After developing a passion project for nearly 20 years, Mel Gibson is finally ready to move forward, bringing another A-list star along for the ride. Sean Penn is in talks to star alongside Mel Gibson in the unique biopic Professor and the Madman. Both stars will play the two men who helped create the Oxford English Dictionary, under amazing circumstances.

The Hollywood Reporter reveals that Mel Gibson purchased the rights to Simon Winchester's book of the same name back in 1998, and has been developing it ever since. For many years, he had planned to direct the biopic himself, but this new report reveals that he has handed the directorial reins over to Farhad Safinia, who co-wrote Apocalypto with Mel Gibson. Farhad Safinia wrote the screenplay, with Todd Komarnicki and John Boorman writing an earlier draft.

Mel Gibson will star as Professor James Murray, who, in 1857, started compiling entries for the comprehensive work that would come to be known as the Oxford English Dictionary. Sean Penn will portray Dr. W.C. Minor, who compiled more than 10,000 entries for the dictionary, but, at the time, he was an inmate at an asylum for the criminally insane. Both men's work helped change the course of literary history.

Voltage Pictures is providing financing for the project and will sell it to international buyers at the Toronto International Film Festival next month. Mel Gibson will produce through his Icon Productions company, along with his partner Bruce Davey. The filmmakers are eyeing a production start in September, but it isn't known where exactly filming may take place.

Surprisingly, this project will mark the first time both Mel Gibson and Sean Penn have worked together. They both burst onto the Hollywood scene at around the same time, with Mel Gibson starring in the 1979 classic Mad Max and Sean Penn's breakout role coming just two years later in 1981's Taps. We'll be sure to keep you posted with more updates on Professor and the Madman as soon as more information is released.