Still depends on which 140 category...

In general principle, EAD allows one work for any company in any field or even in grocery stores. However, for primary petitioner, 485 will be denied if he/she significantly changes work field described on 140 petition.

More particularly, if you applied through EB1a/NIW, you can certainly walk away from your current position and work in a similar field with EAD in another Univ or Industry and further change to another company.

For Eb1b or EB2-perm or EB3, to keep your 485 valid, you have to fulfill 180 days service for sponsored employer after submitting 485 before using EAD or change company with H1B.