Blackstone Mortgage Trust, headquartered at 345 Park Ave., plans to acquire CRE loans.

NEW YORK CITY-Blackstone Mortgage Trust said Wednesday evening it had upsized its stock offering to 22.5 million shares from the 16 million announced last week. The shares are priced at $25.50 apiece, and the Blackstone Group affiliate said it expects to realize gross proceeds of $573.8 million, or $659.8 million if the underwriters exercise their option to purchase additional shares in full.

In a release, the REIT says it intends to use the proceeds from the offering to originate and acquire an initial portfolio of senior mortgage loans and pari passu participations in existing senior mortgage loans, to originate and acquire additional CRE loans in the US and Europe and for working capital and general corporate purposes.

On May 13, Blackstone Mortgage Trust formed a new joint venture, 42-16 Partners LLC, a Delaware limited liability company, with Blackstone Holdings Finance Co. LLC, a Blackstone affiliate, to warehouse eligible assets in anticipation of closing the stock offering and entering into related financing arrangements. Its initial portfolio of first mortgage loans and pari passu interest totals $823.6 million; the largest loan in the portfolio is a $300-million mortgage on a West Coast office portfolio, according to SEC filings.

Citigroup, BofA Merrill Lynch, J.P. Morgan, Deutsche Bank Securities, Wells Fargo Securities and UBS Investment Bank are acting as joint book-running managers for the offering. Blackstone Capital Markets, Keefe, Bruyette & Woods, Evercore Partners and JMP Securities are acting as co-managers. The underwriters have been granted a 30-day option to purchase up to an additional 3.375 million shares at the public offering price.

Earlier this month, Blackstone Mortgage Trust changed its name from Capital Trust Inc. That same day, it completed a one-for-ten reverse split of its class A common stock.