Restructuring at Pfizer has claimed two more casualties, with the chief financial officer and head of reseach and development at the world's biggest drugmaker both set to depart.

The resignation of Alan Levin, the finance chief, and the departure of John LaMattina, the group's chief scientist, who will retire at the end of the year, follow the ousting of Hank McKinnell as chief executive last August.

Jeff Kindler, the new chief executive, said Mr LaMattina, who has been at Pfizer for 30 years, had helped the company to build up its oncology pipeline of drugs while increasing investment in biologics and vaccines.

"Our progress in oncology, which was a relatively small programme just ten years ago, is especially noteworthy, and we are now in an excellent position to deliver important new cancer medicines," he said in a statement.

Separately it emerged at the weekend that Nigeria’s largest state has sued US drug firm Pfizer for allegedly using 200 children as “guinea pigs” for a test of the drug Trovan Floxacin in 1996 that led to multiple deaths and deformities, officials said.

Authorities in Kano filed the suit last week at the high court, where they are seeking $2.75 billion in compensation from the pharmaceutical giant.

Last month, Pfizer said that its profit fell 17.5 per cent in the first quarter, hurt by disappointing sales of its diabetes drug Exubera. Net income fell to $3.39 billion (£1.7 billion) from $4.11 billion a year ago.

Excluding one-time items, the company reported adjusted profit of $4.8 billion, up from $4.35 billion last year. Revenue rose 6 per cent as sales of the company's bestselling drug, the cholesterol-reducer Lipitor, grew 8 per cent to $3.36 billion.

In January, the group announced plans to cut its global workforce by 10,000 people, or 10 per cent, to achieve up to $2 billion in cost savings.

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