An office landlord has proposed a residential conversion project in an effort to give the mostly vacant downtown building a new purpose.

KS Partners on Tuesday filed an application with the Boston Planning Department to convert its 15 Court Square office building into 80 residential units. The proposal would take advantage of the city's Downtown Residential Conversion Incentive Pilot Program.

"The Conversion Program has opened the door for projects such as this one to create an abundance of new housing in Boston, at a time where the City is in great need of residential opportunities," John Pulgini, partner at Pulgini & Norton and the developer's attorney, wrote in the filing.

The project would create 42 studio apartments, 20 one-bedroom units and 18 two-bedroom units. The conversion would take place on the second through eleventh floors.

The developer acquired the 11-story office building in 2019 from Brickpoint Properties for $29M. It was 98% leased at the time.

In February, the loan tied to the office building matured with a nearly $25M balance and was placed into special servicing, according to Morningstar Credit.

The office building was 60% vacant at the end of 2023 and that has since risen, the Boston Business Journal reported in April. Two of the remaining tenants, Environmental League of Massachusetts and Technical Assistance Collaborative, have leases expiring in 2027 and 2028, respectively.

KS Partners told BBJ in April that it had spoken to city officials about the possibility of converting the building to residential but hadn’t filed official plans until this week.

The developer is also working on the largest office-to-residential conversion in the city at 85 Devonshire St. and 258-262 Washington St., which would bring 95 apartments. The proposal won approval from the Boston Planning Department in April.