Pfizer has agreed to buy the 89% of its long-time development partner Icagen that it does not already own for US$6 per share in order to expand its capabilities in the pain relief therapy area. The price offered by Pfizer, which values Icagen at US$56 M, has failed to meet the expectations of some Icagen shareholders, however. The two companies have been collaborating for the past 4 years on a pain programme focused on three sodium ion channels.