Physician Builder Spotlight: Louie Cai

We’re shining light on MD-entrepreneurs! Each week, we feature an entrepreneurial doctor who’s building a cool product, company, or working on a big idea that you definitely want to know about. This week, meet Louie Cai, Co Founder of Cosign AI, a start-up that is helping clinical trial sponsors and sites accelerate recruitment and close trials faster. You can connect further with Louie on LinkedIn.

1. Louie, what inspired you to become a physician entrepreneur? I’ve always had this underlying drive to make things better. During training and in clinical practice, I constantly noticed workflows and processes that were inefficient or just didn’t feel good for patients or clinicians. I could see what a better version could look like, and I kept thinking, “It doesn’t have to be this way.”A lot of healthcare innovation comes from people who have never actually practiced medicine. They’re smart, but they often miss the emotional and practical realities of what it feels like to care for patients day after day. I came to realize that the people who live the problems are the ones best positioned to solve them. If I wanted a tool that truly supported me and my colleagues — something empathetic, efficient, and clinically grounded — I had to be part of building it. If not me, then who?

2. Tell us what your company does and what problem you’re trying to solve. Our company is built around a simple mission: make healthcare cheaper, better, and easier to access. That mission came from a pretty honest observation — healthcare today is expensive, frustrating, and often hard to navigate for both patients and clinicians. We’ve experimented with different products in clinics, but our current focus — and where we’re seeing the strongest impact — is in clinical trial screening and recruitment. We take all the data that already exists in a patient’s chart and use AI to accurately match them to eligible clinical trials. Clinical trials have very clear inclusion and exclusion criteria, which makes this a great environment to build reliable medical decision support.

This is our entry point into a much bigger roadmap. Over time, we want to build toward a physician copilot that enhances medical decision-making across the board. But today, we’re focused on solving clinical trial recruitment because it’s a meaningful problem, drives real value for practices and patients, and is a place where AI can genuinely make things better right now.

3. What’s your advice to anyone who’s thinking about entrepreneurship or a nontraditional career in medicine? You can’t do this for the money. Building something new in healthcare is incredibly hard. There are moments of real excitement when clinicians love what you’ve built — and then moments when investors tell you the idea is “too small” or “not disruptive enough.” The reality is that most meaningful healthcare innovation looks boring from the outside. Our daily work is mostly documentation, coordination, and administrative burden — so the tools that actually make a difference often don’t look flashy. They just quietly make clinical life better.So my advice is: Don’t let the lack of hype discourage you. Don’t rely solely on investor interest as your validation. Instead, talk to other physicians. Talk to practices. Ask whether the problem you’re solving exists beyond your own personal workflow. Be genuinely curious about how others work — because the biggest trap is assuming your experience is universal.

You will get rejected. A lot. By accelerators, by investors, by advisors. That’s normal. Use each rejection to refine, question, and re-evaluate. And if, after all that, you still deeply believe the problem matters — then keep going. The conviction to continue is the most important part.

4. How can a physician get over the “start” problem and overcome their biggest fear to start a company? The biggest thing is to just start talking to people. Conversations are massively undervalued. If you have an idea, use it as a reason to interview others:“I’m exploring a problem and would love your perspective — could we talk for a few minutes?” That’s your first step — not incorporating, building a prototype, or writing a business plan. It’s simply understanding whether the problem you care about exists beyond your own experience.You’ll find that almost every problem in healthcare is shared somewhere — and often there are already companies working on adjacent issues. That’s a good thing. It means the space is real. So do the research. Ask people about their workflows. Let curiosity drive the process before you commit serious time or money. Once you’re convinced the problem actually matters to others, that’s when you start building traction. Incorporation is just a logistics step — necessary only once you’re taking investment. Tools like Clerky make that part straightforward. And honestly, you can use ChatGPT to help outline your incorporation checklist and legal tasks — it’s great for that.But the most important piece: Find a co-founder. Building in healthcare is emotionally hard, slow, and often discouraging. You need someone to share the emotional weight with. There were many times I wanted to walk away — and my co-founder didn’t. And later, the roles reversed. Having someone to pull you forward when you’re doubting yourself is everything.

So in short:

1. Talk to people and validate the problem first.
2. Don’t rush to incorporate; that’s just execution.
3. Find a co-founder to share the journey — and the setbacks.

5. What’s the #1 lesson you’ve learned since building your company that wasn’t obvious to you before? The biggest lesson I’ve learned is that everything takes longer and is more complicated than you expect. An idea might seem simple in your head — “we’ll talk to a few people, run a pilot, and launch quickly” — but execution is almost always harder. Things that feel like they should be fast often end up taking ten times longer and being ten times more complicated.

The key is to keep moving forward, even if it’s just small steps. You might not scale from 1 to 100 in a month, but going from 1 to 2, or 2 to 5, still counts. Healthcare innovation is slow, and headlines of companies raising millions in a few months often hide years of behind-the-scenes work. Don’t get discouraged if you haven’t raised enough money or gained huge traction yet. Steady progress is what counts.

6. What are your top resources that helped on your entrepreneurial journey? There are three resources that have been incredibly helpful:

1. Alchemist Accelerator – I never went to business school, so a lot of the basics of building a company were new to me. Being part of a formal accelerator gave me a structured curriculum and a roadmap for the steps I needed to take. It also connected me to a network of founders and advisors outside of medicine, which helped me realize that the problems we face in healthcare are not unique — they’re challenges every startup encounters.

2. YouTube – There’s an enormous library of videos where founders share their experiences at every stage of building a company. I’ve learned a lot from YC talks and founder interviews. Not every lesson applies directly to healthcare, but listening to how other founders approached go-to-market strategies, product development, and fundraising has been invaluable.

3. ChatGPT – This has been a game-changer. It’s an amazing way to get a foothold in areas you’re unfamiliar with, whether that’s marketing, sales strategy, product design, or legal questions. ChatGPT allows you to quickly understand the basics so you can have informed conversations and make decisions with confidence. It dramatically lowers the barrier to doing something completely new.

7. How can other physicians support you? Right now, our focus is clinical trial recruitment, and this year we’re looking to work with sites that run a high volume of trials to help improve their workflows. Our product is currently free for sites to use, and we’d love to collaborate with anyone interested in accelerating clinical trial recruitment, particularly in ophthalmology, pain medicine, rheumatology, and dermatology. We’re also open to conversations with potential investors who are interested in the clinical trial space and exploring opportunities for collaboration. If you’d like to connect, the best way to reach us is via email at louie@co-sign.ai or through our website/contact form.

AI Bonus Questions

Just for Offcall members: We're making available Louie’s answers to 3 questions about AI:

1) What's an actual prompt you're feeding to GPT that's been helpful to your clinical work?

2) What's the AI tool/use case you can't live without?

3) What are your top AI resources to get going as a physician?

See his responses below after creating an Offcall account.