IPR Challenges to Biopharmaceutical Patents

Pharmaceutical and biologic patents are high-value targets. A single patent listed in the FDA’s Orange Book, or asserted against a biosimilar, can affect when a lower-cost product reaches the market. Companies seeking to launch such products have two main litigation frameworks: the Hatch-Waxman Act for small-molecule generics and the Biologics Price Competition and Innovation Act (BPCIA) for biosimilars. Inter partes review (IPR) at the Patent Trial and Appeal Board is often used alongside both.

This page explains how IPR fits into these disputes, which issues it can and cannot reach, and the timing and estoppel rules that shape strategy.

How IPR fits with Hatch-Waxman and BPCIA litigation

Under Hatch-Waxman, a generic applicant that certifies a listed patent is invalid or not infringed (a “Paragraph IV” certification) gives notice to the patent owner, and the patent owner can sue. A timely suit generally triggers a statutory stay of FDA approval. The BPCIA has its own procedures for exchanging patent information and litigating biosimilar disputes.

IPR runs on a separate track before the USPTO. Its attractions in this setting include:

• A different decision-maker. A panel of administrative patent judges with technical backgrounds decides the case.
• A lower burden of proof. The petitioner must prove unpatentability by a preponderance of the evidence (35 U.S.C. § 316(e)), rather than the clear and convincing standard that applies to invalidity in court.
• No presumption of validity of the kind that applies in litigation under 35 U.S.C. § 282.
• A statutory timeline. A final written decision is generally due within one year of institution, extendable for good cause.

What IPR can and cannot reach

IPR is limited to grounds under 35 U.S.C. § 102 or § 103, and only on the basis of prior art consisting of patents or printed publications (35 U.S.C. § 311(b)). That limit matters more in the life sciences than in many other fields.

Some of the most significant challenges to drug and biologic patents arise under 35 U.S.C. § 112: whether a claimed genus is enabled, or whether the specification shows possession of what is claimed. Those issues cannot be raised in IPR. They must be pursued in post-grant review, if available, or in court. The Supreme Court’s decision in Amgen Inc. v. Sanofi (2023), on enablement of broad functional genus claims, is an example of the kind of issue that sits outside IPR.

Typical obviousness issues in biopharma IPRs

Most pharmaceutical IPRs turn on obviousness. Recurring themes include:

• Dosing regimens. Claims to a particular dose, frequency or schedule are often challenged on the theory that optimizing those parameters from prior-art ranges would have been routine.
• Formulations. Claims to a specific combination of excipients, concentration or delivery form are compared with known formulation practices.
• Motivation to combine and reasonable expectation of success. The petitioner must show that a skilled artisan would have had reason to arrive at the claimed invention and a reasonable expectation of succeeding. Unpredictability in biology and chemistry is often the patent owner’s central response.
• Unexpected results and other objective indicia. Patent owners frequently rely on unexpected results, long-felt need, failure of others or commercial success. The evidence must have a nexus to what is claimed, and unexpected results are typically compared against the closest prior art.

These disputes are fact-intensive and depend heavily on expert testimony, which is one reason the trial record matters so much. See discovery in PGR and IPR for how such testimony is developed.

Timing: the one-year bar and filing strategy

An IPR petition is barred if filed more than one year after the petitioner, its real party in interest or a privy was served with a complaint alleging infringement of the patent (35 U.S.C. § 315(b)). Separately, a petitioner that first filed its own civil action challenging validity cannot later seek IPR on that patent (§ 315(a)).

Generic and biosimilar applicants therefore think carefully about when to petition. Some file before any suit, others soon after being served, so that the Board can institute while the litigation is still at an early stage. Parallel litigation can also affect whether the Board exercises its discretion to institute at all. Discretionary-denial practice has changed repeatedly, so check current USPTO guidance. For more on timing, see discovery and the one-year time period.

Estoppel considerations

Once the Board issues a final written decision, the petitioner, its real party in interest and privies are estopped in later civil actions and ITC proceedings from asserting invalidity on any ground they raised or reasonably could have raised during the IPR (35 U.S.C. § 315(e)(2)). For a generic company also litigating under Hatch-Waxman, this can narrow the prior-art defenses available in district court. Defenses outside IPR’s scope, including § 112 challenges, remain available. See estoppel arising from PTAB trials.

Post-grant review for newer patents

For patents with an effective filing date on or after March 16, 2013, a petition for post-grant review may be filed within nine months of grant. PGR allows any ground of invalidity that could be raised as a defense under 35 U.S.C. § 282(b)(2) or (3), including written description, enablement and indefiniteness. It requires a higher threshold for institution and carries broader estoppel. See the different threshold standards and the inter partes review guide.

Key takeaways

• IPR is a common companion to Hatch-Waxman and BPCIA litigation, offering a technical panel and a preponderance standard.
• IPR reaches only §§ 102 and 103 on patents and printed publications; § 112 issues need PGR or court.
• Obviousness of dosing regimens and formulations, expectation of success and objective indicia are recurring battlegrounds.
• The one-year bar of § 315(b) and the estoppel of § 315(e) drive timing and scope decisions.
• PGR is available within nine months of grant for first-inventor-to-file patents and can reach § 112 grounds.