Shares of AbbVie (NYSE:ABBV) hit a session low on Tuesday as Reuters reported that UnitedHealth (NYSE:UNH) is removing the company’s blockbuster therapy Humira from some of its formulary lists for preferred drugs, following similar moves by rivals Cigna (NYSE:CI) and CVS Health (NYSE:CVS).

UnitedHealth (UNH) added that Amgen’s (AMGN) Humira biosimilar Amjevita will be among the alternatives available on its lists for commercial health plans operated by its pharmacy benefit manager (PBM) Optum Rx.

The decision, expected to take effect Jan. 1, 2025, is the latest blow to AbbVie’s (ABBV) rheumatoid arthritis therapy, which became the world’s top-selling drug for the tenth consecutive year, making up more than a third of the company’s top line in 2021.

In August, Cigna (CI) said Humira would be removed from the formulary lists of many of its healthcare plans in 2025 in favor of biosimilars. Early this year, CVS Health (CVS) said its PBM unit, Caremark PBM, would remove Humira from its commercial formularies on April 1.

In January 2023, AbbVie’s (ABBV) U.S. market exclusivity for Humira (adalimumab) ended as cheaper biosimilars entered the market.

In addition to Amgen (AMGN), Alvotech (ALVO)/ Teva (TEVA) and Sandoz (OTCQX:SDZNY) (OTCQX:SDZXF) were among other developers to launch their Humira biosimilars in reaction.