Introduction
Monoclonal antibodies remain one of the most commercially valuable classes of biologics, yet obtaining robust patent protection for them in China requires a precise understanding of the China National Intellectual Property Administration's (CNIPA) evolving examination standards. This article aims to clarify how claims must be drafted, how novelty and inventiveness are assessed, and which formalities must be observed for applications relating to antibodies. Below is a concise roadmap that reflects CNIPA's current practice into practical advice for companies, universities, and patent attorneys.
- Claim Language – Two Acceptable Paths
CNIPA accepts two alternative formats for antibody claims, i.e. the antibody can be defined by its structure or the hybridoma which produces the antibody. The applicant could choose the one that best aligns with the available experimental data.
Option A – Structural Definition
The antibody is defined by the amino-acid sequences of its complementarity-determining regions (CDRs).
Example: "A monoclonal antibody against antigen A, comprising a heavy-chain variable region (VH) CDR1, CDR2 and CDR3 having the amino-acid sequences of SEQ ID NOs: 1–3, and a light-chain variable region (VL) CDR1, CDR2 and CDR3 having the amino-acid sequences of SEQ ID NOs: 4–6."
This format is appropriate when full sequencing data are available and variability outside the CDRs is not relied upon for patentability.
Option B – Hybridoma Definition
The antibody is defined by the deposited biological material that produces it.
Example: "A monoclonal antibody against antigen A, produced by the hybridoma deposited under CGMCC No. XXX."
You may use this route when the exact CDR sequences have not been determined or when the hybridoma itself is the inventive contribution.
- Novelty – Antigen-Driven Analysis
If antigen A itself is new, the monoclonal antibody against it is deemed novel.
However, if A is merely a variant of a known antigen A′ that shares the same epitope, the monoclonal antibody will be presumed NOT novel unless you can demonstrate that the claimed antibody is different from the antibody disclosed in prior art. Thus, if your antigen is a splice variant or point-mutant of a known molecule, prepare comparative binding or neutralization data to rebut the presumption of lack of novelty.
- Inventiveness – The "Structural Leap" Test A monoclonal antibody can be inventive if the following three cumulative conditions are met:
1) Its key functional sequences (typically the CDRs) differ significantly from all previously disclosed antibodies against the same antigen.
2) The prior art offers no teaching or suggestion that would lead a skilled person to the claimed sequences.
3) The antibody confers "beneficial technical effects," e.g., higher affinity, unique epitope specificity, improved safety profile, or unexpected cross-reactivity.
If the antigen is known and it is clear that the antigen is immunogenic (for example, the polyclonal antibody against the antigen is known or the antigen is a large polypeptide, which indicates that the antigen is obviously immunogenic), then an invention involving a monoclonal antibody defined only by the antigen does not involve an inventive step. However, if the invention is further defined by a hybridoma that secretes a monoclonal antibody against the antigen, and thereby produces an unexpected technical effect, then the invention of the monoclonal antibody involves an inventive step.
- Additional Formalities and Disclosure Requirements
For patent applications directed to antibodies, the specification should include characterization of the antibody (amino acid sequence, or if it is hybridoma-specific and the specific sequence is unknown, the deposit information is required), the preparation of the antibody, and experimental data on the effect or use.
For methods of preparing monoclonal antibodies, the method of obtaining or preparing the immunogen, the immunization method, the method of selectively obtaining antibody-producing cells, or the method of characterizing the monoclonal antibody should be described.
Deposit obligations:
When the invention involves a specific monoclonal antibody (for example, a specific binding constant is used to describe its affinity for antigen A), the hybridoma should be deposited with a depository in accordance with relevant regulations, unless the applicant can provide sufficient evidence to prove that a person skilled in the art can repeatedly prepare hybridomas based on the description.
Conclusion
China's patent framework for antibodies is stringent but predictable once the rules are understood. By choosing the correct claim format, marshalling comparative data to overcome novelty objections, and embedding the antibody's structural and functional novelty in the inventiveness narrative, applicants can secure enforceable rights that withstand post-grant challenges. Early alignment of experimental work with CNIPA's disclosure and deposit requirements will facilitate prosecution and maximize the commercial benefits of the resulting patents.
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.
