Associate scientist ii, histology

Arrowhead Pharmaceuticals, Inc. (Nasdaq ARWR) is a commercial stage biopharmaceutical company that develops medicines that treat intractable diseases by silencing the genes that cause them. Using a broad portfolio of RNA chemistries and efficient modes of delivery, Arrowhead therapies trigger the RNA interference mechanism to induce rapid, deep, and durable knockdown of target genes. RNA interference, or RNAi, is a mechanism present in living cells that inhibits the expression of a specific gene, thereby affecting the production of a specific protein. Arrowhead’s RNAi-based therapeutics leverage this natural pathway of gene silencing.

Arrowhead is focused on developing innovative drugs for diseases with a genetic basis, typically characterized by the overproduction of one or more proteins that are involved with disease. The depth and versatility of our RNAi technologies enables us to potentially address conditions in virtually any therapeutic area and pursue disease targets that are not otherwise addressable by small molecules and biologics. Arrowhead is leading the field in bringing the promise of RNAi to address diseases outside of the liver, and our clinical pipeline includes disease targets in the liver and lung with a promising pipeline of preclinical candidates.

Arrowhead’s corporate headquarters is in Pasadena, CA with research and development teams in Madison, WI & San Diego, CA, and a state of the art manufacturing facility in Verona, WI. Our employees are nimble, science-driven innovators who are collaborating to bring new therapies to patients in need.

The Position

The Associate Scientist II is a key member of the Histotechnology team within the Toxicology Department. This team advances the company’s preclinical drug development by designing tissue-based study workflows and delivering high-quality histology data from animal studies. Working under the guidance of the Team Lead, the Associate Scientist II performs both routine and advanced histological methods with a high degree of independence, ensuring reproducible results and consistent section quality aligned with program needs.

This role is onsite 5 days a week in San Diego.

Responsibilities

• Plan and execute end-to-end histotechnology workflows for preclinical studies (tissue receipt, grossing/trimming, processing, embedding, microtomy, staining, imaging, and data handoff).
• Perform paraffin microtomy and cryosectioning of small and large animal tissues at 5–7 µm with consistent quality across batches.
• Conduct routine automated tissue processing and paraffin embedding across species; recognize processing issues (e.g., incomplete infiltration, tissue carryover, artifacts) and implement effective fixes.
• Run routine and special stains on automated platforms (e.g., Leica Spectra and Ventana systems) with minimal supervision; complete instrument setup, QC, and maintenance logs.
• Execute immunohistochemistry (IHC) and/or immunofluorescence (IF), including antigen retrieval, control selection, optimization, and troubleshooting; document conditions and outcomes.
• Perform high-precision sectioning at optimal parameters to ensure maximum transcript preservation and morphological stability prior to in situ hybridization staining.
• Assess tissue morphology and state; document findings accurately and recommend follow-up techniques or controls when appropriate.
• Trim tissues from multiple species according to study protocols and nomenclature; ensure accurate cassette labeling and chain-of-custody tracking.
• Support necropsy activities for small and large animals as requested, following biosafety, animal welfare, and PPE requirements.
• Maintain meticulous records in lab notebooks/ELN and, when applicable, LIMS; draft or revise SOPs, work instructions, and checklists to improve reproducibility.
• Collaborate closely with pathologists, toxicologists, and study directors to deliver large studies on time; communicate progress, risks, and mitigation plans proactively.
• Uphold laboratory safety, housekeeping, equipment calibration/preventive maintenance, and reagent inventory management.
• Provide schedule flexibility, including occasional weekend or overtime work, based on project timelines.

Requirements

• 3-5 years in Histology field or B.S in Science with 1-2 years of Histological work
• Familiarized with ELN, IHC, microtomy, basic anatomy

Preferred

• Degree from an accredited Histotechnology program, HT or HTL(ASCP) certification
• Experience validating RNAscope/miRNAscope and multiplex IHC/IF across multiple tissues/species.
• Familiarity with LIMS/ELN.
• Familiarity with digital pathology and whole-slide imaging

California pay range

$70,000—$78,000 USD

Arrowhead provides competitive salaries and an excellent benefit package.

Candidates must have current, valid authorization to work in the country where this role is located.

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