ALBERT

Description: We prove that the SH2-containing tyrosine phosphatase 1 (SHP-1) plays a prominent role as resistance determinant of imatinib (IMA) treatment response in chronic myelogenous leukemia cell lines (sensitive/KCL22-S and resistant/KCL22-R). Indeed, SHP-1 expression is significantly lower in resistant than in sensitive cell line, in which coimmunoprecipitation analysis shows the interaction between SHP-1 and a second tyrosine phosphatase SHP-2, a positive regulator of RAS/MAPK pathway. In KCL22-R SHP-1 ectopic expression restores both SHP-1/SHP-2 interaction and IMA responsiveness; it also decreases SHP-2 activity after IMA treatment. Consistently, SHP-2 knocking-down in KCL22-R reduces either STAT3 activation or cell viability after IMA exposure. Therefore, our data suggest that SHP-1 plays an important role in BCR-ABL–independent IMA resistance modulating the activation signals that SHP-2 receives from both BCR/ABL and membrane receptor tyrosine kinases. The role of SHP-1 as a determinant of IMA sensitivity has been further confirmed in 60 consecutive untreated patients with chronic myelogenous leukemia, whose SHP-1 mRNA levels were significantly lower in case of IMA treatment failure (P 〈 .0001). In conclusion, we suggest that SHP-1 could be a new biologic indicator at baseline of IMA sensitivity in patients with chronic myelogenous leukemia.

Description: The cancer testis antigen (CTA) preferentially expressed antigen of melanoma (PRAME) is overexpressed by many hematologic malignancies, but is absent on normal tissues, including hematopoietic progenitor cells, and may therefore be an appropriate candidate for T cell–mediated immunotherapy. Because it is likely that an effective antitumor response will require high-avidity, PRAME-specific cytotoxic T lymphocytes (CTLs), we attempted to generate such CTLs using professional and artificial antigen-presenting cells loaded with a peptide library spanning the entire PRAME protein and consisting of 125 synthetic pentadecapeptides overlapping by 11 amino acids. We successfully generated polyclonal, PRAME-specific CTL lines and elicited high-avidity CTLs, with a high proportion of cells recognizing a previously uninvestigated HLA-A*02–restricted epitope, P435-9mer (NLTHVLYPV). These PRAME-CTLs could be generated both from normal donors and from subjects with PRAME+ hematologic malignancies. The cytotoxic activity of our PRAME-specific CTLs was directed not only against leukemic blasts, but also against leukemic progenitor cells as assessed by colony-forming–inhibition assays, which have been implicated in leukemia relapse. These PRAME-directed CTLs did not affect normal hematopoietic progenitors, indicating that this approach may be of value for immunotherapy of PRAME+ hematologic malignancies.

Description: Providing a proliferative and survival advantage to tumor-specific cytotoxic T lymphocytes (CTLs) remains a challenge in the adoptive therapy of cancer patients. It is now evident that the in vivo expansion of T cells after adoptive transfer is best accomplished in the lymphodepleted host due to the increased production of endogenous IL15 and IL7, which help restore lymphopoiesis. We have found that antigen activated cytotoxic T lymphocytes (CTLs) directed to tumor associated epitopes (for example derived from EBV, or from cancer testis antigens such as PRAME) down regulate a chain of IL7R, a common γ chain cytokine receptor, impairing their capacity to respond to IL7. We hypothesized that despite receptor downregulation, the signal transduction pathway for IL7R would remain intact in the CTLs so that forced expression of IL7Rα would restore IL7 responsiveness and improve in vivo expansion and survival of CTLs. We used EBV-specific CTLs as our model, and showed in vitro that a functional IL-7Ra molecule can be expressed in CTLs using retroviral gene transfer so that the percentage of receptor + cells increased from 2.4%±0.5% to 50%±20. This modification restored the in vitro proliferation of genetically modified CTLs in response to IL7 so that cell numbers increased from 1×106 cells to 0.1×109 (range, 0.6×108 to 0.3×109)] comparable with the effects of IL2 [from 1×106 cells to 0.7×109 (range, 0.7×107 to 1.6×109)] In contrast, control EBV-CTL with IL7 progressively declined in number (p

