Principal Scientist (Cell Line Development)

Exelixis Inc; Alameda (CA); On-site; USD 150,000 - 213,000; Full time

Benefits offered by this job

401(k) plan

Medical, dental & vision insurance

Life and disability insurance

FSAs

Discretionary annual bonus

Stock purchase plan

Long-term incentives

Vacation & holidays

Sick days

Job summary

Exelixis Inc. seeks a senior BiotherapeuticsCell Line Development Scientist to advance CHO‑based mammalian cell lines for early‑phase biologics and ADC candidates. You will design vectors, engineer host cells, perform transfections, cloning, and stability assessments while ensuring monoclonality and product quality.

The role emphasizes independent execution, cross‑functional collaboration, data-driven decisions, and rigorous documentation in a fast‑paced biotech environment.

Qualifications

• PhD in molecular biology, biochemistry, biology, or microbiology with 5+ years in biotech/pharma OR
• MS with 9+ years OR
• BS with 11+ years of relevant experience.

Responsibilities

• Design and execute CHO-based cell line development experiments for biologics progressing to clinical development.
• Improve expression systems and workflows through novel technology and boundary-pushing approaches.
• Perform cell line development steps: transfection, single-cell cloning, monoclonality documentation, screening and progression, and cell banking.
• Develop vectors and genetic components; engineer host cells and optimize cell line development processes.
• Identify emerging practices in biologics cell line development to guide scientific strategy.
• Represent the cell line development team on cross-functional projects and communicate results clearly.

Skills

Molecular biology

CHO cell culture

Transfection methods

Monoclonality analysis

Vector design

Regulatory knowledge

Data analysis

Communication skills

Education

PhD in molecular biology

MS in related field

BS in biology

Tools

HPLC

LC/MS

CE

Job description

About Exelixis

Every Exelixis employee is united in an ambitious cause: to launch innovative medicines that give patients and their families hope for the future. Our 25 years in the biotech sector have established a proven track record of resilience, guided by our commercial success and commitment to research in drug discovery, clinical development, and commercialization. We are expanding our global partnerships and investing in R&D to discover breakthroughs for difficult‑to‑treat cancers. Cancer is our cause. Make it yours, too.

Job Purpose

As a member of the Biotherapeutics group, the incumbent will support discovery and preclinical development by leveraging skills in recombinant antibody and bispecific antibody production and purification/characterization. The role focuses on delivering high‑performing, high‑quality mammalian cell lines that enable early‑phase biologics manufacturing for potential therapeutic candidates or ADCs. Duties include designing and testing vector constructs, engineering host cells, and conducting transfection, selection, and clone generation campaigns in CHO cells, with a deep theoretical understanding of recombinant protein expression to guide improvement of titer in stable cell lines.

Key Responsibilities

• Design and execute experiments to develop CHO‑based cell lines for biologic therapeutics progressing into clinical development.
• Design complex experimental approaches to improve expression systems and workflows through innovation and new technology.
• Perform therapeutic CHO cell line development processes, including transfection, single‑cell cloning, imaging analysis to document monoclonality, clone screening and progression, characterization, and cell banking and stability assessment of cell banks using state‑of‑the‑art equipment.
• Develop improved expression vectors and genetic components, host cell line engineering, and/or cell line development process optimization.
• Identify emerging practices for biologics therapeutic cell line development and manufacturing to shape scientific strategies and continue innovation.
• Represent the cell line development team on cross‑functional projects, making decisions for cell line activities and effectively communicating results, progress, and plans.
• Comply with company health and safety policies and general laboratory practices.

Supervisory Status

No supervisory responsibilities. Individual contributor role.

Education, Experience and Knowledge

• PhD in molecular biology, biochemistry, biology, or microbiology AND a minimum of five (5) years of experience in the biotechnology/pharmaceutical industry – OR
• Master’s degree in the same disciplines AND a minimum of nine (9) years of experience – OR
• Bachelor’s degree in the same disciplines AND a minimum of eleven (11) years of experience.

Candidate must be a highly skilled, hands‑on, detail‑oriented professional able to contribute with minimal onboarding.

Required Technical Skills

• Proficient in molecular biology, vector construction, and genetic elements influencing recombinant antibody/bispecific expression.
• Experience with stable CHO expression platforms, able to articulate pros and cons and recommend suitable platforms for manufacturing cell lines.
• Well versed in transfection methodologies, screening, and selection workflows.
• Deep understanding of regulatory requirements for demonstrating monoclonality.
• Experience culturing CHO cells in shake flasks, spin tubes, deep‑well plate fed‑batch processes, and optionally AMBR fed‑batch processes.
• Experience in single‑cell cloning and imaging technologies to prove monoclonality.
• Experience running titer determination and standard downstream product quality assessments.
• Authoring and reviewing cell line development reports, summaries and presentations.
• Experience in analytical techniques such as HPLC, LC/MS, and/or CE is a plus.
• Familiarity with automation platforms and data analysis tools is a plus.
• Excellent communication, organization, and documentation skills.
• Ability to design and execute activities aimed at producing and characterizing recombinant antibodies and bispecifics, interpret experimental data, and formulate conclusions and next‑steps.
• Prior experience with electronic laboratory notebook documentation and workflow management is a plus.

Working Conditions

Primary laboratory or office environment. Potential exposure to hazardous chemicals/materials. Work may involve shift or flexible hours as required by project timelines.

Employment Compensation

Base pay range: $150,000 – $213,000 annually, adjusted for geographic region and experience. Total rewards include a 401(k) plan with company contributions, group medical, dental, and vision coverage, life and disability insurance, and flexible spending accounts.

Benefits

Eligible for discretionary annual bonus program, sales‑based incentive plan for field sales staff, company stock purchase option, and long‑term incentives. 15 accrued vacation days in first year, 17 paid holidays including a company‑wide winter shutdown in December, and up to 10 sick days per calendar year.

Equal Opportunity Employer Statement

We are an Equal Opportunity Employer and do not discriminate against any employee or applicant for employment because of race, color, sex, age, national origin, religion, sexual orientation, gender identity, status as a veteran, or basis of disability or any other federal, state, or local protected class.

For disability accommodations during application or recruitment, please email [e-mail].