S4, E8: Infinimmune – From a Scientific Hunch to an $838M Merck Partnership, with CEO and co-founder Wyatt McDonnell

[00:00:03] Welcome to the Raising Biotech podcast, where we explore the stories, science and strategy behind companies raising impressive funds to develop ambitious medical breakthroughs. I'm your host, Sarani Fernando.

[00:00:19] When five former 10x genomic scientists came together in 2022 to start what would become Infinimmune, they didn't have a polished business plan. They didn't even have an idea of what the company was going to be. What they did have were some scientific observations that they just couldn't ignore. Cutting edge work in single cell sequencing had left them wondering whether there might be an entirely different way to discover antibody drugs.

[00:00:49] Four years later, Infinimmune has raised close to $90 million in venture financing, built its own pipeline of antibody drugs, and earlier this year signed a multi-target discovery partnership with big pharma Merck, worth up to $838 million. Its most recent raise came just last month, a $75 million Series A to help take its first two dermatology programs into the clinic.

[00:01:16] It's a lot of progress in a very short period of time. But what interested me most was how they got there, because the path to what Infinimmune is today was anything but conventional. Joining me on the podcast to tell that story is Infinimmune co-founder and CEO, Wyatt McDonald.

[00:01:35] We talk about his own journey into industry, the scientific question he couldn't quite let go of, and how that ultimately led to Infinimmune and the company's rapid journey from seed financing to a landmark Merck partnership just four years after launch. I hope you enjoy the episode. Hi, Wyatt. Thanks for joining the podcast. Great to join me this morning. Thanks so much for having us.

[00:02:02] All right. So just to start us off, do you want to just give us the elevator pitch of Infinimmune, a little bit about the core of what you guys are trying to do and what separates it from other antibody developers?

[00:02:13] Yeah, happy to talk about that. So most antibody discovery typically starts with a murin or a transgenic or another synthetic library. And then you start with antibodies out of that library and engineer those antibodies towards something that is human compatible or compatible with your target product profile.

[00:02:35] So we do the opposite. So Infinimmune reads the human immune system and antibodies in human immune systems directly end to end. So we sequence several thousand base pairs versus several hundred. We are able to access all of this really interesting antibody biology as a result. And we screen millions of single memory B cells across hundreds of different donors. At its core, Infinimmune is trying to rethink how antibody drugs are discovered.

[00:03:03] Rather than starting with mice or synthetic antibody libraries, the company starts with something else entirely, the human immune system. The thinking is surprisingly simple. Every day, our immune system produces antibodies that have already been tested and refined by evolution. So instead of engineering antibodies from scratch, Infinimmune begins with antibodies that already exist in people.

[00:03:30] Once they've identified promising antibody candidates, the company then uses its AI model called Glimpse to optimize them for drug development. This optimization includes improving characteristics like potency, manufacturability, developability while preserving their human origins. So the short version of that is human first antibody biology at scale with AI on top.

[00:04:00] It's an ambitious vision. But in 2022, this wasn't a company. It was an idea shared by a handful of scientists who believed they had spotted something everyone else had missed. Not necessarily that everyone else was wrong, more that new technology allowed them to see biology that hadn't previously been accessible. So let's rewind a bit back to where it all began, specifically Wyatt's journey.

[00:04:28] Like many biotech founders, Wyatt's story began in academia. I was a pretty distracted kid, fresh out of a liberal arts college. I studied biology, microbiology and immunology specifically, and chemistry and Spanish and piano performance. You know, highlight that as a way of saying, if you can find different ways of looking at the world, you meet other people that can see things differently than you do. And that's sort of a through line that's central to how we build teams at the company today.

[00:04:58] In 2015, Wyatt graduated with a molecular biology degree from Hillsdale College. And over the next four years, he went on to complete both a master's and a PhD in microbiology and immunology at Vanderbilt University. In 2019, he went on to work as faculty and Wyatt reflected on this time as being quite serendipitous for his career trajectory. During his PhD, single cell sequencing was beginning to transform biology.

[00:05:28] For the first time, scientists could study individual cells at scale that simply hadn't been possible before. So part of what that looked like for me was this really, really interesting, you know, candidly speaking, lucky time to go to graduate school where single cell sequencing really took off and became accessible at a totally new scale than when I had started even just a year or two beforehand.

