Claims are the most important part of a patent. They define the invention and put others on notice not to infringe. Patent claims can be directed to a composition, a method, a system, a formulation, or a machine. Patents usually have multiple claims of different scope.
Here’s an example of two composition claims from a Merck patent.
1.An isolated antibody or antibody fragment which binds to human PD-1 comprising:
a. three light chain CDRs of SEQ ID NOs: 15, 16 and 17; and/or
b. three heavy chain CDRs of SEQ ID NOs: 18, 19 and 20.
2. The antibody of claim 1, further comprising a human heavy chain constant region and a human light chain constant region, wherein the human heavy chain constant region comprises a γ4 or γ1 human heavy chain constant region or a variant thereof, wherein the constant region variant comprises up to 5 conservatively modified amino acid substitutions.
In claim 1, I highlighted three parts, a preamble, a transition, and a body. The preamble describes the invention and its purpose. The transition “comprising” is an open-ended term indicating that the claimed invention can have additional features. The body sets forth the metes and bounds of what is protected.
The body of claim 1 specifies the amino acid sequences that form the binding domain of the monoclonal antibody known as Keytruda, an immune checkpoint inhibitor for treating cancer. This is a relatively narrow claim that will not be infringed by an otherwise identical PD-1 antibody that has different CDR sequences. Even so, the claim is valuable because Keytruda is regulated by the FDA. Under FDA regulations, a biosimilar to Keytruda must have the same CDR sequences.
Claim 2 is a dependent claim that starts with a reference to claim 1. A dependent claim is narrower in scope than an independent claim. It requires all the limitations of the independent claim, plus the additional limitations of the dependent claim. Claim 1 is recognizable as an independent claim because its preamble does not refer to another claim.
Given the precise specificity of claim 1, you might wonder whether a competitor could avoid infringement by making a minor change such as a conservative amino acid substitution at the end of a CDR. This mutation would avoid direct infringement, but the competitor could still be held liable for infringing under a legal theory called the doctrine of equivalents. The doctrine of equivalents can be invoked if the claimed and accused products have the same function, work the same way, and achieve the same result.
The independent claim of the Cabilly patent shown here is much broader in scope than the Keytruda claim.
1. A method comprising
(a) preparing a DNA sequence encoding a chimeric immunoglobulin heavy or light chain having specificity for a particular known antigen wherein a constant region is homologous to the corresponding constant region of an antibody of a first mammalian species and a variable region thereof is homologous to the variable region of an antibody derived from a second, different mammalian species;
(b) inserting the sequence into a replicable expression vector operably linked to a suitable promoter compatible with a host cell;
(c) transforming the host cell with the vector of (b);
(d) culturing the host cell; and
(e) recovering the chimeric heavy or light chain from the host cell culture.
Cabilly claimed a method for expressing an antibody in a recombinant host cell. This is fundamental technology used by the entire therapeutic antibody industry. Genentech licensed the Cabilly patent to other pharmaceutical companies and earned billions of dollars in licensing revenue before the patent expired. The legal tactics Genentech used to maintain the Cabilly patent, which has limited experimental data, were impressive.
As a founder working on your first patent, you will have to provide the information your attorney will use to prepare a diverse set of claims. You should explain all the different ways your invention is distinguishable from the prior art, how competitors might try to invent around your patent, and what data you can provide to support claims with varying degrees of specificity and breadth. Claims of varying scope allow flexibility as you continue developing your lead. The broad claims will deter competitors from inventing around more specific claims. Diverse claim sets are also an asset in litigation where the validity of each claim is considered independently. If your broadest independent claim is invalidated, a dependent claim may survive.
