Llewellyn Cox

Llewellyn Cox is a British-American scientist, entrepreneur, and investor who has been an active builder in Los Angeles's biotech startup community for over a decade. Originally from Gillingham, Kent, England, he was educated at the Universities of Sheffield and Cardiff, earning a Ph.D. in molecular and cell biology at Cardiff University, and then moved to New York City for a postdoctoral fellowship in neuroscience at Weill Cornell Medical College. As a researcher his work spanned cell, molecular, and developmental biology and neuroscience — he is associated with the discovery of PLC-zeta (the protein that triggers egg activation at fertilization) and with identifying a novel intracellular signaling mechanism in developing neurons driven by locally synthesized proteins from trafficked mRNAs.

Cox has built much of LA's life-sciences infrastructure from the ground up. He founded Lab Launch, a non-profit network of affordable entry-level R&D wet-lab spaces for small and startup biotech companies, and co-founded BioBuilt, an LA-based biotech startup accelerator. These efforts addressed a structural gap — the lack of accessible lab space and early capital — that historically pushed LA biotech founders out of the region.

He is a co-founder and General Partner of MarsBio, a synbio/biotech/deep-tech venture fund backing pre-seed and seed companies, which he launched alongside co-founders Arye Lipman and Rob Rhinehart (creator of Soylent). MarsBio was structured in part as a public-private venture vehicle in partnership with the County of Los Angeles, aimed at keeping local biotech startups anchored in the region. (Note: MarsBio was acquired by/folded into the biotech holding company Dark Matter around 2025, and its publicly listed team has since changed; Cox's most active GP investing appears to date to the fund's earlier vintage.)

Alongside his investing and ecosystem work, Cox holds a part-time faculty appointment at the Keck School of Medicine of USC (Department of Translational Genomics / Cancer Biology), where he lectures on pharmaceutical commercialization and science communications, and has served as USC's Executive Director of Corporate Relations, building industry partnerships around university research.

• Stage: Pre-seed and seed (occasionally seed-plus), writing first checks at the earliest stages.
• Check size: Roughly $250K–$500K per company.
• Core thesis: Back founders "using biology as a manufacturing tool" across health and environmental technology — what MarsBio frames as backing "relentless founders with uncompromising visions for the future of biology."
• Sectors: Synthetic biology, therapeutics (immunology, oncology, neuroscience), bio-enabling research tools and bioelectronics, the future of food, materials science, and agriculture.
• Hands-on at the earliest stage: The fund emphasizes engaging deeply with founders from day one and helping them scale, reflecting Cox's own track record of building lab space, accelerators, and community for first-time biotech founders.
• Geographically intentional: A stated motivation is to keep promising biotech startups rooted in Los Angeles rather than losing them to the Bay Area or Boston "black hole."