(Bloomberg) -- With more states and countries opening up to legal cannabis, there are growing concerns about a rise in addiction. That’s leading some companies to step up efforts to develop drugs to combat the problem.

Indivior Plc, a U.K.-based company that makes drugs for opioid addiction, has partnered with French biotech firm Aelis Farma to begin a mid-stage study on a therapy that aims to help the condition known as cannabis use disorder. The pact involves a $30 million payment now to Aelis, and lets Indivior buy the rights to the drug for $100 million later, along with possible milestone payments and royalties, if the trial is successful, Indivior said Tuesday.

They’re among a handful of companies seeking to address what they see as a growing problem, particularly with no drugs approved by the U.S. Food and Drug Administration for treatment. According to clinicaltrials.gov, 69 studies have been registered for drugs aimed at cannabis use disorder. Of those, around a third appear to be recruiting or enrolling subjects.

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“Cannabis is the most common substance of abuse besides alcohol and tobacco, and there is no FDA-approved drug, which is concerning when you look at where cannabis use in general is headed,” Indivior Chief Executive Officer Mark Crossley said in an interview.

In the U.S. alone, where an increasing number of states have approved marijuana use and there’s growing momentum for federal legalization, the cannabis industry is expected to reach $41.5 billion by 2025, according to figures from New Frontier Data. The National Institute on Drug Abuse cites research suggesting 9% to 30% of people who use marijuana may become addicted.

Crossley said he projects the market for drugs to treat marijuana addiction will be “in the multiple billions of dollars.” He said the increasing potency of cannabis, which he estimates has increased fivefold in the past few decades, means the probability of people developing cannabis use disorder is “significantly higher” today.

Indivior, which last year paid $600 million to settle U.S. criminal probes of illegal marketing of an opioid-addiction treatment, will still need to fund a late-stage study if the cannabis-drug trials are successful. That means it could still be six or more years before it’s brought to market.

Indivior’s chief scientific officer, Christian Heidbreder, said the drug targets the brain receptor that’s affected by cannabis’s psychoactive ingredient.

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