mRNA Vaccine Candidate for Chlamydia Receives FDA Grants Fast Track Designation

The FDA has granted fast track designation to an mRNA vaccine candidate from Sanofi for the prevention of chlamydia infection. The designation is aimed to address the unmet public health need caused by the bacterial infection.¹

Image credit: Christoph Burgstedt | stock.adobe.com

According to the CDC, chlamydia is a common sexually transmitted infection (STI) caused by the bacterium Chlamydia trachomatis that can trigger infection among men and women who are sexually active.^1,2

Although chlamydia usually does not present symptoms, it can cause severe health issues even without symptoms. This includes permanent damage to a woman’s reproductive system and potentially fatal ectopic pregnancy. Asymptomatic individuals are often left untreated, which could lead to unintentional transmission; however, if symptoms do occur, they may not appear for several weeks. In women, this includes abnormal vaginal discharge and a burning sensation when urinating. In men, symptoms include penis discharge, a burning sensation when urinating, as well as pain and swelling in 1 or both testicles.²

A total of 129 million cases of chlamydia among adults aged 15 to 49 years were reported in 2020, with the highest rates among young adults, according to study authors.¹

“Millions of people currently live with undiagnosed chlamydia, including asymptomatic infection that can also cause severe long-term health effects if left untreated. Antibiotics to treat chlamydia have not been successful in controlling rising infection rates,” Jean-François Toussaint, global head of vaccines research and development, said in a news release. “With our program we aim to make chlamydia a preventable disease through vaccination.”¹

Doxycycline and azithromycin are antibiotics that are commonly used to clear chlamydia in 1 to 2 weeks; however, they are not intended to reverse the harm the bacteria caused to the body prior to treatment, emphasizing the need for a preventative vaccine.³

The chlamydia vaccine candidate is indicated to protect against primary genital tract infection and reinfection by Chlamydia trachomatis. Researchers are planning a randomized, placebo-controlled, multi-arm, dose-finding phase 1/2 clinical trial (NCT06891417) to assess the immunogenicity and safety of the vaccine candidate, focusing on adults aged 18 to 29 years.¹

The study (NCT06891417) will include 3 sentinel cohorts and a main cohort— the sentinel cohorts will aim to assess the safety of different dose levels. Individuals will be randomly assigned to receive 3 intramuscular injections of the chlamydia mRNA vaccine candidate or placebo. All study participants will require a 12-month follow-up after the last study intervention administration.⁴

The primary end points of the study will evaluate vaccine safety by tracking the following: immediate adverse events (AEs) within 30 minutes; expected reactions within 7 days; unexpected events within 28 days; medically attended events within 6 months; serious AEs within 12 months; and all serious vaccine-related events throughout the 18-month study. It will also assess out-of-range biological test results within 7 days of vaccination in specific cohorts.⁴

By targeting Chlamydia trachomatis with a preventative vaccine, Sanofi seeks to address a critical unmet public health need, potentially reversing the rising rates of chlamydia infection. The phase 1/2 clinical trial will provide crucial data on the vaccine's tolerability and pave the way for future development and potential widespread use.

REFERENCES

1. Press Release: Chlamydia vaccine candidate granted fast track designation by the US FDA. Sanofi. News release. March 26, 2025. Accessed March 31, 2025. https://www.sanofi.com/en/media-room/press-releases/2025/2025-03-26-06-00-00-3049326

2. CDC. About Chlamydia. Updated January 31, 2025. Accessed March 31, 2025. https://www.cdc.gov/chlamydia/about/index.html

3. Cleveland Clinic. Chlamydia. News release. Updated February 6, 2023. Accessed March 31, 2025. https://my.clevelandclinic.org/health/diseases/4023-chlamydia

4. Phase 1/​2 Study of Chlamydia Trachomatis mRNA Vaccine in Adults Aged 18 to 29 Years. ClinicalTrials.gov. NCT06891417. Updated March 30, 2025. Accessed March 31, 2025. https://clinicaltrials.gov/study/NCT06891417#xd_co_f=MzA3MmU2N2EtMzgxNi00NDcyLTliOGUtYjE1ZDVlZmVlNTc4~