Partial fanconi syndrome induced by imatinib therapy: a novel cause of urinary phosphate loss

Case Report of Renal Calculi in a Child Receiving Imatinib for Acute Lymphoblastic Leukemia

Rationale

Imatinib is used in the treatment of Philadelphia chromosome positive (Ph+) leukemias and has been reported to have a direct effect on bone physiology.

Presentation

To report on a child with Ph+ acute lymphoblastic leukemia who presented with bilateral flank pain and gross hematuria.

Diagnosis

She was diagnosed with obstructive kidney stones 101 days after commencing daily oral imatinib. Stone analysis revealed the presence of calcium phosphate.

Interventions and outcome

The patient passed the stones spontaneously with medical therapy that included the use of thiazide, allopurinol, and potassium citrate, but she required temporary insertion of a double-J stent to relieve an obstruction.

Novel findings

Imatinib inhibits receptor tyrosine kinases and stimulates the flux of calcium from the extracellular fluid into bone, resulting in hypocalcemia with a compensatory rise in parathyroid hormone that may result in phosphaturia and the formation of calcium phosphate stones. Given that kidney stones are rare events in children, we believe that monitoring for kidney stone formation needs to be performed in children receiving imatinib.

Hypophosphatemia in cancer patients

Dysregulation of phosphorus homeostasis resulting in hypophosphatemia is common in cancer patients and can result in serious complications and impact outcomes. Several factors, including critical illness, nutritional status, cancer type and therapy, influence the development of hypophosphatemia. Hypophosphatemia can develop as a result of phosphaturic mesenchymal tumors or as a paraneoplastic phenomenon. The clinical presentation for hypophosphatemia varies depending on the duration and severity of the hypophosphatemia and affects several organ systems. Among other serious effects, hypophosphatemia can impair tissue oxygenation and can cause hemolysis, leukocyte and platelet dysfunction, encephalopathy, seizures, arrhythmias, cardiomyopathy, rhabdomyolysis and coma. Multiple studies have demonstrated that hypophosphatemia is an adverse prognostic marker in inpatients with increased in-hospital stay, mortality and postoperative complications. The phosphate level is homeostatically regulated and maintained in a narrow range by three main hormones: parathyroid hormone, fibroblast growth factor 23 and 1,25-dihydroxyvitaminD₃. Together, these hormones regulate how the intestine, kidneys and bones traffic phosphorus. Several hematological malignancies and cancer therapies are associated with proximal tubular dysfunction (Fanconi syndrome), resulting in phosphaturia. Caution should be taken with parenteral administration of phosphate salts, because secondary complications can develop, principally due to hypocalcemia. The general approach to hypophosphatemia should target the underlying cause. Early recognition and prevention are essential and the approach to hypophosphatemia in the cancer patient, because of the nuances and complexity, should be multidisciplinary.

Focal segmental glomerulosclerosis and concurrent glomerular microangiopathy after long-term imatinib administration

A 79-year-old Japanese man was admitted to our hospital because of proteinuria and kidney dysfunction. He was diagnosed with chronic myeloid leukemia 13 years before and was treated with imatinib. Deep molecular response was achieved but he developed 1+ proteinuria in the first year, which gradually worsened thereafter. Imatinib was discontinued 12 years later but proteinuria and kidney dysfunction were progressive. Percutaneous kidney biopsy revealed mild mesangial hyper-cellularity and matrix increase, swelling of endothelial cells, and partial double contours of glomerular tufts. Subendothelial edema in the interlobular artery was also noted. Immunofluorescence was not remarkable. Electron microscopy revealed endothelial injury with severe sub-endothelial edema. Since imatinib had already been discontinued, conservative therapy with maximal dose of azilsartan was administered. A second biopsy was performed 1 year later because of further deterioration of kidney function, which revealed markedly increased global glomerulosclerosis and severe interstitial fibrosis and tubular atrophy. Segmental glomerulosclerosis with podocyte hyperplasia was also observed. Electron microscopy revealed glomerulosclerotic changes and partially attenuated endothelial injury. Two and a half years later, proteinuria reduced, progression of kidney dysfunction slowed, and he was independent on dialysis therapy. Molecular response of chronic myeloid leukemia was also maintained. The clinical course suggested that endothelial and podocyte injuries were induced by imatinib, and that the nephrotoxic effects lasted for a few years after discontinuation.

Nephrotoxicity From Molecularly Targeted Chemotherapeutic Agents

The introduction of novel molecularly targeted therapies in the last 2 decades has significantly improved the patient survival compared to standard conventional chemotherapies. However, this improvement has been accompanied by a whole new spectrum of kidney adverse events. Although known as "targeted," many of these agents lack specificity and selectivity, and they have a tendency to inhibit multiple targets including those in the kidneys. Early detection and correct management of kidney toxicities is crucial to preserve kidney functions. The knowledge of these toxicities helps guide optimal and continued utilization of these potent therapies. The incidence, severity, and pattern of nephrotoxicity may vary depending on the respective target of the drug. Here, we review the mechanism of action, clinical findings of kidney adverse events, and their proposed management strategies.

Successful determination of imatinib re-administration dosage by therapeutic drug monitoring in a case of chronic myeloid leukemia initiating dialysis for acute renal dysfunction

Fixed dose regimen is currently the standard administration method for TKI. However, this case report indicated that TDM may by a useful approach to individualized dosing of TKI for the treatment of CML when initiating dialysis.

