Senior Principal Scientist, Drug Substance at Loyal36 — Remote

About Loyal

Loyal is a well-funded startup with teams of scientists, veterinarians, engineers, operators, and creatives. You'll help us continue on our path of earning FDA approval for the first lifespan extension medicine for any species — and change what's possible for the dogs we love.

About the role

Loyal is seeking a Senior Principal Scientist, Drug Substance to serve as the technical leader for drug substance process development and manufacturing from early development through commercialization. This high-impact, externally-facing role will drive drug substance process development and manufacturing, and deliver flawless execution across CDMO partners while serving as the internal subject matter expert informing cross-functional decision-making and long-term development strategy across Loyal's growing pipeline. 

You will be reporting to our VP of Manufacturing

Your daily work will include

• Lead end-to-end drug substance process development and manufacturing  for small molecule APIs  from synthetic route assessment and impurity control through scale-up, technology transfer, and commercial manufacturing readiness at CDMOs.
• Serve as the primary technical interface with drug substance CDMOs spanning partner selection, day-to-day oversight, troubleshooting, PAI preparation and performance management; ensure drug substance supply continuity, including second source qualification and starting material supply risk strategy, in support of clinical and commercial manufacturing.
• Lead RSM designation, ICH Q11 assessments, impurity fate and purge strategies and ICH M7 mutagenic impurity risk assessments; establish CQAs, CPPs, and ICH Q6A-aligned control strategies.
• Lead drug substance process validation from PPQ protocol development through batch execution and CPP/CQA verification; align PPQ timelines and batch disposition with drug product process validation and registration batch campaigns.
• Author, review, and approve drug substance CMC sections for regulatory submissions (VMF, INAD/NADA); represent drug substance CMC in agency interactions and ensure a technically integrated and consistent regulatory package.
• Partner with drug product development to translate drug substance CQAs into formulation design, excipient selection, container closure strategy and final dosage form decisions.
• Partner with analytical development to define method development, qualification, and validation strategy for drug substance release and stability testing.
• Partner with Quality to align drug substance specifications, batch disposition, and GMP compliance across CDMOs, and to support inspection and regulatory submission readiness.
• Manage drug substance post-approval change control strategy for manufacturing changes at CDMOs.

About you

• Ph.D. in Chemistry, Chemical Engineering, Biochemistry, or a related discipline.
• 12+ years of industry experience in drug substance process development and manufacturing, with demonstrated ownership from early development through regulatory submission and commercialization phase.
• Hands-on expertise in small molecule API process development, including synthetic process understanding, impurity profiling, ICH Q11 RSM assessment, and ICH M7 mutagenic impurity control.
• Proven experience selecting, managing, and technically overseeing CDMOs for small molecule drug substance development, scale-up, technology transfer and PPQ.
• Demonstrated experience authoring and defending drug substance CMC regulatory submissions (INAD/NADA, VMF or equivalent) and interacting with regulatory agencies on CMC questions.
• Deep knowledge of applicable regulatory frameworks: ICH Q7, Q8, Q9, Q10, Q11, Q6A, M7, and relevant VICH guidelines for veterinary drug substances.
• Demonstrated ability to operate effectively in a dynamic, fast-paced startup environment with a high degree of autonomy and accountability.
• Experience with large biomolecule drug substance development (peptides, proteins, or other biological entities) preferred but not required.
• Veterinary dosage form experience preferred but not required.

Salary Range: $175,000 - $230,000

Loyal benefits

• Full-coverage health insurance — medical, dental and vision — for you and your dependents
• $1,000 home office equipment stipend
• $1,200/year learning budget for books, courses, etc.
• $250/month wellness budget for gym, cleaners, spa, food, etc.
• All 3-day weekends are turned into 4-day weekends 🎉
• Unlimited vacation and paid holidays
• Paw-ternity leave — adopt a dog and get a day off with your new family member 🐶
• Competitive salary
• Company equity options grant for new hires

Our values

Moonshots, derisked methodically

Opportunity is at the intersection

Expertise without ego

High agency, high humility

Lead with transparency and context

Empathy and respect for all life