Once partners with the now-embattled Purdue on an insomnia treatment, Eisai bought a full stake in the drug earlier this year––taking on its full development and marketing costs, too. Now, with an FDA approval in hand, Eisai is scaling up to support that drug's pending launch. The FDA approved Eisai's Dayvigo (lemborexant) on Friday as a treatment for insomnia characterized by difficulties with sleep onset or maintenance. Due to the FDA recommending the drug's classification as a controlled substance, Eisai plans to launch once Dayvigo receives a Drug Enforcement Administration schedule in roughly 90 days, the company said in a release. Eisai took full ownership of Dayvigo in May after it bought out Purdue's stake in the drug in 2015. The drug is an orexin receptor antagonist that works by targeting the wake center of the brain, according to Eisai CEO and president of its global neurology business Ivan Cheung, who called the approval "very exciting." "It’s a large opportunity, and the question now is differentiation," Cheung said. "There’s a lot of unmet need as far as efficacy and safety." RELATED: Eisai buys Purdue stake in insomnia drug as PDUFA date nears The drug will come with a stiff warning label, including for daytime impairment, worsening of suicidal ideations and sleep paralysis. The FDA based its approval on two phase 3 trials showing Dayvigo topped placebo in terms of patients' sleep onset as well as time to uninterrupted sleep. In both trials, patients treated with Dayvigo did not experience insomnia "rebounding"––when even worse symptoms return once treatment is stopped––to a significant degree, Eisai said. In separate safety studies to determine nighttime and next-day memory and activity, Dayvigo was more of a mixed bag. Both patients on high doses and those on low doses of the drug showed no significant improvement in night- and daytime postural stability or memory. In fact, patients on the high dose of 10 milligrams posted impaired next-day driving over placebo, and patients on both doses showed had trouble standing upright after four hours of sleep. When Dayvigo launches post-DEA waiting period, it'll follow Merck's Belsomra, which hit the scene in 2014, on to the market. Eisai plans to roll out a team of 250 sales professionals to promote the drug, and the company's physician outreach team will be backed by a digital sales team tasked with consumer outreach and feedback, Cheung said. "It’s not just about sending our specialists out there in the field, but also having that additional platform proactively reaching out and being able to respond to all inquiries," Cheung said. Dayvigo will enter a market that's "generics heavy," with a need to distinguish itself to both physicians and consumers, said Tushar Patel, Eisai's executive director and global lead of sleep-wake disorders in the neurology business group. "What’s going to be really important for us to communicate to doctors is, 'What are the benefits that we deliver, and how do we deliver that from a safety standpoint?'" Patel said."That’s going to be something that is central in terms of our messaging in terms of our prescribers." With an approval now in hand, Eisai is "actively exploring" a phase 3 trial for irregular sleep-wake rhythm disorder in Alzheimer's patients after a phase 2 study demonstrated proof of concept that the drug could be effective in that population, Cheung said. Eisai is currently working with regulators to determine "appropriate scales" for a clinical trial, Patel said.