Director, Medicinal Chemistry

POSITION SUMMARY

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), herpesviruses, 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 MedChem 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 MedChem 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 proprietary estate

Mentoring and developing colleagues and CRO partner scientists, and contributing to a collegial, rigorous scientific culture

Other duties as assigned

This job description outlines the primary duties and responsibilities of the role; however, it is not intended to be all-inclusive. The scope of responsibilities may be modified, expanded, or adjusted at the discretion of the organization to meet evolving business needs.

Qualifications include :

PhD in synthetic organic or medicinal chemistry

Minimum of 8 years of drug discovery experience in the pharmaceutical or biotechnology industry

Demonstrated experience leading or co-leading a discovery program from hit-to-lead, lead optimization, to development candidate nomination

Demonstrated creativity in drug design and problem solving, including the ability to generate novel chemical matter and new approaches

Working knowledge of PK and PK/PD concepts and their application to compound design and candidate selection

Demonstrated ability to diagnose and solve DMPK issues in a lead optimization setting

Experience with structure-based drug design and the practical use of protein structures and computational tools in compound design

Demonstrated sound decision making, particularly with respect to advancing project goals under real-world data and resource constraints

Resourcefulness in acquiring the appropriate tools, data and expertise required for problem solving

Demonstrated success designing and directing synthetic chemistry executed by either domestic or / and international CRO partners

Excellent written and oral communication skills, including the ability to present and defend a scientific position to cross-functional colleagues and senior leadership

Strong interpersonal skills and a genuine orientation toward teamwork; able to contribute constructively to programs he/she does not lead and to operate with minimal supervision in a fast-paced, small-company environment

Knowledge and experience in antiviral drug discovery is desirable but not required

Pay Range: $220,000 - $233,500 annualized

The stated pay range for this position reflects the San Francisco Bay Area job market. Assembly Bio establishes pay ranges based on geographic work locations. Additional factors such as academic credentials and relevant experience will influence the actual salary offered .

About Assembly Bio

Assembly Bio (NASDAQ: ASMB) is an ambitious biopharmaceutical company with cutting-edge therapeutic candidates capable of improving the lives of millions living with devastating viral and liver diseases. We have multiple ongoing clinical programs focused on the development of novel treatments for herpesviruses, hepatitis delta virus (HDV), cholestatic liver diseases and hepatitis B virus (HBV). Further, our research organization is dedicated to the discovery of new therapies to change the treatment paradigm for individuals living with serious viral and liver diseases.

We pride ourselves on creating a culture and work environment that is scientifically driven, ambitious, and collaborative. We encourage diversity of thought that leads to great innovation and are looking to add great people to our dynamic team who are driven to transform the lives of patients. We set our sights high—and pursue our goals with determination. Our unique organization stands ready to welcome talented, motivated individuals, who share our ambitions.

As an equal opportunity employer, we are committed to diversity and inclusion and will

not tolerate discrimination and harassment of any kind. All employment decisions are based on business needs, job requirements and individual qualifications, without regard to race, color, religion or belief, national, social or ethnic origin, sex (including pregnancy), age, physical, mental or sensory disability, HIV status, sexual orientation, gender identity and/or expression, marital, civil union or domestic partnership status, past or present military service, family medical history or genetic information, family or parental status, or any other status protected by the laws or regulations in the locations where we ope