Protagonist Therapeutics Inc PTGX:NASDAQ

Protagonist Therapeutics (PTGX) shares slumped 53% by Tuesday afternoon, a day after the biopharmaceutical company said a phase 2 study of its proposed treatment for inflammatory bowel disease failed to meet the primary endpoint for the higher-dose group.

The trial was meant to assess the efficacy and safety of PN-943 in patients with moderate-to-severe ulcerative colitis with two doses set at 150 milligrams and 450 milligrams.

Scott Plevy, therapeutic head of gastroenterology at Protagonist, said in a statement that the lower-dose arm offered "consistent evidence of clinical efficacy and safety." The company said PN-943 150 mg achieved 27.5% clinical remission and that plans for a registrational Phase 3 study based on twice-daily 150-mg dose of PN-943 are in progress.

Price: 9.22, Change: -9.58, Percent Change: -50.96