In the future, humanity develops a "fountain of youth" drug, but as many people around the world begin to take it, most begin to mutate into a barbaric proto-humanoid state. The few people immune to this side-effect of the drug band together and live in a futuristic city while the mutants live in the vast wasteland outside its gates. In an effort to save the human race and understand what went wrong, the city sends out research missions in fortified vehicles to bring back mutated humans for research, and to rescue healthy humans. The film focuses on one such squad of soldiers and scientists.

References:
https://en.wikipedia.org/wiki/Island_City_(1994_film)