SSSSnake

SSSSnake is a 1973 horror film, about deadly snakes created via a bizarre form of a serum. The film's original title though, was in fact Ssssss. It is called that obviously to mimic the sound of a snake. But you don't say it - you hiss it!

Plot
A college student becomes lab assistant to a scientist who is working on a serum that can transform humans into snakes.