Abaloparatide (Tymlos)
PTHrP Analog · Anabolic Bone-Building Agent
Overview
Abaloparatide is an FDA-approved anabolic bone-building agent and synthetic analog of parathyroid hormone-related protein (PTHrP). It selectively activates the PTH1 receptor to stimulate new bone formation while minimizing bone resorption. In the phase III ACTIVE trial, abaloparatide showed superior BMD increases at the hip compared to teriparatide, with substantial fracture risk reduction. It was approved in the US in 2017 and EU in 2022 for postmenopausal women and men with osteoporosis at high fracture risk.
Abaloparatide works through selective activation of the parathyroid hormone 1 receptor (PTH1R), a G protein-coupled receptor expressed on osteoblasts and osteocytes. It preferentially binds to the RG (relaxed, G-protein-coupled) conformational state of PTH1R, which elicits a transient downstream cyclic AMP signaling response favoring anabolic bone formation over resorption. This selective binding pattern produces more bone-building activity with less hypercalcemic effect compared to native PTH. The result is increased cortical and trabecular bone volume, density, and improved microarchitecture.
FDA-approved for postmenopausal women with osteoporosis at high risk for fracture or who have failed other therapies.
FDA-approved for men with osteoporosis at high risk for fracture or intolerant to other treatments.
Phase III trials demonstrated substantial reduction in vertebral and nonvertebral fractures.
ACTIVExtend trial showed benefits of abaloparatide followed by alendronate for maintained bone protection.
Mechanism
Abaloparatide is an FDA-approved anabolic bone-building agent and synthetic analog of parathyroid hormone-related protein (PTHrP). It selectively activates the PTH1 receptor to stimulate new bone formation while minimizing bone resorption. In the phase III ACTIVE trial, abaloparatide showed superior BMD increases at the hip compared to teriparatide, with substantial fracture risk reduction. It was approved in the US in 2017 and EU in 2022 for postmenopausal women and men with osteoporosis at high fracture risk.
Abaloparatide works through selective activation of the parathyroid hormone 1 receptor (PTH1R), a G protein-coupled receptor expressed on osteoblasts and osteocytes. It preferentially binds to the RG (relaxed, G-protein-coupled) conformational state of PTH1R, which elicits a transient downstream cyclic AMP signaling response favoring anabolic bone formation over resorption. This selective binding pattern produces more bone-building activity with less hypercalcemic effect compared to native PTH. The result is increased cortical and trabecular bone volume, density, and improved microarchitecture.
FDA-approved for postmenopausal women with osteoporosis at high risk for fracture or who have failed other therapies.
Research areas
- Abaloparatide is an FDA-approved anabolic bone-building agent and synthetic analog of parathyroid hormone-related protein (PTHrP). It selectively activates the PTH1 receptor to stimulate new bone formation while minimizing bone resorption. In the phase III ACTIVE trial, abaloparatide showed superior BMD increases at the hip compared to teriparatide, with substantial fracture risk reduction. It was approved in the US in 2017 and EU in 2022 for postmenopausal women and men with osteoporosis at high fracture risk.
- Abaloparatide works through selective activation of the parathyroid hormone 1 receptor (PTH1R), a G protein-coupled receptor expressed on osteoblasts and osteocytes. It preferentially binds to the RG (relaxed, G-protein-coupled) conformational state of PTH1R, which elicits a transient downstream cyclic AMP signaling response favoring anabolic bone formation over resorption. This selective binding pattern produces more bone-building activity with less hypercalcemic effect compared to native PTH. The result is increased cortical and trabecular bone volume, density, and improved microarchitecture.
- FDA-approved for postmenopausal women with osteoporosis at high risk for fracture or who have failed other therapies.
- FDA-approved for men with osteoporosis at high risk for fracture or intolerant to other treatments.
- Phase III trials demonstrated substantial reduction in vertebral and nonvertebral fractures.
- ACTIVExtend trial showed benefits of abaloparatide followed by alendronate for maintained bone protection.
Research notes
- Hypercalciuria (high calcium in urine)
- Dizziness
- Headache
- Palpitations
- Upper abdominal pain
- Injection site reactions
- Signs of hypercalcemia (confusion, fatigue, excessive thirst)
- Persistent bone pain
- Severe dizziness or fainting
- Allergic reactions
- Paget's disease of bone
- Prior external beam or implant radiation therapy to skeleton
- Bone metastases or history of skeletal malignancies
- Metabolic bone diseases other than osteoporosis
- Pre-existing hypercalcemia
- Pregnancy or nursing
- Cumulative use exceeding 2 years lifetime
FAQs
Why is abaloparatide limited to 2 years of use?
Cumulative lifetime use is limited to 2 years due to theoretical osteosarcoma risk observed in rodent studies at very high doses. This is a precautionary measure based on animal data, and the ACTIVExtend trial demonstrated that benefits can be maintained by transitioning to alendronate after 18 months of abaloparatide.
Is abaloparatide better than teriparatide (Forteo)?
Yes. In the phase III ACTIVE trial, abaloparatide showed superior BMD increases at the hip compared to teriparatide, with substantial fracture risk reduction. It also carries lower hypercalcemia risk than teriparatide despite more potent bone-building activity.
What causes the dizziness and palpitations reported with abaloparatide?
Dizziness, palpitations, and vertigo occur in a subset of users, likely due to transient hypotension or hemodynamic changes from rapid PTH receptor activation. These effects typically subside with continued use as the body adapts. Orthostatic hypotension is a rare but serious warning sign requiring discontinuation.
Can women take abaloparatide if they're still in their reproductive years?
No. Abaloparatide is teratogenic and contraindicated in pregnancy or potential pregnancy. It's FDA-approved specifically for postmenopausal women and men with osteoporosis, making it appropriate for women beyond reproductive years.