Bilex Pharma is pleased to announce positive Phase 2 clinical trial results for BLX-RSV01, our investigational vaccine candidate for Respiratory Syncytial Virus (RSV). The trial demonstrated robust immune responses in adults aged 60 and older, a population particularly vulnerable to severe RSV disease.
Trial Results Exceed Expectations
The randomized, placebo-controlled Phase 2 study enrolled 350 healthy adults across 12 clinical sites in the United Kingdom. Participants received either a single dose of BLX-RSV01 at one of three dose levels or placebo, with immune responses and safety monitored over a 12-month period.
Key findings from the trial include:
- Strong Neutralizing Antibody Response: Participants receiving BLX-RSV01 showed a 9.8-fold increase in RSV-neutralizing antibodies at the selected dose level compared to baseline, significantly exceeding the pre-specified success criteria of a 4-fold increase.
- Rapid and Sustained Protection: Robust antibody responses were observed as early as 14 days post-vaccination and remained significantly elevated through 12 months of follow-up, suggesting potential for durable protection through an entire RSV season.
- Balanced Immune Profile: The vaccine induced both humoral and cell-mediated immune responses, with significant increases in RSV-specific T-cells that may contribute to broader and more effective protection.
- Consistent Results Across Age Groups: Similar immune responses were observed across all age subgroups within the study population, including those over 75 years of age who often show reduced responses to vaccination.
- Favorable Safety Profile: BLX-RSV01 was well-tolerated across all dose groups, with no vaccine-related serious adverse events reported. Most adverse events were mild to moderate and transient, consisting primarily of injection site reactions and short-lived systemic symptoms.
“These results represent a significant milestone in our RSV vaccine program,” said Dr. Sophia Chen, Chief Medical Officer at Bilex Pharma. “The magnitude and durability of the immune response, together with the favorable safety profile, strongly support advancement of BLX-RSV01 into pivotal Phase 3 evaluation.”
Addressing a Significant Public Health Need
RSV is a common respiratory virus that can cause serious illness in older adults and young children. In adults over 60, RSV causes approximately 177,000 hospitalizations and 14,000 deaths annually in the United States alone. Currently, no approved vaccines exist for RSV in any population, representing a major unmet medical need.
“The results from this Phase 2 study are particularly encouraging given the substantial disease burden of RSV in older adults,” commented Professor Michael Thompson, Principal Investigator for the trial and Director of Respiratory Infections Research at Imperial College London. “The strong immune response observed with BLX-RSV01, especially in terms of functional neutralizing antibodies, suggests potential for meaningful protection in this vulnerable population.”
Innovative Vaccine Design
BLX-RSV01 leverages Bilex Pharma’s proprietary StructVaxโข platform to present the RSV fusion (F) protein in its pre-fusion conformation, which has been shown to elicit more potent neutralizing antibodies compared to post-fusion conformations.
“Our vaccine’s design is based on precise structural understanding of the RSV F protein,” explained Dr. Eleanor Harrington, Chief Scientific Officer at Bilex Pharma. “By stabilizing the pre-fusion conformation and optimizing epitope presentation, we’ve developed a vaccine candidate that generates high levels of neutralizing antibodies targeting the most vulnerable sites on the virus.”
The vaccine utilizes Bilex Pharma’s AdaVantโข adjuvant system, specifically formulated to enhance immune responses in older adults whose immune systems typically show decreased responsiveness to vaccination.
Path Forward to Phase 3
Based on these positive results, Bilex Pharma plans to advance BLX-RSV01 into Phase 3 clinical development by Q4 2023. The Phase 3 program will evaluate the vaccine’s efficacy in preventing RSV-associated lower respiratory tract disease in adults aged 60 and older.
“We’re already engaged in productive discussions with regulatory authorities regarding our Phase 3 program,” noted Dr. Chen. “The strong data from this Phase 2 study have informed our dose selection and endpoint definition for the pivotal trials, positioning us for an efficient late-stage development program.”
The planned Phase 3 program will include approximately 25,000 participants across multiple countries, with sites in North America, Europe, and Asia to ensure broad population representation.
Expanding the Program
In parallel with the older adult program, Bilex Pharma is advancing plans to evaluate BLX-RSV01 in maternal immunization, with the goal of protecting infants during their vulnerable first months of life through the transfer of maternal antibodies.
“The strong immunogenicity data in our older adult population provides encouraging support for our maternal immunization strategy,” said Dr. Chen. “We plan to initiate a Phase 2 study in pregnant women later this year, with a focus on safety and transplacental antibody transfer to infants.”
Investment in Manufacturing Capabilities
In anticipation of late-stage clinical trials and potential commercialization, Bilex Pharma is investing in expanded manufacturing capabilities at its planned Manchester facility.
“The positive Phase 2 data accelerates our manufacturing scale-up activities,” said Dr. Robert Jenkins, Vice President of Manufacturing at Bilex Pharma. “We’re implementing a robust manufacturing process that will support not only our Phase 3 program but also potential commercial supply following regulatory approval.”
Statement from Leadership
“These results represent a pivotal moment for Bilex Pharma’s RSV program and validate our overall approach to vaccine development,” said Dr. Andras Ottlik, CEO and Director of Bilex Pharma. “RSV remains one of the most significant unmet needs in infectious disease prevention, and our progress brings us one step closer to delivering a vaccine that could substantially reduce the global burden of RSV disease.”
Dr. Ottlik added, “Following our recent Series B funding, we’re well-positioned to advance BLX-RSV01 through late-stage development and continue building our broader vaccine pipeline addressing major public health challenges.”
About the Phase 2 Trial
The Phase 2 trial (RSV-201) was a randomized, observer-blind, placebo-controlled study conducted across 12 clinical sites in the UK. The study enrolled 350 healthy adults aged 60 years and older, randomized to receive a single intramuscular injection of BLX-RSV01 at one of three dose levels (50ฮผg, 100ฮผg, or 150ฮผg) or placebo in a 1:1:1:1 ratio.
The primary endpoints were safety and RSV F protein-specific neutralizing antibody responses measured 28 days post-vaccination. Secondary endpoints included durability of immune response through 12 months, cell-mediated immune responses, and evaluation of functional antibody activity.
For more information about Bilex Pharma’s RSV vaccine program or other pipeline candidates, please visit our website or contact our investor relations team.
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.
About Respiratory Syncytial Virus (RSV)
RSV is a common respiratory virus that usually causes mild, cold-like symptoms. However, it can cause serious illness in infants, young children, and older adults. In the United States alone, RSV leads to approximately 177,000 hospitalizations and 14,000 deaths annually among adults 65 years and older, and is a leading cause of hospitalization in infants. Currently, no vaccines are approved to prevent RSV infection, though several candidates are in late-stage clinical development.