Safety and Efficacy of PTH 1-34 and 1-84 Therapy in Chronic Hypoparathyroidism: A Meta-Analysis of Prospective Trials.

Hypoparathyroidism is the only endocrine deficiency for which hormone replacement therapy is not the standard of care. Although conventional treatments may control hypocalcaemia, other complications such as hyperphosphatemia, kidney stones, peripheral calcifications, and bone disease remain unmet needs. This meta-analysis (PROSPERO registration number CRD42019126881) aims to evaluate and compare the efficacy and safety of PTH1-34 and PTH1-84 in restoring calcium metabolism in chronic hypoparathyroidism. EMBASE, PubMed, and CENTRAL databases were searched for randomized clinical trials or prospective studies published between January 1996 and March 2021. English-language trials reporting data on replacement with PTH1-34 or PTH1-84 in chronic hypoparathyroidism were selected. Three authors extracted outcomes, one author performed quality control, all assessed the risk of biases. Overall, data from 25 studies on 588 patients were analyzed. PTH therapy had a neutral effect on calcium levels, while lowering serum phosphate (-0.21 mmol/L; 95% confidence interval [CI], -0.31 to -0.11 mmol/L; p < 0.001) and urinary calcium excretion (-1.21 mmol/24 h; 95% CI, -2.03 to -0.41 mmol/24 h; p = 0.003). Calcium phosphate product decreased under PTH1-84 therapy only. Both treatments enabled a significant reduction in calcium and calcitriol supplementation. PTH therapy increased bone turnover markers and lumbar spine mineral density. Quality of life improved and there was no difference in the safety profile between PTH and conventionally treated patients. Results for most outcomes were similar for the two treatments. Limitations of the study included considerable population overlap between the reports, incomplete data, and heterogeneity in the protocol design. In conclusion, the meta-analysis of data from the largest collection to date of hypoparathyroid patients shows that PTH therapy is safe, well-tolerated, and effective in normalizing serum phosphate and urinary calcium excretion, as well as enabling a reduction in calcium and vitamin D use and improving quality of life. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

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.

Safety and Efficacy of Oral Human Parathyroid Hormone (1-34) in Hypoparathyroidism: An Open-Label Study.

The standard treatment of primary hypoparathyroidism (hypoPT) with oral calcium supplementation and calcitriol (or an analog), intended to control hypocalcemia and hyperphosphatemia and avoid hypercalciuria, remains challenging for both patients and clinicians. In 2015, human parathyroid hormone (hPTH) (1-84) administered as a daily subcutaneous injection was approved as an adjunctive treatment in patients who cannot be well controlled on the standard treatments alone. This open-label study aimed to assess the safety and efficacy of an oral hPTH(1-34) formulation as an adjunct to standard treatment in adult subjects with hypoparathyroidism. Oral hPTH(1-34) tablets (0.75 mg human hPTH(1-34) acetate) were administered four times daily for 16 consecutive weeks, and changes in calcium supplementation and alfacalcidol use, albumin-adjusted serum calcium (ACa), serum phosphate, urinary calcium excretion, and quality of life throughout the study were monitored. Of the 19 enrolled subjects, 15 completed the trial per protocol. A median 42% reduction from baseline in exogenous calcium dose was recorded (p = .001), whereas median serum ACa levels remained above the lower target ACa levels for hypoPT patients (>7.5 mg/dL) throughout the study. Median serum phosphate levels rapidly decreased (23%, p = .0003) 2 hours after the first dose and were maintained within the normal range for the duration of the study. A notable, but not statistically significant, median decrease (21%, p = .07) in 24-hour urine calcium excretion was observed between the first and last treatment days. Only four possible drug-related, non-serious adverse events were reported over the 16-week study, all by the same patient. A small but statistically significant increase from baseline quality of life (5%, p = .03) was reported by the end of the treatment period. Oral hPTH(1-34) treatment was generally safe and well tolerated and allowed for a reduction in exogenous calcium supplementation, while maintaining normocalcemia in adult patients with hypoparathyroidism. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Therapy of Hypoparathyroidism With rhPTH(1-84): A Prospective, 8-Year Investigation of Efficacy and Safety.

