I agree on the surface that cloze 2 gives away cloze 1, but now the testable info of cloze 2 is removed (i.e. . it’s most important clinical indication of why we even use this drug is removed in place for side effects) . That is not ideal. The side effects of nitrosureas are already tested in Anki ID 1509222029799 already.
So then there are two options here to make the card better, but the current suggestion does not work: (1) change c2 to be “…useful for treating {{c2::brain tumors}}” or (2) just get rid of c1 because we don’t really care about that it can penetrate the blood-brain barrier. We care about its clinical use above all else – brain tumors. The fact that nitrosoureas cross the blood-brain barrier is already tested in AnkiID 1509221847885 for mechanism/Step 1 purposes