Sanofi is making significant strides in the fight against chlamydia, the most common sexually transmitted bacterial infection, for which there are currently no approved preventative vaccines. The French pharmaceutical group has recently been granted a fast-track designation from the U.S. Food and Drug Administration (FDA) for its preclinical-stage mRNA-based vaccine candidate. This promising candidate is poised to enter a Phase 1/2 clinical trial in the coming days, positioning it as one of only a handful of chlamydia vaccines ready for human testing globally.
Chlamydia, caused by the bacterium Chlamydia trachomatis, remains a major public health concern worldwide. The World Health Organization (WHO) estimated approximately 128.5 million new chlamydia infections occurred in 2020, with a global prevalence of 4% among women and 2.5% among men. While the infection is typically easily treated with antibiotics and often does not lead to long-term issues if addressed promptly, a significant challenge lies in its often asymptomatic nature. This lack of noticeable symptoms can delay or prevent timely treatment, potentially contributing to severe complications such as pelvic inflammatory disease (PID) in women, which can lead to pregnancy complications or infertility. Furthermore, chlamydia infection has been shown to dramatically increase an individual’s risk of contracting other sexually transmitted infections, including HIV.
Recognizing the substantial public health burden and the lack of preventative measures, the FDA’s decision to grant Fast Track designation underscores the urgency and potential significance of Sanofi’s vaccine candidate, contingent upon demonstrating safety and efficacy in subsequent clinical trials. The drugmaker has stated that its vaccine is specifically designed to provide protection against both primary genital tract infection and reinfection by C. trachomatis. The planned Phase 1/2 clinical trial is expected to last 18 months, with an estimated completion date in 2028. According to its listing on the clinicaltrials.gov register, the study aims to enroll approximately 1,560 individuals between the ages of 18 and 29 years.
The trial will include both chlamydia seropositive and seronegative men and women who report having a new sexual partner within the last six months, more than one current sexual partner, a partner with a prior or current STI, or inconsistent condom use. Participants will receive three doses of the mRNA vaccine via intramuscular injection at varying low, medium, and high dose levels, or a matched placebo for comparison.
Jean-François Toussaint, Sanofi’s global head of vaccines R&D, emphasized the critical need for a preventative approach, stating, “Millions of people currently live with undiagnosed chlamydia, including asymptomatic infection that can also cause severe long-term health effects if left untreated.” He further noted the limitations of current treatments, adding, “Antibiotics to treat chlamydia have not been successful in controlling rising infection rates. With our programme, we aim to make chlamydia a preventable disease through vaccination.”
Sanofi’s efforts are part of a broader push to develop a chlamydia vaccine. Another notable candidate in development is CTH522 from Denmark’s Statens Serum Institut (SSI). This vaccine utilizes a conventional recombinant approach based on a bacterial membrane protein and has demonstrated safety and immunogenicity in early-stage trials with healthy volunteers. SSI is currently preparing for further studies to evaluate its ability to prevent chlamydia infections.
https://pharmaphorum.com/news/fda-fast-tracks-sanofis-experimental-chlamydia-vaccine
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