Senior / Principal Scientist, Molecular Simulations

About the Role:FL117, a venture-backed stealth AI x bio company, is seeking a Sr. Scientist / Principal Scientist, Molecular Simulations. Here you will build the physics layer of a drug development AI platform. You will characterize how binders engage their targets and validate generated designs before they are committed to synthesis. You will work at the interface of structure-based modeling and generative ML, turning simulation output into training signals. We are looking for a hands-on simulation scientist who is comfortable owning a method end to end in a cross-functional, fast-moving team. Responsibilities: Binder Characterization: Run and interpret structural and dynamic analysis of ligand–target complexes peptides, macrocycles, nanobodies/VHHs, antibody CDRs. Pocket & Target Assessment: Characterize binding sites, including cryptic and induced-fit pockets, across the target portfolio using MD, enhanced sampling, and pocket detection methods. Design Validation: Triage generated molecules before synthesis through a combination of pose prediction and refinement, docking rescoring, binding-mode stability under MD, ligand strain and conformational ensemble analysis, and define the criteria by which a design advances or gets killed. Free Energy & Affinity Prediction: Build, validate, and own the affinity prediction workflow (relative and absolute FEP, MM-GBSA/PBSA, endpoint methods); establish its accuracy and applicability domain against measured data and report both honestly. Beyond-Rule-of-5 Properties: Model conformational behavior, intramolecular hydrogen bonding, chameleonicity, and membrane partitioning for macrocycles and other non-classical chemotypes to support oral property design. Simulation-to-ML Interface: Convert simulation output into structured signal for the generative platform in close partnership with the AI/ML team. Infrastructure & Throughput: Build reproducible, automated simulation pipelines on GPU cloud or HPC infrastructure; own system setup, parameterization, QC, and analysis at portfolio scale rather than one system at a time. Cross-functional Partnership: Work directly with medicinal chemistry, pharmacology, and external structural biology and assay partners; turn structural hypotheses into testable designs, feed returning data back into corrected models, and flag clearly where predictions are unreliable. Must-have Qualifications: PhD in computational chemistry, biophysics, chemical physics, structural biology, or a related field; MSc with equivalent industry depth considered 4+ years of post-PhD molecular simulation experience, at least part of it in a drug discovery setting (Sr. Scientist); 6+ years with demonstrated ownership of a method or platform (Principal) Deep hands-on expertise in classical molecular dynamics: force fields and small molecule parameterization (AMBER/CHARMM/OPLS, GAFF/OpenFF), solvation and ion treatment, equilibration protocols, and the characteristic failure modes of each. Production experience with at least one enhanced sampling or free energy framework (relative or absolute FEP/TI, metadynamics, umbrella sampling, replica exchange, or weighted-ensemble MD) including validation against measured affinities. Structure-based drug design fundamentals: docking and pose evaluation, pharmacophore and hot-spot analysis, and critical assessment of experimental and predicted structures. Strong Python, with fluency in simulation toolchains (OpenMM, GROMACS, AMBER, NAMD, or Desmond) and analysis stacks (MDAnalysis/MDTraj, RDKit); version control and reproducible workflows as habit, not aspiration. Demonstrated ability to run simulations at scale on GPU, HPC, or cloud infrastructure through automation rather than manual per-system setup. Judgment about method cost versus decision value: able to say when a multi-week free energy campaign is warranted and when docking plus a short MD run is enough. Consistent record of outstanding technical output reflected in publications, patents, or high impact internal reports Preferred Experience: Peptide, macrocycle, or other beyond-Rule-of-5 simulation: conformational ensembles, intramolecular hydrogen bonding, chameleonicity, and membrane permeability (ex: water-to-membrane transfer free energies). Experienced with target classes such as: GPCRs, protein–protein interactions, transcription factors, highly dynamic target classes. Working with predicted structures and their limitations (AlphaFold-class models, co-folding methods), and with cryptic or induced-fit pocket discovery. ML-adjacent simulation work: machine-learned force fields and potentials (ANI, MACE, NequIP-class), learned scoring functions, or generating simulation-derived features for downstream generative models. Workflow and infrastructure tooling: Snakemake/Nextflow, Airflow/Prefect/Dagster, Docker, AWS (Batch, ParallelCluster, S3), and experiment tracking (MLflow/W&B). Clear structural communication to non-specialists using PyMOL, ChimeraX, or Mol*. Please send a link to representative figures or your GitHub, if applicable. Strong presence in the computational chemistry or biophysics community through publications and conference proceedings. Please send a list of publications, if applicable. ABOUT FLAGSHIP PIONEERINGFlagship Pioneering invents and builds platform companies, each with the potential for multiple products that transform human health, sustainability and beyond. Since its launch in 2000, Flagship has originated more than 100 companies. Many of these companies have addressed humanity’s most urgent challenges: vaccinating billions of people against COVID-19, curing intractable diseases, improving human health, preempting illness, and feeding the world by improving the resiliency and sustainability of agriculture. Flagship has been recognized twice on FORTUNE’s “Change the World” list, an annual ranking of companies that have made a positive social and environmental impact through activities that are part of their core business strategies and has been twice named to Fast Company’s annual list of the World’s Most Innovative Companies. Learn more about Flagship at .At Flagship, we accept impossible missions to enable bigger leaps. Our core values guide us through uncertainty and toward lasting impact.We are an equal opportunity employer. All qualified applicants will be considered for employment without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, disability, protected veteran status, or any other characteristic protected by law.We recognize that great candidates often bring unique strengths without fulfilling every qualification. If you have some of the experience listed above but not all, please apply anyway. We are dedicated to building diverse and inclusive teams and look forward to learning more about your background and interest in Flagship.Recruitment & Staffing Agencies: Flagship Pioneering and its affiliated Flagship Lab companies (collectively, “FSP”) do not accept unsolicited resumes from any source other than candidates. The submission of unsolicited resumes by recruitment or staffing agencies to FSP or its employees is strictly prohibited unless contacted directly by Flagship Pioneering’s internal Talent Acquisition team. Any resume submitted by an agency in the absence of a signed agreement will automatically become the property of FSP, and FSP will not owe any referral or other fees with respect thereto.#LI-MB1Privacy Notice for Applicants: When you apply for a role at Flagship Pioneering or one of its portfolio companies, we collect and use personal information you provide (such as your name, contact details, work history, and application materials) to evaluate your application, communicate with you, and comply with legal obligations. Your application data is processed through Greenhouse, our applicant tracking system, and may also be reviewed using AI-assisted screening tools. We do not sell your personal information. California residents have rights under the CCPA/CPRA including to know, delete, and opt out of the sharing of their personal information. If you are located in the EU or UK, we process your data under GDPR and you have rights to access, rectify, and erase your data. To exercise your rights or for questions, contact View email address on click.appcast.io. The salary range for this role is $146,000 - $236,500. Compensation for the role will depend on a number of factors, including a candidate’s qualifications, skills, competencies, and experience. FL117 currently offers healthcare coverage, annual incentive program, retirement benefits and a broad range of other benefits. Compensation and benefits information is based on FL117's good faith estimate as of the date of publication and may be modified in the future.Privacy Notice for Applicants: When you apply for a role at Flagship Pioneering or one of its portfolio companies, we collect and use personal information you provide (such as your name, contact details, work history, and application materials) to evaluate your application, communicate with you, and comply with legal obligations. Your application data is processed through Greenhouse, our applicant tracking system, and may also be reviewed using AI-assisted screening tools. We do not sell your personal information. California residents have rights under the CCPA/CPRA including to know, delete, and opt out of the sharing of their personal information. If you are located in the EU or UK, we process your data under GDPR and you have rights to access, rectify, and erase your data. To exercise your rights or for questions, contact View email address on click.appcast.io.