The International Securities Exchange has filed a lawsuit against the Chicago Board Options Exchange alleging the CBOE's electronic trading system violates patents held by the ISE. The suit comes in the wake of another case in which ISE is suing over CBOE's exclusive deal to list index options.

The lawsuit alleges that the CBOE's Hybrid System uses an automated exchange for trading financial instruments, such as options, much like ISE's own patented technology. The suit was filed November 22 in the United States District Court for the Southern District of New York,