US FDA delays Merck & Co's insomnia drug suvorexant, issuing CRL

There was disappointment for US drug giant Merck & Co (NYSE: MRK), which said that it has received a complete response letter from the US Food and Drug Administration regarding the New Drug Application for the firm’s suvorexant, an investigational medicine for the treatment of insomnia.

In the CRL, the FDA advised Merck that:

• the efficacy of suvorexant has been established at doses of 10mg to 40mg in elderly and non-elderly adult patients;
• 10mg should be the starting dose for most patients, and must be available before suvorexant can be approved;
• 15mg and 20mg doses would be appropriate in patients in whom the 10mg dose is well-tolerated but not effective; and
• for patients taking concomitant moderate CYP3A4 inhibitors, a 5mg dose would be necessary.