L9LS MAb in Malian Infants

The purpose of this study is to assess the safety, tolerability, and pharmacokinetics of L9LS in infants in Mali and to evaluate the impact of L9LS on subsequent R21/Matrix-MTM vaccine immunogenicity.

This is an age-stratified, randomized, double-blind, placebo-controlled trial evaluating the safety, tolerability, and pharmacokinetics (PK) of 1-time intramuscular (IM) administration of the monoclonal antibody (MAb) L9LS to healthy Malian infants aged 1 to 12 months, followed by an assessment of the impact of L9LS on the immunogenicity of subsequent administration of the R21/Matrix-MTM vaccine. The study hypotheses are that L9LS will be safe and will not impact the immunogenicity of the R21/Matrix-MTM vaccine. During the beginning of the 6-month malaria season (approximately August and September at the study site), 180 participants will be enrolled and randomized 1:1 to receive 150 mg of L9LS (n=90) or normal saline placebo (n=90). Randomization of participants in each arm will be age-stratified (1 to 4 months, n=60; \>4 to 8 months, n=60; \>8 to 12 months, n=60). The safety of L9LS will be assessed within each of the 3 age strata. Participants will be followed at study visits 1, 3, 7, 14, 21, and 28 days later, and once every 4 weeks thereafter through study day 280 (40 weeks). Approximately 5 months after receiving L9LS or placebo, all participants will receive the R21/Matrix-MTM vaccine as 3 total doses given 4 weeks apart as per World Health Organization (WHO) recommendations and the anticipated Malian vaccination guidelines. Primary study assessments include medical history, physical examination, and blood collection to assess antibody responses to the R21/Matrix-MTM vaccine, L9LS PK, anti-drug antibody (ADA) assessments, identification of Plasmodium falciparum (Pf) infection by microscopic examination of thick blood smears and reverse transcription polymerase chain reaction (RT-PCR), and other research laboratory evaluations. Through their local provider, all participants 3 months and older will be offered 4 rounds of seasonal malaria chemoprevention (SMC) as a monthly 3-day treatment course of sulfadoxine-pyrimethamine plus amodiaquine (SPAQ), as it is the standard of care in Mali for malaria prevention in children 3 months to 5 years of age.