Responding to an IPR Petition: Technical Defence Strategies

When a patent comes under challenge through an Inter Partes Review (IPR) petition before the United States Patent Trial and Appeal Board (PTAB), patent owners face one of the most serious threats in US patent law. In our experience supporting clients through IPR proceedings, we've seen that successful defence requires a strategic combination of strong technical evidence, expert testimony, and procedural expertise to demonstrate that claims remain patentable over the cited prior art.1 With institution rates averaging 69% through FY2025 and final invalidity rates reaching 80% for instituted claims in recent final written decisions,23 patent owners must mount an aggressive, well-coordinated defence from the moment they receive an IPR petition.

This comprehensive guide focuses on the patent owner's defence perspective in US IPR proceedings, providing actionable strategies for responding effectively to IPR challenges through technical rebuttal, expert declarations, claim amendments, and secondary considerations evidence.

Understanding the IPR Challenge Framework

What the IPR Petition Alleges

An IPR petition challenges your patent's validity based solely on prior art patents and printed publications under 35 U.S.C. §§ 102 (novelty) and 103 (obviousness).3 The petitioner must demonstrate a "reasonable likelihood" that at least one challenged claim is unpatentable under 35 U.S.C. § 314(a)—a relatively low threshold that explains why the PTAB institutes approximately 69% of filed petitions in FY2025.45 This standard requires showing "there is a reasonable likelihood that the petitioner would prevail with respect to at least 1 of the claims challenged," which is distinct from the higher "compelling merits" standard used only in discretionary denial analysis.6

The petition will typically include detailed claim charts mapping prior art elements to your patent claims, expert declarations supporting the petitioner's obviousness theories, and arguments about how a person of ordinary skill in the art (POSITA) would have been motivated to combine multiple prior art references.7 Under 37 C.F.R. § 42.104(b)(4), petitioners must specify "where each element of the claim is found in the prior art patents or printed publications relied upon"—a requirement the USPTO has been strictly enforcing since September 2025, prohibiting reliance on "general knowledge" to fill gaps in prior art disclosures.8

Evaluating the Strength of Prior Art

The first task is conducting a thorough technical analysis of the cited prior art. We typically focus on identifying gaps between what the prior art actually teaches and what the petitioner claims it teaches.6 In our experience, common weaknesses in IPR petitions include:

• Missing claim elements: Prior art references that fail to disclose all claim limitations
• Improper combinations: Obviousness theories that lack adequate motivation to combine references
• Teaching away: Prior art that actually discourages the claimed invention, as demonstrated in Chemours Co. v. Daikin Industries (Fed. Cir. 2021), where the court found prior art taught away when it identified techniques for achieving a goal but discouraged their use for sound technical reasons9
• Conclusory expert opinions: Expert declarations lacking supporting evidence or data8

Critical Timeline and Deadlines

Preliminary Response Strategy (3 Months)

Patent owners have three months from the petition's filing date to submit an optional Patent Owner Preliminary Response (POPR).9 This 60-page document represents the only opportunity to prevent institution of the IPR.10 Key strategic considerations include:

When to File: File a preliminary response when you can identify strong statutory bars, clear missing claim elements, or significant flaws in the petitioner's obviousness analysis.11 Statistics show that while 62% of patent owners file preliminary responses, institution rates decrease by only 3%, suggesting careful selection of arguments is crucial.12

What to Include: Focus on procedural challenges (statutory bars, real party in interest issues), missing claim limitations, and teaching away arguments.13 The preliminary response cannot include new testimonial evidence or claim amendments.14

When to Waive: Consider waiving the preliminary response if your strongest arguments require expert testimony or if you prefer to reserve your best arguments for the patent owner response after institution.15

Patent Owner Response Timeline (3 Months Post-Institution)

After institution, you have three months to file your complete defence.16 Under 37 C.F.R. § 42.120(b), this deadline is firm and extensions are rare.17 Your response is limited to 14,000 words, matching the petition's word limit.18

Building Your Technical Defence

Expert Declaration Strategy

The expert declaration represents the cornerstone of any technical defence. The PTAB's precedential decision in Xerox Corp. v. Bytemark, Inc. (designated February 10, 2023) established that expert testimony lacking underlying facts or data "is entitled to little or no weight" under 37 C.F.R. § 42.65(a).19 The Board denied the IPR petition because the expert's declaration merely repeated the petitioner's assertions verbatim without providing technical reasoning or supporting evidence—particularly problematic when expert testimony is used to supply limitations missing from the prior art.20 We recommend that experts:

Analyse Each Prior Art Reference: Provide detailed technical analysis explaining why each cited reference fails to teach specific claim limitations.20 Avoid conclusory statements by supporting each opinion with objective documentary evidence such as contemporaneous treatises, technical articles, and industry publications.21

Address Combination Theories: Explain why a POSITA would not have been motivated to combine the cited references as proposed by the petitioner.22 Consider factors such as different technical fields, inconsistent teachings, or lack of reasonable expectation of success.

Establish Technical Context: Provide background on the state of the art at the relevant time, industry practices, and technical challenges that existed before your invention.23

Secondary Considerations of Non-Obviousness

Secondary considerations can provide "powerful, real-world indicator[s] of what would have been nonobvious."[24] The Federal Circuit has held that when secondary considerations evidence is present in the record, it must be considered and can often be "the most probative and cogent evidence."[25]

Commercial Success

To establish commercial success, you must demonstrate both the commercial success of products practicing your invention and a nexus between that success and the claimed invention's technical merits.26 The Federal Circuit's decision in Fox Factory, Inc. v. SRAM, LLC established that the presumption of nexus requires proving the commercial product is "essentially the claimed invention" with coextensive scope.27 More recently, Yita LLC v. MacNeil IP LLC (2023) tightened nexus requirements, holding that secondary consideration evidence lacks nexus when it "exclusively relates to a feature that was known in the prior art" rather than the inventive combination.28 However, the court relaxed nexus standards for licensing evidence in Ancora Technologies v. Roku (June 2025), finding licenses warrant a "looser" nexus standard as they are directly tied to patented technology.29

Evidence Requirements:

• Sales data and market share information
• Revenue and growth metrics
• Market acceptance evidence
• Expert analysis connecting success to claimed features28

Long-Felt Need and Failure of Others

Demonstrate that your invention addressed a long-standing problem in the field by providing:

• Evidence of industry recognition of the problem
• Documentation of failed attempts by others to solve the issue
• Technical literature discussing the challenges
• Expert testimony on the problem's duration and significance29

Industry Praise and Copying

Evidence of industry praise, licensing activity, and copying by competitors can strongly support non-obviousness arguments.30 The Federal Circuit in Volvo Penta of the Americas, LLC v. Brunswick Corp. clarified that market demand for unique features and copying by competitors can establish sufficient nexus even without perfect product-claim coextensiveness.31

Claim Amendment Strategy

When to Amend Claims

Under 35 U.S.C. § 316(d), patent owners may file a motion to amend claims during IPR proceedings.32 Consider amendments when:

• Original claims cannot be defended effectively against the cited prior art
• You can narrow claims to avoid problematic prior art while preserving commercially important scope
• You have additional dependent claims or embodiments not captured in the independent claims33

Amendment Requirements

Any motion to amend must satisfy strict requirements:

Scope Limitations: Amendments cannot enlarge claim scope or introduce new matter not supported by the original disclosure.34

Written Description Support: All amended claims must have adequate support in the original patent specification.35 The Federal Circuit has clarified that written description challenges in IPR context often arise through priority date disputes rather than direct § 112 invalidity grounds.36

One Motion Rule: Under 37 C.F.R. § 42.121, patent owners may file only one original motion to amend per proceeding, and only after conferring with the Board.37 This motion must be filed no later than the patent owner response deadline, unless otherwise specified by Board order.38

Burden Allocation: As of the 2024 rule changes, patent owners bear the burden of showing statutory compliance, while petitioners bear the burden of proving unpatentability of substitute claims.38

Cross-Examination and Oral Hearing Strategy

Deposing Petitioner's Expert

Approach expert depositions as cross-examination rather than discovery, since the expert's declaration already contains their primary testimony.39 Focus your questioning on:

Gaps in Supporting Evidence: Identify areas where the expert made conclusory statements without adequate factual support.40

Technical Inconsistencies: Explore contradictions between the expert's testimony and objective technical evidence.41

Narrow Scope: Avoid broad questions that allow the expert to supplement weak areas of their declaration.42

Oral Hearing Preparation

PTAB oral hearings provide an opportunity to address the panel directly, but demonstratives must comply with strict limitations.43 Under 37 C.F.R. § 42.70(b), your demonstratives:

• Cannot contain new evidence or arguments not previously presented
• Must be served on opposing counsel at least seven business days before the hearing
• Must be filed with the Board no later than three business days before the hearing
• Cannot rely on record evidence not previously cited in your papers44
• Must be clearly marked "DEMONSTRATIVE EXHIBIT – NOT EVIDENCE" in the footer45

Focus oral argument on the strongest technical arguments and emphasise real-world evidence supporting non-obviousness.45

Real Party in Interest and Standing Challenges

Strategic Use of RPI Challenges

Patent owners can challenge whether petitioners have properly identified all real parties in interest (RPI) under 37 C.F.R. § 42.8(b)(1).49 The PTAB applies the Taylor v. Sturgell framework, particularly the "assumption of control" exception, requiring that unnamed parties have exerted control over the IPR petition.50

Key Considerations:

• Financial interest or indemnification agreements alone are typically insufficient without evidence of control
• The Federal Circuit requires "a flexible approach" considering "equitable and practical considerations" and whether the non-party is a "clear beneficiary that has a preexisting, established relationship with the petitioner"[51]
• Successful RPI challenges can result in estoppel of unnamed parties under 35 U.S.C. § 315(e)52

Estoppel Strategy Benefits

RPI determinations carry significant estoppel consequences. After a final written decision, statutory estoppel applies to the petitioner, all real parties in interest, and anyone in privity with them, preventing future challenges on grounds they "raised or reasonably could have raised."[53] This makes RPI identification crucial for both immediate defence and future enforcement strategy.

Settlement Considerations and Timing

Settlement discussions should begin early in the IPR process, as the PTAB is more likely to approve joint termination requests filed before the panel has "decided the merits" under 35 U.S.C. § 317(a).46 Settlements represent approximately 70% of all IPR terminations, with historically twice as many IPRs settling as reaching final written decision.47 As of FY2025, the settlement rate was 29%, with 94 pre-institution and 147 post-institution settlements.48

Early Settlement Benefits:

• Preserves patent validity
• Avoids estoppel effects from adverse PTAB decisions
• Enables confidential resolution terms
• Reduces litigation costs48

Late Settlement Risks: The PTAB may deny joint termination motions filed near statutory deadlines, particularly after the panel has begun deliberating on the merits.49

Costs and Practical Realities

IPR Defence Cost Estimates

IPR defence represents a substantial financial commitment. Based on AIPLA Economic Survey data and industry benchmarks, patent owners should budget for the following:

Phase	Estimated Cost Range (USD)	Key Cost Drivers
Preliminary Response	$50,000–$150,000	Prior art analysis, initial claim construction, procedural challenges
Full Patent Owner Response	$150,000–$350,000	Expert declarations, secondary considerations evidence, claim amendments
Discovery and Depositions	$50,000–$100,000	Expert depositions, document production
Oral Hearing	$25,000–$75,000	Hearing preparation, demonstratives, travel
Total Through Final Written Decision	$275,000–$675,000	Varies significantly by case complexity

These estimates can increase substantially for complex technologies, multiple expert witnesses, or proceedings with extensive secondary considerations evidence development.

