Aviragen takes a tumble as RSV drug fails midstage trial

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The company will look at the data and decide the path forward in the second quarter, says its CEO.

Aviragen was pummeled in after-hours trading yesterday when it revealed one of its lead antiviral candidates had missed the mark in a phase 2a trial.

The Georgia-based biotech said its BTA585 drug failed to have any impact on viral load in around 20 adult patients given an intranasal inoculation with respiratory syncytial virus (RSV), the most common cause of acute lower respiratory tract infection in children.

CEO Joseph Patti said some biological activity was seen in the trial but there was a lot of variability in the viral load seen in patients and that—coupled with a small number of patients—made it difficult for the study to show an effect.

For now, the impact of the failed study is unclear. The company is playing its cards close to its chest, saying it will analyse the data set and make an announcement on the future of the oral fusion inhibitor before midyear.

At the moment the only option for the 2.1 million or so children in the U.S get RSV seriously enough to warrant medical attention is supportive care—inhaled ribavirin is sometimes used but has limited efficacy, while at-risk children can receive a preventative shot of AstraZeneca's Synagis (palivizumab).

For kids with established infections—which in some cases can be life-threatening—there is a pressing need for drugs that can tackle the virus. Efforts to develop RSV treatments have so far yielded no fruit, although Johnson & Johnson, Gilead Sciences and Ablynx have drugs in clinical testing. Meantime, progress towards a preventative vaccine has also been patchy. Novavax' RSV vaccine failed a phase 3 trial last year but remains in development, while Bavarian Nordic has a candidate in phase 2 trials.

The lack of available treatments helped BTA585 bag a fast-track designation from the FDA, but Aviragen hit a hurdle last year after the regulator placed the drug on clinical hold, requiring toxicity data in juvenile animals before the company can proceed to testing the drug in children. The company is hoping to get the clinical hold relaxed later this year.

The question mark hanging over the BTA585 program means Aviragen is banking on a good outcome in the phase 2b SPIRITUS trial of lead drug vapendavir, a drug intended to treat rhinovirus infections, and BTA074 for anogenital warts which is in a midstage trial due to complete enrollment in the third quarter.  

SPIRITUS is assessing vapendavir in moderate and severe asthma patients to see if the drug can prevent asthma attacks, and results are due in the next few weeks. According to the company, 45% to 80% of asthma exacerbations are linked to viral infections, and two thirds of the thought to be caused by rhinoviruses.