Ascendis Pharma has reported one-year data showing sustained improvement from its ongoing Phase III PaTHway Trial of TransCon PTH (palopegteriparatide), once-daily hormone replacement therapy, in adults with hypoparathyroidism.

This comes after the recent rejection of TransCon PTH by the US Food and Drug Administration (FDA), with the FDA citing concerns regarding the manufacturing control strategy for the variability of delivered doses in the TransCon PTH drug/device combination product.

The data from the randomised, placebo-controlled Phase III trial (NCT04701203) was presented at the annual meeting of the Endocrine Society (ENDO 2023) in Chicago, US.

Ascendis first reported the data from the Phase III trial in March 2022.

TransCon PTH is designed as a long-acting prodrug of the parathyroid hormone and is intended to provide replacement therapy for hypoparathyroidism.

Hypoparathyroidism is a rare disease where the parathyroid gland fails to produce adequate amounts of parathyroid hormone, or the parathyroid hormone produced is not biologically active. The disease is characterised by abnormally low calcium (hypocalcemia) and high phosphorus (hyperphosphatemia) levels in the blood.

Therefore, conventional treatments include calcium supplements and activated vitamin D.

The FDA has approved recombinant human parathyroid hormone for patients with chronic hypoparathyroidism who are uncontrolled with conventional therapy, in accordance with National Organization for Rare Disorders (NORD).

TransCon PTH’s one-year data

The one-year (52-week) data is from the 156-week open-label extension (OLE) with TransCon PTH, an arm of the Phase III PaTHway Trial of TransCon PTH.

The 52-week results consist of a 26-week randomised period, with participants either on TransCon PTH or placebo, followed by 26 weeks of OLE with TransCon PTH.

Of the 82 study participants dosed at the start of the study, 79 completed the randomised period and entered the OLE, with 78 of these completing 52 weeks on TransCon PTH.

Of the 78 patients in the OLE, 74 achieved independence from conventional therapy, with no participant requiring active vitamin D supplements.

At week 52, 81% of the participants had normal serum calcium. Mean albumin-adjusted serum calcium levels of 8.9mg/dL were maintained through week 52 (normal range: 8.3mg/dL–10.6mg/dL).

TransCon PTH was well-tolerated in the extension period, with no new safety signals or trial discontinuations due to therapy.

Ascendis began enrolment in a German early access programme for TransCon PTH in June 2023. The company also expects to launch TransCon PTH in Germany following a possible positive decision on the marketing authorisation by the European Commission for TransCon PTH in the fourth quarter of 2023.