> ## Content Index
> Fetch the complete content index at: https://www.fdaweb.com/llms.txt
> Use this file to discover other available public pages before exploring further.

# Complete Response Letter for AstraZeneca NDA
- URL: https://www.fdaweb.com/complete-response-letter-for-astrazeneca-nda/
- Published: 2016-05-27T12:00:00.000Z
- Updated: 2026-09-14T21:05:58.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5135779

FDA has issued AstraZeneca a complete response letter (CRL) for its NDA for ZS-9 (sodium zirconium cyclosilicate), indicated for treating hyperkalemia (high potassium level in the blood serum). The letter identifies observations cited during a pre-approval manufacturing inspection, acknowledging recently-submitted data which it has yet to review, according to the company. The CRL does not request any new data, it says.   
  
ZS-9 is an insoluble, non-absorbed zirconium silicate with a three-dimensional crystalline lattice structure that was designed to preferentially trap potassium ions, AstraZeneca says. “The unique potassium selectivity of ZS-9 enables high in-vitro binding capacity for potassium ions even in the presence of other competing ions,” it says. The therapy has been studied in three double-blind, placebo-controlled trials, and in two ongoing 12-month open label studies in over 1,600 patients.