How do I abbreviate the name of a corporate author in my in-text citation?

Use either the first few words of the name or, if not cumbersome, the entity’s initials. For example, Institute of Medicine (US) Standing Committee on the Scientific Evaluation of Dietary Reference Intakes and Its Panel on Folate, Other B Vitamins, and Choline might be shortened to Institute or Institute of Medicine, but National Institutes of Health might be shortened to NIH.

Whichever form you choose, use it consistently throughout your work.