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Comparing Patent Linkage Systems in the US, China, and Singapore

14 May 2025

Patent linkage systems play a key role in protecting pharmaceutical patents, particularly for innovator drugs facing competition from generics or biosimilars. These systems link the approval of generics to the patent status of the original product, providing a framework that balances public interest and patent protection.

The US has had a well-established system for decades. China introduced a similar framework in 2021, while Singapore has implemented a simpler version. Here's how these three jurisdictions compare, and what pharma and biotech companies need to know.
 
What Is Patent Linkage?
In simple terms, patent linkage means regulatory approval for generics or biosimilars depends on the patent status of the reference drug. If a valid patent exists, the regulator may:

  • Notify the patent owner of the generic application;

  • Delay approval until the patent expires or is invalidated; and/or

  • Reject the application altogether.

Patent linkage provides a mechanism for innovator companies to assert their rights before the marketing of an allegedly infringing product. At the same time, it gives generic companies greater certainty in planning their marketing strategies and helps avoid potential damages if a commercialized product is later found to infringe. It also offers generics a pathway to challenge patents or certify non-infringement.

Each jurisdiction’s patent linkage system varies in scope, administrative burden, and legal certainty.
 
United States: The Orange Book
The US system, established under the Hatch-Waxman Act (1984), is widely regarded as the gold standard for patent linkage.

The FDA maintains the Orange Book, which lists approved chemical drugs and their relevant patents (e.g., active ingredients, formulations, uses, but not manufacturing processes or packaging).

Generic applicants, when filing an FDA application for drug approval, must submit a certification that:

  1. No patent information has been listed in the Orange Book ("Paragraph I certification");

  2. The patent has expired ("Paragraph II certification");

  3. The product will not be marketed until the patent expires ("Paragraph III certification"); or

  4. The patent is invalid, unenforceable, or will not be infringed by the generic applicant ("Paragraph IV certification").

A Paragraph IV certification triggers a 45-day window for the innovator to sue. If they do, the FDA imposes a 30-month stay on final approval, allowing litigation to proceed before the generic enters the market. If there is no court decision after the 30-month mark, and assuming no FDA approvability issues, the generic can come to market.

While comprehensive, the US system faces criticism over “over-listing” patents. The FDA now allows challenges to improper listings.
 
China: The Emerging System Post-RCEP
China’s patent linkage system launched in 2021, driven by commitments under Regional Comprehensive Economic Partnership (RCEP).

Similar to the Orange Book, relevant Chinese patent information is listed in a public platform managed by the National Medical Products Administration (NMPA). Patents covering the following can be listed:

  • Chemical drugs: Active ingredients, formulations, and medical uses;

  • Biologics: Sequence and medical uses;

  • Traditional Chinese Medicines: Extracts, formulations, and medical uses.

Currently, there is no mechanism to challenge the improper listing of patents.

Unlike the US, patent listing is not mandatory in China. However, only listed patents can be enforced under the patent linkage system during regulatory approval. If a patent is not listed, the innovator can only assert rights after the generic is commercialized.

Generic applicants, when filing an application with the NMPA, must submit a declaration similar to the four types of certifications in the US.

A Type IV declaration triggers a shorter 9-month stay for chemical drugs if the innovator files suit within 45 days.
 
Singapore: A Simplified but Limited System
Singapore has adopted a more streamlined approach without a centralized patent listing system. The onus is on generic applicants to identify any patents that may be relevant to their drug approval request submitted to the Health Sciences Authority (HSA).

Similar to the US and China, Singapore uses the following four categories of declarations:

  1. No relevant patent (Category A1);

  2. A relevant patent is in force, and the generic applicant is the owner or has obtained consent from the patent owner (Category A2);

  3. A relevant patent is in force, and the generic will not be marketed until the patent expires (Category A3);

  4. A relevant patent is in force, but the patent is invalid or will not be infringed by the generic applicant (Category B).

A Category B declaration gives the innovator 45 days to sue, triggering a 30-month stay. If the court rules in favor of the patentee, HSA halts approval until the patent expires.

Singapore’s system imposes fewer administrative burdens, particularly for patent holders, but offers less transparency and certainty compared to the US and China.
 
Final Thoughts: Strategic Implications
Each jurisdiction has its own strengths and limitations. Understanding these differences is key to developing a globally coordinated patent and market entry strategy.

Pharma and biotech innovators should proactively manage patent linkage risks by listing patents early (where applicable), monitoring regulatory filings by generics, preparing for timely enforcement if notified, and working closely with local counsel to navigate different systems.