ALBERT

Description: Analysis of diversity and clonality is an important tool in monitoring reconstitution of the immune system and identificating specific immune reaction clones involved in hematological malignancy individuals who accepted hematological stem cell transplantation (HSCT). We have previously reported the evolution of malignant and reactive γδ+ T cell clones in a case with relapse T-ALL before and after allogeneic stem cell transplantation (allo-SCT) (from 4 weeks to 108 weeks), relapse was discovered with the same TCR Vδ5+ T cell clone at 100 weeks after transplantation, and the patient underwent chemotherapy over the next two months and achieved again remission with minimal residual disease (MRD). We sequentially monitored the clinical and laboratorial features of this T-ALL case. The patient was received three times donor lymphocytes infusion (DLI) at 117, 120 and 124 weeks after HSCT. In 178 weeks after transplantation, the patient underwent relapse again, however, in this time the patient underwent III grade chronic graft versus host disease (cGvHD). We continued to analyze the samples at different time points after HSCT and DLI, the leukemic Vδ5+ T cell clone was detected in most samples, while this clone could not be detected in donor sample (Figure 1). Moreover, we found that a monoclonally expanded TCR Vδ4 which we reported before and it remained detectable in all samples post transplantation, interesting same monoclonal Vδ4 clone was identified in sample from donor which was collected at time for DLI. The sequence of Vδ4 was confirmed as same TCR rearrangement: Vδ4Dδ3Jδ1, and the expression level of Vδ4 was significantly increased at the time of disease relapse, the Vδ4 expression level in samples from PBMC and bone marrow at different time point was showed in figure 2. The monoclone Vδ4 from donor was thought as specifically expanded for unknown antigen (maybe for virus or leukemia) and may possess cytotoxicity in donor, however, the persistent expansion of Vδ4 in receptor was thought that might be responsible for leukemic cells, virus infection or cGvHD, it remains an opne question. Because patient underwent III grade cGvHD, and whether this Vδ4+ T cell clone was mainly associated with cGvHD, it is needed further investigation. In addition, the clonally expanded Vδ3 with same size was also detected at time before HSCT, and most time points after HSCT, while it could not be identified in donor sample (Figure 3). Obviously, this expanded Vδ3+ T cell clone originated from patient, and it is possible that this T cell clone possesssed a specific anti-leukemia function, because it appeared at the time with minimal residual disease, however, the function of clonally expanded Vδ3 is needed further confirmation. And it is needed also to analyze the clonality of TCR Vα and Vβ subfamilies. In conclusion, dynamically monitoring TCR repertoire and combining the characteristic of clinical status might benefit for characterizing the malignant clonal evolution, monitoring the specific T cell clone for graft-versus-leukemia (GvL) or GvHD effect and designing specific therapeutic strategies in T-ALL. Competing interests The authors declare that they have no competing interests. Grants: This study was supported by grants from the National Natural Science Foundation of China (Nos. 91129720 and 81270604), the Collaborated grant for HK-Macao-TW of the Ministry of Science and Technology (2012DFH30060), the Guangdong Science & Technology Project (No. 2012B050600023), the Fundamental Research Funds for the Central Universities (No. 21610603, 21612116). Figure 1. The CDR3 spectratyping of the TCR Vγ and Vδ subfamily T cells in peripheral blood from donor and recipient at different time points after allo-HSCT. Figure 1. The CDR3 spectratyping of the TCR Vγ and Vδ subfamily T cells in peripheral blood from donor and recipient at different time points after allo-HSCT. Figure 2. The expression level of the TCR Vδ4 gene in recipient at different time points post-HSCT: Red dots showing the expression level of TCRVδ4 (TCDV4) gene in PBMC at time points of 117 W, 120 W, 135 W, 142 W, 146 W, 178 W, 190 W and 200 W post-HSCT. Blue triangles showing the expression level of TCRDV4 genes in bone marrow (BM) at time points of 129.5 W, 178 W, 190 W and 200 W post-HSCT. Figure 2. The expression level of the TCR Vδ4 gene in recipient at different time