Teriparatide: Forteo/Bonsity bone-building drug for osteoporosis
A lab-made version of parathyroid hormone that stimulates the body to build new bone; FDA-approved for osteoporosis in people at high risk of fractures.
A researcher, an agent, or an algorithm wrote down the sequence and picked a target to hit.
An AI model like OpenFold3 or AlphaFold built a 3D structure and scored how well it fits the binding site.
A second contributor repeated the computation on their own hardware and the scores matched.
A chemistry service or a researcher ordered the sequence, it was manufactured, and mass spectrometry confirmed the right molecule was produced.
A binding or activity measurement confirmed that it actually does what the computer predicted — or didn't.
What this is
Teriparatide (brand name Forteo; biosimilar Bonsity) is the 34-amino-acid N-terminal fragment of human parathyroid hormone, produced by recombinant DNA technology. It is the first osteoanabolic agent — a drug that stimulates new bone formation rather than simply slowing bone loss — approved for osteoporosis. Teriparatide received FDA approval in November 2002 for postmenopausal osteoporosis at high fracture risk and was subsequently approved for osteoporosis in men and for glucocorticoid-induced osteoporosis. The EMA approved it in June 2003 (as Forsteo). A biosimilar, Bonsity, received FDA approval in May 2019 (Leder, Curr Osteoporos Rep 2017).
History
The PTH paradox — that continuous parathyroid hormone exposure produces net bone loss while intermittent, pulsatile exposure produces net bone gain — was documented experimentally as early as 1929 and revisited by Reeve, Meunier, and others in small human studies during the 1970s and 1980s. The hypothesis: transient PTH receptor activation preferentially drives osteoblast survival and activity, whereas sustained occupancy shifts the balance toward osteoclast-mediated resorption. Eli Lilly developed teriparatide — the 1-34 N-terminal fragment, which retains full receptor-binding activity — as the shortest fully functional PTH fragment amenable to recombinant expression and once-daily subcutaneous delivery. The pivotal Phase 3 fracture trial (Neer and colleagues, NEJM 2001) was halted at a median of 18 months after rat carcinogenicity studies revealed osteosarcoma at high lifetime doses — a finding that was never reproduced in more than 20 years of subsequent human pharmacovigilance. FDA approval followed on November 26, 2002, accompanied by a black box warning and a 24-month lifetime use restriction. That black box warning was removed by the FDA in 2020 based on accumulated post-marketing safety data (Leder, Curr Osteoporos Rep 2017). The Marcus (2011) personal account documents the early development history of teriparatide from within the Lilly program (Marcus, Osteoporos Int 2011).
What it does
When given as a once-daily injection, teriparatide produces a transient two-to-four hour peak in PTH receptor occupancy followed by receptor desensitization. This pulsatile stimulation preferentially activates bone-building cells (osteoblasts): it increases osteoblast number by reducing programmed cell death, activates quiescent lining cells to resume bone synthesis, suppresses sclerostin production from osteocytes (lifting inhibition of the Wnt bone-formation pathway), and stimulates new bone deposition on both periosteal and endosteal surfaces. Bone resorption also rises — teriparatide is not purely anabolic — but the net effect, particularly at trabecular bone, is strongly positive. Lumbar spine bone mineral density increases approximately 6–10% over 12–24 months; hip BMD increases more modestly (Leder, Curr Osteoporos Rep 2017).
Evidence
- Human (pivotal Phase 3, postmenopausal osteoporosis): Neer and colleagues (NEJM 2001) randomized 1,637 postmenopausal osteoporotic women to teriparatide 20 µg/day, 40 µg/day, or placebo for a median of 18 months (trial stopped early on precautionary grounds): new vertebral fracture risk was reduced by 65% (20 µg) and 69% (40 µg) relative to placebo; non-vertebral fragility fracture risk was reduced by 53% (20 µg) and 54% (40 µg); lumbar spine BMD increased 9.7% (20 µg) and 13.7% (40 µg); total hip BMD increased 2.6% (20 µg). A modest decrease in distal radius BMD (−2.1% at 20 µg) was also observed, a characteristic effect at cortical-rich sites.
- Human (osteoporosis in men): In a trial of 437 osteoporotic men, BMD changes were similar to those seen in women at 11 months; a 30-month follow-up showed 83% fewer vertebral fractures in the teriparatide group versus placebo (Orwoll and colleagues, cited in Leder, Curr Osteoporos Rep 2017).
