X Never Marks the Spot

That's entirely possible, since LuthorCorp have had many medicine-related Kryptonite research, but there doesn't seem to be any sign in SV that meteor infections could be cured, otherwise Clark could have asked Jor-El for that ("Stop forcing me to take on the alien overlord mantle and help me do something about the psychotic mutants that could harm me and other innocent people instead, there's a helpful Dad"). Unless Lex is smart enough to discover a way to nullify the effects of Kryptonite, which he did in the comics, I think he would prefer to control and utilize their powers despite the dangers and illegal means to harness it, because he's seen the havoc aliens could wreak, and he'd rather direct the mutants' energy or urges into useful activities against that threat. Maybe he is utilitarian enough that he thought to focus on the active danger posed against the general population more than helping the smaller number of meteor-infected people to achieve normal lives.