Alumni spotlight: Greg Chen (PhD '07)

May 18, 2021 by Sarah MacFarlane

Chemistry alumnus Greg Chen knows a thing or two about working under pressure. He has spent much of the past year helping to develop a COVID-19 vaccine — on top of a dozen other projects on his to-do list.

“The COVID-19 vaccine was just one program our team was handling, and my goal for the year included 13 programs,” says Chen, who studied chemistry at U of T, earning his master’s in 2001 and his PhD in 2007.

“The most important thing is the quality of the work. You really don’t want to make any mistakes. That’s the major pressure. You want to make sure everything is right.”

As a senior scientist at Janssen, the pharmaceutical arm of multinational corporation Johnson & Johnson, Chen was part of an essential team responsible for generating reliable methods to measure biomarkers for clinical trials. In other words, they developed methods of assessing how patients were responding to treatments across several therapeutic areas, including neuroscience, oncology and immunology.

“I needed to show up every day,” he says. “It was a very busy year.”

As part of his broader range of work at Janssen, Chen researched neuroscience biomarkers by identifying novel positron emission tomography (PET) imaging agents to provide information about the state of a disease or a patient’s response to a specific treatment.

“A problem in neuroscience — particularly in clinical studies — is that we don't know how much of a drug we should give the patient,” he explains. “To treat depression or other mood disorders, for example, we don't know how a novel drug candidate should be dosed. In oncology, you can take out the tumour, but in neuroscience, it is much more difficult to take a brain biopsy.”

To overcome this challenge, radiologists use PET imaging biomarkers. PET is a form of nuclear medicine imaging that evaluates tissue and organ function by measuring chemical processes taking place in the body, such as metabolism. During the procedure, a miniscule amount of a radioactive medication — called a radiotracer — is injected into the body and detected by the imaging.

“It will very precisely locate where the drug is delivered, and when co-dosed with the therapeutic medicine, it gives information about how much of the drug went to the target,” Chen says. “So, in a clinical trial, you can predict how much compound is needed to show efficacy without hurting patients.”

In addition to evaluating the body’s response to treatment, this technology can detect biochemical changes which could indicate early stages of certain diseases. For example, with the help of a radiotracer called FDG, cancer cells appear as bright spots on PET scans because they have an increased metabolic rate compared to non-cancerous cells.

“It's a very interesting and highly cross-disciplinary science,” he says. “In order to discover a novel PET radiotracer, you need to understand not only medicinal chemistry, but also radiochemistry, biology, computer modeling — how to formulate the drug, the imaging process, the algorithm behind it. It’s like putting LEGO pieces together. I’m really fascinated by learning new things, and that's something I definitely got out of the training in the PhD program at U of T.”

Last month, Chen’s passion for learning led him on a new adventure. He left his busy but familiar surroundings at Janssen to become associate director at RayzeBio, a biotech company which launched last year. The company is focused on targeted alpha-particle therapy — the process of attaching a small amount of a radioactive substance to antibodies or peptides which will bind to cancerous cells, allowing for targeted destruction of tumors.

“It’s a brand new area, and I thought, ‘Why don't I try to push my career and see where I can go?’” he says. “At Janssen, my life was very stable, but there are a lot of things I can learn from this start-up — how to attract funding, initiate research. I think there are a lot of things to be learned outside of science.”

Though he has spent most of his career living and working in California, Chen hopes to someday retire in Toronto, where he spent nearly a decade as a U of T student.

“I left China in 1998 and started graduate school in the United States,” he says. “The same year, my girlfriend’s application for immigration to Canada got approved, and she landed in Toronto. I started thinking, ‘The best school in Canada is the University of Toronto. If I’m lucky, I can get in.’”

Financial aid was also an important factor in Chen’s decision to apply to U of T and had a lasting impact after he’d enrolled.

“In 1999 and 2000, my wife was working in the tech industry, and there was a big crash with the dotcom bubble,” he says. “She tried to find a job, but it was really hard at that time. Financial aid for graduate school was extremely helpful, not only for my studies but also for my family. We really appreciated it.”

For current U of T students, he recommends a formula of equal parts practicality and curiosity.

“Be practical and honest with yourself in your research. And keep curious all the time; don’t limit yourself to what you learn at school. Keep your mind open, always ready to learn new things.”