From PhD to Biologics Innovator: How Curiosity, Problem-Solving, and Risk-Taking Shape a Career in Biopharma
John Zehmer has spent nearly two decades navigating the evolving world of biologics and immunotherapies. As Associate Director of Purification Sciences at MacroGenics, he oversees critical processes that ensure therapies are safe, effective, and ready for clinical trials.
From his early fascination with biology to leading teams and tackling complex antibody-drug conjugates, John’s journey highlights how curiosity, adaptability, and hands-on problem-solving can drive both personal growth and meaningful impact in the life sciences.
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Q: Can you share your background and what brought you to MacroGenics?
I earned my PhD at Arizona State University and completed a postdoc at the University of Texas Southwestern Medical Center in Dallas. I began my career in process development at a small company, then led the virus clearance department at a contract research organization for several years.
I joined MacroGenics about eight years ago, initially drawn by the chance to learn something new. My current boss, who had been one of my clients, told me about the opportunity to join a well-resourced, innovative company where I could grow with the organization.
Over time, I’ve had the chance to contribute to programs moving late-stage through BLA submissions and, more recently, dive into the exciting field of antibody-drug conjugates (ADCs).
Q: What does your role as Associate Director of Purification Sciences entail day-to-day?
We’re a small, flexible team, so there’s not a strict division of labor—we all wear multiple hats.
I work across process development, purification, and problem-solving to ensure therapies are manufactured reliably. Every day is a mix of analyzing complex data, optimizing purification processes, and coordinating with internal teams to move programs forward. As MacroGenics has expanded into ADCs, my role has evolved to include understanding the interplay of antibodies, toxins, and linkers, ensuring these therapies can reach patients safely and effectively. It’s a combination of scientific rigor, engineering, and practical problem-solving.
Q: What excites you most about the direction of the biopharma field, particularly in biologics and immunotherapies?
ADCs have tremendous promise, though their full potential is still emerging. The challenge lies in balancing the right target, payload, and linker—each variable is complex, and together they require precise coordination.
Beyond ADCs, I’m fascinated by our expanding understanding of the immune system and its application in cancer therapies. There are still mysteries to solve—like why immunotherapies work spectacularly for some patients and not at all for others. I think the next decade will bring big discoveries that can meaningfully change patient outcomes, and being part of that progress is incredibly rewarding.
Q: How has your prior experience leading scientific teams and client-facing roles shaped your approach today?
Earlier in my career, I managed large, specialized teams and worked closely with clients at a contract research organization. That experience taught me the importance of communication, flexibility, and understanding different perspectives.
While MacroGenics is different and I’m still reorienting to some aspects of client-facing work as we expand CDMO operations, those lessons in collaboration and mentorship remain critical. I’ve learned to balance technical expertise with practical guidance, helping colleagues navigate challenges while fostering a culture of curiosity and continuous learning.
Q: What initially drew you to science, and how has that passion influenced your career?
I’ve always been curious about science. Biology made sense to me early on, and I was naturally drawn to analyzing complex problems. I loved discovery but realized I preferred applying biology through problem-solving rather than pursuing endless experiments.
My approach now is more like engineering—combining biology, math, and statistics to design robust manufacturing processes. That mindset has guided my entire career, allowing me to tackle complex challenges while contributing to therapies that improve patients’ lives.
Q: What advice would you give to early-career scientists looking to build a long, impactful career in biopharma?
Be curious. It’s easy to focus solely on your immediate tasks when you’re first starting, but understanding what other teams do, why they ask the questions they ask, and how their work connects to the bigger picture is invaluable.
Take chances—even when outcomes are uncertain. I’ve seen how unexpected opportunities, like being recruited into a role I wasn’t fully qualified for, can transform a career.
Dive in, learn, ask questions, and don’t be afraid to step outside your comfort zone. Those experiences shape not just technical skill, but professional resilience and long-term growth.
Q: Outside of work, how do you recharge?
I love the outdoors—sailing, hiking, backpacking, and exploring wilderness areas whenever I can. My wife and I recently completed a six-day wilderness trip on the Middle Fork of the Salmon River in Idaho, which was a remarkable experience. Adventures like that help me stay balanced, and I try to incorporate a bit of science into every trip—studying ecosystems, geology, and the biology of the places I visit.
Staying curious in both work and life is what keeps me engaged and energized.
