This is a phase 1b/2a, double-blind, randomized, placebo-controlled clinical trial to evaluate the safety, tolerability, and immunogenicity of the LEP-F1 + GLA-SE investigational vaccine compared to placebo.

The proposed clinical trial will establish an initial safety profile for the vaccine in a region endemic for leprosy. The trial will enroll both healthy participants and paucibacillary leprosy patients receiving standard-of-care therapy. Safety at the lower vaccine dose will be demonstrated in healthy participants prior to antigen dose-escalation. Further, safety in all healthy participants will be demonstrated prior to enrolling leprosy patients.

Participants will be randomized within each Group to receive three doses of vaccine or placebo administered IM on Days 0, 28, and 56. Participants will be monitored for one year following the last study injection.

Phase 1b

Inclusion Criteria:

1. Men and women between 18 and 55 years old.
2. They should be in good general health, confirmed by a medical history and physical examination, with negative clinical evaluation for leprosy.
3. Female participants of childbearing age should have a negative serum pregnancy test at screening and a negative urine pregnancy test on study vaccination days (D0, D28 and D56). They must not be breast-feeding and are required to use at least one contraceptive method from the time of study inclusion (Day 0) until 30 days after the last injection if they have sex with men.
4. Screening laboratory tests with normal, within laboratory reference limits for:: sodium, potassium, AST, ALT, total bilirubin, alkaline phosphatase, creatinine, glucose, total leukocyte count, hemoglobin and platelet count. Abnormal results may be repeated at the discretion of the Principal Investigator and/or sub-investigators, who may share doubts with the sponsor's Scientific Leader and if necessary with the DSMB.
5. Negative serological tests for: HIV 1/2 antibody, hepatitis B surface antigen (HBsAg), and hepatitis C virus (HCV) antibody.
6. Normal or not clinically significant urinalysis as determined by the study doctor or designee. Abnormal results may be repeated at the discretion of the Principal Investigator.
7. Must be able to complete the study adverse events diary.
8. Must consent to participate in the study, be able and willing to make all evaluation visits, be accessible by telephone or home visits, and live in the region until study follow-up completion.
9. Having completed the primary vaccination course for Covid 19, at least 14 days before inclusion in the study. If 14 days have not been completed, the participant may be rescheduled for a new eligibility assessment

Exclusion Criteria (Phase 1b)

Individuals who meet ANY of the following criteria will be considered ineligible:

1. History of infection with Mycobacterium leprae.
2. History of exposure to experimental products containing GLA-SE.
3. History of active or documented latent tuberculosis.
4. History of previous infection with other non-tuberculous mycobacteria.
5. Participation in another trial protocol and/or receipt of any trial products in the last 3 months prior to screening.
6. Treatment with immunosuppressive drugs (eg oral or injected steroids, such as prednisone; high doses of inhaled steroids) or cytotoxic therapies (eg chemotherapy or radiation) within 6 months prior to screening.
7. Have received blood transfusion within the last 3 months prior to screening.
8. Donated blood products (platelets, whole blood, plasma, etc.) within the last month prior to screening.
9. Received any vaccine 1 month prior to screening or planned immunizations during the follow-up from D0 to D63 and D154 to D168.
10. History of autoimmune disease or other immunosuppressive causes.
11. History of any other acute or chronic decompensated disease (including cardiovascular, pulmonary, neurological, hepatic, rheumatic, haematological, metabolic or renal disease, uncontrolled hypertension) or use of medication that, in the opinion of the Principal Investigator, may interfere with safety or immunogenicity of the vaccine.
12. Rash, tattoos or any other dermatological condition that may adversely affect the injection site of the vaccine or interfere with its evaluation.
13. Body mass index (BMI) ≥ 32.
14. Systemic arterial hypertension (systolic > 150 or diastolic > 95).
15. History of psychiatric illness with current medication use.
16. Alcohol or drug abuse in the last 6 months prior to screening.
17. Chronic smoker (1 pack or more per day).
18. History of previous anaphylaxis or severe allergic reaction to unknown vaccines or allergens.
19. Individuals who do not wish to cooperate with all procedures recommended in the study protocol.

