Ardelyx Inc. started an underwritten public offering of up to $50 million of its common shares.

The Fremont, Calif.-based Ardelyx plans to grant the underwriters an option to buy up to an additional $7.5 million of shares.

Ardelyx currently expects to use its existing cash, cash equivalents and short-term investments, and the net proceeds of the offering to support its clinical development and pre-commercialization efforts for tenapanor for the treatment of hyperphosphatemia in patients with end-stage renal disease who are on dialysis.

Hyperphosphatemia is characterized by higher than normal levels of phosphate in the blood.

Ardelyx may also use the net proceeds for its manufacturing efforts for tenapanor and research and development of its RDX013 program, for hyperkalemia. The company also plans to use the net proceeds for the preparation and submission of a new drug application for tenapanor for irritable bowel syndrome with constipation and for general corporate purposes and working capital.

Jefferies and Leerink Partners are acting as joint book-running managers for the offering.