Articles
The Antibody Series #1 Quality Characteristics (CQAs) in Antibody Claims: When the Test Method Can Remain Outside the Claim
Januar 2026
Introduction
Therapeutic antibodies are at the heart of innovations in biotechnology and healthcare. With increasing regulatory requirements and quality expectations, critical quality attributes (CQAs) are becoming essential in the drafting of patent claims for biological products. Understanding how to incorporate these parameters into an IP protection strategy is now essential.
Why is this issue becoming more prevalent?
The number of cases related to antibodies and quality attributes is increasing for two main reasons:
- Growing complexity of biologics: Antibodies are no longer defined solely by their sequence; their physicochemical properties directly influence their efficacy and safety.
- Regulatory pressure and competitive differentiation: Companies seek to protect specific characteristics (such as oxidation or deamidation thresholds) to secure their competitive advantage.
These trends make CQAs an essential topic for patent protection strategies in the field of antibodies and biologics.
The EPO Boards of Appeal (BoA) are the appeal body that reviews decisions made by the European Patent Office. Here, they reviewed the rejection of a patent application for an antibody.
The real case: you are developing an anti-IL-5 antibody; your key differentiator is its quality attributes, in particular its oxidation and deamidation levels; you are seeking to protect this by including percentage thresholds directly in claim 1.
Claim 1:
“1. A composition comprising:
(a) an anti-IL-5 antibody comprising a heavy chain sequence as shown in SEQ ID NO: 1 and a light chain sequence as shown in SEQ ID NO: 2; and
(b) a variant of the antibody wherein residue N31 of the light chain is deamidated to aspartic acid or iso-aspartic acid,
wherein the composition comprises 3% or less oxidized antibody variant at W52 of the heavy chain amino acid sequence, 50% or less oxidized antibody variant at M64 of the heavy chain amino acid sequence, and 20% or less deamidated antibody variants at N31 of the light chain amino sequence.”
The beginning of the story: the examination division refused the application for lack of clarity; it considered that the claim was defined by “unusual parameters” and argued that the measurement methods were neither in the claim nor in the general knowledge of the art.
The BoA’s teaching: the Board did not follow the idea that “% of oxidized variants” and “% of deamidated variants” would be “unusual parameters” in this context; it treated them as a structural way of characterizing antibody compositions, rather than as a parameter with no recognized meaning for the skilled person.
On measurement, the Board found that it was not justified to require claim 1 to refer to the method of measurement; it relied on the fact that detailed and commonly used methods for measuring these variants existed in the field, and that there was no evidence that competing methods would lead to different values.
Practical drafting tip: if the competitive advantage of your antibody lies in measurable quality attributes, you can sometimes define the product by these percentages without including the test method in the claim; your position is strongest when the parameter corresponds to a recognized structural characterization and when the measurement approach is well established rather than contested. Be aware that alternative methods may exist that could lead to different measured values!
Disclaimer: This is not legal advice; it is only a practical outline to be discussed early on, before filing.
Source: ECLI:EP:BA:2024:T181522.20241212.
