** Shares of drugmaker Ardelyx ARDX.O rise 1.01% to $7.97 premarket

**  Co says it has begun dosing patients in a late-stage trial testing Ibsrela in adults with chronic idiopathic constipation, a long-term condition that causes infrequent or difficult bowel movements

** The  trial will enroll about 700 adults and compare Ibsrela with placebo over 26 weeks; initial results expected in H2 2027, per co

** ARDX's Ibsrela is already approved in the U.S. for irritable bowel syndrome with constipation; co aims to expand use to chronic idiopathic constipation

**  Most common side effects include diarrhea, gas, abdominal swelling and dizziness, co says

** Shares up ~15% in 2025

(Reporting by Sahil Pandey in Bengaluru)

((Sahil.Pandey@thomsonreuters.com))