It has caused quite a bit of excitement because it is the first drug to reverse the bone loss of osteoporosis in post-menopausal women. As you mention, it is a class of drugs called diphosphate. More specifically it is an aminobisphosphonate. Phosphates are an important element in bone formation. The structure of this drug combines phosphates with what is called an amino group.
Amino groups are common in human biochemistry in a variety of settings.
Amino acids often carry small electrical charges, and have a unique spatial configuration depending on their structures. Once there, it can decrease bone loss. As you may know, osteoporosis is the loss of bone density that occurs in post-menopausal women because of the hormonal changes of menopause. As a result women who have the condition suffer from more fractures. These fractures can lead to disability and loss of independence for mature women.