Yvonne Greenstreet has seized opportunities to try new things in her career, even when those around her weren't as enthusiastic about them. And her willingness to leave her comfort zone has led to a rich career that has touched on important new drugs for patients from GlaxoSmithKline ($GSK) and now Pfizer, where she's been a senior executive since early 2011.

At GSK, where she spent the first 18 years of her career in the industry, she worked on important new drugs such as the company's Zofran, for preventing chemo-associated nausea and vomiting, as well as Valtrex for combating outbreaks of genital herpes. She eventually rose to senior vice president and chief of strategy at GSK, reporting to the drug giant's R&D chairman, Moncef Slaoui, and she engineered the company's in-licensing deal with Human Genome Sciences that brought it rights to the lupus therapy Benlysta (now wholly owned by GSK after its buyout of HGS this year).

None of this would have happened if Greenstreet had placed pleasing others above her desire to leave the practice of medicine to pursue an MBA, which she earned from the prestigious INSEAD Fontainebleau in France.

"When I decided to leave medicine and do an MBA I think a lot of people, my family particularly, were surprised by this and were not hugely enthusiastic, to be honest," Greenstreet says. "But it's what I wanted to do, so I did it. I think it was a really important experience for me that has been quite formative for me in my career. As I said, take on different opportunities. Have courage to follow what you believe is important."

At Pfizer, she's among the senior R&D leaders at the company working on bringing a bevy of new treatments to patients through its specialty care unit. The unit is responsible for the blockbuster hopeful tofacitinib, which the FDA stamped with an approval this week for treating rheumatoid arthritis. The group also has a pipeline of other drugs against rare diseases, cancer, autoimmune conditions and infectious diseases.

Later this year, her group expects to begin a Phase III program for its meningitis B vaccine and has responsibility for the big-selling pneumococcal vaccine Prevnar 13. She's also excited about the human health and market opportunities of a candidate from Pfizer partner GlycoMimetics for patients with sickle cell disease, which is prevalent in people of African descent. Her own experiences in West Africa have influenced her desire to treat illnesses.

"I spent my early childhood in Ghana, and I'm motivated by a desire to make a difference for people with major health challenges," Greenstreet said. "Growing up in that environment, the challenges in healthcare and opportunities to improve it are so evident."

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