Electrolyte Disorders Induced by Antineoplastic Drugs

The use of antineoplastic drugs has a central role in treatment of patients affected by cancer but is often associated with numerous electrolyte derangements which, in many cases, could represent life-threatening conditions. In fact, while several anti-cancer agents can interfere with kidney function leading to acute kidney injury, proteinuria, and hypertension, in many cases alterations of electrolyte tubular handling and water balance occur. This review summarizes the mechanisms underlying the disturbances of sodium, potassium, magnesium, calcium, and phosphate metabolism during anti-cancer treatment. Platinum compounds are associated with sodium, potassium, and magnesium derangements while alkylating agents and Vinca alkaloids with hyponatremia due to syndrome of inappropriate antidiuretic hormone secretion (SIADH). Novel anti-neoplastic agents, such as targeted therapies (monoclonal antibodies, tyrosine kinase inhibitors, immunomodulators, mammalian target of rapamycin), can induce SIADH-related hyponatremia and, less frequently, urinary sodium loss. The blockade of epidermal growth factor receptor (EGFR) by anti-EGFR antibodies can result in clinically significant magnesium and potassium losses. Finally, the tumor lysis syndrome is associated with hyperphosphatemia, hypocalcemia and hyperkalemia, all of which represent serious complications of chemotherapy. Thus, clinicians should be aware of these side effects of antineoplastic drugs, in order to set out preventive measures and start appropriate treatments.

The potential role of mitochondrial impairment in the pathogenesis of imatinib-induced renal injury

Imatinib is a tyrosine kinase inhibitor widely administered against chronic myeloid leukemia. On the other hand, drug-induced kidney proximal tubular injury, electrolytes disturbances, and renal failure is a clinical complication associated with imatinib therapy. There is no precise cellular mechanism(s) for imatinib-induced renal injury. The current investigation aimed to evaluate the role of mitochondrial dysfunction and oxidative stress in the pathogenesis of imatinib nephrotoxicity. Rats received imatinib (50 and 100 mg/kg, oral, 14 consecutive days). Serum and urine biomarkers of renal injury and markers of oxidative stress in the kidney tissue were assessed. Moreover, kidney mitochondria were isolated, and mitochondrial indices, including mitochondrial depolarization, dehydrogenases activity, mitochondrial permeabilization, lipid peroxidation (LPO), mitochondrial glutathione levels, and ATP content were determined. A significant increase in serum (Creatinine; Cr and blood urea nitrogen; BUN) and urine (Glucose, protein, gamma-glutamyl transferase; γ-GT, and alkaline phosphatase; ALP) biomarkers of renal injury, as well as serum electrolytes disturbances (hypokalemia and hypophosphatemia), were evident in imatinib-treated animals. On the other hand, imatinib (100 mg/kg) caused an increase in kidney ROS and LPO. Renal tubular interstitial nephritis, tissue necrosis, and atrophy were evident as tissue histopathological changes in imatinib-treated rats. Mitochondrial parameters were also adversely affected by imatinib administration. These data represent mitochondrial impairment, renal tissue energy crisis, and oxidative stress as possible mechanisms involved in the pathogenesis of imatinib-induced renal injury and serum electrolytes disturbances.

The footprints of mitochondrial impairment and cellular energy crisis in the pathogenesis of xenobiotics-induced nephrotoxicity, serum electrolytes imbalance, and Fanconi's syndrome: A comprehensive review

Fanconi's Syndrome (FS) is a disorder characterized by impaired renal proximal tubule function. FS is associated with a vast defect in the renal reabsorption of several chemicals. Inherited and/or acquired conditions seem to be connected with FS. Several xenobiotics including many pharmaceuticals are capable of inducing FS and nephrotoxicity. Although the pathological state of FS is well described, the exact underlying etiology and cellular mechanism(s) of xenobiotics-induced nephrotoxicity, serum electrolytes imbalance, and FS are not elucidated. Constant and high dependence of the renal reabsorption process to energy (ATP) makes mitochondrial dysfunction as a pivotal mechanism which could be involved in the pathogenesis of FS. The current review focuses on the footprints of mitochondrial impairment in the etiology of xenobiotics-induced FS. Moreover, the importance of mitochondria protecting agents and their preventive/therapeutic capability against FS is highlighted. The information collected in this review may provide significant clues to new therapeutic interventions aimed at minimizing xenobiotics-induced renal injury, serum electrolytes imbalance, and FS.

Effects of Bosutinib Treatment on Renal Function in Patients With Philadelphia Chromosome-Positive Leukemias

BACKGROUND

The purpose of the study was to assess renal function in patients with Philadelphia chromosome-positive leukemias receiving bosutinib or imatinib.

PATIENTS AND METHODS

Patients received first-line bosutinib (n = 248) or imatinib (n = 251; phase III trial), or second-line or later bosutinib (phase I/II trial; n = 570). Adverse events (AEs) and changes from baseline in estimated glomerular filtration rate (eGFR) and serum creatinine were assessed.