Description: Modification of primary T cells to express chimeric antigen receptors (CARs) is an attractive strategy for the generation of tumor-specific T cells for adoptive therapies. However, their efficacy is limited by poor expansion within the tumor microenvironment. The addition of co-stimulatory endodomains, such as CD28, to the CAR may enhance cell expansion in response to the antigen, but cell growth and survival remain suboptimal since the co-stimulation provided through these endodomains cannot recapitulate the spatiotemporal sequence of signals T cells receive during physiologic activation. To further potentiate the expansion and survival of CAR-modified T lymphocytes, we generated a new vector encoding 3 molecules: CAR.19 incorporating the CD28 endodomain, codon optimized hIL15 to enhance cell survival and growth, and an inducible suicide gene based on the expression of Caspase9 (iCasp9) to increase the margin of safety associated with transgenic expression of an autocrine growth factor. These three sequences were linked using 2A-like peptide sequences. We compared the proliferative capacity, cytotoxic activity and in vivo anti-tumor effects of T lymphocytes expressing either CAR.19-28z alone or CAR.19-28z, IL15 and the suicide gene. T lymphocytes were activated with OKT3/CD28 antibodies and then transduced with retroviral supernatants. Phenotypic analysis showed 70±10% and 75±5% transduction efficiency for iCasp9/CAR19-28z/IL15 and CAR19-28z T cells, respectively. Only the iCasp9/CAR19-28z/IL15 T cells produced IL15 (〉100pg/mL) after stimulation with CD19+ tumor cells. In co-culture experiments, T cells expressing CAR.19-28z alone or iCasp9/CAR19-28z/IL15 both completely eliminated CD19+ tumor cells within 72 hours. However, labeling with carboxyfluorescein diacetate succinimidyl ester (CFSE) showed that the proliferation of the iCasp9/CAR19-28z/IL15+ T cells in response to CD19+ tumor cells was greater than that of CAR.19-28z control+ T cells. Finally, the activation of the suicide gene iCasp9 with a small-molecule dimerizer (CID 50ng/mL) rapidly induced 〉90% apoptosis of T cells expressing iCasp9/CAR19-28z/IL15. Hence all three transgenes were functional. To assess the antitumor effects of the modified cells in vivo, we used a xenograft SCID mouse model and an in vivo bioluminescence system. CD19+ Daudi cells (1×106) expressing firefly Luciferase (FL) were injected i.p., and on day 4, mice received i.p iCasp9/CAR19-28z/IL15+ or CAR19-28z+ or control T cells (10×106). By day 30 the tumor signal was significantly reduced in mice receiving iCasp9/CAR19-28z/IL15+ T cells (ROI2.0×109). In conclusion, our data indicate that a tricistronic vector can effectively be expressed in tumor-redirected human T cells, improving their survival and allowing their destruction should unwanted effects occur.

Description: The antitumor effect of adoptively transferred tumor-specific cytotoxic T lymphocytes (CTLs) is impaired by the limited capacity of these cells to expand within the tumor microenvironment. Administration of interleukin 2 (IL-2) has been used to overcome this limitation, but the systemic toxicity and the expansion of unwanted cells, including regulatory T cells, limit the clinical value of this strategy. To discover whether transgenic expression of lymphokines by the CTLs themselves might overcome these limitations, we evaluated the effects of transgenic expression of IL-2 and IL-15 in our model of Epstein Barr Virus–specific CTLs (EBV-CTLs). We found that transgenic expression of IL-2 or IL-15 increased the expansion of EBV-CTLs both in vitro and in vivo in a severe combined immunodeficiency disease (SCID) mouse model and enhanced antitumor activity. Although the proliferation of these cytokine genes transduced CTLs remained strictly antigen dependent, clinical application of this approach likely requires the inclusion of a suicide gene to deal with the potential development of T-cell mutants with autonomous growth. We found that the incorporation of an inducible caspase-9 suicide gene allowed efficient elimination of transgenic CTLs after exposure to a chemical inducer of dimerization, thereby increasing the safety and feasibility of the approach.

