Lead Developer FullStack (ReactJS/NodeJS/Python/ML) scaling up with stock options / equities

ArcaScience builds AI that predicts the benefit-risk profile of drugs. Our platform runs 24 specialised models across a database of more than 100 billion biomedical datapoints, and it turns work that used to take pharma teams months into an assessment they can get in near real time.

Since 2018 we've grown from an idea into a company that already works with Sanofi, AstraZeneca, GSK, Takeda, ICON and the Paris Brain Institute. Our software has supported over 70,000 patients in chronic disease research and backed many regulatory submissions across 12 therapeutic areas. In 2025 we closed a $7M round to expand the platform and the team.

We're now looking for a Lead Developer to build the next generation of these products. This is a seat at the centre of the technical team, with real say in where the platform goes. The person who takes it will help define our architecture, grow the engineering team around them, and see their decisions play out over the years to come.

What you'll do

• Design and build the web apps, APIs and analysis pipelines that process complex scientific data.
• Set the technical direction for our B2B SaaS platform for AI-driven scientific analysis, making the architecture calls on security, availability and usability and standing behind them.
• Help put our AI models into production and keep them running: serving them behind our APIs, wiring up the data and training pipelines they depend on, and building the tooling to monitor their outputs once they're live.
• Shape the product itself: scoping features, gathering requirements, running user tests, validating hypotheses and iterating.
• Raise the bar for how the team works, through code review, technical standards and mentoring, and take part in hiring the engineers who join next.
• Work alongside our data science, product, design and engineering teams to keep the experience coherent end to end, and sit with the CTO and the leadership team when we decide what to build and in what order.

What we're looking for

• Strong front-end experience with React and TailwindCSS.
• Hands‑on knowledge of visualisation libraries such as Plotly, D3.js or Observable.
• Solid back‑end skills in Node.js and Python (FastAPI, Airflow).
• A track record building high‑availability, high‑performance platforms that handle heavy data processing, and the judgement to know which technical bets are worth making at an early‑stage company.
• A working understanding of how machine learning models are built and trained. You don't need to be a research scientist, but you should be comfortable collaborating with data scientists, reading a training pipeline, and knowing what it takes to get a model from a notebook into production.
• Familiarity with serving and integrating AI models in real applications: model APIs and inference, versioning, and monitoring for drift or degradation once a model is live.
• Comfort owning the whole lifecycle, from cloud infrastructure and CI/CD through to what a feature costs to run at scale.
• Experience shipping products and a genuine interest in working with the people who use them.
• Autonomy, rigour, curiosity and initiative.

Leadership and collaboration

• 5+ years leading full‑stack projects, including experience growing and mentoring engineers.
• A history of delivering technical work that maps to real business goals, and of translating a company roadmap into a technical one.
• The ability to explain technical decisions clearly to non‑technical colleagues, including in front of a client or an executive.
• Fluent English and the interpersonal skills to work across functions, from the CTO to product, regulatory and customers.
• A calm, structured, empathetic way of leading in a multicultural team.
• The instinct to think a step ahead of where the company is today, and to build with the platform we'll need in two years in mind.

Nice to have

• A scientific background (bioinformatics, data science, statistics).
• Hands‑on experience with ML frameworks such as PyTorch, TensorFlow or scikit‑learn, or with MLOps tooling for training, tracking and deploying models.
• Some exposure to LLMs and modern AI workflows, whether fine‑tuning, retrieval, or building features on top of foundation models.
• Experience with the security and compliance side of health data, from GDPR to the kind of scrutiny that comes with pharma clients.
• Experience contributing to product design, from mockups to user interviews to A/B testing.
• Experience in a startup that scaled, where you saw first hand what breaks when the team and the traffic grow.
• A hybrid profile that pairs strong front‑end craft with a good grasp of architecture and complex data management.

What we care about

Being an ArcaScientist means a few things to us. We keep the patient in mind in the work we do every day. We keep learning so the company can hold its own in a demanding market. We stay curious and open to the cultures of the people we work with around the world. We work with autonomy and rigour, and we put kindness, creativity and the good of the team ahead of individual interest.

What you get when you join

• A proper introduction to the community.
• Training in either pharmaceutical science or AI, shaped around your background.
• A spot at Future4care, a shared workspace built around healthcare innovation.
• Ownership of projects and actions within our quarterly OKRs, with direct exposure to the leadership team and our pharma clients.
• Room to grow as the company does. We're doubling the team, and the people who build the platform now will be the ones shaping it later.
• An invitation into our cultural events, cooking contests and the rest of the fun.
• A competitive remuneration and equity package.

How hiring works

We designed the process so both sides can tell whether it's a fit:

• A 45‑minute intro call with your future manager.
• An online assessment covering technical skills and working style.
• An operational interview with an ArcaScientist, often over a shared meal.
• A final in‑person interview to go through your results and meet the leadership team.

If you want to help build the future of personalised medicine and do work that reaches patients, we'd like to hear from you.