(Reuters) -An influential drug pricing watchdog on Tuesday said popular GLP-1 weight-loss injections have become more cost-effective as their prices have fallen and studies have shown proof of their cardiovascular health benefits.

In a draft report, the Institute for Clinical and Economic Review gave its highest cost-effectiveness rating to both Novo Nordisk's semaglutide, sold as Ozempic and Wegovy, and Eli Lilly's tirzepatide, sold as Mounjaro and Zepbound, for weight loss compared to lifestyle modifications such as diet and increased exercise.

The cost analysis follows an April report from the small but influential Boston-based research group highlighting the need to make the widely-prescribed drugs more affordable.

"Prices have come down a ton," in the last couple of years, ICER Chief Medical Officer Dr. David Rind told Reuters. But due to high demand, "payers are having a lot of problems with affordability of these drugs," he said.

Around 40% of U.S. adults are obese, according to the Centers for Disease Control and Prevention. A recent study found that U.S. spending on GLP-1 drugs, which in trials led to weight loss of 15%-20%, reached nearly $72 billion in 2023.

ICER said evidence that Lilly's drug is more cost-effective than Novo Nordisk's medication is "promising but inconclusive."

"We know for certain that tirzepatide has greater weight loss and strongly suspect fewer gastrointestinal side effects," Rind said. "What we don't really know is whether the cardiovascular outcomes are better, worse or the same," he said of the drugs' ability to significantly lower the risk of serious heart problems.

In obese patients with heart disease, injectable semaglutide has been shown to reduce the risk of major cardiovascular events and death, while tirzepatide has been shown to reduce risks for obese adults with a common type of heart failure.

In a 2022 report before tirzepatide was approved for weight loss, the group rated semaglutide's cost-effectiveness as slightly lower than the current report.

ICER said an oral version of semaglutide that is now under regulatory review is cost-effective compared to lifestyle changes, but was less certain about its value compared to the injected version. It did not assess the GLP-1 pill orforglipron that Lilly is expected to submit to regulators this year.

ICER estimated the current U.S. annual net price for Novo's semaglutide at $6,830, down from $13,618 in its 2022 analysis. It used a net price of $7,973 for Lilly's tirzepatide, which has a U.S. list price of around $13,000. Both companies sell their drugs directly to consumers for about $6,000 a year.

ICER will hold a public meeting on the draft report in November, after which it will issue a final report.

More than half of large U.S. employers plan to scale back healthcare benefits next year as rising costs from weight-loss and specialty drugs squeeze budgets, according to a recent survey by consulting firm Mercer.

ICER's Rind said cost-effectiveness of the GLP-1 drugs remains "a moving target" given additional studies underway and the fact that semaglutide is one of several drugs under negotiation with the federal government's Medicare plan, with that price expected to be announced in November.

For those without insurance coverage for GLP-1s, the direct-to-consumer route "is a good use of dollars" for people who can afford it, he said.

"But what's going on is that we're not providing resources to many of the people who would most benefit from these therapies... It would be better if we figured out a national way to improve affordability across the broad set of patients," Rind said.