The third chapel was begun in 1599 by Onorio Longhi, but only finished in 1610. It was built to house the funerary monument of Cardinal Giulio Antonio Santorio (1602). Over the altar and in between the column plinths is a shrine to the Madonna delle Grazie. The painting of the Madonna with Child between Saints Lawrence and Sebastian is of the 15th century and attributed to the school of the famous Umbrian painter Pietro Vannucci.