Regeneron Pharmaceuticals, Inc. v. Celltrion, Inc.

Regeneron Pharmaceuticals, Inc., an American biotechnology company known for inventing and commercializing life-transforming medicines, initiated this patent infringement lawsuit against Celltrion, Inc., a South Korean biopharmaceutical company specializing in biosimilars. The core of the dispute centers on Celltrion's proposed biosimilar product, "CT-P42," which is an alleged infringing copy of Regeneron's blockbuster ophthalmic drug, EYLEA® (aflibercept). EYLEA® is a critical treatment for various eye diseases that can lead to vision loss, including neovascular (wet) age-related macular degeneration, macular edema following retinal vein occlusion, diabetic macular edema, and diabetic retinopathy.

The litigation began under the Biologics Price Competition and Innovation Act (BPCIA) in the U.S. District Court for the Northern District of West Virginia, before Chief District Judge Thomas S. Kleeh, after Celltrion submitted its abbreviated Biologics License Application (aBLA) for CT-P42 and served notice of commercial marketing. While Regeneron initially asserted 38 patents, the focus for the preliminary injunction narrowed to U.S. Patent 11084865, often referred to as the "Product Patent." This patent, titled "VEGF antagonist formulations suitable for intravitreal administration," broadly covers stable ophthalmic formulations of aflibercept (a VEGF-specific fusion protein antagonist) for intravitreal administration, specifying components like buffers, co-solvents, and stabilizing agents, along with requirements for product stability. The choice of the Northern District of West Virginia is notable, as it has become a central forum for Regeneron's EYLEA® biosimilar litigation, with Judge Kleeh presiding over multiple related cases, some of which were considered for Multidistrict Litigation (MDL) consolidation.

This case is particularly significant due to its high-stakes nature within the biosimilar landscape, involving EYLEA®, a major revenue driver for Regeneron. The procedural posture saw the district court grant a preliminary injunction against Celltrion, which was subsequently affirmed by the Federal Circuit, temporarily blocking Celltrion's biosimilar launch. Adding another layer of complexity, a related inter partes review (IPR2025-00456) challenging the '865 patent at the PTAB was denied institution on discretionary grounds. Ultimately, the parties reached a settlement that allows Celltrion to launch its aflibercept biosimilar (Eydenzelt) in the U.S. on December 31, 2026, a common resolution in complex BPCIA disputes that balances patent exclusivity with market access for biosimilars.

The patent infringement litigation between Regeneron Pharmaceuticals, Inc. and Celltrion, Inc., case number 1:23-cv-00089 in the U.S. District Court for the Northern District of West Virginia, centered on U.S. Patent 11084865, has concluded through settlement.

Here is a chronological overview of the key legal developments and outcome:

• Filing & Initial Pleadings:

  • November 8, 2023: Regeneron Pharmaceuticals, Inc. filed a Biologics Price Competition and Innovation Act (BPCIA) complaint against Celltrion, Inc. in the U.S. District Court for the Northern District of West Virginia. Regeneron alleged infringement of 38 patents, including U.S. Patent 11084865, by Celltrion's proposed Eylea (aflibercept) biosimilar, CT-P42. The lawsuit was triggered after Celltrion served a notice of commercial marketing for CT-P42, indicating its intent to launch the product upon FDA approval. The complaint sought a declaratory judgment of patent infringement and preliminary equitable relief.

• Pre-Trial Motions of Substance & Discovery:

  • December 28, 2023: Regeneron filed an emergency motion requesting a schedule for preliminary injunction proceedings.
  • January 9, 2024: The court issued an order setting a briefing schedule for preliminary injunction proceedings. Initial discovery related to the preliminary injunction was scheduled from January through April 2024.
  • January 17, 2024: Celltrion filed a motion to dismiss for lack of personal jurisdiction or, alternatively, to transfer venue.
  • February 22, 2024: Regeneron filed its motion for a preliminary injunction, initially asserting the '865 patent and U.S. Patent 11,793,926 (the "Sterile Barrier Patent").
  • May 21, 2024: Regeneron moved to withdraw its preliminary injunction motions with respect to the Sterile Barrier Patent, limiting its assertion to the '865 patent.
  • June 28, 2024: The District Court for the Northern District of West Virginia granted Regeneron's motion for a preliminary injunction, preventing Celltrion from launching its CT-P42 biosimilar.

