a second alzheimers drug proven to slow cognitive decline was a step closer to us approval on monday after clinical trial results published in a top journal confirmed its efficacy many experts have hailed the developments as major breakthroughs after years of little progress in the field although others have urged caution casting the benefits as modest while noting the high costs and risks of lifethreatening side effects in an analysis of nearly 1200 people with the early stages of alzheimers disease the drug called donanemab slowed the progression of symptoms by 35 percent over a period of 18 months compared to placebo according to a paper in the journal of the american medical association jama this was measured by the peoples results on cognitive tests and ability to carry out daily tasks the drug  taken as an intravenous injection every four weeks  is made by drugmaker eli lilly which said it expects regulatory action in the united states by the end of the year the new paper comes days after the us food and drug administration took a step that made leqembi produced by biogen and eisai available on the governmentrun insurance program for the elderly called medicare both work by targeting amyloid beta a protein that impairs cognition when it accumulates in the brain these firstgeneration drugs are by no means perfect but represent an important breakthrough giles hardingham interim director of the uk dementia research institute said in a statement at the same time however he said it was important to realize that alzheimers is a complex disease and amyloid beta was just one element in its genesis but in an editorial in jama that accompanied the new results eric widera of the university of california san francisco and colleagues said it was too early to declare the new medicines would be beneficial over the long run donanemab and leqembi also known as lecanemab do not cure alzheimers  rather they lead to slightly less worsening in patients they said the modest benefits would likely not be questioned by patients clinicians or payers if amyloid antibodies were low risk inexpensive and simple to administer however they are none of these the authors wrote even once 80 percent of the costs are offset by medicare patients will still need to pay costs totalling thousands of dollars out of pocket there were also three deaths in the studies of donanemab and leqembi that were probably caused by the treatments that lead to brain bleeds as the treatments move into real world use it will be essential to gather more data to find out if they continue to slow cognitive decline beyond 18 months  or if they backfire given that antiamyloid treatments also accelerate brain atrophy according to research moreover 96 percent of the patients in the donanemab trial were white while black and latino people have far higher rates of alzheimers meaning that key demographics were left understudied