9.3 Anabolic & Dual-Acting Agents
Key Takeaways
Use the risk framework for the clinical population. AACE, the Endocrine Society and ACR use different criteria.
The U.S. Forteo and Tymlos labels handle use beyond two years differently. Evenity is limited to 12 monthly doses.
The Evenity boxed warning directs clinicians to avoid initiation within one year of myocardial infarction or stroke.
Plan an antiresorptive after a bone-forming course. Review transition risk before changing denosumab to another treatment.
Select therapy using the relevant risk framework
Patients at very high fracture risk may be candidates for an initial bone-forming or dual-acting agent. The risk definitions and options depend on the guideline. In postmenopausal osteoporosis, AACE lists factors such as recent or multiple fractures, fractures during approved therapy, a very low T-score (for example below −3.0) or a very high fracture probability. Its options for initial treatment at very high risk include both bone-forming and selected antiresorptive agents. The Endocrine Society recommends considering bone-forming treatment in very-high-risk postmenopausal women, for example those with severe or multiple vertebral fractures. Its romosozumab guidance also advises against treatment in women at high cardiovascular risk.
The ACR glucocorticoid guideline uses different criteria, including prior osteoporotic fracture, a T-score at or below −3.5 or very high glucocorticoid exposure in adults aged 40 or older. In its very-high-risk group it conditionally favors PTH or PTH-related peptide therapy over antiresorptives. Evaluate the individual's clinical setting and use the current drug label.
| Agent | U.S. dose and duration | Key label distinction |
|---|---|---|
| Teriparatide (Forteo) | 20 mcg subcutaneously daily. Consider lifetime use beyond two years only if the patient remains or again becomes high risk. | Labeled populations include selected high-risk postmenopausal women, men with primary or hypogonadal osteoporosis, and specified patients with osteoporosis associated with sustained systemic glucocorticoids at a daily dosage equivalent to at least 5 mg of prednisone. |
| Abaloparatide (Tymlos) | 80 mcg subcutaneously daily. Lifetime use beyond two years is not recommended. | Labeled for selected postmenopausal women with osteoporosis and to increase bone density in selected men with osteoporosis. |
| Romosozumab (Evenity) | 210 mg subcutaneously monthly as two injections, for up to 12 monthly doses. | Labeled for postmenopausal osteoporosis at high fracture risk, including the specified prior treatment failure or intolerance setting. The cardiovascular boxed warning guides initiation and monitoring. |
Explain the mechanisms with their clinical limits
Intermittent teriparatide, a PTH fragment, and abaloparatide, a PTH-related peptide analog, act through PTH1R. Bone formation can rise early, with a subsequent rise in resorption during treatment. This temporal difference helps explain the concept of an anabolic window. Marker kinetics depend on the agent, the patient and prior therapy. In laboratory receptor models, abaloparatide favored the G protein-coupled receptor conformation relative to the other conformation and produced shorter-lived signaling than teriparatide. Receptor studies do not establish equivalent fracture prevention or a porosity effect in patients.
In the teriparatide Fracture Prevention Trial in postmenopausal women with prior vertebral fractures, new vertebral fractures occurred in 5% receiving 20 mcg daily and 14% receiving placebo. In ACTIVE, abaloparatide reduced new vertebral and nonvertebral fractures versus placebo. Hypercalcemia in ACTIVE occurred less often with abaloparatide than with teriparatide (3.4% versus 6.4% in that trial). This safety comparison does not establish the reason for the difference. DATA-HRpQCT observed an increase in estimated radial cortical porosity during teriparatide treatment. That estimate is site- and method-dependent. A clinical DXA result does not directly measure the pores or establish how the local finding affects fracture risk.
Both PTH analog labels list hypersensitivity as a contraindication and have warnings advising avoidance with selected elevated osteosarcoma risks such as open epiphyses, skeletal malignancy or metastases, Paget disease or prior skeletal radiation. Avoid use in underlying hypercalcemic disorders under the respective label. Initial doses can cause orthostatic symptoms. Check product-specific instructions.
Romosozumab inhibits sclerostin, relieving inhibition of Wnt signaling, and increases formation while decreasing resorption. The anabolic effect wanes, and the label limits use to 12 monthly doses. In FRAME, new vertebral fractures at 12 months were 0.5% with romosozumab and 1.8% with placebo. In ARCH, romosozumab followed by alendronate reduced fractures compared with alendronate alone. Compare outcomes within trials.
Apply the cardiovascular warning and plan the next agent
The U.S. Evenity label says to avoid initiation following myocardial infarction or stroke in the preceding year, weigh risks in patients with other cardiovascular risk factors and discontinue if either event occurs during therapy. The label reports adjudicated major adverse cardiac events of 2.0% with romosozumab and 1.1% with alendronate during the first year in the active-controlled trial. The broader serious cardiovascular event outcome reported in ARCH was 2.5% versus 1.9%. These are different endpoints. In the placebo-controlled trial, the label reports adjudicated MACE of 0.8% in each group. Hypocalcemia and known hypersensitivity are listed in the contraindications section. For a patient with myocardial infarction eight months ago, discuss other eligible treatments.
Plan subsequent antiresorptive therapy after a bone-forming course to maintain gains. ARCH studied a romosozumab-to-alendronate sequence. Prior therapy can affect the response. In STRUCTURE, previously bisphosphonate-treated women gained total hip BMD on romosozumab and lost some on teriparatide over 12 months. In DATA-Switch, transitioning from denosumab to teriparatide alone resulted in transient spine and hip loss and progressive radius loss. Consider the denosumab transition risk before changing treatment.
Forteo label · Tymlos label · Evenity label · AACE guideline · Endocrine Society update · ACR glucocorticoid guideline
Receptor study · Teriparatide Fracture Prevention Trial · ACTIVE · DATA-HRpQCT · FRAME · ARCH · STRUCTURE · DATA-Switch
A postmenopausal woman at very high fracture risk had a myocardial infarction eight months ago. What does the U.S. Evenity label direct?
Start at half the monthly dose and use aspirin to offset the risk.
Start now if bone density is sufficiently low.
Avoid initiating Evenity within a year of the event and consider other eligible therapies.
Apply the boxed warning only to a history of stroke.
Which conclusion is supported by laboratory PTH1R binding studies and the separate ACTIVE trial?
Receptor affinities alone establish equal fracture outcomes and lower cortical porosity.
Abaloparatide and teriparatide bind sclerostin at the same receptor site.
ACTIVE directly measured radial cortical porosity and established the mechanism of hypercalcemia.
Abaloparatide favored the G protein-coupled conformation in laboratory studies, and ACTIVE found fewer hypercalcemia events with abaloparatide than teriparatide.
A 73-year-old woman with a recent vertebral fracture is starting romosozumab after risk assessment, and alendronate is an eligible option. Which sequence was tested in ARCH?
Romosozumab followed by alendronate, compared with alendronate throughout.
Denosumab abruptly followed by teriparatide, compared with alendronate.
Romosozumab plus alendronate concurrently for three years.
Romosozumab continued indefinitely without follow-on therapy.
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