- GlaxoSmithKline will pause enrollment and dosing in trials of an experimental respiratory disease vaccine in pregnant women, reporting Friday that independent monitors had recommended doing so "based on an observation from a routine safety assessment."
- A trial of a related vaccine for the pathogen, called respiratory syncytial virus, in adults age 60 or older is not affected by the pause, the company said. Phase 3 results from that trial are due sometime before June 30.
- GSK is in a race with Pfizer and Sanofi to launch the first vaccines for RSV, a common pathogen that results in more than 100,000 hospitalizations a year in the U.S. Analysts forecast the market could be worth more than $7 billion by the late 2020s.
GSK didn't detail the safety observation identified by the data monitoring committee of the GRACE trial in pregnant women and infants of vaccinated women, and said it will provide an update "in due course." The GRACE trial was set to enroll 20,000 pregnant women and assess the prevention of respiratory tract infection in their babies up to six months after birth. Data wasn't expected until 2023.
The safety observation led GSK to halt two other maternal RSV vaccine trials, one of which hasn't begun enrolling volunteers. The other has been recruiting volunteers and was set to enroll about 750.
A common infection, RSV was first targeted for preventive vaccines back in the 1960s. Those failed due to safety problems caused by the shots stimulating antibodies that weren't protective as well as a type of immune response that can make disease worse.
The recent progress in developing an RSV vaccine, meanwhile, is the result of scientists better understanding how to target the virus' F protein, which antibodies stimulated by the vaccine bind as they work to shut down infections.
GSK said the pause doesn't impact its RSV vaccine for adults age 60 and older, which is in a Phase 3 trial due to enroll 25,000 people. That shot contains a chemical called an adjuvant that adds an additional stimulus to the immune system.
Pfizer and Johnson & Johnson have also begun Phase 3 trials of their respective shots in older adults, while Sanofi is testing a vaccine in young children. Unlike GSK, Sanofi is vaccinating children directly rather than trying to confer protection through maternal antibodies.
Moderna, meanwhile, has begun work on an mRNA vaccine in adults of all ages and children.