Bringing more than 20 years’ experience, Toole previously held roles with Procter and Gamble, ResMed and Sublimity Therapeutics.
He will be appointed to the board “as soon as possible”, the pharmaceutical services company said.
"I am delighted that we have appointed Leo as CFO,” said Open Orphan chairman Cathal Friel.
“He has worked with Open Orphan for the past year and is therefore well placed to assist with the rapid integration of hVIVO, deliver on our synergies programme and target profitability in the near term.
“We feel he is an important addition to the executive team as we target the rapidly growing CRO pharmaceutical services sector."