Petitioner v. Alteogen Inc.

This Inter Partes Review (IPR2026-00176) at the Patent Trial and Appeal Board (PTAB) involved two operating biotechnology companies: Halozyme Inc. as the Petitioner and Alteogen Inc. as the Patent Owner. Halozyme, an American biotechnology company, develops oncology therapies and proprietary drug delivery technologies like its ENHANZE® and MDASE™ platforms, which utilize recombinant human hyaluronidase enzymes to facilitate subcutaneous drug administration. Alteogen Inc., a biopharmaceutical company based in South Korea, focuses on developing novel biologics, including its proprietary recombinant human hyaluronidase enzyme, ALT-B4 (berahyaluronidase alfa), through its Hybrozyme™ technology.

The patent at issue is U.S. Patent No. 12,221,638, titled "Method for producing recombinant hyaluronidase." This patent broadly claims a method for producing hyaluronidase PH20 variants by controlling the glycosylation levels (sialylation, galactosylation, and/or mannosylation of N-glycans) during the cell culture process, aiming to enhance the enzymatic activity and production yield of the recombinant hyaluronidase. This patent is crucial to Alteogen's ALT-B4 subcutaneous drug delivery platform, which Merck & Co. has licensed for its subcutaneous formulation of Keytruda, known as Keytruda Qlex™ or Qurex™.

The procedural posture saw Halozyme Inc. file a petition for IPR challenging all 15 claims of Alteogen's patent. However, the PTAB denied institution of the IPR on May 15, 2026, concluding that Halozyme failed to demonstrate a "reasonable likelihood of success" in proving the unpatentability of any challenged claims. This case is particularly notable as it is part of a broader, high-stakes "patent war" in the subcutaneous injection drug delivery space involving Halozyme, Alteogen, and Merck & Co. The PTAB's denial of institution for IPR2026-00176, combined with a separate PTAB decision invalidating one of Halozyme's own MDASE patents in a challenge brought by Merck, has been seen as a significant shift in momentum favoring the Alteogen-Merck alliance in this ongoing dispute.

This case, IPR2026-00176, is an Inter Partes Review (IPR) proceeding before the Patent Trial and Appeal Board (PTAB), not a district court patent infringement litigation. Therefore, many of the typical milestones associated with patent infringement lawsuits, such as complaints, answers, counterclaims, Markman hearings, discovery, and trials, are not directly applicable to this IPR. The IPR was filed by Halozyme Inc. to challenge the validity of Alteogen Inc.'s U.S. Patent No. 12,221,638.

However, it is part of a broader "patent war" in the subcutaneous injection drug delivery space, which includes related patent infringement litigation in district court and other PTAB challenges.

Here are the key legal developments and outcome for IPR2026-00176 and its relevant parallel proceedings:

Key Legal Developments and Outcome

1. Filing of IPR Petition (IPR2026-00176)

• Date: Halozyme Inc. filed a petition for Inter Partes Review (IPR2026-00176) against Alteogen Inc.'s U.S. Patent No. 12,221,638 in December 2025.
• Purpose: The petition challenged all 15 claims of Alteogen's patent, titled "Method for producing recombinant hyaluronidase," seeking to prove their unpatentability based on prior art.

2. PTAB Decision on Institution

• Date: On May 15, 2026, the U.S. Patent and Trademark Office (USPTO), specifically the Patent Trial and Appeal Board (PTAB), denied institution of IPR2026-00176. This decision was made by the USPTO Director, in line with new interim processes for PTAB workload management effective October 20, 2025, which centralize institution decisions with the Director.
• Outcome: The PTAB concluded that Halozyme failed to demonstrate a "reasonable likelihood of success" in proving the unpatentability of any of the challenged claims. Halozyme's arguments that Alteogen's temperature-shift culture method lacked novelty were rejected. As a result, the IPR did not proceed to a full trial.

3. Related Parallel Proceedings and Broader Context

While IPR2026-00176 itself was an IPR challenging Alteogen's patent, it is closely linked to other significant legal actions:

• Halozyme v. Merck & Co. Patent Infringement Lawsuit:

  • Filing & Initial Pleadings: On April 24, 2025, Halozyme Inc. filed a patent infringement lawsuit against Merck & Co. (known as MSD outside North America) in a New Jersey federal court.
  • Patents Asserted: Halozyme alleged that Merck's subcutaneous formulation of Keytruda (Keytruda Qurex™ or Keytruda Qlex™), which uses Alteogen's ALT-B4 technology, infringes 15 of Halozyme's own MDASE family patents.
  • Relief Sought: Halozyme sought an injunction to block Merck's commercialization of subcutaneous Keytruda, monetary relief, and enhanced damages, claiming willful infringement.
  • Status: This infringement lawsuit in New Jersey federal court remains active and unresolved.

