Attorneys general from 35 states and the District of Columbia are suing a British drug company, alleging it tried to keep less expensive generic versions of the opioid addiction treatment Suboxone off the market.

The suit says the drug company, Indivior, was granted exclusive rights in 2002 to sell Suboxone tablets for seven years, Fox News reports. When those rights expired, the suit alleges, Indivior company worked with the New Jersey company MonoSol Rx to make an oral strip form of Suboxone. The strip form was marketed as safer than tablets, according to the suit. MonoSol Rx is also named in the suit.

The attorneys general said the companies engaged in a multi-pronged “product-hopping” scheme to block competition to Suboxone, “ultimately generating almost one billion dollars in undeserved profits,” according to a news release by California Attorney General Kamala Harris. “In this kind of scheme, pharmaceutical companies try to maintain profits generated via a monopoly by slightly reformulating their product in a way that blocks generic competitors without offering any significant medical or therapeutic advantages to patients,” the release notes.