Abaloparatide is a 34-amino-acid synthetic peptide modeled on parathyroid hormone-related protein, PTHrP(1-34). It is sold as Tymlos and was developed by Radius Health under the code BA058 (also BIM-44058). The FDA approved it on April 28, 2017 for postmenopausal women with osteoporosis at high risk of fracture, and on December 20, 2022 it added an indication for men with osteoporosis at high risk of fracture (Radius Health press release).
Unlike most osteoporosis drugs, which slow bone loss, abaloparatide is an anabolic agent. It builds new bone.
How it works
Abaloparatide is an agonist at the PTH1 receptor (PTH1R). Activating that receptor drives cAMP signaling in bone cells and stimulates osteoblasts to form new bone on trabecular and cortical surfaces. The detail that distinguishes it from teriparatide (the recombinant PTH fragment it competes with) is receptor conformation: abaloparatide binds preferentially to the RG conformation of PTH1R, producing a shorter, more transient signal, whereas teriparatide favors the R0 conformation and a more prolonged response. The proposed consequence is strong bone formation with comparatively less effect on bone resorption and less hypercalcemia (StatPearls, NCBI Bookshelf).
It is given as an 80 mcg subcutaneous injection once daily from a prefilled pen.
What the trials show
The pivotal study was ACTIVE (Abaloparatide Comparator Trial In Vertebral Endpoints), a phase 3 trial that randomized 2,463 postmenopausal women with osteoporosis to abaloparatide, placebo, or open-label teriparatide for 18 months. Abaloparatide cut the risk of new vertebral fractures by 86% versus placebo and significantly reduced nonvertebral fractures as well (Miller et al., JAMA 2016, summarized via StatPearls).
A later head-to-head analysis, ACTIVExtend, followed patients who switched to alendronate after the abaloparatide course and reported continued fracture reduction, with greater vertebral fracture reduction than starting on alendronate alone (Bone et al., JAMA 2019, PubMed).
In men, the ATOM trial (Study BA058-05-019) enrolled 228 men with osteoporosis for 12 months. Lumbar spine bone mineral density rose 8.5% with abaloparatide versus 1.2% with placebo, a treatment difference of about 7.3% (p<0.0001). That bone-density result, rather than a fracture endpoint, supported the 2022 men's indication.
Regulatory and safety notes
When first approved, the Tymlos label carried a boxed warning about osteosarcoma, based on bone tumors seen in rats given high doses. The FDA later removed that boxed warning, while the label still discusses the rodent findings. Because of them, cumulative use of abaloparatide and other PTH-pathway analogs such as teriparatide is not recommended beyond 2 years in a patient's lifetime; efficacy and safety past 2 years have not been established (FDA Tymlos prescribing information).
Abaloparatide is a prescription drug, not a research chemical or supplement. It is not on the WADA prohibited list as a named substance. None of the above is medical or dosing advice; treatment decisions belong with a clinician.
The buyer-quality angle
When a compound exists both as an FDA-approved injectable and as material sold for "research use only," the gap between them is identity and purity. Pharmaceutical Tymlos is a defined formulation made under GMP. Research-grade peptide sold by a vendor is a different thing, and the only way to know what is in a vial is a third-party certificate of analysis: identity by mass spectrometry, purity by HPLC, and ideally documentation of endotoxin and residual solvents. peptideone aggregates published COAs and independent vendor ratings rather than running tests of itself; for a peptide like this, the absence of an attached, batch-specific COA is the thing to notice.