

Blocking Patents Explained
What is a Blocking Patent?
A blocking patent is a patent that prevents a third party from the practice or commercial exploitation of a modified version of the the device or process underlying the patented invention. When a patent stops another product or service (even if patented) from actually being produced because its execution would ultimately need to infringe upon it, it can then be referred to as a blocking patent. In practice companies employ blocking patents in a variety of strategically intentional ways.
A Hypothetical Example of a Blocking Patent Would Be:
Suppose that a person, Sally, holds a patent for her invention of a bluetooth speaker, the Kube. Another person, James, creates an updated version of Sally’s Kube, with several added features and improvements not present in the original Kube—let’s call James’ invention the Ultra3. However, James cannot manufacture his Ultra3 without infringing Sally’s patent. In this case, the patent Sally holds for the Kube is a blocking patent. James’ best move would then be to try to cross-license with Sally.
Now let’s say a third party, William, recognizes a few years down the line that in order to work with new battery technology which would provide better battery life and louder playback for customers both the Kube & Ultra3 would need a new set of internal technology. If William creates that and patents it, Sally and James would ultimately have to cross-license with him in order to keep the Kube & Ultra3 viable on the market. James’ patent on improved battery technology would essentially then block the necessary innovation for the original inventions to stay viable on the market.
Examples of Blocking patents in the Real World
In January of 2017, a U.S. District Court ordered an injunction on sales of pharmaceutical companies Regeneron and Sanofi’s cholesterol medication, Praluent. This injunction on Praluent sales was the result of an ongoing patent dispute between Regeneron and Sanofi, and Amgen, the makers of a similar cholesterol medication called Repatha. Prior to the injunction, a lower court had already found Regeneron and Sanofi to be infringing on two patents held by Amgen. The patents in question cover a particular class of cholesterol-lowering medications called PCSK9 inhibitors; a class which includes Regeneron and Sanofi’s drug, Praluent. As the court upheld the validity of Amgen’s patents, they found Regeneron and Sanofi’s production and sale of Praluent to infringe on Amgen’s patents.
In the case just described, the pharmaceutical company Amgen’s patents for the drug Repatha act as blocking patents. Because Amgen owns patents for the entire class of cholesterol-lowering drugs known as PCSK9 inhibitors, competing pharmaceutical companies cannot manufacture and sell their own PCSK9 inhibitors. Even if the exact formulation of a competing company’s PCSK9 inhibitor medication, such as Praluent, differs from the formulations of any drug manufactured by Amgen, the competing company’s practice of their new PCSK9 inhibitor drug will infringe on Amgen’s patents. This is because Amgen’s patents cover the underlying mechanism and processes by which PCSK9 inhibitors work to lower cholesterol, not just the particular formulation of any PCSK9 inhibitor drug invented by Amgen, such as Repatha. For more information on the patent dispute between Regeneron/Sanofi and Amgen regarding their PCSK9 inhibitor medications follow the links.
Further Reading on blocking patents:
- “Blocking patents: What they are and what they do” by Dominique Guellec, Catalina Martinez, and Pluvia Zuniga in 2008. According to the authors, “When the exclusionary power provided by patents is aimed at keeping competitors off a particular market or technology field rather than at protecting an invention, patents become a strategic blocking tool for offensive or defensive purposes.” In other words, the purpose of a blocking patent is not simply to protect the patent owner’s invention against copycats, but to prevent competitors from putting rival products on the market that might redirect revenue away from the original patent holder. (similar to William’s battery technology in our bluetooth speaker example)
In the paper, the authors examine the characteristics and impact of blocking patents. The authors find that patent applications which are cited as, “compromising the patentability of other applications, and that have never been cited as contributing to the state of the art, ”have a stronger impact on the likelihood of refusal or withdrawal than others”. The above is essentially their definition of a blocking patent. In addition, the authors find that patent applications which are subsequently withdrawn by their applicant are statistically the most effective in preventing other parties’ applications for patents of similar products. In the words of the authors, such patents have the greatest “killing power.”The sort of patent application just described—one which inhibits the success of other patent applications before being withdrawn by the applicant—is what the authors call a defensive patent application. Defensive patent applications, “endow their owner with no exclusive right per se (as no patent is granted) but keep competitors away from the relevant technological field, hence presumably from the corresponding market.” Unlike defensive blocking patent applications, offensive patenting only occurs when a blocking patent application is actually granted. The authors write that, ”Offensive patenting is conceived to threaten, attack and weaken others. It can be used to prevent competitors from using a technology or to restrain their freedom to operate by filing patents at the margin of their areas of activity, for example surrounding high value patents with a screen of minor patents.” Defensive patent applications, on the other hand, largely function to keep the market open for the patent applicant in question to maneuver without being blocked by the patent applications of others.
- A Brief Note on Blocking Patents and Reverse Equivalents: Biotechnology as an Example, by Robert P Merges. This article covers the reverse doctrine of equivalents and the potential limits of blocking patents.
- Exclusion and Exclusive Use in Patent Law by Adam Mossoff. This article describes recent court decisions and their effect on legal nature of patents as constitutionally protected property with exclusionary rights.
- Used, blocking and sleeping patents: Empirical evidence from a large-scale inventor survey by Salvatore Torrisi, Alfonso Gambardella, Paola Giuri, Dietmar Harhoff, & Karin Hoisl. Information on patents and their strategic uses from a large scale survey of patent holders in US, Europe, and Japan.
- Study of blocking patents and many patents strategy by Japanese big companies by Yoshifumi Okuda and Yoshitoshi Tanaka found that 30% of patents filed by Japanese company were intended to cement first mover advantage in R&D.


So What Exactly is patent infringement?
Patent infringement. Big word, scary concept. But what does it mean?
When you hear about a company being sued for infringement, the important thing to understand is that infringement revolves around the violation of a principle. What principle? Someone reducing the ability of the wronged party to monetize their invention. Patents are all about my ability to profit for my invention by preventing you from doing the same.
According to United States law:
“whoever without authority makes, uses, offers to sell, or sells any patented invention, within the United States or imports into the United States any patented invention during the term of the patent therefor, infringes the patent”
(as defined in 35 U.S. Code § 271)
In plain language, this means that anyone who produces and/or profits from a patented invention in the U.S. can face litigation for patent infringement. In addition, anyone who imports an item into the U.S. that is manufactured in a way covered by an existing U.S. patent may be subject to litigation for patent infringement.
All this can usually be avoided if the importer makes sufficient material changes to that item or the item subsequently becomes a trivial and/or non-essential part of another item.
Now, another way businesses often encounter trouble is if they actively encourage others to infringe a patent (stealing a line of code to ship a product faster, for example) or by supplying others with or importing parts of a patented invention. (As an aside you must be extremely careful when importing products from foreign countries for this exact reason. You don’t want your products held by customs for patent infringement or over a trademark dispute)
The Types of Patent Infringement:
An instance of patent infringement is usually categorized as follows:
- Direct infringement: The directly infringing party makes, uses, offers to sell, or sells a patented invention without authorization from the patent owner.
- Induced infringement: The indirectly infringing party encourages or enables another party to infringe a patent.
- Contributory infringement: The contributorily infringing party provides a directly infringing party with a part that is used to produce an infringing item, where the contributed part has no significant non-infringing use.
- Literal infringement: The language of the accusing party’s patent claim corresponds directly, or is identical to the alleged infringer’s item or the processes thereof.
As you can see, someone can be subject to litigation for patent infringement without directly infringing a patent (or by filing a similar patent of their own). For more information on the different kinds of patent infringement, read more on litigation and infringement & types of infringement.
Patent Infringement Litigation
If a patent owner believes someone has infringed upon their patent, they may sue that person in a federal court of law. The patent owner’s lawsuit may demand that the accused party cease and desist their unauthorized use of the patent owner’s invention, as well as claim compensation for the accused party’s unauthorized use of the patent owner’s invention. The damages paid to a patent owner as a result of a successful lawsuit are either in the form of actual damages or reasonable royalty for the infringing use of their patented invention.
Actual damages cover profits that were lost to the patent owner as a direct result of the infringing action, while reasonable royalty is calculated according to factors such as the type of item patented, the time remaining on that item’s patent, other royalty arrangements, and any other relevant issues.
In certain cases, the patent owner will seek to have a preliminary injunction issued against the party accused of patent infringement, in order to bar them from their allegedly infringing activities while the lawsuit is in process. It is standard procedure for the court to issue a permanent injunction against the accused party should they be found culpable in violating a patent. A patent owner that wishes to sue for infringement of their patent must do so within six years of the alleged infringement.
The patent owner’s lawsuit will not succeed if the court finds:
- That the accused party doesn’t need a license to the patent
- That at least one of the patent owner’s patent claims is invalid
- That there are other reasons why the patent owner is not entitled to their demands
The most common defense against allegations of patent infringement is to argue that the accuser’s patent claims are invalid. According to the United States Patent and Trademark Office, “The court may conclude that the patent claim is not valid if it is shown that the claimed invention was disclosed in a prior patent or patents, a book, a magazine, a newspaper, a television show or movie, a web page or other published work before the date of the claimed invention… [or] if it is shown that the claimed invention was offered for sale in this country or was disclosed to the public more than one year before the application for the patent was filed.”
The accused party may also argue that their accuser’s patent is not valid by claiming that the patent falls short of meeting the required criteria of novelty and nonobviousness. The court may also find the patent to be invalid on the grounds that it fails to meet other statutory requirements—for example, if the written description of the patented invention is insufficient or does not describe something that is eligible for patent—or if the patent owner is proved to have provided the United States Patent and Trademark Office with false information in their patent application.
If you believe someone to have directly or indirectly infringed your patent, or if you have been accused of patent infringement, you should seek the assistance of a patent attorney to determine your best course of action. Get in touch with us if you’d like to learn more, or if you have fears that your intellectual property has been placed in jeopardy.