Capsaicin-like Drug for Knee OA

The pain-fighting qualities of capsaicin, the active ingredient in chili peppers, may soon be available as an injectable treatment for knee osteoarthritis (OA).

Boston-based drug maker Centrexion Therapeutics recently completed phase-2 trials of CNTX-4975, a medication that is based on a highly potent, ultrapure, synthetic form of trans-capsaicin (a medicine traditionally derived from the chili plant).

CNTX-4975 is designed to be injected directly into the site of pain to provide rapid and long-lasting pain relief. It works by selectively targeting the capsaicin receptor (TRPV1) to rapidly inactivate only the local pain fibers transmitting signals to the brain. With a short half-life, it clears from the body within 24 hours. Centrexion says the approach provides pain relief that can last for months until the ends of the local pain fibers regenerate, while leaving the rest of the nerve fiber functioning normally and without the risks of toxicities of NSAIDs and injected steroids or their side effects.

Recently, 175 people with chronic moderate-to-severe knee OA pain took part in a randomized, double-blind, placebo-controlled study of the medication. Twenty-two percent of patients achieved a 90 percent or greater reduction in pain and 67 percent of patients achieved 50 percent or greater reduction in pain.

“As our population ages, chronic osteoarthritis pain is an important and growing problem. Short of joint replacement, which carries risks associated with any surgery, there are insufficient options,” says Nathaniel Katz M.D., M.S., adjunct associate professor of anesthesia at Tufts University School of Medicine. “CNTX-4975 represents an important new approach for pain relief for patients. The results seen in this clinical trial suggest that the medicine warrants further clinical investigation.”

Randall M. Stevens, M.D., chief medical officer for Centrexion Therapeutics adds: “These phase 2b data show the largest clinically relevant reductions in knee osteoarthritis pain reported for any drug treatment, marketed or in development.” He foresees people who receive the drug resuming activities such as walking up stairs.

The drug is also being tested to treat Morton’s neuroma, a rare disorder that causes foot pain, as well as knee OA in pet dogs. The next round of trials should begin this year.

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