Although four million people have tried GlaxoSmithKline’s OTC weight loss drug Alli during its first year on the market, preliminary sales figures are “pretty underwhelming,” one analyst tells the Associated Press.

WBB Securities analyst Steve Brozak said in an AP report today that the “underewhelming” sales for Alli may be a result of the agency’s marketing campaign, which stresses the user’s need to transform eating and exercise habits for the drug to be effective. This year, the company spent an estimated $150 million on Alli marketing.

GlaxoSmithKline consumer health division marketing director, Joe Cadle, told the AP that first-year sales of Alli point to a “healthy business,” one that can be sustained and grown dramatically as new users try the drug.

“We’re the only company with an OTC product that helps treat something that affects 140 million people,” Cadle added.

Alli is a lower dose version of Roche’s Xenical (orlistat). GSK acquired the OTC rights to the drug from Roche in 2004. At the time of the Alli’s launch last year, GSK estimated it would eventually sell between five million and six million kits annually, translating to at least $1.5 billion in annual retail. A 60-capsule kit costs about $50 while a 90-capsule pack costs about $60.