Bosutinib efficacy and safety in chronic phase chronic myeloid leukemia after imatinib resistance or intolerance: Minimum 24-month follow-up

Bosutinib is an orally active, dual Src/Abl tyrosine kinase inhibitor for treatment of chronic myeloid leukemia (CML) following resistance/intolerance to prior therapy. Here, we report the data from the 2-year follow-up of a phase 1/2 open-label study evaluating the efficacy and safety of bosutinib as second-line therapy in 288 patients with chronic phase CML resistant (n = 200) or intolerant (n = 88) to imatinib. The cumulative response rates to bosutinib were as follows: 85% achieved/maintained complete hematologic response, 59% achieved/maintained major cytogenetic response (including 48% with complete cytogenetic response), and 35% achieved major molecular response. Responses were durable, with 2-year estimates of retaining response >70%. Two-year probabilities of progression-free survival and overall survival were 81% and 91%, respectively. The most common toxicities were primarily gastrointestinal adverse events (diarrhea [84%], nausea [45%], vomiting [37%]), which were primarily mild to moderate, typically transient, and first occurred early during treatment. Thrombocytopenia was the most common grade 3/4 hematologic laboratory abnormality (24%). Outcomes were generally similar among imatinib-resistant and imatinib-intolerant patients and did not differ with age. The longer-term results of the present analysis confirm that bosutinib is an effective and tolerable second-line therapy for patients with imatinib-resistant or imatinib-intolerant chronic phase CML. http://ClinicalTrials.gov Identifier: NCT00261846. Am. J. Hematol. 89:732–742, 2014. © 2014 The Authors American Journal of Hematology Published by Wiley Periodicals, Inc.

Distinct clinical characteristics of myeloproliferative neoplasms with calreticulin mutations

Somatic insertions/deletions in the calreticulin gene have recently been discovered to be causative alterations in myeloproliferative neoplasms. A combination of qualitative and quantitative allele-specific polymerase chain reaction, fragment-sizing, high resolution melting and Sanger-sequencing was applied for the detection of three driver mutations (in Janus kinase 2, calreticulin and myeloproliferative leukemia virus oncogene genes) in 289 cases of essential thrombocythemia and 99 cases of primary myelofibrosis. In essential thrombocythemia, 154 (53%) Janus kinase 2 V617F, 96 (33%) calreticulin, 9 (3%) myeloproliferative leukemia virus oncogene gene mutation-positive and 30 triple-negative (11%) cases were identified, while in primary myelofibrosis 56 (57%) Janus kinase 2 V617F, 25 (25%) calreticulin, 7 (7%) myeloproliferative leukemia virus oncogene gene mutation-positive and 11 (11%) triple-negative cases were identified. Patients positive for the calreticulin mutation were younger and had higher platelet counts compared to Janus kinase 2 mutation-positive counterparts. Calreticulin mutation-positive patients with essential thrombocythemia showed a lower risk of developing venous thrombosis, but no difference in overall survival. Calreticulin mutation-positive patients with primary myelofibrosis had a better overall survival compared to that of the Janus kinase 2 mutation-positive (P=0.04) or triple-negative cases (P=0.01). Type 2 calreticulin mutation occurred more frequently in essential thrombocythemia than in primary myelofibrosis (P=0.049). In essential thrombocythemia, the calreticulin mutational load was higher than the Janus kinase 2 mutational load (P<0.001), and increased gradually in advanced stages. Calreticulin mutational load influenced blood counts even at the time point of diagnosis in essential thrombocythemia. We confirm that calreticulin mutation is associated with distinct clinical characteristics and explored relationships between mutation type, load and clinical outcome.

Omacetaxine mepesuccinate in patients with advanced chronic myeloid leukemia with resistance or intolerance to tyrosine kinase inhibitors

Omacetaxine mepesuccinate promotes apoptosis by inhibiting the production of short-lived oncoproteins. The efficacy and safety of omacetaxine in patients with advanced chronic myeloid leukemia (CML) previously treated with tyrosine kinase inhibitors were assessed in two phase II trials (CML-202 and CML-203). Fifty-one patients in accelerated phase (AP-CML) and 44 in myeloid blast phase (BP-CML) received subcutaneous omacetaxine 1.25 mg/m(2) twice daily days 1-14 every 28 days until hematologic response/improvement or any cytogenetic response, then days 1-7 every 28 days until disease progression. The primary endpoint was maintenance or attainment of a major hematologic response (MHR). Cytogenetic responses were also evaluated. MHR was 37% in patients with AP-CML and 9% with BP-CML (22% and 5% in those with a history of T315I). Most grade 3/4 adverse events were related to myelosuppression, and were generally manageable. Omacetaxine demonstrates activity and an acceptable safety profile in pretreated patients with advanced CML, irrespective of mutational status.

