Socrates E. Papapoulos

Osteoporosis is a chronic disease associated with significant morbidity and mortality and requires long-term therapy. Efficacious and well-tolerated treatments are available, but their effect is either short-lived or lost following their discontinuation. The exception is bisphosphonates that reduce bone resorption and turnover, can be administered in regimens ranging from once-daily to once-yearly, and have been shown in randomized clinical trials to reduce the incidence of all osteoporotic fractures, but their effect persists following their discontinuation. This is due to their property of being taken-up selectively by the skeleton and being slowly released following treatment arrest. This property allows the discontinuation of bisphosphonate treatment for different periods of time, the so-called drug holiday, which reduces the risk of rare adverse events while maintaining the effect; an action particularly important for patients at very high risk of fractures for whom sequential therapy with different agents is currently advised. Thus, bisphosphonates, apart from being the treatment of choice for certain groups of patients, are also indispensable for the consolidation and maintenance of the gains of all other treatments, providing, in addition, the opportunity of temporary treatment arrest. Most patients with postmenopausal osteoporosis will, therefore, receive bisphosphonate at some stage during therapy of their disease, regardless of their initial fracture risk.

Van Buchem disease (VBD) is an inherited rare sclerosing bone disorder, due to defective synthesis of sclerostin, a negative regulator of bone formation. Our earlier cross-sectional studies of patients with VBD and the closely related sclerosteosis suggested that the accrual of bone mass does not continue after puberty but longitudinal studies of patients with sclerostin deficiency are not available. The aim, therefore, of the present study was the long-term assessment of adult patients with VBD. Fifteen previously evaluated patients with genetically confirmed VBD were invited to participate in the study and 11 (4 women) consented. Mean follow-up time was 8.9 ± 1.1 yr and median age at follow-up was 47 yr (range 20-60). Seven patients developed permanent facial paresis, 9 had progressing hearing loss, and 2 developed had increased intracranial pressure requiring cranial surgery. Dental problems were common, and 3 patients developed osteoarthritis during follow-up. None experienced a cardiovascular event. BMD did not change at the LS or the left FN; Z-scores were 10.2 ± 1.3 SD vs 9.4 ± 2.3 SD, p=.62, and 8.9 ± 2.2 SD vs 7.7 ± 2.2 SD, p=.15, respectively. The variability of the clinical expression and progression of the disease, despite the stabilization of BMD but with progressive cranial nerve compression, requires continuous monitoring of these patients for whom no disease-specific therapy is currently available.

Background: Pseudoxanthoma elasticum (PXE), a rare genetic disorder presenting with slowly progressing calcification of various tissues, including the arteries, is caused by mutations in the ABCC6 gene that lead to the reduction of pyrophosphate, a natural inhibitor of calcification. We showed that, compared to a placebo, the cyclical administration of etidronate, a stable pyrophosphate analog, significantly reduced arterial calcification assessed by low-dose CT scans after one year. The aim of the present prospective, single center, observational cohort study was the assessment of the efficacy and safety of cyclical etidronate in patients treated for periods longer than one year. Methods: Seventy-three patients were followed for a median of 3.6 years without etidronate and 2.8 years with etidronate, and each patient served as their own control. Results: The median absolute yearly progression of total calcification volume during the period with etidronate (388 [83–838] µL) was significantly lower than that without etidronate (761 [362–1415] µL; p < 0.001). The rates of the relative progression of arterial calcification were 11.7% (95% CI: 9.6–13.9) without etidronate compared to 5.3% (95% CI: 3.7–7.0) with etidronate, after adjustment for confounders. Conclusions: The cyclical administration of etidronate for nearly 3 years significantly reduced the progression rate of arterial calcification in patients with PXE with pre-existing calcifications without any serious adverse effects.

Summary To test the hypothesis that during treatment with denosumab osteomorphs and precursors recycle to higher number of osteoclasts with time, we measured TRAcP5b in serum taken 6 months after the last injection in postmenopausal women treated for 1–10 years. Serum TRAcP5b values were not related to time of exposure to denosumab. Purpose In women with postmenopausal osteoporosis the aetiology of the observed inverse relationship between duration of denosumab (Dmab) therapy and bone loss after its discontinuation is currently unknown. In studies in mice inhibition of RANKL is associated with an increase in osteomorphs and osteoclast precursors that recycle into osteoclasts and may accumulate with time. We hypothesized that longer inhibition of RANKL by Dmab will be followed by the synchronous formation of a larger number of osteoclasts after stopping treatment. To test this hypothesis, we measured serum TRAcP5b, a marker of osteoclast numbers, in postmenopausal women treated with Dmab for different periods of time up to 10 years. Methods TRAcP5b, C-terminal telopeptide of type 1 collagen (CTX) and procollagen type 1 N-terminal propeptide (P1NP) were measured at 6.0 months ± 15 days after last Dmab injection in 59 women who had received Dmab for 4.0 ± 2.3 years (range 1–10 years). Of these, 38 were treatment naïve (group 1) and 21 had received other treatments prior Dmab (group 2). Results Duration of Dmab treatment was not related to serum TRAcP5b values or to TRAcP5b/CTX ratio either in the whole cohort or in each of the two groups separately. In contrast, serum TRAcP5b values were significantly correlated with serum CTX values (r_s = 0.619; p < 0.001), but not with serum P1NP values or BMD at all skeletal sites. Conclusion Our observations indicate that serum TRAcP5b, measured at 6 months after a Dmab injection, is not a useful early marker for time-dependent increased accumulation of osteoclasts in humans and for identification of patients at risk for a higher rebound increase in bone resorption.