Description: The cancer testis antigen (CTA) preferentially expressed antigen of melanoma (PRAME) is overexpressed in many hematologic malignancies, including chronic myeloid leukemia (CML). The sensitivity of CML to donor lymphocyte infusion after allogeneic stem cell transplantation suggests this tumor can be highly susceptible to cellular immunotherapy targeted to tumor associated antigens. We therefore tested whether functional PRAME-specific cytotoxic T lymphocytes (PRAME CTLs) could be generated and expanded from healthy donors and CML patients, or whether the limited immunogenicity of this CTA coupled with tumor-associated anergy would preclude this approach. Using optimized culture conditions and HLA-A*02–restricted PRAME-peptides, we have consistently generated PRAME CTLs from 8/9 healthy donors and 5/6 CML patients. These CTLs released IFNγ in response to PRAME peptides (between 113 ± 8 and 795 ± 23 spot forming cells/105 T cells) and lysed PRAME peptide–loaded cells (45 ± 19% at an effector:target [E:T] ratio of 20:1) in a MHC-restricted fashion. Importantly, these CTLs recognized and had cytotoxic activity against HLA-A*02+/PRAME+ tumor cell lines, and could recognize and respond to primary CML cells. PRAME CTLs were generated almost exclusively from the naive T-cell compartment, and clonal analysis showed these cells could have high αβTCR-peptide avidity. PRAME CTLs or vaccines may thus be of value for patients with CML.

Description: Background: T-cell depleted haplo-HSCT is an established treatment for children with primary immune deficiencies (PID). However, children given this type of allograft are exposed to the risk of fatal events due to viral infections because of the prolonged impairment of adaptive immunity. We recently developed a novel method of selective T-cell depletion based on physical elimination of α/β T cells (ClinicalTrial.gov identifier: NCT01810120), which was shown to be safe and more effective than transplantation of positively-selected CD34+ cells for preventing life-threatening infections. However, we recorded some severe and even fatal viral infections, which prompted us to explore innovative approaches to accelerate the recovery of adaptive immunity. For this purpose, we designed an ongoing phase I/II trial aimed at testing the safety and the efficacy of post-transplant infusion of BPX-501 cells in children with malignant or non-malignant disorders (ClinicalTrials.gov identifier: NCT02065869). We report 3 cases of children with either severe combined immune deficiency (SCID) or Wiskott-Aldrich syndrome (WAS), who were enrolled in the dose escalation phase of the study and who cleared cytomegalovirus (CMV) or Adenovirus (AdV) infections likely due to the contribution of the BPX-501 cells. Patients and methods: Patient #1, affected by SCID, was transplanted from the HLA-haploidentical father. Before transplantation she had CMV-DNAemia which was treated with ganciclovir until donor stem cell infusion. She was given 2.5 x 105/kg BPX-501 cells on day 17 after transplantation. Patient #2, also affected by SCID, was transplanted from the HLA-haploidentical mother. Before transplantation she had AdV-DNAemia and high load of the virus in stools. She was given 5 x 105/kg BPX-501 cells on day 15 after transplantation. Patient #3 was affected by WAS and referred to the transplant unit; in the months preceding haplo-HSCT the child had developed CMV retinitis and hepatitis with high levels of CMV-DNAemia. This patient was transplanted from the father and received 1 x 106/kg BPX-501 cells on day 15 after haplo-HSCT. Basic phenotype of circulating lymphocytes was assessed by flow cytometry on fresh heparinized peripheral blood samples at 10, 20, 30, 60, 90, 120 and 150 days post haplo-HSCT, respectively. Since BPX-501 cells are CD3+/CD19+, it was easy to track the presence of these genetically modified cells. CMV specific reconstitution was also monitored through the INF gamma ELISPOT assay. In particular, peripheral blood mononuclear cells were stimulated for 16hrs in the presence of peptide libraries derived from pp65, IE1 and IE2 CMV-specific antigens. Results: The increase in the number of both CD3+ T lymphocytes and BPX-501 cells over time after transplantation together with the modifications of DNAemia of both CMV and AdV in the 3 patients are reported in Panel A, B and C, respectively, of Figure 1. In all of these patients, the pre-existing viral infection was progressively cleared once the BPX-501 cells were infused. These cells expanded in vivo and are still persisting, contributing to the recovery of adoptive immunity. The median time to reach an absolute number of α/β CD3+ cells greater than 0.5x109/L was 90, 90 and 30 days, respectively. None of these patients experienced either acute or chronic Graft-versus-Host Disease (GvHD) and no organ inflammatory-related toxicity was recorded. All children are alive and disease free, without infections, at day +200, +180 and +160, respectively. The 2 patients with CMV infection showed a specific response for at least one CMV-derived antigen; indeed, one patient showed a prevalence in pp65 response, whereas in the second one, we observed a specific anti-CMV response against all three tested antigens (Figure 1 - Panel D). Conclusions: Infusion of BPX-501 cells is able to accelerate the recovery of adaptive T-cell immunity in children with PID given haplo-HSCT after depletion of α/β T cells, thus rendering the procedure safer even in children with active infections at time of transplantation. These cells, once infused, expand in vivo and persist over time, contributing to the clearance of viral infections, without inducing GvHD. Figure 1. Figure 1. Disclosures Moseley: Bellicum Pharmaceuticals: Employment, Equity Ownership.

