The U.S. Food and Drug Administration did not approve Sanofi and Lexicon Pharmaceuticals Inc.'s experimental type 1 diabetes drug Zynquista.
Lexicon's shares fell 24.18% to $6.02 as of 3:10 p.m. ET on March 22 following the news. Sanofi's stock was down 2.69% to $44.21.
Zynquista is a dual inhibitor of both sodium-glucose co-transporter 1, or SGLT1, and sodium-glucose co-transporter 2, or SGLT2.
In January, a panel of outside expert advisers to the FDA was split over whether the drug's data suggested that its benefits outweighed its risks.
Zynquista had presented with an adverse event called diabetic ketoacidosis, or DKA, which has been historically associated with SGLT2 inhibitors and is potentially life-threatening. But the drug also showed a significant increase in glycemic control, according to experts at the January meeting.
The companies argued at the time that more innovative drug like Zynquista would benefit the type 1 diabetes population.
France's Sanofi and Woodlands, Tex.-based Lexicon said in a release that they plan to work closely with the FDA to determine how to proceed with the drug.