After years without a significant breakthrough in dementia research, a new Alzheimer’s drug called solanezumab could lead to a preventative treatment for the disease within five years. Researchers from the U.K. believe monthly injections could delay the onset of Alzheimer’s symptoms in people who could be at risk for developing the disease.

“Already half a million people are living with Alzheimer’s in the UK and that number is expected to soar,” said Dr. Eric Karran, director of research at Alzheimer’s Research U.K. “We urgently need a treatment that can halt the disease in its tracks, and the findings from these trials will help shape new discoveries in the future.”

According to the Alzheimer’s Association, one out of every three senior citizens will die as a result of a dementia-related condition. Alzheimer’s is considered the sixth leading cause of death in the U.S., and an estimated 5.2 million Americans suffer from the disease. Direct costs for Alzheimer’s care, including Medicaid, Medicare, and out-of-pocket expenses, was calculated at around $203 billion in 2013.

Although phase III clinical trials, dubbed EXPEDITION 1 and 2, did not reach their intended goals, researchers noticed a slowing of cognitive decline in patients affected mildly by dementia during a secondary analysis. The two trials, conducted by Eli Lilly & Company, show the drug’s promise as an effective treatment for mild Alzheimer’s symptoms, granting further investigation through 2016.

“While it’s very disappointing that this drug did not meet its primary goals in these phase 3 trials, there did appear to be some effect on cognitive decline in people with mild Alzheimer’s,” explained Dr. Karran. “We need to wait for the full trial data to be published before it is possible to assess the significance of these findings for patients.”

Clinical trials set for the U.S. will examine solanezumab’s effect on over 2,000 patients with mild Alzheimer’s disease even after monthly injections are discontinued. Alzheimer’s detection starts earlier than the onset of symptoms, which include memory loss, anxiety, and an inability to perform routine tasks. Monthly injections of the new drug given long before symptoms are detected could delay or even prevent the disease.

“Solanezumab aims to target amyloid, a hallmark protein involved in Alzheimer’s disease, which we now know starts to build in the brain years before symptoms appear,” Dr. Karran added. “Many scientists believe that drugs targeting amyloid will need to be given early. The fact that the best results were seen in people in the earlier stages of the disease appears to add weight to this theory.”

Scientists at Eli Lilly did warn about certain side effects that were noticed during initial trials such as lethargy, rash, malaise, and angina. The inaugural G8 dementia summit in London is scheduled for next week, where the top health advisors from the U.K., North America, and Asia will discuss the most significant breakthroughs in dementia research in recent years.

“I am full of hope that we are going to have a breakthrough in five years,” Dr. Karran said. “We need to get these therapies in early for them to have an effect. If we can just get efficacy with one drug we will understand so much more. If solanezumab was shown to work in mild Alzheimer’s disease, which is what is being investigated, then the pathway would be to take that earlier and earlier and earlier.”