Director, Medicinal Chemistry

Position Title:

Director, Medicinal Chemistry

Reports to:

Vice President, Medicinal Chemistry

Status:
Regular, Full-time, Exempt

Location:

South San Francisco, California (on-site / hybrid)

Summary:

The Director, Medicinal Chemistry is responsible for co-leading a full-phase small molecule antiviral discovery program from lead optimization through candidate nomination, and for contributing design ideas and scientific judgment across the rest of the medicinal chemistry portfolio.

Assembly Biosciences (Nasdaq: ASMB) is a clinical-stage biotechnology company developing small molecule therapeutics for serious viral and liver diseases. Our pipeline spans hepatitis B virus (HBV), hepatitis delta virus (HDV), herpes viruses, and additional antiviral targets, supported by a collaboration with Gilead Sciences. We are a dynamic, science-driven organization where individual scientists have visible and direct impact on company development.

The medicinal chemistry group is deliberately small, and each member co-leads at least one full-phase discovery program while also driving early-phase programs. All wet chemistry is executed through our designated CRO partners. Our internal chemists are responsible for Med Chem strategy, compound design, and rigorous oversight of external executions to ensure direction, focus, and productivity. The Director will be expected to contribute scientific input to programs beyond his/her own;

the ability to work generously and effectively in a team setting is as critical as individual technical excellence.

Specific responsibilities include, but are not limited to

• Co-leading a full-phase small molecule discovery program: own the Med Chem strategy with a program co-lead, drive the design–synthesis–test–analysis cycle, and advance the program through lead optimization to development candidate nomination
• Designing new target molecules and chemical series to build structure-activity relationships, applying property-based and structure-based design in close partnership with computational chemistry and structural biology scientists
• Directing and rigorously managing external synthetic chemistry resources at CROs — setting chemistry priorities, reviewing and troubleshooting synthetic routes, safeguarding data quality and compound integrity, and delivering on timelines across multiple time zones
• Integrating virology, biochemistry, DMPK, and safety data into compound design; diagnose and resolve DMPK liabilities (metabolic stability, permeability, efflux and transporters, protein binding, CYP inhibition/induction and DDI risk) and apply PK/PD reasoning to define target exposures and dosing hypotheses
• Providing scientific input, design ideas, and constructive feedback to other discovery programs in various team settings
• Contributing to early-phase discovery, including target and hit triage, hit-to-lead progression, and evaluation of new chemical starting points and modalities
• Exercising sound, data-driven decision making on series progression, resource allocation and go/no-go calls, with a consistent bias toward advancing project goals
• Being resourceful in acquiring the right tools to solve problems — identifying and securing the computational, biophysical, structural, analytical or synthetic capabilities a program needs, internally or externally
• Actively participating in multidisciplinary teams, collaborating closely with virology, DMPK, computational chemistry, informatics, pharmacology, toxicology and CMC colleagues
• Presenting research updates and recommendations clearly to project teams, R&D leadership and external partners
• Reviewing patent literature and work with company patent attorney on invention disclosures, patent generation, and filings to build and defend a strong…