The proposed deal - which has been approved by the ERT board - follows a recommendation by a Special Committee of independent directors set up by the outcomes research technology and services specialist to review such offers.
Committee chair Elam Hitchner, III, said: "After completing a sale process conducted by JP Morgan, and careful and thorough analysis, together with our independent advisors, the special committee and our board endorsed this transaction as being in the best interest of the Company and our stockholders.
“We are pleased that this transaction appropriately recognizes the value of ERT as one of the leading vendors to the pharmaceutical industry, while providing our stockholders with an immediate cash realization for their investment in ERT."
This was echoed by ERT CEO Jeffrey Litwin, who said: "We are pleased to announce this transaction with Genstar, whose experienced team of healthcare executives can provide strategic oversight, as well as acquisition capital, to expand the company's service offering and market opportunities.
“They will help position ERT to better serve our clinical research clients by continuing to fund the innovative devices and services that have made us the premier provider of health outcomes research services."
San Francisco-based Genstar has around $3bn invested in various life science, healthcare, software, financial and industrial technology services firms, most notably PRA International which it bought in 2007 for just under $800m.
Genstar MD Robert Weltman said: "ERT is an attractive opportunity that fits with Genstar's outsourcing thesis within the Life Sciences and Pharmaceutical Services sector. We are excited about helping the company evolve its offering and better serve its customers."
The takeover – which is expected to complete in the third quarter pending shareholder approval – will see ERT become a privately held company and its stock will no longer trade on Nasdaq.