Drugmaker giant Pfizer Inc. (NYSE:$PFE) has officially filed a lawsuit against Johnson & Johnson (NYSE:$JNJ) on claims that its rival’s contracts with health insurers for blockbuster rheumatoid arthritis drug, Remicade, were anticompetitive and blocked sales of Pfizer’s new biosimilar.

Specifically, Pfizer claims that J&J is offering discounts on its Remicade treatment in exchange for excluding Pfizer’s drug from insurance coverage, essentially prohibiting patients’ usage.

In fact, J&J signed exclusionary contracts with health insurers, hospitals, and doctor groups after U.S. regulators approved it as a reasonable substitute for Remicade in 2016, according to Pfizer.

Remicade is an infused treatment for chronic autoimmune disorders and costs around $4,000 per dose, or $26,000 a year.

Pfizer has not been able to acquire customers due to J&J’s anticompetitive actions. The suit comes at an opportune time, when insurers, consumers, and the government alike have pushed for lower drug prices, suggesting that double-digit annual price increases are simply unsustainable.

Pfizer shares were up 1.6%, at $36.02, while J&J shares fell 1.4% to $133.39 as of morning trading.

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