A U.S. provisional patent application is often filed in advance of a public disclosure or a sale to establish a “priority date” and thereby preserve the right, under Article 4 of the Paris Convention, to file an international or other non-U.S. patent application within one year. However, simply filing such a priority application might not achieve that goal.

A recent decision from a U.K. patent court, Edwards Lifesciences AG v Cook Biotech Incorporated, warns of a pitfall when multiple inventors are involved. Obtaining written assignments of ownership of the provisional application from all the inventors before filing the later application can be crucial to avoiding prior art published between the priority date and the later application’s filing date.

Without a complete assignment, the later application may not get the benefit of the earlier filing date of the priority application, and intervening prior art may be used to block patentability of the later application or to invalidate a patent that issues from the application. The legal relationships between the inventors and the entity that files the non-U.S. application, as well as the country in which the later application is filed, determine the level of formality required in the assignments.

Many inventions are made by employees or contractors within the scope of their engagements. A corporation typically obtains ownership of an invention, and any corresponding patent applications and eventual patents, through assignments (signed documents that evidence transfers of ownership) from individual inventors to the corporation. Some employment or consulting contracts obligate inventors to sign such assignments. However, absent clear contract language or a signed assignment, legal presumptions about the ownership of intellectual property (“IP”) may vary from state to state and between the U.S. and other countries.

For example, in the U.K. there is a stronger presumption than in the U.S. that an employer owns IP developed by an employee. Under UK law, if an invention may be expected to result from an employee carrying out his or her duties, the invention belongs to the employer. Often, no written assignment is obtained. However in the U.S., an employee must be clearly employed to invent, such as by being tasked to develop a particular product or to solve a particular problem, before an obligation to assign a resulting invention is inferred. Even less obligation to assign is implied when a person provides consulting services.

Furthermore, the U.S. differs from most other countries on the question of whether the inventors or the corporations have the right to file patent applications and claim priority to earlier-filed provisional applications. These jurisdictional differences are reflected in, among other things, the terminology used in patent applications. For example, in the U.S., applications are filed by “inventors,” i.e., all the people who actually made the claimed inventions. Only people (not corporations) can be inventors. (One of several co-inventors or an assignee may file an application if an inventor is dead or missing or refuses to sign a patent application, but that special case is beyond the scope of the present discussion).

On the other hand, in most other countries applications are filed by “applicants,” often corporations. An applicant must fully own the invention for which a patent is sought. However, if an invention is co-owned by a corporation and one or more inventors, all must be co-applicants. While the distinction between inventors and applicants might captivate only patent specialists, the country-specific subtleties of who has the right to file a patent application can be critical to securing legal protection. Getting it wrong can mean a patent is invalid, as Cook Biotech recently learned.

The Cook case turned on a “priority” claim. In Cook, three co-inventors filed a U.S. provisional patent application, but only one of the co-inventors was employed by Cook at the time of the filing. Later, Cook filed an international application under the Patent Cooperation Treaty — a so-called PCT application — that claimed priority to the provisional application. Later still, the two non-employee co-inventors assigned their ownership interests in the provisional application to Cook, thereby giving Cook full ownership of the application. The PCT application yielded a European application, which was eventually granted. Cook was the only applicant on the PCT and European applications.

Cook had obtained full ownership of the priority provisional application before the European application was granted. However, the English High Court of Justice ruled that Cook did not have the right to claim priority to the U.S. provisional application, because Cook did not own the invention when the PCT application was filed.

The court said, “A person who files a patent application for an invention is afforded the privilege of claiming priority only if he himself filed the earlier application from which priority is claimed or if he is the successor in title to the person who filed that earlier application. If he is neither the person who filed the earlier application nor his successor in title then he is denied the privilege. Moreover, his position is not improved if he subsequently acquires title to the invention. It remains the case that he was not entitled to the privilege when he filed the later application and made his claim.”

The court rejected Cook’s argument that its ownership of one of the inventors’ (Obermiller’s) interest was sufficient to claim priority to the earlier application, because the provisional application “was not filed by Mr. Obermiller alone and therefore he was not a ‘a person’ who had ‘duly filed an application for a patent’ within the meaning of Article 4A (1) of the Paris Convention.”

Unfortunately for Cook, a patentability-defeating document was published after the provisional filing date, but before the PCT filing date. Europe, like most non-U.S. jurisdictions, has a “strict novelty” requirement for patentability. Thus, without the benefit of the provisional application’s early filing date, the European application fell to an invalidity attack brought by Edwards Lifesciences.

Had the two non-employee co-inventors assigned their rights to Cook before Cook filed the PCT application (or had these two co-inventors been named as co-applicants on the PCT application), the PCT application would have been given the benefit of the earlier filing date of the provisional application, and the prior art could have been avoided.

In the U.S., there is less emphasis on the timing of obtaining assignments from inventors than in other countries. This may be due to the fact that a priority claim in a U.S. application is based on a congruity of subject matter and inventorship between an earlier- and a later-filed application, not on the ownership of the applications. (See, for example, 35 U.S.C. §120).

Thus, when rushing to file a priority-claiming application on or near a one-year anniversary of a priority date, it is easy for U.S. practitioners, clients and inventors to put off dealing with assignments “until we have more time” or to delay the associated expenses. Typically, executing and recording assignments are not thought of as having “hard deadlines.” However, as shown by Cook, assignments should be obtained from all inventors of provisional or priority applications, particularly from non-employee inventors, before filing corresponding PCT or other non-U.S. applications.