The entire transaction is valued at about $790 million, comprised of the 24.4 million company shares that were outstanding as of April 28 as well as $30.50 each shares (totalling $744.8 million).
PRA said the acquisition was approved by its board of directors. The purchase agreement is based on a 13% premium on its closing share price on July 24.
Genstar originally owned PRA before the company went public in 2004, and currently has a 12.8% holding in the company.
The transaction is expected to be completed in the fourth quarter.
PRA, which has 2700 employees, conducts clinical trials in therapeutic areas with a special emphasis in the areas of oncology, central nervous system, allergy and respiratory and cardiovascular disorders.