Italy's Chiesi Farmaceutici has offered to buy the 40% stake in the USA's Cornerstone Therapeutics it does not already own.

Chiesi holds approximately 60% of the outstanding common stock of Cornerstone and chief executive Ugo Di Francesco has written to the latter's directors with a proposal to pay $6.40-$6.70 per share in cash for the remaining shares. This represents a 20%-25% premium over the closing price on February 15 and 24%-30% up on its 60-day average stock price. The offer would value Cornerstone at up to $177 million.

Mr Di Francesco says that Chiesi "has adequate liquidity available and excellent relationships with our banks, to effect an all-cash bid". He adds that during the last few months "we have conducted an extensive review of Cornerstone based on publicly-available information, our own deep experience in the pharmaceutical industry and consultations with our outside advisors".

Noting that Chiesi would not consider selling its stake, Mr Di Francesco said the proposal is subject to the completion of "certain confirmatory non-public due diligence". He concludes by saying that "Chiesi has devoted substantial time, effort and resources in preparing this proposal and is committed to working vigorously and expeditiously with you to complete a transaction".

Cornerstone, which focuses on specialty products for the hospital, also has a wholly-owned generics subsidiary called Aristos Pharmaceuticals. Last year, the firm suffered a setback after the US Food and Drug Administration rejected lixivaptan for the treatment of hyponatraemia in patients with congestive heart failure.

News of the offer has boosted Cornerstone's share price which climbed 19.5% to $6.55 in after-hours trading. The company noted that "no decisions have been made by the board of directors with respect to Chiesi's proposal".