Even after their retirement from scientific research, the Tréfouëls continued to collaborate on various projects: Jacques was fascinated by metalwork and woodwork, and would construct furniture which Thérèse upholstered.

[1] In the early 1920s, Thérèse and her husband worked at the Pasteur Institute, in the laboratory of Ernest Fourneau — known as the father of medicinal chemistry.

By studying derivatives of arsenic, they created drugs that could be used against syphilis (Stovarsol), African trypanosomiasis (Orsanine,[1] moranyl[2]), and malaria (Rodoquine).

[1] Thérèse officially became the head of the laboratory in 1955, while Jacques served as the director of the Institute for a total of 24 years.

[4] In 1955, they were nominated for the Prix du Conseil National de l'Ordre des Pharmaciens, for their lifetime achievements in medicinal chemistry.