A clinical-stage biopharmaceutical company on Thursday disclosed disappointing data from a key study that tested its chronic pain treatment in patients with osteoarthritis.

Cara Therapeutics Inc's worse-than-expected results sent its shares down almost 32 percent after the bell on Thursday.

The company had tested three dosages of its drug CR845 in 476 patients with osteoarthritis of the hip or knee, experiencing moderate-to-severe pain, against a placebo.

Two dosages of the drug ? 1 mg and 2.5 mg ? failed to meet the main goal of reducing pain intensity in patients, while the 5 mg dose exhibited a statistically significant reduction in joint pain in patients with osteoarthritis of the hip, the company said.

However, the 5 mg dose did not demonstrate a reduction in joint pain of the combined patient group.

Cara is also evaluating CR845 for the treatment of pruritus, a condition that causes severe itching of the skin. Its stock tumbled to $17.40 during the after-market hours.