Boehringer Ingelheim has filed two appeals against Daewon Pharmaceutical over a composition patent for the diabetes drug ingredient linagliptin, despite having previously prevailed in Daewon’s invalidation lawsuits. The unusual move is seen as a strategic bid to strengthen its legal position and prevent future challenges.

According to the Pharmaceutical Patent Research Association’s Daily Alert, Boehringer lodged the appeals on July 15 against first-instance rulings in patent invalidation suits involving Trajenta (linagliptin), Trajenta Duo (linagliptin + metformin HCl), and Esgliteo (empagliflozin + linagliptin).

The disputed patent, which expires in April 2027, covers a granule formulation of linagliptin, a DPP-IV inhibitor. Although unlisted in the official patent register, it is viewed as part of Boehringer’s “evergreening” strategy.

Daewon filed invalidation suits in 2023, prompting Boehringer to amend its claims—deleting certain elements—to maintain coverage. The Intellectual Property Trial and Appeal Board (IPTAB) issued a mixed decision, partially dismissing and partially rejecting Daewon’s claims, effectively siding with Boehringer.

Legal experts note that Boehringer’s appeal—despite winning—appears aimed at converting the “partially rejected” claims into full dismissals. While a dismissal signals claims are without merit, a rejection often reflects procedural flaws that can be corrected and refiled. The move is seen as a preemptive measure to block Daewon from bringing the suits again.

Meanwhile, generic versions of Trajenta continue to enter the market. Daewon sells its own brand, Tralitin, which generated $245,000 in the first half of 2025, compared to $13.6 million for Trajenta, according to Ubist.