The Federal Trade Commission, with the support of the Food and Drug Administration, is warning pharmaceuticals not to unfairly try to block generic drug makers.

According to the FTC, some pharmaceuticals “improperly list patents in the FDA’s catalog of ‘Approved Drug Products with Therapeutic Equivalence Evaluations,” commonly known as the ‘Orange Book.'” Such behavior unfairly prevents other companies from entering the market with off-brand alternatives at a much cheaper price.

“Improper patent listings in the Orange Book illegitimately delay or lock out generic manufacturers from entering the market, depriving Americans of access to lower-cost medicines and drug products,” said FTC Chair Lina M. Khan. “The FTC is making clear that improper Orange Book listings may be an unfair method of competition in violation of the FTC Act. We won’t hesitate to use all our tools to combat illegal practices that are inflating the price of health care, including medicines.”

“The FDA appreciates and supports the FTC’s efforts to examine whether brand drug companies are impeding generic drug competition by improperly listing patents in the Orange Book,” said FDA Commissioner Robert M. Califf, M.D. “The FDA stands ready to assist the FTC as part of our long history of collaboration to protect American consumers, including our continued engagement under the Executive Order on Competition in the American Economy to help identify and address efforts to block or delay generic drug and biosimilar competition.”