Big money managers led by Fidelity Investments are close to launching a private trading venue designed to let them buy and sell large blocks of stock without the involvement of Wall Street firms and high-speed traders, according to people familiar with the matter.

Nine firms including BlackRock, Bank of New York Mellon, JP Morgan and T. Rowe Price, are forming a company that will operate a "dark pool"-a private trading venue in which activity takes place outside of the public view-the people said.