Yale University  


A-Z Index

Patent Law You Can Use™

Continuation Patent Applications

By Howard M. Eisenberg © 2000

Download this document as a PDF® file

Abstract - A patent application can have children. That is, after a patent application has been filed, one or more applications can later be filed that claim the priority date of the earlier patent, which is referred to as a parent application.

Most patent applications that are filed in the US Patent office are original patent applications, meaning that they stand on their own and do not have an effective filing date based on the actual filing date of another application. But, a patent application can be a parent to one or more applications, known as continuation applications. These continuation applications have the same disclosure as the earlier filed parent application and they claim the benefit of the filing date of the earlier application. This means that the later filed continuation application is considered as having been filed on the date that the earlier filed parent application was filed. The filing date of the parent application is referred to in patent terms as the "priority date" of the continuation application.

In order for the continuation application to be entitled to the priority date of the parent application, several conditions must be met. The first condition is that the continuation application must be filed while the parent application is pending, that is before the prosecution of the parent application in the Patent Office has been terminated, either by abandonment of the application or by issuance of the application into a patent.

This doesn't mean that the original patent application must still be pending. What it means is that any one application in a chain of parent and continuation applications must be pending. For example, it commonly occurs that a continuation application is filed claiming priority from an original parent application. Then later, a second continuation application is filed after the original application has issued as a patent and so is no longer pending. However, the first continuation application is still pending. In this situation, the second continuation application is entitled to the priority date of the original patent application, because it is entitled to the effective filing date (the priority date) of the still pending first continuation application.

The second condition is that there must be at least one inventor in common between the parent application and the continuation application. It is important to keep in mind that inventorship is determined based on the invention as claimed, not on what is described in the specification portion of the application. It is possible therefore for an application to disclose more than one invention and for there to be different inventors of the different claimed inventions.

For example, let's say that a patent application is filed disclosing a new pharmaceutical compound, a method of use of the compound as an antibiotic, and a method for making the compound. The application also discloses that the method for making the compound can be used to make other structurally similar compounds and that this group of compounds has some anti-inflammatory properties. The original application claims the new compound, its method of use as an antibiotic, and the method of making that particular compound. This application names three researchers, Drs. A, B, and C, as co-inventors. Then a first continuation application is filed claiming the method for making similar compounds. The continuation application names only Dr. B because this researcher discovered how this method can be used to make compounds other than the original compound. Later a second continuation application is filed to claim the use of this class of compounds as an anti-inflammatory agent. Dr. C is named as the sole inventor.

In this situation, the third application (Dr. C's) cannot claim priority from the second application (Dr. B's) because there is no common inventor between these two applications. This is not a problem if the first application is still pending because Dr. C's application could claim priority from the original application based on the fact that Dr. C is named as a co-inventor in that application. However, if the first application has already issued as a patent or had become abandoned, then this new Dr. C's application would have to be filed as an original application, having an effective filing date only on the date of its actual filing. This might have serious consequences if there had been any patent-defeating publication between the filing of the original application and Dr. C's later filed application.

The third condition is that the claims in the continuation application must be fully supported in the parent application. If not, the claims will be entitled to the priority date of the later filed application, not that of the original application. This situation typically does not arise with continuation applications, as they have the identical disclosure as the original application. The problem with non-supported claims comes about frequently with what is referred to as a "continuation-in-part application."

A continuation-in-part application, commonly referred to as a "CIP", contains the same disclosure that is found in a parent application plus some additional invention disclosure. If the claims of the CIP are based on the disclosure of the CIP application and are not fully supported by the parent application, the claims will have a priority date of the CIP filing date and not of the parent application filing date. On the other hand, if the claims are supported by the disclosure of the parent application, they will be entitled to that application's priority date.

In previous patent practice, it was common to routinely file applications as CIPs because there were no adverse consequences to doing so. If the claims in the CIP were accorded the priority date of the parent application, that was good. If not, there was no harm done in filing the later application as a CIP.

Due to recent changes in the patent law, however, there is now a very important reason for not routinely filing an application as a CIP application. Because the term of a patent is calculated as extending from its date of issuance to a date twenty years from the filing date of the earliest parent application, filing a patent application as a continuation or as a CIP results in a shortening of the life of the patent. Therefore, it makes sense to file an application as a continuation-in-part only if by doing so the priority date of an earlier application will be obtained. If the priority date of the earlier application is not available because the claims are not supported by the parent application, then it serves no purpose to file the application as part of the chain of continuation applications. This would result in loss of a portion of the term of the patent, without receiving the benefit of the earlier application's priority date.

This consideration is of great importance in the field of biotechnology or pharmaceutical inventions. With many types of inventions, such as software or most electronics, the inventions are often obsolete within a few years. With these technologies, a reduction in the term of the patent by a couple of years is frequently unimportant. With biotechnology and pharmaceutical patents, however, often the most valuable time of the patent term is towards the end of the patent, when a therapeutic method or a drug is well known and is generating a great deal of revenue. Therefore, it is suggested in most situations that CIP applications needing the additional disclosure in order to support their claims should be filed, not as CIP applications but as original patent applications.

Continuation applications are useful in several different situations.

