As was rumoured, Pfizer is buying the stake it did not already hold in Icagen, as part of an expansion of its pain franchise.

The US giant currently owns 11% of Icagen and will acquire the remaining 8.3 million shares at $6.00 each. The aggregate transaction value, including the shares currently owned by Pfizer, is $56 million.

The firms have been partners for some time; in 2007, they entered into a collaboration centred around compounds that modify three specific sodium ion channels and could be new treatments for pain and related disorders. These channels are important in the generation of electrical signals in nerve fibres that "mediate the initiation, transmission and sensation of pain", Pfizer noted, and by selectively targeting them, the companies are seeking to develop effective treatments for serious pain disorders with fewer side effects.

Ruth McKernan, head of Pfizer’s pain and sensory disorders and regenerative medicine unit, known as Neusentis, said that “Icagen’s capabilities and core ion channel technology will help to further expand Pfizer’s position in the pain relief disease area and our ability to develop potential first-in-industry drugs".

Shares in Icagen have shot up over 200% since the end of June, when the companies revealed they were discussing a "strategic transaction". Pfizer's offer is actually a 22% discount from Icagen's shares on Tuesday and its stock fell 23% on the news.

Some analysts are surprised at the price, after previous estimates valued Icagen at around $8 per share. A number of legal firms in the USA have already announced investigations on behalf of the latter's shareholders concerning potential unfairness and potential conflicts of interests among Icagen's board members.

AMAG, Allos to merge

On a busy day for mergers across the pond, AMAG Pharmaceuticals and Allos Therapeutics have announced an all-stock link-up with a value of $686 million.

The transaction is expected to result in annual cost savings of $55-$60 million in the first fiscal year after closing and one-time costs associated with the merger are expected to total $35-$38 million. The combined company, which will be renamed, will have two commercial products in the USA - AMAG’s Feraheme (ferumoxytol) for the treatment of iron deficiency anaemia  in adults with chronic kidney disease and Allos’ Folotyn (pralatrexate) for patients with relapsed or refractory peripheral T-cell lymphoma.

Allergan buys Vicept

Last but not least, Allergan is buying privately-held dermatology company Vicept Therapeutics.

The maker of Botox (botulinum toxin type A) is paying $75 million cash up-front, plus $200 million in payments depending on the progress of Vicept's V-101, a topical cream for the treatment of the erythema (redness) associated with rosacea. Two Phase II studies have demonstrated the clinical potential V-101 for a dermatological problem for which there currently is no approved therapy.

Vicept was only founded in August 2009 and raised $16 million in Series A backing from Vivo Ventures, Sofinnova Ventures and Fidelity Biosciences.