If you have invited a person to your studio and they have not yet accepted your invitation, you can delete the pending invitation by following these steps:
1) Select "Invitations" in the Members tab on the left-hand navigation pane.
2) You will see a list of pending invitations. To remove an invitation, select the check box next to the person's name (Note: you can select multiple invitations.)
3) At the bottom of the screen in the action strip, click "Delete Invitation."
The person invited will no longer be able to access your studio. To add them as a member again, you will need to re-invite them.