Spoiler for Hidden:
Centuries later, humanity finds new hope in King Arthur and the Knights of the Round Table. King Arthur and his like-minded knights take the fight to the half breeds, but Arthur soon realizes it's a losing battle. Through a mysterious turn of fate The Knights discover Black Water, a mystical liquid that significantly extends their lifetimes and gives them remarkable healing abilities. Despite this new advantage the half breeds continue to win battle after battle, until the industrial Revolution turns the tide."
According to wikipedia the lycan have been around long before black water was discovered. Plus if black water made them become lycan, why would they keep using it? Modern tech that's helping them win the war could also be used to heal them if it was such a problem.