Pfizer Reports Positive Phase 3 Results for RSV Vaccine in Immunocompromised Adults

Pfizer announced encouraging top-line results from substudy B of its pivotal Phase 3 MONeT trial, demonstrating that the respiratory syncytial virus (RSV) vaccine Abrysvo is both well-tolerated and effective in generating strong neutralizing responses in immunocompromised adults aged 18 and older.¹

The RSV vaccine showed strong immunogenicity and safety in immunocompromised adults, study finds. | Image credit: jetcityimage - stock.adobe.com

“Immunocompromised adults, such as patients with cancer or autoimmune disorders, have a substantially increased risk of experiencing severe complications from RSV, yet there are currently no vaccines approved for those aged 18 to 59 in the US,” said Annaliesa Anderson, PhD, senior vice president and chief scientific officer of Vaccine Research and Development, Pfizer, in a statement. “We are encouraged by the positive top-line data from this study, which provide important evidence that Abrysvo has the potential to address a significant unmet need in this vulnerable population.”

RSV is a common respiratory virus that usually causes symptoms resembling a cold.² Currently, the CDC recommends an RSV vaccine for everyone aged 75 and older and for adults aged 60 to 74 who are at increased risk of severe RSV.

The study (NCT05842967) included individuals with conditions such as non-small cell lung cancer (NSCLC), end-stage renal disease, autoimmune disorders, and solid organ transplants.¹ Approximately 203 immunocompromised adults were enrolled in the study, of which approximately half were aged 18 to 59, and the other half were aged 60 years and older.

Participants received 2 doses of the vaccine, administered 1 month apart. The primary end point was to assess the safety of the vaccine, including any adverse events or reactions. The secondary end point was to evaluate the immunogenicity of the vaccine, specifically measuring the neutralizing antibody response against both RSV-A and RSV-B subtypes.

Safety data were collected throughout the trial, while immunogenicity was assessed by measuring levels of neutralizing antibodies in blood samples taken before and after vaccination.

The vaccine demonstrated a consistent safety profile, with no unexpected adverse effects reported across the diverse participant groups, including those with NSCLC, individuals on hemodialysis due to end-stage renal disease, those with autoimmune inflammatory disorders receiving active immunomodulator therapy, and solid organ transplant recipients.

While the study evaluated doses of the vaccine, the findings indicated that a single dose was sufficient to elicit a strong neutralizing response against both RSV-A and RSV-B subtypes, exhibiting robust immune protection.

Furthermore, Pfizer plans to present these results at an upcoming scientific conference and to submit the data for review by regulatory agencies, which could lead to the approval and availability of the vaccine for immunocompromised adults. Pfizer has also initiated a clinical trial evaluating the vaccine in children aged 2 to 18 years who are at increased risk for RSV.

“Many health care providers and pharmacies prefer the simplicity of having 1 vaccine for both adult vaccinations and maternal vaccination, which only Abrysvo can offer,” Pfizer’s chief US commercial officer, Aamir Malik, said on a call to Fierce Pharma.³ As for the limited Advisory Committee on Immunization Practices (ACIP) policy, Malik said the guidance offers clarity and “strengthens the directive for those who are eligible for a vaccine.”

According to the statement, these results contribute to the growing body of evidence supporting the vaccine as an effective and safe option for preventing RSV-related illnesses in high-risk populations, including those with compromised immune systems.¹

References

1. Pfizer announces top-line results of Abrysvo for RSV in immunocompromised adults. News release. Pfizer. Published August 2, 2024. Accessed August 15, 2024. https://www.businesswire.com/news/home/20240812622927/en/Pfizer-Announces-Top-Line-Results-of-ABRYSVO%C2%AE-for-RSV-in-Immunocompromised-Adults

2. RSV (respiratory syncytial virus) immunizations. CDC. Published July 3, 2024. Accessed August 15, 2024. https://www.cdc.gov/vaccines/vpd/rsv/index.html

3. Pfizer, looking to expand RSV vaccine's reach, touts its benefits in immunocompromised adults. Fierce Pharma. Published August 12, 2024. Accessed August 15, 2024. https://www.fiercepharma.com/pharma/pfizer-looks-expand-abryxvos-reach-rsv-vaccine-shows-benefit-immunocompromised-adults