[00:05:56] As it happened, Vanderbilt was one of the first universities to gain access to these new single cell sequencing platforms, allowing researchers to compare different technologies side by side. For Wyatt, it opened up an entirely new way of thinking about biology, not by looking at millions of cells together, but by studying them one cell at a time. That shift would ultimately change the course of Wyatt's career.

[00:06:22] As Wyatt's research progressed, he found himself working closely with a hot new biotech company at the forefront of the single cell sequencing revolution. That company, 10x Genomics, was developing technologies that were transforming how researchers studied biology. Wyatt's work involved evaluating some of the company's earliest single cell sequencing technologies and co-authoring papers using the platform.

[00:06:50] I joined the faculty very, very briefly. I think I made it a whole month before taking an offer from 10x that ended up changing my life. I moved to California. Talking about serendipity, joining 10x Genomics couldn't have come at a better time for Wyatt. In September 2019, the company went public with a debut valuation of nearly $5 billion. They went into IPO lockup, I think, eight weeks after I started.

[00:07:18] So, you know, I recommend getting lucky at least once in your lifetime. I certainly did. Meanwhile, single cell sequencing was pretty much transforming biology. And Wyatt suddenly found himself surrounded by scientists, engineers and computational biologists who were all pushing the technology into new and exciting directions. Yeah, you know, I spent three years cutting my teeth with some of the brightest interdisciplinary scientists I have ever met.

[00:07:47] And that was, you know, really great because, you know, if you learn how to write a little bit of R or Python code, you suddenly meet software engineers from Google and go like, wow, I don't really know anything about any of this. I don't know really anything about algorithm development, but I do know how to sit in the gap and bridge a couple of those different worlds, whether it's molecular biology plus computational analysis.

[00:08:11] So Tenex, when I joined, was this unbelievably well-connected talent hub with chemists, with microfluidics developers, with physicists, with computational biology proper, not just on a weekend or what Claude could teach you in an afternoon in 2026. And connected to a really strong focus on product innovation.

[00:08:34] So it was a really great journey through academic roots, product development, product landscape analysis into, wow, there's this untapped opportunity to take this gold standard technology and discover therapeutics. Actual drug discovery is possible with this technology. The next three years would prove to be an intense but formative period for Wyatt.

[00:08:58] And during those years, a very different question began to emerge, one that would eventually lead Wyatt and several other colleagues to start Infinimune. I was a very excitable recent academic and said, you know, we should point this technology at antibody discovery. An interesting idea, but hard in theory to execute in any material way. And then the pandemic hit.

[00:09:25] And all of a sudden, everybody on the planet knew what an antibody was. And there was a pretty obvious reason to develop an antibody solution. The COVID-19 pandemic unexpectedly gave Wyatt and his colleagues the opportunity to put their idea into practice. Working with some of the earliest patient samples, the team used single cell sequencing to recover thousands of potent human antibodies in a matter of days.

[00:09:53] So that turned into barcode enabled antigen mapping, which I worked on at 10X with initially a really, really small focused team. And that was a big take home for Wyatt, a small team that moved remarkably quickly. Within a matter of months, they had built a prototype and were able to test it using samples from some of the earliest COVID patients in the States. In just a week, they recovered thousands of broadly neutralizing antibodies directly from humans.

[00:10:23] And for Wyatt, it was a powerful demonstration of what suddenly became possible when you could study antibodies, their genetic sequences and what they bind to all at much greater scale. But there was another lesson in it too. This didn't require a huge research organization. A small, highly technical team, given the right tools and a very specific problem to solve, had been able to move extraordinarily quickly.

[00:10:50] That left Wyatt thinking about the much bigger data set that could be created by applying this approach beyond COVID and what else might be hiding in the human immune system. And after you've seen what high speed, high throughput, high quality antibody discovery looks like, well, if that's true for viruses, maybe everything I learned in grad school was wrong. And if that's true, what would that look like?

[00:11:16] That moment became impossible to ignore and leaving 10X in 2022 wasn't one decision for Wyatt. It was several. He explained that the technology he'd helped build wasn't being adopted in the way he'd hoped. And after taking some time away from work for family reasons, one thought kept returning. Things that I can't stop thinking about, like, you know, we, you know, David and I were right.