CONTEXT: Conventional treatment of hypoparathyroidism is associated with decreased renal function and increased bone mineral density (BMD). OBJECTIVE: To evaluate the effects of 8 years of recombinant human parathyroid hormone (1-84) [rhPTH(1-84)] therapy on key biochemical and densitometric indices. DESIGN: Prospective open-label trial. SETTING: Tertiary medical center. PARTICIPANTS: Twenty-four subjects with hypoparathyroidism. INTERVENTION: Treatment with rhPTH(1-84) for 8 years. MAIN OUTCOME MEASURES: Supplemental calcium and vitamin D requirements, serum calcium and phosphorus levels, calcium-phosphate product, urinary calcium excretion, estimated glomerular filtration rate (eGFR) and BMD. RESULTS: PTH therapy was associated with progressive reduction in supplemental calcium (57%; P < 0.01) and active vitamin D (76%; P < 0.001) requirements over 8 years. Serum calcium concentration was stable; urinary calcium excretion declined 38% (P < 0.01). eGFR remained stable and was related to baseline eGFR and serum calcium levels. Calcium-phosphate product was below the recommended limit; serum phosphorus remained within normal range. Lumbar spine and total hip BMD increased, peaking at 4 (mean ± SE, 4.6% ± 1.5%; P = 0.01) and 8 years (2.6% ± 1.1%; P = 0.02), whereas femoral neck BMD did not change and one-third radius BMD decreased (mean ± SE, -3.5% ± 1.1%; P = 0.001). BMD at all sites was higher throughout the 8 years than in the age- and sex-matched reference population. Hypercalcemia and hypocalcemia were uncommon. CONCLUSION: rhPTH(1-84) is a safe and effective treatment for hypoparathyroidism for 8 years. Long-term reductions in supplemental requirements and biochemical improvements with stable renal function are maintained.

Safety and Efficacy of Recombinant Human Parathyroid Hormone in Adults With Hypoparathyroidism Randomly Assigned to Receive Fixed 25-µg or 50-µg Daily Doses.

PURPOSE: The present study examined the efficacy and safety of a lower rhPTH(1-84) dose. METHODS: RELAY was a dose-blinded, multicenter, 8-week study of patients with hypoparathyroidism randomized to fixed 25- or 50-µg/d doses of subcutaneous rhPTH(1-84). The primary end point was the percentage of patients at week 8 with supplement reductions in calcium to ≤500 mg/d and in calcitriol to ≤0.25 µg/d, while maintaining serum calcium levels between 1.875 mmol/L and the upper limit of normal. The secondary end point was the percentage of patients at week 8 with a ≥50% reduction in calcium and calcitriol doses, while maintaining serum calcium levels between 1.875 mmol/L and the upper limit of normal. FINDINGS: Forty-two patients were randomized (25-µg group, n = 19; 50-µg group, n = 23). At week 8, the primary end point was achieved by 4 (21%; 95% CI, 6%-46%) and 6 (26%; 95% CI, 10%-48%) of the patients receiving 25 and 50 µg/d of rhPTH(1-84), respectively. The secondary end point was achieved by 2 (11%; 95% CI, 1%-33%) and 6 (26%; 95% CI, 10%-48%) of the patients receiving 25 and 50 µg/d of rhPTH(1-84), respectively. Treatment-emergent adverse events were reported by 11 (58%) patients in the 25-µg group and 17 (74%) patients in the 50-µg group. IMPLICATIONS: Doses as low as 25 µg/d of rhPTH(1-84) are well tolerated and may be effective for a subset of patients. ClinicalTrials.gov identifier: NCT01268098.

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.

Therapy of Hypoparathyroidism With PTH(1-84): A Prospective Six Year Investigation of Efficacy and Safety.