Description: Introduction Tyrosine Kinase Inhibitors (TKI) have completely changed the scenario of CML and dramatically improved the outcomes. Thus, early identification of patients expecting poor outcome is crucial to offer alternative TKI regimens or in some selected cases stem cell transplantation before disease progression may occur. The Evaluating Nilotinib Efficacy and Safety in Trial as First-Line Treatment (ENEST1st) is a phase 3b is an open-label study of nilotinib 300 mg twice daily (BID) in adults with newly diagnosed BCR-ABL positive CP-CML. Aim of the ENEST1st sub-study N10 was to investigate BM microenvironment markers that regulate leukemic stem cells in the bone marrow (BM) niche of Nilotinib-treated patients. Methods The study enrolled patients in 21 Italian ENEST1st participating centers. Response was based on ELN recommendations (Baccarani M, et al. Blood 2013 122:872-884). In an interim analysis, molecular and cytogenetic response by 24 months was assessed. Mononuclear cells were collected from BM and PB samples at the screening visit (V0) and after 3 months of treatment (V4). RT-qPCR for the expression of 10 genes (ARF, KIT, CXCR4, FLT3, LIF, NANOg, PML, PRAME, SET and TIE), involved in the stemness and hematopoietic stem cells survival signaling regulation was conducted. RT-qPCR data were normalized by the expression of GUS mRNA (normalized copy number, NCN). Plasma samples were collected at different time points from both BM or PB samples. Concentrations of 20 different analytes, including IL-1a, IL-3, M-CSF, SCF, SDF1-a, TRAIL, HGF, PDGF-bb, IL1b, IL-6, IL-7, IL-8, IL-10, IL-12, IL-15, G-CSF, GM-CSF, MIP-1a, TNF-a, and VEGF, were simultaneously evaluated using commercially available multiplex bead-based sandwich immunoassay kits. Results 33 out of 37 patients enrolled were available for an interim molecular analysis at 24 months: an optimal response was achieved in 25 patients, a warning response in 5 patients and a failure response in 3 patients. We observed a significant correlation between the expression of two genes involved in the regulation of stem cell pluripotency (NANOg) or cytokine signaling (SET) and patient outcome. Indeed, NANOg and SET mRNA were significantly down-regulated in PB samples at diagnosis of patients with optimal response compared to patients with warning/failure response (NANOg mRNA: 0.3±0.25 NCN vs 0.6±0.7 NCN, respectively; p=0.05; SET mRNA: 0.2±0.3 NCN vs 2.3±4.2 NCN, respectively; p=0.03). We also investigated the plasma level of several factors involved in the hematopoietic stem cells (HSCs). Some of these markers showed a significant correlation with patient's outcome when evaluated at diagnosis in either PB or BM samples. Indeed, high level of IL12 (in the BM samples), or HGF, mCSF and SCF (in the PB samples) were associated to a worst prognosis markers, since significantly correlating with no MMR@12months (IL12, p=0.03), intermediate/high Socal score (mCSF, p=0.03; SCF, p=0.03), no reduction of MMR below to 1 at 3 month (SCF, p=0.04) or warning/failure response to Nilotinib treatment (HGF, p=0.03; SCF, p=0.04). Indeed, we find a lower levels of PDGFb, SDF1, TNFa, TRAIL (in the BM samples), and HGF, SDF1, TRAIL (in the PB samples) in those patients with intermediate/high Hasford or Sokal score (PDGFb, p=0.0007; SDF1, p=0.02), warning/failure response to Nilotinib treatment (HGF, p=0.03) or lacking of MMR4.0 (SDF1, p=0.01; TNFa, p=0.02; TRAIL, p=0.05). Conclusion/Summary Taken together, our results suggest that the expression analysis of genes involved in cell pluripotency (NANOg) and/or cell signaling (SET) at baseline, may indicate early achievement of deep molecular response in shown CML-CP patients treated with nilotinib. In addition, in patients with optimal response to Nilotinib, high