March 26 (Reuters) - EU antitrust regulators have

started an investigation into whether Zoetis ( ZTS ) blocked the

market launch of a rival pain medicine for dogs, the European

Commission said on Tuesday, a move that could result in a hefty

fine for the U.S. pet products maker.

Antitrust regulators on both sides of the Atlantic have

recently cracked down on Big Tech and Big Pharma acquiring

start-ups or small rivals in order to shut them down in what is

known as killer acquisitions.

Zoetis' ( ZTS ) Librela is currently the first and only monoclonal

antibody medicine approved in Europe to treat pain associated

with osteoarthritis in dogs.

Zoetis ( ZTS ) did not immediately respond to a request for comment.

Its shares were down 1.4% on news of the EU antitrust probe.

The EU competition watchdog said the investigation would

focus on Zoetis' ( ZTS ) acquisition of a late-stage pipeline product to

treat dog pain, which was going to be commercialised in Europe

by a third party.

"Zoetis ( ZTS ) may have engaged in exclusionary behaviour contrary

to EU antitrust rules by terminating the development of this

alternative pipeline product and refusing to transfer this

pipeline medicine to the third party which in the EEA had

exclusive commercialisation rights," the Commission said in a

statement.

EEA refers to the 27-country European Union, Iceland,

Liechtenstein and Norway.

The EU executive said this was the first formal

investigation into a potential abuse relating to the

exclusionary termination of a pipeline product which was to be

commercialised by a third party.

Companies risk fines as high as equalling 10% of their

global turnover for breaching EU antitrust rules.