CONTEXT: Human recombinant (rh)PTH(1-84) was recently approved for the treatment of refractory hypoparathyroidism, based upon a short-term phase 3 clinical trial. Long-term data are needed, because no time limit was placed on the treatment period. OBJECTIVE: We studied the effect of long-term rhPTH(1-84) treatment in hypoparathyroidism for up to 6 years. DESIGN: Prospective open-label study. SETTING: Referral center. PATIENTS: A total of 33 subjects with hypoparathyroidism. INTERVENTIONS: rhPTH(1-84) treatment was initiated at a starting dose of 100 µg every other day for 6 years. Due to the availability of new dosages during the 6-year time period of the study, the dose could be and was adjusted for most patients to a daily dosing regimen. MAIN OUTCOME MEASURES: Supplemental calcium and vitamin D requirements, serum and urinary calcium (monthly for 6 mo and then biannually), serum phosphorus, bone turnover markers, and bone mineral density (BMD) biannually. RESULTS: Treatment with rhPTH(1-84) progressively reduced supplemental calcium requirements over 6 years by 53% (P < .0001) and 1,25-dihydroxyvitamin D requirements by 67% (P < .0001). Sixteen subjects (48%) were able to eliminate 1,25-dihydroxyvitamin D supplementation completely. Serum calcium concentration remained stable, and urinary calcium excretion fell. Lumbar spine BMD increased (3.8 ± 1%, P = .004) as did total hip BMD (2.4 ± 1%, P = .02), whereas femoral neck BMD remained stable and the distal one third radius decreased (-4.4 ±1%, P < .0001). Bone turnover markers increased significantly, reaching a 3-fold peak above baseline values at 1 year and subsequently declining but remaining higher than pretreatment values. Hypercalcemia was uncommon (12 episodes over 6 y; 2.5% of all values). CONCLUSIONS: Long-term, continuous therapy of hypoparathyroidism for 6 years with rhPTH(1-84) is associated with reductions in supplemental calcium and calcitriol requirements, stable serum calcium concentration, and reduced urinary calcium excretion. The safety profile remains good. These data represent the longest experience with the therapeutic use of PTH for any condition and demonstrate its long-term efficacy and safety in hypoparathyroidism.

Bisphosphonates, vitamin D, parathyroid hormone, and osteonecrosis of the jaw. Could there be a missing link?

BACKGROUND: It is estimated that over 190 million bisphosphonates have been prescribed worldwide. But this drug can produce adverse effects, of which osteonecrosis of the jaw and severe hypocalcemia are the most serious. It is evident that bisphosphonate administration affects multiple and diverse biochemical mediators related to bone metabolism. MATERIAL AND METHODS: This review of literature investigates four basic parameters in patients treated with bisphosphonates - parathyroid hormone (PTH), bisphosphonates, vitamin D, calcium, and jaw osteonecrosis - which are fundamental for assessing bone metabolism and so the efficacy and correct use of the drug. The imbalances generated by vitamin D and calcium deficiencies, together with their multiple systemic repercussions, have been widely researched but the outcomes of these imbalances in relation to bisphosphonate administration are not well known, and some research has indicated that they may be associated with osteonecrosis of the jaw (ONJ). RESULTS: The present review set out to explain the functioning of bone metabolism, the importance of different chemical mediators, the imbalances produced by incorrect use of this drug, in order to forewarn against the possible relation of these parameters with ONJ, whose physiopathology remains unknown. CONCLUSIONS: Medical and dental clinics should keep detailed anamneses of the use of vitamin D and calcium supplements, as it is of vital importance to maintain their correct levels in blood, given that these are related to ONJ as well as other adverse effects; this procedure is also necessary in order to ensure the correct use of the drug.

Efficacy and safety of recombinant human parathyroid hormone (1-84) in hypoparathyroidism (REPLACE): a double-blind, placebo-controlled, randomised, phase 3 study.

