(Reuters) - Drug developer Axovant Sciences Ltd said it would stop testing its lead drug in Alzheimer’s after it failed to meet the main goals of a late-stage trial, underlining the challenges in developing treatments for the memory-robbing disease.

The company’s shares tumbled 74.7 percent to a record low of $6.13 in morning trading on Tuesday.

Axovant’s once-daily oral drug, intepirdine, belongs to a class of drugs called 5-HT6 antagonist, which works by blocking the 5-HT6 receptor to help release acetylcholine, a neurotransmitter needed for normal cognition.

The latest failure raised serious doubts about the mechanism’s potential as a treatment for Alzheimer’s, the most common form of dementia that affects about 5.5 million people in the United States.

In February, Denmark-based Lundbeck said late-stage trials testing its 5-HT6 antagonist-based drug failed to meet their main goals.

“Following a slew of failures with other 5-HT6 receptor antagonists, Axovant’s intepirdine put the nail in the coffin for the mechanism in Alzheimer’s disease,” Baird analyst Brian Skorney wrote in a client note.

The failure is a “death blow” to his hypothesis around Axovant, Skorney said.

Another path to treat Alzheimer’s by targeting beta-amyloid protein - long thought to be an underlying cause of the disease - has also suffered setbacks.

Eli Lilly and Co last year said its experimental Alzheimer’s drug failed a key late-stage trial.

A slew of drugmakers, including Biogen Inc, ProMIS Neurosciences and Roche’s Genentech, are developing drugs that directly target beta-amyloid protein in the blood and brain.

Biogen’s aducanumab and Genentech’s Crenezumab are being evaluated in late-stage studies, while ProMIS’ therapy is in pre-clinical trials.

Axovant said on a conference call that it would shift its focus to other trials.

The company is testing intepirdine to treat dementia with Lewy bodies and gait and balance impairments in dementia.

Data from a mid-stage trial testing intepirdine in patients with dementia with Lewy bodies will be reported by the year-end, the company said.

Deaths from Alzheimer’s jumped more than 50 percent from 1999 to 2014, and the rates are expected to rise, reflecting the nation’s aging population and increasing life expectancy, according to American researchers.

Intepirdine failed to demonstrate statistically significant improvement in cognitive ability and showed no difference in daily living activities, compared with a placebo, in patients with mild-to-moderate Alzheimer’s who were receiving background therapy.

The company’s shares had almost doubled in value this year.