He has been involved in advising several multinational companies in antitrust proceedings before the Slovak national competition authority and antitrust investigations, including on-site assistance during dawn raids. He regularly advises clients on antitrust compliance issues, including the review of contracts and distribution models, internal antitrust audits, and preparation of antitrust compliance training. Marek is also regularly involved in merger control cases. In the pharmaceutical industry, he has been assisting clients in review of distribution models, and numerous pharmaceutical regulatory and compliance matters.