points post-HSCT: Red dots showing the expression level of TCRVδ4 (TCDV4) gene in PBMC at time points of 117 W, 120 W, 135 W, 142 W, 146 W, 178 W, 190 W and 200 W post-HSCT. Blue triangles showing the expression level of TCRDV4 genes in bone marrow (BM) at time points of 129.5 W, 178 W, 190 W and 200 W post-HSCT. Figure 3. The The CDR3 spectratyping of Vδ3 T cells in the samples of donor and recipient at different time points post-HSCT. The red boxes indicated the clonally expanded Vδ3 T cell clone with 526 bp which contained the same sequence confirmed by PCR product direct nucleotide sequencing. Figure 3. The The CDR3 spectratyping of Vδ3 T cells in the samples of donor and recipient at different time points post-HSCT. The red boxes indicated the clonally expanded Vδ3 T cell clone with 526 bp which contained the same sequence confirmed by PCR product direct nucleotide sequencing. Disclosures Xu: National Natural Science Foundation of China (Nos. 91129720 and 81270604), the Collaborated grant for HK-Macao-TW of the Ministry of Science and Technology (2012DFH30060), the Guangdong Science & Technology Project (No. 2012B050600023): Research Funding; Fundamental Research Funds for the Central Universities (No. 21610603, 21612116): Research Funding. Li:Fundamental Research Funds for the Central Universities (No. 21610603, 21612116). : Research Funding; National Natural Science Foundation of China (Nos. 91129720 and 81270604), the Collaborated grant for HK-Macao-TW of the Ministry of Science and Technology (2012DFH30060), the Guangdong Science & Technology Project (No. 2012B050600023): Research Funding.

Description: Comparison of the 5 year Medical Outcome and Quality of Life of Patients with Chronic Myeloid Leukemia treated with Imatinib or Allogeneic Transplant Jianyu Weng1*, Lisi Huang1*, Peilong Lai1, Zesheng Lu1, Ping Wu1, Suijing Wu1, Chengwei Luo1, Wei Ling1, Chenxin Deng1, Xin Huang1, Suxia Geng1, Xin Du1? 1Department of Hematology, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, P.R. China. *These authors contributed equally to this work.? Corresponding author: Xin Du, MD, Ph.D. 106. Zhongshan Er Rd, Guangzhou, 510080, P.R. China E-mail: miyadu@hotmail.com Phone: (86)-20-83827812-62122 Fax: (86)-20-83889772 Abstract To evaluate and compare the long-term medical outcome and health-related quality of life (HRQOL) of patients with CML in chronic phase (CML-CP) who received imatinib or an allogeneic hematopoietic stem cell transplant (allo-HSCT) using retrospective analysis and an embedded cross-sectional study. CML-CP patients who received imatinib or transplantation from January 4, 2004 to October 10, 2011 in the Department of Hematology at Guangdong General Hospital (GGH) were enrolled in this study. A total of 131 patients, including 90 and 41 in the imatinib and allo-HSCT groups, respectively, were enrolled. The two groups including HRQOL investigation were well matched for gender, marital status, employment status, educational background, and Sokal score at diagnosis. There were no significant differences in the five-year EFS, PFS and OS between the two groups. The HRQOL was measured using EORTC QLQ-C30. Those questions include five multi-item function scales (Physical, Role, Emotional, Cognitive and Social Functioning), a combined Global Health Status/QOL scale, and a number of individual items (appetite loss, dyspnea, diarrhea, constipation, sleep disturbances, and financial impact). In terms of HRQOL, with the exception of social functioning (64.9 vs. 77.5, P=0.035), there was no significant difference in many of the HRQOL scores between the imatinib and transplant groups: global HRQOL, role function, physical function, emotional function and cognitive function. However, symptoms including nausea/vomiting (14.8 vs. 3.2, P=0.013), diarrhea (18.4 vs. 2.5, P=0.001), and financial difficulty (56.9 vs. 33.3, P=0.023) more negatively impacted the imatinib group (P

Description: Background: Treatment for acute myeloid leukemia (AML) has remained relatively unchanged over the past few decades. Standard-dose cytarabine and idarubicin (7+3 IA) or daunorubicin (7+3 DA) induction regimen have been recommended for AML induction therapy by global guidelines. Mitroxantrone, a type II topoisomerase inhibitor, disrupts DNA synthesis and DNA repair, has been recommended as a salvage treatment for refractory/relapsed AML or induction therapy for elderly patients. Objective: To compare the the clinical response and adverse events of Idarubicin regimen ( IA) with mitoxantrone and cytarabine (MA) in the treatment of newly acute myeloid leukemia (AML) . Methods: This retrospective study evaluated 164 patients with newly diagnosed AML who received either IA (idarubicin 10mg/M2, d1-3; cytarabine 200mg/d, d1-7) or MA regimen (mitoxantrone 10mg/M2, d1-d3; cytarabine 200mg/d, d1-7) as induction therapy from September 2010 to November 2017 at Guangdong General Hospital. The primary end point of this study was complete response and complete response with incomplete blood count recovery (CR/CRi), with secondary end points were adverse event rates and days of granulocyte and platelet recovery. Results: A total of 164 patients , 90 patients were males and 74 females, the median age was 41 (range:14~64) years old. There were 88 patients received IA regimen and 76 patients received MA regimen. There was no significant difference in clinical features and molecular biological characteristics in two groups (P〉0.05). The CR/CRi rate was 72.3% and 64.0% (P=0.263) in IA and MA group after the first induction regimen, respectively. And the accumulated CR/CRi rate was 85.9% and 75.7% in two group, respectively (P=0.109). The common adverse reactions in the two groups were myelosuppression and infection , but with no statistical difference (P〉0.05) in the incidence and grade of serious. The grade 4 and grade 5 neutropenia were 95.3% vs.98.7% and 4.7% vs. 1.3%, P〉0.05 in IA and MA group respectively. And thrombocytpenia were 72.9% vs.63.2% and 4.7% vs. 1.3%, P〉0.05. There was no significant difference in the incidence and severity of gastrointestinal, cardiovascular, respiratory, skin, liver and kidney injury between the two groups (P〉0.05). The median days of intravenous antibiotics (including antifungal drugs), neutrophil recovery, platelet recovery and the units of platelet and red blood cell suspension transfusion had no statistical difference in two groups (P〉0.05). Conclusion: This retrospective study implied mitoxantrone with standard-dose cytarabine (3+7 MA) regimen has similar efficacy and outcome to the idarubicin with standard-dose cytarabine (3+7 IA) regimen for newly diagnosed AML, without increasing the incidence of adverse event rates. Disclosures No relevant conflicts of interest to declare.

Description: Abstract 4856 Objective The multiparametric flow cytometry is becoming a very useful tool of the diagnosis and prognostication for patients with Myelodysplastic Syndrome(MDS). This study was aimed at using multiparametric flow cytometry to explore the immunophenotypic abnormalities of bone marrow cells from patients with RAEB. Methods We collected BM samples from 12 MDS-RAEB patients (6 male, 6 female, Median Age 67.5) and 20 non-MDS patients (11 male, 9 female, median age 32.5, 7 AA, 5 PNH, 3 IDA, 1 ALL, 2 CML, 2 MM). The multiparametric flow cytometric analysis was performed using an extensive panel of monoclonal antibodies. We used the conventional and secondary gating strategies to analysis the BM cells compartments such as the percents of blast cells and the expression of lineage and maturation-associated antigens of BM hemopoietic cells quantified. Results Compared with the non-MDS group, the proportion of blast cells increased significantly in the MDS-RAEB group (P=0.001), but the percentages of nucleated erythrocyte, lymphocyte, monocyte and granulocyte were no significant difference (P=0.954, P=0.893, P=0.730 and P=0.182). As the percentage of blasts cells increasing, the survival time became shorter (13 ± 6 vs 35 ± 15 months; P=0.02). The expressions of haemopoietic stem/progenitor cell surface marker CD34+ and T lymphocyte surface marker CD7+ on blast cells were much higher by secondary gating method than non-MDS group (P=0.009, P=0.002, respectively), while no significant difference of the expression of CD56 (P=0.375). The expressions of CD7+ and CD56+ on lymphocyte were no significant difference between the two groups (P=0.195, P=0.369, respectively), however the expression of CD19+ may be different (P=0.039). The expressions of CD33+ and CD13+ on granulocyte were no significant difference between the two groups (P=0.289, P=0.744, respectively). However, the expression levels of CD15+CD11b+, CD15+CD11b-, CD10+, HLA-DR, CD56+ in the MDS-RAEB group were significantly