In 1981, Chugai
Pharmaceutical succeeded in marketing
alfacalcidol, a
prodrug of
calcitriol, as a therapeutic agent for
renal osteodystrophy. In 1983, Chugai succeeded in extending the application of
alfacalcidol to the treatment of
osteoporosis as well. Clinicians in Japan have accepted
alfacalcidol as a remedy for
osteoporosis. However, the use of
calcitriol and its analogs for the treatment of
osteoporosis is still controversial. Some misunderstandings exist internationally about the efficacy of the active form of
vitamin D for the treatment of
osteoporosis. It is important to emphasize that patients with
osteoporosis have intestinal
calcium malabsorption and dysfunction in renal activation of
vitamin D. When massive doses of parent
vitamin D were administered to OVX rats, bone mass increased, but surprisingly, many porotic area were observed in the cortical bone. On the other hand, administration of
alfacalcidol increased physiological bone without porotic observation. It is necessary to give the active form of
vitamin D, D-
hormone, with an RDA-equivalent supply of
calcium.
Alfacalcidol forms physiological strong bones that are hardly fractured by regulating
calcium and bone metabolism. We proposed a new
vitamin D analog, 2beta (3-hydroxypropoxy)calcitriol [
ED-71] as a therapeutic
drug for
osteoporosis, which is more potent than
calcitriol.
ED-71 is now being investigated in phase 2 clinical studies in Japan.
ED-71 will appear as more improved drugs for
osteoporosis until 2010.