THE MISSION Drug discovery has a translation problem: more than 95% of drugs that succeed in animal models fail in humans. We're building the alternative: human-first drug discovery, powered by organoids and AI, running on real human biology from the very first experiment. Our platform is 87% concordant with clinical patient data - a vast improvement over the 3% translational success rate of animals. We’ve demonstrated the ability to model immunotoxicology, immunogen stimulation, and two autoimmune diseases with more on the way. Numerous pharma partners including 3 Fortune 500 companies are already using the platform. We've raised ~$30M from AIX Ventures, Marc Benioff, Jeff Dean, and Y Combinator. With the FDA Modernization Act 3.0 and the FDA's March 2026 validation framework, the regulatory tailwinds only continue to get stronger. The opportunity ahead of the company is generational: build the first scaled engine for generating real human biological data, and use it to fundamentally change how medicines are discovered. THE ROLE As Principal Scientist, you will lead the science at our San Francisco site. You will manage our team of scientists and research associates, set experimental strategy, and own the scientific decisions that determine where we invest our experimental effort. You will remain personally at the bench on the hardest problems. Your first priority is scientific: deepening our understanding of how our organoid models behave across donors, conditions, and operators, building the reference data and controls that let the team interpret results with confidence, and bringing that rigor to the workflows running at the site. From that foundation, you will own assay development and maturation, technology transfer from R&D, control strategy, characterization, optimization, and readiness for routine execution on the platform. You will also serve as the scientific lead for our external partner programs, designing them well, interpreting them rigorously, and standing behind the results with our partners. WHAT YOU'LL OWN SCIENTIFIC LEADERSHIP - Lead the scientific team at our San Francisco site, including hiring, managing, and developing scientists and holding a high bar for experimental rigor and pace. - Set scientific direction and experimental strategy for the platform, and bring competing interpretations to a clear conclusion. - Run regular data review with the team, distinguishing biological effects from technical or process effects and driving toward the experiment that resolves the question. - Establish high standards for experimental design, controls, documentation, reproducibility, and scientific decision-making, and hold the team to them. - Facilitate productive scientific disagreement and reach clear conclusions quickly, without suppressing dissent or letting debate stall the work. - Serve as the scientific lead for external partner programs, from experimental design through data delivery. - Remain close to the bench and personally engage in difficult experimental and troubleshooting work. ASSAY AND PROCESS DEVELOPMENT - Build biological systems from first principles, taking models from concept to working, characterized assays, and deepening the ones already running. - Own the development and maturation of biological assays and workflows intended for execution on the Parallel Bio platform. - Translate early R&D assays into robust, repeatable, scalable experimental processes. - Develop and execute characterization and optimization strategies for complex organoid and cell-based assays. - Identify critical assay and process parameters and understand how they influence biological outputs. - Design experiments that establish appropriate operating ranges, robustness, and sources of variability. - Lead troubleshooting of complex biological and process failures using structured, hypothesis-driven experimentation. TECHNOLOGY TRANSFER AND PLATFORM READINESS - Define and build the framework for transferring assays and biological processes from R&D into development and ultimately routine Technical Operations. - Define clear entry and exit criteria for each stage of assay maturation and technology transfer. - Establish objective acceptance criteria for platform readiness, including controls, expected ranges, reproducibility requirements, and system suitability. - Ensure transferred assays have sufficient documentation, reference data, controls, and scientific understanding to support reliable execution. - Partner with Technical Operations to ensure new processes can be executed reproducibly by trained operators rather than only by their original developers. - Lead or support comparability studies when assays, instruments, workflows, reagents, software, or biological inputs change. SCALE-UP AND ROBUSTNESS - Develop strategies for scaling biological workflows from small exploratory experiments into higher-throughput platform processes. - Understand and reduce variability introduced by operators, instruments, automation, reagents, donors, biological materials, and environmental conditions. - Establish appropriate process controls and monitoring strategies for complex biological workflows. - Partner with automation and software teams to translate manual scientific workflows into automated, observable, and reproducible platform processes. - Identify where additional automation, instrumentation, software, or process controls will materially improve scientific performance. - Build processes that balance scientific rigor with throughput, cost, cycle time, and operational complexity. CROSS-FUNCTIONAL PLATFORM DEVELOPMENT - Partner closely with R&D to ensure new assays are designed with eventual scale and platform implementation in mind and are ready to tech transfer. - Partner with Technical Operations to establish reliable processes for external project execution. - Work with Platform Software, automation, hardware, and data teams to ensure biological requirements are translated into effective platform capabilities. - Contribute to platform roadmap decisions by identifying scientific and process-development capabilities required for