Eli Lilly said on Tuesday it has begun selling higher doses of its popular weight-loss drug Zepbound in vials in the U.S. at a $150 discount to the cost of the injector pen versions, as it seeks to spur further demand for the medicine.

The drugmaker said patients could purchase 7.5 milligram and 10 mg vials of Zepbound for $499 a month on the LillyDirect website. That is nearly 23% less than the $650 Lilly charges for auto-injectors of the drug to patients who are insured but not covered for the medicine.

The U.S. drugmaker last August launched vials of the two lowest doses of Zepbound, which is typically sold in auto-injector pens, to help increase availability. On Tuesday, it said it had also cut the prices for a month's supply of those doses by around $50 each. They now cost $349 and $499 a month through LillyDirect.

Patrik Jonsson, Eli Lilly’s president of cardiometabolic health, said in an interview that more than 10% of patients starting on Zepbound have been initiated on vials since their launch.

Lilly is looking for ways to stimulate further demand for Zepbound this year to help ease investor agitation over signs of weakness in sales, and to better compete with Danish rival Novo Nordisk's popular Wegovy.

Novo offers Wegovy on its website for $650 for a month's supply to patients not covered by insurance for the drug, but does not sell its medicine in vials.

Lilly's new offer of $499 per month is still higher than the $231 to $330 compounding pharmacies typically charge for their versions of Zepbound and Wegovy in the U.S., although compounders have been told to cease selling their copies in the coming months.

Shortages of the weight-loss drugs pushed patients to cheaper compounded versions, which can be sold and distributed in bulk as long as the original drug is on the U.S. Food and Drug Administration's shortage list.

In the past three months, the FDA took both Zepbound and Wegovy off its shortage list, spurring lawsuits from compounding pharmacies.

Lilly said patients must refill their prescriptions of the two higher dose vials within 45 days of their first fill to get the same pricing, and would otherwise have to pay as much as $699 for repeat prescriptions. Jonsson said this requirement ensures patients comply with a dosing regimen approved by the FDA.