RESULTS

Time from the last patient's first dose to data cutoff was ≥ 48 months. Renal AEs were reported in 73/570 patients (13%) receiving second-line or later bosutinib, and in 22/248 (9%) and 16/251 (6%) receiving first-line bosutinib and imatinib, respectively. eGFR in patients receiving bosutinib declined over time with more patients developing Grade ≥ 3b eGFR (< 45 mL/min/1.73 m² according to the Modification of Diet in Renal Disease method) with second-line or later bosutinib (139/570, 24%) compared with first-line bosutinib (26/248, 10%) and imatinib (25/251, 10%); time to Grade ≥ 3b eGFR was shortest with second-line or later bosutinib. Similar proportions of patients receiving second-line or later bosutinib (74/139, 53%), first-line bosutinib (15/26, 58%), and first-line imatinib (15/25, 60%) improved to ≥ 45 mL/min/1.73 m² eGFR as of the last follow-up. In a regression analysis, first-line treatment with bosutinib versus imatinib was not a significant predictor of Grade ≥ 3b eGFR.

CONCLUSION

Long-term bosutinib treatment is associated with an apparently reversible decline in renal function with frequency and characteristics similar to renal decline observed with long-term imatinib treatment. Patients with risk factors for Grade ≥ 3b eGFR should be monitored closely.

Blockade of Y177 and Nuclear Translocation of Bcr-Abl Inhibits Proliferation and Promotes Apoptosis in Chronic Myeloid Leukemia Cells

The gradual emerging of resistance to imatinib urgently calls for the development of new therapy for chronic myeloid leukemia (CML). The fusion protein Bcr-Abl, which promotes the malignant transformation of CML cells, is mainly located in the cytoplasm, while the c-Abl protein which is expressed in the nucleus can induce apoptosis. Based on the hetero-dimerization of FKBP (the 12-kDa FK506- and rapamycin-binding protein) and FRB (the FKBP-rapamycin binding domain of the protein kinase, mTOR) mediated by AP21967, we constructed a nuclear transport system to induce cytoplasmic Bcr-Abl into nuclear. In this study, we reported the construction of the nuclear transport system, and we demonstrated that FN3R (three nuclear localization signals were fused to FRBT2098L with a FLAG tag), HF2S (two FKBP domains were in tandem and fused to the SH2 domain of Grb2 with an HA tag) and Bcr-Abl form a complexus upon AP21967. Bcr-Abl was imported into the nucleus successfully by the nuclear transport system. The nuclear transport system inhibited CML cell proliferation through mitogen-activated protein kinase (MAPK) and signal transducer and activator of transcription 5 (STAT5) pathways mainly by HF2S. It was proven that nuclear located Bcr-Abl induced CML cell (including imatinib-resistant K562G01 cells) apoptosis by activation of p73 and its downstream molecules. In summary, our study provides a new targeted therapy for the CML patients even with Tyrosine Kinase Inhibitor (TKI)-resistance.

Adefovir dipivoxil-induced Fanconi syndrome and its predictive factors: A study of 28 cases

The aim of the present study was to identify monitoring and prevention measures as well as predictive factors for early detection of renal toxicity associated with long-term administration of adefovir dipivoxil in order to avoid progression to Fanconi syndrome. Clinical data of 28 patients with Fanconi syndrome caused by long-term administration of adefovir dipivoxil for the treatment of chronic hepatitis B virus (HBV) infection were collected pre-and post-administration for analysis. Patients presented with fatigue, progressive systemic pain in multiple bones and joints, as well as difficulty in walking and pathological fractures in a number of severe cases. Laboratory examinations revealed hypophosphatemia, elevated serum cystatin C (Cys-C), elevated serum creatinine (SCr), reduced glomerular filtration rate (GFR), positive urinary protein, erythrocytes and glucose, as well as osteoporosis. In consequence, adefovir dipivoxil administration was stopped, and patients received concentrated divitamins, sodium phosphate syrup and calcitriol. Symptoms and abnormalities in laboratory examinations were significantly improved in all patients after 2-6 months. Therefore, serum phosphate, SCr, routine urine parameters, Cys-C and GFR should be monitored regularly in chronic HBV patients treated with adefovir dipivoxil. The following factors were identified as predictive of kidney damage and Fanconi syndrome: Age ≥40 years, living in rural areas, previous renal toxicity, estimated GFR (eGFR) <90 ml/min/1.73 m², hypertension, diabetes, cirrhosis and duration of adefovir dipivoxil treatment exceeding 24 months. The present results indicate that timely termination of adefovir dipivoxil treatment and replacement with other antiviral agents is critical once renal impairment appears, and that it is necessary to change to other antiviral agents and prolong the interval of administration according to the eGFR level.

Renal Toxicities of Targeted Therapies

With the incorporation of targeted therapies in routine cancer therapy, it is imperative that the array of toxicities associated with these agents be well-recognized and managed, especially since these toxicities are distinct from those seen with conventional cytotoxic agents. This review will focus on these renal toxicities from commonly used targeted agents. This review discusses the mechanisms of these side effects and management strategies. Anti-vascular endothelial growth factor (VEGF) agents including the monoclonal antibody bevacizumab, aflibercept (VEGF trap), and anti-VEGF receptor (VEGFR) tyrosine kinase inhibitors (TKIs) all cause hypertension, whereas some of them result in proteinuria. Monoclonal antibodies against the human epidermal growth factor receptor (HER) family of receptors, such as cetuximab and panitumumab, cause electrolyte imbalances including hypomagnesemia and hypokalemia due to the direct nephrotoxic effect of the drug on renal tubules. Cetuximab may also result in renal tubular acidosis. The TKIs, imatinib and dasatinib, can result in acute or chronic renal failure. Rituximab, an anti-CD20 monoclonal antibody, can cause acute renal failure following initiation of therapy because of the onset of acute tumor lysis syndrome. Everolimus, a mammalian target of rapamycin (mTOR) inhibitor, can result in proteinuria. Discerning the renal adverse effects resulting from these agents is essential for safe treatment strategies, particularly in those with pre-existing renal disease.

