A phase 2b clinical trial of Arena Pharmaceuticals’ olorinab has missed its primary endpoint. The cannabinoid receptor 2 agonist failed to reduce abdominal pain in the overall population of irritable bowel syndrome (IBS) patients, but Arena pointed to a subgroup analysis as evidence of efficacy.
Arena made olorinab, then known as APD371, a key part of its future in 2017 when it offloaded the rights to its commercial weight-loss drug Belviq. A small phase 2a linked olorinab to reductions in pain in Crohn’s disease patients in 2018, leading Arena to start a larger phase 2b in IBS patients the next year.
Now, Arena has shared top-line findings from the 273-subject IBS study. The trial found olorinab was no better than placebo at reducing average abdominal pain scores at any of the three tested doses. Participants took one capsule three times a day for 12 weeks.
The failure in the overall population left Arena looking to a pre-specified subgroup analysis for signs the drug works. In patients with moderate to severe pain at baseline, the 50-mg dose was linked to a 1.64 point reduction in pain scores compared to placebo. Arena said the difference was statistically significant and clinically meaningful.
Physicians quoted by Arena called the results promising, but the company’s long-term plans for the drug candidate are unclear. “We expect to evaluate possible strategic options for olorinab, while maintaining our commitment to the GI community and remaining focused on advancing our clinical programs for etrasimod in ulcerative colitis, Crohn’s disease and eosinophilic esophagitis,” Arena CEO Amit Munshi said in a statement.
While the future of olorinab is uncertain, Arena has made progress with the other experimental medicines it hitched its future to back in 2017. United Therapeutics paid $800 million to license pulmonary arterial hypertension drug ralinepag, and etrasimod has advanced into a broad phase 3 program.
Those successes have helped send Arena’s stock up more than 400% since it sold the rights to Belviq at the start of 2017. The failure of olorinab put a small dent in those gains, sending shares in Arena down 9% after-hours.