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Amunix

Biotech & Life Sciences · San Francisco, United States · Founded 2006

Amunix Pharmaceuticals operates as a clinical-stage immuno-oncology company, concentrating on the development of therapeutics for patients with cancer. Founded in 2006 by Volker Schellenberger and the late Willem "Pim" Stemmer, the firm initially focused on leveraging its proprietary XTEN technology to extend the half-life of partnered drugs. A significant shift in strategy occurred in 2018 when Frazier Life Sciences acquired a majority stake, refocusing the company on developing its own pipeline of conditionally active biologic drug candidates. The company's core business revolves around its proprietary technology platforms designed to overcome the toxicity challenges associated with potent cancer therapies. Its Pro-XTEN platform is a universal, protease-releasable masking technology. This approach allows biologic drugs, such as T-cell engagers (TCEs) and cytokines, to circulate in an inactive or "stealth" mode. The drugs are engineered to be preferentially activated by proteases within the tumor microenvironment, aiming to concentrate the therapeutic effect on cancerous tissues while sparing healthy cells. This mechanism is intended to reduce severe side effects, like cytokine release syndrome, that have limited the use of other immuno-oncology treatments. The business model prior to its acquisition involved both in-house pipeline development and technology licensing to other biopharmaceutical companies. Its primary clients are large pharmaceutical firms seeking to enhance their oncology pipelines. A major milestone was its acquisition by Sanofi, announced in December 2021 and completed in February 2022. Sanofi acquired Amunix for an upfront payment of approximately $1 billion, with potential for an additional $225 million in milestone payments. This acquisition integrated Amunix's platforms, including XPAT (TCEs) and XPAC (cytokines), and its lead candidate, AMX-818—a masked HER2-directed T-cell engager—into Sanofi's extensive oncology research and development portfolio. Keywords: immuno-oncology, T-cell engagers, cytokine therapies, Pro-XTEN, masked biologics, cancer therapeutics, drug delivery, tumor microenvironment, protein engineering, Sanofi acquisition