Adult data back Merck & Co's challenger to Pfizer’s blockbuster Prevnar 13

Merck & Co has built more momentum behind its attempt to depose Pfizer’s blockbuster pneumococcal conjugate vaccine Prevnar 13, with two new phase 3 trials backing its rival shot V114.

The two trials are both in adult subjects, a group that has been driving growth of Prevnar 13 in the last few years, and showed that V114 stimulated immune responses to all 15 pneumococcal serotypes included in the vaccine.

In the PNEU-PATH and PNEU-DAY studies, dosing with V114 was followed a year later by a shot of Merck’s older polysaccharide-based Pneumovax 23 vaccine, and showed that the combination was protective in the over-50 and under-50 adult age groups, respectively.

US-based Merck already has phase 3 data in hand backing the safety and efficacy of V114 in children as well as non-inferiority to Prevnar 13 for the serotypes the two vaccines share. It reiterated its plans to file for approval of the vaccine before the end of the year in the US.

Prevnar 13 – which as its name suggests covers 13 serotypes – is the world’s top-selling vaccine, adding almost $6 billion to Pfizer’s top-line last year thanks to its dominant position in the paediatric pneumococcal shot market.

Added to that, it’s not due to lose patent protection until 2026, when analysts predict it could make more than $7 billion, although it’s worth noting that growth has been pegged back so far in 2020 as a result of the pandemic lockdowns.

Merck is hoping to trump its rival with 15-valent V114, as it provides protection against two serotypes – 22F and 33F – that aren’t included in Pfizer’s product. It also provides an opportunity to expand its position in the adult pneumococcal disease market, where Pneumovax 23 is still widely used.

“Pneumococcal disease in adults is on the rise globally, in part driven by disease-causing serotypes not targeted by the currently available pneumococcal conjugate vaccine,” said Merck’s chief medical officer Roy Baynes.

“These data provide important information about the potential for V114 followed by Pneumovax 23 [which is] included in more than 90% of age-based adult pneumococcal immunization programmes globally,” he added.

Pfizer isn’t resting on its laurels however, and is preparing to defend its Prevnar franchise, reporting positive clinical results with a 20-serotype follow-up – called PF-06482077 or 20vPnC – that it also thinks could be ready for filing before the end of the year.

As a backup it has also been developing a 7-serotype shot that would provide the same breadth of cover as 20vPnC when combined with Prevnar 13.

Pneumococcal disease is caused by Streptococcus pneumoniae, and includes non-invasive illnesses like pneumonia, sinusitis and middle ear infections, as well as invasive diseases like meningitis.

It can be particularly problematic in young children under two and adults aged over 65, as well as people with compromised immune systems.