NEW YORK (AP) -- Arena Pharmaceuticals and Eisai said Monday that their weight loss drug Belviq will be available to more people thanks to an agreement with pharmacy benefits manager CVS Caremark.

The companies said more than half of all Americans with insurance should now have access to the drug. Caremark is a pharmacy benefits manager, or PBM, which means it run prescription drug plans for employers, insurers and other customers.

In January health insurer Aetna Inc. said it would study weight loss drugs in a pilot program that could boost sales. Aetna is evaluating both Belviq and a competing drug, Vivus Inc.'s Qsymia.

Shares of Arena picked up 27 cents, or 4.5 percent, to $6.27 in midday trading.

Belviq is approved for use in adults who are obese or who are overweight and have at least one serious medical condition, such as diabetes or high cholesterol. The Food and Drug Administration approved Belviq in June 2012, but it didn't go on sale for another year afterward because of logistical concerns like classification by the Drug Enforcement Administration. Arena reported $2 million in net sales of the drug in the third quarter.

Eisai is based in Japan and it has rights to market Belviq in all countries except South Korea, Taiwan, Australia, New Zealand, and Israel.