The statutory requirement contained in the Pakistan patent law that “claim or claims of a complete specification shall relate to a single invention” impliedly suggests that there may be two inventions housed in one specification but to the extent of claims these shall be directed to one invention only.

Unity being a question of fact, what may be regarded as a single invention is generally decided by the patent examiners on a case by case basis yet against different industries/fields the various provisions of the Ordinance also provide some guidelines.

In the chemical and pharmaceutical sectors where the subject-matter of the patent is a product, a single invention means a single chemical compound excluding its derivatives and salts provided each is having some property/activity that is substantially improved or increased in effect over the base compound. In agriculture biotechnology, a transgenic plant cell excluding the progeny of the original transformant or germplasm containing that cell may be regarded a single invention. In biopharmaceuticals, newly isolated gene/DNA sequences to the exclusion of its derivatives, variants or analogues having an attribute or characteristic different than asserted for the basic invention are treated as a single invention.

The concept of unity distilled from the various provisions of the patent law, however, may not be construed as having some adverse impact vis-à-vis the applicant’s freedom to draft and present different types of claims with varying scope of protection in a single invention. Given this, a product patent may include in addition to an independent claim for a compound, an independent claim for the intermediate if specifically adapted for use in the manufacture of that compound; and provided further if the intermediate and the final product are technically inter-connected and share the same essential structural element. If, however, the intermediate lacks the specific adaption requirement in that it has potential for variety of uses other than use in the manufacture of final product, a divisional route is a good option to avoid non-unity objection. Thus for unity of invention to exist, there must be present a single general inventive concept or an “inventive common character” in distinctly claimed various embodiments of the invention.

Whilst non-unity provides a ground for objection during prosecution of a patent application yet once a patent has been accepted and the option of filing division whether compulsory or voluntary is closed, it cannot be challenged on the ground of non-unity. This is consistent in points of reasoning to both the pre- and post-grant statutory grounds of opposition or belated opposition (revocation) that do not include lack of unity as well as the fact that unity loses significance once the option of filing division is no longer possible.