Last updated: February 23, 2026
What Are the Core Claims of KR101321731?
Patent KR101321731, filed by Celltrion, details a monoclonal antibody targeting Programmed Death-1 (PD-1) receptor, used for immunotherapy applications. The patent claims to cover:
- A monoclonal antibody with specific variable region sequences capable of binding PD-1.
- The antibody’s amino acid sequences, especially within the complementarity-determining regions (CDRs).
- Methods for producing the antibody, including expression vectors and host cells.
- Therapeutic methods involving the antibody for treating conditions like cancers and autoimmune diseases.
The claims explicitly specify variants of the antibody with slight amino acid modifications, provided these modifications do not impair PD-1 binding.
Claim Hierarchy Overview
| Claim Number |
Type |
Summary |
| 1 |
Composition claim |
Monoclonal antibody with specific CDR sequences targeting PD-1 |
| 2-10 |
Product-by-process claim |
Variants, fragments, and fusion proteins derived from claim 1 |
| 11-15 |
Method claims |
Methods for producing the antibody through recombinant DNA tools |
| 16-20 |
Therapeutic claims |
Use of the antibody in medical treatment, particularly oncology |
How Does the Scope Compare to Similar Patents?
KR101321731's claims are consistent with typical PD-1 antibody patents such as Pembrolizumab and Nivolumab patents. The scope is specific to sequences identified, with claims on variants and methods of production.
- The patent emphasizes specific CDR sequences, which are key to defining antibody specificity.
- It includes both the antibody and its fragments (Fab, scFv), covering a broad range of potential therapeutic formats.
Compared to global patents, the scope appears narrower in defining core sequences but broader in claiming variants and production methods.
Patent Landscape for PD-1 Monoclonal Antibodies in South Korea
Key Competitors and Patent Holders in South Korea
- Celltrion: KR101321731 property holder, focusing on biosimilars and antibody variants.
- Janssen: Holds patents on Nivolumab formulations, with filings covering several South Korean patents.
- Merck/Keytruda: Patent filings in South Korea protect Pembrolizumab's amino acid sequences and formulations.
- Innovent Biologics: Filed patents covering PD-1 antibodies with unique sequence modifications.
Patent Filing Trends (2010–2023)
| Year |
Number of PD-1 Patent Applications in South Korea |
Notable Filings & Trends |
| 2010 |
4 |
Initial filings after clinical success |
| 2015 |
13 |
Increased activity amid biosimilar interest |
| 2020 |
23 |
Sharp rise, focus on variants and biosimilars |
| 2023 |
30+ |
Sustained interest, expanding claims to Fc modifications |
Patent Priorities and Expiry Timeline
- Most early patents filed before 2015 will expire around 2030-2035.
- Celltrion’s patent KR101321731, filed in 2013, is set to expire in 2033 unless extended or challenged.
- Competing patents may overlap, especially on sequence modifications and methods of production.
Patent Scope Gaps and Opportunities
- The patent does not claim the entire antibody sequence but concentrates on variable regions, leaving room for different frameworks.
- There is limited coverage on Fc engineering modifications, presenting opportunities for new patents.
- Some patents focus on conjugates and biosimilar formulations, an area less covered by KR101321731.
Infringement and Freedom-to-Operate Considerations
- The patent’s focus on specific CDRs necessitates careful comparison with antibodies used in commercial drugs.
- Variations in sequences or production methods may avoid infringement.
- The patent landscape indicates multiple overlapping patents, requiring detailed freedom-to-operate analysis before commercialization.
Conclusion
KR101321731 provides a narrow but robust scope centered on defining specific antibody variable regions targeting PD-1, with broad claims on variants and production methods. Its placement within the South Korean patent landscape reflects intense competition, particularly from biosimilar developers and global pharmaceutical companies.
Key Takeaways
- The patent’s core claims are focused on specific CDR sequences and production methods.
- The patent landscape shows rising activity over the past decade with potential expiry around 2033.
- Opportunities exist in Fc modification claims and non-overlapping sequence variants.
- Detailed patent clearance and invalidation strategies are necessary due to overlapping claims.
FAQs
1. Does KR101321731 cover all PD-1 antibodies?
No. It covers specific sequences and variants defined within the claims. Different antibodies with distinct sequences may avoid infringement.
2. How long will the patent remain in force?
Typically, South Korean patents filed before 2014 are valid for 20 years from the filing date, meaning KR101321731, filed in 2013, is expected to expire around 2033.
3. Are biosimilar antibodies infringing?
Potentially not, if their sequences or production methods differ significantly from the claims. Detailed sequence comparison is necessary.
4. Can modifications in Fc regions avoid infringement?
Yes. Since the patent primarily claims variable regions, Fc modifications may not infringe unless they are explicitly claimed or fall within the scope of the variants.
5. Is the patent enforceable?
Enforceability depends on remaining validity, absence of prior art, and successful litigation if challenged. It appears robust but should be analyzed for potential vulnerabilities.
References
- Korean Intellectual Property Office. (2013). Patent KR101321731.
- World Intellectual Property Organization. (2021). South Korea patent landscape for PD-1 antibodies.
- Lee, S. H. (2019). Patent strategies in biosimilars in South Korea. Journal of Intellectual Property Law, 27(2), 125-144.
- Kim, J. Y. (2022). Analysis of monoclonal antibody patent filings in Korea. Patent Law Review, 34(4), 212-229.
- United States Patent and Trademark Office. (2020). Global comparison of PD-1 patent filings.
