Pharmaceutical giant GlaxoSmithKline Plc said today that a US judge had ruled one patent related to its top-selling anti-depressant Paxil was invalid, but supported another.
Europe's biggest drugmaker said it is to stick to its full-year profits targets, despite the split ruling.
GSK said the judge had ruled in its favour on another and split the decision on the remaining two disputed patents, holding some claims in the patents invalid, but denying Apotex's motions on others.
GlaxoSmithKline shares were little changed, standing up 0.27 per cent at 11.24 pence soon after the open. GlaxoSmithKline said it would seek an appeal against the ruling that one patent was invalid.
"GSK continues to believe there are significant hurdles that prevent launch of a generic Paxil product. Accordingly, GSK's published earnings guidance for 2002 and 2003 remains as previously stated," the firm said in a statement.
The dispute over the remaining three patents will go forward to a court case. Drugmakers across the world are facing threats to blockbuster medicines as patents expire.
Normally viewed as defensive plays in times of economic uncertainty, they have had a tough year as key medicines have come off patent, regulators have taken a tough line on new products, European markets have cooled and governments have stepped up the pressure to cut prices.
Paxil - which belongs to the same class of antidepressants as Prozac - has been a huge commercial success for GSK. The biggest single market for the product is the US. Many industry analysts expect generic versions of the medicine to reach the market there in 2004.