With a master plan approved, the team behind a planned Somerville mixed-use development next to Assembly Row thinks its project, on the Orange Line’s northern stretch, is poised to poach companies experiencing growing pains in congested Boston.

“If you live in Boston and you’re anywhere near the Orange Line, this is really an extension neighborhood,” Cresset Group Executive Vice President John Baxter said. “It’s interesting how the transportation has really changed the perception of different areas.”

Cresset Group’s 1.5M SF development, which it has dubbed Xmbly, got master-plan approval from Somerville earlier this month, clearing a hurdle to move forward with construction on the 9-acre property sandwiched between Interstate 93 and Federal Realty Investment Trust’s Assembly Row. While Cresset still needs special permitting for each individual component of the project, Baxter said construction for the first phase, a residential building, is scheduled to begin in the next year.

Cresset plans to build 329-unit and 160-unit residential towers at full build-out, according to documents from project architect SGA. While the project will also feature about 20K SF of retail, the Xmbly team is promoting it more as an office and lab development than the retail-focused Assembly Row next door. But that doesn’t mean the two projects are going to be sparring partners. The kind of retail seen at Assembly is increasingly viewed as a driver for better rents at office projects like the one next door.

“Federal did a tremendous job on Assembly,” Baxter said. “It’s an amazing amenity base to have for a commercial development.”

The approved Xmbly master plan calls for a 250-foot, 388K SF office tower as well as an adjoining 200-foot, 286K SF office building. A 140K SF office/R&D-capable building along with the refurbishment of a 162K SF commercial building are also part of the mix.

“We’re going to hit all sectors,” said Newmark Knight Frank Executive Managing Director Philip Giunta, Xmbly’s leasing agent. “It could be tech; it could be a lot of firms in Boston who don’t want to keep all the freight there and move their back offices here. It’s great for lab users, and it’s great for medical users.”

Xmbly is moving forward at a time when a relief valve for East Cambridge, the tightest lab market in the country, is needed for companies looking to expand, but the life science heir apparent has yet to emerge. With direct lab vacancies routinely nonexistent, growing companies have pushed beyond Kendall Square into areas like the Seaport, NB Development Group's Boston Landing project and Route 128.

Even Harvard has entered the mix in its push to develop more of its Allston campus into a hub of innovation many are referring to as Kendall Square 2.0. But Baxter thinks Xmbly, which is a 10-minute drive from Kendall and directly on the Orange Line, has an advantage over the rest.

“All sites have their challenges: the traffic of 128, the growing pains in the Seaport, and Boston Landing is on one side of the metro area,” he said. “We think the proximity to Cambridge is really terrific here, along with the skill set of employees and easy access to the site. It competes extremely well.”