NCT07208760

L9LS-R21 Interaction

A Phase 2, Randomized, Double-Blind, Placebo-Controlled Trial to Evaluate the Effect of L9LS on R21/Matrix-M™ Vaccine Immunogenicity

• Status: Withdrawn
• Phase: Phase 2
• Study type: Interventional
• Enrollment: 0 (actual)
• Sponsor: National Institute of Allergy and Infectious Diseases (NIAID) · NIH
• Sex: All
• Age: 5 Months – 50 Years
• Healthy volunteers: Accepted

Summary

This is a randomized, double-blind, placebo-controlled trial in 2 parts evaluating the effect of 1-time administration of the monoclonal antibody (MAb) L9LS to healthy Malian participants on the immunogenicity of subsequent administration of the R21/Matrix-M™ vaccine. L9LS will be administered subcutaneously (SC) for adults and infants. The study will assess how the timing of L9LS administration impacts immunogenicity following subsequent intramuscular (IM) R21/Matrix-M™ vaccination. Twenty-four adult participants and 333 infant participants will be enrolled.

Detailed description

In Part 1, 24 adult participants will be randomized 1:1 to receive 1800 mg of L9LS or normal saline placebo at enrollment, followed by the R21/Matrix-M™ 3-dose initial vaccine series starting on day 7. Adult participants will be followed at study visits 7 days after L9LS administration and 7 days after each R21/Matrix-M™ vaccination. If no significant safety concerns arise through 7 days after administration of the first R21/Matrix-M™ vaccine (day 14) per an interim safety review, the study will proceed to Part 2. There will also be study visits 28 and 84 days following the last R21/Matrix-M™ vaccine to assess immune responses. In Part 2, 333 infant participants will be randomized into 1 of 3 cohorts, each with an L9LS arm and a placebo arm (2:1). The individual cohorts will differ in the timing of the R21/Matrix-M™ 3-dose initial vaccine series (7 days, 2 months, and 4 months between L9LS and first R21/Matrix-M™ respectively). Infant participants will be followed at study visits 7 days after L9LS administration and 7 days after each R21/Matrix-M™ vaccination, after which they will continue to be followed every 28 days through the fourth (booster) dose of the R21/Matrix-M™ vaccine. There will also be study visits 28 and 84 days following the last R21/Matrix-M™ vaccine to assess immune responses. Primary study assessments include medical history, physical examination, and blood collection to assess antibody responses to the R21/Matrix-M™ vaccine, L9LS pharmacokinetics (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.

Conditions

• Malaria

Interventions

Type	Name	Description
DRUG	Single dose of 1800 mg L9LS SC (12mL)	A human monoclonal antibody to protect against Plasmodium falciparum.
OTHER	Placebo 12 mL SC	Normal saline.
DRUG	Single dose of 225 mg L9LS SC (1.5mL)	A human monoclonal antibody to protect against Plasmodium falciparum.
OTHER	Placebo 1.5 mL SC	Normal saline.

Timeline

• Start date: 2026-03-01
• Primary completion: 2028-03-01
• Completion: 2029-03-01
• First posted: 2025-10-06
• Last updated: 2026-04-09

Locations

1 site across 1 country: Mali

Regulatory

• FDA-regulated drug study