Recombinant Human Parathyroid Hormone (Natpara)

Number: 0894

Policy

Note: REQUIRES PRECERTIFICATION.Footnotes for Precertification of Natpara^*

Aetna considers recombinant human parathyroid hormone 1-84 (rhPTH[1-84]) (Natpara) medically necessary as an adjunct to vitamin D and calcium supplements for adults 18 years of age or older with hypocalcemia due to hypoparathyroidism that cannot be well controlled on calcium supplements and active forms of vitamin D alone, who meet all of the following selection criteria:

• Hypoparathyroidism documented by biochemical evidence of hypocalcemia and concomitant serum intact parathyroid hormone (PTH) concentrations below the lower limit of the normal laboratory reference range on 2 test dates at least 21 days apart within the past 12 months; and
• History of hypoparathyroidism for greater than or equal to 18 months; and
• No known history of hypoparathyroidism resulting from an activating mutation in the CaSR gene or impaired responsiveness to PTH (pseudohypoparathyroidism); and
• No disease that might increase the risk of osteosarcoma, such as Paget's disease, children and young adults less than 25 years of age with open epiphyses (x-rays should document epiphyseal closure), persons with prior history of external beam or implant radiation involving the skeleton, or persons with hereditary syndromes predisposed to ostesarcoma (Li-Fraumeni syndrome (LFS), hereditary retinoblastoma (RB), Rothmund-Thomson syndrome (RTS) type 2, Werner syndrome (WS), Bloom syndrome (BS), RAPADILINO syndrome, and Diamond Blackfan anemia (DBA); and
• Requirement for vitamin D metabolite/analog therapy with calcitriol greater than or equal to 0.25 μg per day or alphacalcidol greater than or equal to 0.50 μg per day; and
• Requirement for supplemental oral calcium treatment greatr than or equal to 1,000 mg per day over and above normal dietary calcium intake; and
• Serum thyroid function tests within normal laboratory limits for persons not on thyroid replacement (for persons on thyroid replacement, thyroxine may be outside of reference range but dose of thyroid replacement should be stable at least 3 months); and
• Serum magnesium levels within laboratory normal limits; and
• Serum 25-hydroxyvitamin D concentration above the lower limit of the normal laboratory reference range; and
• Creatinine clearance greater than 30 ml/min on 2 separate measurements OR creatinine clearance greatr than 60 ml/min AND serum creatinine less than 1.5 mg/dL.

Aetna considers rhPTH(1-84) experimental and investigational for all other indications including the following (not an all-inclusive list) because its effectiveness for these indications has not been established:

• Fracture healing
• Prevention of breast cancer skeletal metastases
• Treatment of osteoporosis
• Treatment of post-surgical hypoparathyroidism.

Footnotes for Precertification of Natpara^* Precertification of Natpara is required of all Aetna participating providers and members in applicable plan designs.  For precertification of toclizumab, call (866) 503-0857, or fax (866) 267-3277.

Background

Hypoparathyroidism is a rare endocrine disorder in which the parathyroid glands fail to produce sufficient amounts of parathyroid hormone (PTH) or where the hormone lacks biologic activity (NPS, 2015).  PTH plays a central role in a variety of critical physiological functions in the body.  Insufficient levels of PTH lead to low levels of calcium and high levels of phosphate in the blood, and an inability to convert native vitamin D into its active state, which helps the body properly absorb oral calcium.  Parathyroid hormone increases serum calcium by increasing renal tubular calcium reabsorption, increasing intestinal calcium absorption (i.e., by converting native vitamin D (25 OH) into its active form (1,25 OH2 vitamin D)) and by increasing bone turnover which releases calcium into the circulation. 

Hypoparathyroidism occurs most commonly as a result of surgical removal of the parathyroid glands and more rarely as a result of autoimmune or congenital diseases (NPS, 2015).  Patients with hypoparathyroidism can experience numbness, tingling, muscle twitching, spasms or cramps, abnormal heart rhythm, and seizures as a consequence of hypocalcemia.  Hypoparathyroidism is also associated with long-term complications such as kidney damage, kidney stones, development of cataracts and calcification of soft tissues. 

