No, you didn’t miss one; I’m skipping glitch #456 (for now, at least) because I’m just not up to dealing with the subject matter.
Change on a new drug to of a new drug.
Add an apostrophe to sister’s to form the possessive.
Add a comma before though. (In this usage, though is an interrupter, which means it needs to be separated from the rest of the sentence.)
A young woman volunteers for tests of a new drug that, if released, could save her sister’s life. The side effects, though, are nothing she expected.