Ronald Reagan's daughter, Patti Davis, has criticized Will Ferrell over an upcoming comedy, which is about the former President's battle with Alzheimer's.

Ferrell is set to play the role of the former commander-in-chief in the film titled Reagan, which is based on a Black List script penned by Mike Rosolio, as previously reported.

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The film is set at the start of Reagan's second term in office, when he starts suffering from dementia and an intern in tasked with the responsibility to convince the him that he's an actor playing the role of the President in a movie.

In an open letter posted on her blog, Davis slammed the Daddy's Home actor, who will also serve as a producer on the upcoming film, over his decision to make a comedy film about her father's Alzehimer's.

"I saw the news bulletin - as did everyone - that you intend to portray my father in the throes of Alzheimer's for a comedy that you are also producing," Davis wrote. "Perhaps you have managed to retain some ignorance about Alzheimer's and other versions of dementia. Perhaps if you knew more, you would not find the subject humorous."

Davis also recalled the things her family had to go through while her father struggled with Alzheimer's, a disease she described as the "ultimate pirate" that ""steals what is most precious to a human being - memories, connections, the familiar landmarks of a lifetime that we all come to rely on to hold our place secure in this world and keep us linked to those we have come to know and love."

"I watched as fear invaded my father's eyes-this man who was never afraid of anything. I heard his voice tremble as he stood in the living room and said, 'I don't know where I am,'" she added. "There was laughter in those years, but there was never humor."

Davis then told the 48-year-old to go visit dementia patients and their family members and explain to them what he finds amusing about the disease.

"The only certainty with Alzheimer's is that more will be lost and the disease will always win in the end," she said. "Perhaps you would like to explain to them how this disease is suitable material for a comedy."

TagsWill Ferrell, Will Ferrell Ronald Reagan, ronald reagan, Ronald Reagan daughter, Ronald Reagan Alzheimers, Ronald Reagan dementia, Patti Davis, Patti Davis Will Ferrell, Reagan