Cello will pay US$6.4mln upfront, plus up to a further US$4.1mln in milestone payments.
New Jersey-based ISS, which employs ten staff, specialises in strategic counsel and regulatory support for the healthcare industry in the US.
Founded in 2000, the company helps its clients navigate advisory committee meetings with the US Food and Drug Administration.
Last year, ISS generated revenue of US$5.0mln and an adjusted operating profit of US$1.8mln.
As of 31 December 2018, the company had unaudited gross assets of about US$1.7m.
Cello expects that post completion ISS's operating profits will likely be lower than historical levels, reflecting the investment in senior headcount required as the business rapidly develops the scale of its professional base to support its growing client franchise.
“We are excited about the acquisition of ISS at this stage in our US evolution,” said Cello Health US chief executive Julia Ralston.
“ISS has built a strong reputation for provision of its scientific consulting services. Adding this technical offer will benefit our clients, particularly by tackling their biggest challenges in navigating critical scientific, commercial, and regulatory pathways to successful commercialisation.”