Westwood-based investment firm Shamrock Capital Advisors has sold its majority stake in Giant Creative Strategy in a deal valued at up to $97 million.

The company announced July 18 it had completed the sale of its San Francisco-based health care marketing agency to Huntsworth, a global health care and communications company based in London.

Huntsworth paid $72.2 million in cash at closing from Shamrock Capital Growth Fund III. The transaction is valued at up to $97.2 million based on Giant’s future performance.

“This is the beginning of an exciting new chapter for the team at Giant,” said Will Wynperle, a partner at Shamrock Capital, in a statement. “It has been a pleasure working with the team over the past several years during this critical phase of growth.”

Giant Creative Strategy, among the largest independent health care marketing agencies in the U.S., provides services for the biopharmaceutical, medical device and diagnostic industries. It has 150 employees.

Shamrock Capital Advisors, founded in 1978 as the family investment company of the late Roy E. Disney, claims $1.9 billion assets under management in media, entertainment and communications.

A Business Journal ranked Shamrock Capital the 20th largest private equity firm in Los Angeles County last April in a list ranked by private assets under management.

Health business reporter Dana Bartholomew can be reached at [email protected]. Follow him on Twitter @_DanaBart.