Comedian Bill Cosby on Tuesday sought to derail Pennsylvania prosecutors' effort to make him stand trial on sexual assault charges, contending that a deal reached over a decade ago gave him immunity from prosecution.

An entertainer who built a career on family-friendly comedy, Cosby now faces accusations from more than 50 women that he sexually assaulted them, often after plying them with drugs and alcohol, in a series of attacks dating back to the 1960s.

Prosecutors late last year charged Cosby, 78, with sexually assaulting Andrea Constand, a former basketball coach at his alma mater Temple University, just days before the statue of limitations to bring charges ran out.