AstraZeneca's new chief executive stamped his authority on the struggling drugmaker on Tuesday by removing the heads of research and commercial operations.

Pascal Soriot, who took the helm at Britain's second-biggest pharmaceutical company in October, said the roles held by Martin Mackay and Tony Zook respectively had been eliminated and both men would leave the company at the end of January.

Instead, Soriot is creating three senior research and development (R&D) roles responsible for discovery and early stage development in small molecules, biologics and late-stage development.

On the commercial side, three positions will in future represent the different regions, with a further senior role responsible for global portfolio and product strategy.

Soriot, a former Roche executive, is striving to return AstraZeneca to health in the face of one of the industry's steepest patent "cliffs" - when patents expire and drugs face generic competition.

He is expected to set out his ideas for the group when he presents full-year results on Jan. 31. A more in-depth presentation on strategy for analysts and investors is slated for March.

Soriot's first decision on taking office was to suspend share buybacks, prompting immediate speculation that he will embark on more acquisitions to replace lost revenue. But he is also likely to re-focus both R&D and marketing operations in a bid to make the most of existing assets.

The company is not alone in facing big patent losses, but while rivals like GlaxoSmithKline and Sanofi have now put the worst behind them, AstraZeneca still has the worst to come. Its two biggest selling drugs - Nexium for stomach acid and the cholesterol fighter Crestor - will lose U.S. protection in 2014 and 2016.

Soriot's new line-up for the key R&D functions will see Mene Pangalos take over as head of innovative medicines, with Bahija Jallal responsible for biologic drug development at the MedImmune unit, and Briggs Morrison heading up global medicines development.

"This new senior executive team structure, that draws heavily from the leadership talent within the company, enables us to bring an even sharper management focus to key pipeline assets, key brands and key markets, and helps us further accelerate decision-making," Soriot said.