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§ Private Profile · 2 Tower Pl Ste 1100, South San Francisco, CA
Biopharmaceutical company developing targeted protein therapeutics for solid tumor cancers, activating immune cells in tumor environments.
Founded in 2006 by Willem P.C. "Pim" Stemmer and Volker Schellenberger, Amunix is a South San Francisco, California-based biotechnology company developing targeted immuno-oncology therapeutics for solid tumors. The enterprise utilizes its proprietary XTEN technology platform to engineer masked T cell engagers, like lead candidate AMX-818, designed to activate exclusively within the tumor microenvironment to minimize systemic toxicity. Prior to its exit, the biopharma secured approximately $190 million in total venture funding, including a $73 million Series A and a $117 million Series B, backed by institutional investors such as Omega Funds and Frazier Healthcare Partners. Led by CEO Angie You, the company previously licensed its half-life extension technology to pharmaceutical partners like Biogen. In December 2021, pharmaceutical giant Sanofi acquired Amunix for an upfront payment of $1 billion, alongside up to $225 million in future milestone payments.
Amunix has raised $193.0M across 2 funding rounds.
Key people at Amunix.
Amunix was founded in 2006 by Volker Schellenberger (Co-Founder, President, and CTO).
Amunix has raised $193.0M in total across 2 funding rounds.
Key people at Amunix.
Amunix was founded in 2006 by Volker Schellenberger (Co-Founder, President, and CTO).
Amunix has raised $193.0M in total across 2 funding rounds.
Amunix's investors include Viking Global Investors, Frazier Healthcare Partners, ArrowMark Partners, Avidity Partners, Bain Capital Life Sciences, BlackRock, CaaS Capital Management, Casdin Capital, Franklin Templeton, Janus Henderson Investors, Longitude Capital, Omega Funds.
Amunix has raised $193.0M across 2 funding rounds. Most recently, it raised $120.0M Series B in March 2021.
| Date | Company | Round | Lead Investor(s) | Co-Investor(s) |
|---|---|---|---|---|
| Oct 1, 2013 | Versartis | $20.0M Series D | Srinivas Akkaraju | Advent Life Sciences, Samsara BioCapital, Advent Venture Partners, Aisling Capital, Index Ventures, NEW Leaf Venture Partners |
| Feb 1, 2011 | Versartis | $21.0M Series B | Srinivas Akkaraju | Advent Life Sciences, Samsara BioCapital, Shahzad Malik, Kevin Johnson |
| Date | Round | Lead Investors | Other Investors | Status |
|---|---|---|---|---|
| Mar 1, 2021 | $120M Series B | Viking Global Investors | Frazier Healthcare Partners, ArrowMark Partners, Avidity Partners, Bain Capital Life Sciences, BlackRock, Caas Capital Management, Casdin Capital, Franklin Templeton, Janus Henderson Investors, Longitude Capital, Omega Funds, Polaris Partners, Redmile Group, Venrock | Announced |
| Mar 1, 2020 | $73M Series A | Otello Stampacchia | Frazier Healthcare Partners, Casdin Capital, Delian Capital, David Hirsch, Polaris Partners, Redmile Group, TWO River, Venrock | Announced |
Amunix Pharmaceuticals is a biopharmaceutical company developing masked, protease-activated pro-drugs for immuno-oncology, focusing on T-cell engagers (TCEs) and cytokines to treat solid tumors.[1][2][3] It leverages proprietary platforms like Pro-XTEN, XPAT® (for TCEs), and XPAC™ (for cytokines) to create therapeutics that remain inactive until activated in the tumor microenvironment, addressing on-target/off-tumor toxicity and enabling safer, more effective dosing with extended half-life and low immunogenicity.[2][3][4][5] The company serves cancer patients with HER2-expressing solid tumors and others, solving key challenges in potent immune activators that limit efficacy due to systemic toxicity; its lead candidate, AMX-818 (XPAT® TCE), is in IND-enabling studies, with additional programs in optimization.[3][4] Amunix raised $117M in Series B financing in 2024 from Bain Capital Life Sciences and others to advance its oncology pipeline, following technology licensing deals with Roche and prior collaborations with Sanofi and Merck.[4][5][7]
Founded in 2006 in South San Francisco, CA, Amunix initially developed the XTEN® platform—a synthetic, unstructured polypeptide for extending serum half-lives of protein therapeutics with low immunogenicity, validated through partnerships like Merck, Roche, and Sanofi (e.g., in efanesoctocog alfa for hemophilia A).[7][8][5] The idea emerged from needs in protein engineering for longer-acting biologics; early traction came via technology licensing, positioning Amunix as a platform provider.[7][5] Under CEO Angie You, Ph.D., it pivoted around 2021-2024 from pure licensing to internal oncology drug discovery, building a pipeline of Pro-XTEN pro-drugs after Sanofi's failed $1B acquisition attempt in 2021, which highlighted the tech's promise amid toxicity hurdles in immuno-oncology.[6][7][2] This shift capitalized on clinical validation of XTEN and protease-releasable masking for tumor-selective activation.[4][5]
Amunix rides the immuno-oncology wave, targeting bispecific TCEs and cytokines for solid tumors where traditional therapies fail due to toxicity, amid a market shift toward conditionally active biologics.[2][6][7] Timing aligns with post-2021 learnings from cytokine/TCE setbacks (e.g., cytokine release syndrome), as protease-activated pro-drugs gain traction for precision activation.[3][4] Favorable forces include rising demand for safer IO agents, validated half-life extension tech, and partnerships validating XTEN beyond oncology; Amunix influences the ecosystem by licensing platforms, accelerating partner pipelines while building its own, potentially reshaping TCE/cytokine adoption in solid tumors.[5][7]
Amunix is poised to advance AMX-818 into clinical trials post-IND, with XPAC cytokines like IL12 following, fueled by 2024 Series B funding amid a pivot to proprietary oncology assets.[3][4] Trends like AI-driven protein design and tumor-microenvironment targeting will amplify its Pro-XTEN edge, potentially drawing more Big Pharma deals or acquisition interest akin to Sanofi's 2021 bid.[6][7] Its influence may evolve from tech licensor to full-fledged oncology player, delivering breakthrough TCEs/cytokines that unlock solid tumor potential—transforming Amunix from half-life innovator to toxicity conqueror in cancer therapy.[2][5]
