By Jonathan Stempel

Sept 25 (Reuters) - A federal judge in Chicago dismissed racketeering claims in a lawsuit accusing Abbott Laboratories and AbbVie Inc of causing health plans to pay unnecessarily for the latter's blockbuster Humira arthritis drug and AndroGel testosterone drug instead of cheaper generics.

In a decision on Thursday, U.S. District Judge Robert Dow said the New England Carpenters Health and Welfare Fund failed to show that the defendants "joined together" illegally with pharmacies and intermediaries to maximize sales, by offering savings cards or coupons to help patients reduce co-payments.

The plaintiff also accused the companies of insurance fraud, saying they instructed pharmacies to conceal the "subsidies" by processing them as secondary insurance rather than as discounts.

"While the amended complaint includes some allegations of cooperation between pharmacies and the co-pay subsidy administrators, it falls short of indicating that pharmacies processed savings cards in a fraudulent manner in order to further the distinct goals of an enterprise, separate and apart from the pharmacies' business," Dow wrote.

In dismissing claims seeking unspecified triple damages under the federal racketeering law known as RICO, Dow said he may also lack jurisdiction over the remaining state law claims in the lawsuit, alleging interference with contracts. He scheduled an Oct. 7 hearing on that issue.

Humira treats rheumatoid arthritis and plaque psoriasis, while AndroGel is a treatment for men with low testosterone.

AbbVie reported Humira sales of $5.93 billion and AndroGel sales of $472 million for the first six months of 2014. Abbott is based in Abbott Park, Illinois, and split off North Chicago-based AbbVie at the beginning of 2013.

Lawyers for the Massachusetts-based plaintiff did not immediately respond to requests for comment. Abbott and AbbVie did not immediately respond to similar requests.

According to the complaint, the hiding of co-pay subsidies could boost health benefit plans' prescription drug costs by $32 billion industrywide over 10 years.

The case is New England Carpenters Health and Welfare Fund et al v. Abbott Laboratories et al, U.S. District Court, Northern District of Illinois, No. 12-01662.

(Reporting by Jonathan Stempel in New York; Editing by Cynthia Osterman)