Pfizer takes 25-valent Prevnar follow-up into phase 3

Pfizer has upped the ante in the increasingly competitive market for pneumococcal vaccines with mid-stage clinical data for a new shot covering 25 strains – five more than its current Prevnar 20 product.

The phase 2 trial of the new vaccine – known as PF-07872412 or 25vPnC – revealed stronger immune responses to the serotypes covered by Prevnar 20 when given as a four-shot course to healthy infants, as well as providing protection against the additional five.

It also achieved a significantly "enhanced response" against serotype 3 – a highly virulent and invasive strain of Streptococcus pneumoniae linked to pneumonia, bacteraemia, and meningitis – according to data presented from the study at the International Society of Pneumonia & Pneumococcal Diseases (ISPPD) congress in Copenhagen, Denmark.

A month after the third dose, antibody titres for serotype 3 were 8.8-fold higher with 25vPnC than with Prevnar 20, and came in 15-fold higher a month after dose four.

"This vaccine candidate is expected to cover up to 90% of disease-causing serotypes in children under five years of age, which includes approximately 15% from serotype 3," said Pfizer in a statement.

Along with Prevnar 20, the company still sells a 13-valent version of the pneumococcal vaccine (Prevnar 13), and the two products lead the pneumococcal vaccine market with sales of nearly $6.5 billion last year.

It is the latest development in an ongoing game of one-upmanship with rival vaccine developers like MSD, Sanofi, and Vaxcyte. MSD already sells a 21-valent pneumococcal vaccine, Capvaxive, while Sanofi is running late-stage trials of a 21-valent candidate (PCV21) licensed from SK Bio, and Vaxcyte is developing a 31-valent jab (VAX-31) in phase 2.

Capvaxive has made rapid inroads into the market, recording $759 million in global sales last year, while MSD's older 15-valent vaccine Vaxneuvance brought in another $825 million, but the franchise is still a long way behind Pfizer.

"These phase 2 results reinforce our confidence in a next-generation vaccine designed to expand protection across serotypes while improving responses to key residual disease drivers such as serotype 3," said Annaliesa Anderson, Pfizer's chief vaccines officer.

"We are advancing our phase 3 programme with the goal of delivering broader and more durable protection for children," she added.

A late-stage paediatric trial of 25vPnC started earlier this month, and Pfizer is also working on a 35-valent candidate for the adult pneumococcal vaccination market that is due to start clinical development by the end of this year.