Lowenstein Sandler LLP will move its New Jersey offices to another site in Roseland, serving as the new anchor tenant in a repositioned office building that once housed a global pharmaceutical company.

The deal, announced by building owners Mountain Development Corp. and Square Mile Capital Management, calls for the firm to anchor 170,000 square feet at 56 Livingston Ave. That represents more than a third of the building — which is about a mile from Lowenstein Sandler’s existing office in the borough — with plans calling for the firm to move by 2017.

The tenant was represented by David Simson, vice chairman and chief operating officer of Newmark Grubb Knight Frank’s New Jersey offices, according to a news release. As part of its plans, the law firm will consolidate its New Jersey office and firm-wide administrative center into the new location.

The nearly 434,000-square-foot property was originally developed by Prudential Financial as part of its satellite campus before being renovated to become the U.S. headquarters of Organon International. The pharmaceutical firm was acquired by Merck in 2009, while Mountain Development, a Woodland Park-based commercial real estate firm, acquired the 56-acre campus with Square Mile in 2012 for $20 million.

In the news release, the building owners said Lowenstein’s space will be custom developed to meet its specifications, with new interiors that are being designed by Manhattan-based Marner & Associates. Those plans call for “a fully branded building within a building,” including a tree-lined “boulevard” dubbed Lowenstein Way that leads to the firm’s own private entryway.

“This is not just a deal. It’s a collaboration. When we first saw 56 Livingston Avenue, we were struck by its size, scale and quality of design,” Michael Seeve, Mountain Development’s president, said in a prepared statement. “We knew it was the ideal corporate home for sophisticated tenants with unique needs unmet by ordinary space.

“Lowenstein is that kind of tenant, and we are working together to assure that we fill out the rest of the building with equally prestigious co-tenants.”

Lowenstein will occupy the entire third floor as well as its own vertical townhouse, the news release said. Under the terms of the lease, the landlord and tenant will share the cost of the renovation, as well as major upgrades to the building overall.

“We’re creating inviting, efficient and technology-rich offices here in a wooded natural environment,” said Gary Wingens, chairman and managing partner of Lowenstein Sandler. “The space will reflect the intense energy and collaborative nature of our firm, which, along with the terrific amenity package, will certainly help us recruit and retain top talent.”

Wingens added that the firm “learned an enormous amount from the recent expansion and remodeling of our Rockefeller Center offices, and we plan to bring much of that learning to New Jersey, while adapting it to the beauty of the local environment.”

The new spaces in the repositioned office — including conference rooms, collaboration areas, coffee bars, exterior lounges and a 400-seat cafeteria — will be designed to maximize both the natural light and the surrounding environment. Infrastructure improvements also include a dedicated data center with a network operations center, communications network, security and primary and secondary power systems to ensure that the building is operational 24 hours a day.

Square Mile Principal Matthew Drummond noted that 56 Livingston Ave. is located along Interstate 280 and “has already served two major companies very well.” He said the building can accommodate large and smaller users from different industry sectors.

“We recognized this when we decided to enter into this, our second venture with MDC, and we have great confidence in the ultimate success of this partnership,” Drummond said.

Brown & Brown, the international insurance company, currently occupies 29,500 square feet at 56 Livingston Ave. There is about 130,000 square feet of available space remaining.

“The tenant, the owners and the township all netted huge benefits,” Simson said in the news release, “Lowenstein can consolidate their operations into great space offering their long-term vision and objectives, MDC and Square Mile can turn around a huge property and attract additional high-end tenants, and Roseland will retain its outstanding corporate presence.”

For Mountain Development, it is the second deal involving a prominent New Jersey law firm in recent years. The firm earlier this year opened the new West Windsor headquarters of Hill Wallack LLP, which anchors a 62,500-square-foot building developed by Mountain Development and Gottesman Real Estate Partners.