PTH(1-84) and Yorvipath

Natpara (PTH 1-84) was the first FDA-approved treatment for hypoparathyroidism — a real hormone-replacement drug, distinct from the PTH-fragment drugs teriparatide/abaloparatide already on this site, that was ultimately discontinued over an unfixable manufacturing defect rather than a safety or efficacy failure, and has since been succeeded by a re-engineered replacement, Yorvipath.

Replacement, not stimulation

Natpara was recombinant, full-length human parathyroid hormone — PTH(1-84), biologically identical to the hormone your parathyroid glands normally make. That's a fundamentally different clinical rationale from this site's teriparatide and abaloparatide pages, both PTH fragments/analogs given to people with normal PTH levels specifically to pharmacologically stimulate bone formation for osteoporosis. Natpara instead replaced a hormone that's genuinely deficient in hypoparathyroidism (most often after neck surgery, or from autoimmune destruction of the parathyroid glands), restoring calcium and phosphate balance rather than driving bone growth in someone who doesn't need more PTH signal.

Natpara's approval and pivotal trial

The FDA approved Natpara on 23 January 2015 — the first approved therapy for hypoparathyroidism — based on the REPLACE trial (Mannstadt et al., Lancet Diabetes Endocrinol 2013, PMID 24622413): 134 patients, and a real, clean result — 53% of the PTH(1-84) group achieved a 50%-or-greater reduction in their calcium/calcitriol supplement dose while keeping serum calcium in the target range, versus 2% on placebo.

Why Natpara was discontinued

On 5 September 2019, Takeda recalled all Natpara lots after finding that rubber particulate from the injection cartridge's septum could detach into the drug solution after repeated needle punctures over the cartridge's 14-day use period — the FDA classified it a Class I recall. This was a device/manufacturing defect, not a finding against the drug molecule itself; the risk was under-dosing from a clogged needle in a hormone-replacement context, not a toxicity signal. A limited Special Use Program kept supplying existing patients, but after Takeda couldn't engineer a fix, it announced in October 2022 that it would discontinue manufacturing Natpara entirely by the end of 2024.

Yorvipath: a re-engineered successor

Yorvipath (palopegteriparatide) was approved 9 August 2024 as the successor therapy for the same patient population — but it isn't simply "Natpara, fixed." It's a structurally different molecule: a PEGylated prodrug of PTH(1-34), the same peptide fragment class as teriparatide rather than full-length PTH(1-84), engineered (via Ascendis's TransCon conjugation technology) to release active hormone at a controlled, steady rate over 24 hours from a single daily injection — aiming for more continuous, physiologic PTH exposure than either Natpara's once-daily bolus or teriparatide's own dosing pattern would give. Approval rested on the Phase 2 PaTH Forward and Phase 3 PaTHway trial programs.