The Soho-based agency beat an undisclosed number of rivals in a competitive pitch.
It is understood there was not an incumbent, although Ash will work alongside CDM Consulting, which has a medical education and market access brief.
York has several pipeline products in the dermatology market, which is worth an estimated £5bn worldwide.
Founded by chief executive Terry Sadler in April 2003, York’s brands include fungal skin disease treatment Abasol – expected to be the company’s first launch.
Ash director Carys Thomas Ampofo will lead the account. York refused to reveal to whom she will report, saying only that it is ‘into the UK marketing team’.
The comms programme will target health professional audiences prior to launch. In addition to media relations work, the campaign will include continued professional development across prescriber audiences.
A York spokesperson said Ash’s ‘strength of expertise in dermatology’ and emphasis on evaluation were the key reasons for the appointment.
York was set up to acquire, develop and commercialise treatments to wholesalers, hospitals and GPs in Europe, the US and Japan.
In addition to Abasol, its brands include Vampex (to treat psoriasis), Sabarep (for atopic eczema) and several pipeline products.