Anti-malaria MAb in Malian Children (L9LS)

Safety and Efficacy of L9LS, a Human Monoclonal Antibody Against Plasmodium Falciparum, in a Dose-Escalation Trial in Adults and Children and a Randomized, Double-Blind Trial of Children in Mali

The purpose of this study is to evaluate the safety and tolerability of onetime subcutaneous (SC) or intravenous (IV) administration of monoclonal antibody (MAb) L9LS in healthy Malian adults and one-time SC administration of L9LS in healthy Malian children, as well as its protective efficacy against naturally occurring Plasmodium falciparum (Pf) infection over a 7-month malaria season in healthy Malian children 6-10 years of age.

Study Overview

• Status: Completed
• Conditions: Malaria; Plasmodium Falciparum Infection
• Intervention / Treatment: Biological: L9LS (VRC-MALMAB0114-00-AB) Subcutaneous injection; Biological: L9LS (VRC-MALMAB0114-00-AB) intravenous injection; Other: Placebo

Detailed Description

A two-part, phase 2 trial evaluating the safety and tolerability of onetime subcutaneous (SC) or intravenous (IV) administration of monoclonal antibody (MAb) L9LS in healthy Malian adults and one-time SC administration of L9LS in healthy Malian children, as well as its protective efficacy against naturally occurring Plasmodium falciparum (Pf) infection over a 7-month malaria season in healthy Malian children 6-10 years of age.

The first part of the study is an age de-escalation and dose-escalation study for safety and tolerability. Adult subjects in the dose-escalation study will be assigned in open-label fashion to 1 of 3 L9LS dose arms. Dosing will begin in the lowest dose arm. Once all subjects in that arm reach day 7 post-administration, if no safety concerns have arisen, dosing will begin at the next dose level. Once all subjects in that arm reach day 7 post-administration, if no safety concerns have arisen, dosing will begin at the highest dose level. Once all adult subjects reach day 7 post-administration, if no safety concerns have arisen, 18 subjects aged 6-10 years will be randomized 1:1 to L9LS or placebo in double-blind fashion. Once all 18 subjects reach day 7 post-administration, if no safety concerns have arisen, an additional 18 subjects aged 6-10 years will be randomized 1:1 to L9LS versus placebo. Randomization of subjects aged 6-10 years in each L9LS dose arm will be weight-stratified and enrollment will be weight de-escalated. Adult subjects will be followed for safety to assess adverse events (AEs) at study visits 1, 3, 7, 14, 21, and 28 days after administration, and once every month thereafter through 28 weeks. Subjects aged 6-10 years will be followed at study visits 1, 3, 7, 14, 21, and 28 days after administration, and once every 2 weeks thereafter through 36 weeks. Primary study assessments include physical examination and blood collection for identification of Pf infection and other research laboratory evaluations. After the last subject in the pediatric L9LS dose arm reaches day 7 safety follow-up, an interim safety evaluation will be performed before enrollment begins for the efficacy part of the study. Data from the 36 subjects aged 6-10 years enrolled in the dose-escalation study will be included in a secondary analysis to determine the relationship between L9LS concentration and the risk of Pf infection.

The second part of the study is a weight-stratified, randomized, double-blind, placebo-controlled trial to assess safety and protective efficacy of L9LS versus placebo administered SC in children 6-10 years of age. In this part of the study, subjects will be randomized to L9LS or placebo. Randomization of subjects in each arm will be weight-stratified. Subjects in the efficacy study will receive the study agent prior to the malaria season and be followed at study visits 1, 3, 7, 14, 21, and 28 days later, and once every 2 weeks thereafter through 24 weeks. Primary study assessments include physical examination and blood collection for identification of Pf infection and other research laboratory evaluations.

Prior to the last study visit of the original protocol described above (January 2023 - February 2023), study participants who remain enrolled in the dose-escalation and efficacy studies will be invited to participate in a 12-month extension study. After the safety and efficacy results are unblinded (approximately March/April 2023), participants who agree to continue with the extension will be grouped into one of 3 arms based on their original study arm assignment:

Arm 1: Up to 84 subjects who received 150 mg of L9LS in year 1 (9 from the dose-escalation study, plus 75 from the efficacy study).

