The Purlieu Experiment, Book 1. The Mascot Trilogy, #1

Donte is a Mascot - a genetically modified human. He is the offspring of Mascots designed by a group of scientists known to the inhabitants of Purlieu only as "The Parliament." Mascots were programmed for leadership. They lived longer, were stronger and more intelligent than their human counterparts. And yet, the humans were resistant to a plague that swept through all the colonies but one. The plague killed many of the male Mascots and left most of the remaining sterile.
Donte, safe in his mother's womb throughout the plague, was an exception. Being the only fertile male Mascot in two colonies made him distinctive enough, but Donte was also a descendant of the leaders of two colonies. His heritage had made him a target and his integrity kept him a captive. Donte is a captive in Nyumbani, one of the original five colonies of the Purlieu Experiment. Their insane king has been conducting raids on other colonies, but for Donte, he crosses the line when his raiders take a captive and plan to kill her.
Donte does the only thing he can to save her - he kills the king. A last-minute change in punishment from execution to being exiled from the colony means his escape route is over the snow capped mountains in scant clothing. He must take the girl over the mountain and across a desert to her colony. Donte believes the only way the colonies can progress is to unite. He gets help and resistance in some unexpected areas.
In spite of all the obstacles thrown in his path, Donte keeps his momentum until tragedy makes him falter and lose faith in himself. He must retain that faith if he is to meet the final challenge.