A challenger's assault on a blocking pharma patent — Inter Partes Review at the PTAB and EPO opposition, from petition to final written decision
Every patent invalidation challenge begins with a strategic choice: which patent to attack, which claims within it are commercially blocking, which prior art best supports unpatentability, and which forum — USPTO Inter Partes Review or EPO opposition — offers the fastest, cheapest, most favorable path to clearing the way to market.
The Leahy-Smith America Invents Act (AIA), signed into law in September 2011, created Inter Partes Review (IPR) as a streamlined, quasi-judicial alternative to district-court patent litigation. Effective September 16, 2012, IPR moved adjudication of patent validity — on novelty and obviousness grounds only, based solely on patents and printed publications — from federal district courts into the Patent Trial and Appeal Board (PTAB), a specialized administrative tribunal within the USPTO.
Why challengers prefer IPR over district court:
• Speed: statutory deadline for Final Written Decision within 12 months of institution (extendable to 18 months for good cause), versus 2–4 years for district court patent litigation to reach trial • Cost: total IPR cost typically $300k–$700k versus $2M–$5M+ for district court patent litigation through trial • Standard of proof: preponderance of the evidence (>50%) at the PTAB, versus clear and convincing evidence required to invalidate a patent in district court — a meaningfully lower bar for the challenger • Expert panel: three Administrative Patent Judges (APJs), most with technical (often PhD-level) and legal training, versus a lay jury
Grounds available in IPR are narrower than in district court: only anticipation (35 U.S.C. §102) and obviousness (35 U.S.C. §103), and only based on prior art patents and printed publications — no §101 subject-matter eligibility, no §112 enablement/written description, and no prior public use or sale (which remain exclusively litigation defenses).
A generic or biosimilar manufacturer facing a Hatch-Waxman or BPCIA infringement suit over a branded drug's patent will frequently file an IPR petition in parallel with (or instead of) an ANDA/aBLA Paragraph IV litigation defense — attacking the same patent through two forums simultaneously to maximize the odds of clearing a path to market before exclusivity expires.
A well-constructed petition is built around a small number of strong grounds rather than a scattershot of weak ones — PTAB panels and their word-count limits (14,000 words for the petition) punish sprawling, unfocused challenges.
Claim selection: petitioners typically target the commercially significant claims — often the broadest independent claims covering the marketed formulation, dosing regimen, or crystalline form — rather than every claim in the patent. Challenging 12 of an 18-claim patent (leaving narrow dependent claims for later, cheaper challenges) is a common pattern.
Grounds — anticipation vs. obviousness: • Anticipation (§102): a single prior art reference discloses every element of the claim, arranged as claimed. The strongest, cleanest ground when available — but such "smoking gun" single references are rare against well-drafted pharma claims. • Obviousness (§103): the claimed invention would have been obvious to a person having ordinary skill in the art (PHOSITA) in view of the combined teachings of two or more references, applying the Graham v. John Deere (1966) factors: (1) scope and content of the prior art, (2) differences between the prior art and the claims, (3) level of ordinary skill, (4) objective indicia (secondary considerations) such as commercial success, long-felt unmet need, and unexpected results.
Prior art sourcing: patent challengers mine issued patents, published patent applications, scientific journal articles, conference abstracts, FDA labels and approval packages, and — critically for pharma — prior clinical trial registrations (ClinicalTrials.gov) and prior art cited in related family members or foreign prosecution histories (especially European and Japanese counterparts, whose examiners may have applied different, sometimes stricter, art).
The European Patent Office offers a centralized post-grant opposition procedure under Articles 99–105 EPC, available to any third party (opponents may act anonymously through a straw man) for nine months from the date the mention of grant is published in the European Patent Bulletin. Because a single European patent, once granted, can be validated in up to 39 EPC contracting states, a successful EPO opposition revokes or narrows the patent across the entire European footprint in one proceeding — far more efficient than separate national revocation actions in each country.
Grounds available in EPO opposition are broader than U.S. IPR: lack of novelty (Art. 54), lack of inventive step (Art. 56), insufficient disclosure (Art. 83, roughly analogous to U.S. enablement), added subject matter (Art. 123(2), amendments extending beyond the application as filed), and lack of patentable subject matter (Art. 52-53).
The opposition is examined by an Opposition Division composed of three technically qualified EPO examiners, at least two of whom did not participate in the original examination that granted the patent — an internal check against confirmation bias. Opposition remains a comparatively low-cost tool: official EPO opposition fees are on the order of a few hundred euros, though total costs (attorney fees, expert evidence, oral proceedings) typically run into the tens of thousands of euros — still far below district-court-scale litigation.
Unlike EPO opposition, where a timely, properly formed opposition is admitted essentially as of right, U.S. IPR interposes a discretionary gate: the PTAB must decide, within three months of receiving the patent owner's preliminary response, whether to institute trial at all — and on which claims and grounds.
Under 35 U.S.C. §314(a), the PTAB Director (delegated to the panel) may not institute an IPR unless the petition and preliminary response show "a reasonable likelihood that the petitioner would prevail with respect to at least one of the claims challenged." This is a comparatively low threshold — well short of the "preponderance of the evidence" standard applied at the merits stage — but it is nonetheless a genuine gate: roughly one in three petitions is denied institution entirely.
The patent owner's preliminary response (POPR), filed within three months of the petition, is the first opportunity to argue against institution — typically by attacking the sufficiency of the prior art combination, disputing claim construction, invoking the one-year time bar, or raising discretionary denial arguments.
Discretionary denial — the Fintiv factors: even where the merits threshold is met, the Director retains discretion to deny institution under 35 U.S.C. §314(a) when parallel district court litigation on the same patent is proceeding to trial quickly. The PTAB's Apple v. Fintiv (2020) precedential decision set out six factors weighing discretionary denial, including the proximity of the parallel trial date, investment in the parallel proceeding, and overlap of issues — a doctrine that has significantly reduced institution rates for petitions filed late relative to a fast-moving companion district court case.
Historical USPTO PTAB statistics show the institution rate has fluctuated from a high of roughly 87% in the earliest years of the program (FY2013) down to the mid-to-high 50s during the peak of Fintiv-driven discretionary denials (2020–2021), settling back to roughly 65–70% in recent fiscal years as the PTAB refined its discretionary-denial guidance.
Before the Supreme Court's SAS Institute v. Iancu (2018) decision, the PTAB could institute trial on some challenged claims and grounds while denying others — "partial institution." SAS held that the statute requires an all-or-nothing approach: if the Board institutes at all, it must institute on every claim and every ground raised in the petition. This simplified the trial scope (no more claim-by-claim institution triage) but raised the stakes of the initial institution decision, since a marginal petition is now either fully in or fully out.
Practical consequence for pharma patent challenges: petitioners now front-load their strongest grounds and drop weak ones before filing, since a single weak ground included in the petition can no longer simply be excised at institution — the whole petition succeeds or fails together on the reasonable-likelihood threshold as applied to the strongest claim.
The EPO Opposition Division performs only a formal admissibility check: was the opposition filed within the nine-month window, is the opposition fee paid, does the notice of opposition identify the extent of opposition and the grounds relied upon with supporting facts and evidence in sufficient detail (Rule 76 EPC)? There is no merits-based gate analogous to §314(a) — an opposition that is formally complete is admitted, and the Opposition Division proceeds to examine the substantive grounds on the full merits.
This structural difference matters strategically: because EPO opposition carries no institution risk, opponents can raise more grounds more liberally than in a U.S. IPR petition, where petitioners must marshal their single best case to clear the reasonable-likelihood bar before ever reaching the merits.
Once trial is instituted, the proceeding shifts into a compressed discovery and briefing phase: both sides submit expert declarations construing the disputed claim language and applying that construction to the prior art, exchange limited discovery, and file a sequence of merits briefs — all within the tight statutory clock running toward a Final Written Decision.
For its first six years, the PTAB construed claims in IPR proceedings under the "broadest reasonable interpretation" (BRI) standard — the same standard used during original patent examination — on the theory that a patent owner retains the ability to amend claims during an IPR (via a motion to amend), so a broader construction was appropriate. BRI construction, being broader, made it easier for petitioners to read prior art onto the claims and correspondingly easier to invalidate them.
Effective November 13, 2018, the USPTO amended its rules (37 C.F.R. §42.100(b)) to replace BRI with the Phillips standard — the same claim construction standard applied in Article III district courts and derived from Phillips v. AWH Corp. (Fed. Cir. 2005, en banc). Under Phillips, claims are construed according to their ordinary and customary meaning to a person of ordinary skill in the art at the time of the invention, read in light of the specification and prosecution history (intrinsic evidence given primacy over extrinsic evidence like dictionaries or expert testimony).
This harmonization was intended to reduce inconsistent outcomes between the PTAB and parallel district court litigation on the same patent — a claim term construed narrowly by a district court could no longer be construed more broadly (and therefore more vulnerable to prior art) at the PTAB.
Both petitioner and patent owner retain technical experts — typically PhD-level scientists in the relevant pharmaceutical or chemical discipline — to submit declarations under 37 C.F.R. §42.65 addressing:
• Level of ordinary skill in the art (education, experience typical of a PHOSITA at the critical date) • Claim construction, applying Phillips to disputed terms • Whether each claim limitation is disclosed, expressly or inherently, in the asserted prior art • For obviousness grounds, whether a PHOSITA would have been motivated to combine the asserted references, with a reasonable expectation of success, and whether the combination would have achieved the claimed invention • Rebuttal of the opposing expert's secondary-considerations evidence (commercial success nexus, unexpected results, long-felt need, failure of others, copying)
Cross-examination depositions of opposing experts are a central evidentiary event — transcript excerpts are frequently the decisive exhibits cited in the Final Written Decision, particularly admissions elicited on cross regarding motivation to combine or the plausibility of a reasonable expectation of success.
In pharmaceutical obviousness challenges, "obvious to try" is not automatically obviousness — KSR Int'l Co. v. Teleflex (2007) held a claim may be obvious if there was a finite number of identified, predictable solutions and a PHOSITA had good reason to pursue them, but the Federal Circuit has repeatedly cautioned that unpredictable results in chemistry and pharmacology (e.g., unexpected potency, bioavailability, or reduced toxicity of a specific salt or polymorph) can rebut an obvious-to-try case — making crystalline form, salt-selection, and formulation patents some of the hardest-fought battlegrounds in pharma IPR practice.
IPR discovery is deliberately limited compared to district court litigation, consistent with Congress's goal of a faster, cheaper alternative:
• Mandatory initial disclosures: real party-in-interest, related matters, lead and back-up counsel • Routine discovery (37 C.F.R. §42.51(b)(1)): exhibits cited in a party's paper, cross-examination of declarants (depositions), and any relevant information inconsistent with a position advanced (a narrow, self-executing duty roughly analogous to a duty of candor) • Additional discovery: available only by motion, applying the Garmin factors (more than a possibility of useful information, not a fishing expedition, ability to generate the requested information themselves, easily understandable instructions, non-burdensome requests) — the PTAB grants additional discovery sparingly • Motion to amend: patent owner may file a contingent motion to amend, proposing substitute claims narrower than the originally challenged claims, to be considered only if the original claims are found unpatentable — a safety valve, though amended claims must themselves survive a new patentability analysis and cannot broaden scope or introduce new matter
As the statutory clock nears its deadline, both sides present live argument to the deciding panel — three Administrative Patent Judges at the PTAB, or the Opposition Division's three examiners at the EPO — walking through the claim charts, contesting motivation to combine, and, for pharma patents specifically, sparring over secondary-considerations evidence meant to rebut a prima facie case of obviousness.
The oral hearing is the only live, in-person (or video) advocacy opportunity in the entire IPR proceeding — everything else is written briefing and documentary/deposition evidence. Held roughly 10–11 months into a standard 12-month trial, shortly before the panel must issue its Final Written Decision, the hearing typically runs about one hour per side before the three-APJ panel.
Structure: petitioner presents first (as the moving party bearing the burden of proving unpatentability by a preponderance of the evidence), walking through demonstrative slides mapping each prior art reference to each claim limitation, and articulating the motivation a PHOSITA would have had to combine references. Patent owner responds, attacking gaps in the combination, disputing claim construction, and presenting secondary-considerations evidence. Petitioner may reserve rebuttal time.
Judges actively question counsel throughout — unlike many appellate arguments, PTAB hearings are often highly interactive, with APJs (who typically have relevant scientific/technical backgrounds) probing the strength of the prior art teachings and testing counsel's claim-construction positions against the intrinsic record.
No new evidence or arguments may be introduced at the hearing that were not already presented in the briefing — the hearing is argument on an already-closed record, not a fact-finding proceeding.
For each challenged claim, the panel must resolve, element by element:
1. Claim construction: what does the disputed term mean, applying Phillips? 2. Disclosure: does the prior art (singly for anticipation, or in combination for obviousness) disclose that claim element, either expressly or inherently? 3. Motivation to combine (obviousness only): would a PHOSITA, at the time of the invention, have had a reason — articulated with rational underpinning, not hindsight — to combine the specific references in the specific way claimed? 4. Reasonable expectation of success: would that PHOSITA have expected the combination to work, not merely hoped it might? 5. Secondary considerations: does objective evidence of commercial success, long-felt unmet need, failure of others, unexpected results, industry praise, or copying support non-obviousness — and is there a sufficient nexus between that evidence and the specific claimed features (not just general product success)?
For a mixed patent portfolio (e.g., a genus claim, a species claim, a formulation claim, and a method-of-treatment claim all in the same patent), the panel's claim-by-claim analysis frequently produces mixed outcomes — some claims cancelled, others confirmed — because the strength of the prior art combination and the secondary-considerations nexus can differ sharply claim to claim.
EPO oral proceedings before the Opposition Division are often scheduled for a single day and, unusually by U.S. standards, the Division frequently announces its decision on novelty, inventive step, and the maintained claim set at the end of that same hearing day — with the full written reasoning ("decision with reasons") following weeks later.
