Yes it's possible but personally I encounter few problems, sometimes it works, sometimes not.
Uncaught TypeError: Cannot read property 'prototype' of undefined
PS : Don't forget to call super methods if you use them.
class A extends Sup.behavior {
awake() {
Sup.log("Awake from A");
}
}
class B extends A {
awake() {
super.awake();
Sup.log("Awake from B");
}
start() {
Sup.log("Start from B");
}
}