After 18 years performing at the tiny but storied Adrienne Theater on Sansom Street, InterAct Theatre Company will be picking up its props and sets and leading a group of four other theatrical organizations to a new, multistage home being carved out of the old Drake hotel ballroom behind the Kimmel Center.

The move, scheduled to be announced Thursday, represents something of a sea change in the city's performing arts landscape, bringing smaller producing theater companies into closer proximity to the Avenue of the Arts.

The new, as-yet-unnamed theater space, in the back of the Drake Building - formerly a hotel, now apartments - at 1512 Spruce St., will be the only multicompany theater space in regular use in the city.

Joining InterAct as resident companies will be the Simpatico Theatre Project, Azuka Theatre, and Inis Nua Theatre, as well as PlayPenn, a new-play development workshop. Simpatico has been staging work in the Adrienne's little third-floor Skybox Theater. Azuka and Inis Nua had been based at the former First Baptist Church at 17th Street and Sansom in what was known as the Off-Broad Street Theater.

But First Baptist was sold last year, and the new owner, Liberti Church, has terminated Off-Broad Street's lease.

The 8,500-square-foot performing space at the Drake, used for nearly two decades by the University of the Arts dance program, became available last year when UArts did not renew its lease, choosing to move dance operations to the refurbished Gershman Y at Pine and Broad Streets.

InterAct had been pondering a move from the cramped 106-seat Adrienne, a former home for the Wilma Theater and Susan Hess Dance, so producing artistic director Seth Rozin took a look at the vacated space, on the first floor of the iconic Drake Building.

"We immediately felt we had to move aggressively," Rozin said recently. "What was the dance stage was the size of the Adrienne stage. The ceilings were 15 feet, not 10 feet. There were no pillars. We quickly realized we'd want to put in two theaters in that huge space."

Coincidentally, Inis Nua and Azuka were engaged in what turned out to be fruitless efforts to renew their lease at the former First Baptist Church. Mike Harder, Liberti's executive pastor, said the church will be undergoing serious systems renovations this year, and the former Off-Broad space will be largely inaccessible.

"We're not opposed to renting to a theater group," he said. "We're trying to get the renovations done. . . . As far as what what we do in there, at this point, I don't know."

Tom Reing, Inis Nua's artistic director, asked Rozin whether there might be room at the Drake. Azuka producing artistic director Kevin Glaccum, another Off-Broad Street denizen, wondered the same. Both were excited by the possibilities.

"It's going to be a great performance space," Reing said. "More importantly, it's going to be a destination for new work in Philadelphia, and even nationally."

Inis Nua, which focuses on theatrical work from the British Isles, will present the last play of its current season, Enda Walsh's Penelope, at the Prince Music Theater on Chestnut Street, with previews beginning April 8.

As it happens, Inis Nua will stage the debut performance in the new space when it opens in the fall, probably in late September or early October. Reing is fairly certain of his lineup, but is keeping mum for the moment.

InterAct's first production there - Grounded, a drama by George Brant - will open within a couple of weeks of Inis Nua.

InterAct will hold a long-term lease on the space and rent it out to its resident partners.

Architectural plans call for cleaving two stages from the cavernous former ballroom, a 128-seat mainstage space, and a second one with 75 seats. Rozin envisions the lobby as a place where theater people can hang out, drink coffee, write, talk, and use WiFi.

"It could really be a game-changer for the city," said Azuka's Glaccum.

Azuka has already announced it will present its final play of this season, the Philadelphia premiere of Stephen Karam's Speech & Debate, from May 6 to 24 at Theatre Exile's Studio X, 1340 S. 13th St. It will start up again at the Drake in the fall.

"The primary thing is that it will be something of a center for new work," Glaccum said of the Drake. "I feel there's going to be a synergy there and Philadelphia will become more prominently known for the creation of new work nationally."

Even though four groups will present full seasons and PlayPenn will run its annual conference and other events, Rozin said, there will be about 35 weeks of stage time available for rentals and special programs, an important potential revenue source.

Over time, the entire cost of lease and construction will be about $4 million, far less than if InterAct were to buy or build a new home, company officials said.

Wendy White, InterAct's board chair and senior vice president and general counsel at the University of Pennsylvania, said the company had started a capital campaign and had raised about half its $1.8 million goal.

"We are confident we can do it," she said. "The Adrienne has wonderful attributes that served the company well for many years. . . . But the move to the Drake offers this collaborative, really exciting opportunity."

John Ciccone, owner of the Adrienne since 1979, said he had no intention of forgoing "legit" theater in the building. With the departure of Simpatico and InterAct, the Adrienne will host two comedy groups, ComedySportz and Philly Improv Theater. Ciccone said he would seek another theatrical group.

"I'm trying to keep it as a performing arts center," he said. "It's a strange animal owned by a private person. . . . It's been there a long, long time. I'm interested in keeping up the tradition."