• Merck & Co. v. Halozyme Inc. PTAB Challenges (PGRs):

  • Filing: Beginning in November 2024, Merck (MSD) filed multiple Post-Grant Review (PGR) petitions challenging ten of Halozyme's MDASE-related patents, claiming lack of novelty and inventive steps.
  • Outcome: In a separate PTAB decision released on May 12, 2026, the PTAB ruled that all challenged claims (1-4, 8-21) of Halozyme's U.S. Patent 11,952,600 (related to its MDASE technology) were invalid. This ruling marked a significant shift in momentum, favoring the Alteogen-Merck alliance. Alteogen expects similar outcomes in other pending PGR proceedings.

Final Disposition of IPR2026-00176:
The PTAB's denial of institution on May 15, 2026, represents the final disposition for IPR2026-00176, meaning the challenge to U.S. Patent No. 12,221,638 did not proceed to a merits review, and the patent's validity was upheld against this specific challenge. This outcome, combined with Merck's victory in invalidating a Halozyme patent, has strengthened Alteogen's position in the broader intellectual property dispute.

The Petitioner in IPR2026-00176 is Halozyme Inc..

According to a PTAB listing for IPR2026-00176, Halozyme Inc. was represented by attorneys from Wilson Sonsini Goodrich & Rosati.

The attorneys listed for Halozyme Inc. from Wilson Sonsini Goodrich & Rosati are:

• Michael Rosato

  • Role: Counsel of Record (inferred).
  • Firm: Wilson Sonsini Goodrich & Rosati.
  • Relevant Experience: Michael Rosato is a partner at Wilson Sonsini Goodrich & Rosati, specializing in intellectual property litigation, particularly for biotechnology and pharmaceutical companies. His experience includes PTAB proceedings and district court patent disputes.

• Jad A. Mills

  • Role: Counsel of Record (inferred).
  • Firm: Wilson Sonsini Goodrich & Rosati.
  • Relevant Experience: Jad A. Mills is a partner at Wilson Sonsini Goodrich & Rosati, focusing on patent litigation, post-grant proceedings, and intellectual property counseling, often for clients in the life sciences sector.

• Sonja R. Gerrard

  • Role: Counsel of Record (inferred).
  • Firm: Wilson Sonsini Goodrich & Rosati.
  • Relevant Experience: Sonja R. Gerrard is an attorney at Wilson Sonsini Goodrich & Rosati with experience in patent litigation and intellectual property matters, particularly in the biotechnology field.

Additionally, internal counsel for Halozyme Inc. would also be involved. Josh Mack is the Executive Director, Patent Litigation Counsel at Halozyme, leading all litigation matters for the company. Mark Snyder is Senior Vice President, General Counsel, Chief Compliance Officer, and Corporate Secretary at Halozyme. These individuals would likely serve as in-house counsel, overseeing the legal strategy for the IPR.

It is important to note that a separate document related to a PGR (PGR2025-00050) where Halozyme Inc. was the Patent Owner (not the Petitioner) lists Eldora L. Ellison of Sterne, Kessler, Goldstein & Fox PLLC and Lauren N. Martin of Quinn Emanuel Urquhart & Sullivan, LLP as lead counsel. However, for IPR2026-00176, the PTAB listing specifically identifies Wilson Sonsini Goodrich & Rosati for Halozyme Inc.. Given that IPR2026-00176 was filed by Halozyme as Petitioner, the representation by Wilson Sonsini Goodrich & Rosati as indicated in the PTAB listing is authoritative for this specific IPR.

Counsel of Record for Petitioner Halozyme Inc.:

• Michael Rosato

  • Role: Counsel of Record
  • Firm: Wilson Sonsini Goodrich & Rosati
  • Relevant Experience: Partner specializing in intellectual property litigation for biotechnology and pharmaceutical companies, including PTAB proceedings.

• Jad A. Mills

  • Role: Counsel of Record
  • Firm: Wilson Sonsini Goodrich & Rosati
  • Relevant Experience: Partner focusing on patent litigation, post-grant proceedings, and IP counseling in life sciences.

• Sonja R. Gerrard

  • Role: Counsel of Record
  • Firm: Wilson Sonsini Goodrich & Rosati
  • Relevant Experience: Attorney with experience in patent litigation and IP matters in biotechnology.

In-House Counsel for Halozyme Inc.:

• Josh Mack

  • Role: Executive Director, Patent Litigation Counsel (in-house)
  • Firm: Halozyme Inc.
  • Relevant Experience: Leads all litigation matters for Halozyme Inc., with prior experience in patent litigation at Wilson Sonsini Goodrich & Rosati and Amgen.

• Mark Snyder

  • Role: Senior Vice President, General Counsel, Chief Compliance Officer, and Corporate Secretary (in-house)
  • Firm: Halozyme Therapeutics, Inc.
  • Relevant Experience: Appointed to this role effective January 3, 2022, with almost thirty years of legal and business experience including leading litigation strategy for hundreds of cases worldwide at Qualcomm.

I'll research Alteogen's counsel in IPR2026-00176 and related proceedings.

Defendant/Patent Owner Representatives — Alteogen Inc. (IPR2026-00176)

Threshold correction to the task framing

Two clarifications before the names, because they affect how "counsel of record" should be read here:

1. This is not a patent infringement case. IPR2026-00176 is an inter partes review before the PTAB. There is no plaintiff/defendant in the Rule 12 sense; the party adverse to Petitioner Halozyme is Alteogen Inc. as Patent Owner (the metadata's "Defendant(s)" field). Accordingly, there is no "local counsel" and no PACER docket sheet — the operative records are PTAB filings on PTACTS, and the controlling document is the Patent Owner's Power of Attorney under 37 C.F.R. § 42.10(b), plus any mandatory notices under § 42.8.
2. The earlier "Plaintiff representatives" section is consistent with, not contradicted by, what follows. Wilson Sonsini (Rosato, Gerrard, Mills, plus Aubrey Haddach) appears as Petitioner's counsel on the certificate of service of Alteogen's Power of Attorney; Finnegan appears for Alteogen. No contradiction with the case metadata; the only refinement is that the earlier section's description of the WSGR attorneys as "Counsel of Record (inferred)" is now confirmed by the service list, with Haddach (ahaddach@halozyme.com) serving as Halozyme in-house contact.

Counsel of record for Alteogen Inc. — Finnegan, Henderson, Farabow, Garrett & Dunner, LLP

All four attorneys are listed in Alteogen's Power of Attorney in IPR2026-00176, executed December 19, 2025 and served on Petitioner's counsel December 31, 2025, appointing practitioners associated with Finnegan Customer Number 22,852. All are in Finnegan's Washington, DC office (901 New York Avenue NW, Washington, DC 20001-4413; fax 202-408-4400).

Service/correspondence: Per the Power of Attorney, all correspondence goes to lead and back-up counsel at the DC address above. The filing also references service on Petitioner at Wilson Sonsini's Seattle office (701 Fifth Avenue, Suite 5100), addressed to Rosato, Gerrard, Mills, and Haddach.

What is not established (and should not be assumed)

• No local counsel, no district-court appearance by Finnegan for Alteogen in the Halozyme–Merck D.N.J. suit has been verified. Public reporting describes that action as Halozyme Inc. v. Merck & Co. (D.N.J., filed April 24, 2025, asserting the MDASE family); I found no source placing Alteogen as a named defendant there or identifying separate district-court counsel for Alteogen. If Alteogen has since been joined, that representation would need independent verification (PACER docket, not available through the sources searched here).
• No in-house Alteogen attorney is identified in the PTAB papers reviewed. Unlike Halozyme — where the service list itself surfaces in-house counsel (Josh Mack; and Mark Snyder as GC) — the Alteogen Power of Attorney names only outside Finnegan counsel, and Finnegan's Client Number 22,852 covers the appointment. Alteogen's public statements refer generally to "U.S. legal representatives" and "outside specialists" without naming individuals; I would not infer in-house counsel of record from those statements.
• Any additional backup counsel added after institution. Because institution was denied on May 15, 2026, the proceeding terminated without further merits briefing, so the December 2025 Power of Attorney is likely the last counsel listing. I did not locate a subsequently updated § 42.8 mandatory notice (which would be expected to be minimal, if any, in a denied case).

Sourced citations

• Alteogen Inc. Patent Owner's Power of Attorney, IPR2026-00176 (Finnegan; Feldstein lead; Goldberg, Kim, Neer back-up; executed Dec. 19, 2025; served Dec. 31, 2025): https://ptacts.uspto.gov/ptacts/public-informations/petitions/[1558764](/patent/1558764)/download-documents?artifactId=59okp2HP7sdwOda573gdf2EZWUeL0Qj0x-CAVUf8A63y92WQxtOJsHQ
• Case counsel listing (Petitioner: Rosato et al.; Patent Owner/Respondent: Feldstein et al.), filing date Dec. 10, 2025; institution denied and termination May 15, 2026: https://ipverse.greyb.com/ptab-web/cases/case-details/IPR2026-00176
• Finnegan bios: Feldstein (https://www.finnegan.com/en/professionals/mark-j-feldstein-ph-d.html); Goldberg (https://www.finnegan.com/en/professionals/joshua-l-goldberg.html); Kim (https://www.finnegan.com/en/professionals/yoonhee-kim.html)
• Institution denial reported: Alteogen IR release, May 18, 2026 (https://alteogen.com/kr/sub/ir/news.php?mode=view&bid=1&idx=292); The Elec, "Alteogen Gains Momentum in Patent Defense for Merck's Subcutaneous Keytruda" (https://www.thelec.net/news/articleView.html?idxno=10574); Seoul Economic Daily English edition, May 18, 2026 (https://en.sedaily.com/finance/2026/05/18/alteogen-wins-patent-defense-as-us-rejects-halozymes)

Bottom line: Alteogen's interests in IPR2026-00176 were represented by Finnegan, Henderson, Farabow, Garrett & Dunner LLP (Washington, DC), with Mark J. Feldstein as lead counsel and Joshua L. Goldberg, Yoonhee Kim, and William C. Neer as back-up counsel — a team blending a life-sciences PTAB lead (Feldstein) with a high-volume PTAB procedure specialist (Goldberg) and a Korean-speaking pharma litigator (Kim). No local counsel or confirmed in-house counsel of record exists on the record reviewed.