- Human (glucocorticoid-induced osteoporosis): An 18-month trial in 428 women and men with glucocorticoid-induced osteoporosis found that teriparatide produced larger spine and hip BMD increases and significantly fewer new vertebral fractures compared with alendronate; an 18-month extension confirmed the vertebral fracture advantage (Saag and colleagues, cited in Leder, Curr Osteoporos Rep 2017).
- Human (combination with denosumab): The DATA trial randomized 94 postmenopausal osteoporotic women to teriparatide, denosumab, or both for 24 months: lumbar spine BMD at 12 months was +9.1% (combination), +6.2% (teriparatide alone), and +5.5% (denosumab alone); total hip at 12 months was +4.9% (combination) versus +0.7% (teriparatide alone). The cortical bone loss at the distal radius seen with teriparatide alone was prevented by the denosumab combination (Leder and colleagues, cited in Leder, Curr Osteoporos Rep 2017).
- Human (comparison with bisphosphonates): Systematic reviews and network meta-analyses consistently show teriparatide exceeding bisphosphonates for lumbar spine BMD gain at 18–24 months; hip BMD gains are similar or slightly lower. Co-administration of bisphosphonates attenuates the anabolic response (Leder, Curr Osteoporos Rep 2017; Sato and colleagues, JBMR Plus 2021).
- In vitro / mechanistic: Differential PTH1R signaling kinetics between teriparatide, abaloparatide, and long-acting PTH analogs have been characterized at the intracellular level; despite distinct downstream biological effects, initial engagement of major signaling pathways is comparable across these ligands (Sato and colleagues, JBMR Plus 2021). Receptor conformation selectivity studies show that abaloparatide preferentially stabilizes the RG conformation, explaining its different cortical vs. trabecular BMD profile relative to teriparatide (Hattersley and colleagues, Endocrinology 2016).
Myths and misconceptions
- "Teriparatide causes osteosarcoma in humans" — The osteosarcoma signal arose from lifetime high-dose rat studies at exposures well above clinical therapeutic levels. Over 20 years of post-marketing human surveillance — including the Forteo Patient Registry — has documented no increase in osteosarcoma above background rates. The FDA removed the black box warning and the 24-month lifetime use restriction in 2020 (Leder, Curr Osteoporos Rep 2017).
- "Teriparatide can be combined with bisphosphonates for additive benefit" — Randomized trials consistently show that co-administration of bisphosphonates, particularly potent agents such as alendronate, blunts the osteoanabolic response, likely by suppressing the bone resorption component that is required to liberate matrix-bound growth factors and remodel bone architecture. Sequential therapy — teriparatide for the anabolic phase followed by an antiresorptive to consolidate — is the established paradigm.
- "Teriparatide is just an expensive version of other osteoporosis drugs" — Bisphosphonates, denosumab, and SERMs are antiresorptive: they slow bone loss. Teriparatide is anabolic: it stimulates new bone formation by exploiting the paradoxical effect of intermittent versus continuous PTH exposure. The mechanism, the magnitude of BMD gain, and the clinical positioning (severe high-risk osteoporosis, treatment failure of antiresorptives) are fundamentally different.
- "Stopping teriparatide will keep the bone gains" — BMD gains made on teriparatide are rapidly lost if treatment is stopped without follow-on antiresorptive therapy. Sequential therapy — teriparatide for the anabolic window, then a bisphosphonate or denosumab to consolidate — is what preserves the long-term benefit.
- "Continuous PTH would be even more bone-building" — Continuous PTH exposure is catabolic, not anabolic — it produces the bone loss seen in primary hyperparathyroidism. The intermittent pulsatile pattern is pharmacologically essential to the anabolic effect.
Common questions
Why was there originally a 24-month lifetime limit? The osteoblast-stimulatory effect of teriparatide wanes after 12–18 months (bone formation markers plateau and decline toward baseline), and at high lifetime doses in rats, sustained PTH1R activation promoted osteosarcoma. The 24-month limit reflected precautionary regulatory policy. The FDA removed it in 2020 after more than two decades of negative human post-marketing surveillance (Leder, Curr Osteoporos Rep 2017).
