Ros Deegan: Taking Aim at the “Undruggable”

Ros Deegan’s ambitions of becoming a doctor ended abruptly on the floor of a veterinary office near her hometown of Rugby, England. As a teenager, she had decided to get some work experience in the medical field. But during her first week, while holding the paw of a black lab about to be neutered, Deegan fainted before the dog did, revealing she wasn’t cut out for the hands-on side of medicine.

Deegan didn’t give up on life sciences, however. She studied molecular biology at Cambridge and earned an MBA at France’s INSEAD. After a seven-year stint at the London-based pharmaceutical giant GSK, she found her calling in biotech. “I’ve always cared about having an impact on people’s lives,” she says. “In biotech, you get to feel close to your products and how they’re helping people.”

Ros Deegan’s secret weapon at OMass Therapeutics? The novel use of mass spectrometry

As CEO of OMass Therapeutics, Deegan is working to develop novel drugs for patients with rare or hard-to-treat diseases. Built on research originating at Oxford University, OMass uses patented mass spectrometry technology to study biological targets long considered “undruggable,” including membrane proteins and intracellular protein complexes. Its lead program focuses on rare endocrine disorders such as congenital adrenal hyperplasia (CAH). The Oxford-based company also recently formed a partnership with Genentech to develop new treatments for inflammatory bowel disease (IBD).

In this conversation, Deegan, who joined OMass Therapeutics as CEO in 2019, discusses why running a biotech company in the UK was not what she expected, how OMass’ work will have a direct impact on unmet patient needs, and why biotech needs a sisterhood.

You spent over a decade in the U.S. biotech industry, including several years in Boston, often considered the biotech capital of the world. What made you want to work for OMass, a biotech company in the UK?

Ros Deegan: I wasn’t necessarily looking to leave the U.S. My networks were there, and I loved Boston. But I had reached a point in my career where I was ready for a CEO role. When I met the team at OMass, I was incredibly impressed with both the founding scientists and the company’s then-chief scientific officer, and I fell in love with the technology. I could immediately see how useful it would have been to have at Trevena, my first biotech company, to accomplish some of the things we were trying to do there.

My husband and I were still somewhat reluctant returnees to the UK. I had grown very comfortable with the culture of big ambition, big ideas, and high-risk tolerance in the U.S., and I wasn’t sure what building a biotech company in the UK would be like.

Has the UK biotech experience surprised you?

RD: I’ve found that the UK is actually a great place for biotech. The government is incredibly supportive and sees life sciences as a high-potential sector. They offer generous R&D support, which can cover roughly one-quarter to one-third of your costs.

There are now many strong investors in Europe, and capital is flowing to where the great science is. There’s also a growing pool of very high-quality, experienced biotech talent.

The mindset has even changed since I moved back. The first person I tried to hire from GSK ended up taking another role there. I remember thinking, “What are you doing? Biotech is so much more exciting.” But at the time, people didn’t necessarily see it that way. We were offering similar compensation, yet the big-brand pharma company felt like the better opportunity. Now there’s a real excitement factor where it suddenly feels cooler to be in biotech than in pharma.

Mass spectrometry isn’t a new technology. How is OMass using it differently in drug development?

RD: Historically, mass spectrometry has been used to measure things after they’ve already been broken down. Our founder, Dame Carol Robinson, built her career on using the technology to measure changes within biological systems rather than studying components in isolation. When you do that, you get a much higher-definition readout because you can see what’s actually happening inside the system, which helps identify more precise drug candidates.

We also use mass spectrometry as a screening tool for potential compounds. By analyzing changes in mass, we can see how effective compounds are at binding to other molecules. It’s incredibly powerful because biology ultimately comes down to changes in mass – molecules becoming larger or smaller, breaking apart, or coming together.

How did OMass choose the diseases and pathways it’s targeting?

RD: We wanted strong synergy across our portfolio rather than working across many unrelated diseases. We chose to focus on rare diseases because the biology is more contained and on immunology, where we can develop a core expertise. And in both cases, we’re focused on areas where there is a significant unmet need among patients.

For example, our congenital adrenal hyperplasia (CAH) program, which is the most advanced of our solutions, has the potential to help patients who have lacked effective treatment options. In this disease, which is present from birth, patients cannot produce cortisol properly. In addition, excess male sex hormones are produced at the wrong time and in the wrong amounts.

Doctors have traditionally managed the excess hormones by giving patients higher doses of cortisol replacement to try to trigger the body’s feedback loop, which doesn’t always work and produces side effects of its own. Many patients have spent decades balancing between two difficult treatment outcomes. Our approach targets the problem more directly by blocking a specific receptor, reducing hormone overproduction without requiring high steroid doses.

The same is true for IBD. Around eight million people live with the disease, yet there have been relatively few truly innovative treatment approaches.

You’re a member of the Biotech CEO Sisterhood. What is it? And are female leaders becoming more influential in the industry?

RD: Women leaders in biotech are absolutely making their presence felt. A disproportionate share of 2025’s success stories came from companies led by female CEOs. The Biotech Sisterhood is an amazing group. It’s a network of successful, motivated women united by a shared commitment to lift one another up and open doors for the next generation. At a recent event in San Francisco, what stood out to me was how many men showed up. Expanding representation and attracting top female talent across biotech isn’t just a women’s issue. It matters for the strength and competitiveness of the entire sector.

What does success look like for OMass in five to ten years?

RD: Our ambition is to become a fully integrated biotech company that can market its own products while continuing to discover new medicines for immunological diseases with high unmet need.

That feels achievable because clinical trials for rare disease medicines typically involve hundreds of patients rather than thousands, and because we can begin to de-risk drug targets with Phase 1 data in healthy volunteers. The UK hasn’t yet produced a company like Genentech or Biogen. We want to become Britain’s leading biotech company.

That doesn’t mean doing everything alone. We’ll continue to partner where it makes sense, such as our collaboration and license agreement with Genentech for IBD. It’s a complex disease and we are working on new biology, so generating strong clinical data is essential to help de-risk the drug.

Ross Deegan is the CEO of OMass Therapeutics, an Oxford-based biotechnology company that develops novel treatments for rare diseases and immunological conditions. GV co-led OMass’ Series B financing in 2022. GV Executive Venture Partner Scott Biller is on the company’s board, and General Partner, Vidu Shanmugarajah is a board observer. Ros has more than 20 years' experience in the biotechnology and pharmaceutical industries, both in the UK and the US. Prior to OMass, she helped establish the US subsidiary of Bicycle Therapeutics and led business development and operations at Trevena.