Apalutamide is a structural analogue of enzalutamide and RD-162.
It is a pyridyl variant of RD-162.
Enzalutamide and RD-162 were derived from the nonsteroidal androgen RU-59063, which itself was derived from the first-generation NSAA nilutamide and by extension from flutamide.

Chemical structures of apalutamide and its predecessors
Apalutamide is a structural analogue of enzalutamide and RD-162. It is a pyridyl variant of RD-162. Enzalutamide and RD-162 were derived from the nonsteroidal androgen RU-59063, which itself was derived from the first-generation NSAA nilutamide and by extension from flutamide.
Chemical structures of apalutamide and its predecessors
Apalutamide