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Positive Data Reported for New Pain Drug

Kappa opioid agonist reduces abuse potential

Positive results have been reported from a human abuse liability (HAL) trial of intravenous (IV) CR845 (Cara Therapeutics), a first-in-class peripherally selective kappa opioid agonist.

Top-line results showed that therapeutic and supratherapeutic doses of CR845 met the trial’s primary endpoint by demonstrating significantly lower “drug liking” scores (P < 0.0001), as measured by a visual analog scale, compared with IV pentazocine, a schedule IV opioid receptor agonist. CR845 also demonstrated significantly lower “feeling high” and “overall liking” scores (P < 0.0001) compared with pentazocine. Moreover, both doses of CR845 were rated equivalent to placebo on “overall drug liking” and “take drug again” measures.

“Drug liking,” “feeling high,” “overall liking,” and “take drug again” scores are standard subjective measures recommended by the FDA to assess a drug’s abuse liability, both for recommended scheduling as well as labeling.

The HAL trial was a double-blind, randomized, active- and placebo-controlled, four-way crossover study that evaluated the abuse potential of IV CR845 in 40 non-dependent, recreational polydrug users with lifetime and recent hallucinogenic drug use. The trial’s primary objective was to measure the relative abuse potential of both a therapeutic and a supratherapeutic dose of CR845 compared with that of an IV dose of pentazocine. Pentazocine is a mixed-action kappa and mu opioid receptor agonist used clinically in the treatment of moderate-to-severe pain and is classified by the Drug Enforcement Agency (DEA) as a schedule IV drug, indicating reduced abuse liability compared with that of most other opioids.

CR845 is currently in development for the treatment of acute and chronic pain. In several randomized, double-blind, placebo-controlled phase II trials in patients undergoing laparoscopic hysterectomy or bunionectomy procedures, IV CR845 treatment resulted in statistically significant reductions in pain intensity and opioid-related side effects. In more than 400 subjects dosed to date, CR845 was found to be safe and well tolerated, without incurring the dysphoric and psychotomimetic side effects that have been reported with centrally acting (CNS-active) kappa opioid receptor agonists.

 According to the Centers for Disease Control and Prevention (CDC), 46 people die each day in the U.S. from an overdose of prescription pain medications. Statistics compiled by the National Institute on Drug Abuse (NIDA) indicate that young adults (aged 18 to 25 years) are the biggest abusers of prescription opioid pain relievers. In 2010, almost 3,000 young adults died from prescription-drug (mainly opioid) overdoses — more than died from overdoses of any other drug, including heroin and cocaine combined — and many more needed emergency treatment. The total cost of prescription opioid abuse in the U.S. was $55.7 billion in 2007.

Source: Cara Therapeutics; October 29, 2014.

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