Phase 1/2 Study of Chlamydia Trachomatis mRNA Vaccine in Adults Aged 18 to 29 Years

A Phase 1/2, Randomized, Placebo-controlled, Multi-arm, Dose-finding Study to Evaluate the Safety, Immunogenicity, and Efficacy of a Chlamydia Trachomatis mRNA Vaccine Candidate in Adults Aged 18 to 29 Years

The purpose of this study is to evaluate the safety, efficacy, and immunogenicity of different dose levels (low, medium, and high) of Chlamydia messenger ribonucleic acid (mRNA) Vaccine candidate in adult participants aged 18 to 29 years.

This study will consist of 3 Sentinel Cohorts and a Main Cohort, with the Sentinel Cohorts assessing the safety of the different dose levels in a stepwise manner.

All participants will be followed up to 12 months after the last study intervention administration. Thus, the expected duration of the participant's involvement will be 18 months.

Study Overview

• Status: Recruiting
• Conditions: Chlamydia Trachomatis Immunization
• Intervention / Treatment: Biological: Chlamydia mRNA Vaccine; Other: Placebo

• Study Type: Interventional
• Enrollment (Estimated): 1560
• Phase: Phase 2; Phase 1

Contacts and Locations

• Study Contact: Name: Trial Transparency email recommended (Toll free for US & Canada); Phone Number: option 6 800-633-1610; Email: Contact-US@sanofi.com

Study Locations

• Australia
  • Australian Capital Territory
    • Bruce, Australian Capital Territory, Australia, 2617
      • Recruiting
      • Investigational Site Number : 0360002
  • New South Wales
    • Maroubra, New South Wales, Australia, 2035
      • Recruiting
      • Investigational Site Number : 0360006
    • Sydney, New South Wales, Australia, 2010
      • Recruiting
      • Investigational Site Number : 0360005
  • Queensland
    • Albion, Queensland, Australia, 4010
      • Recruiting
      • Investigational Site Number : 0360001
    • Morayfield, Queensland, Australia, 4506
      • Recruiting
      • Investigational Site Number : 0360004
    • Southport, Queensland, Australia, 4222
      • Recruiting
      • Investigational Site Number : 0360003
  • Victoria
    • Melbourne, Victoria, Australia, 3000
      • Recruiting
      • Investigational Site Number : 0360010

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Aged 18 to 29 years on the day of inclusion
• New sex partner within the past 6 months, or more than one current sex partner, or partner with known previous or coexisting sexually transmitted infection (STI), or inconsistent condom use

• A female participant is eligible to participate if she is not pregnant or breastfeeding and one of the following conditions applies:

  • Is of non-childbearing potential. To be considered of non-childbearing potential, a female must be surgically sterile.

OR

• Is of childbearing potential and agrees to use an effective contraceptive method from at least 4 weeks prior to study intervention administration until at least 4 weeks after the last study intervention administration.

• A female participant of childbearing potential must have a negative highly sensitive pregnancy test (urine or serum as required by local regulation) at the screening visit and before each subsequent study intervention administration

Exclusion Criteria:

• Any screening laboratory parameter with laboratory abnormalities as per local reference range and that are greater than Grade 2 or deemed clinically significant in the opinion of the Investigator
• Participants who are Chlamydia trachomatis (CT) and/or Neisseria gonorrhea (NG) NAAT positive at screening visit
• Self-reported or documented seropositivity for HIV antigen and/or antibodies (Abs), hepatitis B virus surface antigen (HBsAg), hepatitis B core antibodies (HBcAbs), or hepatitis C virus (HCV) Abs infection at screening visit
• Known or suspected congenital or acquired immunodeficiency; or receipt of immunosuppressive therapy, such as anti-cancer chemotherapy or radiation therapy, within the preceding 6 months; or long-term systemic corticosteroid therapy (prednisone or equivalent for more than 2 consecutive weeks within the past 3 months)
• Known systemic hypersensitivity to any of the study intervention components, or history of a life-threatening reaction to the study intervention(s) used in the study or to a product containing any of the same substances
• Previous history of myocarditis, pericarditis, and/or myopericarditis
• Known history of previous history of Guillain-Barre syndrome and other immune mediated demyelinating conditions that include but are not limited to Multiple Sclerosis (MS), Neuromyelitis Optica (NMO), acute disseminated encephalomyelitis (ADEM), Transverse myelitis
• Screening electrocardiogram (ECG) value that is consistent with possible myocarditis, pericarditis, and/or myopericarditis or screening ECG that demonstrates clinically relevant abnormalities, per investigator, that may affect participant safety or study results
• Self-reported thrombocytopenia, contraindicating intramuscular injection, based on investigator's judgment
• Bleeding disorder, or receipt of anticoagulants in the 3 weeks preceding inclusion, contraindicating intramuscular injection, based on investigator's judgment
• Chronic illness that, in the opinion of the investigator, is at a stage where it might interfere with study conduct or completion
• Moderate or severe acute febrile illness (temperature ≥ 38.0°C [≥ 100.4°F]) on the day of study intervention administration. A prospective participant should not be included in the study until the condition has resolved or the febrile event has subsided
• Alcohol, prescription drug, or substance abuse that, in the opinion of the Investigator, might interfere with the study conduct or completion
• Receipt of any mRNA vaccine/product in the 2 months preceding study enrollment or planned receipt of any mRNA vaccine/product within the 2 months following any study intervention administration
• Receipt of any vaccine (other than the study vaccine) in the 4 weeks preceding any study intervention administration or planned receipt of any vaccine (other than the study vaccine) in the 4 weeks following any study intervention administration, except influenza which may be received at least 2 weeks before or 2 weeks after any study vaccination
• Receipt of immune globulins, blood, or blood-derived products in the past 3 months

