Despite the anticipated approval of breast cancer drug Tykerb (lapatinib) tomorrow, analysts at Goldman Sachs are warning that patent expiry of four products with combined sales of £2.4bn (€3.5bn), coupled with slow pipeline progression, could result in the pharma heavyweight underperforming.

The statement comes as a further blow to GSK after analysts at Morgan Stanley also criticised the company's pipeline last week.

"That GSK has improved its pipeline productivity in terms of number of drugs in the pipeline is not open to question; the debate in our view remains whether the quantity can be sufficiently translated into quality launched products," said Dr John Murphy at Goldman Sachs, in a note to investors.

"Evidence of improving late-stage productivity is key in our view."

Dr Murphy did concede that GSK is much more open about its pipeline than other pharma companies and that he expected the company to launch nine blockbuster drugs by 2015 - despite the launch of only one so far this decade.

He added that expectations for the company's new drugs could prove to be too high. Although Tykerb is due to be approved as a second and third line breast cancer therapy, the drug is also in Phase III trials as a first line treatment. Dr Murphy pointed out that positive results could boost shares in the future.

According to Dr Murphy, the company is also facing uncertainty over its future strategy in light of the fact that CEO JP Garnier is stepping down in May 2008.

Dr Murphy predicts GSK's share price will stay around the £14.26 area over the course of 2007 although shares are currently 0.6 per cent higher at £14.35.