New data suggest GSK's RSV vaccine Arexvy may protect more at-risk adults

A single dose of the Arexvy vaccine has been found to elicit a strong immune response with an acceptable safety profile in adults aged 18-49 who are at increased risk for RSV-LRTD. Additionally, two doses of the vaccine in immunocompromised adults aged 18 and above produced immune responses similar to those observed after one dose in healthy adults aged 50 and above, also maintaining a favorable safety profile. In the United States alone, there are potentially over 21 million adults aged 18-49 with at least one risk factor for RSV disease.

GSK plc recently announced this new preliminary data for Arexvy, a respiratory syncytial virus (RSV) vaccine, in a study involving adults aged 18-49 who are at increased risk for RSV-LRTD due to underlying medical conditions, as well as in immunocompromised adults. The data suggest that the vaccine could broaden protection to more adults at risk of RSV, a virus that can cause severe respiratory illness. Currently, the vaccine is approved for adults aged 60 and older in over 50 countries, and for adults aged 50-59 at increased risk in several countries, including the US and Europe. However, there are no RSV vaccines recommended for adults younger than 60 who are at increased risk, despite the disease burden in this population.

Tony Wood, GSK's Chief Scientific Officer, emphasized that these findings support the potential of GSK’s RSV vaccine to expand protection to more at-risk adults. He highlighted the insights into the impact of a second dose for certain populations, underscoring GSK's commitment to collaborating with health authorities and regulators to benefit adults at increased risk of RSV disease through vaccination.

In the phase IIIb trial, a single dose of the vaccine generated robust immune responses in adults aged 18-49 with underlying medical conditions leading to increased risk for RSV-LRTD. The immune response in this group was non-inferior to that observed in adults aged 60 and above, meeting the trial's co-primary endpoints. Meanwhile, the phase IIb trial demonstrated that a single dose of the vaccine elicited a strong immune response in immunocompromised adults aged 18 and above, with a second dose producing responses comparable to those of healthy adults aged 50 and older who received one dose. These consistent immune responses were observed for both RSV-A and RSV-B subtypes.

Safety and reactogenicity data from both studies aligned with previous phase III results that supported the vaccine's initial approval. The most common local adverse event was pain, while common systemic adverse events included fatigue, myalgia, arthralgia, and headache, most of which were transient and mild.

RSV is a widespread, contagious virus that can cause severe respiratory illness, impacting an estimated 64 million people globally each year. Individuals who are immunocompromised or have certain underlying medical conditions, such as chronic obstructive pulmonary disease (COPD), asthma, heart failure, and diabetes, are at higher risk for severe consequences from RSV infection compared to those without these conditions, including an increased risk of mortality.

The final results from these trials will be presented at upcoming medical conferences and submitted for peer-reviewed publication. Additionally, the final data will be submitted to the US Food and Drug Administration (FDA) and other regulators to support potential updates to the vaccine's label.

The phase IIIb open-label study (NCT06389487) aimed to evaluate the non-inferiority of the immune response and the safety of GSK’s RSV vaccine in adults aged 18-49 at increased risk for RSV disease compared to adults aged 60 and older. The study enrolled 1,457 participants across 52 locations in six countries, and it is ongoing, with further safety and immunogenicity data expected to be collected up to six months post-vaccination, concluding in 2025.

The phase IIb trial (NCT05921903) is a randomized, controlled, open-label, multi-country study evaluating the immune response and safety of the RSV vaccine in immunocompromised adults due to lung and renal transplants, comparing one versus two doses. It enrolled 386 participants across 48 locations in eight countries, and it aims to collect safety and immunogenicity data up to 12 months post the last dose, concluding in 2025.

GSK’s RSV vaccine contains recombinant RSV glycoprotein F stabilized in the prefusion conformation and is combined with GSK’s proprietary AS01E adjuvant. The vaccine is approved for the prevention of RSV-LRTD in individuals 60 years and older in more than 50 countries, including Europe, Japan, and the US. It is also approved in the US and EU/EEA countries for use in individuals aged 50-59 at increased risk due to underlying medical conditions, with regulatory reviews ongoing in other countries.