Rebound-associated vertebral fractures (RVFx) following denosumab discontinuation are typically multiple, are commonly associated with acute sharp pain, increase the risk of imminent fractures, and are pathogenetically different from common osteoporotic vertebral fractures (VFx). A clinically relevant question is whether patients with RVFx should be managed differently from patients with osteoporotic VFx. To address this question, we performed a systematic search of the PubMed database, and we reviewed current evidence on the optimal management of patients with RVFx. For pain relief of patients with RVFx, potent analgesics, often opioids, are essential. Information on the effectiveness of braces in these patients is scarce. Vertebroplasty and kyphoplasty are strongly contraindicated as they confer a substantial risk for new VFx. Exercise may be helpful, but again evidence is lacking. In contrast to patients with osteoporotic VFx, in whom initial treatment with bone-forming agents is recommended, patients with RVFx should initiate treatment with potent antiresorptives. To summarize, patients who have sustained RVFx following denosumab discontinuation are at a very high risk for new fractures, especially VFx. The management of such patients requires a multidisciplinary approach that should not be restricted to pain relief and administration of antiosteoporotic medication, but should also include back protection, early mobilization, and appropriate exercise.

Pycnodysostosis, a rare autosomal recessive skeletal dysplasia, is caused by a deficiency of cathepsin K. Patients have impaired bone resorption in the presence of normal or increased numbers of multinucleated, but dysfunctional, osteoclasts. Cathepsin K degrades collagen type I and generates N-telopeptide (NTX) and the C-telopeptide (CTX) that can be quantified. Levels of these telopeptides are increased in lactating women and are associated with increased bone resorption. Nothing is known about the consequences of cathepsin K deficiency in lactating women. Here we present for the first time normalized blood and CTX measurements in a patient with pycnodysostosis, exclusively related to the lactation period. In vitro studies using osteoclasts derived from blood monocytes during lactation and after weaning further show consistent bone resorption before and after lactation. Increased expression of cathepsins L and S in osteoclasts derived from the lactating patient suggests that other proteinases could compensate for the lack of cathepsin K during the lactation period of pycnodysostosis patients.

We prospectively assessed, with predefined criteria, the location and rates of all femur fractures (hip, subtrochanteric/femoral shaft [ST/FS], including atypical [AFF], and distal fractures) in women at increased fracture risk during treatment with the cathepsin K inhibitor, odanacatib (ODN), or placebo over 5 years in the Long‐Term ODN Fracture Trial (LOFT and LOFT Extension [NCT00529373, EudraCT 2007–002693‐66]). ODN was an investigational antiresorptive agent previously in development as an osteoporosis treatment that, unlike bisphosphonates, reduces bone formation only transiently. Women aged ≥65 years with a BMD T‐score ≤ −2.5 at the TH or FN, or with a radiographic vertebral fracture and T‐scores ≤ − 1.5 at the TH or FN, were randomized (1:1) to receive ODN 50 mg/week or placebo. All patients received vitamin D₃ (5600 IU/week) and calcium (total 1200 mg/day); the analysis included 16,071 women. Rates of all adjudicated low‐energy femoral fractures were 0.38 versus 0.58/100 patient‐years for ODN and placebo, respectively (hazard ratio [HR] 0.65; 95% CI 0.51, 0.82; nominal p < 0.001), and for low‐energy hip fractures were 0.29 versus 0.56/100 patient‐years, respectively (HR 0.52; 95% CI 0.40, 0.67; p < 0.001). The cumulative incidence of combined hip and ST/FS or hip fractures alone in the ODN group was consistently lower than in the placebo group (1.93% versus 3.11% for combined fractures, and 1.53% versus 3.03% for hip fractures at 5 years, respectively). However, low‐energy ST/FS fractures were more frequent in ODN‐treated women than placebo‐treated women (24 versus 6, respectively). Among these, 12 fractures were adjudicated as AFF in 10 patients treated with ODN (0.03/100 patient‐years); compared with none in the six placebo‐treated women (estimated difference, 0.03 (95% CI 0.02, 0.06). These results provide insight into possible pathogeneses of AFF, suggesting that the current criteria for diagnosing these fractures may need to be reconsidered.

Cessation of denosumab treatment is associated with increases in bone turnover above baseline values and rapid bone loss. We investigated the efficacy of zoledronate to prevent this bone loss in women with postmenopausal osteoporosis who were treated with denosumab (mean duration 2.2 years) and discontinued treatment after achieving osteopenia. Women were randomized to receive a single 5-mg infusion of zoledronate (ZOL) (n = 27) or two additional 60-mg injections of denosumab (Dmab) (n = 30). Both groups were followed for a total period of 24 months. At 24 months lumbar spine–bone mineral density (LS-BMD) was not different from baseline in the ZOL group, but decreased in the Dmab group by (mean ± SD) 4.82% ± 0.7% (p < 0.001) from the 12-month value; the difference in BMD changes between the two groups, the primary endpoint of the study, was statistically significant (p = 0.025). Results of femoral neck (FN)-BMD changes were similar. ZOL infusion was followed by small but significant increases in serum procollagen type 1 N-terminal propeptide (P1NP) and C-terminal telopeptide of type 1 collagen (CTX) during the first year and stabilization thereafter. In the Dmab group, bone turnover marker values did not change during the first 12 months but increased significantly at 15 months and in the majority of women these remained elevated at 24 months. Neither baseline nor 12-month bone turnover marker values were associated with BMD changes in either group of women. In the Dmab group, three patients sustained vertebral fractures (two patients multiple clinical, one patient morphometric) whereas one patient in the ZOL group sustained clinical vertebral fractures 12 months after the infusion. In conclusion, a single intravenous infusion of ZOL given 6 months after the last Dmab injection prevents bone loss for at least 2 years independently of the rate of bone turnover. Follow-up is recommended, because in a few patients ZOL treatment might not have the expected effect at 2 years. © 2019 American Society for Bone and Mineral Research.