Alnylam Pharmaceuticals, Inc., a leading RNAi therapeutics company, has initiated a human experimental infection study with respiratory syncytial virus (RSV) designed to establish a safe and reliable RSV infection of the upper respiratory tract in adult volunteers.

Upon determination of the optimal level of RSV inoculum, Alnylam plans to initiate a subsequent clinical protocol to evaluate the anti-viral activity for ALN-RSV01, an RNAi therapeutic being developed for the treatment of RSV infection. ALN-RSV01 is the industry's most advanced RNAi therapeutic program for the treatment of an infectious disease and is an Alnylam proprietary program.

The experimental infection study is designed to safely and reliably establish infection in healthy adult volunteers. Approximately 40 subjects are planned to be enrolled into the study, where gradually increasing levels of virus will be used to determine the optimal infectious inoculum. Following determination of the optimal level of the RSV inoculum, Alnylam expects the next stage of this programme will be performed with a separate clinical protocol using ALN-RSV01 in order to investigate the drug's anti-viral properties.

"Viral challenge models have been safely used to develop many anti-viral treatments including those for flu and the common cold. This new Alnylam study represents an important step forward in the overall clinical development of ALN-RSV01, as it advances this program toward generation of proof-of-concept anti-viral activity data in man," said Akshay Vaishnaw, M.D., Ph.D., vice president, Clinical Research of Alnylam. "Continued development of ALN-RSV01 is supported by an encouraging safety profile in recently completed phase I intranasal studies together with promising pre-clinical efficacy data."

ALN-RSV01 is an RNAi therapeutic being developed for the treatment of RSV infection, a prevalent viral infectious disease in pediatric and certain adult patient populations. ALN-RSV01 was found to be safe and well tolerated when administered intranasally in relevant doses to human adult volunteers where it demonstrated a safety profile comparable to placebo. A phase I inhalation safety study is currently enrolling subjects in the US, and Alnylam expects to initiate a phase II study in naturally infected patients in the first half of 2007.

"Alnylam has made considerable progress in the development of ALN-RSV01, which entered clinical development late last year. There is significant need for an effective anti-viral for the treatment of RSV infection, a cause of serious illness in immune compromised patient populations and the leading cause of infant hospitalization in the US," said John P. DeVincenzo, M.D., associate professor of Pediatrics at the University of Tennessee Health Science Centre. "ALN-RSV01 has the potential to be a breakthrough treatment for RSV based on its novel mechanism of action, impressive pre-clinical efficacy data, and safety profile to date.

Alnylam's experimental infection study may prove to be a compelling and efficient way to establish anti-viral activity, thereby representing the first opportunity to potentially establish human proof of concept for ALN-RSV01."

RSV is a highly contagious virus that causes infections in both the upper and lower respiratory tract. RSV infects nearly every child at least once by the age of two years and is a major cause of hospitalization due to respiratory infection in children and in people with compromised immune systems, and others. RSV infection typically results in cold-like symptoms but can lead to more serious respiratory illnesses such as croup, pneumonia, bronchiolitis, and in extreme cases, death.

RSV infection in the pediatric population accounts for more than 100,000 hospitalizations per year in the US. In addition, RSV infection in infants has been linked to the development of childhood asthma. As a result, there is a significant need for novel therapeutics to treat patients who become infected with RSV.


RNA interference, or RNAi, is a naturally occurring mechanism within cells for selectively silencing and regulating specific genes. Since many diseases are caused by the inappropriate activity of specific genes, the ability to silence genes selectively through RNAi could provide a new way to treat a wide range of human diseases. RNAi is induced by small, double-stranded RNA molecules. One method to activate RNAi is with chemically synthesized small interfering RNAs, or siRNAs, which are double-stranded RNAs that are targeted to a specific disease-associated gene. The siRNA molecules are used by the natural RNAi machinery in cells to cause highly targeted gene silencing.