Prana shares sink after Alzheimer's trial disappoints

Prana Biotechnology (ASX:PBT) shares slumped 73% on Tuesday, after the company announced that a phase II imaging trial of Alzheimer’s drug candidate PBT2 failed to meet its primary endpoint.

PBT2 did not achieve a statistically significant reduction in the levels of beta-amyloid plaques in the brains of mild Alzheimer’s disease patients, as measured using the PiB-PET Standardised Uptake Value Ratio (SUVR).

The results do show a reduction in levels of PiB PET signal in PBT2 treated patients, but these are confounded by an atypical reduction in the placebo group as well.

No improvement was observed on the secondary endpoints of brain metabolic activity, cognition or function, but there was a trend towards preserving hippocampal brain volume in the treated group.

Prana CEO Geoffrey Kempler said the result may point to PBT2 targeting soluble species of Abeta including toxic oligomers - which are not visible on PiB-PET scans - rather than plaques.

“Alternatively, what we are seeing is simply the result of an inconclusive imaging readout in a small sample size with 42 patients,” he said.

On the bright side, PBT2 was found to be safe and well tolerated over a 52-week period, with 40 of the 42 enrolled participants completing the full year of treatment.

“Whilst not meeting all of our hopes, this result does not deter us from the future development of PBT2,” Kempler commented. “The suggestion of beneficial effect of PBT2 on brain volumes ... is intriguing. We are consulting with experts in the field to further assess these results and consider how best to progress PBT2 in Alzheimer’s disease.”

Prana is also developing PBT2 as a prospective treatment for Huntington’s disease, and expects the safety and tolerability data from the Alzheimer’s trial to support the candidate’s clinical development in this indication.

Prana Biotechnology (ASX:PBT) shares fell 73.56% to $0.275 on Tuesday, a day after the trial results were announced. The shares were trading 3.64% lower at $0.265 as of around 1.30 pm on Wednesday