1 EXHIBIT 4.5 STOCK PURCHASE AGREEMENT THIS STOCK PURCHASE AGREEMENT is made as of the 13 day of February, 1997, by and between Alkermes, Inc. a Pennsylvania corporation ("Alkermes"), and ALZA Corporation, a Delaware corporation ("ALZA"). WHEREAS,...Stock Purchase Agreement • February 27th, 1997 • Alkermes Inc • Pharmaceutical preparations • Pennsylvania