Gov. Martin O'Malley and Delaware Gov. Jack Markell sent a joint letter to Pfizer Thursday expressing concerns about its proposed $106 billion acquisition of pharmaceutical firm AstraZeneca, which employs thousands in both states.

The governors said they earlier asked for but did not receive assurances from Pfizer that it intends to preserve those jobs, though they said the company made such promises to British leaders about jobs there.


"Our concern is exacerbated by Pfizer's history of closing U.S. research facilities, including sites in Michigan and Illinois, after closing on previous corporate transactions," they wrote.

AstraZeneca, which bought Gaithersburg-based biotech firm MedImmune in 2007, employs about 3,100 people in Maryland. The company has 2,600 jobs in Delaware.

A Pfizer spokeswoman said in a statement that the company had spoken with the governors about the potential acquisition.

"We understand and appreciate their concerns," the statement said. "We have great respect for AstraZeneca and its rich heritage. We believe this potential combination presents an excellent opportunity to create a leading company in our global industry.

"We believe a potential combination with AstraZeneca would build a stronger company by bringing together our assets, people and scientific expertise to create vibrant businesses with new potential growth and opportunities to meet patients' needs."

Baltimore Sun reporter Colin Campbell contributed to this article.