Cetrotide is used in women undergoing infertility treatment for the regulation of hormone responses.
Presently, Merck Serono is marketing the product across the world except Japan.
The transaction, which is subject to the satisfaction of customary closing conditions, is expected to close on or about 1 October 2013.
Upon closing of the transaction, Aeterna Zentaris will receive €2.5m in addition to certain other payments from Merck.
As a part of the additional transitional services agreement, Aeterna will provide various transition services to Merck for a period of 36 months considering a monthly fee payment.
The transition services are intended to assist Merck in assuming responsibility for Cetrotide manufacturing.