Why is teriparatide particularly useful for glucocorticoid-induced osteoporosis? Glucocorticoid-induced bone loss is driven largely by osteoblast suppression — glucocorticoids increase osteoblast programmed cell death and inhibit differentiation. Antiresorptive drugs cannot restore suppressed bone formation. Teriparatide's primary mechanism of stimulating osteoblast number and activity is mechanistically suited to GIO, and clinical trial data confirm its superiority to alendronate in this setting.
How is teriparatide different from abaloparatide? Abaloparatide is a synthetic analog of PTHrP(1-34) rather than PTH(1-34). It shows greater selectivity for the RG conformation of PTH1R, producing more pronounced cortical BMD gains with less transient hypercalcemia and without the modest cortical bone loss at the distal radius seen with teriparatide. Head-to-head fracture outcome comparisons between the two are limited; both are approved anabolic agents for high-fracture-risk osteoporosis (Hattersley and colleagues, Endocrinology 2016; Cosman and colleagues, Mayo Clin Proc 2017).
Known effects
- Vertebral fracture risk reduction in postmenopausal osteoporosis — FDA-approved; ~65% relative risk reduction over 18 months (Neer and colleagues, NEJM 2001)
- Non-vertebral fragility fracture risk reduction — FDA-approved; ~53% relative risk reduction over 18 months
- Lumbar spine BMD increase — +9.7% at 18 months (20 µg dose), up to ~13% over 24 months
- Osteoporosis in men — FDA-approved indication; fracture benefit confirmed in clinical trial
- Glucocorticoid-induced osteoporosis — FDA-approved; superior to alendronate for vertebral fractures in head-to-head trial
- Trabecular bone microarchitecture improvement — documented by biopsy and high-resolution peripheral quantitative CT data
Safety signals
Hypercalcemia and hypercalciuria occur in a small proportion of patients; calcium and vitamin D supplementation is routinely recommended alongside treatment; renal stones are a relative contraindication. Orthostatic hypotension is possible within the first four hours of injection, is transient, and is self-limiting — the first injection is typically given with the patient sitting or lying down. Osteosarcoma carries a precautionary black box warning in the original prescribing information, based on rat carcinogenicity data; no osteosarcoma excess above background has been identified in human post-marketing surveillance over more than 20 years, and the FDA removed the black box warning in 2020. Common injection-related complaints include nausea, leg cramps, and dizziness. A modest decrease in BMD at cortical-rich sites (distal radius) is a characteristic pharmacological effect, reversed on discontinuation or antiresorptive therapy. Anti-teriparatide antibodies develop in approximately 3% of patients and have not been associated with reduced efficacy or safety signals. Labeled contraindications include Paget's disease of bone, prior radiation therapy to the skeleton, elevated serum alkaline phosphatase of unknown etiology (all associated with baseline-elevated osteosarcoma risk), pre-existing hypercalcemia, pre-existing hyperparathyroidism, and skeletal malignancy (Leder, Curr Osteoporos Rep 2017).
Regulatory status
- US: FDA-approved November 26, 2002 (Forteo, Eli Lilly) for postmenopausal osteoporosis at high fracture risk, primary or hypogonadal osteoporosis in men, and glucocorticoid-induced osteoporosis. Biosimilar: Bonsity (Radius Health), FDA-approved May 2019.
- EU: EMA-approved June 2003 (Forsteo, Eli Lilly). Biosimilar Terrosa (Gedeon Richter) approved 2017.
- Japan: Approved (Forteo, Eli Lilly).
- WADA: Prohibited under S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics).
Related peptides
See also: IGF-1 LR3
Mechanism
Teriparatide is the 34-residue N-terminal fragment of human PTH (sequence: SVSEIQLMHNLGKHLNSMERVEWLRKKLQDVHNF). The C-terminal residues of native 84-residue full-length PTH are not required for PTH1R activation; PTH(1-34) is fully equipotent to PTH(1-84) at PTH1R.
