A drug company subsidiary has pleaded guilty to fraud charges stemming from allegations that the manufacturer schemed to bribe doctors to prescribe its highly addictive fentanyl spray.

The guilty plea entered in Boston federal court Friday by Insys Therapeutics' operating unit is part of a settlement announced this week to resolve investigations into the company.

Chandler, Arizona-based Insys Therapeutics has also agreed to pay $225 million .

Insys Founder John Kapoor and four other former executives were convicted last month of running the bribery scheme. They filed court documents this week challenging their convictions.

Kapoor's attorneys say the former employees who testified against him weren't credible.

His lawyers say prosecutors also introduced unfair and irrelevant evidence, including a rap video showing sales representatives dancing around a person dressed as a bottle of the opioid.