Arthur Allen | (TNS) KFF Health News The first drug purporting to slow the advance of Alzheimer’s disease is likely to cost the U.S. health care system billions annually even as it remains out of reach for many of the lower-income seniors most likely to suffer from dementia. Medicare and Medicaid patients will make up 92% of the market for lecanemab, according to Eisai Co., which sells the drug under the brand name Leqembi.