Pharmacy Benefit Managers Offer Differing Access to Affordable Biosimilars

Pharmacy benefit managers take different approaches to controlling patient access to biosimilars. Coverage of these cheaper versions of expensive biologics, such as the blockbuster autoimmune therapeutics Humira (adalimumab) and Stelara (ustekinumab), varies significantly from one PBM to another.

As intermediaries in the prescription drug supply chain, PBMs negotiate prices and manage lists of medicines which are reimbursed under patients’ pharmacy benefit. They do this on behalf of health insurers and a wide variety of employers, managing the drug coverage for roughly 266 million Americans. Here, they determine which medications get covered and which have preferred status with fewer conditions of reimbursement such as the use of prior authorization protocols.

PBMs’ management of patient access to lower-priced biosimilars has come under scrutiny in Congress and by the Federal Trade Commission for alleged anti-competitive business practices, such as erecting barriers to competition and steering patients to pharmacies the PBMs own. As such, PBMs have become the focal point of bipartisan legislative efforts aimed at reform.

Biosimilars are highly similar to originator branded biologics which they reference. There are no clinically meaningful differences between biosimilars and reference products. As of October 2024, the Food and Drug Administration had approved 61 biosimilars referencing 17 different large molecules. Forty-three of the 61 have launched so far. Some of the remainder will enter the market soon, while others have been delayed by litigation. Despite biosimilars having substantially lower list prices than the products they reference, their adoption rates vary by molecule and therapeutic area. Oncology, ophthalmology and pegfilgrastim biosimilars have experienced relatively rapid uptake following market entry, but in the immunology, epoetin alfa and insulin glargine spaces they’ve generally lagged.

In what can may be characterized as the traditional model, adopted by, among others, the three major PBM companies that control 80% of the prescription volume in the United States, PBMs may favor higher list-priced products in certain instances because of the greater rebates attached to them. This is because the portion of the rebate retained by PBMs is often calculated as a percentage of a drug’s list price. Rebates are payments made by drug manufacturers to PBMs and insurers in exchange for moving market share towards a “preferred” product.

In the case of biosimilars, PBMs may be incentivized to establish formularies—lists of covered medicines—that favor branded originators or biosimilars with comparatively high list prices and larger rebates over lower priced biosimilars. To illustrate, PBMs who adhere to this model have placed high-priced originators or biosimilars that aren’t the lowest in price in preferred positions on formularies. Rival, cheaper biosimilars attempting to enter the market find it hard to gain traction.

Notably, nearly all marketed Humira-referenced biosimilars are excluded from the big three PBMs’ — CVS Caremark, Optum Rx, Express Scripts—formularies in 2025, Exceptions to the rule include private label products. The three largest PBMs have their own manufacturers which produce private-labeled biosimilars. And though such biosimilars referencing Humira have lower list prices than the originator, they don’t have the lowest wholesale acquisition cost.* Cheaper biosimilars are either excluded from formulary or not preferred.

Meanwhile, Stelara remains on the PBMs’ formularies, but soon biosimilars will be added. A PBM private label product will feature prominently. According to Adam Fein, the PBM Optum Rx’s subsidiary manufacturer Nuvaila’s private label Stelara-referenced biosimilar, Wezlana, will play a “crucial role in its formulary strategy.” Conspicuously, OptumRx will include both high- and low-priced variants of Wezlana. This mimics a strategy it employed with the Humira-referenced biosimilar, Amjevita, which had a low- and high-list price option. The higher-priced option had better uptake than the lower-priced one, presumably owing to larger rebates.

Not all traditional PBMs behave the same way. MedImpact Healthcare Systems, Inc., the nation’s largest independent PBM with 20 million members, announced last week that it is expanding access to two Stelara -referenced biosimilars which don’t have private labels (yet), Selarsdi and Yesintek. In the company’s words, these products will “help reduce costs without compromising access.” Yesintek’s list price is 90% lower than the originator, Stelara. This announcement comes several months after MedImpact expanded access to Humira-referenced biosimilars by adding two more to its formulary.

MedImpact says it rejects industry practices that allow PBMs to earn more when their clients and members pay more than they need to. Yet the company does not offer the cheapest available Humira-referenced biosimilar, Yusimry. Still, MedImpact’s overall approach to biosimilars appears to be different from other traditional PBMs. Perhaps this is because it is both pharmacy- and manufacturer-neutral, which the the big three are not.

And then there are examples of non-traditional PBMs, like SmithRx and CapitalRx which operate a model in which rebates don’t play a role. Here the cheapest products do tend to be favored. Regarding Humira-referenced biosimilars, for example, SmithRx gives preference to Yusimry, which has the lowest WAC on the market. SmithRx is offering the product via Mark Cuban Cost Plus Drug Company.

SmithRx says it has “millions of members;” CapitalRx , three million. Going forward, it’s possible that non-traditional PBMs will become increasingly attractive to employers and others who contract to manage their pharmacy benefits, including patient access to biosimilars.

* WAC does not denote the price paid by any entity within the drug channel, because it excludes rebates and discounts.