Merck's challenge to Pfizer's Prevnar grows

Pfizer's longstanding dominance of the pneumococcal vaccines category could be threatened by Merck & Co, which has just reported new data on its V116 shot in older adults that could lead to regulatory filings.

V116 is a cocktail of 21 Streptococcus pneumoniae serotypes designed to have the most benefit in adult populations, and according to Merck has been shown to generate protective immune responses in both vaccine-naïve and vaccine-experienced adults aged 65 and over.

In one phase 3 trial involving patients not previously vaccinated with a pneumococcal jab – called STRIDE-3 – V116 showed "statistically significant immune responses" compared to Pfizer's Prevnar 20, the latest member of its Prevnar family, which leads the market with sales of $6.3 billion last year.

A second study, STRIDE-6, showed that V116 stimulated antibodies against all 21 S. pneumoniae strains in adults who had previously received a pneumococcal vaccine at least one year prior to the study. Both studies also backed up the safety and tolerability of the shot, which Merck said was "comparable" to the comparator product.

The company plans to file for approval of the new vaccine on the strength of the data and, if approved, it will slot into its portfolio alongside Vaxneuvance (formerly V114), which covers 15 serotypes and was approved by the FDA in 2021.

Merck also sells an older shot called Pneumovax 23, which covers 23 serotypes, but is based on an older polysaccharide technology that does not stimulate the immune response as strongly as the newer conjugate vaccines.

In a statement, the drugmaker said it would be "the first pneumococcal conjugate vaccine specifically designed for adults," and covers serotypes responsible for 85% of invasive pneumococcal disease in individuals 65 and older.

Merck is taking a targeted approach with its vaccines, zeroing in on serotypes that cause problems in specific patient populations, and notes that V116 includes eight serotypes not currently covered by approved pneumococcal vaccines.

That's a little different from Pfizer, which has gone for broad-spectrum coverage of the most prevalent serotypes. For now, however, the Prevnar brand remains largely unscathed from Merck's challenge.

Vaxneuvance was launched after Pfizer introduced Prevnar 20, but debuted with FDA approval for paediatric use that wasn't forthcoming for Pfizer's 20-valent shot until earlier this year, setting it into contention against the older Prevnar 13 product.

Sales remain fairly modest at just over $100 million in the first quarter of this year, and some analysts believe V116 could be key to Merck's segmented strategy hover, along with V117, an earlier-stage project that will deploy its serotype selection approach to a paediatric vaccine.

"Despite the availability of current pneumococcal conjugate vaccines, many adults remain vulnerable to pneumococcal disease, especially those who are older," said Dr Eliav Barr, head of global clinical development and chief medical officer at Merck Research Laboratories.

"These results support the potential for V116 to become an important new preventative option for adults, regardless of prior pneumococcal vaccination status, by expanding coverage to include eight serotypes not currently included in any licensed vaccine," he added.