Adverse Renal Effects of Novel Molecular Oncologic Targeted Therapies: A Narrative Review

Novel targeted anti-cancer therapies have resulted in improvement in patient survival compared to standard chemotherapy. Renal toxicities of targeted agents are increasingly being recognized. The incidence, severity, and pattern of renal toxicities may vary according to the respective target of the drug. Here we review the adverse renal effects associated with a selection of currently approved targeted cancer therapies, directed to EGFR, HER2, BRAF, MEK, ALK, PD1/PDL1, CTLA-4, and novel agents targeted to VEGF/R and TKIs. In summary, electrolyte disorders, renal impairment and hypertension are the most commonly reported events. Of the novel targeted agents, ipilumumab and cetuximab have the most nephrotoxic events reported. The early diagnosis and prompt recognition of these renal adverse events are essential for the general nephrologist taking care of these patients.

Bilineal Acute Leukemia Associated With Fanconi Syndrome: The First Case Report

Fanconi syndrome is a metabolic disorder involving dysfunction of the renal proximal tubules, resulting in excessive urinary excretion of several metabolites. Various factors may lead to Fanconi syndrome, as it may be a genetic disease with primary or secondary etiologies, or may be acquired. In this study, we report a unique case of Fanconi syndrome with development of a relatively rare acute leukemia, a condition that has not been reported before. The case was an 8-year-old boy with familial occurrence of Fanconi syndrome, presenting with pallor, asthenia, recurrent infections, growth failure, and a variety of biochemical and hematological abnormalities. After physical examination, radiographic studies, and comprehensive laboratory analyses, Fanconi syndrome associated with bilineal acute leukemia, of myeloid and T-lymphoid lineages, was diagnosed.

European LeukemiaNet recommendations for the management and avoidance of adverse events of treatment in chronic myeloid leukaemia

Most reports on chronic myeloid leukaemia (CML) treatment with tyrosine kinase inhibitors (TKIs) focus on efficacy, particularly on molecular response and outcome. In contrast, adverse events (AEs) are often reported as infrequent, minor, tolerable and manageable, but they are increasingly important as therapy is potentially lifelong and multiple TKIs are available. For this reason, the European LeukemiaNet panel for CML management recommendations presents an exhaustive and critical summary of AEs emerging during CML treatment, to assist their understanding, management and prevention. There are five major conclusions. First, the main purpose of CML treatment is the antileukemic effect. Suboptimal management of AEs must not compromise this first objective. Second, most patients will have AEs, usually early, mostly mild to moderate, and which will resolve spontaneously or are easily controlled by simple means. Third, reduction or interruption of treatment must only be done if optimal management of the AE cannot be accomplished in other ways, and frequent monitoring is needed to detect resolution of the AE as early as possible. Fourth, attention must be given to comorbidities and drug interactions, and to new events unrelated to TKIs that are inevitable during such a prolonged treatment. Fifth, some TKI-related AEs have emerged which were not predicted or detected in earlier studies, maybe because of suboptimal attention to or absence from the preclinical data. Overall, imatinib has demonstrated a good long-term safety profile, though recent findings suggest underestimation of symptom severity by physicians. Second and third generation TKIs have shown higher response rates, but have been associated with unexpected problems, some of which could be irreversible. We hope these recommendations will help to minimise adverse events, and we believe that an optimal management of them will be rewarded by better TKI compliance and thus better CML outcomes, together with better quality of life.

A Case of Hypophosphatemia with Increased Urinary Excretion of Phosphorus Associated with Ibrutinib

Ibrutinib, an irreversible oral inhibitor of Bruton's tyrosine kinase, has been used in the treatment of patients with multiple hematologic malignancies. A 59-year-old male with chronic lymphocytic leukemia was treated with 420 mg/day of ibrutinib. No evidence of bruising or diarrhea was noted. The treatment was complicated by a transient increase in creatinine (from a baseline of 1.2 to 1.5 mg/dl) and potassium (reaching a peak of 6.5 mEq/l). Uric acid and calcium levels were normal. The patient developed hypophosphatemia (prior to initiation of therapy the serum phosphorus was 2.9 mg/dl). No metabolic acidosis was noted. Urinalysis showed no glucosuria or proteinuria. Urinary fraction of excretion of phosphate was found to be 345% (normal <5%). Because of these changes, ibrutinib was held, and the patient was given kayexalate. Serum potassium normalized. Serum phosphorus was checked a couple of weeks later and also normalized. A lower dose of ibrutinib (140 mg/day) was restarted. Upon follow-up, the phosphorus level has been between 2.9 and 3.2 mg/dl. No further evidence of hyperkalemia has been noted. Renal function has remained at baseline. To the best of our knowledge, this is the first case report describing the mechanism of hypophosphatemia in a patient treated with ibrutinib.

Electrolyte disorders associated with the use of anticancer drugs

The use of anticancer drugs is beneficial for patients with malignancies but is frequently associated with the occurrence of electrolyte disorders, which can be hazardous and in many cases fatal. The review presents the electrolyte abnormalities that can occur with the use of anticancer drugs and provides the related mechanisms. Platinum-containing anticancer drugs induce hypomagnesemia, hypokalemia and hypocalcemia. Moreover, platinum-containing drugs are associated with hyponatremia, especially when combined with large volumes of hypotonic fluids aiming to prevent nephrotoxicity. Alkylating agents have been linked with the occurrence of hyponatremia [due to syndrome of inappropriate antidiuretic hormone secretion (SIADH)] and Fanconi's syndrome (hypophosphatemia, aminoaciduria, hypouricemia and/or glucosuria). Vinca alkaloids are associated with hyponatremia due to SIADH. Epidermal growth factor receptor monoclonal antibody inhibitors induce hypomagnesemia, hypokalemia and hypocalcemia. Other, monoclonal antibodies, such as cixutumumab, cause hyponatremia due to SIADH. Tyrosine kinase inhibitors are linked to hyponatremia and hypophosphatemia. Mammalian target of rapamycin inhibitors induce hyponatremia (due to aldosterone resistance), hypokalemia and hypophosphatemia. Other drugs such as immunomodulators or methotrexate have been also associated with hyponatremia. The administration of estrogens at high doses, streptozocin, azacitidine and suramin may induce hypophosphatemia. Finally, the drug-related tumor lysis syndrome is associated with hyperphosphatemia, hyperkalemia and hypocalcemia. The prevention of electrolyte derangements may lead to reduction of adverse events during the administration of anticancer drugs.

Drug-Induced Metabolic Acidosis

Metabolic acidosis could emerge from diseases disrupting acid-base equilibrium or from drugs that induce similar derangements. Occurrences are usually accompanied by comorbid conditions of drug-induced metabolic acidosis, and clinical outcomes may range from mild to fatal. It is imperative that clinicians not only are fully aware of the list of drugs that may lead to metabolic acidosis but also understand the underlying pathogenic mechanisms. In this review, we categorized drug-induced metabolic acidosis in terms of pathophysiological mechanisms, as well as individual drugs’ characteristics.

Effects of tyrosine kinase inhibition on bone metabolism: untargeted consequences of targeted therapies

Tyrosine kinase inhibitors (TKIs) are at the forefront of molecular-targeted therapies for cancer. With the advent of imatinib for the treatment of chronic myelogenous leukemia, a new wave of small-molecule therapeutics redefined the oncologic treatment to become chronically administered medications with tolerable side-effect profiles compared with cytotoxic agents. Effects on bone mineral metabolism were observed during early imatinib treatment, in the form of hypophosphatemia with increased urinary phosphorus excretion. This finding led to detailed investigations of off-target effects responsible for changes in bone cell maturation, activity, and impact on bone mass. Subsequently, another BCR-Abl inhibitor (dasatinib), vascular endothelial growth factor (VEGF) inhibitors (sorafenib and sunitinib) as well as rearranged during transfection (RET) inhibitors (vandetanib and cabozantinib) were developed. Inhibition of bone resorption appears to be a class effect and is likely contributed by TKI effects on the hematopoietic and mesenchymal stem cells. As long-term, prospective, clinical outcomes data accumulate on these targeted therapies, the full extent of off-target side effects on bone health will need to be considered along with the significant benefits of tyrosine kinase inhibition in oncologic treatment.

Drug-induced renal Fanconi syndrome

A number of therapeutic drugs are toxic to the kidney proximal tubule (PT) and can cause the renal Fanconi syndrome (FS). The most frequently implicated drugs are cisplatin, ifosfamide, tenofovir, sodium valproate and aminoglycoside antibiotics, and the new oral iron chelator deferasirox has also recently been associated with FS. The incidence of full or partial FS is almost certainly under-estimated due to a lack of appropriate systematic studies, variations in definitions of tubular dysfunction and under-reporting of adverse events. The clinical features of FS are amino aciduria, low molecular weight proteinuria, hypophosphataemia, metabolic acidosis and glycosuria. The most serious complications are bone demineralization from urinary phosphate wasting and progressive decline in kidney function. Commonly used tests for kidney function such as estimated glomerular filtration rate and urine albumin/creatinine ratio are not sensitive markers of PT toxicity; patients at risk should thus be monitored with more appropriate tests, and drugs should be stopped or reduced in dose if toxicity occurs. Substantial recovery of PT function can occur after withdrawal of therapy, but this can take months and chronic damage may persist in some cases.

Tubulointerstitial injury associated with chemotherapeutic agents

Chemotherapy holds tremendous potential in improving the survival of patients with cancer. However, the side effects of these drugs, including those that affect the kidney, can adversely affect patient outcomes. Prompt recognition of these adverse kidney effects allows early intervention that can minimize or prevent patient morbidity. In this review, we examine the nephrotoxic potential of chemotherapy drugs. In concentrating on tubulointerstitial injury, we will review common agents that result in acute kidney injury due to acute tubular necrosis, tubulopathies, crystal nephropathy, acute interstitial nephritis, and chronic interstitial nephritis, and we will present preventive and management strategies.

