AstraZeneca's new chairman took the helm on Friday and said the troubled drugmaker faced "a period of significant change".

Leif Johansson's first priority is to find a permanent replacement for chief executive David Brennan, who is stepping down in an abrupt exit after six years in the job.

But the more fundamental question for the company's new non-executive chairman is whether to steer AstraZeneca towards bold acquisitions or further cost cutting.

Johansson, who has a track record of taking tough decisions after restructuring Swedish truckmaker Volvo, gave little away in a brief statement marking his arrival in the hot seat at Britain's second biggest drugmaker.

"The pharmaceutical industry is facing major challenges and I look forward to helping AstraZeneca to navigate a period of significant change," he said.

"The company has a strong executive team in place who, under Simon Lowth's leadership, will provide clear direction for the business while the board completes the search for a new CEO, which is my immediate priority."

Finance head Lowth was appointed interim CEO from June 1, after the announcement of Brennan's departure on April 26. He is also viewed as a candidate for the position in the long term, alongside external candidates.

Headhunters Spencer Stuart have been appointed to help with the CEO search.

For several years, AstraZeneca kept investors happy with a strategy of hefty dividend payments and share buybacks, but more recently key shareholders have grown restive about its failure to develop promising new medicines.

The group has suffered repeated drug development setbacks, stoking fears about its long-term prospects given a complete reliance on prescription medicines at a time when rivals have diversified.

Strategic review

As top management prepares to conduct its annual strategic review over the summer, investors remain split about the best way forward. The divisions are reflected in two very different assessments of the company by analysts this week.

Seamus Fernandez of Leerink Swann believes AstraZeneca needs a new CEO with extensive pharmaceutical industry experience who is ready to do bold deals to replenish the company's product portfolio. "The next CEO must act decisively on M&A opportunities," he said in a research note.

Leerink sees Amylin Pharmaceuticals - currently up for auction - as well as Forest Laboratories, Salix Pharmaceuticals and Shire as possible takeover targets.

Stephen McGarry of Societe Generale, however, takes a very different view, arguing that the company could do better to shrink its business further.

By significantly reducing research, sales and marketing, AstraZeneca would boost earnings and effectively become a specialty pharma company. That could make it an attractive M&A target for other specialty pharma players or larger drugmakers.

AstraZeneca faces a slump in sales as its old blockbusters fade out with no obvious replacements. Its antipsychotic drug Seroquel lost patent protection in March, while heartburn pill Nexium and its top-selling heart drug Crestor lose U.S. protection in 2014 and 2016 respectively.

Its problems mean the shares trade at under seven times this year's expected earnings, the lowest multiple for any major international drug company.