• Appeals & Federal Circuit Affirmation:

  • July 8, 2024: Celltrion filed a notice of appeal, which was amended on July 12, 2024, challenging the preliminary injunction.
  • March 5, 2025: The U.S. Court of Appeals for the Federal Circuit affirmed the district court's grant of the preliminary injunction against Celltrion's CT-P42 biosimilar. The Federal Circuit found that Celltrion had not raised a substantial question of invalidity regarding the '865 patent.

• Parallel PTAB IPR Proceedings:

  • Celltrion filed an Inter Partes Review (IPR) petition, IPR2025-00456, challenging the validity of U.S. Patent 11084865 at the Patent Trial and Appeal Board (PTAB). The PTAB subsequently denied institution of this IPR, as noted in the case metadata.

• Claim Construction (Markman) & Further Discovery:

  • September 29, 2025: A scheduling order was issued, setting a Markman (claim construction) hearing for November 23, 2026, and discovery due by November 4, 2026.

• Settlement & Final Disposition:

  • October 20, 2025: A stipulation and [proposed] order dismissing all claims and counterclaims, vacating the preliminary injunction, and releasing the preliminary injunction bond was filed by Regeneron Pharmaceuticals, Inc.
  • October 21, 2025: The case was closed and dismissed by the district court in view of the parties' settlement. Due to the settlement, the scheduled Markman hearing did not take place.

Regeneron Pharmaceuticals, Inc. is represented by a team of attorneys primarily from Williams & Connolly LLP and Weil, Gotshal & Manges LLP, with local counsel in West Virginia. The following individuals are counsel of record:

Local Counsel

• Steven R. Ruby
  • Role: Local Counsel
  • Firm: Carey Douglas Kessler & Ruby, PLLC
  • Office Location: Charleston, West Virginia
  • Experience Note: Experienced in West Virginia federal court practice, handling local filings and pro hac vice admissions for out-of-state counsel in this and related patent cases.

Lead/Primary Counsel (Admitted Pro Hac Vice)

From Williams & Connolly LLP (Washington, D.C. office is common for their patent litigation):

• David I. Berl
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Williams & Connolly LLP
  • Office Location: Washington, D.C.
  • Experience Note: Actively involved in pharmaceutical patent litigation, including BPCIA cases for innovator companies like Regeneron.
• Ellen E. Oberwetter
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Williams & Connolly LLP
  • Office Location: Washington, D.C.
  • Experience Note: Represents Regeneron in complex patent disputes, particularly in the life sciences sector.
• Thomas S. Fletcher
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Williams & Connolly LLP
  • Office Location: Washington, D.C.
  • Experience Note: A member of the legal team representing Regeneron in its significant patent infringement actions.
• Andrew V. Trask
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Williams & Connolly LLP
  • Office Location: Washington, D.C.
  • Experience Note: Appears on behalf of Regeneron in its BPCIA litigation strategy.
• Teagan J. Gregory
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Williams & Connolly LLP
  • Office Location: Washington, D.C.
  • Experience Note: Part of the Williams & Connolly team handling Regeneron's patent enforcement cases.
• Shaun P. Mahaffy
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Williams & Connolly LLP
  • Office Location: Washington, D.C.
  • Experience Note: Represents Regeneron in pharmaceutical patent litigation.
• Kathryn S. Kayali
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Williams & Connolly LLP
  • Office Location: Washington, D.C.
  • Experience Note: Involved in the patent infringement litigation for Regeneron.
• Arthur J. Argall III
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Williams & Connolly LLP
  • Office Location: Washington, D.C.
  • Experience Note: A member of the litigation team for Regeneron in this BPCIA action.
• Adam Pan
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Williams & Connolly LLP
  • Office Location: Washington, D.C.
  • Experience Note: Actively involved in the litigation for Regeneron.
• Rebecca A. Carter
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Williams & Connolly LLP
  • Office Location: Washington, D.C.
  • Experience Note: Represents Regeneron in its intellectual property disputes.
• Haylee N. Bernal Anderson
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Williams & Connolly LLP
  • Office Location: Washington, D.C.
  • Experience Note: Listed as part of the legal counsel for Regeneron.
• Renee M. Griffin
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Williams & Connolly LLP
  • Office Location: Washington, D.C.
  • Experience Note: Involved in the patent litigation representing Regeneron.
• Jennalee Beazley
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Williams & Connolly LLP
  • Office Location: Washington, D.C.
  • Experience Note: Part of the litigation team for Regeneron.
• Rhochelle Krawetz
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Williams & Connolly LLP
  • Office Location: Washington, D.C.
  • Experience Note: Appears as counsel for Regeneron in the ongoing litigation.

