Shortly after Ghostface's video was posted online Shkreli responded on Twitter.
"The format of your apology was unacceptable, @GhostfaceKillah," Shkreli tweeted.
"The consequences will never be the same. (Also, stop making medical claims.)" he tweeted, referring to the claims Ghostface's video made about the supposed benefits of CBD oil. At the end of the video, the oil is called "Revolutionary Hearing" on a graphic, which refers to it reducing seizures, combating anxiety and depression, and reducing blood and sugar levels.
Ghostface's video is the latest iteration of an ongoing beef with Shkreli, which relates only tangentially to the former pharma executive's legal problems in New York federal court, where he is charged with securities fraud. Shkreli has said he is innocent of those criminal charges.
Shkreli, 32, is an avid fan of hip-hop and the Wu-Tang Clan. Last year he shelled out an astounding $2 million for the only copy of the group's album, "Once Upon a Time in Shaolin."
Shkreli, who was already suffering withering public criticism for raising Daraprim's price, made himself even more unpopular after his purchase was revealed by saying he had never listened to the full album and had no plans to let the public hear it.
Ghostface later teed off on Shkreli, calling him a "s---head" for hiking the drug's price during an interview with TMZ, and saying Shkreli was "crazy."
Shkreli then fired back on Twitter, his favorite forum for insulting his many critics, saying that Ghostface Killah "sounds rusty" on the Shaolin album, and "Don't cry, Ghost. All rap careers come to an eventual end." Ghostface responded days later to TMZ by referring to Shkreli as "the Michael Jackson nose kid."
Then, Shkreli made a video surrounded by three masked goons. On that video, Shkreli called Ghostface "my son," threatened to erase the Shaolin abum and "you from the record books of rap."
"I expect you to write a written apology from the heart," Shkreli said.
Last week, during an interview with a New York hip-hop radio station, Shkreli said Ghostface "disrespected me" and that "If he were here right now, I'd smack him right in the face."
On Tuesday, a New York artist sued Shkreli, claiming that the illustrations in the album were only intended to appear on a Wu-Tang Clan fan website.
Last week, while appearing before Congress, Shkreli invoked his Fifth Amendment right against self-incrimination by refusing to answer questions about the purchase of the album.