The developer Larry Silverstein has signed his first lease for the nearly completed 7 World Trade Center, one month after state legislators passed an incentive plan to help downtown buildings, according to a published report.

American Express Financial Advisors, a unit of the credit-card company, is negotiating a 15-year lease for about 20,000 square feet at the 52-story tower just north of the main trade center site, Crain’s New York Business reported for today’s editions. “This is terrific news for downtown,” the state Assembly speaker, Sheldon Silver, who represents Lower Manhattan, told Crain’s. The Legislature approved a package of incentives last month intended to revitalize the downtown commercial district and to lure tenants to the trade center site.

The package provides tax exemptions and rent subsidies potentially worth millions of dollars to companies that move to the site of the 2001 terrorist attack. It also eliminates the commercial rent tax for tenants there and provides a five-year rent tax exemption for companies in buildings elsewhere in Lower Manhattan. There was also an agreement among officials from the city, the state, and the Port Authority of New York and New Jersey to earmark $3.5 billion in tax-free bonds for downtown projects.