PTH1R is a class B (secretin family) GPCR. Two major conformational states are relevant to the pharmacology:
- R0 (G-protein-uncoupled): produces prolonged cAMP signaling via β-arrestin-mediated endosomal signaling
- RG (G-protein-coupled): produces a rapid cell-surface cAMP transient
PTH(1-34) activates both R0 and RG conformations. Downstream signaling via Gαs → adenylyl cyclase → cAMP → PKA engages: (1) CREB phosphorylation → RANKL expression, driving coupled resorption; (2) Runx2 activation → osteoblast differentiation; (3) sclerostin suppression → Wnt pathway disinhibition → further osteoblast stimulation; (4) Bcl-2 upregulation → reduced osteoblast apoptosis → sustained osteoblast number. The structural and signaling distinctions between teriparatide, abaloparatide, and long-acting PTH analogs at PTH1R have been characterized in receptor pharmacology studies (Sutkeviciute and colleagues, Trends Endocrinol Metab 2019; Sato and colleagues, JBMR Plus 2021).
The intermittent-vs-continuous pharmacology distinction is central: intermittent pulsatile teriparatide favors the anabolic response because transient receptor activation preferentially activates the Wnt/sclerostin pathway and reduces osteoblast apoptosis. Continuous PTH exposure — as in primary hyperparathyroidism — chronically elevates RANKL, sustains osteoclast activation, and produces net bone resorption.
The anabolic window: Bone formation markers (serum PINP, osteocalcin) rise within days of starting teriparatide; bone resorption markers (CTX) are delayed by four to six weeks. This early formation-dominant window provides the maximal therapeutic benefit and peaks at 6–12 months, declining thereafter (Leder, Curr Osteoporos Rep 2017).
Open questions
- Whether a second course of teriparatide after a drug holiday provides meaningful fracture benefit, given the documented reduced anabolic response on re-treatment
- Whether combination teriparatide plus denosumab (the DATA regimen) reduces fracture incidence beyond monotherapy — the superior BMD gains observed have not yet been confirmed in a powered fracture-endpoint trial
- The cellular basis for the waning anabolic response after 12–18 months ("osteoblast fatigue") — whether this reflects receptor downregulation, depletion of the osteoblast precursor pool, or increased sclerostin feedback — remains unresolved
- Optimal sequencing relative to abaloparatide and romosozumab in the modern anabolic landscape, where three mechanistically distinct agents are now available; head-to-head sequencing trials are limited (Leder, Curr Osteoporos Rep 2017)
Research directions for this peptide, selected from the current sources — hypotheses you can explore and model. None of it is proven yet; tap any one to see the full thinking.
Could replacing a few amino acid building blocks make teriparatide resist the body's protein-cutting enzymes and last longer between injections?
If true, patients might switch from daily to less frequent injections, which tends to improve how reliably people take their medication. The specific residue positions named here need correction, and the dosing gains are speculative.
Could teriparatide work partly by making one bone cell release a signal that activates nearby bone-forming cells?
If true, researchers could try to target the relay molecule directly, possibly enabling simpler therapies. This is one proposed pathway among several and is not established.
Could the bone-building drug used for osteoporosis also slow cartilage damage in osteoarthritis?
If true, an already-approved drug might be tested to slow joint damage, shortening development time. This is an early hypothesis; the receptor's role in adult cartilage repair is unproven.
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.8609719276428223 | openfold3-mlx |
| ranking score | 0.9853513836860657 | openfold3-mlx |
▸structural qualityopenfold3
| metric | value | note |
|---|---|---|
| gpde | 0.820 | global PDE — lower = better |
| disorder | 0.329 | ! high disorder |
| chain pair ipTM (A, B) | 0.861 | interface quality |
▸3-letter notation
▸recipeopenfold3-mlx 0.3.1
| parameter | value |
|---|---|
| model | openfold3-mlx 0.3.1 |
| weights | aedd8f3eb814e392… |
| hardware | apple_m4_base_16gb |
| mlx version | 0.31.1 |
| python | 3.14.3 |
| random seed | 42 |
| msa strategy | colabfold |
| diffusion samples | 1 |
| runtime | 1163s |
| predicted by | mlx@peptide |
| predicted at | 2026-04-24 |
python3 openfold3/run_openfold.py predict --query_json {query.json} --runner_yaml examples/example_runner_yamls/mlx_runner.yml --output_dir {output_dir} --num_diffusion_samples 1 ▸citationbibtex
@peptide{pep10663,
sequence = {SVSEIQLMHNLGKHLNSMERVEWLRKKLQDVHNF},
target = {pth1r},
author = {peptidemodel},
year = {2026},
status = {synthesized}
}