I personally haven’t used Apoquel in cats but colleagues have and have moderately good success. If you want to use it in a cat then I recommend talking to vets at the manufacturers (Zoetis) who will be able to give you information that you need. My argument would be why would why do you want to use it? Cats are so resistant to the side effects of corticosteroids and there are liquid oral forms whereas Apoquel will only ever be a tablet.
HI there, I contacted Zoetis about this earlier in year and they will sent through details of several papers although they themselves haven’t done any studies. It appears well tolerated at dose up to 1mg/kg twice daily for a month but there are minimal longer studies. I have used it long term in a couple of cases that were poorly responsive to pred, dex and cyclosporine – I figured the welfare issues warranted the risk.