The Mirakuru cure is a serum designed to cure individuals of their Mirakuru powers, as well as their deformed bodies or insanity caused by the Mirakuru serum.
Anthony Ivo had spent his whole life studying the Mirakuru. It was because of this that he was able to figure out how to make a cure for it. However, this version of the Mirakuru cure was not made from the Mirakuru serum, he made it from the prisoners that he had tortured and experimented on the Amazo ship. After Sara Lance was captured by Slade Wilson, Oliver Queen goes to rescue her, he asks Anatoly Knyazev to sink the Amazo if he was not back in 1 hour, after Oliver rescues Sara from the cell she was held in, she leads him to where the cure was, however, Slade had already discovered the cure and had it in his possession, Oliver and Sara got captured by their former friend and former ally again.
Oliver and Sara failed to get back in 1 hour, so Anatoly launches a torpedo from a 70-year-old Japanese submarine, that he managed to get working, as the Amazo was sinking Oliver and Slade battle against each other, however, Slade become immobilized by falling debris, Oliver had the chance to use the Mirakuru cure on Slade but chose to kill him, but he still regretted it, however, due to Slade's Mirakuru healing powers, he survived having an arrow drive through his eye by Oliver, he just simply lost consciousness, Oliver would come to regret this mistake 5 years later.
After Slade steals a biotransfuser from S.T.A.R. Labs, so he can transfer his blood to the prisoners he rescued from Iron Heights Prison, to create his own army, Oliver realized that Slade will be weak enough for him to kill, Oliver asked Felicity Smoak, "how do we find the machine that Slade stole", she tells Oliver, "a machine like this drains a huge amount of power from the city's grid when it turned's on, I will know when and where it is", Oliver gets a call from Felicity, she tells him that Slade has turned the biotransfuser on and she knows where he is now, Oliver goes to Slade's hideout when he gets there, finds that it is Roy Harper who is plugged into the machine, not Slade.
Slade reveals that he and Isabel Rochev captured Roy when he was in Blüdhaven, Oliver then battles again Slade and Isabel, he defeats Isabel easily but he is no match for Slade due to his Mirakuru powers, Oliver is forced to use the 2 small explosives from his customized Oneida Kestrel lever-limb compound bow, to knock Slade out, Oliver then rescues Roy and retrieves a sample of the Mirakuru, he then returns to his secret headquarters.
Oliver revealed to his team that there is a cure for the Mirakuru, that Anthony managed to do it, and he also reveals why he never mentioned that there was a cure for the Mirakuru; because 5 years ago when he had a chance to use it on Slade, he instead tried to kill him, Oliver feels that everything that is happening is because of his choice, Felicity takes the Mirakuru sample to Cisco Ramon and Caitlin Snow, she asked her good friends to do her a favor and to keep it a secret; in other words to make the Mirakuru cure.
Felicity gets a call from Cisco; possibly the Mirakuru cure is finished.
Felicity tells Oliver and her team, that the Mirakuru cure is ready and there's a courier en route, unfortunately the courier is attacked by one of Slade's soldiers, he is injured and has a broken leg, unknown to Team Arrow, Slade hacked into their phones and knows about the Mirakuru cure, he sends one of his men to acquire it before Oliver and his team can, Sebastian Blood steals the Mirakuru cure and gives it to Oliver, Oliver hesitates to use the cure on Roy because he doesn't know if it will cure or kill him or not, however after he learns that Amanda Waller is going to bomb the city at dawn to avoid Slade's men from attacking the rest of the country, Oliver is forced to use the cure on Roy.
The Mirakuru cure does not seem to work, however after Roy regained consciousness, and after Oliver and his team, are attacked by one of Slade's soldiers, Roy punched one of the soldiers, he feels a lot of pain, revealing that the Mirakuru cure does work. Oliver, Sara, Nyssa al Ghul and the League of Assassins go to Queen Consolidated, where they use syringe arrows to cure every enhanced Mirakuru soldiers in Queen Consolidated, however they are unable to cure Slade due to the fact that his Deathstroke Costume, is not only bulletproof but arrow proof as well. Oliver, Sara, Roy, Nyssa and the League of Assassins battle and cure the rest of Slade's enhanced Mirakuru soldiers. Slade takes Felicity hostage, unaware that it is a trap setup by Oliver. Oliver distracts Slade long enough for Felicity to inject the Mirakuru cure into his neck. Curing Slade of his Mirakuru powers, they also cure the last remaining member of Slade's army.
The only known side effects of this cure is; after the individuals are injected, they are immediately cured of their Mirakuru powers, as well as their deformed bodies or insanity caused by the Mirakuru serum. After they are cured the individuals immediately lose consciousness, however, Slade Wilson remains conscious longer than his soldiers, possibly because the Mirakuru cure was made from a replicated version of the Mirakuru serum, as it was not made from the original formula.
However, this is likely due to having had his body become accustomed to the use of Mirakuru, as Slade displays no effects of the serum months later, including a lack of hallucinations and most of insanity afterwards, though still antagonistic towards Oliver. It was later revealed, the psychiatric and psychological effects of the Mirakuru takes longer to wear off than the physical effects, as Slade returned to his former-self three years after being cured and described what he did under the Mirakuru's effects as a "bad dream".
- It is not known whether Anthony Ivo's synthetic version of the serum permanently cures individuals of their Mirakuru induced powers or whether it merely suppresses them - as this modified formula was derived from experimentation on test subjects and was, by Anthony's own admission, not an exact replica of the original serum.