Simultaneous manifestation of pleural effusion and acute renal failure associated with dasatinib: a case report

WHAT IS KNOWN AND OBJECTIVE

Dasatinib is a novel second-generation inhibitor of multiple tyrosine kinases, indicated for the treatment for Philadelphia chromosome-positive (Ph+) chronic myeloid leukaemia (CML), acute lymphoblastic leukaemia (ALL) and lymphoid blast CML with resistance or intolerance to prior therapy. Although dasatinib is a potent, efficacious and generally well-tolerated drug, patients are also subject to various adverse effects. The most common pulmonary-related side effect is pleural effusion (PE). Renal failure has been reported rarely as a side effect of dasatinib treatment. We report the first case of a patient with imatinib-resistant CML who developed PE and acute renal failure (ARF) simultaneously, after being placed on dasatinib therapy.

CASE SUMMARY

We report a 58-year-old female dasatinib-treated patient with Ph+ chronic phase CML who was admitted to our hospital due to persisted dyspnoea and fever. After reviewing the laboratory and clinical findings, we determined our patient as having simultaneously ARF and PE related to dasatinib therapy. Dasatinib was discontinued, and after 10 days of treatment with ampicillin-sulbactam, allopurinol, amlodipine, furosemide and methylprednisolone, she was discharged home effusion free and with ameliorated renal function.

WHAT IS NEW AND CONCLUSION

PE is the most common extra-haematological toxicity observed during dasatinib treatment whose pathogenesis is still unclear. A possible role of cytokines, such as platelet-derived growth factor receptor (PDGFR)-β and vascular endothelial growth factor (VEGF), in causing endothelial permeability has been suggested. The aetiology of renal failure is also unclear in these patients, but two different possible mechanisms have been suggested such as tumour lysis syndrome and toxic tubular damage. In conclusion, here we describe the first case of simultaneous manifestation of PE and ARF associated with dasatinib. Thus, in patients treated with tyrosine kinase inhibitors, especially those with predisposing nephrological or haematological factors, serum creatinine levels should be monitored routinely.

Off-target effects of BCR-ABL1 inhibitors and their potential long-term implications in patients with chronic myeloid leukemia

In patients with chronic myeloid leukemia (CML), use of the BCR-ABL1-specific tyrosine kinase inhibitors (TKIs) imatinib, nilotinib and dasatinib has greatly improved patient survival and prolonged disease remission. More than 10 years of data from imatinib clinical studies and many years of data for nilotinib and dasatinib have demonstrated that these TKIs are well tolerated in most patients with CML. However, these inhibitors are not entirely BCR-ABL1-specific, and this lack of specificity could account for the off-target effects of these drugs. Adverse events (AEs) are off-target effects that are detrimental to the patient. The underlying mechanisms that contribute to these effects are poorly understood and the long-term consequences of chronic TKI therapy remain largely unknown, particularly with the newer agents. Here, we review the preclinical and clinical data for several of the more frequent AEs associated with TKIs and discuss the therapeutic relevance of these AEs for patients with CML.

Approach to the hypophosphatemic patient

Hypophosphatemia is commonly missed due to nonspecific signs and symptoms, but it causes considerable morbidity and in some cases contributes to mortality. Three primary mechanisms of hypophosphatemia exist: increased renal excretion, decreased intestinal absorption, and shifts from the extracellular to intracellular compartments. Renal hypophosphatemia can be further divided into fibroblast growth factor 23-mediated or non-fibroblast growth factor 23-mediated causes. Proper diagnosis requires a thorough medication history, family history, physical examination, and assessment of renal tubular phosphate handling to identify the cause. During the past decade, our understanding of phosphate metabolism has grown greatly through the study of rare disorders of phosphate homeostasis. Treatment of hypophosphatemia depends on the underlying disorder and requires close biochemical monitoring. This article illustrates an approach to the hypophosphatemic patient and discusses normal phosphate metabolism.

Fanconi syndrome in four non-basenji dogs exposed to chicken jerky treats

Four small-breed dogs were diagnosed with acquired Fanconi syndrome. All dogs ate varying amounts of chicken jerky treats. All dogs were examined for similar clinical signs that included, but were not limited to, lethargy, vomiting, anorexia, diarrhea, and altered thirst and urination. The quantity of chicken jerky consumed could not be determined; however, based on the histories obtained, the chicken jerky treats were a significant part of the diet and were consumed daily by all dogs. Extensive diagnostic testing eliminated other causes of the observed clinical signs, such as urinary tract infection and rickettsial disease. Glucosuria in the face of euglycemia or hypoglycemia, aminoaciduria, and metabolic acidosis confirmed the diagnosis of Fanconi syndrome. All dogs received supportive care, including IV fluids, antibiotics, gastroprotectants, and oral nutritional supplements. Three dogs exhibited complete resolution of glucosuria, proteinuria, and the associated azotemia; however, one dog remained azotemic, resulting in a diagnosis of chronic kidney disease.

[Renal tolerance of targeted therapies]

The use of targeted therapies is increasing in the treatment of cancer. Monoclonal antibodies and tyrosine kinase inhibitors are the most commonly used but other classes such as mTOR inhibitors are increasingly prescribed. These treatments are often given in the long term in metastatic and maintenance treatments. It is therefore important to monitor the occurrence of immediate toxicities but also later and cumulative toxicities. Renal toxicities of targeted therapies are most often due to structural damages of the nephron. The anti-epidermal growth factor receptor (EGFR) and anti-vascular endothelial growth factor receptor (VEGFR) have renal side effects since growth factor receptors are expressed in the kidney. The toxicity of molecules such as bortezomib, erlotinib and lapatinib are less known. The approvals by the Food and Drugs Administration (FDA) and European Medicines Agency (EMA) of sorafenib, sunitinib and temsirolimus were based on studies of less than 3,000 patients. In this context, there is little data on their acute and chronic tolerance, including on the kidneys. This short review synthesizes the physiopathological hypotheses, early diagnosis and treatment of renal toxicity of major targeted therapies available in 2011.

