Pfizer jumps on the scene in RSV, pushing vaccine candidate into human testing

Pfizer is counting on several mid- and late-stage vaccine candidates to carry the torch after its megablockbuster pneumococcal shot Prevnar 13, the world's bestselling vaccine, slows down. But it's stocking its early pipeline, too.

The drugmaker started human testing Tuesday with another prospect in a market with blockbuster potential: an early-stage vaccine against RSV, a respiratory virus that kills an estimated 120,000 children worldwide every year. Another 177,000 older adults are hospitalized annually because of the infection in the U.S. alone.

The phase 1/2 placebo-controlled trial will test the shot in two groups: adults 18 to 49 and adults 50 to 85 years old. The vaccine is designed for older adults and for mothers, who'd be injected to protect their infants. Pregnant women will not be included in this early-phase testing.

Primary endpoints are safety and tolerability, with immunogenicity as a secondary endpoint. According to, investigators aim to enroll about 1,200 participants and complete the study in late 2019.

The candidate incorporates work from the National Institutes of Health, according to Pfizer's press release, and the drugmaker says it developed several versions that elicited "strong and stable" immune responses in preclinical tests. The new trial will test up to six formulations, either alone or alongside a seasonal inactivated flu shot.

RELATED: Where is Pfizer putting its R&D hopes? Vaccines are front and center 

The need is great—so great, the World Health Organization has said an RSV vaccine is a global health priority. There are about 33 million RSV cases in children under 5 every year worldwide, a Gates Foundation-funded study found. In addition to the 120,000 children who die of RSV each year, 3 million children are hospitalized, the study found. 

There is no approved RSV vaccine, though other companies are working on their own candidates. Novavax has a late-stage shot in testing, with help from an $89 million grant from the Bill & Melinda Gates Foundation. 

At Pfizer, the work comes as sales for its megablockbuster pneumococcal shot Prevnar 13 are flattening out after a tremendous early success. In 2017, sales for the franchise slipped 2% to $5.6 billion; executives have said the company expects Prevnar sales to be flat this year.

Meanwhile, Pfizer is developing a series of late-stage vaccines against healthcare-associated infections C. diff and S. aureus that Bernstein analyst Tim Anderson recently wrote would "represent new, unprecedented opportunities" if successful. Aside from those programs, Pfizer is advancing a next-generation 20-valent pneumococcal shot. In a conversation with Anderson, Pfizer R&D head Mikael Dolsten said he believes the vaccine "will position the company well for the next decade." 

Other early-stage vaccine programs in Pfizer's pipeline are a maternal Group B streptococcus shot, a prostate cancer vaccine and a MenABCWY vaccine.

RELATED: Novavax details 'pre-commercialization activities,' $1.5B sales target for RSV vaccine 

Elsewhere in RSV, Novavax executives recently outlined "pre-commercialization activities" underway at the biotech, even though a potential launch is still a couple years out. On a recent conference call, executives said their vaccine would be given in the third trimester of pregnancy, and the company is working with American College of Obstetricians and Gynecologists on educational programs for physicians. They expect a market size of $1.5 billion or more.

GlaxoSmithKline, Johnson & Johnson's Janssen, AstraZeneca's MedImmune and Bavarian Nordic are among other companies working on RSV immunizations. GSK and MedImmune are in phase 2, while Janssen, Vaxart and others are in phase 1, according to a vaccine industry report from PhRMA. Novavax previously suffered a late-stage trial flop of its shot in older adults, devastating its share price.