Aviragen Therapeutics reported its second Phase II trial disappointment in as many weeks. The firm said that the Phase IIb SPIRITUS study evaluating the oral capsid-binding antiviral drug vapendavir in asthma patients with rhinovirus (RV) infection failed to meet its primary endpoint. At the start of this month, Aviragen reported on topline Phase IIa data indicating that a second clinical candidate, BTA585, failed to reduce viral load in adults challenged intranasally with respiratory syncytial virus (RSV). BTA585 is an oral selective inhibitor of human RSV fusion protein-mediated viral entry.

The Atlanta-based firm confirmed that it would fully evaluate data from the SPIRITUS study with vapendavir before deciding whether to start a Phase II trial with the drug in hematopoietic stem cell transplant patients with rhinovirus infection. “We are disappointed that the SPIRITUS trial did not meet its primary endpoint in this patient population,” said Joseph Patti, Ph.D., president and CEO of Aviragen.

The SPRITUS study in North America and Europe enrolled 455 adult patients with moderate-to-severe asthma who had a history of losing asthma control when suffering from an upper respiratory tract infection. Of these, 168 patients had laboratory-confirmed human RV infection. The placebo-controlled trial failed to reach its primary endpoint of a statistically significant reduction in the asthma control questionnaire-6 (ACQ-6). Aviragen says the improvement in ACQ-6 in the placebo cohort was larger than expected. The study did show that vapendavir therapy resulted in statistically significant antiviral effects in patients who received the drug within 24 hours of their first symptoms. This finding was consistent with results from previous studies.

“There was evidence of an antiviral effect in patients that received vapendavir within the first day following the onset of their symptoms, and as such, 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, where the ability to stop the progression of the RV infection could be beneficial,” Dr. Patti stated.

Aviragen’s clinical pipeline includes antiviral candidates against human RV, RSV, and human papillomavirus (HPV). BTA585 is an oralselective inhibitor of human RSV fusion protein-mediated viral entry. BTA074 is a protein–protein inhibitor of the interaction between E1 and E2 from HPV 6 and 11. The drug is being evaluated in Phase II studies as a topical treatment for genital warts. 

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