Type and location of isocitrate dehydrogenase mutations influence clinical characteristics and disease outcome of acute myeloid leukemia

Mutations of isocitrate dehydrogenase 1 and 2 (IDH1/2) are genetic alterations in acute myeloid leukemia (AML). The aim of our study was to investigate the frequency and prognostic effect of IDH1/2 mutations together followed by an individual analysis of each substitution in a Hungarian cohort consisting of 376 patients with AML. IDH1(mut) and IDH2(mut) were mutually exclusive, detected in 8.5% and 7.5% of cases, respectively. IDH1/2(mut) was associated with: older age (p = 0.001), higher average platelet count (p = 0.001), intermediate karyotype (p < 0.0001), NPM1(mut) (p = 0.022) and lower mRNA expression level of ABCG2 gene (p = 0.006). Overall survival (OS), remission and relapse rates were not different in IDH1(mut) or IDH2(mut) vs. IDH(neg). IDH1(mut) and IDH2(mut) were associated differently with NPM1(mut); co-occurrence was observed in 14.3% of IDH1 R132C vs. 70% of R132H carriers (p = 0.02) and in 47.4% of IDH2 R140Q vs. 0% of R172K carriers (p = 0.02). IDH1 R132H negatively influenced OS compared to IDH(neg) (p = 0.02) or R132C (p = 0.019). Particular amino acid changes affecting the same IDH1 codon influence the clinical characteristics and treatment outcome in AML.

Randomized phase II study of bortezomib, thalidomide, and dexamethasone with or without cyclophosphamide as induction therapy in previously untreated multiple myeloma

PURPOSE

Bortezomib-thalidomide-dexamethasone (VTD) is an effective induction therapy in multiple myeloma (MM). This phase II, noncomparative study sought to determine whether addition of cyclophosphamide to this regimen (VTDC) could further increase efficacy without compromising safety.

PATIENTS AND METHODS

Patients age 18 to 70 years with previously untreated, measurable MM, who were eligible for high-dose chemotherapy-autologous stem-cell transplantation (HDCT-ASCT), were randomly assigned to bortezomib 1.3 mg/m(2), thalidomide 100 mg, and dexamethasone 40 mg, with (n = 49) or without (n = 49) cyclophosphamide 400 mg/m(2) for four 21-day cycles, followed by HDCT-ASCT. The primary end point was postinduction combined rate of near-complete response (nCR) or better (including complete response [CR] with normalized serum κ:λ free light chain ratio, CR, and nCR).

RESULTS

Postinduction, 51% (VTD) and 44% (VTDC) of patients achieved combined CR/nCR, with bone marrow-confirmed CR in 29% and 31%, overall response rates of 100% and 96%, respectively, and very good partial response or better rates of 69% per arm. Post-HDCT-ASCT, combined CR/nCR rates were 85% (VTD) and 77% (VTDC). In all, 35% (VTD) and 27% (VTDC) of patients were negative for minimal residual disease (MRD) during induction and postinduction. Three-year overall survival was 80% (both arms). Grade 3 to 4 adverse events (AEs) and serious AEs were observed in 47% and 22% (VTD) and 57% and 41% (VTDC) of patients, respectively. The primary health-related quality of life end point (European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire C30 [EORTC QLQ-C30] Global Health score) steadily increased with VTD during induction and reached a clinically relevant difference post-transplantation versus baseline.

CONCLUSION

Both VTD and VTDC are highly active induction regimens producing high combined CR/nCR and MRD-negative rates; however, VTDC was associated with increased toxicity and suggestion of transient decreases in Global Health score, without an increase in activity.

Superiority of the Triple Combination of Bortezomib-Thalidomide-Dexamethasone Over the Dual Combination of Thalidomide-Dexamethasone in Patients With Multiple Myeloma Progressing or Relapsing After Autologous Transplantation: The MMVAR/IFM 2005-04 Randomized Phase III Trial From the Chronic Leukemia Working Party of the European Group for Blood and Marrow Transplantation

Purpose

This prospective multicenter phase III study compared the efficacy and safety of a triple combination (bortezomib-thalidomide-dexamethasone [VTD]) versus a dual combination (thalidomide-dexamethasone [TD]) in patients with multiple myeloma (MM) progressing or relapsing after autologous stem-cell transplantation (ASCT).

