Shares in Ardelyx Inc. have crashed after its tenapanor, under FDA review for managing phosphate levels in chronic kidney disease (CKD), ran into trouble with the regulator. The company said that the FDA has identified “deficiencies” in the data package, which prevent discussions about labeling and postmarketing commitments.

New top-line results from a phase III study of Ardelyx Inc.'s tenapanor – recently approved in irritable bowel syndrome – confirmed the drug can also help dialysis-dependent chronic kidney disease patients with hyperphosphatemia achieve reduced serum phosphorus levels vs. placebo.

It's been a busy September for Ardelyx Inc. so far. Less than two weeks after the Fremont, Calif-based company reported promising pivotal data for tenapanor in chronic kidney disease patients with hyperphosphatemia, the sodium hydrogen exchanger 2 (NHE3) inhibitor won FDA approval for use in irritable bowel syndrome with constipation (IBS-C).