BACKGROUND: Hypoparathyroidism results in impaired mineral homoeostasis, including hypocalcaemia and hyperphosphataemia. Treatment with high-dose oral calcium and active vitamin D does not provide adequate or consistent control of biochemical indices and can lead to serious long-term complications. We aimed to test the efficacy, safety, and tolerability of once-daily recombinant human parathyroid hormone 1-84 (rhPTH[1-84]) in adults with hypoparathyroidism. METHODS: In this double-blind, placebo-controlled, randomised phase 3 study (REPLACE), we recruited patients with hypoparathyroidism (≥ 18 months duration) aged 18-85 years from 33 sites in eight countries. After an optimisation period, during which calcium and active vitamin D doses were adjusted to achieve consistent albumin-corrected serum calcium, patients were randomly assigned (2:1) via an interactive voice response system to 50 µg per day of rhPTH(1-84) or placebo for 24 weeks. Active vitamin D and calcium were progressively reduced, while rhPTH(1-84) could be titrated up from 50 µg to 75 µg and then 100 µg (weeks 0-5). The primary endpoint was the proportion of patients at week 24 who achieved a 50% or greater reduction from baseline in their daily dose of oral calcium and active vitamin D while maintaining a serum calcium concentration greater than or the same as baseline concentrations and less than or equal to the upper limit of normal, analysed by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00732615. FINDINGS: Between June 23, 2009, and Feb 28, 2011, 134 eligible patients were recruited and randomly assigned to rhPTH(1-84) (n=90) or placebo (n=44). Six patients in the rhPTH(1-84) group and seven in the placebo group discontinued before study end. 48 (53%) patients in the rhPTH(1-84) group achieved the primary endpoint compared with one (2%) patient in the placebo group (percentage difference 51.1%, 95% CI 39.9-62.3; p<0.0001). The proportions of patients who had at least one adverse event were similar between groups (84 [93%] patients in the rhPTH[1-84] group vs 44 [100%] patients in the placebo group), with hypocalcaemia, muscle spasm, paraesthesias, headache, and nausea being the most common adverse events. The proportions of patients with serious adverse events were also similar between the rhPTH(1-84) group (ten [11%] patients) and the placebo group (four [9%] patients). INTERPRETATION: 50 µg, 75 µg, or 100 µg per day of rhPTH(1-84), administered subcutaneously in the outpatient setting, is efficacious and well tolerated as a PTH replacement therapy for patients with hypoparathyroidism.

Therapy of hypoparathyroidism with PTH(1-84): a prospective four-year investigation of efficacy and safety.

CONTEXT: PTH may be an effective treatment option for hypoparathyroidism, but long-term data are not available. OBJECTIVE: We studied the effect of 4 yr of PTH(1-84) treatment in hypoparathyroidism. DESIGN: Twenty-seven subjects were treated with PTH(1-84) for 4 yr, with prospective monitoring of calcium and vitamin D requirements, serum and urinary calcium, serum phosphorus, bone turnover markers, and bone mineral density (BMD). RESULTS: Treatment with PTH(1-84) reduced supplemental calcium requirements by 37% (P = 0.006) and 1,25-dihydroxyvitamin D requirements by 45% (P = 0.008). Seven subjects (26%) were able to stop 1,25-dihydroxyvitamin D completely. Serum calcium concentration remained stable, and urinary calcium and phosphorus excretion fell. Lumbar spine BMD increased by 5.5 ± 9% at 4 yr (P < 0.0001). Femoral neck and total hip BMD remained stable. At 4 yr, distal radius BMD was not different from baseline. Bone turnover markers increased significantly, reaching a 3-fold peak from baseline values at 6-12 months (P < 0.05 for all), subsequently declining to steady-state levels at 30 months. Hypercalcemia was uncommon (11 episodes in eight subjects over 4 yr; 1.9% of all values), with most episodes occurring within the first 6 months and resolving with adjustment of supplemental calcium and vitamin D. CONCLUSIONS: PTH(1-84) treatment of hypoparathyroidism for up to 4 yr maintains the serum calcium concentration, while significantly reducing supplemental calcium and 1,25-dihydroxyvitamin D requirements. Lumbar spine BMD increases without significant changes at other sites. These data provide support for the safety and efficacy of PTH(1-84) therapy in hypoparathyroidism for up to 4 yr.

The US postmarketing surveillance study of adult osteosarcoma and teriparatide: study design and findings from the first 7 years.

