Novartis AG said Wednesday that it will expand in Cambridge as part of a major overhaul of its biomedical research operations, one of the biggest in the world.

The Swiss pharmaceutical giant will add an early-stage drug discovery team and a respiratory disease research group in the city, where it already has about 2,500 employees in all or part of 10 buildings.

The restructuring was unveiled by Jay Bradner, who took over in March as president of Cambridge-based Novartis Institutes for BioMedical Research, at an afternoon “town meeting’’ with local employees. Bradner held similar meetings in recent days in Singapore, where Novartis is closing a lab, and at a sister research center in Basel, Switzerland.

Bradner said it was too soon to specify how many more scientists Novartis will hire in Cambridge. He said more details will be disclosed in January. The company is the state’s fourth largest biopharma employer after Sanofi Genzyme, Biogen Inc., and Shire PLC.

Novartis is in the process of “ruthless prioritizing’’ of all its research programs, building up some areas and combining others to improve efficiency, Bradner said in an interview. “This is a very competitive space, and we need to play to win for patients,’’ he said.

The new plan involves strategic shifts not only in the structure of the Novartis research organization but also in its scientific programs and culture.

A new early discovery research team, called the chemical biology and therapeutics group, will be co-located in Cambridge and Basel with the aim of generating new types of small molecules and biomolecules to “illuminate human biology,’’ Bradner said. Two existing research units, working on molecular pathways and proteomics chemistry, will be merged into the new group, but Bradner said Novartis plans additional hiring in Cambridge and elsewhere.

In contrast to current research approaches, which seek to first identify disease targets, he said Novartis scientists in the new group will use phenotypic screening and gene editing tools to initially assess therapeutic responses to molecules and later determine the targets.

The goal is to boost the number of molecules in the Novartis chemical library — the starting point for drug discovery — from 3 million to 300 million in three years, Bradner said.

Novartis, which has a total of about 6,400 research employees worldwide, will also create “centers of excellence’’ in Cambridge and Basel to explore new ways of delivering medicines. At the same time, it will shutter an 84-person biologics group in Singapore, moving the research to a site in Emeryville, Calif., and a 73-person group near Zurich, Switzerland.

The company will also be moving cell and gene therapy research into a broader cancer research unit seeking to link immuno-oncology with targeted therapies. Novartis this summer eliminated more than 100 jobs in its gene and cell therapy research unit in a prelude to the reorganization. None of those job cuts affected its Cambridge operations.

Novartis, which has scaled back its research on respiratory diseases in recent years, will be reinvesting in a new Cambridge-based research group focusing on treatments for diseases such as asthma, cystic fibrosis, and chronic obstructive pulmonary disease.

Bradner said the Novartis restructuring will seek to better align early and late-stage drug development to accelerate the approval of new therapies. It will also try to break down barriers among research groups and create a more open and nimble culture of collaborating with outside scientists. And promoting the career development of researchers will be a priority.

“We envision a powerful new drug discovery engine in this organization,’’ Bradner said. “We’re putting out a call to all chemical biologists, an all-points bulletin of sorts. We’re very interested to recruit in this area.’’

Robert Weisman can be reached at robert.weisman@globe.com. Follow him on Twitter @GlobeRobW.