It's safe to run, not sure why Windows isn't letting you run it, if you're worried you can always download it through the itch.io app instead
If you download the itch.io launcher https://itch.io/app you can copy + paste links, or add the game to a collection and download it from there, not 100% sure where the app downloads to though but I assume you can launch it like a normal .exe if you got it through the app