Sanofi will terminate its 19-month-old, up-to-$198 million collaboration with Ardelyx to develop its portfolio of NaP2b inhibitors effective September 30, and will return rights for the compounds to the biopharma.

There was no payment associated with termination and the return of rights, Ardelyx said.

Ardelyx licensed its phosphate transport NaP2b inhibitor program for kidney disease to Sanofi under an option and license agreement beginning in February 2014. Under that agreement, Ardelyx granted Sanofi an exclusive worldwide license to conduct research using Ardelyx's small molecule NaP2b inhibitors (also called RDX002) for the treatment of hyperphosphatemia in patients with end-stage renal disease (ESRD), also known as chronic renal failure.

The agreement also gave Sanofi the right to exercise its option to obtain an exclusive license to develop, manufacture, and commercialize Ardelyx's NaP2b inhibitors if a development candidate were identified within a defined period.

Ardelyx said yesterday it received $1.25 million upfront from Sanofi upon execution of the agreement to develop its NaP2b inhibitors program, which the companies said last year covered NaPi2b, Npt2b, and SLC34A2. All are in early-stage research.

“We are pleased to regain control over research on NaP2b and look forward to leveraging our knowledge of these inhibitors and their effect on phosphate management as we seek to further understand the mechanisms around phosphate lowering with tenapanor,” Jeremy Caldwell, Ph.D., Ardelyx evp and CSO, said in a statement.

Tenapanor (also known as AZD1722 and RDX5791) is Ardelyx’ lead product candidate, a Phase III-ready non-systemic small molecule inhibitor of NHE3, a sodium transporter present on the epithelia surface of the GI tract. Tenapanor is under development for the treatment of hyperphosphatemia in chronic kidney disease patients on dialysis, as well as constipation-predominant irritable bowel syndrome (IBS-C).

According to Ardelyx, tenapanor has consistently demonstrated the ability to reduce the absorption of dietary sodium and phosphorus, both of which are widely recognized as key factors in the progression of kidney disease. Ardelyx developed tenapanor using its own drug discovery and design platform.

“Importantly, we can now deepen our understanding of NaP2b effects utilizing our proprietary research capabilities, which was not fully possible under the terms of the Sanofi agreement,” Dr. Caldwell added.

Added Ardelyx president and CEO Mike Raab: “The return of the research portfolio of NaP2b inhibitors allows Ardelyx to expand its knowledge of all aspects of phosphate management, complementing tenapanor, which is being evaluated in mid-stage clinical trials for the treatment of hyperphosphatemia in ESRD patients.”

In addition to tenapanor, Ardelyx is developing RDX022, a non-absorbed polymer for the treatment of hyperkalemia in kidney and heart disease patients. The company said it is also advancing several research programs focused in gastrointestinal and cardio-renal diseases.

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