 Pfizer Inc. PFE, -1.18 has agreed to buy Global Blood Therapeutics Inc. s :gbt in a deal valued at 5.4 billion, the companies said Monday, confirming a report by the Wall Street Journal. Pfizer will pay 68.50 a share in cash for Global Blood Therapeutics, which has one of few approved treatments for sickle-cell disease, a painful inherited blood disorder that most affects people of African, Middle Eastern and South Asian descent. 