WSJ News Exclusive | Activist Politan Capital Has 9% Stake in Masimo

An activist investor has a big stake in Masimo and plans to push the medical-device company to take action to improve its stock price following a poorly received acquisition, according to people familiar with the matter.

Politan Capital Management LP, founded by veteran activist Quentin Koffey, has a 9% stake in Masimo worth roughly $750 million, the people said. Politan’s specific ideas couldn’t be learned.