Ardelyx scraps PhIII drug after researchers raise a safety issue for hyperkalemia patients

The roller coaster ride at Ardelyx is continuing today with news that one of their late-stage assets is being scrapped.

With their lead drug tenapanor being slowly guided to regulators and a hoped-for market showdown for irritable bowel syndrome, Ardelyx $ARDX reported that it has decided to scuttle its Phase III program for RDX7675 in patients with hyperkalemia after tracking a safety issue — drug-related reduction in serum bicarbonate, which can trigger a decision to stop treatment — which essentially blew up its plans to market this treatment for chronic cases.

The setback, though, didn’t seem to faze investors. Ardelyx shares, which have followed a neck-snapping pace of ups and downs, are up a bit this morning. And Leerink’s Seamus Fernandez tells us why:

“(O)ur recent initiation and enthusiasm for ARDX is geared almost entirely toward the oppt’y for tenapanor in hyperphosphatemia. Mgmt expects the termination of ‘7675 to result in cash savings of ~$40M and believes the company now has cash runway into 2019.”

Mike Raab

“The goal for RDX7675 was to develop a palatable product that could be taken chronically to address an important medical need for patients with hyperkalemia (high blood levels of potassium). We are pleased by the activity observed; however, the unanticipated bicarbonate side effect creates a barrier for RDX7675, which we believe could limit its chronic use,” said Mike Raab, chief executive officer of Fremont, CA-based Ardelyx, in a statement.

The biotech has plenty left to do. There’s an early-stage therapy for hyperkalemia called RDX013 that will be moved up. And the next Phase III program for tenapanor for hyperphosphatemia in end-stage renal disease patients on dialysis is being enrolled, with a control arm being added after regulators told them they needed more safety data. An application for tenapanor as a new treatment for IBS-C is also in the works.

When Ardelyx execs rolled out their first round of Phase III data on their IBS drug tenapanor, they were confident that they were playing a winning hand, with statistically significant results in beating out a placebo for easing abdominal pain and increasing bowel movements.

Instead they were crushed after some analysts could barely stifle a yawn over perfectly approvable data that didn’t measure up so well against new data from a rival drug from Synergy $SGYP called Trulance as well as Ironwood’s franchise $IRWD drug Linzess. Then, a few weeks ago, the stock rocketed up on better comparison data.

There’s never a dull moment at Ardelyx.

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