Merck's rival to Pfizer's Prevnar 13 hits goal in phase 3 again

Merck is working to file for FDA approval of its V114 vaccine by the end of the year. (Merck)

Two more phase 3 trials of Merck’s challenger to Pfizer’s Prevnar 13 have met their immunogenicity endpoints. The results suggest the V114 vaccine provides broader protection from pneumococcal bacteria than Prevnar 13 does, positioning Merck to muscle in on Pfizer’s turf. 

Prevnar 13  generated sales of $5.8 billion for Pfizer last year. The size of the market has attracted the attention of Merck, which is running a broad clinical development program to show V114 is a better choice than Prevnar 13. V114 is designed to provide protection against the 13 serotypes covered by Prevnar 13, plus two other serotypes.

The latest evidence that V114 matches Prevnar 13 against the 13 shared serotypes, with the bonus of protecting against two other serotypes, comes from two phase 3 trials. One of the studies enrolled healthy adults aged 50 years and older and randomized them to receive V114 or Prevnar 13.

Investigators assessed the 652 participants 30 days after receiving the vaccines. Opsonophagocytic activity responses showed immune responses for the 13 shared serotypes were comparable in the V114 and Prevnar 13 arms. Immune responses for the two serotypes unique to V114, 22F and 33F were higher among subjects who received Merck’s investigational vaccine.

Participants went on to receive a shot of Merck’s Pneumovax 23 one year after being vaccinated with V114 or Prevnar 13. The design mirrors the Centers for Disease Control and Prevention’s schedule for the vaccination of people aged 65 years and older, which suggests patients consider receiving a dose of Prevnar 13 followed by a shot of Pneumovax 23 at least one year later.

Merck found the immune responses in people after the Pneumovax 23 dose were similar regardless of whether the subjects previously received V114 or Prevnar 13. The data give Merck the chance to pitch V114 and Pneumovax 23 as a package to the 90% of age-based adult pneumococcal immunization programs that include the latter vaccine.

The second phase 3 trial to read out Tuesday gave V114 or Prevnar 13 to immunocompetent 18- to 49-year-olds with underlying health conditions that put them at greater risk of pneumococcal disease. V114 outperformed Prevnar 13 in terms of immune responses to its two unique serotypes and was “generally comparable” to Pfizer’s vaccine against the 13 shared serotypes. 

The data follow positive updates from other phase 3 trials of V114 in June and September. Merck is working to file for FDA approval on the strength of the data by the end of the year. In parallel, work is continuing to show V114 can match or outperform Prevnar 13 in other populations, notably children.

Pfizer is working on its own successor to Prevnar 13. In March, Pfizer said the 20-valent vaccine, code-named 20vPnC, was noninferior to Prevnar 13 against their 13 shared serotypes. 20vPnC also matched the immune response of Pneumovax 23 against six of the seven additional serotypes shared by those two vaccines. Pfizer is working to file for approval by the end of the year.