Nuclear transport modulators and uses thereof

A compound of formula I:

• or a pharmaceutically acceptable salt thereof, wherein:
• R1 is selected from hydrogen and C1-C4 alkyl;
• R2 is selected from O and S;
• and
• R3 is selected from —N(R4)—(C3-C6 cycloalkyl), —C1-C6 alkyl, —(C0-C4 alkylene)-heterocyclyl, and —(C0-C4 alkylene)-heteroaryl, wherein any alkyl, alkylene, heterocyclyl, and heteroaryl portion of R3 is optionally and independently substituted;
• and
• R4 is selected from hydrogen and C1-C4 alkyl.