Full-Time

Principal Scientist

Posted on 8/6/2025

Xaira Therapeutics

Xaira Therapeutics

51-200 employees

AI-powered protein design for therapeutics

Compensation Overview

$164k - $205k/yr

+ Bonus + Equity

Daly City, CA, USA

In Person

Category
Biology & Biotech (2)
,
Requirements
  • Ph.D. or M.S. with extensive, relevant experience in molecular biology, biochemistry, structural biology, or a closely related scientific discipline.
  • Clinical Development Expertise: Demonstrated and proven track record in successfully advancing biologics through various stages of development, spanning a diverse range of disease indications. This includes a deep understanding of the regulatory landscape and the challenges inherent in bringing novel therapeutics to market.
  • Antibody Optimization: Hands-on, practical experience in the multiparameter optimization of antibodies, specifically focusing on enhancing both affinity and developability characteristics.
  • Protein Purification Mastery: Advanced expertise in a comprehensive array of protein purification techniques, including but not limited to affinity chromatography, ion exchange chromatography, hydrophobic interaction chromatography, and size exclusion chromatography. Proficiency extends to the operation and troubleshooting of modern chromatography hardware and software, such as Cytiva AKTA systems and Agilent HPLC platforms.
  • Assay Automation and Familiarity: Familiarity with and demonstrated ability to automate a variety of antibody binding assays, including ELISA, SPR, and FACS. This includes knowledge of robotic platforms and high-throughput screening methodologies.
  • Molecular and Cell Biology Foundations: Profound proficiency in core molecular and cell biology techniques, encompassing mammalian tissue cell culture (aseptic technique, cell line maintenance, transfection) and fundamental molecular biology laboratory skills (PCR, cloning, gel electrophoresis).
  • Analytical Acumen and Attention to Detail: Exceptional analytical and problem-solving abilities, coupled with a meticulous attention to detail in experimental design, execution, and data analysis.
  • Communication Excellence: Strong written and verbal communication skills, with the distinct capacity to clearly and concisely articulate complex scientific concepts, data, and findings to diverse audiences.
  • Collaborative and Team-Oriented: A highly collaborative spirit with the proven ability to thrive in dynamic, multidisciplinary team environments. This includes actively promoting cooperation, fostering knowledge exchange, and contributing positively to a shared scientific mission.
Responsibilities
  • Strategic Program Advancement: Play a pivotal role in the initiation and progression of programs toward clinical development by fostering close collaboration with the AI Design and Disease Biology teams. This involves aligning scientific strategies with program objectives to ensure a seamless transition from discovery to development.
  • Binder Discovery and Optimization: Spearhead efforts in identifying critical epitopes of interest, establishing robust binder screening workflows, and meticulously optimizing molecules for drug discovery. This encompasses the design and execution of high-throughput screening assays, characterization of binding affinities, and rational engineering to improve drug-like properties.
  • Molecule Design and Characterization: Leverage identified binders to design advanced molecules with optimized functional properties. This includes fine-tuning Fc functionality for desired effector functions, engineering bispecific arms for enhanced targeting and efficacy, and overseeing the purification, comprehensive biophysical characterization, and functional testing of these molecules. The ultimate goal is to define ideal properties that qualify these molecules as strong developmental candidates.
  • Disease Mechanism Elucidation: Actively participate in a collaborative team environment to design and execute rigorous studies aimed at unraveling the underlying mechanisms of disease (MOA). This will involve a blend of innovative in vitro experiments, utilizing advanced cell-based assays and biochemical techniques, and insightful in vivo studies, employing relevant animal models to validate hypotheses and identify therapeutic targets.
  • Technical Reporting and Dissemination: Contribute significantly to the preparation of high-quality technical reports and presentations. This includes summarizing experimental findings, interpreting complex data, and effectively communicating scientific insights to both internal stakeholders and external collaborators, ensuring clear and concise documentation of research progress.
  • Scientific and Technological Stewardship: Maintain an up-to-date understanding of the latest advancements and emerging trends in the fields of antibody engineering, protein design, and related disease areas. This commitment to continuous learning ensures the application of cutting-edge methodologies and insights to accelerate drug discovery efforts and maintain a competitive edge.

Xaira Therapeutics uses artificial intelligence to transform drug discovery and development. It builds a pipeline of protein- and antibody-based therapeutics by combining generative AI models from the IPD lab (notably RFdiffusion and RFantibody) with large, multidimensional biological data. The company designs novel proteins and antibodies from scratch to target difficult, previously undruggable biology, then validates and evolves these molecules through iterative data generation that improves its biological foundation models. Unlike many entrants that offer research services, Xaira aims to own and advance its own therapeutic pipeline across multiple modalities, rather than solely providing platforms. The goal is to deliver effective new medicines faster and with a lower chance of failure by integrating AI-driven design, expansive data, and expert leadership.

