Post-Grant Review (PGR) and Inter Partes Review (IPR): Strategies for Patent Invalidation

6. Strategies for Successful Patent Invalidation Using PGR and IPR 

Challenging a granted patent requires a well-prepared strategy, strong prior art, and legal expertise. Below are key approaches to maximize the chances of invalidating a patent through these proceedings. 

1. Prior Art Search – The Foundation of a Strong Challenge 

A well-executed prior art search is critical for IPR and still highly valuable for PGR. It helps identify existing patents, publications, or technical papers that invalidate the granted patent’s claims. 

How to Strengthen Your Case with Prior Art: 
✅ Use AI-driven tools like PatDigger LLM or XLSCOUT’s Novelty Checker to discover previously overlooked prior art. 
✅ Identify foreign patents and non-patent literature that the examiner may have missed. 
✅ Find expired patents with similar claims to argue lack of novelty. 

Example: 

• In Google v. Personal Audio LLC (IPR2014-00070), Google successfully invalidated Personal Audio’s podcasting patent by citing a 1996 patent application that predated the claims, proving lack of novelty. 

2. Target Weak Patent Claims & Overly Broad Language 

Patents with broad, ambiguous claims are easier to challenge under both PGR and IPR. 

Best Practices: 
✅ Focus on functional claim language that lacks specificity. 
✅ Identify claims that do not explicitly define a novel feature. 
✅ Use expert declarations to show how the claims are obvious to a skilled person in the field. 

Example: 

• In Apple v. VoIP-Pal (IPR2016-01201), Apple argued that VoIP-Pal’s broad voice-over-internet patents covered generic functions already known in prior art. The PTAB ruled that the claims were too broad, leading to invalidation. 

3. Exploit Section 112 Challenges in PGR

Since PGR allows challenges under §112 (written description and enablement), it’s a powerful strategy against patents with insufficient disclosure. 

Key Targets: 
✅ Claims that lack sufficient technical description to enable reproduction. 
✅ Overclaimed patents where the specification does not fully support all claims. 

Example: 

• In Momenta Pharmaceuticals v. Bristol-Myers Squibb (PGR2018-00033), the PTAB ruled that BMS’s anticoagulant drug patent lacked adequate written description, invalidating key claims. 

4. Use Technical & Economic Expert Testimony 

Expert technical declarations and economic analysis can provide strong evidence to support patent invalidation. 

How to Use Expert Testimony: 
✅ Show how the claims overlap with known technologies. 
✅ Use economic impact analysis to demonstrate that enforcing the patent would create an unfair monopoly. 

Example: 

• In Samsung v. Smartflash (IPR2015-00056), Samsung leveraged multiple expert reports to prove that Smartflash’s patents on digital rights management were obvious based on prior patents, leading to their invalidation. 

5. File IPR to Challenge Competitor Patents and Avoid Infringement Risks 

Companies often use IPR strategically to eliminate competitor patents before entering the market. 

Best Practices: 
✅ Conduct freedom-to-operate (FTO) searches to identify patents that could block your product. 
✅ File IPR before potential litigation, reducing legal risks. 
✅ Monitor competitor patent filings and challenge them proactively. 

Example: 

• In Ford v. Paice LLC (IPR2015-00758), Ford preemptively challenged hybrid vehicle patents owned by Paice, reducing infringement risks before launching its own hybrid models.