What is Palopegteriparatide?
Palopegteriparatide (brand name YORVIPATH, also called TransCon PTH) is a PEGylated long-acting prodrug of teriparatide — recombinant human parathyroid hormone fragment 1-34. It was approved by the FDA on August 12, 2024 as the first and only treatment specifically indicated for adults with chronic hypoparathyroidism.
The molecule consists of teriparatide (PTH 1-34) covalently attached to a 40 kDa branched methoxy-PEG via a TransCon (Transient Conjugation) linker. The linker is a self-cleaving carbamate that hydrolyzes at physiologic pH and temperature, releasing native, unmodified PTH 1-34 at a controlled rate. This converts an inherently short-half-life peptide hormone (~30 minutes) into a once-daily, near-infusional release profile that approximates physiologic PTH replacement.
Mechanism of Action
- Slow release of native PTH(1-34) — the TransCon linker auto-hydrolyzes to release teriparatide at a sustained, predictable rate over 24 hours
- PTH1R agonism — released teriparatide activates the PTH1 receptor on bone and kidney
- Restored calcium and phosphate homeostasis — at a steady-state PTH level, urinary calcium reabsorption normalizes, 1,25-(OH)2-vitamin D synthesis resumes, and intestinal calcium absorption increases
- Replacement of physiologic PTH tone — distinct from intermittent teriparatide injections (which produce supraphysiologic peaks and troughs and are used as anabolic osteoporosis therapy)
In hypoparathyroidism, loss of PTH function leads to chronic hypocalcemia, hyperphosphatemia, and inability to make active vitamin D. Conventional therapy (calcium + active vitamin D) treats only the symptoms and produces hypercalciuria, kidney stones, and renal insufficiency. Palopegteriparatide replaces the missing hormone itself.
Clinical Evidence — PaTHway Phase 3
PaTHway Phase 3 trial (NCT04259255):
- 82 adults with chronic hypoparathyroidism on standard therapy randomized to palopegteriparatide or placebo for 26 weeks
- Composite primary endpoint (normal albumin-corrected serum calcium AND independence from active vitamin D AND ≥50% reduction in calcium supplementation): 79% palopegteriparatide vs 5% placebo (p<0.001)
- 93% of treated patients achieved independence from active vitamin D and oral calcium
Long-term extension PaTH Forward and PaTHway-OLE confirm sustained benefit through ≥3 years.
Approval History
- November 2023 — EMA approval (predates FDA)
- August 12, 2024 — FDA approval for adults with chronic hypoparathyroidism
- December 19, 2024 — Commercial US launch
Distinction from Teriparatide
Palopegteriparatide and teriparatide (Forteo) contain the same active peptide but produce very different pharmacology:
| Drug | Indication | PK Profile | Effect |
|---|---|---|---|
| Teriparatide | Osteoporosis (anabolic) | Daily injection → peaks within 30 min, falls to baseline by 4 hr | Intermittent supraphysiologic PTH → bone formation |
| Palopegteriparatide | Hypoparathyroidism (replacement) | Daily injection → continuous low-level release over 24 hr | Steady physiologic PTH → calcium homeostasis |
The same molecule produces opposite clinical effects depending on the time-concentration profile.
Place in Therapy
Palopegteriparatide is administered as a once-daily subcutaneous injection with patient-titrated dosing based on serum calcium. It transformed the standard of care in chronic hypoparathyroidism from symptomatic management to true hormone replacement.
Safety Profile
The most common adverse events are paresthesia, hypercalcemia, headache, and injection-site reactions. The label carries warnings for hypercalcemia (during dose titration), hypocalcemia (during dose interruption), and orthostatic hypotension. The boxed warning for osteosarcoma carried by daily teriparatide does not apply to palopegteriparatide, because the steady-state low-level PTH exposure differs fundamentally from intermittent supraphysiologic dosing.