Toxicity of Bisphosphonates

Patterns of bisphosphonate treatment among patients with multiple myeloma treated at oncology clinics across the USA: observations from real-world data

PURPOSE

Current guidelines recommend that intravenous bisphosphonates be initiated in all patients with multiple myeloma for management of bone disease. The objective of this study was to describe real-world bisphosphonate treatment patterns.

METHODS

This was a retrospective observational study using oncology electronic health record (EHR) data contained in Amgen's Oncology Services Comprehensive Electronic Records (OSCER) database, generated by Flatiron Health (New York, NY), representing over 1.5 million US oncology patients. Patients were newly diagnosed with multiple myeloma between January 1, 2009 and April 30, 2016. Timing of bisphosphonate administration, frequency, schedule, changes in dosing schedule, and discontinuations were calculated. Bisphosphonate treatment relative to renal function and anti-multiple myeloma therapy regimens were also assessed.

RESULTS

A total of 11,112 patients were enrolled in the study with a median follow-up of 687 days. Sixty-three percent received ≥ 1 bisphosphonate administration, primarily every 4 weeks (67.7%). Mean time from diagnosis to bisphosphonate administration was 106 days (median, 29). Most patients (58.2%) initiated treatment in first year after diagnosis and about half (51.9%) either discontinued or changed dosing. Patients with poorer renal function by estimated glomerular filtration rate (eGFR) stage at baseline were less likely to receive bisphosphonates (eGFR stage 5 vs 1: 24 vs 72%) and more likely to have delayed initiation of bisphosphonate treatment from diagnosis (eGFR stage 5 vs 1: median 70 vs 25 days).

CONCLUSIONS

Real-world data from US oncology practices indicate that many patients with multiple myeloma may not receive optimal therapy for bone disease, particularly those with renal impairment.

Bisphosphonate conjugation for bone specific drug targeting

Bones provide essential functions and are sites of unique biochemistry and specialized cells, but can also be sites of disease. The treatment of bone disorders and neoplasia has presented difficulties in the past, and improved delivery of drugs to bone remains an important goal for achieving effective treatments. Drug targeting strategies have improved drug localization to bone by taking advantage of the high mineral concentration unique to the bone hydroxyapatite matrix, as well as tissue-specific cell types. The bisphosphonate molecule class binds specifically to hydroxyapatite and inhibits osteoclast resorption of bone, providing direct treatment for degenerative bone disorders, and as emerging evidence suggests, cancer. These bone-binding molecules also provide the opportunity to deliver other drugs specifically to bone by bisphosphonate conjugation. Bisphosphonate bone-targeted therapies have been successful in treatment of osteoporosis, primary and metastatic neoplasms of the bone, and other bone disorders, as well as refining bone imaging. In this review, we focus upon the use of bisphosphonate conjugates with antineoplastic agents, and overview bisphosphonate based imaging agents, nanoparticles, and other drugs. We also discuss linker design potential and the current state of bisphosphonate conjugate research progress. Ongoing investigations continue to expand the possibilities for bone-targeted therapeutics and for extending their reach into clinical practice.

Osteotropic nanoscale drug delivery systems based on small molecule bone-targeting moieties

Bone-targeted drug delivery is an active research area because successful clinical applications of this technology can significantly advance the treatment of bone injuries and disorders. Molecules with bone-targeting potential have been actively investigated as promising moieties in targeted drug delivery systems. In general, bone-targeting molecules are characterized by their high affinity for bone and their predisposition to persist in bone tissue for prolonged periods, while maintaining low systemic concentrations. Proteins, such as monoclonal antibodies, have shown promise as bone-targeting molecules; however, they suffer from several limitations including large molecular size, high production cost, and undesirable immune responses. A viable alternative associated with significantly less side effects is the use of small molecule-based targeting moieties. This review provides a summary of recent findings regarding small molecule compounds with bone-targeting capacity, as well as nanoscale targeted drug delivery approaches employing these molecules.

Intravenous pamidronate versus oral and intravenous clodronate in bone metastatic breast cancer: a randomized, open-label, non-inferiority Phase III trial

Purpose

Patients with metastasized breast cancer often suffer from discomfort caused by metastatic bone disease. Thus, osteoprotection is an important part of therapy in breast cancer metastasized to bone, and bisphosphonates (BPs) are a major therapeutic option. In this study, our objectives were to compare the side effects of oral versus intravenous BP treatment and to assess their clinical effectiveness.

Patients and methods

In this prospective randomized, open-label, non-inferiority trial, we enrolled breast cancer patients with at least one bone metastasis and an Eastern Cooperative Oncology Group performance status of 0–2. Patients were randomly assigned to one of the three treatment groups: A, 60 mg pamidronate intravenously q3w; B-iv, 900 mg clodronate intravenously q3w; and B-o, 2,400 mg oral clodronate daily. Assessments were performed at baseline and every 3 months thereafter.

Results

Between 1995 and 1999, 321 patients with confirmed bone metastases from breast cancer were included in the study. At first follow-up, gastrointestinal (GI) tract side effects were most common, and adverse effects on the GI tract were more frequent in the oral treatment group (P=0.002 and P<0.001, respectively). There were no statistically significant differences among the treatment cohorts for other documented side effects (skin, serum electrolytes, urinary tract, immune system, and others). No significant differences in clinical effectiveness of BP treatment, as assessed by pain score, were detected among the groups; however, pathologic fractures were more effectively prevented by intravenous than oral BP administration (P=0.03). Noncompliance rates were similar among the study cohorts.

