CLINICAL TRIAL COMMENTARY Zoledronic acid in the management of osteoporosis: the HORIZON trials Zoledronic acid 5 mg is an annually administered intravenous bisphosphonate that is approved for the treatment of osteoporosis. The Health Outcomes and Reduced Incidence with Zoledronic acid ONce yearly (HORIZON) Pivotal Fracture trial showed an increase in bone mineral density, decrease in bone turnover markers, and signifi cant reduction in the risk of vertebral, hip and other fractures in women with postmenopausal osteoporosis treated over a period of 3 years. The HORIZON Recurrent Fracture Trial demonstrated that an annual infusion of zoledronic acid started within 90 days of surgical repair of a low-trauma hip fracture in women and men was associated with a signifi cant decrease in the risk of new clinical fractures and an increase in survival. The tolerability and safety profi le of treatment in both studies was generally favorable, with the most common adverse event being transient fl u-like symptoms shortly after infusion. KEYWORDS: bisphosphonates, fractures, osteoporosis, treatment, zoledronate, zoledronic acid Osteoporosis is a skeletal disease characterized their predominant effect on bone remodeling. E Michael Lewiecki by low bone mineral density (BMD) and poor Estrogens, bisphosphonates (e.g., alendronate, New Mexico Clinical Research bone quality that reduces bone strength and risedronate, ibandronate and zoledronic acid), & Osteoporosis Center, increases the risk of fractures [1] . It is a worldwide calcitonin and raloxifene are antiresorptive 300 Oak St. NE, Albuquerque, public health problem with serious consequences agents that strengthen bone by decreasing NM 87106, USA in terms of personal suffering and costs to soci- bone turnover. This results in stabilization or Tel.: +1 505 938 2117 ety [2,3]. Approximately 30% of postmenopausal an increase in BMD by reducing the remod- Fax: +1 505 884 4006 Caucasian women have osteoporosis [4], with a eling space and prolonging secondary miner- [email protected] lifetime fracture risk of 40% [5]. Fractures of alization. Bone microarchitecture is preserved, the hip and spine are associated with increased with a reduction in trabecular perforation and morbidity and mortality [6,7]. Despite the gen- decrease in cortical porosity. Recombinant eral availability of clinical tools to diagnose human parathyroid hormone, PTH(1-34) (teri- osteoporosis and predict the risk of fractures [8], paratide) and PTH(1-84), are anabolic drugs patients who could benefi t from treatment to that strengthen bone and reduce fracture risk by reduce fracture risk are commonly not recog- increasing bone formation. They are associated nized or treated [9]. When patients are started with an increase in bone size and restoration or on a pharmacological therapy for osteo porosis, formation of new trabecular microarchitectural compliance is poor [10] . Typically, less than 50% elements. Strontium ranelate (approved in some of patients are still taking the drug 1 year after it countries for the treatment of osteoporosis) may is prescribed [11] . It has been demonstrated that have both antiresorptive and anabolic properties. patients who are compliant to therapy have a Although all of these drugs have been shown to greater increase in BMD [12], lower fracture risk reduce the risk of fractures in women with post- [13] and reduced healthcare costs [10] compared menopausal osteoporosis, each has limitations with those who are not compliant. The US as well. Oral bisphosphonates have complex Surgeon General has identifi ed poor compliance administration requirements (fasting, ingestion and persistence to therapy as a major obstacle in with plain water only and post-dose fasting) and the treatment of osteoporosis, and suggested that have been associated with upper gastro intestinal less frequent dosing and simplifi ed drug admin- symptoms when used in clinical practice. istration be considered as a potential means to Intravenous (iv.) bisphosphonates (ibandronate improve adherence [14] . and zoledronic acid) must be given by trained Drugs for the treatment of osteoporosis are staff in a physician’s offi ce or infusion center. classifi ed as antiresorptive (anticatabolic) or Estrogen and raloxifene are associated with non- anabolic (bone-building) [15], depending on skeletal risks (e.g., thromboembolic events), as 10.2217/14750708.5.6.829 © 2008 Future Medicine Ltd Therapy (2008) 5(6), 829–835 ISSN 1475-0708 829 CLINICAL TRIAL COMMENTARY Lewiecki well as nonskeletal benefi ts, such as reduction in osteoporosis. Patients were randomly assigned to hot fl ashes with estrogen and decreased risk of once-yearly treatment with a 15-min infusion of invasive breast cancer with raloxifene. Nasal cal- either zoledronic acid 5 mg or placebo given at citonin is usually well tolerated, but may cause baseline, month 12 and month 24. All participants nasal congestion, burning or bleeding in some received daily calcium (1000–1500 mg) and vita- patients. Teriparatide involves daily self-admin- min