Targeted treatment of hypereosinophilic syndromes and chronic eosinophilic leukemias with imatinib mesylate

An Intriguing Case of Eosinophilia with FIP1L1/PDGFRA Rearrangement Who Presented as Thrombotic Thrombocytopenic Purpura

Myeloid neoplasm with eosinophilia and FIP1-like-1-platelet-derived growth factor receptor-alpha (FIP1L1-PDGFRA) rearrangement is a multi-organ disease with diverse clinical presentation. Thrombotic thrombocytopenic purpura (TTP) is characterized by the concomitant occurrence of often severe thrombocytopenia, microangiopathic hemolytic anemia, and a variable degree of ischemic organ damage. To our knowledge, only one case of eosinophilia with FIP1L1-PDGFRA rearrangement presented as a case of thrombotic thrombocytopenic purpura reported in the literature. We herein report a case of a young male patient with hypereosinophilic syndrome and FIP1L1-PDGFRA rearrangement who presented with asthma, transient ischemic attacks (TIA), and confusion. He had an acquired TTP that was successfully treated with plasma exchanges (PLEX), corticosteroids, rituximab, and later with the addition of imatinib mesylate (Gleevec, Novartis). He remains in complete remission on imatinib 100 mg daily for more than 28 months of follow-up.

Pharmacology and rationale for imatinib in the treatment of scleroderma

Systemic sclerosis (scleroderma) is a chronic, multisystem, fibrotic disease. Although the pathogenesis is not completely understood, early vascular damage leads to an inflammatory reaction and a severe fibrotic response. Therapy of systemic sclerosis is still not convincing and is mainly restricted to the management of organ complications. A wide choice of immunosuppressive and antifibrotic drugs has been used to try to modify the course of the disease, but significant breakthroughs are still lacking. Imatinib is a tyrosine kinase inhibitor known to regulate growth, proliferation, and differentiation as well as apoptosis of cells and is already widely used for several malignancies, eg, chronic myeloid leukemia and gastrointestinal stromal tumors. It has been used in preclinical as well as clinical studies to modulate the fibrotic process in patients with systemic sclerosis. This is based on its activity to interfere selectively with both the transforming growth factor-β and platelet-derived growth factor signaling pathway. Preclinical studies in mouse models of scleroderma showed significant anti-inflammatory and antifibrotic effects; however, several clinical, proof-of-concept trials have not yet confirmed these initially promising results.

Contemporary consensus proposal on criteria and classification of eosinophilic disorders and related syndromes

Eosinophilia is an important indicator of various neoplastic and nonneoplastic conditions. Depending on the underlying disease and mechanisms, eosinophil infiltration can lead to organ dysfunction, clinical symptoms, or both. During the past 2 decades, several different classifications of eosinophilic disorders and related syndromes have been proposed in various fields of medicine. Although criteria and definitions are, in part, overlapping, no global consensus has been presented to date. The Year 2011 Working Conference on Eosinophil Disorders and Syndromes was organized to update and refine the criteria and definitions for eosinophilic disorders and to merge prior classifications in a contemporary multidisciplinary schema. A panel of experts from the fields of immunology, allergy, hematology, and pathology contributed to this project. The expert group agreed on unifying terminologies and criteria and a classification that delineates various forms of hypereosinophilia, including primary and secondary variants based on specific hematologic and immunologic conditions, and various forms of the hypereosinophilic syndrome. For patients in whom no underlying disease or hypereosinophilic syndrome is found, the term hypereosinophilia of undetermined significance is introduced. The proposed novel criteria, definitions, and terminologies should assist in daily practice, as well as in the preparation and conduct of clinical trials.

Effect of nilotinib on bleomycin-induced acute lung injury and pulmonary fibrosis in mice

BACKGROUND

The tyrosine kinase inhibitor imatinib mesylate was developed as an inhibitor of the kinase activity of BCR-ABL. However, imatinib also has potent inhibitory activity against the platelet-derived growth factor receptor (PDGFR). Nilotinib is approved for treating patients with chronic myeloid leukemia showing resistance or intolerance to imatinib. Like imatinib, nilotinib selectively inhibits the tyrosine kinase activity of PDGFR.

OBJECTIVES

We examined the effect of imatinib and nilotinib on acute lung injury and pulmonary fibrosis in a mouse model.

METHODS

Mice were treated by intratracheal instillation of bleomycin. Imatinib or nilotinib were administered by oral gavage. To study the early inflammatory and late fibrotic phases of lung injury, mice were sacrificed on days 3, 7, 14 and 21 after bleomycin instillation.

RESULTS

Histopathology showed that imatinib and nilotinib attenuated the extent of lung injury and fibrosis. The numbers of inflammatory cells and levels of IL-6, IL-1β and tumor necrosis factor-α were decreased in the imatinib and nilotinib groups on days 3 and 7. Imatinib and nilotinib therapy significantly reduced the levels of hydroxyproline on days 14 and 21, which was accompanied by decreased expression levels of transforming growth factor (TGF)-β1 and PDGFR-β. Imatinib and nilotinib also significantly reduced the expression levels of the genes for TGF-β1 and platelet-derived growth factor (PDGF). Imatinib and nilotinib treatment also significantly inhibited the PDGF-induced proliferation of lung fibroblasts in vitro. When imatinib or nilotinib was given 7 days after the instillation of bleomycin, only nilotinib attenuated pulmonary fibrosis.

CONCLUSIONS

Imatinib and nilotinib attenuated bleomycin-induced acute lung injury and pulmonary fibrosis in mice. In a therapeutic model, nilotinib showed more potent antifibrotic effects than imatinib.

Effect of imatinib on airway smooth muscle thickening in a murine model of chronic asthma

BACKGROUND

Asthma is characterized by airway hyperresponsiveness (AHR), inflammation and remodeling. The tyrosine kinase inhibitor imatinib mesylate was developed to inhibit BCR-ABL kinase activity; however, it also has potent inhibitory activity against the c-Kit and platelet-derived growth factor receptors. The present study aimed to determine whether imatinib suppresses airway smooth muscle (ASM) remodeling and whether its effect is associated with growth factors such as transforming growth factor (TGF)-β1 and stem cell factor (SCF).

METHODS

We developed a mouse model of airway remodeling, which includes smooth muscle thickening, in which ovalbumin (OVA)-sensitized mice were repeatedly exposed to intranasal OVA administration twice a week for 3 months. Mice were treated with imatinib during the OVA challenge.

RESULTS

Mice chronically exposed to OVA developed sustained eosinophilic airway inflammation and AHR compared with control mice. In addition, the mice chronically exposed to OVA developed features of airway remodeling, including thickening of the peribronchial smooth muscle layer. Administration of imatinib significantly inhibited the development of AHR, eosinophilic inflammation and, importantly, ASM remodeling in mice chronically exposed to OVA. Imatinib treatment significantly reduced the levels of interleukin-4, -5 and -13. In addition, TGF-β1 and SCF were significantly reduced in the imatinib-treated animals.

CONCLUSIONS

These results suggest that imatinib administration can prevent not only airway inflammation, but also airway remodeling associated with chronic allergen challenge. Imatinib may provide a clinically attractive therapy for chronic severe asthma.

A case of myeloid neoplasm associated with eosinophilia and KIAA1509-PDGFRβ responsive to combination treatment with imatinib mesylate and prednisolone

A 41-year-old woman presented with dyspnoea, persistent leucocytosis and eosinophilia for 8 months. High-resolution computed tomography scan and pathology of bronchoalveolar lavage confirmed the diagnosis of hypereosinophilic pneumonitis. The patient was treated with prednisolone (0·5-1 mg/kg/day) for more than 20 weeks under the impression of hypereosinophilic syndrome, but without improvement of leucocytosis and eosinophilia. The bone marrow aspiration smear disclosed hypercellular marrow with myeloid hyperplasia and eosinophilia. The fusion gene detection was positive for KIAA1509-PDGFRβ. Myeloid neoplasm associated with eosinophilia and abnormality of PDGFRβ was then diagnosed (Tefferi A, Vardiman JW, Leukemia, 22, 2008, 14). The tyrosine kinase inhibitor, imatinib mesylate (Glivec; 200 mg/day), was administered along with prednisolone (0·25-1 mg/kg/day). White blood cell (WBC) count decreased from 49,500/μL to 17,200/μL, and eosinophil count decreased from 1932/μL to 35/μL, which represent percentage dropped from 7·7%> to 0·2%. Withdrawal of prednisolone was done to avoid adverse events. However, absolute eosinophil count increased progressively despite the continue administration of imatinib and negative detection PDGFRβ fusion gene. The patient then received combination therapy of imatinib and prednisolone again. WBC and absolute eosinophil were normalized subsequently. We had discontinued the prednisolone one more time, and rebound of eosinophilia was seen again. The phenomenon of rebounding of eosinophilia was observed in two subsequent withdrawals of prednisolone. Either steroid or imatinib mesylate alone failed to achieve complete haematological response. A synergistic effect of imatinib and steroid is postulated.

