Patent 8273735
Litigation summary
Past and pending lawsuits — plaintiffs, defendants, jurisdictions, outcomes, and notable rulings.
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No PTAB proceedings on file. This patent has not been challenged through Inter Partes Review, Post-Grant Review, or Covered Business Method review at the USPTO. The absence is itself a signal — well-asserted patents eventually attract IPRs.
Cases on file (1)
Group view →Specific litigation cases in our database that name US patent 8273735. The free-form analysis below may also discuss cases beyond this list.
- 21-900-RGAU.S. District Court for the District of Delawareterminated May 21, 2026Judgment
Defendants: Lupin Ltd. and Lupin Pharmaceuticals, Inc.
Other patents asserted: 8501730
Litigation summary
Past and pending lawsuits — plaintiffs, defendants, jurisdictions, outcomes, and notable rulings.
US Patent 8,273,735 is currently involved in multiple litigations.
Here's a summary of known cases:
Otsuka Pharmaceutical Co., Ltd. v. Lupin Ltd.
- Plaintiff(s): Otsuka Pharmaceutical Co., Ltd.
- Defendant(s): Lupin Limited and Lupin Pharmaceuticals, Inc.
- Jurisdiction: U.S. Court of Appeals for the Federal Circuit (on appeal from the District of Delaware)
- Case Number: 24-2297
- Filing Date: September 10, 2024 (Federal Circuit appeal filing date)
- Outcome/Status: On May 21, 2026, a Federal Circuit panel affirmed a district court's judgment that Lupin's tolvaptan ANDA process does not infringe Otsuka's U.S. Patent Nos. 8,273,735 and 8,501,730. The court also found the asserted method claims invalid as obvious over Kondo's 1999 paper. The district court trial opinion, issued July 31, 2024, found that Lupin did not infringe the patents-in-suit and that the asserted claims of the '735 patent were obvious.
Otsuka Pharmaceutical Co., Ltd. v. Zenara Pharma Private Limited
- Plaintiff(s): Otsuka Pharmaceutical Co., Ltd.
- Defendant(s): Zenara Pharma Private Limited, and a multitude of other defendants including Accord Healthcare Inc., Ajanta Pharma Ltd., Alembic Pharmaceuticals Inc., Alkem Laboratories Ltd., Amneal Pharmaceuticals LLC, Apotex Corp., Aurobindo Pharma Ltd., Cadila Healthcare Ltd., Hetero Drugs Ltd., Lupin Limited, Macleods Pharma USA, Inc., MSN Laboratories Pvt. Ltd., Optimus Pharma Pvt. Ltd., Prinston Pharmaceutical Inc., Raks Pharma Pvt. Ltd., Sandoz Inc., Teva Pharmaceuticals USA Inc., Unichem Laboratories Ltd., and Zydus Lifesciences Limited.
- Jurisdiction: Delaware District Court.
- Case Number: 1:26-cv-00181. (Note: An earlier case with similar parties has case number 19-1938 and 19-cv-01938-LPS, filed in 2019, last retrieved July 27, 2021 and September 21, 2022. It is possible this is related or a continuation.)
- Filing Date: February 19, 2026.
- Outcome/Status: This is a Patent - Abbreviated New Drug Application (ANDA) case. The case is active.
Additional cases filed in Delaware District Court (details pending further search)
- Multiple cases are listed as filed in the Delaware District Court for US8273735B2 on Google Patents and Unified Patents, but specific details (plaintiff, defendant, case number, filing date, status) beyond the jurisdiction are not immediately available without deeper search into each specific case entry. These include cases with identifiers: 1:24-cv-00740, 1:26-cv-00232, 1:25-cv-00318, 1:21-cv-00900, 1:23-cv-00710, and 1:22-cv-00513. The case 1:21-cv-00900-RGA is Otsuka Pharmaceutical Co., Ltd. v. Lupin Limited, which was appealed as 24-2297 to the Federal Circuit.
Generated 5/22/2026, 12:01:56 AM