participation in the study and for 90 days following the completion of the study. Males must also agree to refrain from sperm donation for at least 90 days after they complete the study.
• Participant must be capable of giving signed informed consent which includes compliance with the requirements and restrictions listed in the informed consent form (ICF) and in the protocol
• Participant agrees to stay in contact with the study site for the duration of the study, provide updated contact information as necessary, and has no current plans to relocate from the study area for the duration of the study.

Exclusion criteria

• Acute illness and/or body temperature ≥37.5°C or ≥99.5°F on Study Day 1. NOTE: This is a temporary exclusion for which the participant may be re-evaluated
• Evidence and/or history of clinically significant medical condition(s) as judged by the investigator, including malignancies, diabetes mellitus, and unstable or uncontrolled hypertension
• History of any autoimmune disease or immune deficiency or other impairment to the immune system, including but not limited to HIV, autoimmune conditions, or immunosuppressive therapy. Note: history of Hashimoto's thyroiditis is not an exclusion criterion
• History of anaphylaxis
• Any current medical, psychiatric, occupational, or substance abuse problems that, in the opinion of the investigator, will make it unlikely that the participant will comply with the protocol
• Receiving or plans to receive any medications or other therapies that may impact the immune system such as allergy injections, interferon, immunomodulators, cytotoxic drugs or other drugs known to be frequently associated with major organ toxicity within 90 days prior to Day 1
• Received any vaccination (including COVID-19 vaccine) within the 15 days before Day 1 or plans to receive a dose of any vaccine during the 15-day period following Day 1
• Receiving or plans to receive immunosuppressive agents including systemic steroids within 90 days prior to Day 1 (individuals using inhaled or topical corticosteroids, prednisone (or equivalent) dose of ≤ 20 mg/day for ≤ 14 days, and intra-articular corticosteroids are permitted)
• Received or donated blood or blood products within 90 days prior to Day 1 or plans to receive or donate during the study period
• Received or plans to receive antibody or biologic therapy within 180 days prior to Day 1 or any time during the study period, whether licensed or investigational (e.g., immunoglobulin products, monoclonal antibodies, or antibody fragments)
• Participation in an interventional clinical trial and/or receipt of any investigational drug within 30 days or 5 half-lives of the investigational drug before the first day of study drug dosing in this study, whichever is longer.
• Concurrent enrollment in another interventional study
• Previously participated and received study intervention in the current study
• Female participants: positive serum pregnancy test
• Safety laboratory values outside of normal range, for age and sex that are suggestive of a disease state (Grade 1 abnormalities will not lead to exclusion if the investigator considers them not clinically significant.)
• Urinalysis abnormality greater than Grade 1 (with the exception of hematuria in a menstruating female), or urinalysis abnormality judged clinically significant by the investigator
• Clinically significant ECG abnormalities
• Reactive HIV antibody testing
• Current hepatitis B and/or hepatitis C infection
• Positive urine drug screen at screening or Day -1 (with the exception of prescribed drugs)
• History of allergy or hypersensitivity to the study drug, excipients or related substances
• Female participants with any one of the following conditions: currently pregnant or lactating/nursing; has positive serum pregnancy test during the Screening Phase, planning a pregnancy within 1 year after first dose of study drug
• Acting as study personnel or immediate family members (brother, sister, child, parent) or the spouse/partner of study personnel