Arm 2: Up to 84 subjects who received 300 mg of L9LS in year 1 (9 from the dose-escalation study, plus 75 from the efficacy study).

Arm 3: Up to 93 subjects who received placebo in year 1 (18 from the dose-escalation study, plus 75 from the efficacy study).

The protocol extension employs a pre-specified, adaptive design based on the time-to-event efficacy of 150 mg and 300 mg of L9LS against P. falciparum infection as detected by blood smear observed after the first malaria season in the original protocol. Specifically, if 150 mg and 300 mg of L9LS both show ≥60% efficacy during the first malaria season (based on the upper bound of the two-sided 95% confidence interval [CI]), participants will be re-randomized 1:1 in a double-blind fashion within each arm to receive a single dose of either L9LS (150 or 300 mg depending on study arm) or placebo administered SC before the 2023 malaria season.

The same randomization scheme will be followed if in the first malaria season the 300-mg dose of L9LS shows ≥60% efficacy (based on the upper bound of the two-sided 95% CI) and the 150-mg dose of L9LS shows <60% efficacy (based on the upper bound of the two-sided 95% CI) but the difference between their respective point estimates of efficacy is ≤10%, with the exception that children who received placebo in year 1 will receive 300 mg of L9LS (or placebo) in year 2.

If 300 mg of L9LS shows ≥60% efficacy (based on the upper bound of the two-sided 95% CI) and 150 mg of L9LS shows <60% efficacy (based on the upper bound of the two-sided 95% CI) but the difference between their respective point estimates of efficacy is >10% during the first malaria season, participants will be re-randomized 1:1 in a double-blind fashion within each arm to receive a single dose of either 300 mg of L9LS or placebo administered SC before the 2023 malaria season.

If 150 mg and 300 mg of L9LS both show <60% efficacy (based on the upper bound of the two-sided 95% CI) after the first malaria season, the protocol extension will be abandoned.

Before study agent administration, all subjects will be given artemether-lumefantrine to clear any preexisting Pf blood-stage infection.

Subjects will be followed at study visits 1, 3, 7, 14, 21, and 28 days after administration, and once every 2 weeks thereafter through 28 weeks, with a final visit occurring on study day 252 (36 weeks) to collect a final PK sample. Primary study assessments include medical history, physical examination, and blood collection for pharmacokinetics (PK), anti-drug antibody (ADA) assessments, identification of Pf infection by microscopic examination of thick blood smears and RT-PCR, and other research laboratory evaluations.

• Study Type: Interventional
• Enrollment (Actual): 365
• Phase: Phase 2

Contacts and Locations

Study Locations

• Mali
  • Région De Koulikoro
    • Kalifabougou, Région De Koulikoro, Mali
      • Kalifabougou MRTC Clinic
    • Torodo, Région De Koulikoro, Mali
      • Torodo MRTC Clinic

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 6 years to 55 years (Child, Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Is within the appropriate age range for the respective cohort:

  1. Children: Aged ≥6 years and <11 years.
  2. Adults: Aged ≥18 years.
• Able to provide proof of identity to the satisfaction of the study clinician completing the enrollment process.
• In good general health and without clinically significant medical history.
• Adult participants or parent and/or guardian of minor participants able to provide informed consent.
• Willing to have blood samples and data stored for future research.
• Resides in or near Kalifabougou or Torodo, Mali, and available for the duration of the study.

• For the adult cohort, females of childbearing potential must be willing to use reliable contraception from 21 days prior to study day 0 through the final study visit as described below.

  • Reliable methods of birth control include 1 of the following: confirmed pharmacologic contraceptives via parenteral delivery or intrauterine or implantable device.
  • Nonchildbearing women will be required to report date of last menstrual period, history of surgical sterility (i.e., tubal ligation, hysterectomy) or premature ovarian insufficiency, and will have urine or serum pregnancy test performed per protocol.

Year 2 Extension Inclusion Criteria:

• Participated in the first year of the protocol.
• Able to provide proof of identity to the satisfaction of the study clinician completing the enrollment process.
• In good general health and without clinically significant medical history.
• Parent and/or guardian able to provide informed consent.
• Willing to have blood samples and data stored for future research.
• Resides in or near Kalifabougou or Torodo, Mali, and available for the duration of the study.