Uncommon or delayed adverse events associated with imatinib treatment for chronic myeloid leukemia

Imatinib, a tyrosine kinase inhibitor, is the first-line therapy for chronic myeloid leukemia (CML). The majority of patients continue treatment for their lifespan because discontinuation generally results in relapse. Many patients treated with imatinib experience adverse events (AEs) at some time during their treatment. Commonly encountered AEs and their management are well known. However, in addition to the common AEs with imatinib, there is a significant number of patients who display either uncommon or delayed AEs. These events can involve cardiac, renal, or dermatologic problems, and fluid retention. Herein, we review these less-than-common side effects and the hazard of administering imatinib during pregnancy. While chronic treatment with imatinib has revolutionized CML prognosis, physicians should be aware of both the common and uncommon adverse reactions.

Acute renal failure under dasatinib therapy

Dasatinib is a second-generation tyrosine kinase inhibitor that is approved for the treatment of imatinib-resistant or imatinib-intolerant chronic myeloid leukemia. It has a 325 times stronger in vitro activity against to native BCR-ABL when comparing with imatinib. Little is known about the effects of dasatinib on renal function. A literature review revealed only one case with imatinib-resistant chronic myeloid leukemia that developed renal failure after being placed on dasatinib therapy. Here we report a patient with imatinib-resistant chronic myeloid leukemia who developed gastroenteritis and acute renal failure after a short time from the initiation of dasatinib therapy. After dasatinib interruption, these side effects resolved completely in days. In summary, dasatinib is a potent drug in the treatment of chronic myeloid leukemia, but close clinical monitoring and the timely interruption of the therapy in patients who developed acute renal failure are warranted.

Evaluation of imatinib mesylate in the treatment of pulmonary arterial hypertension

Imatinib mesylate is a small molecule inhibitor that selectively inhibits the PDGF receptor kinase as well the cKIT and Abl kinases, among other targets. Various studies have implicated the PDGF pathway in the pathogenesis of pulmonary arterial hypertension (PAH). Inhibition with imatinib mesylate has shown efficacy in human case reports and experimental models of PAH. Results from a Phase II trial of imatinib mesylate in PAH did not meet the primary end point but showed improvement in several secondary end points and in a subgroup analysis. As suggested by this study as well as a few case reports, imatinib may be effective in a subset of patients with more severe disease. However, this remains to be further validated through a Phase III study, which is already underway. In conclusion, it appears that imatinib mesylate may hold promise as an adjunct drug in PAH therapy, especially since it is directed at a pathway not previously targeted.

Vascular endothelial growth factor pathway-targeted therapy as initial systemic treatment of patients with renal cancer

Advanced renal cancer is known to be largely refractory to traditional DNA- and DNA repair-targeted chemotherapy. Until recently, immunotherapy had been the mainstay for the treatment; however, it is effective in only a small proportion of patients. Advances in the understanding of the association between the von Hippel-Lindau pathway and angiogenesis and their role in the development of renal cancer has led to the development of highly effective vascular endothelial growth factor (VEGF) pathway-targeted inhibitors. Several such novel agents have demonstrated increased clinical benefit, progression-free survival, and superior quality of life in large, randomized phase III clinical trials, and additional VEGF pathway inhibitors are currently being studied. This review will summarize the major clinical trials and practical recommendations for the most studied VEGF inhibitors, including sunitinib, sorafenib, and bevacizumab; introduce novel VEGF inhibitor agents; outline side effects and toxicities; and discuss sequential and combination therapy with these agents.

Dysregulation of bone remodeling by imatinib mesylate

Imatinib mesylate is a rationally designed tyrosine kinase inhibitor that has revolutionized the treatment of chronic myeloid leukemia and gastrointestinal stromal tumors. Although the efficacy and tolerability of imatinib are a vast improvement over conventional chemotherapies, the drug exhibits off-target effects. An unanticipated side effect of imatinib therapy is hypophosphatemia and hypocalcemia, which in part has been attributed to drug-mediated changes to renal and gastrointestinal handling of phosphate and calcium. However, emerging data suggest that imatinib also targets cells of the skeleton, stimulating the retention and sequestration of calcium and phosphate to bone, leading to decreased circulating levels of these minerals. The aim of this review is to highlight our current understanding of the mechanisms surrounding the effects of imatinib on the skeleton. In particular, it examines recent studies suggesting that imatinib has direct effects on bone-resorbing osteoclasts and bone-forming osteoblasts through inhibition of c-fms, c-kit, carbonic anhydrase II, and the platelet-derived growth factor receptor. The potential application of imatinib in the treatment of cancer-induced osteolysis will also be discussed.

Renal failure associated with tyrosine kinase inhibitors--case report and review of the literature

Imatinib mesylate (IM), nilotinib and dasatinib are tyrosine kinase inhibitors (TKIs) that have revolutionized the treatment of chronic myeloid leukemia (CML). Data regarding the effect of TKIs on the kidney or their safety in patients with renal failure is lacking. We describe a patient with CML who developed renal failure during IM treatment which resolved upon discontinuation of the drug and was not exacerbated by the administration of nilotinib. The literature reporting on the association between TKIs and renal failure is reviewed and the postulated mechanisms including tubular dysfunction caused by the drug or tumor lysis syndrome are discussed.