Note: The above information is not intended to contain all considerations relevant to a patient's potential participation in a clinical trial.

Study Plan

How is the study designed?

Design Details

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

Number of Arms

16

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Sentinel Cohort A Group 1: Chlamydia trachomatis Seronegative; Participants will receive three low dose injections of Chlamydia mRNA Vaccine	Biological: Chlamydia mRNA Vaccine; Pharmaceutical Form: Suspension for injection Route of Administration: Intramuscular injection
Experimental: Sentinel Cohort B Group 2: Chlamydia trachomatis Seronegative; Participants will receive three medium dose injections of Chlamydia mRNA Vaccine	Biological: Chlamydia mRNA Vaccine; Pharmaceutical Form: Suspension for injection Route of Administration: Intramuscular injection
Experimental: Sentinel Cohort C Group 3: Chlamydia trachomatis Seronegative; Participants will receive three high dose injections of Chlamydia mRNA Vaccine	Biological: Chlamydia mRNA Vaccine; Pharmaceutical Form: Suspension for injection Route of Administration: Intramuscular injection
Placebo Comparator: Sentinel Cohort A, B and C Group 4: Chlamydia trachomatis Seronegative; Participants will receive three injections of Placebo	Other: Placebo; Pharmaceutical Form: Solution for injection Route of Administration: Intramuscular injection
Experimental: Sentinel Cohort A Group 5: Chlamydia trachomatis Seropositive; Participants will receive three low dose injections of Chlamydia mRNA Vaccine	Biological: Chlamydia mRNA Vaccine; Pharmaceutical Form: Suspension for injection Route of Administration: Intramuscular injection
Experimental: Sentinel Cohort B Group 6: Chlamydia trachomatis Seropositive; Participants will receive three medium dose injections of Chlamydia mRNA Vaccine	Biological: Chlamydia mRNA Vaccine; Pharmaceutical Form: Suspension for injection Route of Administration: Intramuscular injection
Experimental: Sentinel Cohort C Group 7: Chlamydia trachomatis Seropositive; Participants will receive three medium dose injections of Chlamydia mRNA Vaccine	Biological: Chlamydia mRNA Vaccine; Pharmaceutical Form: Suspension for injection Route of Administration: Intramuscular injection
Placebo Comparator: Sentinel Cohort A, B and C Group 8: Chlamydia trachomatis Seropositive; Participants will receive three injections of Placebo	Other: Placebo; Pharmaceutical Form: Solution for injection Route of Administration: Intramuscular injection
Experimental: Main Cohort Group 9: Chlamydia trachomatis Seronegative; Participants will receive three low dose injections of Chlamydia mRNA Vaccine	Biological: Chlamydia mRNA Vaccine; Pharmaceutical Form: Suspension for injection Route of Administration: Intramuscular injection
Experimental: Main Cohort Group 10: Chlamydia trachomatis Seronegative; Participants will receive three medium dose injections of Chlamydia mRNA Vaccine	Biological: Chlamydia mRNA Vaccine; Pharmaceutical Form: Suspension for injection Route of Administration: Intramuscular injection
Experimental: Main Cohort Group 11: Chlamydia trachomatis Seronegative; Participants will receive three high dose injections of Chlamydia mRNA Vaccine	Biological: Chlamydia mRNA Vaccine; Pharmaceutical Form: Suspension for injection Route of Administration: Intramuscular injection
Placebo Comparator: Main Cohort Group 12: Chlamydia trachomatis Seronegative; Participants will receive three injections of Placebo	Other: Placebo; Pharmaceutical Form: Solution for injection Route of Administration: Intramuscular injection
Experimental: Main Cohort Group 13: Chlamydia trachomatis Seropositive; Participants will receive three low dose injections of Chlamydia mRNA Vaccine	Biological: Chlamydia mRNA Vaccine; Pharmaceutical Form: Suspension for injection Route of Administration: Intramuscular injection
Experimental: Main Cohort Group 14: Chlamydia trachomatis Seropositive; Participants will receive three medium dose injections of Chlamydia mRNA Vaccine	Biological: Chlamydia mRNA Vaccine; Pharmaceutical Form: Suspension for injection Route of Administration: Intramuscular injection
Experimental: Main Cohort Group 15: Chlamydia trachomatis Seropositive; Participants will receive three high dose injections of Chlamydia mRNA Vaccine	Biological: Chlamydia mRNA Vaccine; Pharmaceutical Form: Suspension for injection Route of Administration: Intramuscular injection
Placebo Comparator: Main Cohort Group 16: Chlamydia trachomatis Seropositive; Participants will receive three injections of Placebo	Other: Placebo; Pharmaceutical Form: Solution for injection Route of Administration: Intramuscular injection

