Sequence last week announced that it had filed suit against Avanti, alleging that Avanti's Star-RCXT product violates the Sequence patent (see related story). But Sequence did not announce that it had also filed suit against Simplex, whose Fire & Ice QX product violates the same patent, Sequence claims.

"We're building an intellectual property [IP] business, and we're serious about protecting our IP," said Greg Fawcett, senior director of corporate marketing at Sequence. "This is not the first communication we've had. At least two previous letters went to Simplex on this matter."

Penny Herscher, Simplex president and chief executive officer, said her company did a thorough review of Sequence's patent claims prior to Simplex's recent initial public offering. "We think any infringement allegations [Sequence] might make are without merit, and we will vigorously defend ourselves," she said.

Just as the Avanti lawsuit seeks an injunction against Star-RCXT, Sequence's Simplex lawsuit seeks to enjoin Fire & Ice QX, along with unspecified damages. Both cases are in the U.S. District Court of Northern California, and Mike Freeman, Sequence general counsel, said he expects both to move forward "in tandem," although with separate hearings.

Michael Santarini contributed to this story.