Fueled by early success, Enanta paves way for mid-stage RSV study in adult patients later this year
RSV, a field littered with failure, has another hopeful.
On Friday, Enanta Pharmaceuticals showed that its experimental treatment, EDP-938, conferred a statistically significant reduction in the respiratory syncytial virus (RSV) viral load in healthy adults inoculated with the virus. Now comes the hard part.
“While we view today’s positive results from the Phase 2a human challenge study as encouraging, we anticipate that results from the Phase 2b will go a much longer way as to determining whether EDP-938 is a viable treatment for RSV…We think the path to commercialization here is particularly difficult to navigate, given that RSV infection resolves fairly quickly without intervention and the key will be showing a difference in terms of time to resolution,” Baird’s Brian Skorney wrote in a note.
Once 115 healthy adults were inoculated with the virus, patients were randomized to either get placebo or administered two different EDP-938 regimens. The Enanta drug is an N-protein inhibitor, which the company believes has an edge over fusion inhibitors currently in development, as it targets the virus’ replication machinery. Compared to the placebo, patients given either regimen achieved a statistically significant reduction (p<0.001) in RSV viral load and was well tolerated, Enanta said.
“We think this study largely confirms the anti-viral activity of this drug, but was widely expected and the program is now moving into the more costly and difficult period of clinical development…Recall, RSV has been a tough space, with Johnson and Johnson discontinuing development of lumicitabine, even after the medication had produced promising Phase 2a results from a similar human challenge model,” Skorney noted.
The complex molecular structure of RSV has largely thwarted drugmakers from developing a vaccine or a treatment for an infection that afflicts most American infants before their second birthday. For most older healthy children and adults, RSV causes little discomfort beyond a common cold, but in high-risk groups with compromised immune systems such as infants and the elderly, it can lead to more serious lung and airway infections.
But efforts to stifle the infection have culminated in a litany of failures. Most recently, J&J $JNJ terminated Phase IIb trials of its RSV drug lumicitabine, Regeneron $REGN abandoned its RSV drug after a late-stage failure and Novavax’s $NVAX RSV vaccine has failed a pair of Phase III trials (although it insists there’s a way forward). The only silver lining is from AstraZeneca $AZN, the original maker of the only preventative treatment, Synagis, for serious lower respiratory tract infections (LRTI) caused by RSV in infants and young children. In February, the British drugmaker was granted expedited review from US and EU regulators for its long-acting RSV drug, MEDI8897.
Buoyed by its early success, Enanta is planning its Phase IIb study by the end of 2019 in adult outpatients with confirmed RSV infections, company chief Jay Luly said.
The company’s shares $ENTA initially rose, but closed down about 12% at $85.81 on Friday. “I just don’t think RSV treatment is an indication that investors are ready to give credit to at this stage so it became a sell the news event,” Skorney told Endpoints News.
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