Exhibit 4.3 REGISTRATION RIGHTS AGREEMENT REGISTRATION RIGHTS AGREEMENT (this "Agreement"), dated as of December 16, 1997, by and among IGEN International, Inc., a Delaware corporation (the "Company"), and each of the entities whose names appear on...Registration Rights Agreement • January 30th, 1998 • Igen International Inc /De • Patent owners & lessors • New York
PURCHASE AGREEMENT PURCHASE AGREEMENT (this "Agreement"), dated as of December 16, 1997, by and among IGEN International, Inc., a Delaware corporation (the "Company"), and the entities whose names appear on the signature pages hereof. Such entities...Purchase Agreement • January 30th, 1998 • Igen International Inc /De • Patent owners & lessors • New York