Exclusion Criteria:

• Body weight <15 kg or >30 kg for children, or >60 kg for adults.
• Currently receiving or planning to receive seasonal malaria chemoprevention (SMC).
• Any history of menses (for 6-10 year old cohort) or positive pregnancy test at screening (for adult cohort).
• Behavioral, cognitive, or psychiatric disease that in the opinion of the investigator affects the ability of the subject to understand and comply with the study protocol.
• Subject (for adult subjects) or parental (for minor subjects) study comprehension examination score of <80% correct or per investigator discretion.
• Hemoglobin, white blood cell, absolute neutrophil, or platelet count outside the local laboratory-defined limits of normal. (Subjects may be included at the investigator's discretion for "not clinically significant" values.)
• Alanine transaminase (ALT) or creatinine (Cr) level above the local laboratory-defined upper limit of normal. (Subjects may be included at the investigator's discretion for "not clinically significant" values.)
• Infected with HIV, hepatitis C virus (HCV), or hepatitis B virus (HBV).
• Known or documented sickle cell disease by history. (Note: Known sickle cell trait is NOT exclusionary.)
• Clinically significant abnormal electrocardiogram (ECG; Corrected QT Interval (QTc) >460 or other significant abnormal findings, including unexplained tachycardia or bradycardia).
• Evidence of clinically significant neurologic, cardiac, pulmonary, hepatic, endocrine, rheumatologic, autoimmune, hematological, oncologic, or renal disease by history, physical examination, and/or laboratory studies including urinalysis.
• Receipt of any investigational product within the past 30 days.
• Participation or planned participation in an interventional trial with an investigational product before the last required protocol visit. (Note: Past, current, or planned participation in observational studies is NOT exclusionary.)
• Medical, occupational, or family problems as a result of alcohol or illicit drug use during the past 12 months.
• History of a severe allergic reaction or anaphylaxis.
• Severe asthma (defined as asthma that is unstable or required emergent care, urgent care, hospitalization, or intubation during the past 2 years, or that has required the use of oral or parenteral corticosteroids at any time during the past 2 years).
• Salivary gland disorder diagnosed by a doctor (e.g., parotitis, sialadenitis, sialolithiasis, salivary gland tumors).
• Pre-existing autoimmune or antibody-mediated diseases including but not limited to: systemic lupus erythematosus, rheumatoid arthritis, multiple sclerosis, Sjogren's syndrome, or autoimmune thrombocytopenia.
• Known immunodeficiency syndrome.
• Known asplenia or functional asplenia.
• Use of chronic (≥14 days) oral or IV corticosteroids (excluding topical or nasal) at immunosuppressive doses (i.e., prednisone >10 mg/day) or immunosuppressive drugs within 30 days of day 0.
• Receipt of a live vaccine within the past 4 weeks or a killed vaccine or COVID-19 vaccine within the past 2 weeks prior to study agent administration.
• Receipt of immunoglobulins and/or blood products within the past 6 months.
• Previous receipt of an investigational malaria vaccine or monoclonal antibody in the last 5 years.
• Known allergies or contraindication against artemether-lumefantrine.
• Clinical signs of malnutrition.
• Other condition(s) that, in the opinion of the investigator, would jeopardize the safety or rights of a subject participating in the trial, interfere with the evaluation of the study objectives, or render the subject unable to comply with the protocol.

Year 2 Extension Exclusion Criteria:

