US district court invalidates Megace patent

The US District Court for the District of Maryland has ruled that Taiwanese company TWi Pharmaceuticals’ generic version of Par Pharmaceuticals’ Megace ES drug does not infringe US patent 7,101,576.

Megace ES (megestrol acetate) is used in the treatment of appetite loss, severe malnutrition or unexplained significant weight loss in AIDS patients. Since 2005, Megace ES has made more than $600 million in net sales.

Par filed the case in September 2011 to stop TWi from launching a generic version of the drug, claiming it would infringe its patent.

On February 21, the court found the patent to be invalid on the grounds of obviousness. TWi may now launch a generic version of the drug pending approval from the US Food and Drug Administration (FDA).

“As the first applicant to file the ANDA [Abbreviated New Drug Application] for Megace ES, TWi may be entitled to 180-day generic market exclusivity,” TWi said.

In 1993, Bristol-Myers Squibb began marketing Megace OS, an oral suspension of the drug.

The FDA approved five generic versions of Megace OS, including one made by Par. By 2005, Par had the majority of the generic Megace OS medicine market, which generated $25 million in annual sales.

The ‘576 patent inventors, after experimenting with new formulations of the drug with a reduced particle size using biopharmaceutical company Alkermes’ patented NanoCrystal technology, found that the drug was much more easily absorbed when administered with food.

However, Par said this effect was a “significant weakness”, as the drug is aimed at patients suffering from low appetites and it is unlikely the drug can be administered “in a sufficiently fed state”.

The inventors later discovered that a new nanoparticulate formulation was absorbed well in both a fed and fasted state, and filed to protect the formulation in 2002.

The US Patent and Trademark Office rejected it several times, deeming the claimed invention obvious.

However, after it had amended the application to highlight the reduced difference in absorption between patients who had eaten and those who hadn’t, Par was granted the patent in 2006.

Around the same time, Par received FDA approval for its Megace ES, a formulation of the drug made of smaller molecules which, unlike its predecessor, can be taken outside mealtimes.

TWi’s ANDA for a generic version of this formulation is currently being reviewed by the FDA.

It told LSIPR that it is pleased that the judge ruled in its favour. Par did not respond to a request for comment.