TransCon PTH kidney function gains hold for up to five years in pooled trial data

Ascendis Pharma says TransCon PTH kidney function gains held for up to five years in adults with hypoparathyroidism. In a pooled post hoc analysis of 139 treated people from two trials, average estimated glomerular filtration rate, or eGFR, rose by 9.6 mL/min/1.73 m2 by week 52 and then stayed level. The poster was shown on 26 October at Kidney Week 2026, the American Society of Nephrology meeting. The drug, palopegteriparatide, is already approved as Yorvipath in the US and the EU, so the data add detail rather than a new stage.

How the TransCon PTH kidney function analysis was built

The analysis pools the phase 2 PaTH Forward trial and the phase 3 PaTHway trial, which together enrolled 141 adults. Of those, 139 received at least one dose and form the analysis group, and 129 reached the final trial visit. Each trial opened with a blinded placebo controlled period, four weeks in PaTH Forward and 26 weeks in PaTHway, followed by open label extensions that ran to week 266 and week 182. To enter, people needed an eGFR of at least 30, and the group average at baseline was 69 with a standard deviation of 17. The pooling was done after the fact, as a post hoc analysis, and the poster was presented by Elvira Gosmanova, a nephrologist at Albany Medical College.

Kidneys are a natural place to look. Parathyroid hormone is the main regulator of calcium and phosphate, and people who lack it have long been treated with active vitamin D and calcium tablets that lift blood calcium without replacing the hormone itself. That approach can push calcium into the urine, and kidney complications are among the long term problems the company lists for the disease. Palopegteriparatide is a prodrug of the active fragment of the hormone, given once a day and designed to release it steadily around the clock. It belongs with the other hormone pathway molecules on our site, which replace or steer a missing hormone signal.

eGFR rose in the first year and then held steady

Mean eGFR rose by 7.2 mL/min/1.73 m2 from baseline to week 26 and by 9.6 to week 52, and the company reports that the change was statistically significant from week 26 to the end of the trials. At week 52, 68.9 percent of people had gained at least 5 points of eGFR, and 49.6 percent had gained more than 10. After that, the curve flattened: the mean slope from week 52 to week 266 was 0.28 per year, which Ascendis describes as stable. The company contrasts this with the gradual decline in eGFR usually seen as adults age, citing a 2024 paper in BMJ Open, but the release does not give a reference rate.

At week 52, 68.9 percent of people had gained at least 5 points of eGFR, and 49.6 percent had gained more than 10.

Other measures moved in the same direction. Average 24 hour urine calcium fell from 396 milligrams a day at baseline to 206 at week 26 and 170 at week 52, and the company says the improvement lasted to the end of the trials. At the final visits, mean blood calcium was 8.9 milligrams per decilitre, and 88 percent of people had albumin adjusted blood calcium in the normal range. Most had stopped conventional therapy: 98 percent were free of active vitamin D and 95 percent were free of therapeutic calcium doses. Ascendis said the drug was generally well tolerated, with no new safety signals, and most treatment emergent adverse events were grade 1 or 2. People who started below an eGFR of 60 gained numerically more, but no figures were released.

Limits of a post hoc open label look

Several features of the design limit what the TransCon PTH kidney function data can prove. The analysis was not planned in advance, so it may pick up patterns that a prespecified test would not confirm. The placebo periods ended at week 4 and week 26, which means the long tail out to five years has no control group: there is no way to say from these data how the same people would have fared on conventional therapy. Ten of the 139 treated people did not reach the final visit, and the release does not describe them. Because the trials required an eGFR of at least 30, the results say nothing about people with more advanced kidney disease.

There is also the question of what eGFR measures. It is an estimate calculated from a blood test, usually creatinine, rather than a direct measurement of filtration, and the release does not explain the mechanism behind the early rise. A poster at a congress is not a peer reviewed paper, and the Ascendis release on the poster is the main public account so far. Aimee Shu, the company's chief medical officer, said the improvements "underscore the unique ability of TransCon PTH to replicate the systemic and balanced actions of endogenous PTH across multiple target organ systems." That is the company's reading. An independent analysis with a comparison group would test it more firmly than pooled single arm follow up can.

Where Yorvipath stands and what comes next

Palopegteriparatide is approved as Yorvipath in the United States, the European Union, the European Economic Area and other jurisdictions for adults with hypoparathyroidism, according to Ascendis. On our board, this readout leaves the molecule where it is, in the approved column, with the signal set to up. The data do not change the label or the indication. What they add is a five year view of a safety concern that matters in this disease: whether replacing the hormone protects the kidneys, or at least does not harm them. For an approved drug, that kind of long term reassurance often matters more to prescribers than a fresh efficacy number, but it does not replace a controlled trial.

The next checkpoints are about evidence quality rather than stage. A full paper on the pooled kidney analysis would allow readers to check the dropouts and the subgroup below an eGFR of 60. Ascendis has not said whether it plans to ask regulators to reflect the kidney data in the label, and we will not assume it. Longer real world data from patients treated outside trials would also help, as would any study that compares the drug with conventional therapy over years rather than weeks. Readers can see how this molecule sits against others on the pipeline board, which we update when a confirmed regulatory or trial event changes a stage.

Conclusion

The TransCon PTH kidney function data show eGFR rising by about 10 points in the first year and then holding for up to five years, alongside lower urine calcium and little need for conventional therapy. The analysis is post hoc and lacks a long term control group. Yorvipath stays approved; the next useful step is a peer reviewed paper with dropout and subgroup detail. This story is research news, not medical advice.