BOSTON (Reuters) - Insys Therapeutics Inc said on Thursday it was taking a $4.5 million charge in connection with resolving a lawsuit by Illinois’ attorney general claiming it deceptively marketed a fentanyl-based cancer pain drug for off-label uses.

A box of the Fentanyl-based drug Subsys, made by Insys Therapeutics Inc, is seen in an undated photograph provided by the U.S. Attorney's Office for the Southern District of Alabama. U.S. Attorney's Office for the Southern District of Alabama/Handout via REUTERS

The drugmaker announced the charge as it reported a 38 percent decline in quarterly revenue resulting from a further drop in prescriptions for Subsys, a synthetic opioid at the center of the lawsuit and federal probes.

Those investigations led to federal prosecutors in Boston in December charging six former Insys executives and managers, including former Chief Executive Michael Babich, with engaging in a scheme to bribe doctors to prescribe Subsys.

The Illinois lawsuit, filed in August 2016 by state Attorney General Lisa Madigan, accused Insys of marketing Subsys to doctors who prescribed high volumes of opioid drugs instead of oncologists treating cancer patients.

Insys CEO Saeed Motahari told analysts on an earnings call that he gave top priority to resolving the investigations Insys faces, including by the U.S. Justice Department.

Motahari said he is personally involved in settlement talks with the Justice Department but that the timing of any deal was out of Insys’ control.

“Our strategy is to show we’re taking the right steps, to show them that the mistake that happened won’t happen again,” he said.

Insys said net revenue fell to $42.6 million for the second quarter, from $69.2 million for the same period in 2016, because of the drop in demand for Subsys. It reported a net loss for the quarter of $8.2 million.

Insys shares were down 3.2 percent at $10.65 in morning trading on the Nasdaq.

Babich and his co-defendants have pleaded not guilty. Federal charges have also been filed in several other states against other ex-Insys employees and medical practitioners who prescribed Subsys.

Until recently, Subsys had been the company’s only drug approved by the U.S. Food and Drug Administration.

On Monday, it launched Syndros, a liquid dronabinol aimed at treating nausea and vomiting associated with chemotherapy. Dronabinol is a synthetic form of THC, the principal psychoactive substance of marijuana.

“We remain committed it will be a major contributor to our top line over the next five years,” Motahari said.