Shares of Ardelyx (ARDX 3.75%) were up 13.2% as of 2:30 p.m. ET Wednesday after the U.S. Food and Drug Administration (FDA) approved its first-in-class chronic kidney disease drug. In a press release issued Tuesday after the market close, the biopharmaceuticals company announced the FDA has approved Xphozah (tenapanor).

Xphozah is a single tablet taken twice daily as an add-on therapy to reduce serum phosphorus in adults with chronic kidney disease on dialysis. Candidate patients will either have an inadequate response to phosphate binders or are intolerant of phosphate binder therapy. The drug now stands tall as the market's first and only phosphate absorption inhibitor.

Why Xphozah's FDA approval is a big deal

"The approval of Xphozah is an important milestone for patients on dialysis, their families, and the nephrology care community, as it represents a new mechanism and new option for patients who, despite treatment with phosphate binders, continue to have elevated phosphorus," stated Ardelyx CEO Mike Raab. "It is also a significant accomplishment for everyone at Ardelyx."

Stanford Professor of Medicine Dr. Glenn Chertow added that management of hyperphosphatemia -- or high phosphorus -- "has been a persistent clinical challenge," particularly as most patients receiving maintenance dialysis have had trouble consistently achieving target phosphate concentrations even when treated with phosphate binders. As a phosphate absorption inhibitor, Xphozah will offer an important new treatment option for these patients.

On expanding access and affordability for Xphozah

In conjunction with the FDA-approval news, Ardelyx announced an amendment to its debt financing with SLR Capital Partners to provide an additional $50 million of committed capital. The non-dilutive funds will be used at Ardelyx's discretion (with SLR's approval) to bolster its balance sheet and support the commercialization of both of the company's FDA-approved products, Xphozah and Ibsrela. The latter received FDA approval to treat irritable bowel syndrome and constipation (IBS-C) in late 2019. 

The company says it will integrate Xphozah into its established patient services program, ArdelyxAssist, which provides access and affordability support for patients through integration into medical office work processes and connectivity with healthcare providers. 

As for investors, this is massive news that's been years in the making. With its growth runway now significantly expanded and commercialization imminent for Xphozah alongside Ibsrela, it's no surprise to see shares of this leading biopharma stock soaring today.