Extended Treatment With Recombinant Human Parathyroid Hormone (1-84) in Adult Patients With Chronic Hypoparathyroidism.

OBJECTIVE: Recombinant human parathyroid hormone (1-84) (rhPTH[1-84]) is efficacious in patients with hypoparathyroidism but additional data supporting its prolonged use are needed. We evaluated whether efficacy, safety, and tolerability are maintained during long-term rhPTH(1-84) treatment of patients with chronic hypoparathyroidism. METHODS: This was a phase 4, single-center, open-label, single-arm, 3-year extension (NCT02910466) of the phase 3 Hypo Extended (HEXT) study (NCT01199614). Patients self-administered rhPTH(1-84) once daily by subcutaneous injection, with doses individualized based on clinical parameters. Albumin-adjusted serum calcium levels (primary outcome measure), other disease biomarkers, health-related quality of life, and safety of rhPTH(1-84) were assessed using descriptive statistics. RESULTS: All patients (n = 39) had been exposed to rhPTH(1-84) (mean exposure [SD] 8.5 [3.5] years) before the start of the study, resulting in a mean exposure of 10.8 years including the present study. Mean patient age was 51.9 years, 79.5% were female, and 97.4% were White. Mean albumin-adjusted serum calcium concentrations were within the target range, and mean serum phosphate, serum calcium-phosphate product, and 24-hour urinary calcium excretion levels were within reference ranges at end of treatment. Mean doses of supplemental calcium and active vitamin D were maintained throughout the study. Bone turnover marker levels were maintained from baseline to end of treatment. No clinically relevant changes in bone mineral density were observed. Patient-reported health-related quality-of-life scores were generally maintained throughout the study. Four adverse events were considered treatment related and no new safety signals were identified. CONCLUSION: The effects of rhPTH(1-84) on biochemical, skeletal, and health-related quality-of-life parameters did not wane with extended use.

Five-Year Estimated Glomerular Filtration Rate in Adults with Chronic Hypoparathyroidism Treated with rhPTH(1-84): A Retrospective Cohort Study.

INTRODUCTION: Chronic hypoparathyroidism is associated with higher risk of developing chronic kidney disease compared with the general population. This study evaluated changes in estimated glomerular filtration rate (eGFR) over a 5-year period in adult patients with chronic hypoparathyroidism treated with recombinant parathyroid hormone (1-84), rhPTH(1-84), compared with a historical control cohort of patients who did not receive rhPTH(1-84). METHODS: This retrospective cohort study included patients with chronic hypoparathyroidism treated with rhPTH(1-84) in the REPLACE (NCT00732615), RELAY (NCT01268098), RACE (NCT01297309), and HEXT (NCT01199614 and continuation study NCT02910466) clinical trials. A historical control cohort who did not receive parathyroid hormone but who had enrollment criteria similar to those for the clinical trials was selected from the IBM® Explorys electronic medical record database (January 2007-August 2019). Outcomes of interest were the annual rate of change in eGFR from baseline (i.e., eGFR slope) and the predicted eGFR change from baseline at years 1 through 5. RESULTS: The study comprised 72 adult patients with chronic hypoparathyroidism treated with rhPTH(1-84) and 176 control patients who did not receive rhPTH(1-84). Over 5 years, eGFR remained stable in the rhPTH(1-84) cohort, whereas eGFR declined at a rate of 1.67 mL/min/1.73 m2 per year in the control cohort (P < 0.001 for eGFR slope in the control cohort). At 5 years, predicted eGFR in the rhPTH(1-84) cohort increased from baseline by 1.21 mL/min/1.73 m2, whereas eGFR in the control cohort declined by 10.36 mL/min/1.73 m2, after adjusting for baseline variables. The difference in eGFR slopes between the cohorts over 5 years was 1.37 mL/min/1.73 m2 per year (95% CI 0.62-2.13; P < 0.001). CONCLUSION: Long-term treatment with rhPTH(1-84) was associated with stable eGFR compared with eGFR decline in the controls not treated with rhPTH(1-84). Preservation of renal function conferred by rhPTH(1-84) may benefit patients with chronic hypoparathyroidism by reducing risk of long-term renal complications.

Lower Risk of Cardiovascular Events in Adult Patients with Chronic Hypoparathyroidism Treated with rhPTH(1-84): A Retrospective Cohort Study.

INTRODUCTION: Patients with chronic hypoparathyroidism are at increased risk of cardiovascular disease. This study evaluated the risk of developing cardiovascular conditions over a period of 5 years in adult patients with chronic hypoparathyroidism treated with recombinant human parathyroid hormone (1-84), rhPTH(1-84), compared with a historical control cohort of patients not treated with rhPTH(1-84). METHODS: This retrospective cohort study comprised patients with chronic hypoparathyroidism treated with rhPTH(1-84) in the REPLACE (NCT00732615), RELAY (NCT01268098), and RACE (NCT01297309) clinical trials, and controls selected from the IBM® Explorys electronic medical record database (January 2007-August 2019) who did not receive parathyroid hormone but who had enrollment criteria similar to those for the clinical trials. Cardiovascular outcomes were the first diagnosis of cerebrovascular, coronary artery, peripheral vascular disease, or heart failure during the study period. RESULTS: We evaluated 113 adult patients with chronic hypoparathyroidism treated with rhPTH(1-84) and 618 control patients who did not receive rhPTH(1-84). Over the 5-year follow-up period, 3.5% of patients (n = 4) in the rhPTH(1-84) cohort had a cardiovascular event compared with 16.3% (n = 101) in the control cohort. Kaplan-Meier analysis demonstrated that patients in the rhPTH(1-84) cohort had lower risk of experiencing a cardiovascular event compared with patients in the control cohort (P = 0.005). Multivariable analyses adjusted for baseline variables showed that patients in the rhPTH(1-84) cohort had 75% lower risk for a cardiovascular event compared with patients in the control cohort (adjusted hazard ratio, 0.25 [95% CI 0.08-0.81]; P = 0.020). CONCLUSION: Long-term treatment with rhPTH(1-84) was associated with a lower risk of incident cardiovascular conditions compared with conventional therapy in patients with chronic hypoparathyroidism. Previous studies demonstrated that mineral homeostasis was maintained with lower use of calcium and active vitamin D when rhPTH(1-84) was added to conventional therapy. Future studies are needed to understand whether improved regulation of mineral homeostasis conferred by rhPTH(1-84) may provide long-term cardiovascular benefits to patients with chronic hypoparathyroidism.

Multicenter retro-prospective observational study on chronic hypoparathyroidism and rhPTH (1-84) treatment.

PURPOSE: The main purpose of this study was to investigate the effects of 12 months of rhPTH (1-84) (Natpar®) treatment in a cohort of patients selected according to the indications of hypoparathyroidism guidelines. The use of recombinant human PTH (1-84) [rhPTH (1-84)] is approved as hormonal replacement therapy in patients with hypoparathyroidism not adequately controlled with conventional therapy. METHODS: It is a multicenter, observational, retro-prospective, open label study. Eleven Italian Endocrinological centers, members of Hypoparathyroidism Working Group of the Italian Society of Endocrinology (HypoparaNET) were involved. Main outcome measures were serum and urinary calcium and phosphate concentration, calcium-phosphate product, renal function, oral calcium and vitamin D doses, and clinical manifestations. RESULTS: Fourteen adult subjects, affected by chronic hypoparathyroidism, were treated with rhPTH (1-84) for 12 months. At 12 months of rhPTH (1-84) treatment, 61.5% of patients discontinued calcium supplement and 69.2% calcitriol. Mean albumin-adjusted total serum calcium levels quickly normalized after initiation of rhPTH (1-84) treatment compared to baseline (p = 0.009), remaining in the normal range until 12 months. Rare hypo-hypercalcemia episodes were reported. Renal function was maintained normal and no renal complications were reported. Serum and urinary phosphate and urinary calcium were maintained in the normal range. Mean phosphatemia levels linearly decreased from 3 months up to 12 months compared to baseline (p = 0.014). No severe adverse events were described. CONCLUSIONS: Biochemical and clinical results confirm the efficacy and safety of rhPTH (1-84) therapy, which represents an important option for hypoparathyroid patients unresponsive to conventional therapy.

The PARADIGHM (physicians advancing disease knowledge in hypoparathyroidism) registry for patients with chronic hypoparathyroidism: study protocol and interim baseline patient characteristics.

BACKGROUND: The PARADIGHM registry of adult and pediatric patients with chronic hypoparathyroidism evaluates the long-term safety and effectiveness of treatment with recombinant human parathyroid hormone, rhPTH(1-84), and describes the clinical disease course under conditions of routine clinical practice. In this first report, we detail the registry protocol and describe the baseline characteristics of two adult patient cohorts from an interim database analysis. One cohort after study entry were prescribed rhPTH(1-84), and the other cohort received conventional therapy of calcium and active vitamin D. METHODS: An observational study of patients with chronic hypoparathyroidism in North America and Europe, collecting data for ≥10 years per patient. Main outcome measures were baseline patient demographics, clinical characteristics, medications, and disease outcome variables of symptoms, biochemical parameters, and health assessments. Baseline is the enrollment assessment for all variables except biochemical measurements in patients treated with rhPTH(1-84); those measurements were the most recent value before the first rhPTH(1-84) dose. Exclusion criteria applied to the analysis of specified outcomes included pediatric patients, patients who initiated rhPTH(1-84) prior to enrollment, and those who received rhPTH(1-34). Clinically implausible biochemical outlier data were excluded. RESULTS: As of 30 June 2019, data of 737 patients were analyzed from 64 centers; 587 (80%) were women, mean ± SD age 49.1±16.45 years. At enrollment, symptoms reported for patients later prescribed rhPTH(1-84) (n=60) and those who received conventional therapy (n=571), respectively, included fatigue (51.7%, 40.1%), paresthesia (51.7%, 29.6%), muscle twitching (48.3%, 21.9%), and muscle cramping (41.7%, 33.8%). Mean serum total calcium, serum phosphate, creatinine, and estimated glomerular filtration rate were similar between cohorts. Health-related quality of life (HRQoL) 36-item Short Form Health Survey questionnaire scores for those later prescribed rhPTH(1-84) were generally lower than those for patients in the conventional therapy cohort. CONCLUSIONS: At enrollment, based on symptoms and HRQoL, a greater percentage of patients subsequently prescribed rhPTH(1-84) appeared to have an increased burden of disease than those who received conventional therapy despite having normal biochemistry measurements. PARADIGHM will provide valuable real-world insights on the clinical course of hypoparathyroidism in patients treated with rhPTH(1-84) or conventional therapy in routine clinical practice. TRIAL REGISTRATION: EUPAS16927, NCT01922440.

Tratamiento de hipoparatiroidismo con parathormona recombinante humana [rhPTH(1-84)] / Hypoparathyroidism treated with recombinant human parathyroid hormone [rhPTH(1-84)]

El hipoparatiroidismo (hipoPTH) es una enfermedad infrecuente caracterizada por hipocalcemia y niveles inapropiadamente bajos o ausentes de parathormona. Presentamos el caso de un hombre de 25 años, deportista de alto rendimiento, con antecedente de hipoPTH secundario a tiroidectomía total dos años antes por cáncer papilar multifocal bilateral tiroideo, estadificado como T3 N1b M0, derivado por hipocalcemia sintomática. Presentaba calcemias promedio de 7mg%, síntomas de hipocalcemia en reposo y múltiples internaciones. Inicialmente, se optimizó tratamiento convencional con aporte de calcio vía oral hasta 12g/día, vitamina D y calcitriol, sin mejoría clínica ni bioquímica. Se descartaron malabsorción y complicaciones crónicas de hipoPTH. Se evidenció a través de cuestionario de salud SF-36 disminución de la calidad de vida. Se indicó sustitución con parathormona recombinante humana [rhPTH(1-84)] 50μg/día subcutánea con posterior ascenso a 75μg y reducción progresiva de la medicación por vía oral. Actualmente se encuentra asintomático, sin requerimiento de calcio ni vitamina D, mantiene calcemias de 9mg%, realiza actividad deportiva y demuestra marcada mejoría en la calidad de vida según cuestionario SF-36 (36-Item Short Form Health Survey).

Hypoparathyroidism (HypoPT) is a rare disease characterized by low calcium and inappropriately low circulating parathormone levels. We present the case of a 25-year-old high-performance athlete male, with history of HypoPT after total thyroidectomy for papillary thyroid carcinoma (T3 N1b M0) two years before, who was referred to our clinic for symptomatic hypocalcemia. The patient reported serum calcium average levels of 7mg%, presented symptoms of hypocalcemia at rest and had multiple hospital admissions. First, standard treatment was optimized by calcium supplementation up to 12g/d and active vitamin D, not showing clinical or biochemical improvement. Malabsorption and complications of chronic HypoPT were ruled out. The 36-Item Short Form Health Survey (SF-36) demonstrated an impaired quality of life (QoL). Full-length recombinant human parathyroid hormone [rhPTH(1-84)] therapy was started with 50μg/d subcutaneous, and later adjusted to 75μg/d and the oral treatment gradually decreased. Currently, he is asymptomatic, with serum calcium levels above 9mg%, without receiving oral medication. He performs sports activity and shows marked improvement in quality of life according to SF-36 questionnaire.

[Hypoparathyroidism treated with recombinant human parathyroid hormone [rhPTH(1-84)]]. / Tratamiento de hipoparatiroidismo con parathormona recombinante humana [rhPTH(1-84)].

Hypoparathyroidism (HypoPT) is a rare disease characterized by low calcium and inappropriately low circulating parathormone levels. We present the case of a 25-year-old high-performance athlete male, with history of HypoPT after total thyroidectomy for papillary thyroid carcinoma (T3 N1b M0) two years before, who was referred to our clinic for symptomatic hypocalcemia. The patient reported serum calcium average levels of 7mg%, presented symptoms of hypocalcemia at rest and had multiple hospital admissions. First, standard treatment was optimized by calcium supplementation up to 12g/d and active vitamin D, not showing clinical or biochemical improvement. Malabsorption and complications of chronic HypoPT were ruled out. The 36-Item Short Form Health Survey (SF-36) demonstrated an impaired quality of life (QoL). Full-length recombinant human parathyroid hormone [rhPTH(1-84)] therapy was started with 50υg/d subcutaneous, and later adjusted to 75υg/d and the oral treatment gradually decreased. Currently, he is asymptomatic, with serum calcium levels above 9mg%, without receiving oral medication. He performs sports activity and shows marked improvement in quality of life according to SF-36 questionnaire.

El hipoparatiroidismo (hipoPTH) es una enfermedad infrecuente caracterizada por hipocalcemia y niveles inapropiadamente bajos o ausentes de parathormona. Presentamos el caso de un hombre de 25 años, deportista de alto rendimiento, con antecedente de hipoPTH secundario a tiroidectomía total dos años antes por cáncer papilar multifocal bilateral tiroideo, estadificado como T3 N1b M0, derivado por hipocalcemia sintomática. Presentaba calcemias promedio de 7mg%, síntomas de hipocalcemia en reposo y múltiples internaciones. Inicialmente, se optimizó tratamiento convencional con aporte de calcio vía oral hasta 12g/día, vitamina D y calcitriol, sin mejoría clínica ni bioquímica. Se descartaron malabsorción y complicaciones crónicas de hipoPTH. Se evidenció a través de cuestionario de salud SF-36 disminución de la calidad de vida. Se indicó sustitución con parathormona recombinante humana [rhPTH(1-84)] 50υg/día subcutánea con posterior ascenso a 75υg y reducción progresiva de la medicación por vía oral. Actualmente se encuentra asintomático, sin requerimiento de calcio ni vitamina D, mantiene calcemias de 9mg%, realiza actividad deportiva y demuestra marcada mejoría en la calidad de vida según cuestionario SF-36 (36-Item Short Form Health Survey).

PTH and bone material strength in hypoparathyroidism as measured by impact microindentation.

PTH levels might be associated with bone material strength as measured by impact microindentation. Resistance to microfracture is decreased in hypoparathyroidism and appears to be associated with more severe disease and to improve with PTH replacement. INTRODUCTION: PTH is a key regulator of bone structure and remodeling. When PTH is absent in hypoparathyroidism (HypoPT), bone mass is increased and remodeling is decreased. In addition to bone structure and remodeling, bone material properties contribute to fracture resistance. Yet little is known about the relationship between PTH and bone material properties. Impact microindentation provides a clinical assessment of microfracture resistance, measured as the bone material strength index (BMSi). METHODS: Case-control cross-sectional study of PTH levels and in vivo BMSi measurement by impact microindentation at the anterior tibia in HypoPT patients (n = 17) and in controls matched for age, sex, and menopausal status (n = 17), with follow-up in a subgroup of HypoPT patients (n = 5) after recombinant human parathyroid hormone (1-84) [rhPTH(1-84)] treatment. RESULTS: BMSi was positively associated with PTH levels in controls (r = 0.58, p = 0.02) and was 11% lower (p = 0.01) in HypoPT patients as compared with controls. In HypoPT, lower BMSi was associated with a trend toward greater supplemental calcium doses (p = 0.07). BMSi increased after rhPTH(1-84) treatment in the HypoPT patients who underwent repeat microindentation. CONCLUSIONS: PTH levels might be associated with bone material strength, although other factors might be contributory. In HypoPT, resistance to microfracture is decreased and may be associated with greater supplemental calcium doses and might increase with PTH replacement. It remains to be determined whether changes in bone remodeling and microarchitecture contribute to the effects of PTH on microfracture resistance.

Skeletal Manifestations of Hypoparathyroidism.

Chronic PTH deficiency has a marked effect on the skeleton, leading to characteristic decreases in bone remodeling and increases in bone mass. An effect on fracture risk has not been demonstrated, although biochemical, imaging, and histomorphometric data indicate abnormalities in skeletal properties1,21,21,21,2. Replacement with PTH leads to a new skeletal state that is maintained with long-term treatment.

Skeletal Manifestations of Hypoparathyroidism.

Chronic parathyroid hormone (PTH) deficiency has a marked effect on the skeleton, leading to characteristic decreases in bone remodeling and increases in bone mass. Numerous lines of evidence using biochemical, imaging, and histomorphometric methodologies have demonstrated that the skeleton is altered when PTH is absent and that these abnormalities might be reversed with PTH treatment. More evidence is needed to determine whether fracture risk is altered in hypoparathyroidism.

New Directions in Treatment of Hypoparathyroidism.

The history of parathyroid hormone (PTH) replacement therapy for hypoparathyroidism begins in 1929. In 2015, the Food and Drug Administration approved recombinant human PTH(1-84) [rhPTH(1-84)] as a treatment for hypoparathyroidism. Long-term studies of rhPTH(1-84), up to 6 years, have demonstrated continued efficacy of this replacement agent. Approaches to optimize PTH treatment in hypoparathyroidism include subcutaneous pump delivery systems, long-lived carrier molecules, and long-acting PTH analogues that show promise to prolong efficacy. Calcilytic compounds have been explored as a treatment for autosomal dominant hypocalcemia. Calcilytics are negative modulators of the calcium-sensing receptor and may present a therapeutic opportunity to increase endogenous PTH synthesis and secretion.

The Effects of Long-term Administration of rhPTH(1-84) in Hypoparathyroidism by Bone Histomorphometry.

Hypoparathyroidism is a rare disorder that is associated with abnormal bone properties. Recombinant human parathyroid hormone (1-84) [rhPTH(1-84)] in short-term studies has beneficial skeletal effects. Although rhPTH(1-84) will likely be used indefinitely, long-term effects on skeletal microstructure are unknown. We therefore studied histomorphometric changes with transiliac crest bone biopsies before and after 8.3 ± 1 years of rhPTH(1-84) in 13 hypoparathyroid subjects compared with 45 controls. Before institution of rhPTH(1-84), skeletal remodeling indices were markedly suppressed. With long-term treatment, indices of bone remodeling increased. Mineralizing surface increased by 26-fold (0.3 ± 1 to 7.9 ± 7%, p = 0.003), bone formation rate increased by 15-fold (0.003 ± 0.01 to 0.047 ± 0.05 µm2 /µm/day, p = 0.007), osteoid width doubled (1.9 ± 1 to 4.3 ± 1 lamellae, p = 0.017), and osteoid surface tripled (3.3 ± 3 to 10.8 ± 6%, p = 0.011). Bone resorption as measured by eroded surface increased (4.6 ± 2 to 7.5 ± 3%, p = 0.021). Structural changes demonstrated intratrabecular tunneling, with increases in cancellous bone volume (19.6 ± 5 to 29.1 ± 11%, p = 0.017) and trabecular number (1.8 ± 1 to 2.5 ± 1 #/mm, p = 0.025). Cortical porosity tended to increase (6.3 ± 5 to 9.5 ± 3%, p = 0.07). Mineralizing surface, osteoid surface, and eroded surface surpassed control levels, as did cancellous bone volume, trabecular number, and cortical porosity. These data, the first to reflect such long exposure of any PTH for any disease, illustrate that PTH establishes and maintains a new skeletal state for at least 8 years in hypoparathyroidism. © 2018 American Society for Bone and Mineral Research.

Drug safety evaluation of parathyroid hormone for hypocalcemia in patients with hypoparathyroidism.

INTRODUCTION: Hypoparathyroidism is a rare disorder characterized by low serum calcium levels and high serum phosphate levels, and low or inappropriately normal levels of parathyroid hormone (PTH). This disease is commonly treated with calcium supplements and active vitamin D metabolites or analogues, but large doses of these supplements are often utilized to relieve the symptoms caused by hypocalcemia, without guarantee of a physiological normalization of calcium-phosphate homeostasis. Areas covered: Several studies have investigated replacement therapy with recombinant human PTH [rhPTH (1-84) and rhPTH (1-34)] for subjects with hypoparathyroidism. In 2015, The Food and Drug Administration (FDA) approved, in the United States, rhPTH (1-84), named Natpara®, a bioenginerred rhPTH, for the management of chronic hypoparathyroidism not well controlled with conventional therapy. This article evaluates the safety and tolerability of rhPTH (1-84) in patients with chronic hypoparathyroidism, and also describes the studies conducted so far on rhPTH (1-34) used for chronic hypoparathyroidism. Expert opinion: The research done in this field has shown that replacement treatment with rhPTH is an attractive option for subjects with hypoparathyroidism who are unable to maintain stable and safe serum and urinary calcium levels. However, since therapy with rhPTH is a long-term management option in hypoparathyroidism, more long-term safety data are needed.

Effects of parathyroid hormone rhPTH(1-84) on phosphate homeostasis and vitamin D metabolism in hypoparathyroidism: REPLACE phase 3 study.

In hypoparathyroidism, inappropriately low levels of parathyroid hormone lead to unbalanced mineral homeostasis. The objective of this study was to determine the effect of recombinant human parathyroid hormone, rhPTH(1-84), on phosphate and vitamin D metabolite levels in patients with hypoparathyroidism. Following pretreatment optimization of calcium and vitamin D doses, 124 patients in a phase III, 24-week, randomized, double-blind, placebo-controlled study of adults with hypoparathyroidism received subcutaneous injections of placebo or rhPTH(1-84) (50 µg/day, titrated to 75 and then 100 µg/day, to permit reductions in oral calcium and active vitamin D doses while maintaining serum calcium within 2.0-2.2 mmol/L). Predefined endpoints related to phosphate homeostasis and vitamin D metabolism were analyzed. Serum phosphate levels decreased rapidly from the upper normal range and remained lower with rhPTH(1-84) (P < 0.001 vs. placebo). At week 24, serum calcium-phosphate product was lower with rhPTH(1-84) vs. placebo (P < 0.001). rhPTH(1-84) treatment resulted in significant reductions in oral calcium dose compared with placebo (P < 0.001) while maintaining serum calcium. After pretreatment optimization, baseline serum 25-hydroxyvitamin D (25[OH]D) and 1,25-dihydroxyvitamin D (1,25[OH]2D) levels were within the normal range in both groups. After 24 weeks, 1,25(OH)2D levels were unchanged in both treatment groups, despite significantly greater reductions in active vitamin D dose in the rhPTH(1-84) group. In hypoparathyroidism, rhPTH(1-84) reduces serum phosphate levels, improves calcium-phosphate product, and maintains 1,25(OH)2D and serum calcium in the normal range while allowing significant reductions in active vitamin D and oral calcium doses.

Natpara for the treatment of hypoparathyroidism.

INTRODUCTION: Hypoparathyroidism is a rare endocrine disorder characterized by hypocalcaemia and hyperphosphatemia, due to absent or inappropriately low parathyroid hormone levels. For management of chronic hypoparathyroidism, current treatment options involve oral calcium and vitamin D. This standard treatment cannot resolve all problematic aspects of the disease, such as abnormal bone remodeling and reduced quality of life, and is associated with long-term complications, including nephrolithiasis, nephrocalcinosis, renal impairment, cataracts and cerebral calcifications. AREAS COVERED: In 2015, the FDA (Food and Drug Administration) approved rhPTH (1-84), named Natpara®, a bioengineered recombinant human PTH, for the management of hypoparathyroidism of any etiology, except Autosomal Dominant Hypocalcemia, not well controlled with calcium and active vitamin D. Herein, the authors review its chemistry, pharmacodynamics, pharmacokinetics and clinical efficacy for hypoparathyroidism. EXPERT OPINION: Replacement therapy with rhPTH (1-84) is a fundamental step in the treatment of chronic hypoparathyroidism in cases not well controlled by standard therapy, providing the natural hormone that is lacking for the maintenance of normal calcium levels, and reducing long-term risks associated with conventional therapy. Nevertheless, given the chronic nature of the disease, in the future, further studies will have to be performed to evaluate long-term efficacy and safety of the drug.

Hypoparathyroidism - disease update and emerging treatments.

Parathyroid hormone (PTH) is the primary regulator of blood calcium levels and bone metabolism. Insufficient levels of PTH lead to hypoparathyroidism, characterized by low serum calcium and elevated serum phosphate levels. It is most commonly caused by the inadvertent damage to the parathyroid glands during thyroid surgery. Patients with hypoparathyroidism are currently being treated with oral calcium and active vitamin D, and to avoid worsening hypercalciuria, target serum calcium levels are within the lower end of normal. With current treatment, patients may suffer from large swings in serum calcium and are at a substantial risk of chronic renal failure, nephrocalcinosis, and kidney stones. The recent FDA approval of recombinant human (rh) PTH(1-84) for the treatment of hypoparathyroidism adds PTH replacement therapy to the endocrinologist's armamentarium to treat this chronic disease.

Pharmacokinetics and pharmacodynamics of subcutaneous recombinant parathyroid hormone (1-84) in patients with hypoparathyroidism: an open-label, single-dose, phase I study.

BACKGROUND: Impaired mineral homeostasis affecting calcium, phosphate, and magnesium is a result of parathyroid hormone (PTH) deficiency in hypoparathyroidism. The current standard of treatment with active vitamin D and oral calcium does not control levels of these major minerals. Recombinant full-length human PTH 1-84 (rhPTH[1-84]) is being developed for the treatment of hypoparathyroidism. OBJECTIVE: The goal of this study was to investigate the pharmacokinetics and pharmacodynamics of a single subcutaneous injection of rhPTH(1-84) in patients with hypoparathyroidism. METHODS: This was an open-label, dose-escalating study of single subcutaneous administration of 50 µg and then 100 µg of rhPTH(1-84). Enrolled patients (age range, 25-85 years) had ≥12 months of diagnosed hypoparathyroidism defined according to biochemical evidence of hypocalcemia with concomitant low-serum intact PTH and were taking doses ≥1000 mg/d of oral calcium and ≥0.25 µg/d of active vitamin D (oral calcitriol). The patient's prescribed dose of calcitriol was taken the day preceding but not on the day of or during the 24 hours after rhPTH(1-84) administration. Each patient received a single 50-µg rhPTH(1-84) dose, had at least a 7-day washout interval, and then received a single 100-µg rhPTH(1-84) dose. The following parameters were assessed: plasma PTH; serum and urine total calcium, magnesium, phosphate, and creatinine; and urine cyclic adenosine monophosphate. RESULTS: After administration of rhPTH(1-84) 50 µg (n = 6) and 100 µg (n = 7), the approximate t½ was 2.5 to 3 hours. Plasma PTH levels increased rapidly, then declined gradually back to predose levels at ~12 hours. The median AUC was similar with calcitriol and rhPTH(1-84) for serum 1,25-dihydroxyvitamin D (calcitriol, 123-227 pg · h/mL; rhPTH[1-84], 101-276 pg · h/mL), calcium (calcitriol, 3.3-3.7 mg · h/dL; rhPTH[1-84], 3.3-7.6 mg · h/dL), and magnesium (calcitriol, 0.7-0.9 mg · h/dL; rhPTH[1-84], 1.3-2.8 mg · h/dL). In contrast, the median AUC for phosphate was strongly negative with rhPTH(1-84) (calcitriol, -1.0 to 0.8 mg · h/dL; rhPTH[1-84], -21.3 to -26.5 mg · h/dL). Compared with calcitriol, rhPTH(1-84) 50 µg reduced 24-hour calcium excretion and calcium-to-creatinine ratios by 12% and 23%, respectively, and rhPTH(1-84) 100 µg reduced them by 26% and 27%. There was little overall impact on urine magnesium levels. Compared with calcitriol, rhPTH(1-84) 50 µg increased urinary phosphate excretion and phosphate-to-creatinine ratios by 53% and 54%, respectively, and rhPTH(1-84) 100 µg increased them by 45% and 42%. Urine cyclic adenosine monophosphate-to-creatinine ratio increased with rhPTH(1-84) by 2.3-fold (50 µg) and 4.4-fold (100 µg) compared with calcitriol. CONCLUSIONS: PTH replacement therapy with rhPTH(1-84) regulated mineral homeostasis of calcium, magnesium, phosphate, and vitamin D metabolism toward normal in these study patients with hypoparathyroidism.