• Currently receiving or planning to receive SMC.
• Any history of menses.
• Behavioral, cognitive, or psychiatric disease that in the opinion of the investigator affects the ability of the subject to understand and comply with the study protocol.
• Parental study comprehension examination score of <80% correct or per investigator discretion.
• Hemoglobin, white blood cell, absolute neutrophil, or platelet count outside the local laboratory-defined limits of normal. (Subjects may be included at the investigator's discretion for "not clinically significant" values.)
• Alanine transaminase (ALT) or creatinine (Cr) level above the local laboratory-defined upper limit of normal. (Subjects may be included at the investigator's discretion for "not clinically significant" values.)
• Infected with HIV, hepatitis C virus (HCV), or hepatitis B virus (HBV).
• Known or documented sickle cell disease by history. (Note: Known sickle cell trait is NOT exclusionary.)
• Clinically significant abnormal electrocardiogram (ECG; QTc >460 or other significant abnormal findings, including unexplained tachycardia or bradycardia).
• Evidence of clinically significant neurologic, cardiac, pulmonary, hepatic, endocrine, rheumatologic, autoimmune, hematological, oncologic, or renal disease by history, physical examination, and/or laboratory studies including urinalysis.
• Receipt of any investigational product within the past 30 days.
• Participation or planned participation in another interventional trial with an investigational product other than L9LS until the last required protocol visit. (Note: Past, current, or planned participation in observational studies is NOT exclusionary.)
• Medical, occupational, or family problems as a result of alcohol or illicit drug use during the past 12 months.
• History of a severe allergic reaction or anaphylaxis.
• Severe asthma (defined as asthma that is unstable or required emergent care, urgent care, hospitalization, or intubation during the past 2 years, or that has required the use of oral or parenteral corticosteroids at any time during the past 2 years).
• Currently active salivary gland disorder diagnosed by a doctor (e.g., parotitis, sialadenitis, sialolithiasis, salivary gland tumors).
• Pre-existing autoimmune or antibody-mediated diseases including but not limited to: systemic lupus erythematosus, rheumatoid arthritis, multiple sclerosis, Sjogren's syndrome, or autoimmune thrombocytopenia.
• Known immunodeficiency syndrome.
• Known asplenia or functional asplenia.
• Use of chronic (≥14 days) oral or IV corticosteroids (excluding topical or nasal) at immunosuppressive doses (i.e., prednisone >10 mg/day) or immunosuppressive drugs within 30 days of day 0.
• Receipt of a live vaccine within the past 4 weeks or a killed vaccine or COVID-19 vaccine within the past 2 weeks prior to study agent administration.
• Receipt of immunoglobulins and/or blood products within the past 6 months.
• Previous receipt of an investigational malaria vaccine or any other monoclonal antibody other than L9LS in the last 5 years.
• Known allergies or contraindication against artemether-lumefantrine.
• Clinical signs of malnutrition.
• Other condition(s) that, in the opinion of the investigator, would jeopardize the safety or rights of a subject participating in the trial, interfere with the evaluation of the study objectives, or render the subject unable to comply with the protocol.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Sequential Assignment
• Masking: Triple

