She was sent to a girls' boarding school in England, studied medicine at Leeds University and began practising obstetrics and gynecology in the UK.
[1] Wanting to "impact more than the hundred or so patients I would see in a year", Greenstreet switched career, gaining a master's degree at the INSEAD Business School in France.
[1] There, she was vice-president and medical director on the executive team of GSK's UK subsidiary.
[3] As SVP of medicines development at Pfizer, Greenstreet in 2013 was named by Fast Company among the 100 "most creative people in business".
In 2021, it was announced that John Maraganore would step down as Alnylam's CEO on 1 January 2022, and would be succeeded by Greenstreet.