concentration of SDF-1, TRAIL (inversely correlated with BCR-ABL, and associated to an higher susceptibility to apoptosis in the leukemic blasts) were observed as well as BM TNF (cell-extrinsic and potent endogenous suppressor of HSC activity). A lower concentration of several factors associated to hematopoietic progenitor cell growth and survival (including HGF, SCF and IL12) were observed compared to patients failing to achieve response to Nilotinib. These data strongly suggest that stromal microenvironment supports the viability of BCR-ABL cells in BM niches through direct feeding, or environment releasing of survival factors. Disclosures Soverini: Novartis, Briston-Myers Squibb, ARIAD: Consultancy. Martinelli:MSD: Consultancy; BMS: Speakers Bureau; Roche: Consultancy; ARIAD: Consultancy; Novartis: Speakers Bureau; Pfizer: Consultancy. Saglio:Bristol-Myers Squibb: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; ARIAD: Consultancy, Honoraria; Novartis Pharmaceutical Corporation: Consultancy, Honoraria. Galimberti:Novartis: Employment. Giles:Novartis: Consultancy, Honoraria, Research Funding. Hochhaus:Pfizer: Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding; ARIAD: Honoraria, Research Funding; Novartis: Honoraria, Research Funding.

Description: Background: Immune recovery is crucial for patients treated with allogeneic HSCT and in particular of those receiving a T-cell depleted haplo-HSCT. We recently developed a novel method of graft manipulation based on physical elimination of α/β T cells and B-lymphocytes for preventing graft-versus-host disease (GvHD) and EBV-related lymphoproliferative disorders, respectively. Thanks to this approach, we successfully conducted a prospective trial in children with malignant or non-malignant disorders (ClinicalTrial.gov identifier: NCT01810120). Although patients enrolled in this trial had faster immune recovery and lower incidence of infections than those given haplo-HSCT after infusion of positively selected CD34+ cells, reconstitution of adaptive T-cell immunity remains suboptimal. We therefore designed a phase I/II trial aimed at testing the effect on post-transplant immune recovery of adoptive infusion (within 14 + 4 days after transplantation) of BPX-501 cells in children given haplo-HSCT after depletion of α/β T and B cells (ClinicalTrials.gov identifier: NCT02065869). Patients and methods: As of July 25th 2015, 23 children have been infused with BPX-501 cells. The 9 children included in the phase I portion of the study were given 2.5x105, 5x105, and 1x106 BPX-501 cells/kg, respectively, while the 14 included in the phase II received 1x106 BPX-501 cells/kg. This analysis refers to the 16 patients with a minimum follow-up of 90 days; 7 children had acute leukemia and 9 non-malignant disorders. Basic phenotype of circulating lymphocytes was assessed by flow cytometry on fresh heparinized peripheral blood samples at 10, 20, 30, 60, 90, 120 and 150 days post haplo-HSCT, respectively. The following antibodies were used: anti-TCRαβ FITC/anti-TCRγδ PE/anti-CD3 PerCP-Cy™5.5 (WT31, 11F2, SK7), anti-CD4 APC Cy7 (RPA-T4), anti-CD19 BV 510 (SJ25C1), anti-CD3 BV 421 (UCHT1), anti-CD56 PeCy7 (B159), anti-CD16 APC (B73.1), anti-CD8 APC (RPA-T8) from BD Biosciences (San Diego, CA, USA). Antigen-driven activation of peripheral mononuclear cells was evaluated by standard lymphoproliferation assay (LPA) with 3H-thymidine pulsing on day 4 and harvesting 18 hours later. Antigens included PHA or CMV, EBV and AdV whole viral lysate. Results were scored positive with stimulation indexes (SI) 〉10 for PHA and 〉3 for viral antigens. Results: None of the patients died from transplant-related complications. Chimerism analysis investigated through short tandem repeats showed that in all but 4 patients, cells were of donor origin