Pharmaceutical giant Pfizer Inc. said Wednesday that it has completed the move of one of its research units from Groton to Cambridge, Mass., and plans to complete the relocation of another group of scientists by the middle of next year.

Pfizer said that its cardiovascular and endocrine disease research unit completed its move to Massachusetts this summer and that its neuroscience unit would follow next year. The announcement came as the New York-based company said it had signed a 10-year agreement with the Massachusetts Institute of Technology to move the two research units into a new 180,000-square-foot research headquarters in Cambridge's Kendall Square.

"This is a very exciting period in Pfizer R&D," Pfizer Senior Vice President Rod McKenzie said in a statement. "By expanding our presence in one of the world's great centers of scientific and medical innovation, we will provide the best environment for our researchers to invent the next generation of medicines in areas of greatest need, such as Alzheimer's disease, schizophrenia, diabetes and cardiovascular disease."

Pfizer said 400 to 450 researchers - many currently working in Groton - would eventually populate the new Cambridge site at 610 Main St. South, which won't be ready for occupancy until late in 2013. The company added that scientists previously working in the Groton cardiovascular research unit were sent to an interim location at 620 Memorial Drive in Cambridge, and that researchers now in the local neuroscience unit would be making a similar interim move in the second quarter of next year.

Pfizer said the Cambridge site will recruit about 40 percent of its employees in the Massachusetts area, while 60 percent of the scientists will come from other company research sites, principally Groton. The company said Tim Rolph will continue to head up the company's cardiovascular unit, while neuroscience-unit chief Mike Ehlers will be making the move to Cambridge as well.

Pfizer said a third Groton research unit, involving the study of anti-infective medications, is in transition.

"We are building a research unit in Shanghai that will support our current and future anti-infectives portfolio," Pfizer spokeswoman Kristen Neese said in an email response to questions. "As we build this new research unit in Shanghai, we will continue to run our existing clinical and pre-clinical programs in the U.S. to ensure uninterrupted progress on these important programs in areas of high unmet medical need."

The research moves are part of a major downsizing of local Pfizer operations that will eventually result in the loss of 1,100 positions in Connecticut by sometime next year.

About 3,400 Pfizer employees will remain at the Groton campus, which became the sole remaining company site in the region when the last worker vacated the former Pfizer Global Research & Development headquarters in New London in June.

While some local officials have worried about Pfizer's commitment to Connecticut as it moves many of its most important discovery scientists to Massachusetts, the company said its Groton campus will be more than a support center for R&D.

"Every new Pfizer medicine in development will come through Groton on its way to patients," Neese said.

She added that Groton will continue to perform many of the functions of discovery science, including early screening of potential therapeutic compounds, identifying and assessing the most promising drug candidates and on-site organic and synthetic chemistry work.

"The Pfizer Connecticut R&D laboratories will remain Pfizer's largest research site," Neese said.

"Colleagues at the site will continue to play a critical role in turning discoveries into medicines as Pfizer's Center for Discovery and Development Sciences. It is anticipated that the site will be involved either directly or indirectly in advancing the Pfizer's R&D portfolio."

l.howard@theday.com