The U.S. Food and Drug Administration (FDA) has approved Natpara (recombinant human parathyroid hormone) as an adjunct to calcium and vitamin D to control hypocalcemia in patients with hypoparathyroidism (FDA, 2015).  Natpara received orphan drug status for the treatment of hypoparathyroidism from the FDA in 2007 as it is intended to treat a rare disease. 

Because of the potential risk of osteosarcoma, Natpara is recommended only for patients who cannot be well-controlled on calcium supplements and active forms of vitamin D alone (FDA, 2015).  Natpara was not studied in patients with hypoparathyroidism caused by calcium-sensing receptor mutations or in patients with acute post-surgical hypoparathyroidism. 

The FDA approval of Natpara was supported by 12 pharmacology studies and 4 company-sponsored efficacy and safety studies (NPS, 2015).  In clinical studies, Natpara has been shown to increase serum calcium levels while reducing the need for oral calcium and active vitamin D and, in some cases, eliminate the need for active vitamin D altogether. 

The pivotal Phase 3 study, known as REPLACE (Mannstadt et al, 2013), was a randomized, double-blind, placebo-controlled study in 124 patients with hypoparathyroidism who were randomly assigned to receive Natpara or a placebo.  The trial was designed to determine whether Natpara can be used as a substitute for, or be used to help reduce the amount of, active forms of vitamin D or oral calcium taken by participants.  Results showed 42 % of Natpara-treated participants achieved normal blood calcium levels on reduced doses of calcium supplements and active forms of vitamin D, compared to 3 % of placebo-treated participants. 

Mannstadt et al (2013) reported on the efficacy, safety, and tolerability of Natpara, a once-daily recombinant human parathyroid hormone 1-84 (rhPTH[1-84]) in adults with hypoparathyroidism.  In this double-blind, placebo-controlled, randomized phase III study (REPLACE), investigators recruited patients with hypoparathyroidism (greater than or equal to 18 months duration) aged 18 to 85 years from 33 sites in 8 countries.  Hypoparathyroidism was defined as hypocalcemia (calcium concentration below the lower limit of normal) and documented PTH concentrations below the lower limit of the normal range, recorded on at least 2 occasions within the previous 12 months.  Additional eligibility criteria were: a requirement for active vitamin D and oral calcium (greater than or equal to 1,000 mg daily) treatment, normal thyroid-stimulating hormone concentrations if not on thyroid hormone replacement therapy (or if on therapy, the dose had to have been stable for greater than or equal to 3 months), and normal magnesium and serum 25-hydroxyvitamin D concentrations.  Creatinine clearance needed to be either greater than 30 ml/min on 2 separate measurements, or greater than 60 ml/min (1 measurement) with an accompanying serum creatinine concentration of less than 132.6 μmol/L.  Patients with a known activating mutation in the calcium-sensing receptor gene were excluded.

After an optimization 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 (Mannstadt et al, 2013).  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 to 5).  The primary end-point 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, analyzed by intention to treat.  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); 6 patients in the rhPTH(1-84) group and 7 in the placebo group discontinued before study end.  A total of 48 (53 %) patients in the rhPTH(1-84) group achieved the primary end-point compared with 1 (2 %) patient in the placebo group (percentage difference 51.1 %, 95 % confidence interval [CI]: 39.9 to 62.3; p < 0.0001).  The proportions of patients who had at least 1 adverse event were similar between groups (84 [93 %] patients in the rhPTH[1-84] group versus 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 (10 [11 %] patients) and the placebo group (4 [9 %] patients).  The investigators concluded that 50 μg, 75 μg, or 100 μg per day of rhPTH(1-84), administered subcutaneously in the out-patient setting, is effective and well-tolerated as a PTH replacement therapy for patients with hypoparathyroidism.

