After closing his firm Exis Capital Management Inc., hedge-fund manager Adam Sender announced that he will sell nearly half of his contemporary art collection at Sotheby’s. Since 1998, with guidance from New York-based art adviser Todd Levin and various Chelsea gallerists, Sender has amassed a collection of approximately 800 works by 139 artists.

Over the course of 18 months, Sotheby’s will sell about 400 works from Sender’s collection, including pieces by Cindy Sherman, Richard Prince, John Baldessari and Dan Flavin. The collection is expected to fetch over $70 million.

The first selection of works from Sender’s collection will be offered on May 14 at Sotheby’s important evening sale of contemporary art.