[00:11:41] This finding that we discovered is now a seminal paper in antibody biology worthy of publication in Nature. So we're right about that. Like, I can't really let go of this, like, thought in the back of my head going, probably there's more to be found there. It can't just be a function of antiviral biology and how antibodies target viruses. I simply can't believe that what I was taught about autoimmunity in grad school about, you know, antibody selection is correct.

[00:12:10] There's just no way it's true. And if that's right, then there's a company to be built around that. Right after I left 10X, you know, we had started fishing through the sequence read archive and finding all of these really unusual antibodies that were mostly viewed as junk reads by folks who could look at them with traditional RNA-seq alignment workflows.

[00:12:37] We found all of these antibodies that are not in anything I read or taught in grad school. So antibodies that seem to exist in humans consistently and break the rules of antibody structural biology. So that was what we decided to build Infinimune around. And that was the remarkable, almost simple founding thesis.

[00:12:59] Rather than trying to improve existing antibody discovery methods, the team believed they had uncovered biology that had largely been overlooked. If these unusual antibodies really did exist consistently across humans, they weren't just interesting scientific observations. They could represent an entirely new starting point for discovering medicines. But believing you have a company is one thing. Actually building one is another.

[00:13:28] Over the following weeks, Wyatt began bringing together a group of colleagues he'd worked closely with at 10X Genomics. Between them, they brought expertise spanning computational biology, genomics, software engineering and antibody development. More importantly, they shared the same conviction that the biology they'd uncovered deserved to be explored further. I think for us it was more, it feels like there's all of this biology.

[00:13:56] Let's rent a shoebox office in San Ramon and spend a couple of weeks figuring out what we do and don't believe are sensible opportunities, how long it's going to take to build some of these technologies that don't exist. Rather than just rushing to build the first company they could think of, the founding team deliberately stepped back and challenged their own assumptions.

[00:14:17] They explored different ideas, questioned whether there was really a business behind the science and tried to separate what was genuinely novel from what was simply exciting. Only once they were convinced they had found a problem worth solving, did they begin thinking about how to build a company around it. I think initially we'd sat down as a team of founders and thought, well, maybe we should do an SBIR grant.

[00:14:43] And then I said, no, we should go raise a big seed round right now. And my co-founders just sort of chuckled and said, yeah, pat me on the head like, okay, Wyatt. And I'm like, yeah, let's go raise a seed round. And then it happened. And so I actually would say I didn't initially set out to be a CEO, but I did set out to work on a problem that I believed in very, very deeply.

[00:15:09] Like it was the most compelling problem I have encountered in my career as a scientist. And that's a very excellent motivator as well. What really struck me about this story was just how unconventional it was. This wasn't a group of founders who left their jobs with a polished business plan and a pitch deck already in hand. They came together because they shared a conviction about the science.

[00:15:35] And only then did they spend weeks figuring out whether there was actually a company to build. What's even more crazy is how quickly it all happened. Within just a few months, the founding team had settled on a company thesis and decided it was time to raise capital. I think an exercise that all founders should do very early on, which is there's a slew of companies that have been funded in the past several years. Trace those back.

[00:16:04] You know, maybe they're at a, you know, series A or a B or a C now, but go back to the seed round and who were the first checks in the door? So then I spent, you know, that July just pitching some of those folks, including Josh Elkington at Axial VC, who ended up being our sort of initial center of capital gravity, introduced us to a couple of funds. You know, I was supposed to get a half hour walk and talk with him.

[00:16:31] And that turned into a three and a half hour walk throughout most of Berkeley's campus and most of the surrounding neighborhoods. And then sort of a similar chemistry fit to Playground Global, where Ben Kim and Jory Bell ultimately ended up leading our seed round. I think just three months after we had started the company.

[00:16:51] Infinimune closed its $12 million seed round in October 2022, going from a non-existent company with some napkin ideas to a successfully funded startup by Silicon Valley heavyweights in just three months. Now, if you're a regular listener of Raising Biotech, you'll know that I'm always very curious around founders' experiences knocking on investors' doors.

[00:17:15] And not only was I keen to know Wyatt's general experience being quite fresh in the industry, I was also curious to know how investors received the five co-founders setup. It's interesting because I feel like if you are serious about raising capital, that just sort of is evident to investors.

