CORS Issue on IE11 - calling https --> http

we have an Angular 5 project that is running off an HTTPS enabled site. https://abc.com/myapp. I am trying to invoke a legacy service which is non-https, but has enabled CORS headers for my client. The call works in Chrome, I can see the Access-Control-Allow-Origin header flowing from the svc to the client. But in IE11, the call does not even reach the server. It is being blocked by the browser itself and I get an Access is Denied error on the console. Any ideas how this can be fixed? Changing IE11 Settings is not an option, it is controlled centrally by firm policy.

Vik