A repurposed drug originally used to treat ovarian cancer produced positive results in patients with advanced peritoneal cancers during a phase I clinical trial.

The drug, known under the brand name Nanotax, is a fine particle reformulation of paclitaxel, the standard treatment for ovarian cancer. The drug was developed by CritiTech, based in Lawrence, Kansas; the drug testing and phase I clinical trial were conducted by researchers at The University of Kansas Cancer Center, in Lawrence, and led by Stephen Williamson, MD, medical director of Cancer Clinical Trials.

Nanotax works by flipping the script on how paclitaxel is administered to patients and with how it is formulated, potentially making it a more effective and better tolerated treatment for ovarian and other abdominal cancers.

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During the trial, 5 of 21 patients with late-stage cancer survived more than 400 days after treatment with Nanotax at high concentrations for more than 4 weeks. Among the enrolled patients, 74% had ovarian cancer with tumors that had relapsed and metastasized to the peritoneum. The treatment was well tolerated by patients and no serious adverse reactions were reported from the drug.

Although the effectiveness of the new drug is not the main concern of a phase I trial, Williamson noted it was promising that five of the patients survived more than 1 year after starting the drug.

“Because these patients have advanced disease, we didn’t think we’d see much benefit,” said Williamson. “But some patients stayed on it for a longer period of time, which is more than what we expected and is promising.”

Unlike regular paclitaxel, which is administered intravenously over a few hours, Nanotax is given as a bolus injection. It is injected directly into the peritoneum through a catheter, which exposes the tumors to higher concentrations of the drug compared to standard IV paclitaxel treatment.

“The fine particles of this drug allow for it to be released slowly and stay in the abdomen,” said Katherine Roby, PhD, research associate professor in the Department of Anatomy and Cell Biology at KU Medical Cancer, who started her preclinical work on Nanotax more than a decade ago. “The concentration of the drug stays higher in the space where the cancer is, killing more cancer cells. This allows less of the drug to be absorbed systemically and fewer side effects.”

Previous studies on mice showed that compared with paclitaxel, Nanotax had a 10-fold higher maximum tolerated dose, and increased overall survival.

The lack of major side effects is also a good sign for future usage of Nanotax. When regular paclitaxel is given to patients, it is mixed with ethanol and castor oil derivative, and many patients develop an allergy to that additive (all patients are pretreated to prevent serious allergic reactions). Nanotax is the fine particle formulation of paclitaxel mixed with saline, which the body can absorb and tolerate much better.