Factors Affecting Defence Costs

In our experience, the following factors most significantly affect IPR defence budgets:

• Number of claims challenged: More claims require more detailed technical analysis
• Complexity of prior art: More references mean more expert time analysing combinations
• Secondary considerations scope: Commercial success evidence often requires economic expert testimony
• Claim amendment strategy: Developing and supporting substitute claims adds cost
• Parallel litigation: Coordination with district court proceedings increases complexity55

Business Continuity Considerations

While defending an IPR, patent owners should consider:

• Licensing negotiations: Ongoing licensing discussions may be affected by IPR outcomes
• Enforcement strategy: District court proceedings may be stayed pending IPR resolution
• Portfolio implications: Challenge to one patent may affect perception of related patents
• Insurance coverage: Some policies cover IPR defence costs—check coverage terms early

Critical Mistakes to Avoid

Procedural Errors

Missing Deadlines: IPR deadlines are strictly enforced. We've seen cases where patent owners lost significant rights simply by missing the three-month response deadline. Calendar all deadlines immediately upon receiving notice of institution.

Exceeding Word Limits: The 14,000-word limit for patent owner responses is strictly enforced. Plan content carefully and prioritise arguments rather than trying to squeeze in everything.

Improper Evidence Submission: New evidence in reply briefs or oral hearings will be excluded. All substantive evidence must be in the patent owner response.56

Strategic Errors

Weak Expert Declarations: Following Xerox v. Bytemark, conclusory expert testimony carries little weight. Ensure every expert opinion is supported by objective evidence and technical reasoning. This is the single most common mistake we observe in unsuccessful defences.

Ignoring Secondary Considerations: Patent owners often focus exclusively on technical prior art arguments while neglecting commercial success, long-felt need, and copying evidence. These real-world indicators can be dispositive.

Overly Narrow Amendments: Claim amendments that preserve only minimal scope may win the IPR but leave commercially worthless claims. Balance prosecution history estoppel concerns against maintaining enforceable claim scope.

Premature Settlement: Settling before fully evaluating defence strength may leave value on the table. Conversely, waiting too long risks adverse decisions that affect future enforcement.

Evidence Development Errors

Inadequate Nexus Development: For secondary considerations, merely showing commercial success is insufficient. The connection between success and claimed features must be established—often requiring detailed expert testimony linking specific claim elements to commercial outcomes.57

Ignoring Petitioner's Expert Weaknesses: Thoroughly review the petitioner's expert declaration for conclusory statements, lack of supporting evidence, or technical errors. These weaknesses should be exploited in depositions and briefing.

Late Secondary Considerations Evidence: Begin gathering commercial success and industry recognition evidence immediately. Waiting until after institution significantly limits evidence development time.

Recent Developments Affecting Defence Strategy

2024-2025 Rule Changes

The USPTO implemented several changes benefiting patent owners:

Motion to Amend Improvements: New rules provide opportunities for preliminary PTAB guidance on proposed claim amendments before final decisions.50

Enhanced Expert Standards: The PTAB continues emphasising that expert testimony must be supported by objective evidence following the precedential Bytemark decision.51

Federal Circuit Trends

Recent Federal Circuit decisions have clarified several issues favourable to patent owners:

SoftView v. Apple (2024): Patent owner estoppel applies only to new and amended claims, not previously issued claims.52

Centripetal Networks v. Palo Alto Networks (2025): PTAB must adequately consider copying evidence and secondary considerations.53

IPR Defence Timeline

Phase	Deadline	Key Activities
Preliminary Response	3 months from petition filing	Optional 60-page response; statutory bars, missing elements, teaching away
Institution Decision	6 months from petition filing	PTAB decides whether to institute; focus shifts to merits
Patent Owner Response	3 months from institution	14,000-word response with expert declarations, amendments, secondary considerations
Petitioner Reply	3 months after PO response	Address patent owner arguments; opposition to amendments
Patent Owner Sur-Reply	1 month after petitioner reply	Limited response to new arguments in reply
Oral Hearing	Upon request	Final opportunity to argue before PTAB panel
Final Written Decision	18 months from institution	PTAB's final validity determination

Secondary Considerations Evidence Checklist

Commercial Success

• Sales data and revenue figures
• Market share documentation
• Growth metrics and projections
• Evidence connecting success to claimed invention (nexus)
• Expert analysis of commercial performance

