Prana Biotechnology (ASX:PBT/NASDAQ: PRAN) has today released the top line results of the 12-month Phase II Imaging trial in Alzheimer's Disease ("IMAGINE" Trial), based on draft results.
Prana's PBT2 did not meet its primary endpoint of a statistically significant reduction in the levels of beta-amyloid plaques in the brains of prodromal/mild Alzheimer's disease patients, as measured using PiB-PET Standardized Uptake Value Ratio (SUVR). Whilst there was a reduction in the overall levels of the PiB PET signal in patients treated with PBT2, the results were confounded by an atypical reduction of levels of the PiB PET signal in the placebo group as well.
Commenting on the result, Geoffrey Kempler, CEO of Prana Biotechnology said: "This is the first time that Prana has looked at PiB-PET in a study with PBT2 to measure its effect on insoluble amyloid plaques. In our previous Alzheimer's study (EURO)1, we looked at levels of unaggregated soluble Abeta peptides in spinal fluid, and they were significantly reduced with PBT2 treatment. So in the IMAGINE trial we looked for an impact on the insoluble plaques as well, but did not see it differ significantly from the placebo."
"It is possible the result may point to PBT2 targeting soluble species of Abeta including toxic oligomers rather than plaques. Abeta oligomers are not visible in the PiB-PET scans which can only detect amyloid plaques. Alternatively, what we are seeing is simply the result of an inconclusive imaging readout in a small sample size with 42 participants (15 on Placebo, 27 on PBT2)".
No improvement was observed on the secondary endpoints of brain metabolic activity, cognition and function; however there was a trend towards preserving hippocampal brain volume in the PBT2 group. Specifically, there was less atrophy in those patients treated with PBT2 relative to placebo, 2.6% and 4.0%, respectively. This is consistent with published measures of atrophy in AD patients versus healthy controls2 of 4.7% and 1.4%, respectively. The company is tracking measures of brain volume and cognition in the current 12 month extension study that will be completed at the end of the year. Further analysis of the results is ongoing.
Importantly, PBT2 was shown to be safe and very well tolerated over the 52 weeks. The adverse event profile was equivalent between placebo and treated groups. Forty of the 42 enrolled participants (95%) completed the 52 week treatment period.
Mr. Kempler concluded: "Whilst not meeting all of our hopes, this result does not deter us from the future development of PBT2, a safe and well tolerated drug candidate for Alzheimer's disease. Our scientists and those from other institutes have developed a strong body of evidence for the efficacy of PBT2 in Alzheimer's disease. The suggestion of beneficial effect of PBT2 on brain volumes first seen in the Reach2HD Huntington disease trial and now in this Alzheimer's disease IMAGINE trial is intriguing. We are consulting with experts in the field to further assess these results and to consider how best to progress PBT2 in Alzheimer's disease. Indeed, the IMAGINE Extension trial is continuing, and data from this trial is likely to inform the next steps for an AD program."
Prana is proceeding with its plans toward a confirmatory study for Huntington disease. Based on Prana's previous discussion with the US Food and Drug Administration, the data on safety and tolerability of PBT2 in Alzheimer's disease will support the future clinical development and, ultimately, a New Drug Application in Huntington disease.
Prana has a cash position of AU$25.4 million as at 31 March 2014.
Investor conference call
Prana is hosting an investor conference call at 11.00pm Australian Eastern Daylight Savings time on Monday 31st March (8.00am USA EDT; 5.00am USA PDT, and 1.00pm UK BST).
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