Shares of Tenax Therapeutics and Sionna Therapeutics tumbled Monday after the biotechs revealed separate late-stage trial failures.

Tenax stock fell nearly 90% after a Phase 3 trial of its experimental heart-failure pill failed to help patients walk farther than those on a placebo. The trial measured how far patients could walk in six minutes-a standard test for heart failure treatments. A second trial goal measuring patient-reported symptoms also came up short.

Meanwhile, shares of Sionna dropped 92% after a trial of its experimental cystic fibrosis drug missed its main goal. The drug, added to a treatment developed by Vertex Pharmaceuticals, was meant to help patients' lungs clear mucus more effectively, measured by a drop in sweat chloride levels. The company said it wouldn't continue development of the drug as an add-on treatment.