Number of Arms

12

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Adult Dose-escalation study: Arm 1: 300 mg of L9LS; Adult participants receive single dose of 300 mg of L9LS subcutaneously. Once subjects reach day 7 post-administration without safety concerns dosing begins for arm 2.	Biological: L9LS (VRC-MALMAB0114-00-AB) Subcutaneous injection; Administered one time via subcutaneous route.
Experimental: Adult Dose-escalation study: Arm 2: 600 mg of L9LS; Adult participants receive single dose of 600 mg of L9LS subcutaneously. Once subjects reach day 7 post-administration without safety concerns dosing begins for arm 3.	Biological: L9LS (VRC-MALMAB0114-00-AB) Subcutaneous injection; Administered one time via subcutaneous route.
Experimental: Adult Dose-escalation study: Arm 3: 20 mg/kg of L9LS; Adult participants receive highest single dose of 20 mg/kg IV of L9LS intravenously. Once subjects reach day 7 post-administration without safety concerns dosing begins for pediatric subjects dose escalation arm 1.	Biological: L9LS (VRC-MALMAB0114-00-AB) intravenous injection; Administered one time via intravenous route.
Experimental: Pediatric Dose-escalation study: Arm 1: 150 mg of L9LS; Pediatric subjects ages 6-10 years receive single dose of 150 mg L9LS subcutaneously. Once subjects reach day 7 post-administration without safety concerns, dosing begins for arm 2.	Biological: L9LS (VRC-MALMAB0114-00-AB) Subcutaneous injection; Administered one time via subcutaneous route.
Experimental: Pediatric Dose-escalation study: Arm 2: 300 mg of L9LS; Pediatric subjects ages 6-10 years receive single dose of 300 mg L9LS subcutaneously. Once subjects reach day 7 post-administration without safety concerns, dosing begins for the pediatric efficacy study arms.	Biological: L9LS (VRC-MALMAB0114-00-AB) Subcutaneous injection; Administered one time via subcutaneous route.
Placebo Comparator: Pediatric Dose-escalation study: Arm 3: Placebo; Pediatric subjects ages 6-10 receive single dose placebo of normal saline subcutaneously for comparison.	Other: Placebo; Normal saline administered one time via subcutaneous route.
Experimental: Pediatric Efficacy study: Arm 1: 150 mg of L9LS; Pediatric subjects ages 6-10 receive single dose of 150 mg L9LS subcutaneously.	Biological: L9LS (VRC-MALMAB0114-00-AB) Subcutaneous injection; Administered one time via subcutaneous route.
Experimental: Pediatric Efficacy study: Arm 2: 300 mg of L9LS; Pediatric subjects ages 6-10 receive single dose of 300 mg L9LS subcutaneously.	Biological: L9LS (VRC-MALMAB0114-00-AB) Subcutaneous injection; Administered one time via subcutaneous route.
Placebo Comparator: Pediatric Efficacy study: Arm 3: Placebo; Pediatric subjects ages 6-10 receive single dose placebo of normal saline subcutaneously.	Other: Placebo; Normal saline administered one time via subcutaneous route.
Experimental: Pediatric Extension study: Arm 1: 150 mg of L9LS; Pediatric subjects ages 6-10 who completed year one of the study and agreed to continue with the extension were randomized to receive 150 mg of L9LS subcutaneously.	Biological: L9LS (VRC-MALMAB0114-00-AB) Subcutaneous injection; Administered one time via subcutaneous route.
Experimental: Pediatric Extension study: Arm 2: 300 mg of L9LS; Pediatric subjects ages 6-10 who completed year one of the study and agreed to continue with the extension were randomized to receive 300 mg of L9LS subcutaneously.	Biological: L9LS (VRC-MALMAB0114-00-AB) Subcutaneous injection; Administered one time via subcutaneous route.
Placebo Comparator: Pediatric Extension study: Arm 3: Placebo; Pediatric subjects ages 6-10 who completed year one of the study and agreed to continue with the extension were randomized to receive placebo of normal saline subcutaneously.	Other: Placebo; Normal saline administered one time via subcutaneous route.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Participants With Local Adverse Events (AEs) - Year One	Number of participants with local adverse events occurring within 7 days after administration of L9LS. Local reactogenicity included pain/tenderness, swelling, redness, bruising, and pruritus at the site of infusion. Adverse events were captured by Investigator examination and history from participants.	Within 7 days after administration of L9LS
Severity of Local Adverse Events (AEs) - Year One	The severity of local AEs was graded using the Toxicity Grading Scale for Healthy Adult and Adolescent Volunteers Enrolled in Preventive Clinical Trials. Grade 1: Pain = does not interfere with activity; Tenderness = mild discomfort to touch; Erythema/Redness = 2.5-5 cm; Induration/Swelling = 2.5-5 cm and does not interfere with activity. Grade 2: Pain = Repeated use of non-narcotic pain reliever > 24 hours or interferes with daily activity; Tenderness= Discomfort with movement; Erythema/Redness = 5.1-10 cm; Induration/Swelling = 5.1-10 cm and interferes with activity. Grade 3: Pain = Any use of narcotic pain reliever or prevents daily activity; Tenderness = Significant discomfort at rest; Erythema/Redness = > 10 cm; Induration/Swelling = > 10 cm or prevents daily activity. Grade 4: Pain = Emergency room (ER) visit or hospitalization; Tenderness = ER visit or hospitalization; Erythema/Redness = Necrosis or exfoliative dermatitis; induration/Swelling = Necrosis Grade 5: Death	Within 7 days after administration of L9LS
Participants With Systemic Adverse Events (AEs) - Year One	Number of participants with local adverse events occurring within 7 days after administration of L9LS. Systemic reactogenicity events included fever, feeling unusually tired or unwell, muscle aches, headache, chills, nausea, and joint pain. Adverse events were captured by Investigator examination and history from participants.	Within 7 days after the administration of L9LS
