Scientist I/II, Modality Engineering

Role Summary 

Lexeo is hiring a hands-on Modality Engineering Scientist to design, synthesize, and characterize oligonucleotides, bioconjugates, and AAV therapeutics for our discovery pipeline. The scientist will advance molecules from design through analytical characterization and handoff to in vitro and in vivo teams, working across chemistry, molecular biology, and pharmacology. Reporting to the Head of Cardiac Research, this role joins cardiac, neuroscience, and non-clinical scientists developing therapies for genetic heart disease and offers broad experience in multidisciplinary biopharma research. 

Primary Responsibilities

Select and manage CROs for oligonucleotide synthesis and bioconjugation, including scope, vendor guidance, data review, quality, and delivery timelines

Design and oversee oligonucleotide conjugates using peptides, antibodies, or ligands; optimize conjugation chemistry, linkers, purification, and analytical characterization

Build or outsource methods to confirm identity and assess purity using HPLC, LC-MS, SDS-PAGE, spectroscopy, and other fit-for-purpose assays

Engineer AAV capsids, regulatory elements, and transgene cassettes; conduct cloning, plasmid preparation, sequencing, and research-grade vector production

Design and screen sequence or vector/capsid with NGS readouts, applying state-of-the-art analytical methods to improve potency, selectivity, and production yield

Partner with In Vitro Pharmacology, In Vivo Physiology, Analytical DMPK, and CMC to define screening cascades, interpret data, assess developability and manufacturability, select leads, and support go/no-go decisions

Support molecule advancement through process development and formulation while identifying technical risks and recommending practical experiments or external capabilities

Write SOPs, maintain and troubleshoot instruments, document work in the ELN for intellectual property and regulatory filings, present results, and monitor platform advances 

Required Skills and Qualifications

PhD in chemistry, chemical biology, biochemistry, molecular biology, or a related field with 0–3 years of postdoctoral or industry experience; or MS with 5+ years of industry experience

Hands-on experience synthesizing, purifying, and characterizing research-scale ASOs, siRNAs, or bioconjugates using automated solid-phase synthesis, chromatography, and mass spectrometry

Working knowledge of ASO/siRNA therapeutic chemistry, backbone and sugar modifications, class-related toxicity, various delivery approaches

Strong research productivity demonstrated through publications, patent filings, or comparable technical contributions

Clear written and verbal communication skills, sound scientific judgment, and the ability to manage multiple projects in a collaborative, fast-paced team

Ability to regularly work onsite at our HQ in New York City 

Preferred Skills and Qualifications

Industry experience in a small, fast-paced biotech is highly preferred

Working knowledge of AAV biology and vector design

Hands-on experience in AAV capsid engineering, pooled library design, and NGS data analysis

Antibody- or peptide-oligonucleotide conjugate (AOC/POC) design or linker discovery 

About LEXEO

Lexeo Therapeutics is a New York City-based, clinical stage company dedicated to reshaping the path of genetic disease. By advancing pioneering science, Lexeo seeks to set a new standard in the treatment of cardiovascular and neurological genetic diseases, charting the path to patient outcomes once thought out of reach. The Company is advancing a portfolio of therapeutic candidates designed to address the underlying genetic causes of disease, including LX2006 for Friedreich ataxia (FA), LX2020 for plakophilin-2 (PKP2) arrhythmogenic cardiomyopathy, and others in devastating diseases with high unmet need. 

LEXEO Therapeutics is an EEO employer committed to an exciting, diverse, and enriching work environment.