higher than those in the non-MDS group, specially, the levels of CD10+, HLA-DR and CD56+ were much higher (P=0.016, P=0.011, P=0.005, P=0.005 and P=0.005, respectively) and these patients showed a shorter median overall survival (15 ± 5 vs 36 ± 10 months; p = 0.03). Conclusions The percentage of blast cells increased in MDS-RAEB patients and the expressions of CD34+, CD7+ on blast cells and the expressions of CD10+, HLA-DR and CD56+ on granulocyte is higher than non-MDS group. It will be necessary to increase the number of cases (MDS-RAEB) to confirm our findings. Using multiparametric flow cytometry can find the immunophenotypic abnormalities more sensitively, accurately and objectively, and this new approach could provide much more useful information in the diagnosis and prognosis of MDS-RAEB patients. Disclosures No relevant conflicts of interest to declare.

Description: Abstract 4673 Refractory chronic GVHD (cGVHD) is an important complication after allogeneic hematopoietic SCT and is prognostic of poor outcome. Bone Marrow Stromal Cells (MSCs) are involved in tissue repair and modulating immune responses in vitro and in vivo. MSCs as salvage treatment for refractory cGVHD have been reported in our previous study, however, the possible mechanism have yet not to be determined. Between November 2006 and November 2010, 18 patients were diagnosed with refractory cGVHD, 8 patients were treated with in vitro expanded BM-derived MSCs as a compassionate treatment for refractory cGVHD, 10 patients that did not receive BMSCs treatment were control group. The median MSC dose given was 0.6×106/kg body weight. MSCs were harvested fresh from culture and administered to the patients by intravenous infusions over 30 minutes. The median time of MSC administrations was 3 (range, 2–6). The response was assessed monthly after BMSCs treatment, and the total follow-up period was 6 months. The organ response and the overall response were used to determine the therapeutic efficacies of MSC for refractory cGVHD. The expression of the Jagged2 gene of peripheral blood mononuclear cells in patients at the assessment points were analyzed using the TaqMan real-time polymerase chain reaction, with ABL mRNA expression levels as an internal reference. After BMSCs treatment, a total of 6 patients (75%) had an overall response (PR n=6), and 2 patients had a minor partial response (mPR n=2). The expression levels of Jagged2 mRNA in these cases at the diagnosis of refractory cGVHD were significantly increased, compared with none cGVHD patients (23.94%±18.68% vs 3.76%±1.50%, P 〈 0.05), and the copies of Jagged2 mRNA in BMSC treatment responsed patients' peripheral blood were significantly reduced (5.15%±3.25%, P 0.05). Our pilot study showed that Jagged2 gene reproduction upregulated when the cGVHD is active, so, dynamic monitoring of Jagged2 mRNA expression may have the potential effect on predicting the activity of chronic graft-versus-host disease. Mechanism of Bone marrow stromal cells to treat refractory cGVHD may be related to down-regulation of donor T cells Notch ligand Jagged2 gene expression, which suppression of T cell Notch signaling pathway activation, thus inducing immune tolerance. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 4132 The objective was to definite the expression level of aven mRNA of white blood cells from peripheral blood(PB)of de novo acute myeloid leukemia and preliminary analyze its clinical significance, providing a experimental basis for evaluating prognosis. Aven mRNA levels in PB samples from 69 AML patients were detected by using real-time quantitative PCR. The relation of aven mRNA level with clinical and hematological characteristics (age, sex, WBC, Hb, Plt, LDH, Blast% in PB and BM,FAB subtype) and treatment outcome (complete remission rate and relapse rate)were analyzed. Twenty-one normal individuals served as controls. The level of aven mRNA was between 11.72% and 178.93 %(median 37.2%) in de novo AML and between 10.81% and 50.98 %(median 28.81%) in normal individuals. Aven mRNA level was higher in the AML group than in the controls (p=0.006). When we compared aven mRNA with other clinical and hematological parameters, there were significant correlations between aven mRNA and age(r=0.25,p=0.039),aven mRNA and hemoglobin level (r=0.29,p=0.019),aven mRNA and FAB subtype(r=0.253,p=0.036). We found that median level