Severity of Systemic Adverse Events (AEs) - Year One	The severity of systemic AEs occurring after the administration of L9LS was assessed using the grading scale below: Grade 1: Fever = 37.5^oC-37.9^oC; Fatigue, Headache, Myalgia = No interference with activity; Nausea = no interference with activity or 1-2 episodes/hour Grade 2: Fever = 38^oC-38.4^oC; Fatigue, Myalgia = Some interference with activity; Headache = Repeated use of non-narcotic pain reliever > 24 hours or some interference with activity; Nausea = Some interference with activity or > 2 episodes/24 hours Grade 3: Fever = 38.5^oC-39.5^oC; Fatigue = Prevents daily activity; Headache =Significant; any use of narcotic pain reliever or prevents daily activity; Myalgia =Significant; prevents daily activity; Nausea = Prevents daily activity, requires outpatient intravenous hydration Grade 4: Fever = > 39.5^oC; Fatigue, Headache, Myalgia = Emergency room (ER) visit or hospitalization; Nausea = ER visit or hospitalization for hypotensive shock Grade 5: Death	Within 7 days after the administration of L9LS
Participants With Plasmodium Falciparum (Pf) Infection Detected by Microscopic Examination - Efficacy Study	Number of participants with Plasmodium falciparum (Pf) blood stage infection defined as blood smear-positive for Pf was assessed by microscopic examination of thick blood smear collected from participants from day 14 through week 28 (196 days) after administration of L9LS or placebo. Analysis was done as number of participants who had at least one positive blood smear.	Day 7 through week 28
Participants With Detectable Anti-drug Antibody (ADA) in Sera - Extension Study	Number of participants with detectable anti-drug antibody (ADA) in sera after exposure to L9LS. Serum was collected from participants at specific timepoints throughout the study, on days 0, 7, 28, 84, 168, and 196. The tier 3 assay was used to directly measure ADA's ability to impair L9LS binding to Plasmodium falciparum circumsporozoite protein (PfCSP). Analysis was done to determine number of participants with positive or detectable ADA in sera.	Measured through week 36
Maximum Total Plasma Concentration (Cmax) for L9LS - Extension Study	Maximum total plasma concentration (Cmax) following a dose of 150 mg or 300 mg L9LS. Serum collected on days 0, 7, 28, 84, 140, 196, & 252 after the administration of L9LS. Cmax for L9LS was obtained directly by visual inspection of the plasma concentration versus time profiles post dose. Analysis was done to determine each participant's observed maximum concentration based on all available timepoints and cumulative output was calculated as the central tendency and dispersion metric based on the observed maximum concentrations.	Measured through Week 36
Time to Maximum Plasma Concentration (TMax) for L9LS - Extension Study	Time to maximum total plasma concentration (Cmax) following a dose of 150 mg or 300 mg L9LS. Serum collected on days 0, 7, 28, 84, 140, 196, & 252 after the administration of L9LS. Tmax for L9LS was obtained directly by visual inspection of the plasma concentration versus time profiles. Analysis was done to determine the time (in days) at which the maximum observed concentration was achieved for each participant and cumulative output was calculated as the central tendency and dispersion metric based on the observed time of maximum concentration.	Measured through Week 36
Participants With Local Adverse Events (AEs) - Extension Study	Number of participants with local adverse events occurring within 7 days after administration of L9LS. Local reactogenicity included pain/tenderness, swelling, redness, bruising, and pruritus at the site of infusion. Adverse events were captured by Investigator examination and history from participants.	Within 7 days after administration of L9LS
Severity of Local Adverse Events (AEs) - Extension Study	The severity of local AEs was graded using the Toxicity Grading Scale for Healthy Adult and Adolescent Volunteers Enrolled in Preventive Clinical Trials. Grade 1: Pain = does not interfere with activity; Tenderness = mild discomfort to touch; Erythema/Redness = 2.5-5 cm; Induration/Swelling = 2.5-5 cm and does not interfere with activity. Grade 2: Pain = Repeated use of non-narcotic pain reliever > 24 hours or interferes with daily activity; Tenderness= Discomfort with movement; Erythema/Redness = 5.1-10 cm; Induration/Swelling = 5.1-10 cm and interferes with activity. Grade 3: Pain = Any use of narcotic pain reliever or prevents daily activity; Tenderness = Significant discomfort at rest; Erythema/Redness = > 10 cm; Induration/Swelling = > 10 cm or prevents daily activity. Grade 4: Pain = Emergency room (ER) visit or hospitalization; Tenderness = ER visit or hospitalization; Erythema/Redness = Necrosis or exfoliative dermatitis; induration/Swelling = Necrosis Grade 5: Death	Within 7 days after administration of L9LS
Participants With Systemic Adverse Events (AEs) - Extension Study	Number of participants with local adverse events occurring within 7 days after administration of L9LS. Systemic reactogenicity events included fever, feeling unusually tired or unwell, muscle aches, headache, chills, nausea, and joint pain. Adverse events were captured by Investigator examination and history from participants.	Within 7 days after the administration of L9LS
Severity of Systemic Adverse Events (AEs) - Extension Study	The severity of systemic AEs occurring after the administration of L9LS was assessed using the grading scale below: Grade 1: Fever = 37.5^oC-37.9^oC; Fatigue, Headache, Myalgia = No interference with activity; Nausea = no interference with activity or 1-2 episodes/hour Grade 2: Fever = 38^oC-38.4^oC; Fatigue, Myalgia = Some interference with activity; Headache = Repeated use of non-narcotic pain reliever > 24 hours or some interference with activity; Nausea = Some interference with activity or > 2 episodes/24 hours Grade 3: Fever = 38.5^oC-39.5^oC; Fatigue = Prevents daily activity; Headache =Significant; any use of narcotic pain reliever or prevents daily activity; Myalgia =Significant; prevents daily activity; Nausea = Prevents daily activity, requires outpatient intravenous hydration Grade 4: Fever = > 39.5^oC; Fatigue, Headache, Myalgia = Emergency room (ER) visit or hospitalization; Nausea = ER visit or hospitalization for hypotensive shock Grade 5: Death	Within 7 days after the administration of L9LS

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Participants With Plasmodium Falciparum (Pf) Infection Detected by Real-Time Polymerase Chain Reaction (RT-PCR)	Number of participants with Plasmodium falciparum (Pf) blood stage infection defined as blood sample positive for Pf was assessed by real-time polymerase chain reaction (RT-PCR) of blood sample collected from participants from day 0 through week 28 (196 days) after administration of L9LS or placebo. Analysis was done as number of participants who had at least one positive blood sample.	Measured through week 24 (dose escalation study) and week 28 (efficacy study)
Participants With Clinical Malaria - Pediatric Dose Escalation Study	Number of pediatric participants with clinical malaria during a single malaria season, defined by an illness accompanied by measured axillary fever ≥37.5°C, or history of fever (subjective or objective) in the previous 24 hours, and Plasmodium falciparum (Pf) asexual parasitemia >5,000 parasites/μL as detected from microscopic examination of thick blood smear. Assessment was done from day 0 through week 28 (196 days) after administration of L9LS or placebo. Subjective data, objective data and blood sample were collected from administration of intervention through week 28. Analysis was done as number of participants who had at least one symptom and positive blood sample.	Measured through Week 28
Participants With Clinical Malaria - Pediatric Efficacy Study	Number of pediatric participants with clinical malaria during a single malaria season, defined by an illness accompanied by measured axillary fever ≥37.5°C, or history of fever (subjective or objective) in the previous 24 hours, and Plasmodium falciparum (Pf) asexual parasitemia >5,000 parasites/μL as detected from microscopic examination of thick blood smear. Assessment was done from day 0 through week 28 (196 days) after administration of L9LS or placebo. Subjective data, objective data and blood sample were collected from administration of intervention through week 28. Analysis was done as number of participants who had at least one symptom and positive blood sample.	Measured through Week 28
Participants With Clinical Malaria Detected by Microscopic Examination of Thick Blood Smear - Pediatric Dose Escalation Study	Number of participants with clinical malaria during a single malaria season, defined by an illness accompanied by any level of Plasmodium Falciparum (Pf) asexual parasitemia as detected from microscopic examination of thick blood smear that results in the administration of anti-malarial treatment.	Measured through Week 28
Participants With Clinical Malaria Detected by Microscopic Examination of Thick Blood Smear - Pediatric Efficacy Study	Number of participants with clinical malaria during a single malaria season, defined by an illness accompanied by any level of Plasmodium Falciparum (Pf) asexual parasitemia as detected from microscopic examination of thick blood smear that results in the administration of anti-malarial treatment.	Measured through Week 24
Maximum Total Plasma Concentration (Cmax) for L9LS - Study Year One	Maximum total plasma concentration (Cmax) following a dose of 150 mg or 300 mg L9LS. Serum collected on days 0, 7, 28, 56, 84, 112, 140, 168, 196, 224, & 252 after the administration of L9LS. Cmax for L9LS was obtained directly by visual inspection of the plasma concentration versus time profiles post dose. Analysis was done to determine each participant's observed maximum concentration based on all available timepoints and cumulative output was calculated as the central tendency and dispersion metric based on the observed maximum concentrations.	Measured through Week 36
Time to Maximum Plasma Concentration (TMax) for L9LS - Study Year One	Time to maximum total plasma concentration (Cmax) following a dose of 150 mg or 300 mg L9LS. Serum was collected on days 0, 7, 28, 56, 84, 112, 140, 168, 196, 224, & 252 after administration of L9LS. Tmax for L9LS was obtained directly by visual inspection of the plasma concentration versus time profiles. Analysis was done to determine the time (in days) at which the maximum observed concentration was achieved for each participant and cumulative output was calculated as the central tendency and dispersion metric based on the observed time of maximum concentration.	Measured through Week 36

