Ninety-five percent of patients who enrolled in a trial five years ago are still in it. That completion rate, reported Wednesday for the Phase 2 PaTH Forward Trial of TransCon PTH (palopegteriparatide), is itself a signal worth examining before getting to the efficacy numbers. Dropout in chronic disease trials is often where long-term data quietly collapse. Here, 56 of the original 59 adults with hypoparathyroidism reached Week 266, and the clinical picture they presented was largely intact.
The headline efficacy number is an 82% response rate on a demanding multi-component endpoint requiring normal serum calcium, no active vitamin D, and calcium supplementation below 600 mg per day. More granularly, 96% achieved independence from active vitamin D and 95% from therapeutic calcium doses. Those figures reflect what the trial was actually designed to test: whether a once-daily prodrug of PTH(1-34) can restore hormone physiology broadly rather than simply patch serum calcium levels. The kidney data reinforce that ambition. Mean eGFR improved by 9.4 mL/min/1.73 m² from baseline and held that gain through five years, a meaningful finding given that conventional management with high-dose active vitamin D and calcium tends to worsen renal function over time. Quality-of-life scores measured by both the HPES and SF-36 normalized early and stayed in the normative range, and bone mineral density Z-scores corrected from elevated baseline levels without overcorrecting below zero.
The safety profile over this duration draws no new flags. Treatment-emergent adverse events were mostly mild or moderate, no discontinuations were drug-related, and only one patient developed transient, low-titer, non-neutralizing anti-PTH antibodies with no clinical consequence. That antibody finding matters because immunogenicity is a recurring concern with peptide-based hormonal replacements. Five years of clean data on that front strengthens the case for durable use. YORVIPATH received FDA approval for adult hypoparathyroidism in August 2024, and Natpara, the prior PTH-based option, has been effectively off the market due to manufacturing and recall issues, leaving the practical landscape narrow for patients whose disease is inadequately managed on calcium and calcitriol alone.
This is Phase 2 data, 59 patients, and without a concurrent control arm in the open-label extension the eGFR trajectory cannot be formally compared against an untreated population. The number to track from here is whether the Phase 3 PaTHway trial, which enrolled a larger population in a controlled 26-week design followed by its own extension, replicates this kidney function signal at scale. That is where the renal benefit either becomes a regulatory and clinical cornerstone or gets reclassified as a Phase 2 artifact.
Jon Napitupulu is Director of Media Relations at The Clinical Trial Vanguard. Jon, a computer data scientist, focuses on the latest clinical trial industry news and trends.