D (400–1200 IU). Patients were seen at clinic istered subcutaneous injection, and is higher visits at months 6, 12, 24 and 36, and contacted in cost than the other agents. Recent trends in quarterly for telephone interviews. the development of drugs for the treatment of postmenopausal osteoporosis (PMO) have been Study population toward injectable dosing with long dosing inter- Postmenopausal women between the ages of 65 vals, with the goal of maximizing compliance and 89 years were eligible for participation in and persistence to effective and safe therapy. the study if they had a BMD T-score of -2.5 The most recent bisphosphonate to be approved or less at the femoral neck (i.e., a densitometric for the treatment of PMO is iv. zoledronic diagnosis of osteoporosis) or a T-score of -1.5 or acid 5 mg every 12 months (also known as less with radiological evidence of at least two zoledronate; Reclast® in the USA, Aclasta® mild or one moderate vertebral fracture (i.e., a in other countries, Novartis Pharmaceutical clinical diagnosis of osteoporosis). Previous use Corporation, NJ, USA) (FIGURE 1). It is also of oral bisphosphonates was allowed, provided approved to reduce the incidence of new clini- a prespecifi ed washout period was attained. cal fractures in patients at high risk of fracture, Concomitant use of the following bone-active defi ned as a recent low-trauma hip fracture, and agents was allowed at baseline and during the for the treatment of Paget’s disease of the bone. study: hormone therapy, raloxifene, calcitonin, Zoledronic acid 5 mg iv. given annually for the tibolone, tamoxifene, dehydroepiandrosterone, treatment of osteoporosis should not be confused iprifl avone and medroxyprogesterone. Patients with zoledronic acid 4 mg (Zometa®, Novartis were not eligible for participation if there was Pharmaceutical Corporation) iv., which is given any previous use of parathyroid hormone, stron- with a much shorter dosing interval (often every tium ranelate or sodium fl uoride; use of anabolic 3–4 weeks) and far greater cumulative dosage steroids or growth hormone within 6 months of for cancer-related conditions (hypercalcemia of study entry; or use of oral or iv. gluco corticoids malignancy, bone metastases associated with in the previous 12 months. Patients with abnor- solid tumors and multiple myeloma). This is a mal serum calcium levels (>2.75 mmol/l or review of two clinical trials evaluating the effi - <2.00 mmol/l) or abnormal renal function cacy and safety of zoledronic acid 5 mg every (calculated creatinine clearance <30 ml/min 12 months for the treatment of osteoporosis – or urine dipstick showing >2+ protein) were the Health Outcomes and Reduced Incidence excluded. Patients were divided into two strata: with Zoledronic acid ONce yearly (HORIZON) Stratum 1 patients were taking no osteo porosis Pivotal Fracture Trial [16] and the HORIZON medications at the time of randomization Recurrent Fracture Trial [17] . Stratum 2 patients were taking an allowed HORIZON Pivotal Fracture Trial osteoporosis medication. Design The HORIZON Pivotal Fracture Trial was a Effi cacy end points 3-year, Phase III, international, multicenter, There were two primary end points: new randomized, double-blind, placebo-controlled morpho metric vertebral fractures in Stratum 1 clinical trial evaluating the effi cacy and safety of and hip fractures in Stratum 1 and Stratum 2. zoledronic acid in women with postmenopausal Secondary end points included any non vertebral fracture, any clinical fracture and clinical ver- tebral fracture; BMD change at the lumbar N PO3H2 spine, femoral neck and total hip; and changes in bone turnover markers – serum C-telopeptide N OH•H2O of type 1 collagen (a marker of bone resorp- tion) and bone-specifi c alkaline phosphatase (a PO3H2 marker of bone formation). Vertebral fractures were diagnosed with lateral spine radiographs Figure 1. Zoledronic acid. carried out at baseline, and at months 12, 24 and 830 Therapy (2008) 5(6) future science group Zoledronic acid for osteoporosis: the HORIZON trials CLINICAL TRIAL COMMENTARY 36 or early termination for those in Stratum 1, and at baseline, month 36 or early termination Placebo Zoledronic acid for Stratum 2. Vertebral fractures were defi ned according to quantitative morphometry and 15 Relative risk, 0.30 standard methods [18]. BMD was measured p < 0.001 by dual-energy x-ray absorptiometry (DXA) at Relative risk, 0.29 10.9% baseline and at months 6, 12, 24 and 36. 10 p < 0.001 7.7% Relative risk, 0.40 Assessment of safety p < 0.001 fracture (%) 5 All adverse events and serious adverse events were 3.7% 3.3% recorded and categorized according to standard 1.5% 2.2% coding procedures. Renal safety was evaluated vertebral with new Patients 0 in a subgroup of patients by measuring serum 0–1 0–2 0–3 creatinine 9–11 days after each infusion. Cardiac Year safety was measured in another subgroup with Figure 2. Relative risk of morphometric vertebral fracture in the HORIZON 12-lead electrocardiograms before and 9–11 days Pivotal Fracture Trial.