GSK’s antibiotic eliminated the bacterial cause of gonorrhea in 92.6% of patients in a Phase III study, while its Shingrix vaccine’s efficacy in shingles remained above 70% over 11 years of follow up.
GSK’s infectious disease unit reported two clinical trial victories Wednesday, lifting the lid on its Phase III antibiotic victory and sharing long-term data on its blockbuster Shingrix shingles vaccine.
The Phase III antibiotic trial tested gepotidacin in uncomplicated urogenital gonorrhea. The molecule is a first-in-class oral candidate that inhibits bacterial DNA replication using a novel mechanism of action and binding site, suggesting it may be active against strains of gonorrhea and other pathogens that are resistant to existing antibiotics.
GSK reported positive top-line results from the study in February 2024 without sharing any data. The drug developer has now filled in some of the blanks, revealing two oral doses eliminated the bacterial cause of gonorrhea in 92.6% of patients. The success rate was non-inferior to the 91.2% achieved by an existing antibiotic combination of intramuscular ceftriaxone plus oral azithromycin.
The safety and tolerability data were similar to the Phase I and II results, GSK said. Gastrointestinal issues were the most common adverse event in the gepotidacin arm. One patient experienced a severe, Grade III adverse event but it was ruled unrelated to gepotidacin. The other adverse events in the gepotidacin cohort were mild or moderate, according to the company.
GSK ran the study to unlock the market for treating gonorrhea, the rate of which increased by more than 100% in the U.S. from 2009 to 2021, according to the Centers for Disease Control and Prevention. The CDC received reports of almost 650,000 cases in 2022. Around half of U.S. cases are resistant to one antibiotic.
GSK previously reported positive data from a pair of Phase III gepotidacin trials in uncomplicated urinary tract infection. With gepotidacin showing promise in two settings, GSK has identified the drug candidate as one of three anti-infectives that could collectively generate peak annual sales of £2 billion ($2.5 billion). The other anti-infectives are tebipenem HBr and Brexafemme.
The anti-infectives could join a portfolio of products that includes Shingrix, a shingles vaccine that pulled in sales of £3.4 billion ($4.2 billion) last year. GSK is forecasting Shingrix sales of more than £4 billion ($5 billion) this year.
GSK strengthened the case for Shingrix Wednesday. The company posted data from an extension to two Phase III trials, one in adults aged 50 years and over and another in people aged 70 years or older. Between the sixth and eleventh years after vaccination, Shingrix achieved a cumulative efficacy of 79.7% in the over 50s. Cumulative vaccine efficacy in people aged 70 years or older was 73.1%.
“With the vaccine now included in many national immunization programs around the world, these data add to the body of evidence on the extended long-term protection against shingles and provide further confidence to inform public immunization strategies,” Phil Dormitzer, head of vaccines R&D at GSK, said in a statement.
The immunization rate in people aged 50 years and over in the U.S. is 35%. While that leaves room to increase Shingrix sales in the U.S., GSK expects most of the growth in 2024 to come from overseas. The vaccine is approved in almost 40 countries, but penetration is less than 4% in most markets.
Nick Paul Taylor is a freelance pharmaceutical and biotech writer based in London. He can be reached on LinkedIn.
