Purdue's breakthrough research in the 1980s and 1990s on the pawpaw tree and its cancer-killing compounds has had a impact on cancer research but has failed to reach the markets today due to poor solubility and supply difficulties.

Nicholas Oberlies, the then-doctoral student who worked under Jerry McLaughlin, the head researcher and former professor of pharmacognosy in Purdue's College of Pharmacy, recalls the basis for the research done more than 20 years ago.

Oberlies, now a professor of chemistry at University of North Carolina at Greensboro, compared the research to Taxol, a natural chemotherapy drug that treats ovarian cancer and breast cancer.

“We were trying to discover other compounds from nature that had properties that could kill cancer cells and could potentially become drugs,” Oberlies said.

Oberlies discussed the popularity of natural drugs in drug stores.

“If you walk into your average pharmacy, about 25-30% of all the drugs in the pharmacy are from natural products,” Oberlies said.

Oberlies explained that this includes pain medicine, cough syrup, aspirin and more.

By studying different parts of plants from the Annonaceae family from all over the world, including Ecuador and Brazil, McLaughlin and his team of 15-20 researchers eventually made historic discoveries from one tree.

Funded by the National Cancer Institute, the team studied samples of the pawpaw, a tree native to North America that grows in Indiana, to discover that the series of compounds called Annonaceous acetogenins within the bark, seeds and leaves contained anti-cancer properties.

Tested in petri dishes, the compounds were proven to be effective in killing tumors resistant to other anti-cancer agents.

Oberlies claimed their research was prolific and groundbreaking.

“There was probably one other group in the world that was that prolific in that space, meaning with those class of compounds,” Oberlies said.

Members of the researching team advanced significantly in their careers and education following the study of the tree.

“We worked really hard on it for a really long period of time. A lot of people got their degrees and eventually went on to great careers based on their training here,” Oberlies said.

The components of the tree went on to be tested further.

“They never got tested in humans; they certainly got tested in animals,” Oberlies said.

The team tested the drug on mice, killing several in the process due to imperfect doses. Nevertheless, the discoveries were outstanding, according to Oberlies.

“It killed just about every cancer cell we tested,” Oberlies said.

However, the drug failed to reach markets and go beyond laboratory research.

Oberlies said the reason the cancer-killing tree never made it to the market was due to poor water solubility, meaning the compounds were unable to be dissolved in water. This made it difficult to turn into a pill or an intravenous infusion. The drug delivery and supply were issues as well.

According to Oberlies, McLaughlin planted pawpaw trees around West Lafayette in order to supply it, but taking care of the trees was a difficult process.

Although developing a cancer-killing drug was Oberlies’ main goal, today the pawpaw compounds have been extracted to make a lice-killing shampoo from the company Nature Sunshine, along with other herbal remedies.

“They never made it as drugs, but that doesn’t mean it wasn’t important. Will they make it as drugs in the future? Who knows,” Oberlies said.

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