Merck’s Prevnar challenger nabs FDA ‘breakthrough’ tag. Should Pfizer be worried?

pneumococcal virus microscope image
Merck's vaccine candidate targeting 15 strains of the pneumococcal virus just got FDA VIP treatment on its way to challenge Pfizer's Prevnar 13. (Josef Reischig/CC BY-SA 3.0)

Merck & Co.’s endeavor to challenge Prevnar 13, the world’s best-selling vaccine, just got a speed-up. But it doesn’t appear to have too much of a lead over rival Pfizer.

The New Jersey pharma said Wednesday its 15-strain pneumococcal vaccine candidate, V114, has nabbed an FDA “breakthrough” designation in pediatric patients. With that, it will enjoy an expedited review process with closer communications with the FDA. And if everything goes well, the vaccine could win accelerated approval and priority review tags, too, speeding things up even further.

The FDA’s decision was based on data from two studies, Merck said. In both studies, V114 induced an immune response in infants for the two serotypes of S. pneumoniae not targeted by Pfizer’s Prevnar 13 and showed a similar effect in the other 13 serotypes, the company said.

V114’s “breakthrough” tag came about half a year after Pfizer earned the same designation—but in adults—for its 20-valent pneumococcal vaccine candidate, PF-06482077. The two vaccines are in a tight race to be the next big thing in vaccines, with V114 slightly ahead in phase 3.

Prevnar 13 has been hogging that title for some time. In 2018, it grew sales by 4% to reach $5.80 billion, thanks to rollouts in emerging markets. But with the market growing saturated, sales growth has slowed, and Pfizer predicts 2019 sales will be flat year over year. The U.S. adult market may see some decline due a shrinking pool of patients not yet vaccinated, Credit Suisse analyst Vamil Divan wrote in a Tuesday note to clients, referring to a Q&A with Pfizer’s investor relations team.

RELATED: Racing with Merck, Pfizer wins FDA 'breakthrough' tag for 20-valent pneumococcal vaccine

The company did warn of a potential risk at the upcoming CDC’s Advisory Committee on Immunization Practices (ACIP) meeting on Feb. 28, where experts might remove a recommendation for Prevnar in adults or limit it to high-risk adults only. Currently, the CDC recommends the pneumococcal vaccine for all children younger than 2 years of age and for all adults 65 years or older.

Judging by the Credit Suisse report, the Pfizer team seemed unfazed by Merck's potential challenger. Merck started phase 3 testing on V114 mid-2018, and one of the two studies is a head-to-head trial against the Pfizer shot. PF-06482077 entered phase 3 a bit later—at the end of 2018. While the two additional serotypes included in the Merck shot are implicated in about 15% of pneumococcal cases, Pfizer’s 20-valent candidate can cover 15% beyond that, Pfizer told Divan.