PTH(1-34) prodrug · hypoparathyroidism
A long-acting form of parathyroid hormone for adults with hypoparathyroidism, a condition in which the parathyroid glands make too little hormone to keep blood calcium normal. It is teriparatide, the active front portion of the hormone, attached to a large polyethylene glycol carrier, and it is injected under the skin with a prefilled pen.
Parathyroid hormone keeps blood calcium in range by releasing calcium from bone, helping the kidneys hold on to calcium while clearing phosphate, and activating vitamin D so the gut absorbs more calcium1. In palopegteriparatide, the hormone fragment PTH(1-34) is linked to an inert, branched polyethylene glycol carrier through a linker that slowly cleaves itself under normal body conditions. This releases PTH(1-34) gradually, giving continuous exposure across the day instead of a brief spike; the apparent half-life of the released hormone is about 60 hours1. After release, it acts on the same PTH1 receptor as the body's own hormone, which is plentiful on bone cells and kidney tubule cells1.
The main evidence is PaTHway, a 26-week phase 3 trial in 84 adults with chronic hypoparathyroidism who were also taking standard calcium and active vitamin D. On the drug, 79% met a combined goal of normal blood calcium while no longer needing active vitamin D or therapeutic calcium supplements, versus 5% on placebo; it also improved scores on a hypoparathyroidism symptom and functioning scale and brought average 24-hour urine calcium into the normal range2. The FDA label, scoring the 82 analyzed participants with stricter criteria, reports 69% versus 5% at week 261.
In the open-label extension, about two-thirds of those first assigned to the drug kept normal calcium without conventional therapy at weeks 52 and 78 when further titration was allowed1. Most adverse events in PaTHway were mild or moderate, and no withdrawals were attributed to the drug2.
FDA-approved in August 2024 as Yorvipath (Ascendis Pharma) for hypoparathyroidism in adults; it was not studied in acute hypoparathyroidism right after neck surgery1. The European Commission authorised it in November 20233.
Per the FDA label, the most common reactions were injection-site reactions, dizziness or palpitations from blood-vessel widening, headache, diarrhea, back pain, high blood calcium and throat pain. Warnings cover serious high or low blood calcium, so calcium is checked periodically; allergic reactions including anaphylaxis; low blood pressure on standing; digoxin toxicity if calcium rises; and a possible osteosarcoma risk, so it is not recommended for people at higher risk of that bone cancer1.
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