Pope Sixtus V
He participated in the papal conclave of 1585 that elected Pope Sixtus V. On 13 October 1586 he opted for the titular church of San Lorenzo in Lucina upon became cardinal protopriest. Under Pope Sixtus V, he was a prefect of the Sacred Congregation of the Index. On 11 May 1587 he opted for the order of cardinal bishops, taking the suburbicarian see of Palestrina. He was named papal legate to the Campagne and Maritime Province on 13 May 1587.