of aven mRNA in group whose age older than median age was higher than group whose age younger than median level(p=0.018).The complete remission rate after two cycles chemotherapy in group with lower aven mRNA level(25/30,83.33%)was higher than group with higher aven mRNA level(21/30,70%). But the difference was not significant(p=0.22).The difference of aven mRNA expression level between AML patients with relapse and that without relapse was not significant (p=0.076). In conclusions, the level of aven mRNA in de novo AML is overexpression. The overexpression of aven mRNA is likely to play an important role in tumorigenesis of AML. Association of aven mRNA expression with treatment outcome and relapse was not observed. Disclosures: No relevant conflicts of interest to declare.

Description: Background: Our preliminary research found that STAT3, IL-17A, and IL-21 expressed in cGVHD patients. So, we provide the blocking STAT3 signal to the induction of Treg cells differentiation, and to provide experimental basis on new targets of cGVHD immunotherapy. Methods: 1. Mice spleen CD4+ CD62L+ naiveT cells were separated by immune magnetic bead and then activated for 72 h. After 96 h infection with STAT3-shRNA and negative control lentivirus, the Th subgroup proportion were measured by flow cytometry. Th related cytokines levels test by Luminex. Real time quantitative PCR was to detect STAT3 and Th subgroup related transcription factor mRNA levels. CD117+ mouse bone marrow stem progenitor cells were sorted by flow cytometry, and transfected by STAT3-shRNA. Inhibition of STAT3 gene in mRNA level was measured at 96 h. Cell proliferation activity was test with CCK8 kit, and cell apoptosis rate determined by flow cytometry. Differentiation of CD117+ cells was induced by 2.2% of methyl cellulose and different cytokines. 2. BALB/c female mice, after the linear accelerator 700cGy of whole body irradiation, accepted miHA mismatched male B10. D2 mice bone marrow cells and spleen cells (8 x 106, 1:1). Randomly assigned 6 mice of cGVHD clinical score of 0.6 or above to each group. After STAT3-shRNA or negative control lentivirus treatment, the observe end point was 58th day after transplantation. The clinical and pathologic scores compared. Th17 and Treg cells measured by flow cytometry. Th related cytokines measured by Luminex. Purpose genes in blood and protein expression levels in target organs were found by Q-PCR and western blot test, respectively. Results: 1. The Th17 / Treg ratio of shRNA group was significantly decreased than that in the NC group (P 〈 0.05). Except for the Foxp3 gene, other purpose genes, including T-bet, Gata3, RORγt, TGFβ, Notch1, and Jagged2 mRNA levelsin interference group were cut. GM-CSF, IFN-gamma, beta, IL- 3, IL-2, IL-4, IL-6, TNF alpha, IL-17, IL-22a, IL-27, and IL-9 factor expression levels were significant difference between shRNA and negative control group (P 〈 0.05). There was no significant difference of cell proliferation activity, early apoptosis rate, and differentiation ability in STAT3-shRNA treated CD117+ bone marrow, compared with negative control group and blank control group (P 〉 0.05). 2. After 50th day, shRNA treatment group appear hair recovery, energy recovery, weight gain, shortness of breath better, mean of cGVHD score decreased. At the 58th day, clinical scores of cGVHD between shRNA treatment group and the negative control group overall mean difference was statistically significant (P 〈 0.05). cGVHD pathological score of lungs in shRNA treat group reduced (P 〈 0.05). STAT3mRNA levels in peripheral blood, phosphorylated STAT3, and STAT3 expression level of lung declined than control groups. The proportion of Th17 / Treg cells of spleen was significant reduced in shRNA group, compared with negative control group (P 〈 0.05). Conclusion: 1. STAT3 knocking down in naïve CD4 + Th cells induced the increased Treg cells, and the decreased Th17 cells. IL-2 confirmed to promote the growth of Treg cells. It speculated that blocking STAT3 might bring Th9 cells differentiation. STAT3 blocking in CD117+ stem progenitor cells have no significant effect on the proliferation, apoptosis and differentiation, validation the safety of STAT3-shRNA. 2. STAT3-shRNA treatment cGVHD mice in vivo achieved curative effect. The main target organs was the lung, which might be closely related to the fall in the proportion of Th17 /Treg. STAT3 may be used as a new target for immunotherapy of cGVHD. Acknowledgment The project was sponsored by grants from National Natural Science Foundation of China (No. 30972790; No.81270648; No.81370665; No.81300446), Provincial Natural Science Foundation of Guangdong (No. S2012010009560), Provincial Science and Technology Planning Project of Guangdong (No.2013B021800186; No.2013B021800201), and Science and Technology Planning Project of Guangzhou (No. 201400000003-4, 201400000003-1). Disclosures No relevant conflicts of interest to declare.

