It follows the departure of UK MD Tim Geldard for an in-house role in AstraZeneca's cardiovascular and metabolic disease (CVMD) business last year.
Preskett spent the last four years leading the PR and comms team at Havas Life Medicom, and has also previously worked in-house at Allergan, and at the agencies Edelman and Porter Novelli.
Kearney was previously a director at TogoRun, having worked alongside Preskett at Havas Life Medicom before making the move in 2015.
Both will be part of the firm's global leadership team and report to president Gloria M Janata.
Preskett said: "TogoRun was an obvious choice for me – not only because of its entrepreneurial culture and great people, but also because of the strong partnership Jonathan and I have built over the years.
"I’m looking forward to working with Jonathan again, and partnering with Gloria and the team to provide our clients with the best agency experience of their careers, while expanding our offering and growing the business further."
Owned by Omnicom, TogoRun has offices in London, New York, Washington DC, Boston and Los Angeles. It was highly commended as the international agency of the year at the PRWeek Global Awards in both 2016 and 2015.