[00:17:36] Like investors are pretty good and generally have had enough of their time wasted by folks like, oh, you know, I'm exploring a fundraise. You know, especially at that early stage of a company, right? Where if you do what we did, you know, we came out of the gate strong and said, we are raising a seed round. We have started a company around this.

[00:17:59] We have a clean cap table on the Delaware C Corp and a world-class set of technologists, all of whom left their full-time jobs to work full-time on this. Like it's, it's very, it's a strong signal. And I do think some of our, our earliest meetings, you know, we had funds that would ask, you know, all five of us to get on zoom. You know, I think in part because it's like, are these, like, are these people really all working together?

[00:18:26] Like, are we, are we sure that there's five people who left 10 X to go work on this one thing? And that seems like a, a pretty strong sub position. Maybe why it's just going to like try to recruit some people after closing the round. And I was like, no, like, no, this is a management team that's working really well together. They're highly technical. They also can zoom out and look at a bigger picture. They're comfortable doing that. They'll take feedback. They'll defend a position. Those are the things that I think a good investor looks for.

[00:18:56] And I think once you have also talked to enough funds, it's like, yeah, and we're talking to folks over here and here and here. Like if you're able to talk about what the potential syndicate looks like with active conversations, that's the other signal that investors need because nobody likes feeling alone. And like they're the first, you know, capital at risk into the round, right? People are thinking about risk-free returns, not return-free risk.

[00:19:26] And if you're the first money in the door, it can be hard to overcome that fear of return-free risk. And as it happens, according to Wyatt, the five co-founders seem to have worked without any major drama. I think the biggest thing you have to get over initially is like there have to be like technical areas of expertise, right? Where it's like people need to have lanes that they can work in.

[00:19:52] It's one thing to ask a computational biology person to explain their work and explain their thinking. And it's a very different thing to say like, I don't think you're doing this right without being able to justify that position. So I do feel like our founding team, you know, we're partially a product of the cultural selection that 10X was very, very good and still good at running.

[00:20:18] Which is you have to hire these smart persnickety PhD holders. But also you have to screen for are they going to work well with other people? And are they going to put in the effort to articulate their thinking? Are they going to be able to change directions very quickly and very aggressively given new data? So I feel like a lot of that was selected out before we started Infinimin.

[00:20:47] Like we're all survivorship bias products of 10X, which excelled at hiring collaborative, bright, interdisciplinary scientists. So armed with a collaborative team and their fresh $12 million, things went a lot smoother than planned. You know, the funny thing is we didn't budget for success, which is an interesting problem to have.

[00:21:12] I mean, I think when we did our initial modeling and said, well, we think it's going to take us a solid year to build the initial sequencing and the end technology platform. Then we think it's going to take another year to build the antigen specificity platform. So the complete human tech and the anthrobotic tech that are part of our platform. We were wrong by a lot.

[00:21:34] Instead of two years, Wyatt said the team hit those first two major milestones within months, the first in three months and the second within four. It meant Infinimune suddenly found itself much further ahead than expected. The question was no longer simply whether they could build the platform. It was whether that platform could actually produce antibodies capable of becoming drugs. So over the next couple of years, the team began building the evidence.

[00:22:03] They screened antibodies across hundreds of targets. They generated data to show that those antibodies were functional and started turning some of the most promising candidates into Infinimune's first internal drug programs. And at the same time, they began talking to potential pharmaceutical partners. This is where I think the story becomes particularly interesting because for a company as young as Infinimune, getting the attention of Big Pharma is one thing.

[00:22:31] But convincing them to trust you with targets from their own pipeline is something else entirely. Having those partnership conversations with companies like Merck to build that sort of reputation, which is half of why you get a partnership in the first place. A partner has to understand if they look at a company like Infinimune. Infinimune's met with us for the first time. Here's what they said. They told us they have a platform that does this.

[00:22:58] They told us these data that they're working on will be available in three months' time. Let's check in with them in three months' time and see if that's true. So once you have a couple of those meetings in a row, then it's like, okay, this is a team that is doing science we believe in, that does what they say they're going to do. Now, do they have other asset data to show that their platform can do something really exceptional and unique? The team first met Merck in December 2024.