Controlling subcellular localization to alter function: Sending oncogenic Bcr-Abl to the nucleus causes apoptosis

Altering the subcellular localization of signal transducing proteins is a novel approach for therapeutic intervention. Mislocalization of tumor suppressors, oncogenes, or factors involved in apoptosis results in aberrant functioning of these proteins, leading to disease. In the case of chronic myelogenous leukemia (CML), cytoplasmic Bcr-Abl causes oncogenesis/proliferation. On the other hand, nuclear entrapment of endogenous Bcr-Abl (in K562 human leukemia cells) causes apoptosis. The goal of this study was to determine whether ectopically expressed Bcr-Abl could cause apoptosis of K562 cells when specifically directed to the nucleus via strong nuclear localization signals (NLSs). A single NLS from SV40 large T-antigen or four NLSs were subcloned to Bcr-Abl (1NLS-Bcr-Abl or 4NLS-Bcr-Abl). When transfected into K562 cells, only 4NLS-Bcr-Abl translocated to the nucleus. Bcr-Abl alone was found to localize in the cell cytoplasm, colocalizing with actin due to its actin binding domain. 1NLS-Bcr-Abl also localized with actin. Apoptosis induced by 4NLS-Bcr-Abl was evaluated 24h post-transfection by morphologic determination, DNA staining, and caspase-3 assay. This is the first demonstration that altering the location of ectopically expressed Bcr-Abl can kill leukemia cells. Multiple NLSs are required to overcome Bcr-Abl binding to actin, thus driving it into the nucleus and causing apoptosis.

Decreased bone turnover despite persistent secondary hyperparathyroidism during prolonged treatment with imatinib

CONTEXT

The tyrosine kinase inhibitor imatinib mesylate has an established role in the management of a number of malignant and proliferative conditions. Cross-sectional and short-term prospective studies have demonstrated secondary hyperparathyroidism during imatinib therapy, and variable changes in markers of bone turnover.

OBJECTIVE

Our objective was to determine the biochemical and skeletal effects of imatinib during long-term therapy.

DESIGN

This was a 2-yr prospective study.

SETTING

The study was performed at an academic clinical research center.

PATIENTS OR OTHER PARTICIPANTS

Nine patients with bcr-abl positive chronic myeloid leukemia were included in the study.

INTERVENTIONS

Patients received Imatinib mesylate 400 mg/d.

MAIN OUTCOME MEASURES

Serum and urine biochemistry, markers of bone turnover, and bone mineral density were measured.

RESULTS

Participants developed mild secondary hyperparathyroidism, with significant decreases in serum calcium and phosphate (P < 0.05 and P < 0.0001 vs. baseline, respectively) and an increase in PTH (P < 0.0001 vs. baseline). Biochemical markers of bone turnover demonstrated a biphasic response, with an initial increase in markers of bone formation being followed by a decrease in markers of both formation and resorption. Bone density at the lumbar spine increased [mean (95% confidence interval) change from baseline 3.6% (1.6, 5.5); P = 0.003] as did that at the total body [1.4% (0.2, 2.5); P = 0.065], whereas that at the proximal femur did not change [-0.12% (-3.0, 2.7); P = 0.93]. Body weight and fat mass increased significantly (P < 0.0001 vs. baseline).

CONCLUSIONS

Long-term treatment with imatinib leads to persistent mild secondary hyperparathyroidism. Despite this, bone turnover is decreased, and bone density is stable or increased. Evaluation of the skeletal actions and safety of imatinib during longer-term therapy is warranted.

Electrolyte disturbances and acute kidney injury induced by imatinib therapy

Imatinib mesylate is an anticancer agent that selectively inhibits protein kinases involved in the pathophysiology of cancer. It is now the first-line therapy for patients with chronic myeloid leukaemia (CML) and is generally well tolerated. Here, we describe a case of a patient receiving imatinib for CML. The patient developed renal failure accompanied by severe hypophosphataemia, hypokalaemia and hypomagnesaemia. We discuss the pathophysiological characteristics of imatinib-induced renal injury, and we demonstrate that these electrolyte disturbances were caused by increased urinary excretion of phosphate and potassium. Early diagnosis and correction of imatinib-induced renal injury and electrolyte disorders can improve clinical outcomes.

Renal failure and recovery associated with second-generation Bcr-Abl kinase inhibitors in imatinib-resistant chronic myelogenous leukemia

Tyrosine kinase inhibitors (TKIs) directed against the Bcr-Abl kinase have revolutionized the treatment of chronic myelogenous leukemia (CML). Relatively little is known regarding the effects of these agents on the kidney. Clinically, there have been a handful of reports associating imatinib with acute renal failure. Preclinical reports indicate that imatinib inhibits signaling pathways which may play a role in renal injury. We report the case of a patient with imatinib-resistant CML who developed renal failure after being placed on dasatinib. When she later became resistant to dasatinib she was switched to nilotinib. Shortly thereafter, she became dialysis-independent. Second-generation Bcr-Abl TKIs may influence renal function based on differential inhibition of related tyrosine kinases.