A review of the PBT2 data with input from doctors not involved in the study was posted to the Alzforum website yesterday. Alzforum is a web-based scientific community focused on Alzheimer's disease and related disorders. Independent experts said PBT2 looked safe but saying anything about efficacy in Huntington's was an overreach.
Several outside scientists were careful to point out that the study was not powered to evaluate the drug's effectiveness. In this trial, people on PBT2 fared no better than those on placebo on tests of motor function, behavior, functional abilities, or biomarkers. "It is good to see that PBT2 met its safety goals so that it can progress to an efficacy study," said Lon Schneider, University of Southern California, Los Angeles. However, he cautioned that "the clinical outcomes of this Phase 2 study should not be used to predict outcomes of a Phase 3 study."
The Alzforum review spoke with a number of experts in neurodegenerative disease about the PBT2 data, including Rachelle Doody of Baylor College of Medicine:
"We can't be sure that the drug met safety and tolerability requirements based on the limited data presented.," said Rachelle Doody, Baylor College of Medicine, Houston, who was uninvolved in the trial. Doody said she would need to see more specifics on how many adverse events and serious adverse events occurred in each group.Maybe it's just me, but is the following quote in the Alzforum review from Cristina Sampaio, CHDI, Princeton, a scolding of Harvard professor and Prana Chief Science Officer Rudy Tanzi for his cheerleading tweets about PBT2 on Tuesday?
A peer-reviewed paper is forthcoming, said Ray Dorsey, University of Rochester, New York, in a presentation to investors. Dorsey is the principal investigator of the trial. "I was pleased to hear these results would be submitted to peer-reviewed publications," noted Cristina Sampaio, CHDI, Princeton, New Jersey. "A proper evaluation of this trial must await full access to the data. Until that happens, undue enthusiasm can only harm the patients."
And then there's this comment from Paul Aisen of the University of California, San Diego, with an assist from Doody:
Paul Aisen, University of California, San Diego, pointed out that these results cannot be interpreted as suggesting efficacy, however, because the Trail Making Test was the only one of eight cognitive tests administered that showed a positive effect, and also because Prana did not control for false positives on this outcome. "Analyses of anything having to do with cognition or function did not meet the pre-specified objectives," added Doody. "The tertiary analyses of various subcomponents are inconclusive and uninterpretable."Healthcare investor Ian Estepan summed up the importance of the Alzforum review nicely: