Abaloparatide

What is Abaloparatide?

Abaloparatide is an FDA-approved osteoporosis drug sold as Tymlos. It is a synthetic analog of parathyroid hormone-related protein, PTHrP(1-34), rather than of parathyroid hormone itself, though the two are close chemical cousins. Approved in 2017, it is used to build bone in postmenopausal women and certain men who are at high risk of fracture. Think of it as the newer sibling to teriparatide: same anabolic goal, slightly different molecule and receptor behavior.

How Abaloparatide works

Both abaloparatide and teriparatide act on the PTH1 receptor, but that receptor can sit in different signaling states. Abaloparatide was engineered to preferentially engage the state that favors bone formation, which in theory tilts the balance toward building bone with somewhat less of the calcium-mobilizing effect. Given as short daily pulses, it stimulates osteoblasts to lay down new bone, raising bone mineral density and improving bone strength. As with teriparatide, the pulsatile, once-daily pattern is what makes it anabolic rather than bone-depleting.

What the research shows

The main evidence comes from the phase 3 ACTIVE trial, which randomized about 2,460 postmenopausal women with osteoporosis to abaloparatide, placebo, or open-label teriparatide. Over 18 months, abaloparatide reduced the risk of new vertebral fractures by roughly 86 percent and nonvertebral fractures by about 43 percent versus placebo, with significant increases in bone density at the spine and hip. Follow-on data from ACTIVExtend showed those fracture benefits held up when patients transitioned to a bisphosphonate afterward. It is a smaller evidence base than teriparatide's, but it is real, controlled, human trial data.

Dosage and how it is used

The approved dose is 80 micrograms injected subcutaneously once daily from a prefilled pen. It is a prescription anabolic therapy for people at high fracture risk, and like other bone-building agents it is typically followed by an antiresorptive drug to preserve the gains. This is a clinician-managed medicine, not a self-directed protocol; dose and duration are medical decisions.

→ How to reconstitute Abaloparatide: calculator, units to draw & storage

Side effects and safety

The most common side effects are dizziness, palpitations, headache, nausea, and injection-site reactions, and it can cause a temporary rise in blood or urine calcium. Like teriparatide, abaloparatide originally carried a boxed warning about osteosarcoma, driven by rats given high doses over most of their lifespan. After post-marketing human data did not show that risk, the FDA removed the boxed warning in December 2021, while keeping a note in the warnings section. It is still avoided in people at higher baseline risk of bone cancer.

• FDA-approved with phase 3 trial data, including large vertebral fracture reduction.
• Rodent osteosarcoma finding led to a boxed warning that the FDA removed in 2021.
• A prescription drug used under medical supervision. Verify current status independently.

Frequently asked questions

References

• Miller PD et al. Effect of abaloparatide vs placebo on new vertebral fractures in postmenopausal women with osteoporosis: the ACTIVE randomized clinical trial. JAMA, 2016.
• TYMLOS (abaloparatide) injection: US prescribing information. FDA, 2017.