Long-Felt Need

• Industry publications discussing the problem
• Technical literature documenting challenges
• Evidence of duration of the need
• Failed attempts by others to solve the problem

Failure of Others

• Documentation of unsuccessful competing solutions
• Technical reasons for others' failures
• Timeline showing persistent industry challenges
• Expert testimony on technical difficulties

Industry Recognition

• Awards and industry recognition
• Technical publications praising the invention
• Licensing agreements and terms
• Adoption by industry leaders

Copying and Designing Around

• Evidence of competitors copying the invention
• Attempts by others to design around claims
• Industry analysis of competitive responses
• Patent prosecution activity by competitors

Key Takeaways for Effective IPR Defence

1. Early Assessment is Critical: Immediately evaluate the technical merits of the IPR petition and identify the strongest defence arguments.

2. Expert Evidence Must Be Robust: Ensure expert declarations are supported by objective technical evidence and avoid conclusory statements.

3. Secondary Considerations Provide Real-World Context: Commercial success, long-felt need, and copying evidence can be more persuasive than technical arguments alone.

4. Strategic Amendment Decisions: Carefully weigh the benefits of claim amendments against the risks of scope reduction and estoppel.

5. Settlement Timing Matters: Early settlement discussions provide more options and avoid adverse PTAB decisions.

6. Procedural Compliance is Essential: Strict deadlines, word limits, and evidence requirements leave no room for procedural errors.

Conclusion

Defending an IPR petition successfully requires a comprehensive strategy combining strong technical analysis, persuasive expert testimony, and strategic use of secondary considerations evidence. With institution and invalidity rates remaining high, patent owners must approach IPR defence as a bet-the-patent proceeding requiring the highest level of preparation and advocacy.

The key to success lies in early identification of technical weaknesses in the petitioner's case, development of robust rebuttal evidence, and strategic decision-making about claim amendments and settlement timing. By following the framework outlined in this guide and maintaining focus on both technical merit and procedural compliance, patent owners can maximise their chances of preserving patent validity against IPR challenges.

For additional background on IPR proceedings generally, see our companion article on Understanding Inter Partes Review: A Complete Guide for Patent Owners.

