Eisai rejig means sales-force downsizing at a critical moment for Arena's Belviq

Less than a year ago, Arena ($ARNA) marketing partner Eisai pledged to add another 200 staffers to its rep army for obesity therapy Belviq, bringing the total force to 600. Now, though, the Japanese pharma is doing some stateside job-trimming, and the restructuring will affect Arena's med, too.

As part of the revamp, Eisai recently told the San Diego pharma it would be creating a new, 90-rep neurology sales force to hawk Belviq and two other Eisai products, Arena said in an SEC filing. In addition, Eisai plans to keep a shared contract field force--230 strong--on hand that will promote Belviq alongside another product from another pharma company.

The rejigging accompanies about 215 layoffs for the company, which Eisai announced last week. Its commercial and regional corporate service units will each shrink by about 25%, affecting employees in New Jersey, Massachusetts, Maryland, North Carolina, Washington, DC and in the field.

With the moves, the Belviq rep tally will now fall far short of the 600 Eisai promised it would hit last May when it unveiled its second set of expansion plans. It'll also fall far short of the 900 staffers rival Takeda has enlisted to push competing med Contrave from Orexigen ($OREX).

Indeed, with a couple newly approved products on the scene, it's a less-than-ideal time for any obesity-drug marketer to be shedding firepower. In addition to Contrave, Novo Nordisk's ($NVO) Saxenda recently entered the picture, and Vivus' ($VVUS) Qsymia--Belviq's original competitor--is still hanging around, too.

For now, Belviq is in good shape, leading the market with between 38.6% and 42.5% of new prescriptions, RBC Capital Markets analyst Simos Simeonidis wrote last week in a note to investors.

But at least some analysts expect Contrave to eventually win out, at least where sales are concerned. Wells Fargo's Matthew Andrews, for one, has forecast $1.2 billion for Orexigen/Takeda by 2020, with just $481 million for Belviq and $396 million for Qsymia.

- read Arena's 8-K

Special Report: Limited attention span? Focus on these market shake-ups in 2015

Read more on