Drug-Like "Compounds" May Improve Prostate-Cancer Treatment

By Jane Farrell

Researchers from Southern Methodist University have discovered three new compounds that could, ultimately, offer better survival odds to prostate cancer patients.

The drug-like compounds can be modified and developed into medicines that target a protein in the human body that is responsible for chemotherapy resistance in cancers, said biochemist Pia D. Vogel, lead author on the scientific paper reporting the discovery.

So far there’s no approved drug on the market that reverses cancer chemotherapy resistance caused by P-glycoprotein, or P-gp for short, said Vogel, a biochemistry professor at SMU. One potential drug, Tariquidar, is currently in clinical trials, but in the past, other potential drugs have failed at that stage.

“The problem when a person has cancer, is that the treatment itself is composed of cellular toxins — the chemotherapeutics that prevent the cells from dividing. Usually upon the first chemotherapy treatment the cancer responds well, and initially goes away. Ideally it doesn’t come back,” said Vogel, director of SMU’s Center for Drug Discovery, Design and Delivery.

“Sometimes, however, the cancer returns,” she said. “The reason often is that some of the cancer cells “learn,” after the first rounds of chemotherapy, how to make a lot of this P-gp pump. The normal function of P-gp is to pump toxins from cells, so it has evolved to protect cells against a large variety of toxins, including almost all currently available chemotherapeutics. After initial exposure, the cells surviving the chemo make so much P-gp that it allows the cells to pump the chemotherapy drugs straight back out of the cells during subsequent rounds of treatment.”

As a result, P-gp causes resistance of the diseased cells to a majority of drugs currently available for the treatment of cancer, as well as drugs used for treatment of infectious diseases like HIV/AIDS.

According to a news release from the university, the new drug-like compounds discovered by Vogel and her co-authors offer hope that using a computer-generated P-gp model, developed to accurately mimic the physical, chemical and biological functions of the protein in the human body, will speed up the drug discovery process and work in real life as well.

“These are not drugs yet. We still have to develop them before they can go in the clinic,” Vogel said. “But what we know now is that they’re not toxic — they have low toxicity to noncancerous cells, so that’s a pretty good predictor that they may be good candidates for drug development. But we need to do much more work.”

A pharmaceutical hit compound, like those discovered by Vogel and her co-authors, is a compound that is a promising candidate for chemical modification so it can eventually be delivered to patients as a therapeutic drug. In the case reported here, the compounds were commercially available for testing. The timeline from drug discovery to development to clinical trials and approval can take a decade or more.

The study was reported in the journal Pharmacology Research & Perspectives.