Company Size

51-200

Company Stage

Late Stage VC

Total Funding

$1B

Headquarters

Brisbane, California

Founded

2023

Simplify Jobs

Simplify's Take

What believers are saying

  • Rachel Lane closed Genentech and Sanofi partnerships at Belharra, now drives Xaira deals.
  • Focus on inflammatory diseases aligns with high-priority pharma therapeutic targets.
  • 73,075 sq ft San Francisco expansion by July 2025 supports rapid scaling.

What critics are saying

  • Isomorphic Labs' $600M Series A in March 2025 erodes Xaira's first-mover edge.
  • Xaira's $1B burn rate triggers liquidity crisis without Series B by mid-2027.
  • Public X-Atlas release lets Recursion reverse-engineer models within 12 months.

What makes Xaira Therapeutics unique

  • Xaira leverages RFdiffusion and RFantibody from David Baker's IPD for de novo protein design.
  • X-Cell model with 4.9 billion parameters predicts perturbations on 25.6 million transcriptomes.
  • X-Atlas/Pisces dataset is largest public genome-wide CRISPRi Perturb-seq resource.

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Benefits

Flexible Work Hours

Stock Options

Company Equity

Growth & Insights and Company News

Headcount

6 month growth

0%

1 year growth

1%

2 year growth

2%
Business Wire
Mar 26th, 2026
Xaira Therapeutics appoints Rachel Lane as SVP to lead business development and AI drug discovery partnerships

Xaira Therapeutics has appointed Rachel Lane as Senior Vice President of Business Development and Operations. She will oversee business development strategy and drive partnerships integrating machine learning with therapeutic development. Lane brings over a decade of biotech leadership experience as an operator and investor. Most recently, she served as Chief Business Officer at Belharra Therapeutics, where she closed major platform partnerships with Genentech and Sanofi. She previously worked at Versant Ventures and holds a PhD in Molecular Genetics and Cell Biology. This month, Xaira launched X-Cell, its virtual cell model trained on 25.6 million perturbed single-cell transcriptomes. The 4.9 billion-parameter model predicts outcomes of genetic perturbations, marking progress towards transforming drug discovery into a predictive engineering discipline.

Endpoints News
Mar 18th, 2026
With its first AI model release, xaira tests scaling laws in virtual cells.

With its first AI model release, xaira tests scaling laws in virtual cells. Senior biopharma correspondent. Biotech's best-funded AI startup detailed its first AI model on Tuesday, giving a glimpse at what it's been doing since launching out of stealth nearly... Get free access to a limited number of articles, plus choose newsletters to get straight to your inbox.

Fierce Biotech
Mar 17th, 2026
Xaira COO reveals $1B AI biotech targets inflammatory and immunological diseases

Xaira Therapeutics' Chief Operating Officer Jeff Jonker has revealed the AI-driven biotech is focusing its research and development efforts on inflammatory and immunological science. The disclosure marks the first detailed insight into how the company is deploying its capital since raising $1 billion in 2024. The secretive biotech has remained largely quiet about its operations since the fundraise. Jonker's comments to Fierce Biotech provide the first public glimpse into Xaira's strategic priorities as it applies artificial intelligence to drug discovery in areas the pharmaceutical industry considers high-priority therapeutic targets.

Business Wire
Mar 17th, 2026
Xaira Therapeutics launches X-Cell virtual cell model trained on 25.6M single-cell transcriptomes

Xaira Therapeutics has launched X-Cell, its first virtual cell model, trained on X-Atlas/Pisces, the largest genome-wide CRISPRi Perturb-seq dataset ever reported. The dataset contains 25.6 million perturbed single-cell transcriptomes across seven cellular contexts, more than three times larger than Xaira's previous dataset. X-Cell uses a diffusion language model architecture with 4.9 billion parameters, making it the largest causal perturbation model to date. Unlike traditional autoregressive models, it iteratively refines predictions by progressively replacing control gene expression values with perturbed values, improving accuracy with each step. The model demonstrates state-of-the-art performance in predicting genetic perturbation outcomes, including unseen experiments across different cell types and laboratories. Xaira is making a subset of the dataset and model available to the scientific community.

Business Wire
Jul 9th, 2025
Xaira Therapeutics Announces the Appointment of Jeff Jonker as President and Chief Operating Officer

Xaira Therapeutics announces the appointment of Jeff Jonker as President and Chief Operating Officer.

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