Rapper Mos Def has been tapped to star with Alan Rickman in "Something the Lord Made," an original movie for HBO about the true story of heart surgery pioneers Alfred Blalock and Vivien Thomas, a white surgeon and a black lab technician.

Multiple Emmy winner Joseph Sargent has come on board to direct the film, which is still in development. Peter Silverman (Lifetime's "We Were the Mulvaneys") penned the script for the project, which has been kicking around for six-and-a-half years.

The partnership between Blalock (Rickman) and Thomas (Mos Def) began in 1929 when the then-19-year-old Thomas' dreams to go to college and medical school were dashed after he lost his tuition savings in the October stock market crash. He then took a job as a lab technician at Vanderbilt University's medical school, working for Blalock, a resident surgeon.

At Vanderbilt and later at John Hopkins University, Blalock and Thomas worked on several breakthroughs that revolutionized cardiac surgery, including the wider use of plasma or whole-blood transfusions to prevent surgical shock, which saved millions of lives during World War II.

Mos Def most recently co-starred in the hit "The Italian Job." His upcoming features include "The Woodsman," "The Sky Is Green" and "A Confederacy of Dunces."

Next up on Rickman's plate is a reprise of his role as Professor Severus Snape in "Harry Potter and the Prisoner of Azkaban," the third movie in the series. He will also be seen in the upcoming comedy "Love Actually."