PaTH Forward: A Randomized, Double-Blind, Placebo-Controlled Phase 2 Trial of TransCon PTH in Adult Hypoparathyroidism.

CONTEXT: Hypoparathyroidism is characterized by insufficient levels of parathyroid hormone (PTH). TransCon PTH is an investigational long-acting prodrug of PTH(1-34) for the treatment of hypoparathyroidism. OBJECTIVE: This work aimed to investigate the safety, tolerability, and efficacy of daily TransCon PTH in adults with hypoparathyroidism. METHODS: This phase 2, randomized, double-blind, placebo-controlled 4-week trial with open-label extension enrolled 59 individuals with hypoparathyroidism. Interventions included TransCon PTH 15, 18, or 21 µg PTH(1-34)/day or placebo for 4 weeks, followed by a 22-week extension during which TransCon PTH dose was titrated (6-60 µg PTH[1-34]/day). RESULTS: By Week 26, 91% of participants treated with TransCon PTH achieved independence from standard of care (SoC, defined as active vitamin D = 0 µg/day and calcium [Ca] ≤ 500 mg/day). Mean 24-hour urine Ca (uCa) decreased from a baseline mean of 415 mg/24h to 178 mg/24h by Week 26 (n = 44) while normal serum Ca (sCa) was maintained and serum phosphate and serum calcium-phosphate product fell within the normal range. By Week 26, mean scores on the generic 36-Item Short Form Health Survey domains increased from below normal at baseline to within the normal range. The Hypoparathyroidism Patient Experience Scale symptom and impact scores improved through 26 weeks. TransCon PTH was well tolerated with no treatment-related serious or severe adverse events. CONCLUSION: TransCon PTH enabled independence from oral active vitamin D and reduced Ca supplements (≤ 500 mg/day) for most participants, achieving normal sCa, serum phosphate, uCa, serum calcium-phosphate product, and demonstrating improved health-related quality of life. These results support TransCon PTH as a potential hormone replacement therapy for adults with hypoparathyroidism.

Psychometric validation of the Hypoparathyroidism Patient Experience Scales (HPES).

BACKGROUND: Hypoparathyroidism (HP) is a rare endocrine disorder characterized by absent or inappropriately low levels of circulating parathyroid hormone with associated significant physical and cognitive symptoms. This study evaluated the psychometric properties of the Hypoparathyroidism Patient Experience Scales (HPES), which were developed as disease-specific, patient-reported outcome (PRO) measures to assess the symptoms and impacts associated with HP in adults. METHODS: Data from a non-interventional, observational study (N = 300) and a Phase 2 clinical trial (N = 59) were used in the psychometric evaluation. Observational and trial assessments included: an online validation battery (baseline or screening) and retest (approximately 2 weeks after baseline or screening). In the trial, the primary efficacy endpoint was assessed at week 4 through re-administration of the HPES and validation battery subset. The observational study's larger sample size allowed for evaluation of the HPES descriptive properties, scoring algorithm, test-retest reliability, and construct validity. The trial data examined responsiveness, meaningful within-patient change estimates, and treatment impact on HPES scores. RESULTS: Demographic and self-reported medical characteristics results were similar across the 2 studies. Factor analysis confirmed domains in the HPES-Symptom (n = 2) and HPES-Impact (n = 4). For both measures, total and domain scores demonstrated acceptable reliability and validity for both the observational and trial samples. Internal consistency evidence was strong. Test-retest reliability estimates generally approached the recommended 0.70 threshold. The construct validity correlations with other PRO measures were mainly as hypothesized, thus supporting the HPES scores and constructs. Mean scores for both measures also differed as anticipated and significantly across known-groups, thus providing evidence for the scores discriminating between meaningful groups. Trial results supported both HPES total and domain scores' ability to detect change. The difference in mean total and domain scores for both measures demonstrated statistically significant improvements for TransCon PTH compared to placebo treated subjects despite the small sample and a short 4-week duration on fixed, non-optimized doses. CONCLUSIONS: The HPES were found to be conceptually sound with adequate evidence supporting their reliability and validity. Incorporation of the HPES into clinical and research settings will help to further elucidate and assess the patient experience of living with HP and identify treatment differences.

A Randomized Double-Blind Placebo-Controlled First-In-Human Phase 1 Trial of TransCon PTH in Healthy Adults.

TransCon PTH is a sustained-release, essentially inactive prodrug transiently bound to an inert carrier, designed to release PTH(1-34), and in development for hypoparathyroidism (HP). This phase 1, randomized, placebo-controlled, single and multiple ascending dose (SAD and MAD, respectively) trial evaluated safety, tolerability, pharmacodynamics (PD), and pharmacokinetics (PK) of TransCon PTH in healthy adults. SAD and MAD cohorts consisted of 10 subjects (eight active, two placebo) who received up to seven single or six multiple ascending doses of TransCon PTH, respectively. TransCon PTH doses ranged from 3.5 to 124 µg PTH(1-34) for the SAD cohorts and 3.5 to 24 µg PTH(1-34)/day for the MAD cohorts. The primary PK endpoint was Free PTH. The PD endpoints included albumin adjusted serum calcium (sCa), fractional excretion of calcium (FECa), intact endogenous PTH(1-84), bone turnover markers, renal tubular maximum reabsorption of phosphate/glomerular filtration rate (TMP/GFR), serum phosphate (sP) and magnesium, and 1,25 dihydroxyvitamin D. TransCon PTH was generally well tolerated; there were no drug-related serious adverse events (SAEs), and all AEs were transient in nature. Free PTH demonstrated an effective half-life of approximately 60 hours and a dose-dependent, sustained exposure with an infusion-like profile within the calculated physiologic range for active PTH at steady-state. Albumin-adjusted sCa demonstrated a dose-dependent, sustained response with complete control of FECa despite modest hypercalcemia at higher doses. Renal tubular maximum reabsorption of phosphate/glomerular filtration rate (TMP/GFR) showed a dose-dependent decrease, resulting in a dose-dependent decrease in sP. TransCon PTH administered daily for 10 days showed no increase in the osteoblastic bone formation markers, serum bone-specific alkaline phosphatase (BSAP) or P1NP, or the osteoclastic bone resorption marker, urine NTx, but modestly and transiently increased the osteoclast marker, serum CTx. These phase 1 data support TransCon PTH as a daily replacement therapy for HP providing physiological levels of PTH 24 hours per day and advancement into phase 2 clinical development. © 2020 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.