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Sources

[1] 37 C.F.R. § 42.220, Patent owner response requirements 2 USPTO PTAB AIA Trial Statistics, FY2025 YTD through January 2025 - 69% institution rate 3 PTAB Statistics for Final Written Decisions, December 2024-January 2025 - 80% cancellation rate, Mondaq (2025) 4 35 U.S.C. § 311(b), Grounds for inter partes review 5 35 U.S.C. § 314(a), Institution of inter partes review - "reasonable likelihood" standard 6 PTAB Litigation Blog, "Will Compelling Merits Institution Standard Lead To Rubber Stamp FWDs?" (2025) 7 37 C.F.R. § 42.104(b), Requirements for inter partes review petition 8 USPTO enforcement of 37 C.F.R. § 42.104(b)(4), prohibition on general knowledge, effective September 2025 9 Chemours Co. FC, LLC v. Daikin Industries, Ltd., Fed. Cir. 2021 (teaching away doctrine) 10 Trial Practice Guide, USPTO PTAB, November 2019, https://www.uspto.gov/sites/default/files/documents/tpgnov.pdf 11 Venable LLP, "IPR Spotlight Series: Evaluating Whether to File a Preliminary Patent Owner Response" (2014) 12 37 C.F.R. § 42.107, Patent owner preliminary response 13 USPTO PTAB Trial Practice Guide, preliminary response procedures 14 37 C.F.R. § 42.107(c), Content of preliminary response 15 Strategic considerations for preliminary response filing, based on industry practice 16 37 C.F.R. § 42.120(b), Patent owner response deadline 17 35 U.S.C. § 316(a)(11), Timeline for inter partes review 18 37 C.F.R. § 42.24, Type-volume limits for IPR filings 19 Xerox Corp. v. Bytemark, Inc., IPR2020-00019 (precedential decision, Feb. 10, 2023) - expert testimony standards 20 Baker Botts, "PTAB Precedential Decision on Conclusory Expert Testimony" (August 2024) 21 Mintz, "Patent Owner Tip #6: Using Objective Sources & Evidence to Support Expert Declarations" 22 McGuire Woods, "Perfecting Expert Testimony at PTAB" (2025) 23 Technical rebuttal strategies for combination theories, based on PTAB precedent 24 Expert declaration best practices for IPR defence 25 Graham v. John Deere Co., 383 U.S. 1 (1966) 26 Federal Circuit precedent on secondary considerations importance 27 MPEP § 716.03, Commercial success requirements 28 Fox Factory, Inc. v. SRAM, LLC, Fed. Cir. 2019 (nexus requirements) 29 Yita LLC v. MacNeil IP LLC, 69 F.4th 1356 (Fed. Cir. 2023) (tightened nexus standards) 30 Ancora Technologies, Inc. v. Roku, Inc., Fed. Cir. June 2025 (relaxed nexus for licensing evidence) 31 MPEP § 716.01(a), Objective evidence of nonobviousness 32 Secondary considerations case law compilation 33 Volvo Penta of the Americas, LLC v. Brunswick Corp., Fed. Cir. 2023 34 35 U.S.C. § 316(d), Amendment of patent during review 35 Strategic considerations for claim amendments in IPR 36 37 C.F.R. § 42.121, Amendment requirements 37 Written description support requirements for amendments 38 Baker Botts, "35 U.S.C. § 112 in IPR: Priority Chain Analysis" (February 2025) 39 37 C.F.R. § 42.121, Amendment of the patent - one motion rule 40 37 C.F.R. § 42.121(a)(3), Motion to amend filing deadline requirements 41 USPTO Final Rule on Motions to Amend, September 2024 42 Mintz, "Patent Owner Tip #1: Approach IPR Depositions Like Cross-Examination" 43 JD Supra, "Patent Owner Tip #2: Don't Swing for the Fences in IPR Depositions" 44 Expert deposition strategy for patent owners 45 Venable LLP, "IPR Spotlight Series: Top 5 IPR Discovery Tips for Patent Owners" 46 37 C.F.R. § 42.70, Oral hearing procedures 47 37 C.F.R. § 42.70(b), Demonstrative exhibit filing deadlines 48 PTAB Hearing Guide, demonstrative marking requirements 49 37 C.F.R. § 42.8(b)(1), Real party in interest identification requirement 50 Taylor v. Sturgell, 553 U.S. 880 (2008) - framework for nonparty preclusion exceptions 51 Applications in Internet Time, LLC v. RPX Corp., Fed. Cir. 2018 (RPI determination standards) 52 35 U.S.C. § 315(e), Estoppel provisions for real parties in interest 53 35 U.S.C. § 315(e)(1), Estoppel from maintaining proceedings on raised/raisable grounds 54 35 U.S.C. § 317(a), Termination of review 55 Foley & Lardner, "Inter Partes Review – Parties Favor Settlement Over Board Decisions" (2014) 56 USPTO PTAB AIA Trial Statistics, FY2025 settlement rates through May 2025 57 PTAB Litigation Blog, "Settlement Does Not Necessarily End An IPR Or PGR" 58 USPTO Final Rule on Motions to Amend Practice, 89 Fed. Reg. 75084 (Sept. 18, 2024) 59 PTAB precedential decisions on expert testimony standards 60 SoftView LLC v. Apple Inc., Fed. Cir. 2024 (patent owner estoppel scope) 61 Centripetal Networks v. Palo Alto Networks, Fed. Cir. 2025 (secondary considerations analysis) 62 AIPLA 2023 Report of the Economic Survey, IPR proceeding cost benchmarks 63 37 C.F.R. § 42.23, Timing of reply briefs and new evidence restrictions 64 Federal Circuit guidance on nexus requirements for secondary considerations

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Legal Disclaimer: This article provides general information about IPR defence strategies and should not be construed as legal advice. Patent owners facing IPR challenges should consult with qualified patent attorneys to develop case-specific defence strategies. The law and PTAB practices continue to evolve, and practitioners should verify current requirements and deadlines.