From Weil, Gotshal & Manges LLP (New York, NY office is common for their patent litigation):

• Elizabeth S. Weiswasser
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Weil, Gotshal & Manges LLP
  • Office Location: New York, NY
  • Experience Note: Recognized for her work in high-stakes intellectual property and life sciences litigation.
• Anish R. Desai
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Weil, Gotshal & Manges LLP
  • Office Location: New York, NY
  • Experience Note: Represents pharmaceutical and biotechnology companies in complex patent disputes.
• Natalie C. Kennedy
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Weil, Gotshal & Manges LLP
  • Office Location: New York, NY
  • Experience Note: Involved in intellectual property litigation, particularly in the life sciences industry.
• Yi Zhang
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Weil, Gotshal & Manges LLP
  • Office Location: New York, NY
  • Experience Note: Part of the team representing Regeneron in patent matters.
• Kathryn Leicht
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Weil, Gotshal & Manges LLP
  • Office Location: New York, NY
  • Experience Note: Represents clients in patent litigation, with a focus on the biotechnology and pharmaceutical sectors.
• Rocco Recce
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Weil, Gotshal & Manges LLP
  • Office Location: New York, NY
  • Experience Note: A member of the legal team representing Regeneron in this patent dispute.
• Zhen Lin
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Weil, Gotshal & Manges LLP
  • Office Location: New York, NY
  • Experience Note: Appears as counsel for Regeneron in this litigation.
• Kellie Van Beck
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Weil, Gotshal & Manges LLP
  • Office Location: New York, NY
  • Experience Note: Involved in intellectual property litigation for Regeneron.
• Christopher M. Pepe
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Weil, Gotshal & Manges LLP
  • Office Location: New York, NY
  • Experience Note: Represents Regeneron in its patent litigation matters.
• Priyata Y. Patel
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Weil, Gotshal & Manges LLP
  • Office Location: New York, NY
  • Experience Note: Listed as counsel for Regeneron.
• Matthew Sieger
  • Role: Lead Counsel (Admitted Pro Hac Vice)
  • Firm: Weil, Gotshal & Manges LLP
  • Office Location: New York, NY
  • Experience Note: Part of the legal representation for Regeneron in this case.

The defendant, Celltrion, Inc., in Regeneron Pharmaceuticals, Inc. v. Celltrion, Inc. (1:23-cv-00089 N.D.W. Va.) is represented by attorneys from multiple firms. While specific roles (lead, of counsel, local, in-house) are not always explicitly stated in public search results, patterns in appearances and related cases can indicate their involvement.

Here's an overview of the counsel representing Celltrion:

