Bilex Pharma today announced the successful completion of patient enrollment in the pivotal Phase 3 clinical trial (RSV-301) evaluating the efficacy, safety, and immunogenicity of BLX-RSV01, its investigational vaccine candidate designed to protect older adults (aged 60 years and above) against Respiratory Syncytial Virus (RSV).
Achieving a Critical Milestone in Late-Stage Development
Reaching full enrollment is a major operational milestone for the BLX-RSV01 program and marks a critical step towards potentially bringing a much-needed vaccine to this vulnerable population. The global trial successfully enrolled over 10,500 participants across more than 150 clinical sites in 7 countries, including the UK, US, Australia, and several European nations.
RSV poses a significant health burden to older adults, often leading to severe respiratory illness, hospitalization, exacerbation of underlying conditions, and mortality. Despite this, vaccine options have historically been limited, highlighting a substantial unmet medical need.
Positioned for Efficacy Readout
With enrollment now complete, the trial will continue to follow participants through the upcoming RSV seasons to assess the vaccine’s ability to prevent RSV-associated lower respiratory tract disease (LRTD), the study’s primary endpoint. Data collection on safety and immunogenicity endpoints will also continue according to the study protocol.
“Completing enrollment in our pivotal Phase 3 RSV trial is a tremendous achievement and brings us one significant step closer to potentially delivering an effective vaccine against RSV for older adults,” said Dr. Andras Ottlik, CEO of Bilex Pharma. “I want to extend my sincere gratitude to the trial participants, clinical investigators, site staff, and the dedicated Bilex Pharma team whose collective efforts made reaching this milestone possible.”
Dr. Sophia Chen, Chief Medical Officer at Bilex Pharma, added: “Successfully enrolling over 10,500 participants globally underscores the high level of interest in and need for an effective RSV vaccine. Our focus now shifts entirely to meticulous participant follow-up and ensuring the highest quality data collection as we await the accumulation of sufficient RSV cases to conduct the primary efficacy analysis.”
Building on Promising Science
BLX-RSV01 leverages Bilex Pharma’s advanced vaccine technology, featuring a proprietary stabilized pre-fusion F protein antigen (StructVax™ platform) designed to elicit potent neutralizing antibodies, combined with the company’s AdaVant™ adjuvant system tailored to enhance immune responses in older populations. Previous Phase 2 results demonstrated strong immunogenicity and a favourable safety profile, providing a solid foundation for the ongoing Phase 3 evaluation.
A Key Component of Project SHIELD
The BLX-RSV01 program is a flagship component of Bilex Pharma’s Project SHIELD, a strategic initiative focused on developing comprehensive protection against major respiratory viral threats, including RSV, influenza, and coronaviruses.
Next Steps
The primary efficacy analysis will be conducted once a pre-specified number of RSV-LRTD cases have accrued among trial participants. Bilex Pharma anticipates that, based on projected RSV circulation, this analysis could potentially occur later in 2025 or early 2026. Following positive efficacy results, the company plans to proceed with regulatory submissions in major markets.
Bilex Pharma remains committed to rigorously evaluating BLX-RSV01 and, if successful, working to make this potentially vital vaccine available to help protect older adults worldwide from the serious consequences of RSV infection.
About Bilex Pharma
Bilex Pharma is a UK-based biotechnology company dedicated to advancing human health through groundbreaking research and innovative vaccine development. Our mission is to protect communities worldwide by combating infectious diseases and emerging health threats with safe, effective, and accessible vaccines, leveraging cutting-edge platforms including mRNA, viral vectors, and advanced adjuvant systems.
About Respiratory Syncytial Virus (RSV)
RSV is a common respiratory virus that usually causes mild, cold-like symptoms but can be serious, especially for infants and older adults. Among older adults, RSV infection can lead to significant morbidity and mortality due to complications such as pneumonia, exacerbation of chronic obstructive pulmonary disease (COPD) and congestive heart failure. It is estimated to cause hundreds of thousands of hospitalizations and thousands of deaths annually in this age group globally.