Innovation Pharmaceuticals Inc (IPIX)

[BonelessCat]

It comes from the Prior Art reasoning in patent law:

First, a person is not entitled to a patent if the invention was "known or used by others in this country, or was patented or described in a printed publication in this or a foreign country" before the date of invention by the applicant for the patent. If, for example, an invention is known or is being used by someone in the United States, another person who makes the same invention at a later date may not obtain a patent.

Second, a patent is barred if "the invention was patented or described in a printed publication in this or a foreign country or in public use or on sale in this country, more than one year prior to the date of the application for patent in the United States."
http://www.tms.org/pubs/journals/jom/matters/matters-9106.html

Although a prior patent is no longer protected, expiration of that prior patent makes the claims of that patent no less applicable. The questions are whether or not the new claim(s) is sufficiently different or if the change is non-obvious to anyone skilled in that area.