Sphingosine kinase inhibitors

A compound of the formula I

• or a pharmaceutically acceptable salt thereof, wherein:
• X—R2 is —C(R3,R4)N(R5)—R2 or —C(O)N(R4)—R2;
• R1 is phenyl substituted with 1 to 5 groups that are independently halogen, haloalkyl, —CONR′R″, OC(O)NR′R″, —NR′C(O)R″, CF3, OCF3, —CN, —CO2H, —S-alkyl, —SOR′R″, or —SO2R′, wherein R′ and R″ are independently H or (C1-C6) alkyl, and wherein each alkyl portion of a substituent is optionally further substituted with 1, 2, or 3 groups independently selected from halogen, CN, OH, and NH2;
• R2 is aryl, -alkylaryl, heterocycloalkyl or -alkyl-heterocycloalkyl;
• R3 is H or alkyl;
• wherein the alkyl and ring portion of each of the above R2 and R3 groups is optionally substituted with up to 5 groups that are independently (C1-C6) alkyl, halogen, haloalkyl, —OC(O)(C1-C6 alkyl), —C(O)O(C1-C6 alkyl), —CONR′R″, —OC(O)NR′R″, —NR′C(O)R″, —CF3, —OCF3, —OH, C1-C6 alkoxy, hydroxyalkyl, —CN, —CO2H, —SH, —S-alkyl, —SOR′R″, —SO2R′, —NO2, or NR′R″, wherein R′ and R″ are independently H or (C1-C6) alkyl, and wherein each alkyl portion of a substituent is optionally further substituted with 1, 2, or 3 groups independently selected from halogen, CN, OH, and NH2;
• and
• R4 and R5 are independently H or alkyl.