Lowenstein & Weatherwax

Lowenstein & Weatherwax LLP is a highly regarded patent litigation boutique headquartered in Santa Monica, California. Recognized by Chambers USA 2026 in Intellectual Property: Patent Litigation – California, the firm is noted as the smallest among the ranked firms and one of only three newly recognized in this competitive category. It has also been named a Chambers Spotlight California firm for two consecutive years, a distinction for small and mid-sized firms delivering high-quality legal services.

The firm specializes in complex patent disputes across a broad range of technologies, including semiconductors, computer hardware and software, telecommunications, digital video, medical devices, and electronic commerce. Lowenstein & Weatherwax primarily focuses on defending patent owners and technology companies against validity challenges, demonstrating a strong preference for the defendant side, with 7 out of its 8 tracked appearances being for defendants.

Lowenstein & Weatherwax has built a national reputation, particularly for its robust Patent Trial and Appeal Board (PTAB) and inter partes review (IPR) practice. The firm has handled over 400 IPR/CBM proceedings and nearly 80 Federal Circuit appeals. Notably, in Infineon Technologies Americas Corp. v. Mosaid Technologies Inc. (IPR2025-01456), the PTAB Director denied institution of Infineon's IPR challenge, representing a significant defense outcome for Mosaid. The firm also secured three non-institutions of IPR petitions on behalf of Security First Innovations LLC. While representing DivX LLC in Unified Patents v. Divx LLC, the Federal Circuit affirmed the unpatentability of DivX's adaptive bitrate streaming patent following a PTAB decision.

Founding and co-Managing Partners Nathan Lowenstein and Kenneth Weatherwax are key leaders in the firm's practice. Nathan Lowenstein was ranked by Patexia as the #1 attorney in Patent Owner Performance among 5,650 PTAB practitioners nationwide for the 2020-2025 period and is consistently recognized by IAM Patent 1000. Kenneth Weatherwax is also a nationally recognized patent litigator with significant PTAB experience. Colette Woo, who became a partner in 2026, focuses on IPR and reexamination proceedings and has been recognized among top-performing patent owner-side IPR attorneys. Partners Parham Hendifar and Dennis J. Courtney also contribute to the firm's IP litigation expertise.