Cara's pain drug clears an abuse hurdle as it trots toward Phase III

CEO Derek Chalmers

The bull case for Cara Therapeutics' ($CARA) new opioid pain drug is that it can provide postsurgery relief without the abuse potential inherent in many heavy analgesics. Now the biotech is touting positive data from a trial in which its in-development treatment proved significantly less abuse-friendly than a commonly used opiate, results the company believes could make the drug a standout on the market.

To map the abuse potential of CR845, a Phase II intravenous treatment, Cara recruited 40 subjects who reported recreational drug use, separating them into four groups. One received a standard dose of CR845; another got a dialed-up, supratherapeutic dose designed to emulate prescription drug abuse; a third took pentazocine, a widely used opioid analgesic; and the final got placebo.

In top-line results from the study, subjects taking CR845 reported statistically significantly lower "drug liking," "feeling high" and "overall drug liking" scores--subjective measures recommended by the FDA--compared with those taking pentazocine. Both doses of CR845 charted similar results as placebo on the "drug liking" scale, Cara said.

Cara's shares surged 17% on Wednesday morning.

The company launched its abuse-liability study with the DEA in mind. The agency classifies all controlled substances on a range of abuse potential, with Schedule I reserved for the most dangerous and Schedule V the least. CR845's results compared with pentazocine, a Schedule IV drug, suggest it could become the first opioid treatment for acute pain to fall under Schedule V or skirt the system altogether, CEO Derek Chalmers said.

"The results are especially encouraging because CR845 was administered via an intravenous bolus, which provides the fastest delivery of the highest level of drug into the bloodstream, a critical determinant of abuse liability," Chalmers said in a statement.

Next, CR845 needs to prove itself in Phase III. Cara's treatment came through in two Phase II studies on postoperative patients, and those data, combined with the latest abuse-liability results, will inform the company's coming meeting with the FDA. If all goes according to plan, Cara will kick off a Phase III trial early next year.

The biotech pulled off a $55 million IPO earlier this year to pay CR845's way into late-stage trials, earmarking some of its funds for the development of an oral version of its lead candidate.

If and when Cara's drug hits the market, the company has faith it can carve out a space for itself. The most common opioids--including morphine, fentanyl and hydromorphone--work by activating the central nervous system's mu opioid receptors, relieving pain but often finding their way into the brain and leading to unintended effects like euphoria. CR845, by contrast, targets the kappa opioid receptors in the nerves outside the brain, a formulation that allows CR845 to provide analgesia without the abuse-friendly externalities, according to the company.

- read the statement

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