CHS's 40-strong staff will move into Succinct Medical Communications, one of the 10 agencies owned by OPEN Health. The CHS brand will be phased out.
CHS was formed in 2000 and has its HQ in London.
Succinct was itself acquired by OPEN Health in February 2012, and OPEN is in turn owned by Chime, the UK group that includes Fast Track, Good Relations, VCCP and CSM Sport and Entertainment.
Sandy Royden, OPEN Health COO, said: "The range of specialist agencies across Open Health allows us to provide a full-service offering to our clients – from medical communications and market access to cutting-edge digital and public relations. The acquisition of CHS is a pivotal step in strengthening our international offering in this space and adds world-leading global publication planning to our growing portfolio."
OPEN Health was launched by former Huntsworth Health executive David Rowley in 2011, and now includes LEC Brand Communications, PR firm Reynolds-MacKenzie, data firm pH Associates and other brands alongside Succinct.