Resident Evil 2 began development in 1996 shortly after the original game and was originally scheduled for a March 1997 release. However, as the game was approaching its release date, the developers were unsastified with the resulting product. Rather than releasing a game they were unhappy with, the developers took the risk of developing the game from scratch. This scrapped version of the game was later dubbed Resident Evil 1.5. by the internal staff of Capcom.
This prototype version of the game starred Leon S. Kennedy from the finished game and Elza Walker, a prototype of Claire Redfield. Like Claire Redfield, Elza was a motorcyclist and college student, with the only difference being her appearance and the fact Elza had no ties to any established character from the previous games. Other supporting characters from the released game also appeared in Resident Evil 1.5. For example, Marving Branagh, a minor character who gets killed off early in the finished game played a major role in the prototype, helping Leon and Ada escape. The settings of the game were also significantly changed, with the police station in the original prototype having a more contemporary design. – [info from Wikipedia]
In early 2013 the beta / prototype version of Resident Evil 1.5 was finally leaked online, and many gamers are now able to check a part of what the game was meant to be. You can find the RE 1.5 proto / beta to download around the web, with a simple Google Search.
For more infos: Resident Evil 2: Beta Backgrounds Comparison