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Presence of immediate unsolicited systemic adverse events (AEs)	Number of participants with immediate unsolicited systemic adverse events (AEs) reported in the 30 minutes after each vaccine injection.	Within 30 minutes after each vaccine injection
Presence of solicited injection site and systemic reactions	Number of participants with solicited injection site and systemic reactions occurring up to 7 days after each vaccine injection.	Up to 7 days after each vaccine injection
Presence of unsolicited AEs	Participants with unsolicited AEs reported up to 28 days after each vaccine injection.	Up to 28 days after each vaccine injection.
Presence of medically attended adverse events (MAAEs)	Number of participants with MAAEs reported after each vaccine injection and up to 6 months after last vaccine injection.	Up to 6 months after last vaccine injection
Presence of all serious AEs (SAEs) and all adverse events of special interest (AESIs)	Number of participants with SAEs and all AESIs reported after each vaccine injection and up to 12 months after last vaccine injection	Up to 12 months after last vaccine injections
Presence of related SAEs, and fatal SAEs	Number of participants with related SAEs, and fatal SAEs throughout the study	Throughout the study, appriximatley 18 months
Presence of out-of-range biological test results (Sentinel Cohort and Safety Subset of Main Cohort)	Number of participants with out-of-range biological test results up to 7 days after each vaccine injection	Up to 7 days after each vaccination injections

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Assessment of serum binding antibodies to specific Chlamydia trachomatis antigens and whole bacteria in immunogenicity subset	Binding Immunoglobulin (Ig) will be measured using a multiplex electrochemiluminescent (ECL) based binding assay	Before each vaccine injection through 1 month after each vaccine injection
Geometric mean cell-mediated immune response of antigen-specific T helper type 1 (Th1) and T helper type 2 (Th2) cytokine-producing T cells by phenotype	Geometric mean cell-mediated immune responses will be measured by an intracellular cytokine staining assay over time	Before each vaccine injection through 1 month after each vaccine injection

Collaborators and Investigators

• Sponsor: Sanofi

Publications and helpful links

Helpful Links

• VAV00023 Plain Language Results Summary

Study record dates

Study Major Dates

• Study Start (Actual): March 27, 2025
• Primary Completion (Estimated): January 3, 2028
• Study Completion (Estimated): January 3, 2028

Study Registration Dates

• First Submitted: March 17, 2025
• First Submitted That Met QC Criteria: March 17, 2025
• First Posted (Actual): March 24, 2025

Study Record Updates

• Last Update Posted (Actual): April 8, 2026
• Last Update Submitted That Met QC Criteria: April 2, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Chlamydia
• Additional Relevant MeSH Terms: Urogenital Diseases; Genital Diseases; Infections; Communicable Diseases; Sexually Transmitted Diseases; Bacterial Infections; Bacterial Infections and Mycoses; Gram-Negative Bacterial Infections; Chlamydiaceae Infections; Sexually Transmitted Diseases, Bacterial; Chlamydia Infections
• Other Study ID Numbers: VAV00023; U1111-1308-7349 (Other Identifier: WHO ICTRP)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org

Drug and device information, study documents

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