In 1926 he was appointed physician in the hospitals of the city of Brussels.
After World War II he joined the Communist Party of Belgium.
In February 1946 he led the list of the party and was elected communist senator for the Arrondissement of Brussels.
He resigned in May 1947.
He was also at that time President of the Belgian Red Cross and ensured Belgium considered the positions of the Soviet Union and its satellite states, the only Western country to do so in the ICRC.
These countries refused to allow the Belgian Red Cross to participate in August 1948 at the International Meeting of the Red Cross in Stockholm.Depage broke with the communists, and in 1948 emigrated to the United States.
His correspondence was monitored by the U.S.
Government.In 1950 he was the head of a United Nations mission in Syria, on behalf of the United Nations Relief and Work Agency (UNRWA), which was engaged in providing assistance and employment for Palestinian refugees.