Bryan Fuller's Hannibal TV show adapted elements of all of Thomas Harris' Lecter books, with the prominent exception of The Silence of the Lambs. It's no secret that Fuller eventually wanted to incorporate the story and characters of Silence of the Lambs into Hannibal, but things never ended up coming together to make that happen before the show was canceled by NBC in 2015. Hannibal did at least adapt parts of Red Dragon, Hannibal (the book), and Hannibal Rising, albeit while often throwing curve balls at fans in how it did so.
With a Clarice Starling-centered series coming to CBS, simply titled Clarice, the door now seems to be closed for good on a potential Hannibal season 4 ever adapting The Silence of the Lambs to any real degree. While that certainly doesn't preclude a continuation of the existing story starring Hannibal and Will Graham, it'll still be a disappointment to diehard fans who looked forward to seeing Clarice and Will Graham interact onscreen for the first time ever.
So, why did Hannibal not attempt to use Clarice, Buffalo Bill, or other Silence of the Lambs characters and storylines when it was still on the air? The simple answer is this: the show legally couldn't. Here's why.
Why Hannibal Never Adapted The Silence of the Lambs
In the mid-1980s, movie producer Dino de Laurentiis bought the screen rights to the Hannibal Lecter character, and the content of the novel Red Dragon. The book was then adapted into the 1986 movie Manhunter, directed by Michael Mann. While Manhunter is generally well-regarded today, it was a bomb upon release, and when Orion Pictures wanted to adapt Red Dragon's follow-up book The Silence of the Lambs, de Laurentiis didn't think much of it, allowing them to use the Hannibal character for free. The Silence of the Lambs then won a bunch of Oscars and made hundreds of millions in profit, presumably making de Laurentiis feel like a fool.
From then on, de Laurentiis held a death grip on anything to do with Dr. Lecter, producing or co-producing the movies Hannibal, Red Dragon, and Hannibal Rising, with his wife and producing partner Martha continuing the trend after Dino's 2010 death by producing the Hannibal TV show. The Dino de Laurentiis company still fully owns the movie and TV rights to the Hannibal Lecter character, meaning no studio can use him without giving de Laurentiis a piece of the pie. However, MGM - now parent company of Orion - retains ownership of The Silence of the Lambs' screen rights, meaning they control the specific plot of the book, and characters created for it, such as Clarice Starling and Buffalo Bill.
What this means practically is that Hannibal TV show producers tried their best to get MGM to play ball on allowing them to adapt Silence of the Lambs and use its characters, but MGM was unwilling to agree to a deal. MGM is now behind the Clarice TV series, which, on the flipside, isn't allowed to use Hannibal Lecter. How Clarice's story can be told without even mentioning Hannibal remains to be seen, but one wonders why de Laurentiis and MGM couldn't just come to a shared agreement that could benefit both shows.