Enanta Pharmaceuticals (ENTA.O), opens new tab said its experimental respiratory syncytial virus treatment significantly quickened recovery in a mid-stage study of adults at high risk of complications from the infection.
The Monday announcement boosted shares of the drug developer by 40%.
The oral drug, zelicapavir, however, failed to meet the main study goal of improving the time taken to resolve certain symptoms of lower respiratory tract disease associated with RSV infection.
RSV is a common respiratory virus that causes seasonal infections such as the flu. It is a major cause of pneumonia and death in infants and older adults.
All RSV symptoms in patients on zelicapavir resolved 2.2 days faster than a placebo, and 6.7 days faster in the high-risk group, which had people who either had congestive heart failure, chronic obstructive pulmonary disease or were aged 75 or above, the company said.
“We believe the trial results validate there is a high likelihood that Zelicapavir is an approvable RSV therapeutic product,” said H.C. Wainwright analyst Brandon Folkes.
With an estimated two to three million cases of RSV annually among high-risk adults in the U.S., even modest market penetration translates to a very significant commercial opportunity, Folkes said.
The drug met several other secondary goals of the study, including reduction in hospitalization rates.
The data will inform a future late-stage study, including identifying its potential primary endpoints, Enanta’s medical chief, Scott Rottinghaus, said on a conference call.
CEO Jay Luly said Enanta is looking for a partner to further develop zelicapavir.
There are currently no U.S.-approved drugs to treat RSV in adults. Prevention measures rely on recently approved vaccines from GSK (GSK.L), opens new tab, Pfizer (PFE.N), opens new tab and Moderna (MRNA.O), opens new tab and antibody drugs from Merck (MRK.N), opens new tab, Sanofi (SASY.PA), opens new tab and AstraZeneca (AZN.L), opens new tab for children.
Gilead (GILD.O), opens new tab is also developing a drug called obeldesivir to treat the disease.