The Osteosarcoma Surveillance Study, an ongoing 15-year surveillance study initiated in 2003, is a postmarketing commitment to the United States (US) Food and Drug Administration to evaluate a potential association between teriparatide, rhPTH(1-34), a recombinant human parathyroid hormone analog (self-injectable medication to treat osteoporosis), and development of osteosarcoma in response to a finding from preclinical (animal) studies. Incident cases of primary osteosarcoma diagnosed in adults (aged ≥40 years) on or after January 1, 2003, are identified through population-based state, regional, and comprehensive cancer center registries in the US. Information on possible prior treatment with teriparatide, on demographics, and on risk factors is ascertained by patient or proxy telephone interview after patient consent. Between June 2004 and September 30, 2011, 1448 cases (diagnosed 2003 to 2009) were identified by participating cancer registries (estimated to be 62% of all adult cases in the US for that time period); 549 patients or proxies were interviewed. Interviewed patients were similar to noninterviewed patients with regard to mean age, sex, race, and geographical distribution and tumor type and site of tumor. Mean age of those interviewed was 61 years, 46% were female, 86% were white, and 77% were alive when the case was reported to the study investigators. Data collected in the study provide descriptive information on a large number of adults with osteosarcoma, an uncommon malignant bone tumor. After 7 years of the study, there were no osteosarcoma patients who had a prior history of teriparatide treatment. Thus, approximately halfway through this 15-year study, the study has not detected a pattern indicative of a causal association between teriparatide treatment and osteosarcoma in humans.

The effect of adding PTH(1-84) to conventional treatment of hypoparathyroidism: a randomized, placebo-controlled study.

In hypoparathyroidism, plasma parathyroid hormone (PTH) levels are inadequate to maintain plasma calcium concentration within the reference range. On conventional treatment with calcium supplements and active vitamin D analogues, bone turnover is abnormally low, and BMD is markedly increased. We aimed to study the effects of PTH-replacement therapy (PTH-RT) on calcium-phosphate homeostasis and BMD. In a double-blind design, we randomized 62 patients with hypoparathyroidism to daily treatment with PTH(1-84) 100 µg or similar placebo for 24 weeks as add-on therapy to conventional treatment. Compared with placebo, patients on PTH(1-84) reduced their daily dose of calcium and active vitamin D significantly by 75% and 73%, respectively, without developing hypocalcemia. However, hypercalcemia occurred frequently during the downtitration of calcium and active vitamin D. Plasma phosphate and renal calcium and phosphate excretion did not change. Compared with placebo, PTH(1-84) treatment significantly increased plasma levels of bone-specific alkaline phosphatase (+226% ± 36%), osteocalcin (+807% ± 186%), N-terminal propeptide of procollagen 1 (P1NP; +1315% ± 330%), cross-linked C-telopeptide of type 1 collagen (CTX; +1209% ± 459%), and urinary cross-linked N-telopeptide of type 1 collagen (NTX; (+830% ± 165%), whereas BMD decreased at the hip (-1.59% ± 0.57%), lumbar spine (-1.76% ± 1.03%), and whole body (-1.26% ± 0.49%) but not at the forearm. In conclusion, the need for calcium and active vitamin D is reduced significantly during PTH-RT, whereas plasma calcium and phosphate levels are maintained within the physiologic range. In contrast to the effect of PTH(1-84) treatment in patients with osteoporosis, PTH-RT in hypoparathyroidism causes a decrease in BMD. This is most likely due to the marked increased bone turnover. Accordingly, PTH-RT counteracts the state of overmineralized bone and, during long-term treatment, may cause a more physiologic bone metabolism.

Long-term treatment of 12 children with chronic hypoparathyroidism: a randomized trial comparing synthetic human parathyroid hormone 1-34 versus calcitriol and calcium.