Patients and Methods

Overall, 269 patients were randomly assigned to receive bortezomib (1.3 mg/m2 intravenous bolus) or no bortezomib for 1 year, in combination with thalidomide (200 mg per day orally) and dexamethasone (40 mg orally once a day on 4 days once every 3 weeks). Bortezomib was administered on days 1, 4, 8, and 11 with a 10-day rest period (day 12 to day 21) for eight cycles (6 months), and then on days 1, 8, 15, and 22 with a 20-day rest period (day 23 to day 42) for four cycles (6 months).

Results

Median time to progression (primary end point) was significantly longer with VTD than TD (19.5 v 13.8 months; hazard ratio, 0.59; 95% CI, 0.44 to 0.80; P = .001), the complete response plus near-complete response rate was higher (45% v 21%; P = .001), and the median duration of response was longer (17.9 v 13.4 months; P = .04). The 24-month survival rate was in favor of VTD (71% v 65%; P = .093). Grade 3 peripheral neuropathy was more frequent with VTD (29% v 12%; P = .001) as were the rates of grades 3 and 4 infection and thrombocytopenia.

Conclusion

VTD was more effective than TD in the treatment of patients with MM with progressive or relapsing disease post-ASCT but was associated with a higher incidence of grade 3 neurotoxicity.

Characterization and function of histamine receptors in human bone marrow stromal cells

There are several clinical trials worldwide using bone marrow stromal cells (BMSCs) as a cellular therapy to modulate immune responses in patients suffering from various inflammatory conditions. A deeper understanding of the molecular mechanisms involved in this modulatory effect could help us design better, more effective protocols to treat immune mediated diseases. In this study, we demonstrated that human BMSCs express H1, H2, and H4 histamine receptors and they respond to histamine stimulation with an increased interleukin 6 (IL-6) production both in vitro and in vivo. Using different receptor antagonists, we pinpointed the importance of the H1 histamine receptor, while Western blot analysis and application of various mitogen-activated protein kinase inhibitors highlighted the role of p38, extracellular signal-regulated kinase, and c-Jun N-terminal kinase kinases in the observed effect. When BMSCs were pretreated with either histamine or degranulated human mast cells, they exhibited an enhanced IL-6-dependent antiapoptotic effect on neutrophil granulocytes. Based on these observations, it is likely that introduction of BMSCs into a histamine-rich environment (such as any allergic setting) or pretreatment of these cells with synthetic histamine could have a significant modulatory effect on the therapeutic potential of BMSCs.

Expanding Nilotinib Access in Clinical Trials (ENACT), an open-label multicenter study of oral nilotinib in adult patients with imatinib-resistant or -intolerant chronic myeloid leukemia in accelerated phase or blast crisis

Nilotinib has shown favorable safety in patients with Philadelphia chromosome-positive (Ph+) chronic myeloid leukemia (CML) in chronic (CML-CP) or accelerated phase (CML-AP) who failed prior imatinib, and superior efficacy over imatinib in newly diagnosed Ph+ patients with CML-CP. Reported here are the efficacy and safety data for patients in CML-AP (n = 181) or blast crisis (CML-BC) (n = 190; myeloid BC, 133; lymphoid BC, 50; unknown, seven) enrolled in an expanded access phase IIIb study. Non-hematologic adverse events were mostly mild to moderate. Drug-related myelosuppression was generally manageable with dose reductions or interruptions and infrequently led to discontinuation of nilotinib. Drug-related grade 3/4 elevations in serum bilirubin and lipase were infrequent. While an analysis of efficacy was not the primary objective of this study, significant hematologic and cytogenetic responses were observed. These results support the safety and efficacy of nilotinib in patients with advanced CML in AP and BC.

The prognostic impact of germline 46/1 haplotype of Janus kinase 2 in cytogenetically normal acute myeloid leukemia

BACKGROUND

Prognostic risk stratification according to acquired or inherited genetic alterations has received increasing attention in acute myeloid leukemia in recent years. A germline Janus kinase 2 haplotype designated as the 46/1 haplotype has been reported to be associated with an inherited predisposition to myeloproliferative neoplasms, and also to acute myeloid leukemia with normal karyotype. The aim of this study was to assess the prognostic impact of the 46/1 haplotype on disease characteristics and treatment outcome in acute myeloid leukemia.

