"We have now received a communication from US FDA that they have determined that Ranbaxy has forfeited its 180 days exclusivity for esomeprazole magnesium delayed-release capsules," the company said in a BSE filing.
AstraZeneca's top-selling drug Nexium contains esomeprazole and is used for treatment of certain stomach and oesophagus problems such as acid reflux and ulcers.
Ranbaxy said it "is disappointed with the result and is pursuing all available legal options to preserve its rights."
Earlier in a filing to BSE in November 2014, Ranbaxy had said that "FDA has rescinded the previously granted tentative approvals for Ranbaxy's ANDAs for esomeprazole magnesium delayed-release capsules, 20 mg and 40 mg and for Valganciclovir hydrochloride tablets USP, 450 mg."
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The USFDA had then said that its original decisions granting tentative approvals were in error because of the compliance status of the facilities referenced in the ANDAs at the time the tentative approvals were granted.
However the communication from US Food and Drug Administration (USFDA) had said that Ranbaxy's ANDAs of concern did not have any data integrity issues.
Also in November, the Indian drug maker had sued the USFDA over revoking an approval to sell generic versions of these two drugs -- Nexium and Valcyte -- in the US market.