What: Shares in Cara Therapeutics  (NASDAQ:CARA) are surging higher by 30% today after the company reported that its lead product candidate CR845 met its primary endpoint in a mid stage trial.

So what: Cara Therapeutics is developing CR845 as a treatment for acute pain and uremic pruritis, a chronic itch affecting roughly half of all kidney failure patients.

In a 65 person mid stage trial, uremic pruritus patients experienced a 54% bigger drop-off in worst itch intensity scores when taking CR845 than patients experienced while taking a placebo. Secondary endpoints for quality of life and a reduction in sleeplessness were also met.

Now what:  Cara Therapeutics' positive mid stage study clears the way for the company to kick-off a larger phase 3 study next year. While there's no guarantee that CR845 will prove to be effective in this upcoming trial, results confirming its mid stage data could lead to an eventual FDA approval in this condition.

If approved, the drug could potentially benefit up to 50% of the 400,000 Americans receiving hemodialysis, many of whom fail to control their itch with corticosteroids and antihistamines.

Although the results and potential patient pool are intriguing, a bigger opportunity for CR845 may exist as a therapy for acute pain. A phase 3 trial for use in post operative patients to treat pain gets under way this quarter and if successful, CR845 could prove to be an effective pain drug alternative for patients suffering from side effects tied to traditional opioid therapy.

Although CR845 could carve out market share in pain treatment and pruritis, I'm uncertain just how big demand could prove to be for this drug. Admittedly, Cara Therapeutics' $361 million market cap indicates that it's not very expensive, but until I have additional insight into potential demand for CR845, I'm content to sit on the sidelines and wait for phase 3 data, which should be available next year.

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