SAN FRANCISCO — Douglas Lumish is leaving the office he helped open in Silicon Valley for Kasowitz Benson Torres & Friedman. He and three other partners will join Latham & Watkins, three sources with direct knowledge of the matter said.

Lumish, who leads Kasowitz’s IP practice, will move to Latham with fellow IP litigation partners Jeffrey Homrig and Gabriel Gross, both based in Silicon Valley, and Michael Eisenberg, who is based in New York. The date of the partners’ move to Latham has not yet been determined due to their contractual obligations to Kasowitz.