Double-whammy for Aviragen as lead drug trial ends in failure

A decision on a trial of vapendavir in stem cell transplant patients will hinge on analysis of the asthma data.(Pixabay)

It's been a torrid few days for antiviral drug developer Aviragen as a second phase 2 trial ended in failure, all but decapitating its R&D pipeline.

The phase 2b SPIRITUS trial of vapendavir in moderate to severe asthma patients failed to hit its main objective of curbing breakthrough symptoms and attacks in asthmatics with rhinovirus (RV) infections, according to a statement from Aviragen.

That setback comes hard on the heels of the revelation that Aviragen's second most advanced program—respiratory syncytial virus (RSV) candidate BTA585—failed a phase 2a trial, and also casts some doubt on whether a planned trial of vapendavir in stem cell transplant patients will go ahead.

"We plan to take time to fully analyze the data before making a decision on whether to initiate a study in hematopoietic stem cell transplant patients," said CEO Joseph Patti.

Shares in the Georgia-based biotech have been in steep decline after the announcement, plunging 43% to 68 cents in after-hours trading as investors absorbed the news. Analysts at Ladenburg Thalmann downgraded the stock to 'neutral' from 'buy' this morning, having started coverage of the firm last September with a $2.50 price target.

Patti said there had been some evidence that vapendavir had an antiviral effect in patients treated within one day of displaying symptoms, and that this data would be analyzed before the company makes a decision on testing the drug in stem cell transplant patients "where the ability to stop the progression of the RV infection could be beneficial."

In the two-week SPIRITUS trial, vapendavir was unable to show a significant reduction compared to placebo on a standard patient questionnaire (ACQ-6) focusing on asthma symptoms, a result the company blamed on a better-than-expected improvement for the control group.

The study had an 80% chance of detecting a 0.5 point change in the ACQ-6 score, which is considered clinically relevant, and according to Patti was "well powered and well designed." There were also no differences between vapendavir and placebo on lung function tests, which had been mooted as a possible primary endpoint for future phase 3 trials.

With BTA585's future up in the air (and still subject to an FDA clinical hold) and vapendavir in trouble, Aviragen's next most advanced asset is BTA074, a human papillomavirus-targeted antiviral in a phase 2 trial for genital warts that has been held up by manufacturing issues.