SAN FRANCISCO — Highwire has appointed Michael O’Brien as CEO, replacing interim chief executive Carol Carrubba, who will remain on the agency’s executive leadership team.

O’Brien, who spent a total of 23 years at Ketchum—including more than a decade as chief client officer—joins Highwire following a brief tenure as global CEO of 5WPR. At Ketchum, he led global business development and strategic planning and oversaw efforts to reduce revenue attrition and strengthen client relationships.

O’Brien will oversee Highwire’s work across sectors including B2B technology, cybersecurity, healthcare, financial services, and sustainability. The agency has recently invested in AI-backed tools and data capabilities to support its strategic communications and marketing programs.

Carrubba said the decision to bring in O’Brien reflects the agency’s focus on scaling operations and expanding services while maintaining a people-first culture.

“Michael stood out in every way as a leader who shares our values and brings the scale, relationships, and experience to realize our vision,” she said. Carrubba has been overseeing the agency since co-founder Kathleen Gratehouse stepped down from the role in March.

“Highwire has an outstanding reputation as a strategic partner for some of the most influential brands,” O’Brien said. “I’m honored to lead the organization into its next phase, and excited to build on the entrepreneurial, inclusive, and bold spirit established by Highwire’s founders.”