Merck Announces Positive Results on its Late-Stage, Investigational Pneumococcal Vaccine

Today, Merck announced results from across its phase 3 STRIDE studies for its V116 pneumococcal vaccine, which was shown to be immunogenic for all 21 serotypes covered by the vaccine in a variety of adult populations including, those who had not previously received a pneumococcal vaccine (pneumococcal vaccine-naïve); those who had previously received a pneumococcal vaccine (pneumococcal vaccine-experienced); and those with an increased risk of pneumococcal disease, including people living with HIV.

One of the interesting results came from the pneumococcal vaccine-experienced group, explained Heather Platt, MD, clinical director, Merck Research Laboratories, and who leads the product development team for V116.

“We looked at individuals who had gotten a vaccine before, and this is our Stride 6 data in pneumococcal vaccine experienced individuals, and the reason I think this is important is that this represents quite a large population of adults in the US, 60 to 70% of adults have received a pneumococcal vaccine,” said Platt. “So we conducted the study to say, well, if you had a vaccine before, how will you respond to V116? And what we saw in the study is that those individuals were able to mount robust immune responses.”

The data is being presented at the ongoing International Society of Pneumonia and Pneumococcal Diseases (ISPPD) in Cape Town, South Africa. Some of the key findings from the studies include:

• In pneumococcal vaccine-naïve adults 50 years of age and older (STRIDE-3 sub-group), V116 was immunogenic for all 21 serotypes across the studied age groups (50–64, 65–74, and 75–84), as assessed by serotype-specific opsonophagocytic activity (OPA) geometric mean titers (GMTs) at Day 30;
• In pneumococcal vaccine-experienced adults 50 years of age and older (STRIDE-6), V116 elicited comparable immune responses for the serotypes shared with PCV15 (pneumococcal 15-valent conjugate vaccine) or PPSV23 (pneumococcal vaccine, polyvalent [23-valent]) and higher immune responses for the serotypes covered by V116 only, regardless of the previous pneumococcal vaccine received or time since prior pneumococcal vaccination, as assessed by serotype-specific OPA GMTs at Day 30;
• In adults 18 years of age and older living with HIV (STRIDE-7), V116 elicited comparable immune responses to PCV15+PPSV23 for all 13 shared serotypes and higher immune responses for the eight serotypes covered by V116 only, as assessed by serotype-specific OPA GMTs and Immunoglobulin G (IgG) geometric mean concentrations (GMCs) at Day 30;
• Across all presented studies, V116 demonstrated a safety profile comparable to the studied comparators, including PCV20 (pneumococcal 20-valent conjugate vaccine), PCV15 and PPSV23.

Novel and Long-Term Protection?
As many adults have been previously vaccinated for pneumococcal disease, Merck performed a sub study, where they looked at the time since last vaccination. “If they got the vaccine, 1 to 4 years, 5 to 9 years or even 10 years before, they still had robust immune responses to be 116,” Platt stated. “V116 has 8 unique serotypes that are not in any currently licensed vaccine. And this accounts for about 30% of disease in adults. So we wanted to provide data to say, ‘if you had a vaccine before, you could have this incremental benefit.’ And we want to make sure that those patients are represented.”

One of the areas Merck is looking at is the potential for long-term protection from disease and although they have not determined that yet, they do expect to understand it better in future studies.

“It's a T-cell dependent vaccine, which means it stimulates B cells, and we develop memory. So, the next time we see strep pneumonia, we already have the antibodies ready to respond,” Platt stated.

“The B cells stimulating memory means that those antibodies will persist far longer, and they'll actually be functional. And that's what we look at…to evaluate how is the vaccine going to perform over time. In our clinical studies, we look at the immune responses, we look at functional activity, and it's really do the antibodies kill the bacteria in vitro?”

Next Steps
In approximately 3 months (June 17), Merck has its Prescription Drug User Fee Act (PDUFA) target action date for V116. If the vaccine is approved, Platt explained there were a few patient populations who may potentially benefit from the vaccine.

“I would expect that there will be value in this vaccine for individuals just based on age alone—that are 50 years of age and older,” Platt explained. And I also expect there will be value in protecting patients with risk factors, no matter their age. Of course, the advisory committee, the ACIP, will make their recommendation, but our belief is that [it will] prevent disease and benefit public health. We're generating the data and we see the value in vaccinating patients based on their risk profile.”

Reference
Merck Announces Positive Data on V116, an Investigational, 21-Valent Pneumococcal Conjugate Vaccine Specifically Designed for Adults, Demonstrated Immune Responses in Adults. Merck press release. March 19, 2024. Accessed March 19, 2024.

https://www.merck.com/news/merck-announces-positive-data-on-v116-an-investigational-21-valent-pneumococcal-conjugate-vaccine-specifically-designed-for-adults-demonstrated-immune-responses-in-adults/