Salesforce is close to signing a big one at Transbay Tower, putting the first dent in the sky-high trophy asset set to deliver in 2016.

We are hearing from credible sources that the cloud giant is about to ink a 300k SF deal at the tower, across the street from Salesforce's new 450k SF home rising at Kilroy's 350 Mission. (This means you won't be able to throw a stone on Mission without hitting a Salesforce employee. So be careful.) Hines and Boston Properties teamed up last year to co-develop the tower at First and Mission. Hines senior managing director Paul Paradis (above) tells us there's no leasing completed at the tower yet, and had no comment regarding any potential transactions.

The 61-story Transbay Tower (underway last month, above) will peak at 1,070 feet, becoming the tallest building West of the Mississippi. (Does that count the lost city under the Mississippi?) The César Pelli-designed skyscraper will feed off of the future Transbay Transit Center, branded as the Grand Central Station of the West Coast. A Salesforce spokesman says the company doesn't comment on rumors, and its broker didn't respond to a request for comment. Salesforce has said it wants to occupy 1.8M SF in the city by 2016. Paul pointed out the website for basic tower information is now live and a marketing office will open next month. "We are available to meet with prospects and discuss leasing," he tells us.

With 1.4M SF of office space, Salesforce's potential lease would mean the tower has 1.1M SF left to go. At Bisnow's State of the Market event in January, Hines senior managing director Cameron Falconer (pictured) said he's not concerned about the amount of office space being added to the market. If anything, he's worried about the lack of options for tenants down the road. It's unclear whether Salesforce is targeting the top floors, but tower employees won't need to switch elevators to shoot all the way up. (That'll be an interesting ride, he says.)