Patients taking the medicine, called suvorexant, fell asleep faster and spent less time awake at night than those on a placebo, according to the Merck-sponsored studies. The company plans to seek U.S. regulatory approval of the pill this year.

About 70 million, or one-third of American adults, have trouble falling or staying asleep, according to the American Psychiatric Association. Suvorexant would compete with drugs such as Ambien and Lunesta in a market expected to reach $3.5 billion by 2019, according to research firm Datamonitor. If cleared for sale, suvorexant would be the first of a novel class of medicines designed to aid in sleep by turning down the systems in the brain that keep a person awake.

“The therapy of insomnia has changed from trying to augment the power of the sleep system to trying to inhibit the wake system,” said Thomas Roth, director of the Sleep Disorders and Research Center at Henry Ford Health System in Detroit, in an interview. Roth worked with Merck on the study and consults with other drugmakers on insomnia therapies.

The Whitehouse Station, New Jersey-based drugmaker released three-month data from yearlong studies of about 1,000 people each, showing that patients fell asleep faster when given the drug than when not taking it, or when on a placebo. They also stayed asleep longer without waking up when taking the drug, Merck said in a statement describing the data.

Merck fell less than 1 percent to $38.58 at 9:38 a.m. New York time.

Side Effects

The most reported side effect was sleepiness upon waking up, seen in 10.7 percent of patients in one trial and 10.3 percent in the second trial; and headaches, seen in 6.8 percent of patients in one trial and 7.5 percent in the other, according to Merck. Suvorexant met all of both studies’ goals except for a single measurement in one of the trials that found the time to fall asleep didn’t differ significantly between those who took the drug and those who got a placebo.

In an earlier study, patients also did better at a driving test the next day, staying in their lane more than patients on eszopiclone, the generic name for Lunesta.

The data was released today at the Annual Meeting of the Associated Professional Sleep Societies in Boston. Suvorexant is in the last of three stages of clinical trials before U.S. regulators decide on approving the drug for sale.

Potential Benefits

The drug may be beneficial in patients with addiction problems on current sleep drugs, or who suffer from sleep apnea, where the body briefly stops breathing, Roth said. Current sleep therapies can suppress respiration. Clinicians are also looking for therapies that let patients wake easier and don’t cause dizziness and falls, he said.

“We want drugs that not only improve sleep but the comorbid conditions associated with sleep” problems, Roth said. “We think that it has potential.”

More study of the medicines must be done before those sorts of benefits over existing drugs can be proven, he said.

Merck will also have to gain approval from the Drug Enforcement Agency, because the pill is classified as a controlled substance. That will take another six to nine months after the FDA rules, according to the company.

Subdue Receptors

Ambien and Lunesta, the current best-selling insomnia medications according to data compiled by Bloomberg, essentially subdue GABA receptors, which are spread throughout the central nervous system, putting people to sleep and acting as a muscle relaxant, anxiety reducer and anti-convulsant. Merck’s drug works by suppressing orexin receptors, which are only found in the hypothalamus region of the brain, according to Merck. The orexin receptors control wakefulness.

GlaxoSmithKline Plc, based in London, has an experimental orexin blocker that is in the second of three phases of clinical development.

Merck estimates that 18 million people in the U.S. currently get treatment for some form of insomnia, which the National Institutes of Health defines as trouble either going to sleep of falling asleep.