AstraZeneca PLC (AZN) is facing a fresh setback for its key blood drug, ZS-9 (sodium zirconium cyclosilicate), as the U.S. Food And Drug Administration (FDA) has issued a complete response letter (CRL) indicating that the drug application is rejected. A complete response letter is issued by the FDA to communicate to a drug maker that its application to market a drug will not be approved in its present form. It also means that the review of the application by the FDA has been completed. (See also, AstraZeneca's Symbicort Gets Pediatric Exclusivity.)

ZS-9 drug is intended as a therapy for treating hyperkalemia, the condition of having higher than normal levels of potassium in the blood serum. The condition is common among patients with chronic kidney disease and/or chronic heart failure. The disease is difficult to diagnose, and the disorder can cause serious health issues, including sudden death from cardiac arrhythmias (irregular heartbeats).

Second CRL for the High-Cost Acquisition

FDA has issued the CRL following the inspection of the concerned manufacturing facility in Texas, and AstraZeneca confirmed that the CRL does not require the generation of any new clinical data. While precise details are not available, the updates indicate that the plant may be having certain manufacturing deficiencies or inadequate controls.

This is the second CRL received by the London, UK-based drug maker from the FDA for the key drug. It was slapped with a similar CRL in May last year.

AstraZeneca paid $2.7 billion in late 2015 to buy ZS Pharma for its promising drug ZS-9. The acquisition has turned out to be a bad gamble for AstraZeneca, as the “promising, best-in-class” hyperkalemia drug, which was then touted to have peak sales of $1 billion, has failed to pass the regulatory hurdle.

The recent failure will mean AstraZeneca will have to wait to challenge Relypsa Inc.’s (RLYP) Veltassa (patiromer), another hyperkalemia drug which secured FDA approval in October 2015.

However, the drug has secured a positive opinion from the Committee for Medicinal Products for Human Use in the European Union in February, which may lead to its approval in the large European markets in near future. (See also, AstraZeneca Ovarian Cancer Drug Succeeds in Trial.)

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