An interim analysis of a phase IIb trial conducted by clinical-stage oncology company PharmAust (ASX: PAA) has provided supportive evidence of a therapeutic window for lead drug candidate monepantel to be used in the treatment of B-cell lymphoma growth in canines.
Monepantel blood plasma levels assessed from six dogs in the trial demonstrated an indicative optimal plasma level and target therapeutic dose for the drug, which is being administered to canine patients in tablet form after meals.
PharmAust said the results represent a material advance in optimising the treatment regimen for canine cancer patients and may have applications in other anti-cancer treatments in companion animals and humans.
The drug, as used in this stage of the study, has indicated no material adverse events and places the company in a strong position to further optimise treatment levels to facilitate a phase III trial later this year.
Blood plasma similarities
PharmAust chief scientific officer Dr Richard Mollard said a range of blood plasma levels was observed in the phase IIb trial in a similar way to a previous high-dose trial using monepantel tablets, but this time within a narrower spread.
“Examination of the blood plasma data in the context of our previous trial, while referencing side effects and efficacy, has reinforced our understanding of a target therapeutic window for monepantel’s use in dogs with B-cell lymphoma,” he said.
“Cancer therapy is all about optimising efficacy and minimising adverse events and this is particularly important with aggressive late-stage cancers such as stage four or five B-cell lymphoma.”
He said the planned phase III trial will include consideration of how monepantel could be integrated into the current standard of care.
PharmAust commenced its phase IIb trial of monepantel tablets to treat canine lymphoma in January, following on from phase IIa which resulted in tumour regression and a stabilising of the disease.
“We have been testing two hypotheses – firstly, that monepantel tablets could make cancer disappear and, secondly, that the tablets could stop cancer progressing (stable disease),” Dr Mollard said at the time.
The phase IIb trial is focusing on optimising the drug’s dosing regimen to maximise its anti-cancer activity.