(Adds share movement)
March 19 (Reuters) - Arena Pharmaceuticals Inc said on Monday a higher dose of its experimental drug succeeded in improving symptoms associated with ulcerative colitis, a chronic bowel disease, in a mid-stage study, sending its shares up 24 percent.
The company's shares, which surged as much as 62 percent to $50 after the bell, were trading at $38.20.
Arena said patients receiving the oral treatment showed statistically significant improvement in stool frequency, rectal bleeding and findings on endoscopy, compared with a placebo.
The company said it planned to move the drug, etrasimod, to late-stage trials based on the data.
Investors have focused on etrasimod and the company's pulmonary arterial hypertension drug since the U.S.-based Arena moved away from its weight-loss treatment due to underwhelming sales.
Arena sold the global commercialization rights to the weight-loss drug, Belviq, to Japanese drugmaker Eisai Co Ltd early last year.
Significantly more patients on etrasimod's higher dosage, 2 mg group, achieved endoscopic improvement, compared with the placebo, Arena said.
However, the company said a lower dose did not significantly improve the disease symptoms on a scale measuring severity of the three indications.
Ulcerative colitis is the most common type of inflammatory bowel disease that causes inflammation and ulcers in the large intestine lining.
Big drugmakers are also eyeing the ulcerative colitis treatment market.
An advisory committee to the U.S. Food and Drug Administration earlier this month recommended approval of Pfizer's Xeljanz to treat the disease, while Celgene's ozanimod is being tested in late-stage trials.
Arena's pulmonary arterial hypertension drug, ralinepag, is expected to begin late-stage trials.
The company is also testing a treatment for pain associated with Crohn's disease, which also causes inflammation but not restricted to the large intestine.
(Reporting by Manas Mishra in Bengaluru; Editing by Sriraj Kalluvila)