Description: Abstract 4721 Objective Nestin was detected in some tumor cells and nestin expression was positive relative with malignancy of glioma, angioma and melanoma. Nestin maybe was considered as marker of tumor malignancy and cell proliferation. There was no report about nestin expression in acute myeloid leukemia (AML) and acute lymphoblast leukemia (ALL). Herein, we describe the clinicopathological and immunohistochemical features of 48 patients with acute leukemia, introducing nestin as an additional marker that identifies these tumors .Meanwhile, Nestin and ki67 antigen expression were done to identify the relation of nestin and cell proliferation in AML, and the correlation between histoscore of nestin expression on leukemic blasts and patients' complete remission rate (CR) and overall survival (OS) was analyzed in AML. Methods Nestin and ki67 antigen expression in a series of 37 AML samples, 11 ALL samples, 2 multiple myeloma samples (MM) and 2 chronically myeloid leukemia samples (CML) were done with immunohistochemistry. Histoscore of nestin expression on leukemic blasts with AML and ALL was done and analyzed with independent t-test. The correlation of histoscore of nestin expression with patients' CR rate in AML was analyzed by the method of chi-square test. Patients' OS analysis was determined by the method of Kaplan and Meier, with log-rank analysis to estimate statistical significance in AML. P values of

Description: Xiaomei Chen and Jianyu Weng contributed equally to this study. The outcomes ofrelapsed or refractory acute myeloid leukemia (RR-AML) are poor and effective salvage regimens are urgently needed. We present a study of 14 patients with RR-AML (median age 42years, range 18-65years; male n=12, female n= 2) treated with CLAT regimen, which consisted of cladribine 5mg/m² per day i.v. 2-3 hour on days 1-5, cytarabine 1.0g/m² per day i.v. 4 hours after cladribine on days 1-5, topotecan 1.25mg/m² per day i.v. 4 hours after cytarabine on days1-5 and G-CSF 300ug per day subcutaneous injection on days until neutrophile granulocyte recovery. Total of fourteen patients were included into the study from June 2013 to June 2015, Two (14.3%) patients were relapsed and twelve (85.7%) patients were refractory, 4 of 14 patients were relapsed or refractory after allogeneic-HSCT. Two patients died of invasive fungal infection before the assessment. Seven patients (58.3%) achieved complete remission (CR), and one patient (8.3%) achieved partial remission (PR), the rest patients (33.3%) did not respond (NR). The overall response rate was 66.7%. Following CLAT treatment, four patients with CR underwent allogeneic hematopoietic stem cell transplantation (HSCT) or microtransplantation. The median relapse-free survival (RFS) for RR-AML patients receiving CLAT regimen was 8.6 (range 2-16) months. Thirteen patients developed grade 4 granulocytopenia and thrombocytopenia, the median duration was 13(range 2 to 21) days and12 (range 2 to 21) days, respectively. The most common non-hematological side effects included nausea, vomiting, diarrhoea, and were grade 1/2. The CLAT regimen seems promising for the treatment of patients, and it was well tolerated. This regimen offers an alternative treatment for those patients with RR-AML who have received severe intensive treatment, especially with anthracycline-containing chemotherapy. The project was sponsored by grants from National Natural Science Foundation of China (No. 30972790; No.81270648; No.81370665; No.81300446) Provincial Natural Science Foundation of Guangdong (No. S2012010009560) Provincial Science and Technology Planning Project of Guangdong (No.2013B021800186; No.2013B021800201), and Science and Technology Planning Project of Guangzhou (No. 201400000003-4, 201400000003-1). Disclosures No relevant conflicts of interest to declare.

