About 100 lawyers and staffers are poised to leave Ropes & Gray within the next few months as the Boston-based Am Law 100 firm prepares to spin-off its patent prosecution practice into an independent firm.

The move by Ropes & Gray represents a major restructuring of its intellectual property practice, the bulk of which stems from the firm’s late 2004 acquisition of 160-lawyer IP boutique Fish & Neave. Ropes & Gray, which released a statement detailing its decision, expects the process of creating a new firm focused on patent prosecution to take several months.