DESIGN AND METHODS

Janus kinase 2 rs12343867 single nucleotide polymorphism tagging the 46/1 haplotype was genotyped by LightCycler technology applying melting curve analysis with the hybridization probe detection format in 176 patients with acute myeloid leukemia under 60 years diagnosed consecutively and treated with curative intent.

RESULTS

The morphological subtype of acute myeloid leukemia with maturation was less frequent among 46/1 carriers than among non-carriers (5.6% versus 17.2%, P = 0.018, cytogenetically normal subgroup: 4.3% versus 20.6%, P = 0.031), while the morphological distribution shifted towards the myelomonocytoid form in 46/1 haplotype carriers (28.1% versus 14.9%, P = 0.044, cytogenetically normal subgroup: 34.0% versus 11.8%, P = 0.035). In cytogenetically normal cases of acute myeloid leukemia, the 46/1 carriers had a considerably lower remission rate (78.7% versus 94.1%, P = 0.064) and more deaths in remission or in aplasia caused by infections (46.8% versus 23.5%, P = 0.038), resulting in the 46/1 carriers having shorter disease-free survival and overall survival compared to the 46/1 non-carriers. In multivariate analysis, the 46/1 haplotype was an independent adverse prognostic factor for disease-free survival (P = 0.024) and overall survival (P = 0.024) in patients with a normal karyotype. Janus kinase 2 46/1 haplotype had no impact on prognosis in the subgroup with abnormal karyotype.

CONCLUSIONS

Janus kinase 2 46/1 haplotype influences morphological distribution, increasing the predisposition towards an acute myelomonocytoid form. It may be a novel, independent unfavorable risk factor in acute myeloid leukemia with a normal karyotype.

Identification of prognostic factors for plerixafor-based hematopoietic stem cell mobilization

The introduction of plerixafor has enabled successful collection of stem cells in the majority of patients with lymphoma or myeloma in whom previous attempts at mobilization have failed. However, a proportion of patients have been shown to be resistant to this mobilization regimen. To identify the factors that impair stem cell mobilization and collection with plerixafor, we reviewed the data for 197 patients who had undergone mobilization with plerixafor and granulocyte-colony stimulating factor in Central Europe. Predictors of mobilization failure were evaluated using logistic regression analysis. Among the 197 patients mobilized, the target of ≥2.0 × 10(6) CD34+ cells/kg was collected from 133 (67.5%). Our analysis revealed that previous treatment with lenalidomide, bortezomib, melphalan, radiotherapy, or autologous stem cell transplantation and regimen of plerixafor use in combination with chemotherapy had no significant effect on the efficiency of collection. In contrast, an age ≥65 years (odds ratio 0.331, 95% CI: 0.112-0.977, P < 0.05), a diagnosis of non-Hodgkin's lymphoma (odds ratio 0.277, 95% CI: 0.124-0.622, P < 0.01), and treatment with ≥ four chemotherapy regimens (odds ratio 0.366, 95% CI: 0.167-0.799, P < 0.05) were associated significantly with failed mobilization. The rate of successful mobilizations was decreased in patients treated with purine analogues (odds ratio 0.323, 95% CI: 0.096-1.094, P = 0.07) but increased in female patients (odds ratio 1.961, CI: 0.943-4.080, P = 0.07). Patients who are characterized by the above negative features could benefit potentially from further improvement in the mobilization strategy.

Common large partial VWF gene deletion does not cause alloantibody formation in the Hungarian type 3 von Willebrand disease population

BACKGROUND

Type 3 von Willebrand disease (VWD) is an autosomal recessive bleeding disorder, characterized by virtually undetectable plasma von Willebrand factor (VWF) and consequently reduced plasma factor VIII levels. Genetic mutations responsible for type 3 VWD are very heterogeneous, scattered throughout the VWF gene and show high variability among different populations.

METHODS

Twenty-five severe VWD patients were studied by direct sequencing of the 51 coding exons of the VWF gene. The total number of VWD type 3 families in Hungary is 24, of which 23 were investigated.

