Hi,
Link-State protocols requires that all nodes in the same area have the same LSP/LSA database so you can't filter LSP's during the flooding phase. In OSPF you can filter which prefix will be inserted in the RIB via a distribute-list but this way is not available for ISIS.
What you can try is to set the distance to 255 for specific ISIS prefixes so they will not be inserted in the RIB.
If you want the specific routes to be removed but still reachable, you need to split your ISIS into different area's
HTH
Laurent.
