Sexual & Reproductive Health

Sexually transmitted infections (STIs)

11,473,757
DALYs in 2017
119,093
Deaths in 2017

Sexually transmitted infections (STIs) are a major global health issue. Although primary infection can be asymptomatic or cause manageable symptoms, it can also produce acute illness, and result in serious conditions including increased HIV acquisition and transmission; pelvic inflammatory disease, ectopic pregnancy and infertility; and congenital deformities, stillbirth, neonatal illness and death.

In 2016, there were 376 million new cases of the four most common curable STIs: 156 million cases of trichomoniasis, 127 million of chlamydia, 87 million of gonorrhoea, and 6.3 million of syphilis – equating to transmission of more than 1 million STIs per day. Up to 10 million people worldwide are also infected with HTLV-1, arguably the most potent oncovirus, while more than 400 million people live with incurable HSV-2. The burden of STI infections is greatest in LMICs.

R&D needs

Antimicrobial resistance (AMR) poses a major threat to effective treatment of STIs, with increasing emergence of resistant strains no longer susceptible to existing antibiotics. However, the novel drug pipeline is largely empty or immature. Gonorrhoea is the only STI with drug candidates in late-stage trials. Preventive and therapeutic vaccines are therefore also urgently required. Currently however, there are no approved vaccines for syphilis, gonorrhoea, HTLV-1, HSV-2 or chlamydia. Development of vaccines to clear or prevent infection with HSV-2 is advancing despite setbacks, while several novel preclinical candidates are being evaluated for syphilis. Clinical research into the cross-protective potential of meningitis vaccines for gonorrhoea is also ongoing, alongside recruitment for Phase I trials of an entirely new gonorrhoea vaccine from GSK. Diagnostics to identify AMR and guide treatment are also needed. Diagnosis still relies on costly laboratory testing: low-cost rapid point-of-care tests are needed for all STIs except for syphilis. There is also a need for tests that can simultaneously diagnose co-existing STIs.

Pipeline spotlight

The novel antibiotic zoliflodacin for gonorrhoea, is in Phase III clinical development through a partnership between GARDP and Entasis Therapeutics (now a subsidiary of Innoviva), with topline results expected end of 2023. A second novel antibiotic, GSK’s gepotidacin, is also in Phase III trials expected to conclude in October 2023.