Another milestone in the revitalization of the corridor between Broad Street and the Schuylkill has been reached with the start of leasing of 321 luxury apartments in the 28-story 1919 Market Street.

The building, a 50-50 joint venture of Brandywine Realty Trust and LCOR of Berwyn, has been under construction since October 2014.

Tenants are scheduled to begin moving into the apartments in March, said Don Tracy, LCOR vice president of development.

The 455,000-square-foot building, which cost in excess of $148 million to build, will be completed in mid-June, Tracy said.

LCOR will manage the property, which Tracy called "an exciting opportunity" for the partnership and the city.

The site had been a grassy area at 20th and Market Streets where Independence Blue Cross had originally planned a second office building. Before that, it had been the 22-story Penn Center Inn, which was demolished in 1990 to make way for the proposed second IBX tower.

About 24,000 square feet of 1919 Market Street will be retail and office, Tracy said.

There will be a CVS Pharmacy, a lobby, the property management office, and a "casual eatery" on the ground floor called the Naf Naf Grill, he said.

Independence Blue Cross will occupy the second-floor office space, with a dedicated elevator for employees from the first floor, Tracy said.

Although described as "luxury," pricing for the apartments will offer "something for everyone," he said.

"We want to be all-inclusive," he said, adding that studio apartments will start at $1,500 a month.

Studio and one-bedroom apartments comprise 75 percent of the 321 units; two-bedroom rentals 25 percent, and two- and three-bedroom penthouses, for which prices have not yet been released, 1 percent, Tracy said.

There are 14 penthouses, Tracy said.

Amenities include a state-of-the-art fitness center, a clubroom, a demonstration kitchen, a golf simulator, and an outdoor roof entertainment center with a fire pit and infinity pool.

A connected 215-car, five-story garage will be accessible and available to residents for daily and monthly parking.

Tracy said the developers were "thrilled" by the location in Market Street West.

"We are across the street from subway access and in the middle of the central business district, where most residents will likely work," he said.

Even though more high-end units are coming on the regional market, Philadelphia's Class A apartment metrics held up through 2015, said Delta Associates of Washington, D.C., which tracks this and other areas of the country.

"This trend of strong demand and more restrained construction starts . . . will sustain positive market performance in the region," Delta said.

Vacancy rates fell in the city from 5.7 percent in December 2014 to 2.8 percent in the same month of 2015, Delta said.

In the Pennsylvania suburbs, rates fell to 3.9 percent from 4.4 percent in the same period, but rose to 2.6 percent from 2.2 percent in South Jersey, Delta Associates said.

Effective rents - what landlords receive, after concessions and allowances - rose regionwide and in each submarket in that period - 2.8 percent in the city, 0.7 percent in the Pennsylvania suburbs, and 2.4 percent in South Jersey, Delta reported.

Effective rents average $2,191 ($2.40 a square foot) for high-rise product in the city and $1,508 ($1.49 a square foot) for low-rise suburban product, Delta Associates said.