Effect of Sequential Therapy with Incadronate after Withdrawal of Recombinant Human Parathyroid Hormone(1-84) on Bone Quantity and Quality in Ovariectomized Rats / 대한내분비학회지

BACKGROUND: Human parathyroid hormone(hPTH) is a promising anabolic agent. However, since hPTH (1-34) is available only via injection, and has a critical side effect of causing bone tumors during life-long administration in the rat, it would be practical to use PTH for the shortest possible duration to obtain the maximal effect. In addition, acquired bone mass due to hPTH tend to decrease after drug cessation. To determine the effectiveness of the osteoporosis-reversing concept of lose, restore, and maintain(LRM), recombinant human PTH(1-84)[rhPTH(1-84)] and the respective anti-resorptive agents were sequentially studied. METHODS: Thirty six, 20-week-old, Sprague-Dawley rats were used in this study. Treatment was started on the 25th week after an ovariectomy, which had been performed at 20weeks of age, with 5weeks of rhPTH (1-84) 100(microgram/kg/d), 5days/wk, followed by the respective sequential therapies for 5 weeks as follows: 1) Ovariectomized rats(OVX, n=6), 2) Sham operated rats(SHAM, n=6), 3) OVX rats with PTH maintenance(PTH-M, n=6), 4) OVX rats treated with PTH then withdrawn(PTH-W, n=6), 5) PTH-treated OVX rats then treated with 17beta-estradiol(PTH-E, 10microgram/d, SQ, 5days/wk, n=6), 6) PTH-treated OVX rats then treated with incadronate(PTH-I, 3mg/kg, per os 5 days/wk, n=6). The bone mineral density(BMD) of the right femurs was measured using dual X-ray absorptiometry(DXA). Microcomputed tomography(microCT) was used to measure the structural parameters of the 2nd lumbar vertebrae. A three-point bending test of the femur and compressive tests of vertebrae were also performed. RESULTS: Bone quantity data showed that the femoral BMD was significantly higher in the PTH-M and PTH-I groups than in the OVX and PTH-W groups(P<0.05). Measurement of the cortical thickness revealed that only the PTH-M group had a significant increase(P=0.001). The ultimate force(Fu) at the midshaft of the femur was stronger in the PTH-M group than in the OVX group(P<0.001). However, no significant difference was found among the treated groups. CONCLUSION: PTH withdrawal resulted in the loss of the acquired BMD, but sequential therapy with the anti-resorptive, incadronate, prevented further bone loss. The use of incadronate after rhPTH(1-84), as a sequential regimen, was significantly effective on the maintenance in the bone mass, but further clarification in the improvement in the bone quality is needed.