Immediate action is needed to accelerate the development of drugs for dementia, the Prime Minister will say.
David Cameron will warn that more must be done to address a "market failure" on dementia research and drug development.
The comments come as health and finance experts gather in London to discuss the burden of dementia on people around the world.
Last year the UK used its presidency of the G8 to host an international summit on dementia, which ended with experts setting a global ambition to find a cure by 2025.
Today experts will gather for the first in a series of legacy events following the summit.
Mr Cameron is expected to pledge a new drive by the UK to discover new drugs and treatment for the condition.
The UK will look at how to bring forward specific proposals on patent extensions and how to give patients earlier access to new drugs, Mr Cameron will say.
"The truth is that dementia now stands alongside cancer as one of the greatest enemies of humanity," he will say.
"In the UK alone there are around 800,000 people living with dementia, worldwide that number is 40 million - and it is set to double every 20 years.
"We have to fight to cure it. I know some people will say that it's not possible, but we have seen with cancer what medicine can achieve.
"We first need to tackle head-on the market failure perilously undermining dementia research and drug development. And we need investment in research, greater collaboration, better incentives for taking new treatments to market and earlier access to innovative new treatments for patients.
"We need to join up the dots and create a big, bold global push to beat this.
"It will take years of work but we have shown with other diseases that we can make progress and we will do so again."
Health Secretary Jeremy Hunt is expected to add: "We owe it to the 44 million people living with dementia across the world to find new treatments for this cruel condition. But with the latest research from the London School of Economics now showing that a treatment to delay onset by three years could save the UK as much as £5 billion a year, we must redouble our efforts to respond to this moral and economic imperative.
"I hope today will help give dementia research in this country and around the world the important boost that's needed."
The news comes as the new world dementia envoy, Dr Dennis Gillings, warned that if global leaders do not incentivise businesses to invest in research the ambition set by the G8 dementia summit to find a cure for the disease by 2025 will not be met.
Dr Gillings said: "Dementia is a ticking bomb costing the global economy £350 billion and yet progress with research is achingly slow. Research must become more attractive to pharmaceuticals so they will invest and innovate.
"Just as the world came together in the fight against HIV/Aids, we need to free up regulation so that we can test ground-breaking new drugs, and examine whether the period for market exclusivity could be extended.
"Without this radical change, we won't make progress in the fight against dementia."