Tennessee last year spent $48 million on a single drug, Humira — about $62,000 for each of the 775 patients who were covered by its employee health insurance program and receiving the treatment. So when nine Humira knockoffs, known as biosimilars, hit the market for as little as $995 a month, the opportunity for savings appeared ample and immediate.

But it isn’t here yet. Makers of biosimilars must still work within a health care system in which basic economics rarely seems to hold sway.

For real competition to take hold, the big pharmacy benefit managers, or PBMs, the companies that negotiate prices and set the prescription drug menu for 80% of insured patients in the United States, would have to position the new drugs favorably in health plans.

They haven’t, though the logic for doing so seems plain.

Humira has enjoyed high-priced U.S. exclusivity for 20 years. Its challengers could save the health care system $9 billion and herald savings from the whole class of drugs called biosimilars — a windfall akin to the hundreds of billions saved each year through the purchase of generic drugs.

The biosimilars work the same way as Humira, an injectable treatment for rheumatoid arthritis and other autoimmune diseases. And countries such as the United Kingdom, Denmark, and Poland have moved more than 90% of their Humira patients to the rival drugs since they launched in Europe in 2018. Kaiser Permanente, which oversees medical care for 12 million people in eight U.S. states, switched most of its patients to a biosimilar in February and expects to save $300 million this year alone.

Biologics — both the brand-name drugs and their imitators, or biosimilars — are made with living cells, such as yeast or bacteria. With dozens of biologics nearing the end of their patent protection in the next two decades, biosimilars could generate much higher savings than generics, said Paul Holmes, a partner at Williams Barber Morel who works with self-insured health plans. That’s because biologics are much more expensive than pills and other formulations made through simpler chemical processes.

For example, after the first generics for the blockbuster anti-reflux drug Nexium hit the market in 2015, they cost around $10 a month, compared with Nexium’s $100 price tag. Coherus BioSciences launched its Humira biosimilar, Yusimry, in July at $995 per two-syringe carton, compared with Humira’s $6,600 list price for a nearly identical product.

“The percentage savings might be similar, but the total dollar savings are much bigger,” Holmes said, “as long as the plan sponsors, the employers, realize the opportunity.”

That’s a big if.

While a manufacturer may need to spend a few million dollars to get a generic pill ready to market, makers of biosimilars say their development can require up to eight years and $200 million. The business won’t work unless they gain significant market share, they say.

The biggest hitch seems to be the PBMs. Express Scripts and Optum Rx, two of the three giant PBMs, have put biosimilars on their formularies, but at the same price as Humira. That gives doctors and patients little incentive to switch. So Humira remains dominant for now.