The sale marks not only the largest office building to trade hands in the Denver area so far this year, the $219 per sf is the most ever paid for a major office building in the Denver area.

However, brokers are quick to point out that the Invesco buildings at 4340 and 4346 S. Monaco St. in DTC West, are single-user buildings, and not directly comparable to multi-tenant office buildings.

The sale was handled by David Shapiro and Kevin McKinnon of the Denver office of Transwestern Commercial Services and Tom Clarke, a broker with the Dallas office of Grubb & Ellis. Tom Clarke is the father of Chip Clarke, who heads the southwest region for Transwestern, which includes Denver. Chip was previously headquartered in Denver, but now is in Houston.

The Invesco campus, where the giant Denver-based mutual fund has about 14 years left on its lease, was not being actively marketed, Shapiro tells GlobeSt.com.

But Tom Clarke, on a visit to Denver, explained that Challenger has an appetite for first-class buildings in premier office parks that are solely leased to creditworthy tenants. Shapiro and McKinnon brought four deals, and the Invesco property was by far the largest, Shapiro tells GlobeSt.com. It was also the one that Challenger liked the most.

Clarke says that Challenger previously has purchased single-tenant office buildings in New York City and in Austin. The Austin building was about the same size as the Invesco campus, while the New York City building was about twice the size, he says.

Challenger is looking to double its U.S. holdings to about $800 million from $400 million, Clarke says.