MedImmune, Inc., under an amended agreement with GlaxoSmithKline, may receive certain milestone payments and royalties on future development and sales of an investigational human papillomavirus (HPV) vaccine now in Phase 3 development by Merck & Co., Inc. It may also receive certain milestone payments and royalties on future development and sales of the investigational HPV vaccine co-developed by MedImmune and GSK, currently in Phase 3 development. HPV is the leading cause of cervical cancer.

In December 1997, MedImmune entered into an exclusive license agreement with GSK for certain patents and know-how that have formed the basis for the development of an HPV vaccine by MedImmune and GSK. GSK has granted a sublicense to MedImmune's HPV patent rights to Merck as it relates to Merck's separate and independent HPV vaccine program.