RESULTS

Fifteen novel mutations were identified in 31 alleles, five being nonsense mutations (p.Q1238X, p.Q1898X, p.Q1931X, p.S2505X and p.S2568X), four small deletions and insertions resulting in frame shifts (c.1992insC, c.3622delT, c.5315insGA and c.7333delG), one a large partial deletion (delExon1-3) of the 5'-region, four candidate missense mutations (p.C35R, p.R81G, p.C295S, p.C623T) and one a candidate splice site mutation (c.1730-10C>A). Six previously described mutations were detected in 17 alleles, including the repeatedly found c.2435delC, p.R1659X and p.R1853X. Only one patient developed alloantibodies to VWF, carrying a homozygous c.3622delT.

CONCLUSION

We report the genetic background of the entire Hungarian type 3 VWD population. A large novel deletion, most probably due to a founder effect, seems to be unique to Hungarian type 3 VWD patients with high allele frequency. In contrast to previous reports, none of the five patients homozygous for the large partial deletion developed inhibitors to VWF. This discrepancy raises the possibility of selection bias in some of the reports.

Analyses of donor-derived keratinocytes in hairy and nonhairy skin biopsies of female patients following allogeneic male bone marrow transplantation

Skin samples taken from 6 female patients receiving allogeneic bone marrow transplants (BMT) from male siblings (n=5) or from unrelated human leukocyte antigen (HLA)-matched male donor (n=1) due to hematological malignancies were studied for the presence of donor cells. One nontransplanted male and 1 female control that received female BM were used as further controls of the technique. Skin biopsies were taken from the scalp and the back from each patient 12-16 years after the successful BMT. We have found donor chimerism in all of the 6 patients in both of their biopsies. Using single and double immunostainings in combination with Y chromosome hybridization, we observed that there are cytokeratin-expressing donor-derived cells in the epidermis of all the 6 patients, the numbers being slightly higher in the scalp (0.37%-1.78%) than in the back (0.32%-1.08%) biopsies. The indication for BMT, and the age of the patient did not seem to have any effect on the numbers found. A few of the double-labeled cells also stained for Ki67, a marker of cellular proliferation, suggesting that the engrafted cells were able to further divide in the epidermis. In 2 patients we observed patches of donor keratinocytes within the epidermis, suggesting a clonal origin. We conclude that in agreement with some and in contrast to other published studies, BM-derived circulating cells are able to engraft in the human skin and to further proliferate there and thus contribute to tissue renewal. These data raise the possibility to use BM cells in regenerative medicine to help in extended injuries, large surface burns, or lack of skin due to other reasons.

Plerixafor for PBSC mobilisation in myeloma patients with advanced renal failure: safety and efficacy data in a series of 21 patients from Europe and the USA

We describe 20 patients with myeloma and 1 with primary amyloidosis from 15 centres, all with advanced renal failure, most of whom had PBSC mobilised using plerixafor following previous failed mobilisation by conventional means (plerixafor used up-front for 4 patients). For 15 patients, the plerixafor dose was reduced to 0.16 mg/kg/day, with a subsequent dose increase in one case to 0.24 mg/kg/day. The remaining six patients received a standard plerixafor dosage at 0.24 mg/kg/day. Scheduling of plerixafor and apheresis around dialysis was generally straightforward. Following plerixafor administration, all patients underwent apheresis. A median CD34+ cell dose of 4.6 × 10(6) per kg was achieved after 1 (n=7), 2 (n=10), 3 (n=3) or 4 (n=1) aphereses. Only one patient failed to achieve a sufficient cell dose for transplant: she subsequently underwent delayed re-mobilisation using G-CSF with plerixafor 0.24 mg/kg/day, resulting in a CD34+ cell dose of 2.12 × 10(6)/kg. Sixteen patients experienced no plerixafor toxicities; five had mild-to-moderate gastrointestinal symptoms that did not prevent apheresis. Fifteen patients have progressed to autologous transplant, of whom 12 remain alive without disease progression. Two patients recovered endogenous renal function post autograft, and a third underwent successful renal transplantation. Plerixafor is highly effective in mobilising PBSC in this difficult patient group.

Dasatinib in imatinib-resistant or imatinib-intolerant chronic myeloid leukemia in blast phase after 2 years of follow-up in a phase 3 study: efficacy and tolerability of 140 milligrams once daily and 70 milligrams twice daily

BACKGROUND

In a phase 3 study, the authors assessed the effects of dasatinib at doses of 140 mg once daily and 70 mg twice daily in patients who had either chronic myeloid leukemia (CML) in advanced phases or Philadelphia chromosome-positive acute lymphoblastic leukemia and were resistant or intolerant to imatinib. In the current report, the results for patients with CML in blast phase after 2 years of follow-up are reported.

