Preserving a Patent’s Validity During Litigation: Strategic Use of Post-Grant Amendment Procedures
It is not widely known that a patentee can amend granted claims through specific post-grant procedures to address invalidity arguments raised by a defendant, while still pursuing an infringement claim, even during an ongoing patent infringement lawsuit. In the United States and Korea, there is no direct mechanism for amending claims in the courts. However, one can file administrative actions with the competent patent offices—namely, the USPTO in the United States, or the Patent Tribunal (the Korean Intellectual Property Trial and Appeal Board in Korea, or the PTAB in the U.S.)—to refine and limit the scope of an already granted patent.
These amendment procedures are equally available even if a U.S. court has ultimately found the patent invalid or a Korean court has determined that the patent is highly likely to be invalid. In such circumstances, a patentee may petition for an amendment (or correction) before the relevant tribunal, seeking to narrow or reorganize the claims to effectively “overcome” an invalidity determination and potentially secure a newly tailored set of enforceable rights.
1. The U.S. Landscape
In the United States, courts presiding over infringement actions do not permit direct amendments to patent claims within the litigation itself. Once a judgment of invalidity becomes final (whether by a District Court, the ITC, or the Federal Circuit), it is binding between the parties, preventing the patentee from reasserting the same patent against the same party (Res Judicata, Collateral Estoppel). Although the court may notify the USPTO of the judgment, the patent is not automatically canceled. Instead, it is administratively marked as “invalid” for the parties in that case, limiting its enforceability against them going forward.
However, a final judgment of invalidity does not immediately extinguish the registration itself. The patentee may subsequently file a Reissue application or request an Ex Parte Reexamination before the USPTO to revise or rewrite the claims. Additionally, during Inter Partes Review (IPR) or Post-Grant Review (PGR), the patentee may submit a “Motion to Amend” to reasonably narrow the claims. Certain conditions must be met in these proceedings, including maintaining patentability over the prior art. While it is generally not feasible to revive the exact same invalidated claims, newly amended claims that constitute a substantially different invention compared to the prior art may confer fresh enforceable rights. Nonetheless, the patentee must factor in potential issues like Intervening Rights and Issue Preclusion.
2. The Korean Landscape
Korean courts cannot unilaterally invalidate a registered patent without a separate invalidation trial at the Korean Intellectual Property Trial and Appeal Board (KIPTAB). Nevertheless, a Korean court may evaluate potential invalidity during infringement litigation. If the defendant files an invalidation trial, the court can await the outcome, or if the patent’s invalidity appears manifest, the court may deny enforcement on the grounds of abuse of right (dismissing the infringement claim). The actual removal of a patent from the registry only occurs after an invalidation decision by the KIPTAB becomes final, at which point the patent is administratively canceled.
Because the court does not allow amendments to patent claims within the litigation, a patentee seeking to refine a granted patent must file a correction trial (정정심판) with the KIPTAB or, if an invalidation trial is already in progress, submit a request for claim correction in that proceeding. While the invalidation trial is pending, the court may, at its discretion, pause the infringement suit, giving the patentee time to fortify their claims.
3. Key Considerations for Challenging a Patent’s Validity
These amendment procedures (post-grant corrections) exist largely to give patentees a legitimate and reasonable defense when previously unchallenged prior art emerges. By revising the claims—provided they remain within the core inventive concept—a patentee may stave off a complete invalidation or reassert a narrower set of enforceable rights.
From the challenger’s perspective, assuming that “an issued patent will be automatically invalidated” can be hasty. If the patentee successfully amends the claims, the patent may become stronger against the prior art, hindering the challenger’s invalidation strategy. Therefore, a meticulous analysis of the prior art and the breadth of the claims—along with the patentee’s potential to amend—is essential for constructing an effective invalidation approach.
4. Conclusion
Filing an invalidation trial in parallel with an infringement lawsuit can be a powerful tactic for defendants, but patentees, too, can benefit by leveraging amendment procedures to preserve the patent’s validity and sustain infringement claims. Although courts in the U.S. and Korea do not directly permit claim amendments during litigation, effective use of post-grant proceedings in the USPTO or the relevant tribunal can keep an already granted patent alive. Even if the patent faces a strong invalidity challenge, timely and strategic correction or narrowing of the claims may enable a patentee to regain a favorable litigation position.
This article is intended solely to provide general information and does not constitute legal advice or a litigation strategy for any particular set of facts. Individuals or entities considering patent disputes or claim amendments should consult an intellectual property professional—an attorney or patent agent—to tailor an approach that meets the specific needs of their case.