WT1 transcript amount discriminates secondary or reactive eosinophilia from idiopathic hypereosinophilic syndrome or chronic eosinophilic leukemia

Idiopathic hypereosinophilic syndromes (HES) comprise a spectrum of indolent to aggressive diseases characterized by persistent hypereosinophilia. Hypereosinophilia can result from the presence of a defect in the hematopoietic stem cell giving rise to eosinophilia, it can be present in many myeloproliferative disorders or alternatively it may be a reactive form, secondary to many clinical conditions. The hybrid gene FIP1L1-PDGRFalpha was identified in a subset of patients presenting with HES or chronic eosinophilic leukemia (CEL). In spite of this, the majority of HES patients do not present detectable molecular lesions and for many of them the diagnosis is based on exclusion criteria and sometimes it remains doubt. In this study we explored the possibility to distinguish between HES/CEL and reactive hypereosinophilia based on WT1 transcript amount. For this purpose, 312 patients with hypereosinophilia were characterized at the molecular and cytogenetic level and analyzed for WT1 expression at diagnosis and during follow-up. This study clearly demonstrates that WT1 quantitative assessment allows to discriminate between HES/CEL and reactive eosinophilia and represents a useful tool for disease monitoring especially in the patients lacking a marker of clonality.

Apoptosis Induction by Retinoids in Eosinophilic Leukemia Cells: Implication of Retinoic Acid Receptor-α Signaling in All-Trans-Retinoic Acid Hypersensitivity

Hypereosinophilic syndrome (HES) has recently been recognized as a clonal leukemic lesion, which is due to a specific oncogenic event that generates hyperactive platelet-derived growth factor receptor-alpha-derived tyrosine kinase fusion proteins. In the present work, the effect of retinoids on the leukemic hypereosinophilia-derived EoL-1 cell line and on primary HES-derived cells has been investigated. We show that all-trans-retinoic acid (ATRA) inhibits eosinophil colony formation of HES-derived bone marrow cells and is a powerful inducer of apoptosis of the EoL-1 cell line. Apoptosis was shown in the nanomolar concentration range by phosphatidylserine externalization, proapoptotic shift of the Bcl-2/Bak ratio, drop in mitochondrial membrane potential, activation of caspases, and cellular morphology. Unlike in other ATRA-sensitive myeloid leukemia models, apoptosis was rapid and was not preceded by terminal cell differentiation. Use of isoform-selective synthetic retinoids indicated that retinoic acid receptor-alpha-dependent signaling is sufficient to induce apoptosis of EoL-1 cells. Our work shows that the scope of ATRA-induced apoptosis of malignancies may be wider within the myeloid lineage than thought previously, that the EoL-1 cell line constitutes a new and unique model for the study of ATRA-induced cell death, and that ATRA may have potential for the management of clonal HES.