CONTEXT: Hypoparathyroidism is among the few hormonal insufficiency states not treated with replacement of the missing hormone. This is the first randomized controlled study in children comparing treatment with synthetic human PTH 1-34 and calcitriol. OBJECTIVE: The primary objective was to assess the efficacy and safety of long-term PTH 1-34 vs. calcitriol treatment in the maintenance of normal serum calcium values and renal calcium excretion in children with hypoparathyroidism. SETTING: The study was conducted at a clinical research center. SUBJECTS: Subjects included 12 children aged 5-14 yr with chronic hypoparathyroidism and without severe renal or hepatic insufficiency. STUDY DESIGN: The study was a 3-yr randomized parallel trial comparing twice-daily calcitriol (plus calcium and cholecalciferol in four daily doses) vs. s.c. PTH 1-34 treatment, with weekly or biweekly monitoring of serum and urine calcium. RESULTS: Mean predose serum calcium levels were maintained at, or just below, the normal range, and urine calcium levels remained in the normal range throughout the 3-yr study, with no significant differences between treatment groups. Creatinine clearance, corrected for body surface area, did not differ between groups and remained normal throughout the study. Markers of bone turnover were mildly elevated during PTH 1-34 therapy and remained within the normal range during calcitriol therapy. Mean bone mineral density Z-scores at the anterior-posterior lumbar spine, femoral neck, distal radius, and whole body remained within the normal range and did not differ between groups throughout the study. Similarly, height and weight percentiles did not differ between treatment groups and remained normal throughout the 3-yr follow-up. CONCLUSION: We conclude that PTH 1-34 therapy is safe and effective in maintaining stable calcium homeostasis in children with hypoparathyroidism. Additionally, PTH 1-34 treatment allowed normal skeletal development because there were no differences in bone mineral accrual, linear growth, or weight gain between the two treatment arms over the 3-yr study period.

ZT-031, a cyclized analog of parathyroid hormone(1-31) for the potential treatment of osteoporosis.

ZT-031 is a cyclic 31-amino acid analog of parathyroid hormone (PTH) that is in development by Zelos Therapeutics Inc for the treatment of osteoporosis and other bone-related disorders. ZT-031 activates the PTH type 1 receptor - the molecular target of the currently marketed osteogenic peptides PTH and PTH(1-34). Daily subcutaneous injections of ZT-031 prevented bone loss and replaced bone that had already been lost in an ovariectomized rat model of osteoporosis. Daily subcutaneous injections of ZT-031 in gonad-intact monkeys increased bone mineral density (BMD) at cortical and cancellous bone sites and increased serum levels of bone formation markers. The daily subcutaneous administration of ZT-031 to postmenopausal women with osteoporosis elicited a dose-dependent increase in BMD of the lumbar spine, proximal femur and total hip area. Plasma levels of bone formation markers were significantly increased above baseline after 1 month of dosing, and prior to increases in bone resorption markers. ZT-031 was demonstrated to be safe and well tolerated; episodes of hypercalcemia were infrequent and observed with a frequency greater than with placebo only at the highest doses tested for the drug. Although available data are limited, the results obtained following treatment with ZT-031 have generally been at least as favorable as those obtained with other osteogenic PTH peptides. A novel dosing paradigm has been planned for the drug.

Full length parathyroid hormone (1-84) in the treatment of osteoporosis in postmenopausal women.

OBJECTIVE: To review the pharmacological properties and the available clinical data of full length parathyroid hormone (PTH) in post-menopausal osteoporosis. SOURCES: A MEDLINE search was completed, together with a review of information obtained from the manufacturer and from the medicine regulatory agencies. STUDY AND DATA SELECTION: Studies were selected according to relevance and availability. Relevant information (design, objectives, patients' characteristics, outcomes, adverse events, dosing, etc) was analyzed. RESULTS: Different studies have shown that, when administered intermittently as a subcutaneous injection in the abdomen, PTH increases bone mineral density (BMD) and prevents vertebral fractures. On completion of PTH therapy (up to 24 months), there is evidence that sequential treatment with alendronate is associated with a therapeutic benefit in terms of increase in BMD. Further trials are necessary to determine long-term safety and the role of PTH in combination with other treatments for osteoporosis and the effect of repeated cycles of PTH followed by an anti-catabolic agent. There are currently no completed comparative trials with other osteoporosis treatments. CONCLUSIONS: Full length PTH, given intermittently as an abdominal subcutaneous injection, appears to be a safe and efficacious treatment option for high risk osteoporosis. More data are needed to determine its specific role in osteoporosis treatment.