Conclusion

We conclude that oral BP treatment is significantly associated with higher rates of adverse GI side effects. Additionally, our data indicate that intravenous BP administration is more effective than oral treatment in prevention of pathologic fractures; hence, oral administration should be considered with caution.

Side effects of bone-targeted therapies in advanced breast cancer

In up to 75% of cases, advanced breast cancer patients eventually develop bone metastases with often debilitating skeletal-related events (SREs). Osteoclast inhibitors are commonly used as therapeutic mainstay with clinical studies showing superiority of denosumab over bisphosphonates (e.g., zoledronate) for the prevention of SREs. The present review discusses the adverse event profile of these agents, and addresses the prevention and management of untoward side effects. Adverse events associated with osteoclast inhibitors comprise osteonecrosis of the jaw and hypocalcemia. Hypocalcemia is more common with denosumab, particularly in severe renal dysfunction. During therapy, the appropriate prevention of these adverse events includes close attention to dental health, avoidance of invasive dental procedures, supplementation with calcium and vitamin D unless patients are hypercalcemic, and regular monitoring of relevant serum values. Relating to the risk of nephrotoxicity, bisphosphonates but not denosumab have been incriminated. Therefore, serum creatinine levels should be checked prior to each dose of zoledronate, and in severe renal dysfunction (creatinine clearance < 30 ml/min) zoledronate is contraindicated anyway. Acute-phase reactions are particularly linked to bisphosphonates. Consequently, if these adverse events predominate, switching to denosumab is recommended.

Palliative Oncology

Bone metastases cause devastating clinical complications leading patients to have pain, poor quality of life, loss of mobility, and autonomy. Complications from osseous metastases cause a big economic burden reflected by repeated admissions for uncontrolled symptoms. Management of symptoms associated with bone metastasis includes systemic analgesics, glucocorticoids, radiation (external beam radiation and radiopharmaceuticals), ablative techniques (radiofrequency ablation and cryoablation), chemotherapeutic agents, hormonal therapies, interventional techniques (eg, kyphoplasty), and surgical approaches. Bisphosphonates have become a standard therapy for bony metastasis. They bind to bone eventually inhibiting osteoclast action. Bisphosphonates decrease fractures when given routinely. Adverse effects of bisphosphonates include osteonecrosis of the jaw and renal insufficiency. Late last year, the Food and Drug Administration approved denosumab to prevent skeletal-related events (SREs) associated with metastatic solid tumors. This drug is a monoclonal antibody that inhibits the receptor activator of nuclear factor κB (RANK)–RANK ligand interaction. Clinical trials have shown superiority over bisphosphonates for the prevention of SREs. This article reviews the mechanism of action, pharmacology, adverse effects, and clinical trial evidence for this new drug.

Targeting polymer therapeutics to bone

An aging population in the developing world has led to an increase in musculoskeletal diseases such as osteoporosis and bone metastases. Left untreated many bone diseases cause debilitating pain and in the case of cancer, death. Many potential drugs are effective in treating diseases but result in side effects preventing their efficacy in the clinic. Bone, however, provides a unique environment of inorganic solids, which can be exploited in order to effectively target drugs to diseased tissue. By integration of bone targeting moieties to drug-carrying water-soluble polymers, the payload to diseased area can be increased while side effects decreased. The realization of clinically relevant bone targeted polymer therapeutics depends on (1) understanding bone targeting moiety interactions, (2) development of controlled drug delivery systems, as well as (3) understanding drug interactions. The latter makes it possible to develop bone targeted synergistic drug delivery systems.

Enhanced anti-tumor activity and safety profile of targeted nano-scaled HPMA copolymer-alendronate-TNP-470 conjugate in the treatment of bone malignances

Bone neoplasms, such as osteosarcoma, exhibit a propensity for systemic metastases resulting in adverse clinical outcome. Traditional treatment consisting of aggressive chemotherapy combined with surgical resection, has been the mainstay of these malignances. Therefore, bone-targeted non-toxic therapies are required. We previously conjugated the aminobisphosphonate alendronate (ALN), and the potent anti-angiogenic agent TNP-470 with N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer. HPMA copolymer-ALN-TNP-470 conjugate exhibited improved anti-angiogenic and anti-tumor activity compared with the combination of free ALN and TNP-470 when evaluated in a xenogeneic model of human osteosarcoma. The immune system has major effect on toxicology studies and on tumor progression. Therefore, in this manuscript we examined the safety and efficacy profiles of the conjugate using murine osteosarcoma syngeneic model. Toxicity and efficacy evaluation revealed superior anti-tumor activity and decreased organ-related toxicities of the conjugate compared with the combination of free ALN plus TNP-470. Finally, comparative anti-angiogenic activity and specificity studies, using surrogate biomarkers of circulating endothelial cells (CEC), highlighted the advantage of the conjugate over the free agents. The therapeutic platform described here may have clinical translational relevance for the treatment of bone-related angiogenesis-dependent malignances.