Compounds of formula (I) and pharmaceutical compositions thereof: wherein A1 A2 and A3 are each independently selected from the group consisting of N and CR3, wherein R1 is an optionally substituted heterocyclyl or an optionally substituted —(C1-6)alkyl-heterocyclyl, R2 is an optionally substituted aryl or an optionally subsisted heteroaryl, R4 is an optionally substituted aryl, an optionally substituted heterocyclyl or an optionally substituted heteroaryl, useful as an inhibitor of HIV replication.