The US Patent and Trademark Office (USPTO) has rejected Pfizer's application for re-issue of the Lipitor patent, allowing Ranbaxy Laboratories to go ahead with the proposed launch of a generic version of the cholestrol-lowering drug in the US in March 2010.

The rejection by the patent office would allow Ranbaxy to advance the launch of its generic version of Liptor -  atorvastatin - in the US market by 15 months, to March 2010, with 180-day exclusive marketing rights.

Pfizer and Ranbaxy are engaged in a patent war across markets for Lipitor, the world's largest selling drug, with over $12 billion in worldwide sales last year. 

The Lipitor patent, originally scheduled to expire in June 2011, was invalidated in 2006 by a US federal appeals court after Ranbaxy challenged the patent.

While the current ruling is still not a final decision, the Patent Office has clearly rejected Pfizer's application for a Liptor patent. 

The PTO decision can be appealed further. But there seem to be more complications for Pfizer, which had reviewed its application several times. Pfizer may still go ahead and apply again.

Pfizer had told its investors that it would be ring-fencing Lipitor and would be looking to protect its patents.

Ranbaxy, meanwhile, received final approval from the US Food and Drug Administration (USFDA) to manufacture and market cetirizine hydrochloride oral solution (allergy) and children's cetirizine hydrochloride oral solution, 1 mg/ml (OTC).

USFDA has determined the Ohm formulation to be bio-equivalent and having the same therapeutic effect as that of the listed drug Children's Zyrtec Oral Solution (for allergy) and Children's Zyrtec Oral Solution (Hives-Relief), 1mg/ml. of McNeil Consumer Healthcare.

 Cetirizine Hydrochloride Syrup has total annual market sales of $157 million.

Cetirizine Hydrochloride is indicated for the temporary relief of running nose, sneezing, itching of the nose or throat, and itchy, watery eyes due to hay fever or other upper respiratory allergies.