GlaxoSmithKline (GSK) has agreed buy Stiefel Laboratories, the US skincare specialist, for $3.6 billion (£2.5 billion).

The Florida-based company, which is part-owned by Blackstone Group, the private equity house, will give GSK an enlarged dermatology business with annual sales of $1.5 billion.

Andrew Witty, the chief executive of GSK, said, “As part of our strategy to grow and diversify GSK’s business, we are continuing to make new investments through targeted acquisitions.

"This transaction will create a new world-leading, specialist dermatology business and re-energise our existing dermatology products.

"The addition of Stiefel’s broad portfolio will provide immediate new revenue flows to GSK with significant opportunities to enhance growth through leveraging our existing global commercial infrastructure and manufacturing capability.”

GSK is paying $2.9 billion in cash and will assume $400 million of Stiefel’s net debt.

A potential further $300 million cash payment is contingent on Stiefel’s future performance.

GSK’s existing prescription dermatological products will be combined with Stiefel’s and the new business will operate under the Stiefel identity within GSK

The deal is the latest in a wave of takeovers among big pharmaceutical companies, which are looking for new sources of sales growth as some of their biggest drugs face competition from cheaper generics.

Already this year, Pfizer has agreed to pay $68 billion acquisition for Wyeth and Merck is buying Schering-Plough for $41 billion.

Mr Witty, GSK’s new chief executive, has insisted that the company does not need to do blockbuster deals, and has so far concentrated on smaller, bolt-on acquisitions, such as that unveiled this morning.

The purchase of Stiefel marks his fifth bolt-on since taking office last June.

Last week Glaxo struck an alliance with Pfizer to combine their HIV businesses.

That deal is expected to give Glaxo access to Pfizer's more-promising profile of AIDS drugs in development, and provide opportunities for cutting costs.

Glaxo will initially own 85 per cent of the venture, which could be valued at more than £4 billion.

Stiefel products treat a wide range of skin ailments, such as the DUAC acne gel and OLUX, an anti-itch foam for the scalp.

It has sales of about $1 billion, 4,000 employees and has expanded in recent years through a string of acquisitions, including the $600 million purchase of Connetics in 2006.

The company has been controlled for more than 160 years by the founding Stiefel family, although Blackstone invested $500 million in Stiefel in 2007 for a large minority stake.

Shares in GSK, which is valued at £54 billion, were unchanged at £10.37 in early trading.

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