Prana Bio Huntington's Disease Drug Fails Key Efficacy Hurdles

Last month, I said to be careful about how Prana Biotechnology (PRAN) reports results from its Huntington's disease drug study. The company would likely issue a press release announcing positive results based on achieving the primary endpoint of safety and tolerability, even if the drug whiffed on the more important secondary efficacy endpoints. 

Sure enough, that's exactly what Prana did Tuesday, announcing "successful" phase II study results because its drug PBT2 was found to be safe when given to Huntington's disease patients. Unfortunately, PBT2 was unable to improve the motor or cognitive function of these same Huntington's patients compared to a placebo, the company said. 

Prana can spin results from the PBT2 "Reach2HD" study any way it likes, but in the end, the drug failed. A phase III study of PBT2 in Huntington's is planned, the company said Tuesday, but c'mon, this is just an exercise in futility. 

The phase II study enrolled 109 patients with early to mid-stage Huntington's. The patients were then randomized to one of three 26-week treatment arms: PBT2 100 mg, PBT2 250 mg or a placebo.

Ninety-five percent of the enrolled patients completed the study on their assigned dose and rate of adverse events reported were similar across all arms, achieving the safety primary endpoint, Prana said. 

To asses the efficacy of PBT2 in the study, Prana employed a Chinese menu of outcomes, nearly all of which failed to detect any benefit attributable to PB2 compared to placebo.

The higher dose of PBT2 was able to improve the cognition of Huntington's patients versus placebo in only one of eight separate tests -- the Trail Making Test Part B. 

On a composite score of executive function, the high dose of PBT2 showed a statistically significant improvement versus placebo but only in early-stage Huntington's patients, not the overall patient population. 

But buried deep in Prana's press release Tuesday was the most important -- and negative -- assessment of PBT2's efficacy: "No significant changes were seen in motor, functional, behavioural or global assessments in either PBT2 treatment group compared to placebo over the 26 week treatment period."

That's all you really need to know. 

Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.

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