Broad patent protection for cutting edge biotech

Researchers working at the cutting edge of biotechnology occasionally make breakthroughs that open up a new field or overcome an intractable problem. An innovator making an advance of this kind will often want to obtain broad patent coverage so that it can benefit when others use the technology commercially.

But broad patent  coverage can lead to its own problems. In Europe, patent claims that are very broad in scope can fail on the ground of insufficiency. In essence, this means that the disclosure provided in the patent is not enough to enable others to carry out the invention themselves, or at least, not across the whole breadth of the claimed invention.

Invalidity ruling overturned

A recent decision of the UK Court of Appeal shows the tension between broad claiming and full support for the claims. Fortunately for the patent owner, Regeneron, Inc., the Court of Appeal overturned a trial judge’s decision to declare the patent invalid. The Court of Appeal instead took the same view as the European Patent Office and decided that the claims were valid even though a key example in the patent did not work.

The "reverse chimeric locus"

The case involved a dispute between Regeneron Pharmaceuticals, Inc and Kymab Ltd over the production of antibodies using transgenic mice. It was already known that mice could be used to produce fully human antibodies by replacing their own immune genes with human antibody genes. But these transgenic mice  have a reduced immune response. 

Regeneron’s technique addressed this problem by producing transgenic mice with a “reverse chimeric locus” comprising human variable regions with mouse constant regions. Antibodies made using this technology could then be engineered to change the mouse constant regions to human, with a fully human antibody as the result. They achieved this through use of a large targeting vector, or LTVEC, made in a bacterial host.

Enough for the skilled team?

The trial judge felt that the disclosure provided by the patent did not give the skilled team enough to work the invention. A key example in the patent could not be made to work, and the amounts of sequence to be deleted and inserted were too large to be carried out with the methods described. He said:

“The task contemplated was unprecedented and could not have been achieved, if at all, without a great deal of creative thinking at the priority date. I do not accept that all embodiments within the claim are unified by a single principle of a reverse chimeric locus. This is not a principle that enables the method to be performed, rather it is the result of successfully carrying out the method.”

The Court of Appeal disagreed. Looking back over earlier patent cases, and particularly those involving biotech inventions, they felt that the step forward provided by the ideas disclosed did justify broad claims:

“…we have come to the conclusion that claim 1 of the 163 patent does not exceed the contribution to the art which the disclosure of its specification has made. We are satisfied that the extent of the patent monopoly, as defined by claim 1, does correspond to that technical contribution to the art and that it is adequately enabled across its scope.”

The manipulation needed to get the invention to work – reducing the size of the inserts, and carrying out necessary deletions later on – would have been an obvious way forward for the appropriately skilled team.

Alignment with European approach

The Court of Appeal referred to a number of European Patent Office cases as well as UK cases in its analysis. The judgment notes that the decision is consistent with the EPO’s rulings on Regeneron’s patents – seemingly a conscious effort to demonstrate alignment with the EPO approach to the difficult sufficiency question.

Our content explained

Every piece of content we create is correct on the date it’s published but please don’t rely on it as legal advice. If you’d like to speak to us about your own legal requirements, please contact one of our expert lawyers.

Posted by


Mills & Reeve Sites navigation
A tabbed collection of Mills & Reeve sites.
My Mills & Reeve navigation
Subscribe to, or manage your My Mills & Reeve account.
My M&R


Register for My M&R to stay up-to-date with legal news and events, create brochures and bookmark pages.

Existing clients

Log in to your client extranet for free matter information, know-how and documents.


Mills & Reeve system for employees.