An accompanying editorial (Linglart and Rothenbuhler, 2013) noted that, by reducing serum phosphate, rhPTH(1-84) has the potential to prevent of calcium-phosphate precipitation within the kidney and other tissues, the study by Mannstadt et al (2013) had only short-term follow-up.  The editorialist noted that children aged younger than 18 years and patients with a known activating mutation in the calcium-sensing receptor gene did not take part in the study, and stated that further studies should assess the efficacy and safety of rhPTH in these patients.

Fracture Healing

Campbell et al (2015) reviewed current literature regarding possible mechanisms and effectiveness for PTH and teriparatide (PTH 1-34, TPTD) to improve the healing process in the setting of various types of fractures.  This review focused first on the role of PTH in normal bone.  These researchers then discussed mechanisms of normal bone healing as well as delayed and impaired fracture healing.  They summarized pertinent animal data and then reviewed human studies utilizing PTH or TPTD for fracture healing.  In particular, the authors examined unique situations including osteoporotic fractures, diabetes, stress fractures, delayed or poor healing and combination with bisphosphonate therapy.  They concluded that available data indicated there is likely an important role for TPTD and PTH in promoting fracture healing in selected patients, but more clinical trial data are needed.

Treatment of Osteoporosis

Farahmand and colleagues (2016) stated that osteoporosis in men is an important public health problem with more than 1 million cases in Germany.  Although osteoporotic fractures have a much higher mortality in men than in women, male patients are still under-diagnosed and under-treated.  These investigators reviewed the epidemiology of male osteoporosis and current treatment situation, pathophysiological aspects at the hormonal level, risk factors, diagnostic work-up and therapeutic options.  They provided an overview of data concerning male osteoporosis, recommendations for diagnostic work-up and presentation of the study situation on pharmaceutical therapies.  As risk factors for osteoporosis are present in 50 to 70 % of male patients, a detailed patient history is necessary for assessment of the risk factors.  Radiological imaging of the spine is primarily recommended to identify individuals with prevalent vertebral fractures, as approximately 10 % of men over the age of 50 years have suffered a vertebral fracture.  Laboratory testing of relevant parameters helps to rule out other metabolic bone diseases.  In Germany, specific medications available for the treatment of male osteoporosis comprise the active vitamin D analog alfacalcidol, the oral bisphosphonates alendronate and risedronate, the intravenous bisphosphonate zoledronic acid, the anti-receptor activator of NF-κB ligand (RANKL) antibody denosumab, which can be given as intravenous injection and strontium ranelate, a drug with a complex mode of action.  Teriparatide, a recombinant form of the 34 N-terminal amino acid sequence of PTH is the only anabolic agent approved for male osteoporosis.  The authors concluded that osteoporosis in men is increasingly being recognized as an important public health problem and affected patients need to be adequately diagnosed and treated.  Nowadays, a broad spectrum of well-proven therapeutic options with different modes of action allow individual treatment strategies for male osteoporosis patients.

The use of rhPTH[1-84] in the treatment of osteoporosis (male or female) is considered an off-label use.

Prevention of Breast Cancer Skeletal Metastases

Swami and associates (2017) noted that advanced breast cancer is frequently associated with skeletal metastases and accelerated bone loss.  Recombinant PTH [teriparatide, PTH(1-34)] is the 1st anabolic agent approved in the US for treatment of osteoporosis.  While signaling through the PTH receptor in the osteoblast lineage regulates bone marrow hematopoietic niches, the effects of anabolic PTH on the skeletal metastatic niche are unknown.  These researchers demonstrated, using orthotopic and intra-tibial models of 4T1 murine and MDA-MB-231 human breast cancer tumors, that anabolic PTH decreases both tumor engraftment and the incidence of spontaneous skeletal metastasis in mice.  Micro-computed tomography and histomorphometric analyses revealed that PTH increased bone volume and reduced tumor engraftment and volume.  Trans-well migration assays with murine and human breast cancer cells revealed that PTH altered the gene expression profile of the metastatic niche, in particular VCAM-1, to inhibit recruitment of cancer cells.  While PTH did not affect growth or migration of the primary tumor, it elicited several changes in the tumor gene expression profile resulting in a less metastatic phenotype.  The authors concluded that PTH treatment in mice altered the bone microenvironment, resulting in decreased cancer cell engraftment, reduced incidence of metastases, preservation of bone micro-architecture and prolonged survival.  They stated that anabolic PTH clearly warrants further investigation in preventing breast cancer metastasis.

