Safety and Immunogenicity of Pfs25M-EPA/AS01 and Pfs230D1M-EPA/AS01 Vaccines, Transmission Blocking Vaccines Against Plasmodium Falciparum, at Full and Fractional Dosing in Adults in Mali

A vaccine to interrupt malaria transmission (VIMT) would be a valuable tool for local elimination or eradication of this disease, and may contain components that block transmission to mosquitoes (such as Pfs25 or Pfs230) or that prevent human infection (such as the vaccine RTS,S). Pfs25 and Pfs230, surface antigens of zygotes and ookinetes (and gametocytes for Pfs230) in the mosquito stage of P. falciparum, are the lead candidates for a malaria transmission blocking vaccine (TBV). Recombinant Pfs25M and recombinant Pfs230D1M have each been conjugated to P. aeruginosa ExoProtein A (EPA) and adjuvanted with AS01. Our ongoing experience with Pfs25M-EPA and Pfs230D1M-EPA in Malian adult trial participants, and the extensive experience with the AS01 adjuvants in African children and adults, justify conducting the first-in-human trial of Pfs25M-EPA and Pfs230D1M-EPA with AS01 in Malian adults. This dose-escalating phase 1 study will determine safety, immunogenicity, and functional activity of these vaccines in Malian adults. Pfs25M-EPA + Pfs230D1M-EPA in AS01 will be assessed by mosquito feeding assays in Malian adults for evidence that they may reduce the number of malaria transmission events in study subjects.

A total of 305 subjects will be enrolled at multiple sites in Mali, West Africa to receive escalating doses of a malaria transmission blocking vaccine (s): Pfs25M-EPA/AS01, Pfs230D1M-EPA/AS01, or simultaneous administration of Pfs25M-EPA/AS01 and Pfs230D1M-EPA/AS01; or a comparator vaccine (ENERGIX-B). Enrollment within each group will be staggered for additional safety and subjects will only be enrolled into the co-administration group once each individual dose has been administered. Subjects will be followed for at least 6 months after the last vaccination. Safety outcomes will be local and systemic adverse events and serious adverse events. Immunogenicity outcomes will be antibody responses as measured by ELISA against recombinant Pfs25, Pfs230, EPA, CSP, and B cell and T cell responses. Functional activity of the induced antibodies will be assessed in TBV arms by standard membrane feeding assays conducted at the National Institute of Allergy and Infectious Diseases, and activity that interrupts malaria transmission will be measured in all arms by direct skin feeding assays in Mali.

Subjects in the open label safety cohorts (Arms 1a, 1b, 2a, 2b, 3a, 3b, 4a, 4b) will be offered reenrollment for follow-up laboratory assessment to explore the duration of immunogenicity and functional activity at approximately 9, 12 months post vaccination. Following scheduled, intentional unblinding, subjects enrolled in Arms 2c, 2d, and 4c will be provided the opportunity to re-enroll for a fourth vaccination (Arm 2c and 2d with 40 microgram dose of Pfs230D1M-EPA/AS01; Arm 4c with Menatctra) approximately 1 year post vaccination #3. Subjects in these arms will also be eligible to re-enroll for follow up of duration of immunogenicity and functional activity at approximately 9, 12 months post vaccination if they choose not to enroll to recive the booster vaccination. Subjects will be followed similarly to the previous year for safety, immunogenicity, and functional activity.

• Pfs25M-EPA (Biological): The PpPfs25M and EcEPA lots, both manufactured at Walter Reed Bioproduction facility (Silver Spring, Maryland) in cGMP compliance, were used to manufacture the conjugate. PpPfs25M is a Pichia- expressed recombinant Pfs25 with a molecular mass of 18,713 Daltons.The Pfs25M- EPA was formulated as conjugated Pfs25M in 4 mM PBS to a 2X dilution of the high dose (188 (Micro)g/ml in 0.5 ml volume) in cGMP compliance at Walter Reed Bio-production facility in April 2016 and will be provided as a single use vial.
• Pfs230D1M-EPA (Biological): The Pfs230D1M-EPA was formulated as conjugated Pfs230D1M in 4 mM PBS to a 2X dilution of the high dose (160 (Micro)g/ml in 0.5 ml volume) in cGMP compliance at Walter Reed Bio-production facility in April 2016 and will be provided as a single use vial.
• AS01 (Other): AS01B adjuvant will also be provided as a single use vial by GSK, 100 microgram/mL MPL and 100microgram/mL QS21 in a liposomal formulation in a volume of 0.625 mL. One dose injected of AS01B corresponds to 50 μg QS21 and 50 μg MPL.
• Engerix-B (Biological): ENGERIX-B (hepatitis B vaccine; recombinant): is a sterile suspension of noninfectious hepatitis B virus surface antigen (HBsAg) for intramuscular administration. It contains purified HBsAg obtained by culturing genetically engineered Saccharomyces cerevisiae cells, which carry the surface antigen gene of the hepatitis B virus. Each 1-mL adult dose contains 20 g of HBsAg adsorbed on 0.5 mg aluminum as aluminum hydroxide. FDA approved for persons 20 years of age and older for a series of 3 doses on a 0-, 1-, 6-month schedule.
• Menactra (Biological): Menactra is FDA approved for active immunization to prevent invasive meningococcal disease caused by Neisseria meningitidis serogroups A, C, Y, and W-135 (but does not protect against serotype B) for use in individuals 9 months through 55 years of age
• Normal Saline (Other): Sterile isotonic (0.9%) normal saline will be commercially procured in the US and shipped to Mali at ambient temperature. Normal saline will be administered in a 0.5 mL dose as an intramuscular injection. Normal saline will also be used for diluting Pfs25M-EPA and Pfs230D1M-EPA prior to formulation with AS01B for the lower dose groups in Bamako, Mali.
• Coartem (Drug): Artemether/lumefantrine (Coartem(R)) is a licensed antimalarial in the US and Mali for treatment of uncomplicated malaria. It has an excellent safety profile and is widely used to treat malaria. Subjects who may have any contraindications to the use of these drugs will be excluded at screening. Coartem will be dosed with food and administered over 3 days for a total of 6 doses, as per package insert and standard adult dosing

Primary outcomes

• Number of Participants With Local and Systemic Adverse Events in Year 1 [Within 7 days after each vaccination]: Number of participants with local and systemic adverse events (AEs) graded by severity occurring within 7 days after each vaccine
• Number of Participants With Local and Systemic Adverse Events in Year 2 [Within 7 days after each vaccination]: Number of participants with local and systemic adverse events (AEs) graded by severity occurring within 7 days after each vaccine

Sex: All, ages: 18 Years to 52 Years

-INCLUSION CRITERIA:

1. Age greater than or equal to 18 and less than or equal to 50 years.
2. Available for the duration of the trial.
3. Able to provide proof of identity to the satisfaction of the study clinician completing the enrollment process.
4. In good general health and without clinically significant medical history in the opinion of the investigator.
5. Females of childbearing potential must be willing to use reliable contraception (as defined below) from 21 days prior to Study Day 0 (Study Day 476 for re-enrollment) and then until 3 months after last vaccination.

   * Reliable methods of birth control include one of the following: confirmed pharmacologic contraceptives (parenteral) delivery; intrauterine or implantable device.
   * Reliable methods of birth control include concurrent use of a pharmacologic and a barrier method, i.e. two of the following: confirmed pharmacologic contraceptives (oral, transdermal) delivery or vaginal ring AND condoms with spermicide or diaphragm with spermicide.
   * Non-childbearing women will also be required to report date of last menstrual period, history of surgical sterility (i.e. tubal ligation, hysterectomy) or premature ovarian insufficiency (POI), and will have a baseline urine or serum pregnancy test performed.
6. Willingness to have blood samples stored for future research.
7. Willingness to undergo DSFs (Arms 3c, 3d, 4c only).
8. Known resident of Bancoumana or Doneguebougou or surrounding area or known student or long term resident (more than 1 year) of Bamako/Sotuba, Mali

EXCLUSION CRITERIA:

1. Pregnancy as determined by a positive urine or serum human choriogonadotropin (beta-hCG) test (if female).

   NOTE: Pregnancy is also a criteria for discontinuation of any further dosing or non-safety related interventions for that subject.
2. Currently breast-feeding (if female).
3. Behavioral, cognitive, or psychiatric disease that in the opinion of the investigator affects the ability of the participant to understand and comply with the study protocol.
4. Hemoglobin, WBC, absolute neutrophils, and platelets outside the local laboratory-defined limits of normal (subjects may be included at the investigator s discretion for not clinically significant values outside of normal range and less than or equal to Grade 1).
5. 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 outside of normal range and less than or equal to Grade 1).
6. Infected with human immunodeficiency virus (HIV), hepatitis C virus (HCV), or hepatitis B (HBV).
7. 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.
8. History of receiving any investigational product within the past 30 days.
9. Participation or planned participation in a clinical trial with an investigational product prior to completion of the follow up visit 28 days following last vaccination OR planned participation in an investigational vaccine study until the last required protocol visit
10. Subject has had medical, occupational, or family problems as a result of alcohol or illicit drug use during the past 12 months.
11. History of a severe allergic reaction or anaphylaxis.
12. 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.
13. Pre-existing autoimmune or antibody-mediated diseases including but not limited to: systemic lupus erythematosus, rheumatoid arthritis, multiple sclerosis, Sj(SqrRoot)(Delta)gren s syndrome, or autoimmune thrombocytopenia.
14. Known immunodeficiency syndrome.
15. Known asplenia or functional asplenia.
16. Use of chronic (greater than or equal to 14 days) oral or intravenous corticosteroids (excluding topical or nasal) at immunosuppressive doses (i.e., prednisone >10 mg/day) or immunosuppressive drugs within 30 days of Study Day 0.
17. Prior to Study Day 0 and every subsequent vaccination day, receipt of a live vaccine within the past 4 weeks or a killed vaccine within the past 2 weeks.
18. Receipt of immunoglobulins and/or blood products within the past 6 months.
19. Previous receipt of an investigational malaria vaccine in the last 5 years.
20. History of severe reaction to mosquito bites (Arms 3c, 3d, 4c only)
21. History of allergy to the comparator vaccine (such as latex, yeast, or previous Hepatitis B vaccine)
22. Known allergies or contraindications (such as significant cardiac disease; prolonged QTc >450 ms; currently taking medications that may prolong your QTc; serious side effects from Coartem in the past) to study treatment (Coartem \[artemether/lumefantrine\]) (Arms 3c, 3d, 4c only)
23. Other condition that in the opinion of the investigator would jeopardize the safety or rights of a participant participating in the trial, interfere with the evaluation of the study objectives, or would render the subject unable to comply with the protocol.

Participant flow

Outcome results

• Number of Participants With Local and Systemic Adverse Events in Year 1 (Primary), Count of participants, Participants: Pilot/Safety Arm 1a: Dosing Interval 0, 28, 168 Days 2; Pilot/Safety Arm 1b: Dosing Interval 0, 28, 168 Days 6; Pilot/Safety Arm 2a: Dosing Interval 0, 28, 168 Days 4; Pilot/Safety Arm 2b: Dosing Interval 0, 28, 168 Days 6; Safety/Efficacy Arm 2c: Dosing Interval 0, 28, 168, 476 Days 31; Safety/Efficacy Arm 2d: Dosing Interval 0, 28, 168, 476 Days 25; Pilot/Safety Arm 3a: Dosing Interval 0, 28, 168 Days 3; Pilot/Safety Arm 3b: Dosing Interval 0, 28, 168 Days 8; Pilot/Safety Comparator Arm 4a: Dosing Interval 0, 28, 168 Days 2; Pilot/Safety Comparator Arm 4b: Dosing Interval 0, 28, 168 Days 3; Safety Comparator & Efficacy Comparator Arm 4c: Dosing Interval 0, 28, 168, 476 Days 52
• Number of Participants With Local and Systemic Adverse Events in Year 2 (Primary), Count of participants, Participants: Safety/Efficacy Arm 2c: Dosing Interval 0, 28, 168, 476 Days 28; Safety/Efficacy Arm 2d: Dosing Interval 0, 28, 168, 476 Days 27; Safety Comparator & Efficacy Comparator Arm 4c: Dosing Interval 0, 28, 168, 476 Days 20

Adverse events

Time frame: Adverse Events were assessed 7 days from the time of each vaccination in Years 1 and 2

Serious adverse events by term

Other adverse events by term

Limitations and caveats: No limitations or caveats to report.

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• Results publication: Cao Y, da Silva Araujo M, Lorang CG, Dos Santos NAC, Tripathi A, Vinetz J, Kumar N. Distinct immunogenicity outcomes of DNA vaccines encoding malaria transmission-blocking vaccine target antigens Pfs230D1M and Pvs230D1. Vaccine. 2025 Feb 15;47:126696. doi: 10.1016/j.vaccine.2024.126696. Epub 2025 Jan 8. PMID 39787798

• Study Protocol and Statistical Analysis Plan (PDF, 2020-07-21)

• Patrick E Duffy, M.D., Principal investigator, National Institute of Allergy and Infectious Diseases (NIAID)