A NORTH Hampshire firm that grew to become the UK’s third largest pharmaceutical company is set to merge with an American rival.

Shire plc, which has a large base on Hampshire International Business Park, in Chineham, is supporting a takeover offer from AbbVie.

The Chicago-based firm has just upped its offer to £53.20 per share, which the board of Shire will be recommending to its shareholders.

AbbVie first started making bids for the Dublin-headquartered company in May. It is believed that AbbVie will shift the domicile of the combined company to the UK, allowing it to dramatically reduce its tax bill and diversify its portfolio. This is a tactic known as inversion.

The new offer follows negotiations to sell Shire for £31.4billion to AbbVie which is a specialist in treating arthritis.

The new offer will see Shire shareholders owning around 25 per cent of the combined firm.

Shire, which is primarily known for making drugs to treat rare diseases and employs around 400 people in Basingstoke, said in a statement: “The board of Shire has indicated to AbbVie that it would be willing to recommend an offer at the level of the revised proposal to Shire shareholders, subject to satisfactory resolution of the other terms of the offer.”

On Tuesday, Shire’s shares closed at £48.65 per share on the FTSE 100.

The company is also listed on New York’s NASDAQ and the Toronto Stock Exchange.

Shire was founded in 1986 and had its first office above a wine shop in Overton. It later moved to two converted barns in Andover, before moving to Basingstoke in 2001. The company changed its tax base to Ireland in 2008.

Shire sells a range of specialist products, including Reminyl used for the treatment of Alzheimer’s and Mezavant, used for ulcerative colitis and generates most of its business in the United States.