[00:23:26] They had some swift conference meetings at both JPMorgan in San Francisco and Bio in San Diego in 2025, and they had a few Zoom calls in between. Infinimune was generating stability data, functional data, animal data, and eventually the manufacturing data needed as its lead programs moved towards the clinic. In other words, Merck wasn't simply evaluating the promise of Infinimune's platform.

[00:23:52] It was watching whether this very young company could actually execute. And then that turned into, okay, Infinimune is actually making progress on its target product profiles, on its development candidates for its front-running programs. The stability data look excellent. The functional data look excellent. The in vivo data look excellent. Now the CMC data as they're getting up and ready for IND enabling studies look really good.

[00:24:21] So it's a long-running diligence and conversation that is, at least for antibody companies, anchored around, are you capable of building a quality asset? Because if you aren't capable of building a quality asset, why on earth would we give you high-priority targets from our therapeutic pipeline as a global pharma? We need to know you're going to execute very successfully with conviction and quite aggressively. Ultimately, Infinimune passed that test.

[00:24:51] In March 2026, the company announced a multi-target collaboration with Merck, giving the pharma giant exclusive rights to develop and commercialize antibodies discovered through Infinimune's platform against a number of undisclosed targets. The upfront payment wasn't disclosed, but across the collaboration, Infinimune could receive up to $838 million in milestone payments.

[00:25:18] For a company that had started less than four years earlier with five founders trying to work out whether they even had a viable business, it was a pretty extraordinary validation.

[00:25:30] In hindsight, if I had approached our co-founders and said, you know, four years later, we are going to be sub a year to the clinic with two drugs and we'll be on the heels of a really massive partnership and we'll be well on the fundraising front. I think rightfully my co-founders would have looked at me and said, like, that's a great vision for somebody else to work on. Have fun, bud.

[00:25:56] And since Wyatt and I spoke, which was back in June, Infinimune has yet again added another major financing milestone. In August, the company announced a $75 million Series A co-led by existing investor Playground Global and Regeneron Ventures with RA Capital and several other investors joining the round. Merck's venture arm also participated.

[00:26:22] Much of that financing will go towards advancing Infinimune's own pipeline, including two antibody programs for atopic dermatitis or eczema, which the company plans to take into clinical trials in 2027. And despite Infinimune still being relatively early in its journey, Wyatt said the team is already thinking about what a viable exit could eventually look like. I think never too early to think about how you return capital to investors.

[00:26:51] That is ultimately the job of all small biotechs is to return capital to investors. So for us, there's a couple of ways that that can be realized. You know, one are one approach is the sort of put assets in subsidiaries model. Another approach is an outright M&A. Another approach is an IPO or reverse merger.

[00:27:12] So when you're doing partnerships like this, the core in our boardroom discussions is always how does this partnership move us towards exit flexibility and likelihood of exit? And then in terms of milestones that we're working on on our end, you will be first in human with our first two programs next year in 2027. And we are developing our own therapeutic pipeline outside of the SMERC partnerships.

[00:27:41] We likely have bandwidth or room for, call it two to three more partnerships. We can't prosecute hundreds of targets on our platform. We want to help pharma companies work on new target biology for new medicines. And most of the value from platform companies like Infinimune ultimately comes from the assets.

[00:28:02] And we're focused quite attentively on making sure those assets are pushed forward on a tight, high quality timeline with really compelling human clinical evidence behind them. What I found the most interesting about Infinimune story is just how quickly all of this has happened. There are still, of course, much bigger tests ahead in biotech. Raising money and signing partnerships can only take you so far.

[00:28:31] Ultimately, Infinimune will have to show that its platform can produce medicines that can make a difference for patients. But I think there's also something interesting here about how biotech companies are being built today. You don't necessarily need decades of industry experience, a huge team or even a perfectly formed idea on day one. Sometimes what matters is finding the right people, identifying something in the science that others haven't seen.

[00:28:59] And that's probably the real lesson for Infinimune story. But as we know in biotech, we'll have to wait and see. Thanks to Wyatt for joining the episode and sharing Infinimune story. And thanks to all of you for tuning in. Please remember to subscribe if you haven't already to make sure you don't miss future episodes. For now, I'm Sarani Fernando. I'll catch you next time on Raising Biotech.