How effective are the currently available anabolic bone agents?
Teriparatide (Forteo) is a 34 amino acid fragment of intact PTH that retains the ability to bind to and activate PTH receptors on osteoblasts and osteoblast precursors. It is self-administered daily at a 20 mcg/day dose SC for 18 to 24 months. In trials, teriparatide increased lumbar spine bone mass by 9% to 13% and hip bone mass by 2.5% to 5% while decreasing the relative risk of new vertebral fractures by 65% and nonvertebral fractures by 50%. The most common side effects are similar to placebo and include headache, nausea, arthralgias, orthostasis, and flushing. Teriparatide must be refrigerated for the duration of its use; it becomes inactivated if left unrefrigerated for over 24 hours.
Abaloparatide (Tymlos) is a 34 amino acid fragment of PTHrP that also activates osteoblast recruitment and activity. It is self-injected at an 80 mcg SQ daily dose, and its use is limited to 24 months. Spine BMD has been shown to increase by 10.4% and hip BMD by 4% compared with placebo. In a head-to-head trial against teriparatide, abaloparatide reduced new vertebral fractures by 86%, nonvertebral fractures by 43%, and major osteoporosis fractures by 70% (the reduction in major osteoporosis fractures was statistically significantly better than teriparatide). Side effects are similar to those reported with teriparatide. Abaloparatide does not require refrigeration.