Appendix

Natpara Dosing

Natpara is self-administered once-daily by subcutaneous injection. The starting dose of Natpara is 50 mcg once-daily (NPS, 2015). The dose of Natpara (parathyroid hormone) for injection may be increased in increments of 25 mcg every 4 weeks up to a maximum daily dose of 100 mcg if serum calcium cannot be maintained above 8 mg/dL without an active form of vitamin D and/or oral calcium supplementation. The dose of Natpara (parathyroid hormone) for injection may be decreased to as low as 25 mcg per day if total serum calcium is repeatedly above 9 mg/dL after the active form of vitamin D has been discontinued and calcium supplement has been decreased to a dose sufficient to meet daily requirements.

Additional Information:

The most common adverse reactions associated with Natpara and occurring in greater than 10 % of individuals were: paresthesia, hypocalcemia, headache, hypercalcemia, nausea, and hypoesthesia, diarrhea, vomiting, arthralgia, hypercalciuria and pain in extremity (NPS, 2015).

Natpara can cause some people to have hypercalcemia. serum calcium should be monitored prior to initiating therapy with Natpara and during treatment (FDA, 2015).

People who stop using or miss a dose of Natpara may have an increased risk of hypercalcemia (FDA, 2015).

Natpara contains a Boxed Warning citing the potential risk of osteosarcoma.  During animal drug testing, Natpara caused some rats to develop osteosarcoma (NPS, 2015).  It is not known if people who take Natpara will have a higher chance of getting osteosarcoma.  Natpara will be made available through a Risk Evaluation and Mitigation Strategy (REMS) Program to mitigate the potential risk of osteosarcoma.

It is not known if Natpara is safe and effective for children 18 years of age and younger.  Natpara should not be used in children and young adults who are skeletally immature (NPS, 2015).

Warnings and Precautions:

• Natpara (parathyroid hormone) for injection may cause a potential risk of osteosarcoma: Prescribe Natpara only to patients who cannot be well-controlled on calcium and active vitamin D. Avoid use of Natpara in patients who are at increased risk for osteosarcoma
• Natpara (parathyroid hormone) for injection may cause severe hypercalcemia: Monitor serum calcium when starting or adjusting Natpara dose and when making changes to co-administered drugs known to raise serum calcium.
• Natpara (parathyroid hormone) for injection may cause severe hypocalcemia: Can occur with interruption or discontinuation of Natpara treatment. Monitor serum calcium and replace calcium and vitamin D.
• Natpara (parathyroid hormone) for injection may cause digoxin toxicity: Hypercalcemia increases the risk of digoxin toxicity. In patients using Natpara concomitantly with digoxin, monitor serum calcium more frequently and increase monitoring when initiating or adjusting Natpara dose.
• Confirm vitamin D stores are sufficient and serum calcium is above 7.5 mg/dL before starting Natpara (parathyroid hormone) for injection.
• The starting dose of Natpara is 50 mcg injected once daily in the thigh. When starting Natpara, decrease dose of active vitamin D by 50%, if serum calcium is above 7.5 mg/dL.
• Monitor serum calcium levels every 3 to 7 days after starting or adjusting Natpara dose and when adjusting either active vitamin D or calcium supplements dose while using Naptara.
• Natpara (parathyroid hormone) for injection is available only through a restricted program called the Natpara REMS Program, because of the potential risk of osteosarcoma.
  
  

The above policy is based on the following references: