(Reuters) -Fortress Biotech on Wednesday said the U.S. Food and Drug Administration declined to approve the drug it is developing with Indian drugmaker Zydus Lifesciences for treating a type of rare genetic disease in children.

The FDA in its “complete response letter” pointed to deficiencies at the facility where the drug, CUTX-101, is manufactured, the company said, adding that the regulator did not cite issues with efficacy and safety data.

The drug was being developed to treat Menkes disease, where patients are born without the ability to absorb copper from their diet. It is caused by mutations in a particular gene that is responsible for the transportation of copper throughout the body.

(Reporting by Padmanabhan Ananthan and Sneha S K in Bengaluru; Editing by Vijay Kishore)

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