A Phase I trial conducted at Imperial College London reported positive results for CTH522, a potential chlamydia vaccine.

Results from the trial were published in The Lancet, Infectious Diseases on August 12.

The trial

Conducted by Sonya Abraham, MD, Clinical Senior Lecturer in Rheumatology and General Internal Medicine at Imperial College, the trial consisted of 35 participants. Individuals were randomly assigned (3:3:1) to receive either CTH522 adjuvanted with CAF01 liposomes (CTH522:CAF01), CTH522 adjuvanted with aluminum hydroxide (AH) (CTH522:AH), or placebo.

Both vaccines displayed acceptable safety profile, were immunogenic, and met the trial’s primary and secondary outcomes. GlobalData believes that these positive outcomes hold promise for the vaccine’s future clinical development.

These positive results could also prompt organisations to address other unmet needs in sexually transmitted infections (STIs). These include gonorrhea, trichomoniasis, and syphilis, which accounted for a combined 250 million infections globally in 2016.

The Phase I trial took place between August 15, 2016 and February 13, 2017 at the Imperial Clinical Research Facility at Hammersmith Hospital, London, England. Each healthy participant received injections at Months 0, 1, and 4, followed by two intranasal administrations at Months 4.5 and 5. CTH522:CAF01 had a stronger immunogenicity response than CTH522:AH, showing its potential as a leading chlamydia vaccine candidate.

Following the promising safety data from this Phase I trial, CTH522:CAF01 demonstrated an enhanced mucosal antibody with increased immunoglobulin G (IgG) titers, accelerated seroconversion, and a more consistent cell-mediated immune response. Therefore, GlobalData anticipates further clinical trials to establish the vaccine’s positive efficacy data. However, a larger cohort of patients will be required to validate its statistical and clinical significance.

Theoretically, CHT522 should prove to be successful in reducing the rates of chlamydia. However, for CHT522 to achieve commercial success and have a meaningful impact on public health, GlobalData believes the data must support its long-term impact and overall public health benefits.

An elusive disease

Despite screening programs and antibiotic treatments, chlamydia infections tend to present asymptomatically, which results in a large undiagnosed population. Untreated chlamydia infections can result in several complications, such as pelvic inflammatory disease, endometriosis, and tubal factor infertility. Although spontaneous infections can be cleared with oral antibiotics such as azithromycin, recurrent infections are common and support the need for an efficacious vaccine.