11 April 2005. Sometimes it is not the drug that scuppers a clinical trial. Prana Biotechnology announced today that it is halting the much anticipated phase II/III clinical trial of its Alzheimer drug PBT1—before it even starts (see statement on Prana website).
PBT-1, aka clioquinol or iodochlorhydroxyquin, showed promise in an early pilot study (see ARF related news story), but Prana is pulling the drug because of unacceptable levels of a toxic impurity in the formulation. The impurity, a di-iodo form of clioquinol, is a side-product of the synthesis process, and Prana states that “attempts to reduce the impurity to safe levels are not likely to be successful in a timely manner and that further development of PBT1 is not warranted.”
The news is not necessarily a nail in the coffin for metal-protein attenuating compounds like clioquinol (see related ARF Live Discussion on the theory behind the development of clioquinol). The company has one other such drug, PBT2, in the pipeline. PBT2 does not contain iodine, so it cannot be marred by exactly the same problems as its forerunner. PBT2 is currently undergoing phase I safety trials in Holland.—Tom Fagan.