Abaloparatide is one of a small group of FDA-approved peptide drugs that actively builds new bone, rather than simply slowing bone loss, making it a distinct option in osteoporosis treatment.
What It Is
Abaloparatide, sold under the brand name Tymlos, is a synthetic 34-amino-acid peptide analog of parathyroid hormone-related protein (PTHrP). It is given as a once-daily subcutaneous injection.
How It Works
Abaloparatide binds to and activates the PTH1 receptor, the same receptor targeted by teriparatide, but it does so in a way designed to preferentially favor bone-forming (anabolic) signaling over bone-resorbing signaling. In practice, this means abaloparatide stimulates osteoblasts, the cells that build new bone tissue, more than it stimulates the bone-resorption pathways that are also activated by sustained PTH receptor signaling.
Regulatory Status
Abaloparatide received FDA approval in 2017 for the treatment of postmenopausal women with osteoporosis at high risk for fracture, and was later also approved to increase bone density in men with osteoporosis at high fracture risk. Like teriparatide, its labeling limits total lifetime treatment duration, typically to two years, based on the available long-term safety data.
What the Research Shows
Abaloparatide's approval was supported by the ACTIVE trial, a randomized, placebo-controlled study in postmenopausal women with osteoporosis, which found that abaloparatide significantly reduced the risk of new vertebral fractures compared with placebo, and also reduced nonvertebral fracture risk, a secondary endpoint not consistently shown across all anabolic bone-building agents. A head-to-head comparison with teriparatide, covered in more detail in this site's dedicated comparison article, found generally similar bone density gains between the two drugs, with some trial data suggesting a lower incidence of hypercalcemia with abaloparatide.
Safety Considerations
Like teriparatide, abaloparatide carries a boxed warning based on findings of osteosarcoma, a rare bone cancer, in long-term rat studies at doses and exposure durations far exceeding human use; it is not recommended for patients with conditions that already elevate osteosarcoma risk, including Paget's disease of bone or prior radiation therapy involving the skeleton. Orthostatic hypotension, dizziness, and elevated calcium levels (hypercalcemia) have been reported, particularly with the first few doses, and patients are typically advised to sit or lie down for the first several injections until their response is known. As with any treatment decision involving fracture risk and bone health, abaloparatide should be discussed with a physician familiar with a patient's full fracture risk profile and treatment history.
What Happens After Treatment Ends
Because abaloparatide's approved course is time-limited, patients typically transition to an antiresorptive medication, such as a bisphosphonate or denosumab, once their anabolic course ends. Research on sequential therapy has generally found that following an anabolic agent like abaloparatide with an antiresorptive drug helps preserve or further build on the bone density gains made during the anabolic phase, rather than losing that benefit once the first drug is stopped.
The Bottom Line
Abaloparatide is a well-studied, FDA-approved anabolic option for people at genuinely high fracture risk, with a mechanism and safety profile closely related to, but not identical to, teriparatide. The choice between the two, or between either and non-anabolic osteoporosis drugs, and the right follow-on treatment afterward, depends on individual risk factors that a doctor is best positioned to weigh.