Enhancement of fracture healing with parathyroid hormone: preclinical studies and potential clinical applications.

Parathyroid hormone (PTH) has become the most widely studied hormone with regard to its administration to various species and their respective skeletal responses. Beyond its affirmative effect in osteoporosis treatment, systemic PTH administration seems to stimulate bone formation in the fracture healing process. According to preclinical experimental studies, once-daily administration of PTH enhances the morphometric and mechanical properties of fracture calluses and accelerates the normal fracture healing. Its anabolic effect is obvious even in low doses, as well as in cases of implant fixation and distraction osteogenesis. There is little evidence of toxic effects and there are only a few reports of adverse events related to its use. The incidence of bone neoplasms in animal studies depends on the dose and duration of treatment. However, it is not prognostic of an equivalent risk potential of carcinogenesis in humans. In summary, the clinical promise of parathyroid hormone is very high and a positive effect in fracture healing should be anticipated.

Elevations in serum and urinary calcium with parathyroid hormone (1-84) with and without alendronate for osteoporosis.

CONTEXT: The effect of PTH therapy on serum and urinary calcium levels and the risk of hypercalcemia or hypercalciuria has not been formally evaluated. OBJECTIVE: The objective was to examine changes in serum and urinary calcium associated with PTH(1-84) therapy in the PaTH trial and the extent to which a defined algorithm resolved the elevated values. DESIGN, SETTING, PARTICIPANTS, AND INTERVENTION: A total of 178 postmenopausal women were randomized to PTH(1-84) either alone or in combination with alendronate during the first year of the PaTH study. MAIN OUTCOME MEASURE(S): The main outcome measures were fasting serum calcium at baseline and 1, 3, and 12 months and 24-h urinary calcium at baseline and 3 months. RESULTS: In 14% of participants, serum calcium more than 10.5 mg/dl (>2.6 mmol/liter) developed. Following the defined algorithm, 58% of elevated measurements were normal on repeat testing; 38% required discontinuation of calcium and vitamin D supplementation, and one necessitated a decrease in PTH injection frequency to normalize serum calcium. One participant developed transient hypercalcemia between study visits and required hospitalization; the episode resolved with iv hydration and PTH discontinuation. Baseline characteristics associated with the development of hypercalcemia were serum calcium [relative hazards = 1.9 per 0.5 mg/dl (0.12 mmol/liter); 95% confidence interval = 1.1-3.2] and serum 1,25-dihydroxyvitamin D [relative hazard = 1.9 per 10 pg/ml (26 pmol/liter); 95% confidence interval = 1.2-3.1]. Fifteen women (8%) developed hypercalciuria [urinary calcium > 400 mg (100 mmol)/24 h or calcium/creatinine ratio > 0.4]; 80% of cases resolved after discontinuing calcium and vitamin D, 13% without intervention, and one after PTH injection frequency was decreased. Higher baseline urinary calcium excretion was associated with development of hypercalciuria [relative hazard = 1.5 per 50 mg/d (12.5 mmol/d); 95% confidence interval = 1.2-4.0]. Proportions of patients with elevated serum and urinary calcium were similar on single and combination therapy. CONCLUSIONS: The frequency of episodic hypercalcemia or hypercalciuria in the PaTH trial was 21%. Episodes were generally mild, and nearly all cases resolved spontaneously or with discontinuation of calcium and vitamin D. The algorithms used to address hypercalcemia and hypercalciuria in the PaTH trial proved effective in safely resolving clinical episodes of increased urinary or serum calcium and might therefore be helpful to clinicians caring for patients on PTH.

The Safety and Efficacy of Parathyroid Hormone (PTH) as a Biological Response Modifier for the Enhancement of Bone Regeneration.

