so…esteban had leukemia, no? or was it something else?
Yeah, the implication in what Esteban says about his disease is that he had treatment-resistant childhood leukemia, specifically acute lymphoblastic leukemia. His enrollment in the WRU medicinal trials was meant to be part of a last-ditch effort to save his life.
WRU left some stuff out of their explanations. Esteban's parents believe he wrote them letters, although he never did, and that the treatment eventually failed. WRU kept him and the other successful trial enrollees at a hidden facility disguised as a ranch/summer camp in Wyoming to study long-term effects.
They found Reviverol not only successfully treated multiple severe childhood cancers, but also that those who were given the drug were less prone to infection afterward, too.
Esteban does not know it, but he and his fellow trial recipients are some of the healthiest people in the world.