Description: Patients with relapsed or refractory leukemia have less chances of obtaining remission than patients with newly diagnosed.It is reported that more than 80% of acute myeloid leukemia(AML) patients have myeloid blast cells that express the CD33 surface antigen. This antigen also is present on the leukemic stem cells at least some patients with chronic myeloid leukemia(CML)and acute lymphoblastic leukemia(ALL). It is absent from normal hematopoietic stem cells and nonhematopoietic cells and tissues. Gemtuzumab is a humanized anti-CD33 antibody conjugated to calicheamicin, a potent anti tumor antibiotic derived from a bacterium. It is conditionally approved in the US for treatment of CD33+ AML in first relapse in patients over 60 years[Sievers et al.Journal of Clinical Oncology,2001]. Here we evaluate the efficacy and safety of Gemtuzumab -based regimens. The study population comprise 11 patients with CD33-positive refractory leukemia (determined as CD33-antigen expression in over 50% of leukemic blasts by bone marrow aspirates and immunophenotyping), including two with myeloid blast phase of CML, one with refractory ALL, two relapsed after Auto-stem cell transplantation(Auto-SCT). The median age was 47 years. Four cases who were over 60 years or after Auto-SCT treated with single agent. The other seven cases treated with mylotarg and cytotoxic agents, including mylotarg plus idarubine (MI); Gemtuzumab plus fludarabine, cytarabine, CsA(MFAC); or plus mitoxantrone, Ara-C (MMA).The overall response rate was 54% (6/11), with 36%(4/11) patients obtaining complete remission (CR) and 18% (2/11) achieving CRp.The median overall survival time after treatment was 4.8 months, and the median overall survival time after CR was 8.2 months.Two patients with myeloid blast phase of CML achieved CR with BCR/ABL(−), the survival time after CR was 5+months and 20+months respectively, but failed in second relapse. One patient received Allo-SCT after CR with refractory ALL is still alive at present (21months) with disease free. The median time to ANC recovery of 0.5×109/L was 15 days.The common adverse events was myelosuppression (100% Grade 4 neutropenia and thrombocytopenia).Significant non-hematologic toxicitics included infection(96%), infusion-related chills and fever (55%).Although hepatic dysfunction and mucositis were observed,they were generally infrequent and not severe(Grade 1–2).Six patients (55%) developed Hepatic veno-occlusive disease(VOD), four of them were either over 60 years old or received Auto-SCT before although they received only single agent mylotarg therapy, but it was transient and no one died from it. In conclusion, patients with CD33-positive refractory leukemia, Gemtuzumab -based regimens have a comparable response rate and offer a more favorable toxicity profile, expecially for the patients with myeloid blast phase of CML. It is also effective for the patient with refractory ALL. In the treatment, we should pay attention to the hepatic condition of ones who are over 60 years old or after stem cell transplantation, attemps to avoid and treat VOD are warranted. Above all, When patients with refractory leukemia got remission, allogenic-SCT should be done as soon as possible