Osteoporosis is characterized by low bone mineral density and deterioration in the microarchitecture of bone that increases its fracture vulnerability. The mainstay of therapy for osteoporosis is anti-resorptive in mechanism. Parathyroid hormone (PTH) is the most recently approved anabolic agent for osteoporosis. The mechanism of PTH's skeleton anabolic action is composite involving pathways linked to common signalling peptides that affect gene osteoblast transcription. A number of animal studies and clinical trials have demonstrated that intermittent PTH administration induces anabolic effects on both cancellous and cortical bone, enhances bone mass and increases mechanical bone strength, increasing spine and hip bone mineral density and reducing fragility fractures. Preclinical studies investigating the effect of PTH on fracture healing show an increase in bone density and strength indicating an enhancement of this biological cascade. Preclinical and clinical safety assessments have revealed little evidence of toxic effects and there have been few reports of adverse events related to their use. An increase in osteosarcoma in rats probably is not prognostic of an equivalent possibility in humans. In summary, parathyroid hormone is a major advance in the treatment of osteoporosis. Additional studies addressing long-term clinical safety are needed. However the current evidence is very promising.

Short-term, high-dose parathyroid hormone-related protein as a skeletal anabolic agent for the treatment of postmenopausal osteoporosis.

PTH-related protein (PTHrP) is homologous with PTH. PTH, an effective anabolic agent for treating osteoporosis, has been shown to stimulate both bone resorption by osteoclasts and bone formation by osteoblasts. We examined whether PTHrP might share anabolic properties in osteoporosis. A 3-month double-blind, prospective, placebo-controlled, randomized clinical trial was performed in 16 healthy postmenopausal women with osteoporosis. All received calcium and vitamin D, and all continued their prior hormone replacement therapy. One group also received daily sc PTHrP (6.56 microg/kg x d, or approximately 400 microg/d), and the other group received placebo injections. The PTHrP group displayed a 4.7% increase in lumbar spine bone mineral density (BMD) and also demonstrated an increase in osteoblastic bone formation, as assessed using serum osteocalcin measurements. In contrast, there was no increase in bone-specific alkaline phosphatase and collagen-1 propeptide or either of two markers of osteoclastic bone resorption, N-telopeptide, or deoxypyridinoline. One subject in the placebo group withdrew from the study, but there were no significant adverse events in the PTHrP group. PTHrP administered sc in high doses for only 3 months appears to be a potent anabolic agent, producing a 4.7% increase in lumbar spine BMD. This compares very favorably to available antiresorptive drugs for osteoporosis and is similar to the increases in BMD at this early time point reported for PTH. Despite the high doses, PTHrP was well tolerated. Larger clinical trials are required to confirm these results and fully assess the anabolic potential of PTHrP in osteoporosis.

Skeletal changes in rats given daily subcutaneous injections of recombinant human parathyroid hormone (1-34) for 2 years and relevance to human safety.

Fischer 344 rats (60/sex/group) were given daily subcutaneous injections of recombinant human parathyroid hormone (PTH)(1-34) for 2 years at doses of 0, 5, 30, or 75 microg/kg. Treatment caused substantial increases in bone mass consistent with the known pharmacologic effects of once-daily administration. As determined by quantitative computed tomography (QCT) and histomorphometry, bone mass was markedly increased. Substantial new bone formation resulted in a large decrease in marrow space accompanied by altered bone architecture. Bone proliferative lesions were observed in all PTH( 1-34)-treated groups. Osteosarcoma occurred in 3, 21, and 31 male rats and in 4, 12, and 23 female rats in the 5-, 30-, and 75-microg/kg treatment groups, respectively. Focal osteoblast hyperplasia, osteoma, and osteoblastoma were much less frequent. Although the specific cellular or molecular mechanisms responsible for the rat bone tumors have not been fully elucidated, the data suggest that these lesions resulted from the long duration of treatment and the exaggerated pharmacologic response of the rat skeleton to daily treatment with PTH(1-34). Important differences between the rat study and clinical use in adult humans suggest that the increased incidence of bone neoplasia in rats treated for 2 years is likely not predictive of an increased risk of bone cancer in skeletally mature adult humans being given PTH(1-34) for a limited period of time in the treatment of osteoporosis.