About Anthrogen Anthrogen is engineering post-modality biology. Today's modalities reflect historical contingencies in biological progress, not fundamental categories. We develop the AI systems that design modular biological machines and the experimental infrastructure to instantiate them. We're a small, high-density team in San Francisco building frontier AI and the biological systems to validate it, and we care most about people who move fast, go deep, and pick up whatever the problem needs. The role A molecule can work in a dish and fail in a living system for an entirely different reason. It may not reach the tissue, persist long enough, or act in the biological context we expected. We want a scientist who can distinguish those explanations and design the experiment that tells us what to do next. You'll own in-vivo research for our designed biological systems, from selecting appropriate models to interpreting exposure, activity, and tolerability together. This is a hands-on scientific role, not just study coordination. You'll work with the rest of Platform and our ML researchers to make the results useful for design, including when a study does not support the original hypothesis. What you'll do • Define the question each study needs to answer, choose an appropriate model, and establish endpoints and an analysis plan before execution. • Design and execute studies with internal colleagues and external partners as appropriate, maintaining ownership of experimental quality and interpretation. • Connect exposure and tissue distribution to target engagement and functional outcomes, rather than evaluating efficacy in isolation. • Investigate differences between in-vitro and in-vivo behavior and translate them into testable changes to the molecule or experimental approach. • Build reproducible workflows for sample collection, downstream measurements, and analysis, in coordination with the scientists running those assays. • Plan and conduct work within approved animal-care protocols, with appropriate oversight, humane endpoints, and careful use of animals. Who you are • You have independently driven rigorous in-vivo research and can defend the model selection, controls, analysis, and conclusions, not just describe the procedures you performed. • You bring deep hands-on experience in a relevant model system and understand both its practical limitations and what it can tell us about human biology. • You can reason about pharmacokinetics, pharmacodynamics, and biological mechanism together, and distinguish insufficient exposure from lack of activity. • You take experimental design seriously: randomization, blinding where feasible, justified sample sizes, and explicit handling of variability. • You combine scientific independence with meticulous execution, documentation, and a strong commitment to animal welfare. Moving quickly does not mean relaxing those standards. Bonus points • Experience evaluating engineered proteins or protein-based systems in vivo. • Depth in oncology, immunology, or another disease area relevant to engineered biological interventions. • Experience developing translational biomarkers or connecting tissue-level measurements to a proposed mechanism of action. • Strong quantitative analysis skills and experience working productively with external research partners. Logistics Full-time, onsite in San Francisco. Equity: 0.05-0.5%.