The agency, which has been hired on a retained basis, will carry out corporate and scientific comms, as well as reputation-management and profile-raising for the Paris-based pharma firm.
The company is currently developing a pioneering drug for the treatment of multiple sclerosis.
Consilium will target international business and healthcare media as well as local French media, as part of its campaign for the company.
Mary-Jane Elliott, managing partner at Consilium, said: "We are very pleased to be advising MedDay on its scientific and corporate communications. MedDay is a world-class pioneering company in the field of neurology. We look forward to continuing our work with the team as they pursue their growth strategy."