I can not find needed CPU (STM32F401) in IAR 6.5 list
In a newer Version of IAR Embedded Workbench the F401 devices are supported. You might want to try the Kickstarter Version for some preliminary testruns and maybe upgrade to a full version later.

As of now, I'd say IAR was pretty fast to fetch up with the devices with new updates, but lacking in support for newer devices with older versions of their EWARM, but they can be integrated manually I guess - otherwise there wouldn't be benchmarks around on ULP Bench for the L476 (which is a brand new device) using the v6.6 of IAR EWARM.