The deal – terms of which have not been disclosed – will facilitate global expansion according to Synexus, which suggested it may invest in research centres in the US, Asia and South America.
UK-based fund Lyceum Capital bought Synexus in 2007 for £18m ($27m) in a deal that saw it leave London's AIM just two years after it joined to raise cash for acquisitions.
Under Lyceum's ovnership Synexus's expansion continued. The patient recruitment firm increased its 13-strong network of research centers to 25 sites in eight countries through acquisitions.
Sites bought under Lyceum included facilities in the UK, Germany, Romania, Poland and Bulgaria.
Most recently, Synexus bought a fourth site in South Africa citing customer demand for more trial capacity in Africa.
CEO Christophe Berthoux said Synexus’ needs to need to continue to invest in "infrastructure and operations so that we carry on providing clients the best solution delivering thousands of patients and providing excellent quality data."
The takeover - which was brokered by Fairmount Partners - is being supported by LDC, the private equity arm of the Lloyds Banking Group, whose director Ged Gould will sit on Synexus board.
Gould echoed Berthoux’s comments about expansion.
“We are eager to further support the business break into new markets as it targets opportunities in the US, South America and Asia.”
According to financials disclosed after the buyout was announced, Synexus generated revenue of $63m in 2014, which it said was a 140% increase on that recorded in 2011. The firm also said it has $216m worth of orders, up from the $193m in saw four years ago.
Reports in the UK press suggest Synexus management and LDC paid £83m for the services firm.