The incumbent, Shire Health International - now ShireHealth PR - was invited to repitch but declined.
Carrie Deverell, AZ global communications director for lung cancer, said it was a ‘mutual' decision to part ways.
She added: ‘We were in the natural lifecycle of looking to tender for a new agency or asking our old agency to repitch.'
ShireHealth MD Matt de Gruchy said there were ‘various reasons' for the decision not to repitch after five years on the account, but would not elaborate.
Lee Tomkins, European healthcare practice leader at Porter Novelli, will lead a team of five on the brief, including UK healthcare director Rebecca Hunt. The agency will not be handling local implementation of Iressa and Zactima campaigns in any markets.
Hunt said it will concentrate instead on ‘overarching strategic communications' and helping AZ to develop relationships with stakeholders such as oncologists and patient groups.
Tactical comms will include a presence at June's annual meeting of the American Society of Clinical Oncology in Chicago.
Iressa is not yet licensed for non-small-cell lung cancer in the US or Europe, while Zactima is currently in Phase III trials.