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with “nanospears” in medical treatment can be instinctively alarming, Kirkpatrick acknowledges, because people imagine the cells would die after being punctured. However, she says, Ensysce has shown in animal studies that its modified, soluble nanotubes can be absorbed safely by cells.
The company is now in preclinical testing for a nanotube complex that contains two types of siRNA designed to block a pair of cell elements implicated in cancer. The first siRNA aims at the protein EGFR, the target of cancer drugs such as Genentech’s erlotinib (Tarceva). The second siRNA acts against a mutant form of the KRAS gene, which can make cancer cells resistant to drug treatment.
Binding the siRNA molecules to a nanotube guards them from being broken down by ribonucleases and other bodily mechanisms as they pass through the bloodstream and penetrate cells, Kirkpatrick says. As a transport system into cells, nanotubes may prove better than the lipid nanoparticle capsules often used as vehicles for siRNA’s in drug development, Kirkpatrick says. Those lipid complexes can be as much as 150 nanometers wide, while the diameter of Ensysce’s single-walled carbon nanotube is one nanometer—about half the width of a strand of human DNA.
“We hope in the next twelve months to start testing this material in clinical trials,” Kirkpatrick says. The company has not yet chosen a cancer indication to focus on first, but the possibilities include colorectal, lung, and pancreatic cancer. The company now has eight employees and works with contract labs and manufacturers.
Ensysce was awarded $1.5 million from the State of Texas Emerging Technology Fund in 2010, and last year raised another $1 million from individual investors. The company is setting out to raise another $5 million to $10 million in its first outside funding round, Kirkpatrick says.
The fundraising effort could be challenging, Kirkpatrick says. Not only are carbon nanotubes a relatively untried technology in the drug arena, but siRNA’s are now also seen as risky bets.
The early excitement over siRNA’s has flagged in recent years as drug developers hit roadblocks. In 2010, two big pharma investors in RNA interference, Roche and Novartis, dropped their collaborations with Cambridge, MA-based Alnylam Pharmaceuticals (NASDAQ: ALNY). In 2011, Merck shut down the RNA interference research facility that came with the purchase of Sirna. However, Alnylam is one of the companies still betting on the potential of RNA interference. It now has partners including Genzyme and The Medicines Company, and regained investor confidence last year as it showed some promising results with its RNAi drug for the treatment of a rare disease called TTR amyloidosis. As its stock climbed on those results, Alnylam was able to cash in on favorable financial terms, reaping $174 million in a public stock offering this year.
Kirkpatrick says Ensysce appeals to investors who want to take a chance on something truly novel. Carbon nanotubes could become a “universal carrier’’ of therapeutic drugs, she says. Nanotubes a few hundred nanometers long offer a huge surface area where a variety of functional molecules can be stowed, including multiple copies of active drugs. Complementary drugs could be loaded onto the nanotubes together to make combination therapies, and other molecules could be added to selectively bind the complex to tumor cells, she says.
“We have many, many directions to go,” Kirkpatrick says.