Announcement of the 30-day exclusivity agreement came hours after K Capital Partners, a shareholder of the office and industrial REIT, said it was considering making a bid of at least $14.50 per share. K Capital Partners had called the initial offer of $14 per share "grossly insufficient."

Prime Group's stock rose 1.25% to $14.57 per share Thursday on news of K Capital's possible bid, but before the announcement of the exclusivity agreement after the market's close. When the Cadim inc. bid – it includes Prime Group Chairman of the Board Michael W. Reschke – was announced last week, the stock soared 10.5% to $14.15 per share. That's 16.6% higher than its 52-week low, set Aug. 21.

The exclusivity agreement allows for a 15-day extension, as well as break-up fees from $5 million to $20 million if Prime Group pursues better offers.

Prime Group concedes its committee of independent trustees have discussed a possible merger with K Capital but had not received an offer when it decided to enter into the exclusivity agreement with Cadim, an affiliate of Quebec-based CDP Capital.

Prime Group's portfolio includes Dearborn Center, a $350-million joint venture development more than 60% pre-leased a year before its scheduled completion, expected next year. Besides that 1.5-million-sf project, Prime's Downtown portfolio also includes the 1.35-million-sf One IBM Plaza at 330 N. Wabash Ave.; 944,556-sf 77 W. Wacker Dr.; 874,742-sf 208 S. LaSalle St.; 846,759-sf 33 W. Monroe St.; and 770,191-sf 180 N. LaSalle St.