Failed clinical trials have put Vistagen on edge. After seeing two rival social anxiety disorder candidates flunk phase 2 studies, the biotech has paused plans to resume a phase 3 trial of its own once-failed prospect PH94B pending talks with the FDA.
Last year, Vistagen responded to the failure of a phase 3 trial of its social anxiety nose spray by bringing in independent biostatisticians to perform an interim analysis of its second study of the candidate. The biostatisticians gave Vistagen the green light to resume the study, PALISADE-2, without making changes to the design, putting the biotech on track to deliver data in the first half of 2023.
Despite that, Vistagen is yet to resume the study. Late Tuesday, the biotech revealed further analysis of its failed phase 3 trial led it to propose amendments to PALISADE-2 that are intended to address issues that may have contributed to the disappointing data generated in the earlier study. But external data have given Vistagen fresh questions about the impact of its proposed changes to the protocol, leading it to hit the brakes.
“The company believes it is not yet advisable to make a decision about resuming PALISADE-2 before discussing its broader phase 3 development plan for PH94B with the FDA and before further assessing the potential impact of the proposed adjustments to the PALISADE-2 protocol in light of two recently completed public speaking challenge [social anxiety disorder] studies conducted by peers, each of which did not achieve its primary efficacy endpoint,” Vistagen wrote in a statement about its quarterly results.
In December, Vanda Pharmaceuticals and Bionomics reported top-line results from phase 2 clinical trials of their rival candidates. Vanda reported recipients of its candidate, VQW-765, had “numerically lower stress levels” than their peers on placebo when asked to make an interview-style presentation in front of a panel. Bionomics was blunter, stating that BNC210 failed to beat placebo on the primary endpoint.
Vanda and Bionomics both assessed the effect of a single dose of their molecules on the performance of people with social anxiety disorder in a public speaking challenge. PALISADE-2 has a similar design and, as such, Vistagen is now questioning the approach.
The biotech plans to talk to the FDA about running a multiple-administration phase 3 study using the Liebowitz Social Anxiety Scale (LSAS) as the primary efficacy outcome measure. LSAS was the primary endpoint in the registration trials of the three oral antidepressants approved for the chronic treatment of social anxiety disorder in the U.S. Because LSAS measures change in fear and anxiety over time, rather than in a one-off stress situation, Vistagen now says it will show “the true impact” of PH94B on patients.
Vistagen’s statement lacks a timeline for getting PH94B back on track—and the cash clock is ticking. The biotech ended December with $25 million in the bank. Vistagen posted a loss of almost $10 million in the most recent quarter.