A new drug for an aggressive brain cancer has been cleared for clinical trials in patients with anaplastic astrocytoma, a rare brain tumor, and glioblastoma multiforme, an aggressive cancer of the brain.

The phrase Ib trial was approved after the drug, PAC-1, was successful at treating cancer in canine patients.

PAC-1 is unusual because it can cross the blood-brain barrier, which stops most anti-cancer drugs. The drug targets procaspase-3, an enzyme that is overexpressed in many cancer cells.

After promising tests on human cell lines and rodents, the University of Illinois research team conducted a trial of PAC-1 on pet dogs.

Dogs are a larger animal model and may more closely mimic cancer in humans.

"Research in pet dogs complements and builds on animal research in drug development trials," veterinary oncologist Dr. Timothy Fan, a professor of veterinary clinical medicine at Illinois, explained to ALN.

"The inclusion of pet dogs was conducted on a voluntary basis and there was careful thought about ensuring that the research remained humane. We were able to use these developments to further human medicine, as well as veterinary medicine."

The three dogs studied had a variety of naturally occurring cancers, including osteosarcoma, lymphoma, and glioma – a brain cancer similar to glioblastoma in humans.

The animals received daily oral doses of PAC-1 in combination with temozolomide and radiation.

A partial response, meaning there was at least a 30% reduction in the tumor, was seen in all three pet dogs. Additionally, one of the dogs was declared tumor free 84 days after the combination therapy.

Few observable side effects were seen in the dogs, besides some occasional gastrointestinal distress.

The results were published in the journal Oncotarget.

"Optimistically, these positive safety findings in pet dogs suggest that we should have similar results in people with these aggressive cancers," Fan added.