Molecular Analysis of Chronic Eosinophilic Leukemia with t(4;10) Showing Good Response to Imatinib Mesylate

A 38-year-old Japanese man was referred to our hospital in June 2003 for treatment of acute respiratory failure with severe eosinophilia. Idiopathic hypereosinophilic syndrome had been diagnosed in 1994. However, karyotypic examination of bone marrow cells revealed that chromosomal translocation with t(4;10)(q12;p11) had occurred in 2000, and chronic eosinophilic leukemia was diagnosed. At admission, the patient's respiratory condition was extremely serious, and mechanical support was necessary. Despite treatment with steroid pulse therapy and cytarabine, the blood eosinophil count did not decrease, and the patient's respiratory condition worsened. After obtaining informed consent, we administered imatinib mesylate at a dose of 200 mg/day for 2 days and 100 mg/day for 3 days. The blood eosinophil count decreased dramatically over 5 days, and the patient's condition rapidly improved, such that the patient could be discharged. In this case, we performed molecular analysis using peripheral blood. The FIP1-like 1 (FIP1L1)-platelet-derived growth factor receptor alpha (PDGFRalpha) fusion transcript was found with the reverse transcriptase polymerase chain reaction analysis. In this case, eosinophilia was possibly caused by constitutive activation of tyrosine kinase produced by the FIP1L1-PDGFRalpha fusion transcript.

Thrombotic thrombocytopenic purpura in a patient treated with imatinib mesylate: true association or mere coincidence?

Thrombotic thrombocytopenic purpura (TTP), characterized by thrombocytopenia and microangiopathic hemolytic anemia, is a relatively rare disorder. The majority of cases have no defined causes. TTP has been reported in association with many drugs, but not with imatinib mesylate. We report a 22-year-old African-American woman who developed idiopathic hypereosinophilic syndrome. She was treated with imatinib mesylate and subsequently developed microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure. TTP was diagnosed. A kidney biopsy was performed and was diagnostic of thrombotic microangiopathy. The patient was treated with plasma exchange and hemodialysis. Her eosinophilia resolved, but she remained dialysis dependent. To our knowledge, this is the first case report of the possible association between imatinib mesylate and TTP.

Imatinib mesylate as a novel treatment option for hypereosinophilic syndrome: two case reports and a comprehensive review of the literature

Hypereosinophilic syndromes (HES) are a heterogenous group of rare disorders characterized by sustained and otherwise unexplained overproduction of eosinophils with organ involvement and consecutive dysfunction. Recent reports document the efficacy of imatinib mesylate in a large proportion of HES patients (65%). Rearrangements involving the platelet-derived growth factor receptor genes (PDGFRA and PDGFRB), both tyrosine kinase receptors, have been demonstrated to be pathogenetically linked to the dysregulated clonal overproduction of eosinophils. This refined hypothesis has been confirmed by the discovery of the novel FIP1L1-PDGFRA fusion gene, which is a gain-of-function gene on chromosome 4q12. Its product is an imatinib-sensitive tyrosine kinase, which can be found in a subset of patients with HES, particularly in those responding to treatment with imatinib mesylate. Here, we sum up recent knowledge of clinical features, pathophysiology and novel treatment aspects of HES by performing a comprehensive search of the available literature and report on 94 patients. We particularly address the issue of organ involvement and specific characteristics of the variable clinical pictures. In addition, two cases will be presented, which illustrate typical clinical scenarios and treatment outcome.

Genetic alterations and protein expression of KIT and PDGFRA in serous ovarian carcinoma

KIT and PDGFRA are receptor tyrosine kinases that can be specifically inactivated by small-molecule tyrosine kinase inhibitors, notably imatinib mesylate. In ovarian carcinoma, expression of KIT and PDGFRA protein has been documented, but the frequency and the molecular background of expression are poorly known. We analysed the expression of KIT and PDGFRA by immunohistochemistry in 522 serous ovarian carcinomas, and mutations of KIT and PDGFRA by denaturing high-performance liquid chromatographyin 125 and 187 serous ovarian carcinomas, respectively. No mutations of KIT or PDGFRA were detected. KIT expression was detected in 12% of carcinomas: low expression in 10% and high expression in 2% of cases. Using normal serous epithelium as a reference, decreased PDGFRA expression was detected in 12% and increased expression in 13% of carcinomas. Both KIT and PDGFRA expression were associated with high tumour grade, high proliferation index and poor patient outcome. By fluorescence in situ hybridisation, no KIT amplification was found in carcinomas with high KIT expression, but two cases showed a relative gain of chromosome 4. In conclusion, no mutations of KIT or PDGFRA were found, but a subset of serous ovarian carcinoma showed overexpression of the proteins, which was associated with aggressive tumour characteristics.