future programs. - Support external pharmaceutical programs by ensuring platform processes are scientifically defensible, reproducible, and appropriate for the questions being asked. WHAT SUCCESS LOOKS LIKE You will help create a clear path from: Scientific concept → working model with established reference data → demonstrated assay → characterized process → scalable platform workflow → routine external execution Teams will know what constitutes a successful technology transfer and what evidence is required before an assay is considered ready for external work. When experiments fail or produce unexpected results, we will have the controls, reference data, process understanding, and scientific framework necessary to determine why. New assays will move onto the platform faster because Process Development, R&D, Technical Operations, automation, and software share clear interfaces and expectations. And as Parallel Bio scales, our biological processes will become increasingly reproducible without losing the complexity that makes human biology valuable. DAY ONE, WEEK ONE, MONTH ONE Day one Meet the scientific, Process Development, Technical Operations, automation, software, and platform teams. Immerse yourself in our organoid models, assays, workflows, instrumentation, data, and current external programs. Week one Go deep on our models, assays, protocols, instrumentation, and data. Form your own view of how the models behave, where the reference data and controls are strongest, and where additional scientific work will most improve reliability for external execution. Month one Set acceptance criteria for our core organoid workflows and build out the reference data and controls that support them. Stand up a recurring scientific review forum with the San Francisco team. Align R&D, development, and Technical Operations on ownership and decision rights, and begin driving focused characterization experiments against the highest-priority gaps. WHO YOU ARE A principal scientist. You have led bench scientists directly, developed their scientific judgment, and held them to a standard. You can reconcile competing interpretations among people who report to you and reach a decision without suppressing healthy technical disagreement. A deeply experienced experimental scientist. You have spent your career developing complex biological assays and understand how difficult it is to make living systems behave reproducibly. A builder and process developer. You ask not only whether an experiment works, but under what conditions, how often, why it fails, how variable it is, and what must be controlled to make it reliable. You enjoy taking something that works in the hands of one expert scientist and making it executable by an organization. A rigorous troubleshooter. When data are ambiguous, you design experiments that distinguish competing explanations rather than relying on intuition alone. A systems thinker. You understand that biological performance emerges from the interaction of cells, reagents, protocols, operators, instruments, automation, software, and data systems. Hands-on. You are comfortable setting scientific strategy and equally comfortable going to the bench when a difficult problem requires it. Comfortable with ambiguity. You can bring structure to immature technologies without imposing unnecessary bureaucracy or pretending uncertainty does not exist. Mission driven. You are excited by the opportunity to replace animal models with scalable human biology and fundamentally change how medicines are discovered. TECHNICAL FOUNDATION You hold a Ph.D. in Immunology, Cell Biology, Biology, Bioengineering, Biomedical Engineering, Molecular Biology, or a related discipline, with typically 10 to 15 or more years of relevant experience developing complex biological assays, models, and platforms. You have demonstrated significant experience in several of the following areas: - Deep immunology expertise and hands-on work with complex human in vitro models, organoids, primary immune cells, or advanced mammalian cell culture. - Direct management of bench scientists, including setting scientific direction, running data review, and developing scientific judgment in a team. - Building biological systems from 0 to 1 and adapting them onto automated or higher-throughput platforms. - Experience building Process Development functions or technology-transfer frameworks in an early-stage biotechnology company. - Assay development, characterization, optimization, and technology transfer. - Identifying and controlling biological and technical sources of variability. - Developing assays or processes for automated or high-throughput environments. - Translating early-stage R&D methods into robust workflows used by other scientists or operational teams. - Establishing controls, acceptance criteria, reference standards, or system-suitability approaches for biological assays. - Leading technically complex investigations and experimental troubleshooting. Equivalent combinations of education and experience will also be considered. BONUS POINTS - Significant experience developing organoids, immune-cell assays, advanced human cell models, or other highly variable biological systems. - Experience scaling biological workflows onto automated laboratory platforms. - Experience with Design of Experiments, process characterization, capability analysis, or Quality by Design approaches. - Experience working in regulated, quality-controlled, or highly documented scientific environments. - Experience supporting pharmaceutical or biotechnology partners and translating external scientific questions into executable platform workflows. - Experience partnering deeply with robotics, automation, software, data science, or machine-learning teams. Parallel Bio is building human-first drug discovery: 10x faster, 1000x cheaper, 0 animals killed. Parallel Bio is an equal opportunity employer committed to fostering an inclusive and respectful workplace. We encourage applications from individuals of all backgrounds, regardless of age, gender, ethnicity, religion, disability, or sexual orientation.