The Institute for Clinical and Economic Review (ICER) said the spending increase in 2021 was still less than the $1.67 billion rise in the previous year. This is the third year the group has looked at the top 250 drugs by spending and assessed if those driving U.S. spending increases were justified.

"Last year, a huge part of the (increase in) spending was all one drug...in this year, we saw the increase was more spread out across different drugs," ICER's Chief Medical Officer David Rind told Reuters.

In 2020, Abbvie's rheumatoid arthritis therapy Humira led to an almost $1.4 billion increase in U.S. drug spending, accounting for over 80% of the total increase.

Rind said Humira dropped off the ten costliest prescription drug list as its net price hike was lower in 2021. Since there was no single drug which drove the increase in spending this year, the rise is also relatively smaller compared to 2020, he added.

Bausch Health's Xifaxan, an antibiotic drug for traveler's diarrhea, led to an increase of nearly $175 million in spending, among the highest this year.

Johnson & Johnson's schizophrenia therapy Invega Sustenna and Amgen's osteoporosis drug Prolia followed closely with spending increases of $170 million and $124 million, respectively.

All three drugmakers did not immediately respond to Reuters' requests for comment.

President Joe Biden's signature Inflation Reduction Act will allow the government to choose 10 drugs to negotiate from among the 50 costliest drugs for Medicare, the government healthcare program for people aged 65 and older or disabled, starting in 2026.