Buyout speculation fueled by the late-January approval of depression drug Viibryd (vilazodone) ended last week as Clinical Data of Newton, Mass., disclosed an offer much lower than analysts had expected, reported BioWorld Week.

Buyer Forest Laboratories of New York, which is shelling out $30 per share, or about $1.2 billion in cash up front, for the biotech, is a perfect home for Viibryd. Forest already markets Lexapro (escitalopram oxalate), an SSRI, which raked in sales of $586.5 million for the last three months of 2010. Viibryd could help offset declining sales of Lexapro after it starts losing patent protection next year.

Piper Jaffray analyst David Amsellem called it a “Hail Mary pass [that] falls incomplete.” Given the crowded depression market and the number of generics available, “we have a difficult time envisioning blockbuster potential for Viibryd.”

Forest agreed to pay another $6 per share if certain 12-month sales targets are hit: $1 per share if Viibryd reaches $800 million in sales within five years; $2 per share if sales meet or exceed $1.1 billion within six years; and $3 per share if sales reach at least $1.5 billion in seven years.

Though Forest also picks up rights to stress imaging agent Stedivaze (apadenoson), the value of the Clinical Data acquisition hinges on Viibryd’s commercial potential. A dual-acting SSRI and 5HT1A partial agonist, the drug could stack up well as an alternative to traditional SSRIs and erotonin/norepinephrine reuptake inhibitors. Many patients do not respond to treatment with those drugs, and Viibryd’s safety profile—fewer weight gain and sexual side effects—might be enough of an advantage to garner a nice share of the $12 billion antidepressant market.