The Division's three members (a first examiner as chair, a second examiner, and a legally qualified member for complex cases) deliberate in a closed session before returning to announce the outcome: patent maintained as granted, patent maintained in amended form (having considered patent owner's auxiliary requests — fallback narrowed claim sets filed precisely for this purpose), or patent revoked in its entirety.
The auxiliary-request practice is a distinctively European procedural tool: patent owners file a cascading series of increasingly narrow claim amendments (Auxiliary Request 1, 2, 3…) as fallback positions, allowing the Division to grant partial relief by falling back to a narrower, defensible claim set rather than an all-or-nothing outcome — a more incremental mechanism than the PTAB's contingent motion-to-amend practice.
The proceeding culminates in a binding decision on patentability — and, for the losing side, a path to further appeal. The consequences ripple far beyond the PTAB or Opposition Division: they reset the competitive landscape for the drug at issue, trigger estoppel that reshapes any parallel litigation, and, in pharma specifically, can accelerate or foreclose generic and biosimilar entry.
The Final Written Decision (FWD), issued under 35 U.S.C. §318(a), resolves the patentability of every instituted claim — there is no partial "punt": each claim is either found unpatentable (cancelled) or not shown to be unpatentable (confirmed to survive, at least as to the grounds raised in that proceeding).
Of IPR trials that reach a Final Written Decision, historical USPTO statistics show a substantial majority end with at least one, and typically all, challenged claims cancelled — roughly two-thirds of FWDs cancel every instituted claim, with a further slice cancelling some but not all claims, and the remainder confirming all challenged claims as patentable. Cumulatively, since claims can also be resolved by settlement or adverse judgment before reaching a decision, the overall population of filed petitions produces cancellation of at least one claim in a substantial majority of cases that survive institution.
Estoppel — 35 U.S.C. §315(e): a petitioner who receives a Final Written Decision is estopped from later asserting, in a district court civil action or a subsequent USPTO proceeding, that the challenged claim is invalid on any ground that the petitioner raised or reasonably could have raised during the IPR. Following the Federal Circuit's Click-to-Call Technologies (2018, en banc) and later decisions clarifying and broadening the scope of "reasonably could have raised," estoppel now extends to prior art the petitioner reasonably could have found through a diligent search — not merely the specific references cited in the petition — substantially raising the stakes of losing an IPR on the merits.
A branded pharma company that survives an IPR with all challenged claims confirmed gains a powerful strategic asset: the challenger — and often other prospective generic entrants who track the outcome — is now estopped from re-litigating the same or reasonably discoverable invalidity grounds in the parallel Hatch-Waxman district court action, meaningfully strengthening the patent owner's negotiating position in any subsequent settlement or licensing discussion.
Either party may appeal a Final Written Decision directly to the U.S. Court of Appeals for the Federal Circuit (35 U.S.C. §319) — bypassing district court entirely, since the Federal Circuit has exclusive jurisdiction over patent appeals. The standard of review is deferential: factual findings (including obviousness sub-findings like motivation to combine) are reviewed for substantial evidence, while legal conclusions (including the ultimate question of obviousness and claim construction) are reviewed de novo.
A large share of PTAB appeals are resolved by Rule 36 summary affirmance — a one-line judgment affirming without a written opinion, issued when the Federal Circuit panel unanimously agrees the case does not warrant a full opinion. This reflects the deference given to PTAB factual findings and contributes to the high overall affirmance rate. Full merits opinions are reserved for cases presenting genuinely novel legal questions (claim construction methodology, procedural due process, application of estoppel).
Appeal timelines add meaningfully to overall resolution time: briefing, argument, and decision at the Federal Circuit typically add 12–18 months beyond the FWD, meaning a full IPR-through-appeal cycle can span 2.5–3 years from petition filing — still faster, in most cases, than parallel district court patent litigation through trial and appeal.
A party dissatisfied with an Opposition Division decision may appeal to an EPO Board of Appeal (Art. 106–112 EPC), an internal but functionally independent judicial body of the EPO. Appeal has suspensive effect — the Opposition Division's decision does not take effect until the appeal is resolved — and Board of Appeal proceedings frequently take two to four years to reach a final decision, again often centered on cascading auxiliary claim requests.
Downstream commercial effect, common to both fora: a successful invalidation challenge — full cancellation, or even narrowing to claims that no longer read on a generic or biosimilar's specific formulation — can clear the way for earlier market entry, while a patent that survives intact strengthens the originator's position in settlement negotiations, licensing terms, and any parallel infringement litigation. Because IPR/opposition outcomes are public and closely tracked, a single decisive Final Written Decision or Opposition Division ruling often becomes the reference point that resolves an entire cluster of pending disputes over the same patent family across multiple challengers and jurisdictions.