Ralph Dorotheo takes a sample from a bio-reactor in a lab at MedImmune. (Jeffrey MacMillan/JEFFREY MACMILLAN)

Pharmaceutical behemoths New York-based Pfizer and London-based AstraZeneca are waging a trans-Atlantic battle over a potential multibillion-dollar buyout that has put both companies and their respective governments on the defensive.

The kerfuffle raises questions about the future of 3,100 scientists and manufacturers employed in the Maryland offices of MedImmune, a biotechnology company that local officials worry could be gutted if its corporate parent, AstraZeneca, gets bought.

Projections about MedImmune’s future are speculative at this point, of course. Pfizer’s desire to purchase AstraZeneca has yet to win over executives of that company, let alone shareholders and regulators.

But that hasn’t stopped area business and government officials from touting the merits of MedImmune, which has become integral to AstraZeneca’s research efforts since it was acquired for $15.6 billion in 2007.

MedImmune’s roster of biologics under development represents half of AstraZeneca’s worldwide drug pipeline. What’s more, a handful of drugs in late-stage clinical trials could go before the Food and Drug Administration for approval in the next few years.

“In the drug development cycle, this is the fastest [expansion] I have seen, from being 5 percent of AstraZeneca’s pipeline to 50 percent in just seven years,” said Bahija Jallal, head of MedImmune.

“The investment that AstraZeneca made here is bearing fruit,” she added.

Jallal declined to comment specifically on Pfizer’s acquisition proposal.

MedImmune backed its assertion with a pair of announcements last week that treatments for lupus and rheumatoid arthritis showed promising results in second-phase trials.

The company has also begun to aggressively pursue an up-and-coming area of medicine called immunotherapy that uses drugs to trigger the body’s natural immune system to fight cancer.

Anthony Coyle is familiar with MedImmune’s work. He joined Pfizer as vice president of the company’s Centers for Therapeutic Innovation in 2010 after six years in top research roles at MedImmune.

“The pipelines are more complementary than overlapping on exactly the same programs,” Coyle said.

Pfizer maintains large research hubs on the East Coast in Andover and Cambridge, Mass., and Pearl River, N.Y. The company has smaller administrative offices in D.C. and Virginia.

Maryland lawmakers penned a letter to Pfizer last week asking the pharmaceutical giant to ensure that it will not shed jobs at MedImmune’s locations in Gaithersburg and Frederick should it succeed in acquiring AstraZeneca.

“The MedImmune research facility in Maryland has an international reputation for world-class expertise and is located in the heart of our nation’s biotech corridor near the National Institutes of Health. If a deal moves forward, Pfizer would benefit greatly from maintaining their Maryland facilities and workforce,” the letter said.

The letter was signed by Sens. Barbara A. Mikulski and Ben Cardin, as well as congressional Reps. C.A. Dutch Ruppersberger, Chris Van Hollen, John Sarbanes and John K. Delaney, all Maryland Democrats.

British lawmakers have raised similar concerns that an acquisition could mean the loss of jobs in the United Kingdom. Pfizer sought to assuage those concerns by pledging to keep jobs there should a deal go through.

A spokesman said Pfizer would respond to lawmakers’ concerns, adding “we see MedImmune as a strong complement to Pfizer’s existing research efforts in a potential combination with AstraZeneca.”

Ian Read, Pfizer’s chief executive, responded to similar concerns in a May 12 letter to Maryland Gov. Martin G. O’Malley. He said MedImmune “demonstrates incredible value to patients by developing innovation driven biopharmaceuticals. Leveraging biological advances to develop small and large molecule medicines, MedImmune’s modality independent approach to research and development ... could create an enhanced research portfolio in key areas such as oncology, immunology and cardiovascular disease.”