Why exactly would anyone want the cure for immortality, anyway. It isn't just that their methods are dangerous, it's that their goal makes absolutely no sense. They're trying to trade super powers and eternal life for the ability to suffer from horrible physical and mental degeneration before inevitably dying.
They could just buy adult diapers and go around shitting all over themselves and pretend to be mortal that way. They'd get the exact same benefits without all the hassle.