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Arrowhead Pharmaceuticals Pauses Test of its Cystic Fibrosis Treatment

Arrowhead's move comes after a toxicology study in rats contained unexpected signals of local lung inflammation, the company says.
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Arrowhead Pharmaceuticals  (ARWR)  shares plummeted Friday after it paused tests of its drug for treating cystic fibrosis.

Arrowhead voluntarily paused a Phase 1/2 clinical study of ARO-ENaC, the company’s investigational RNA interference therapeutic.

That came “after receiving a preliminary update from an ongoing chronic toxicology study in rats that contained unexpected signals of local lung inflammation,” Arrowhead said in a statement.

“The company has instructed investigators to pause new screening, enrollment, and any further dosing of investigational ARO-ENaC pending additional data from the ongoing chronic rat toxicology study and an additional ongoing chronic primate toxicology study,” Arrowhead said.

Arrowhead recently traded at $64.10, down 24.55%. The stock has fallen 4% over the past six months.

“We await additional information from ongoing nonclinical toxicology studies,” said Javier San Martin, Arrowhead’s chief medical officer.

“After we receive the full data from these studies, we will assess whether there is an acceptable path forward for further clinical investigation,” San Martin said.