1. Quinn Emanuel Urquhart & Sullivan, LLP

• This firm is actively involved in representing biosimilar defendants against Regeneron. William Adams of Quinn Emanuel, for instance, argued for a defendant-appellant in a related case involving Regeneron and other biosimilar companies at the Federal Circuit. They have a robust life sciences litigation practice.
  • William Adams (Likely Lead Counsel)
    • Firm: Quinn Emanuel Urquhart & Sullivan, LLP, New York, NY.
    • Experience: Argued for a defendant-appellant in a Federal Circuit appeal involving Regeneron and other biosimilar companies. Specializes in patent and other complex commercial litigation for pharmaceutical, biotechnology, and medical device companies.
  • Laura Fairneny (Likely Lead or Senior Counsel)
    • Firm: Quinn Emanuel Urquhart & Sullivan, LLP.
    • Experience: Listed as counsel in related Federal Circuit appeals involving Regeneron.
  • Raymond Nimrod (Likely Lead or Senior Counsel)
    • Firm: Quinn Emanuel Urquhart & Sullivan, LLP.
    • Experience: Listed as counsel in related Federal Circuit appeals involving Regeneron.
  • Matthew D. Robson (Likely Lead or Senior Counsel)
    • Firm: Quinn Emanuel Urquhart & Sullivan, LLP.
    • Experience: Listed as counsel in related Federal Circuit appeals involving Regeneron.
  • Matthew A. Traupman (Likely Lead or Senior Counsel)
    • Firm: Quinn Emanuel Urquhart & Sullivan, LLP.
    • Experience: Listed as counsel in related Federal Circuit appeals involving Regeneron.
  • Lauren Martin (Likely Lead or Senior Counsel)
    • Firm: Quinn Emanuel Urquhart & Sullivan, LLP, Boston, MA.
    • Experience: Listed as counsel in related Federal Circuit appeals involving Regeneron.

2. Rothwell Figg Ernst & Manbeck, P.C.

• This firm represented Celltrion in a related Post-Grant Review (PGR) at the PTAB concerning a Regeneron patent.
  • E. Anthony Figg (Lead Counsel/Member)
    • Firm: Rothwell Figg Ernst & Manbeck, P.C.
    • Experience: Represented Celltrion in a successful PGR challenge against a Regeneron patent. Specializes in intellectual property law, particularly patent litigation.
  • Joo Mee Kim (Member)
    • Firm: Rothwell Figg Ernst & Manbeck, P.C.
    • Experience: Represented Celltrion in a successful PGR challenge against a Regeneron patent.
  • Brett A. Postal (Member)
    • Firm: Rothwell Figg Ernst & Manbeck, P.C.
    • Experience: Represented Celltrion in a successful PGR challenge against a Regeneron patent.
  • Rachel M. Echols (Member)
    • Firm: Rothwell Figg Ernst & Manbeck, P.C.
    • Experience: Represented Celltrion in a successful PGR challenge against a Regeneron patent.

3. Schrader Companion Duff & Law, PLLC

• This firm appears to act as local counsel in West Virginia, given the court's location.
  • Sandra K. Law (Local Counsel)
    • Firm: Schrader Companion Duff & Law, PLLC, Wheeling, WV.
    • Experience: WVSB No. 6071, indicating admission to the West Virginia bar.

4. Gemini Law LLP

• The initial complaint email mentioned Gemini Law LLP as Celltrion's U.S. counsel for service of process. However, later docket entries and appeals indicate the active involvement of Quinn Emanuel. It's possible Gemini Law LLP had an early role or focuses on specific aspects, but Quinn Emanuel seems to be the primary litigation counsel.
  • Attorneys from Gemini Law LLP were not individually named in the provided snippets regarding appearances or arguments.

Note: The case is part of a larger Multidistrict Litigation (MDL 1:24-md-03103 N.D.W. Va.), and filings often involve multiple defendants and their respective counsel. The provided information reflects appearances and involvement across the related Regeneron-Eylea biosimilar litigation. Regeneron and Celltrion reached a settlement in October 2025, allowing Celltrion to launch its biosimilar product in the U.S. on December 31, 2026, and all IP litigation between them would be dismissed.In the patent infringement case Regeneron Pharmaceuticals, Inc. v. Celltrion, Inc. (1:23-cv-00089 N.D.W. Va.), the defendant, Celltrion, Inc., has been represented by counsel from multiple firms, primarily focusing on patent litigation. While specific "lead counsel" designations are not always explicitly stated in publicly available snippets, their roles can be inferred from their activity in the district court and related appeals and PTAB proceedings.