Commonly, upon initial examination of a patent application, the Patent Office will find that the applicant has impermissibly claimed more than one invention. For example, a patent application might disclose and claim a DNA sequence, a protein encoded by the DNA sequence, a vector for the DNA sequence, a method for transforming an organism with the DNA sequence, a method for expressing the protein, a method for use of the protein, a monoclonal antibody against that protein, and a diagnostic method utilizing the antibody. In this situation, the examiner might issue a "Restriction Requirement" to require the applicant to choose one invention for prosecution and to remove claims to the other inventions from the application.

In this case, the applicant can elect to file a type of continuation application called a "divisional" application, in which the claims that were divided out of the original application because of the Restriction Requirement are resubmitted. Like any continuation application, the divisional application must be filed during the time the parent application is pending and must claim only subject matter that is disclosed in the parent application.

Continuation applications are also used when an applicant later discovers that a potentially patentable invention that was disclosed in the original application was not claimed. In this case, a later filed continuation application is filed to protect this invention.

At times, it might be advisable to file a patent application as a CIP application when additional material needs to be added. If some of the claims require the new material for support, but other claims are fully supported by the disclosure of the parent application, then the application should be filed as a continuation-in-part and not as an original application. That is, of course, unless the claims that require the new material are patentably distinct from the claims that are supported by the disclosure of the parent application. Then, the claims that are supported by the original application should be presented in a continuation application, not a CIP, and the other claims, those requiring additional support, should be filed as a new original, non-continuation, application.

Another situation where continuation applications are useful is when the Patent Office allows certain claims in an application, usually narrow claims, but continues to reject other broader claims. Especially in situations where it is important to get patent protection for a particular product to prevent a competitor from infringing, it is often advisable to accept the patent on the narrow claims, delete the broad claims, and then refile a continuation application that contains the broad claims. Usually, additional support for the patentability of these claims, such as in the form of an affidavit or declaration, can be provided with the continuation. In this way, the applicant can obtain a patent to protect the commercial embodiment of the invention, while leisurely pursuing patent protection to obtain a broader scope of coverage.

One somewhat sneaky but perfectly acceptable way of using continuation applications is to make sure that the disclosure of an original patent application is always pending. Because an unlimited number of continuation applications may be filed, the only requirement being that at least one application in the chain of continuation applications is still pending, it is possible to keep a chain of patent applications alive for a long period of time. This is useful when a technology field is crowded and there are several competitors, and when it's not really certain exactly what the competitor will try to bring to market.

Competitors will often review the claims of an issued patent to determine how to make a competing product that does not infringe the patent, referred to as "designing around" a patent. In this case, the initial claims of the original patent may not be effective in maintaining the monopoly power of the patentee regarding the invention. By filing additional continuation applications whenever an existing patent application is to issue as a patent or whenever the prosecution of an existing patent application is to be terminated, an applicant can make sure that a continuation patent application claiming priority from the original application is always pending. Then, if a competing product is ever produced, the claims of the pending continuation application can be amended, or another continuation application can be filed, so that the claims clearly cover the competing product, ensuring that the product will infringe the new claims.

This strategy is not necessary with most applications. However, it can be very useful when the presence of a competitor in the field would significantly decrease the commercial value of a patent. Of course, the disclosure of the pending patent application must fully support the new claims.

A new type of continuation application, called a "Continuing Prosecution Application" or "CPA" has recently been created. In previous practice, if an application received what is referred to as a "final rejection" from the Patent Office, the applicant could file a continuation, called a "file wrapper continuation," in which the prosecution of the application was abandoned and transferred to a new application for continuation of the prosecution. This required the application to be removed from the Examiner, to be assigned a new serial number, and to be put back into the queue for examination. These procedural steps resulted in a significant delay in prosecution. This delay became a serious problem when the United States amended its laws so that a patent term is now measured from the date of filing of the application for a patent, rather than from the date of issuance of the patent itself.

It was to reduce these delays so as not to unnecessarily reduce the length of the effective patent term that the CPA application was devised. When a CPA is filed, the application remains in the hands of the Examiner and keeps the same application serial number as it had previously. In this way, the Examiner is able to continue prosecution of the application, but now with the finality of the rejection removed, which increases the Examiner's and the applicant's flexibility in the proceedings.

The CPA procedure is being phased out by the Patent Office and is being replaced by a simpler procedure, referred to as Request for Continued Examination (RCE) . The CPA cannot be used for applications filed after May 28, 2000. The RCE can be used for any application that was filed after June 8, 1995 and must be used in place of the CPA for any application filed on or after May 29, 2000. The RCE and the CPA are similar but differ in certain technical and procedural aspects.

*     *     *

Reprinted by permission from the author.

Howard M. Eisenberg is a biotechnology and life sciences patent attorney with the firm of Chernoff, Vilhauer, McClung & Stenzel, LLP. He is a member of AUTM and represents a number of university clients. His particular area of concentration is in patents involving human or veterinary medicine.

Howard M. Eisenberg
Chernoff, Vilhauer, McClung & Stenzel, LLP
1600 ODS Tower
601 SW Second Avenue
Portland, Oregon 97204
(503) 227-5631
(503) 228-4373 (fax)

Top of page.