METHODS

Patients were stratified according to whether they had CML in myeloid blast phase (MBP-CML) or in lymphoid blast phase (LBP-CML) and were randomized (1:1) within each stratum to receive either oral dasatinib 140 mg once daily or 70 mg twice daily.

RESULTS

In patients with MBP-CML, the major hematologic response rate was 28% for both regimens; and, in patients with LBP-CML, the major hematologic response rate was 42% for once-daily dasatinib and 32% for twice-daily dasatinib. The major cytogenetic response rates were 25% for once-daily dasatinib and 28% for twice-daily dasatinib in patients with MBP-CML, and the respective rates in patients with LBP-CML were 50% and 40%. The overall survival rate at 24 months was 24% for once-daily dasatinib and 28% for twice-daily dasatinib in patients with MBP-CML, and the respective values in patients with LBP-CML were 21% and 16%. Adverse events indicated a trend toward improved tolerability for the once-daily regimen.

CONCLUSIONS

The current results suggested that dasatinib 140 mg once daily had similar efficacy and improved tolerability relative to the 70-mg twice-daily regimen in patients with imatinib-resistant, blast phase CML.

HFE C282Y mutation as a genetic modifier influencing disease susceptibility for chronic myeloproliferative disease

Iron metabolism has been implicated in carcinogenesis and several studies assessed the potential role of genetic variants of proteins involved in iron metabolism (HFE C282Y, TFR S142G) in different malignancies. Few reports addressed this issue with relation to chronic myeloproliferative disorders (CMPD). The aims of our study were (a) to examine the potential associations of CMPD development with genetic modifiers of iron metabolism in a large cohort of CMPD patients; (b) to examine associations of genetic variants of proteins involved in iron metabolism; and acquired JAK2 V617F mutation with clinical characteristics of CMPD. HFE C282Y was genotyped in 328 CMPD patients and 996 blood donors as controls, HFE H63D, and TFR S142G were tested in CMPD patients and 171 first time blood donors. JAK2 V617F mutation was tested in CMPD patients and in 122 repeated blood donors. Decreased C282Y allele frequency (allele frequency+/-95% confidence interval) was found in the CMPD group (1.8%+/-1.0%) compared with controls (3.4%+/-0.8%; P=0.048). TFR S142G allele frequency was reduced among V617F-negative CMPD patients (34.8%+/-7.6%) compared with controls (47.8%+/-5.4%; P=0.02). The frequency of JAK2 V617F was 75.9% (249 of 328) in the CMPD group. At presentation, elevated hemoglobin levels were found in V617F-positive patients compared with V617F-negative counterparts (P<0.000). Vascular complications (26.6% versus 15.2%; P=0.039) as well as female gender (57.4% versus 41.8%; P=0.019) were more common in V617F-positive patients. We found that HFE C282Y might be associated with a protective role against CMPD. Because chronic iron deficiency or latent anemia may trigger disease susceptibility for CMPD, HFE C282Y positivity may be a genetic factor influencing this effect.

An Alu-mediated novel large deletion is the most frequent cause of type 3 von Willebrand disease in Hungary

BACKGROUND

We studied 24 Hungarian patients from 23 unrelated families to identify the genetic background of the entire type 3 von Willebrand disease (VWD) population in this country. The current report focuses on the molecular characterization of a novel large deletion.

RESULTS

A large partial deletion (delExon1-3) of the 5'-region of the von Willebrand factor gene (VWF) was detected in 12/48 alleles (25% of all type 3 alleles). The 5'-deletion breakpoint is located in the untranslated region between VWF and CD9, whereas the 3' breakpoint is in intron 3 of VWF. Analysis of the breakpoints showed Alu Y and Alu SP repetitive sequences at the ends of the deletion, suggesting that a recombination event caused the subsequent loss of the 35-kb fragment. DelExon1-3 was not found in any of the other screened populations.

CONCLUSION

We report a large novel deletion including exons 1, 2 and 3 of VWF commonly causing type 3 VWD in the Hungarian population. This mutation, probably caused by an Alu-mediated recombination event, and subsequently distributed in Hungary by a founder effect, seems to be unique to Hungarian patients with a high allele frequency. Together, delExon1-3 and 2435delC make up 37.5% of the genetic defects in Hungarian patients with VWD type 3. This offers a rational approach to molecular testing of relevant families in Hungary.