Collaborators and Investigators

• Sponsor: National Institute of Allergy and Infectious Diseases (NIAID)
• Collaborators: National Institutes of Health (NIH); University of Washington; Malaria Research and Training Center, Bamako, Mali; Harvard School of Public Health (HSPH); Indiana University School of Medicine; University of the Sciences, Techniques and Technologies of Bamako
• Investigators: Principal Investigator: Kassoum Kayentao, MD, MPH, PhD, Faculté de Médecine Pharmacie d'Odontostomatologie (FMPOS); Principal Investigator: Peter Crompton, MD, MPH, National Institutes of Health (NIH)

Publications and helpful links

General Publications

• Kayentao K, Ongoiba A, Preston AC, Healy SA, Hu Z, Skinner J, Doumbo S, Wang J, Cisse H, Doumtabe D, Traore A, Traore H, Djiguiba A, Li S, Peterson ME, Telscher S, Idris AH, Adams WC, McDermott AB, Narpala S, Lin BC, Serebryannyy L, Hickman SP, McDougal AJ, Vazquez S, Reiber M, Stein JA, Gall JG, Carlton K, Schwabl P, Traore S, Keita M, Zeguime A, Ouattara A, Doucoure M, Dolo A, Murphy SC, Neafsey DE, Portugal S, Djimde A, Traore B, Seder RA, Crompton PD; Mali Malaria mAb Trial Team. Subcutaneous Administration of a Monoclonal Antibody to Prevent Malaria. N Engl J Med. 2024 May 2;390(17):1549-1559. doi: 10.1056/NEJMoa2312775. Epub 2024 Apr 26.

Study record dates

Study Major Dates

• Study Start (Actual): March 18, 2022
• Primary Completion (Actual): April 20, 2024
• Study Completion (Actual): April 20, 2024

Study Registration Dates

• First Submitted: February 28, 2022
• First Submitted That Met QC Criteria: March 30, 2022
• First Posted (Actual): March 31, 2022

Study Record Updates

• Last Update Posted (Actual): July 10, 2025
• Last Update Submitted That Met QC Criteria: June 23, 2025
• Last Verified: June 1, 2025

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Vector Borne Diseases; Mosquito-Borne Diseases; Infections; Protozoan Infections; Parasitic Diseases; Malaria
• Other Study ID Numbers: 2022/34/CE/USTTB

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES

IPD Plan Description

Human data generated in this study for future research will be shared as follows:

• De-identified or identified data with approved outside collaborators under appropriate agreements.
• De-identified results or data in publication and/or public presentations.

• IPD Sharing Time Frame: Data will be shared at the time of publication or shortly thereafter.
• IPD Sharing Access Criteria: Data from this study may be requested from other researchers indefinitely after the completion of the primary endpoint by contacting Laboratory of Immunogenetics at NIH
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No