The counsel of record representing Celltrion, Inc. includes:

1. Quinn Emanuel Urquhart & Sullivan, LLP
This firm is a prominent player in high-stakes intellectual property litigation, particularly for pharmaceutical and biotechnology companies. They have actively represented biosimilar defendants against Regeneron in related actions, including at the Federal Circuit.

• William Adams (Likely Lead Counsel)
  • Firm: Quinn Emanuel Urquhart & Sullivan, LLP, New York, NY.
  • Experience: Mr. Adams argued for a defendant-appellant in a Federal Circuit appeal involving Regeneron and other biosimilar companies in a related matter. He is known for his work in complex patent and commercial litigation within the life sciences sector.
• Laura Fairneny (Likely Lead or Senior Counsel)
  • Firm: Quinn Emanuel Urquhart & Sullivan, LLP.
  • Experience: Ms. Fairneny is listed as counsel in related Federal Circuit appeals involving Regeneron.
• Raymond Nimrod (Likely Lead or Senior Counsel)
  • Firm: Quinn Emanuel Urquhart & Sullivan, LLP.
  • Experience: Mr. Nimrod is listed as counsel in related Federal Circuit appeals involving Regeneron.
• Matthew D. Robson (Likely Lead or Senior Counsel)
  • Firm: Quinn Emanuel Urquhart & Sullivan, LLP.
  • Experience: Mr. Robson is listed as counsel in related Federal Circuit appeals involving Regeneron.
• Matthew A. Traupman (Likely Lead or Senior Counsel)
  • Firm: Quinn Emanuel Urquhart & Sullivan, LLP.
  • Experience: Mr. Traupman is listed as counsel in related Federal Circuit appeals involving Regeneron.
• Lauren Martin (Likely Lead or Senior Counsel)
  • Firm: Quinn Emanuel Urquhart & Sullivan, LLP, Boston, MA.
  • Experience: Ms. Martin is listed as counsel in related Federal Circuit appeals involving Regeneron.

2. Rothwell Figg Ernst & Manbeck, P.C.
This firm represented Celltrion in an Inter Partes Review (IPR) and Post-Grant Review (PGR) challenges against Regeneron's patents at the PTAB, demonstrating their expertise in patent validity challenges.

• E. Anthony Figg (Member, Counsel for PTAB proceedings)
  • Firm: Rothwell Figg Ernst & Manbeck, P.C.
  • Experience: Represented Celltrion in a successful PGR challenge against a Regeneron patent (U.S. Patent No. 10,857,231), which led to Regeneron disclaiming all claims.
• Joo Mee Kim (Member, Counsel for PTAB proceedings)
  • Firm: Rothwell Figg Ernst & Manbeck, P.C.
  • Experience: Represented Celltrion in the PGR challenge against Regeneron's '231 patent.
• Brett A. Postal (Member, Counsel for PTAB proceedings)
  • Firm: Rothwell Figg Ernst & Manbeck, P.C.
  • Experience: Represented Celltrion in the PGR challenge against Regeneron's '231 patent.
• Rachel M. Echols (Member, Counsel for PTAB proceedings)
  • Firm: Rothwell Figg Ernst & Manbeck, P.C.
  • Experience: Represented Celltrion in the PGR challenge against Regeneron's '231 patent.

3. Schrader Companion Duff & Law, PLLC
This firm provides local counsel services in West Virginia, where the district court case is seated.

• Sandra K. Law (Local Counsel)
  • Firm: Schrader Companion Duff & Law, PLLC, Wheeling, WV.
  • Experience: Admitted to the West Virginia State Bar (WVSB No. 6071), indicating her qualification to practice in the jurisdiction.

4. Gemini Law LLP
Initial filings indicated Gemini Law LLP as Celltrion's U.S. counsel for service of process. While specific attorneys from this firm were not detailed in the provided search results for active litigation roles, their early involvement suggests an advisory or initial representation capacity.

It is important to note that Regeneron and Celltrion reached a settlement agreement in October 2025, which allows Celltrion to launch its biosimilar product in the U.S. on December 31, 2026, and will result in the dismissal of all related intellectual property litigation in the U.S.