AstraZeneca said it is buying licensing and research rights to an Alzheimer’s drug, marking the fourth agreement the company has inked in the last month.AstraZeneca said it agreed to pay up to $300 million to Targacept for rights to help develop and market that firm’s phase II compound TC-1734, which is being developed to treat Alzheimer’s disease and schizophrenia.The four-year deal also hands AstraZeneca global rights for the development and commercialization of any compounds that arise out of the research collaboration, namely drugs for treating cognitive decline.The agreement caps a busy month that also included AstraZeneca’s pact worth up to $338 million to develop CytoFab, a treatment for severe infections, with UK biotech company Protherics PLC; a potential $1 billion licensing agreement for an investigational oral drug for the treatment of atherosclerosis from Alpharetta, Ga.-based AtheroGenics; and last week’s $210 million purchase of privately owned UK biotech firm KuDOS Pharmaceuticals, in which AZ acquired promising Phase I cancer compound KU59436.Analysts haven’t ruled out further deals in the coming months.Under the Targacept agreement, Winston-Salem, N.C.-based Targacept, which specializes in drugs for CNS disorders, receives an initial payment of $10 million and could get additional milestone and research-support payments and royalties dependent on sales of TC-1734.