What are the descendents of a saber-toothed tiger?

Saber toothed cats have no modern descendants.

Although modern cats and saber-toothed cats both belong to the family Felidae, modern cats are from the sub-families Pantherinae (like lions and tigers from the genus Panthera and clouded leopards from the genus Neofelis) and Felinae (like servals, lynxes, ocelots, cougars, cheetahs, and house cats) while all saber toothed cats were from the completely separate and now extinct sub-family Machairodontinae.