Inclusion Criteria (Phase 2a)

Participants must meet ALL of the following criteria listed below to be included in the study:

1. Men and women between 18 and 55 years old.
2. Diagnosis of PB leprosy (BI=0) before MDT treatment
3. Female participants of childbearing age should have a negative serum pregnancy test at screening and a negative urine pregnancy test on study vaccination days (D0, D28 and D56). They must not be breast-feeding and are required to use at least one contraceptive method from the time of study inclusion (Day 0) until 30 days after the last injection if they have sex with men.
4. Screening laboratory tests with normal, within laboratory reference limits for: sodium, potassium, AST, ALT, total bilirubin, alkaline phosphatase, creatinine, glucose, total leukocyte count, hemoglobin and platelet count. Abnormal results may be repeated at the discretion of the Principal Investigator and/or sub-investigators, who may share doubts with the sponsor's Scientific Leader and if necessary with the DSMB.
5. Negative serological tests for: HIV 1/2 antibody, hepatitis B surface antigen (HBsAg), and hepatitis C virus (HCV) antibody.
6. Normal or not clinically significant urinalysis as determined by the study doctor or designee. Abnormal results may be repeated at the discretion of the Principal Investigator.
7. Must be able to complete the study adverse events diary.
8. Must consent to participate in the study, be able and willing to make all evaluation visits, be accessible by telephone or home visits, and live in the region until study follow-up completion.
9. Having completed the primary vaccination course for Covid 19, at least 14 days before inclusion in the study. If 14 days have not been completed, the participant may be rescheduled for a new eligibility assessment

Exclusion Criteria (Phase 2a)

Individuals who meet ANY of the following criteria will be considered ineligible:

1. Previous treatment for leprosy.
2. History of exposure to experimental products containing GLA-SE.
3. History of active or documented latent tuberculosis.
4. History of previous infection with other non-tuberculous mycobacteria.
5. Participation in another trial protocol and/or receipt of any trial products in the last 3 months prior to screening.
6. Treatment with immunosuppressive drugs (eg oral or injected steroids, such as prednisone; high doses of inhaled steroids) or cytotoxic therapies (eg chemotherapy or radiation) within 6 months prior to screening.
7. Have received blood transfusion within the last 3 months prior to screening.
8. Donated blood products (platelets, whole blood, plasma, etc.) within the last month prior to screening.
9. Received any vaccine 1 month prior to screening or planned immunizations during the follow-up from D0 to D63 and D154 to D168.
10. History of autoimmune disease or other immunosuppressive causes.
11. History of any other acute or chronic decompensated disease (including cardiovascular, pulmonary, neurological, hepatic, rheumatic, haematological, metabolic or renal disease, uncontrolled hypertension) or use of medication that, in the opinion of the Principal Investigator, may interfere with safety or immunogenicity of the vaccine.
12. Rash, tattoos or any other dermatological condition that may adversely affect the injection site of the vaccine or interfere with its evaluation.
13. Body mass index (BMI) ≥ 32.
14. Systemic arterial hypertension (systolic > 150 or diastolic > 95).
15. History of psychiatric illness with current medication use.
16. Alcohol or drug abuse in the last 6 months prior to screening.
17. Chronic smoker (1 pack or more per day).
18. History of previous anaphylaxis or severe allergic reaction to unknown vaccines or allergens.
19. Individuals who do not wish to cooperate with all procedures recommended in the study protocol.

Vital signs are performed after participants have sat for five minutes without hot or cold drinks or smoking for the past five minutes. Vital signs can be performed up to three times to allow resolution of transient conditions.

This is a double-blind study. Participants, investigators, study personnel performing any study-related assessments following study injection, and laboratory personnel performing immunology assays will be blinded to treatment assignment.