before the infusion of BPX-501 cells. In the 4 patients, there was a reversion to complete donor chimerism after infusion of BPX-501 cells. At early time points after haplo-HSCT, gδ T cells predominated over αβ T lymphocytes; subsequently, this latter population became the more largely represented. The number of both CD3+ T lymphocytes and of BPX-501 cells is shown in Panel A of Figure 1, reconstitution of whole T cells in historical children given haplo-HSCT after depletion of α/β T cells is also shown. The number of CD3+ T lymphocytes reached greater than 0.5x109/L 2 months after infusion of BPX-501 cells. Remarkably, while usually immune recovery after transplantation is characterized by prevalence of CD8+ cells, in our patients the physiological predominance of CD4+ lymphocytes was maintained (Panel B of Figure 1. Reconstitution of natural killer cells (NK) is shown in Panel C of Figure 1. As compared to patients receiving CD34+ selected cell haplo-HSCT, children included in this study had a faster reconstitution of mature KIR+/NKG2A- NK cells. Serum levels of IgA and IgM over time are shown in Panel D of Figure 1: there was a recovery of newly synthetized Ig at 3 months. The analysis of the function of T cells showed that the proliferative response to a polyclonal mitogen or to CMV lysate was comparable to that of a healthy control in 50% of patients as early as day + 60 after haplo-HSCT and BPX-501; on day +150, all patients reached a normal SI. Response to both EBV and AdV antigens was slightly delayed, but progressively improved over time (see also Figure 2). Conclusions: Overall, these data indicate that infusion of BPX-501 cells is able to accelerate the recovery of adaptive T-cell immunity since these cells, once infused, expand in vivo and persist over time, potentially contributing to protect patients from infections. Figure 1. Figure 1. Figure 2. Figure 2. Disclosures Moseley: Bellicum Pharmaceuticals: Employment, Equity Ownership.

Description: Abstract 2212 Poster Board II-189 Treatment of Chronic Myeloid Leukemia (CML) has shown an outstanding progress while new understanding of the disease has increased significantly. Nevertheless in the era of targeted therapy, Sokal index remains a dominant prognostic determinant of newly diagnosed CML patients. Our study has aimed to identify novel prognostic indicators to improve both an initial assessment and subsequent monitoring of CML patients. Initially, we have found that the protein-tyrosine phosphatase SHP1, that has a tumour suppressor activity, may play an important role in the resistance to imatinib treatment. We applied gene profiling and proteomic bidimensional electrophoresis to compare the differential pattern of gene and protein expression between KCL22s (imatinib-sensitive) and KCL22r (imatinib-resistant) cell lines. We found SHP1 to be one of the most differentially expressed genes. By ESI-TRAP MS technique, we found that one of the main interactors of SHP1 is SHP2, a protein phosphatase well known as positive regulator of oncogenic pathways, including the Ras/MAPK pathway. Gain-of-function mutations in SHP2 gene, have been described in various haematopoietic neoplasias and myeloproliferative disorders including Juvenile Chronic Myelomonocytic Leukemia. This protein is regulated throw phosphorylation on 542- and 580-Tyr, and unlike SHP1, acts as a positive regulator of the same oncogenic pathways. We found that KCL22r cell line, that has low SHP1 levels, showed complete phosphorylation of both SHP2 tyrosine residues, while these residues are not phosphorylated in the KCL22s line, which could explain an important mechanism for imatinib sensitivity. Consistently with this hypothesis, knock-down of SHP2 phosphatase in KCL22r by a specific shRNA resulted in 60% inhibition of KCL22r proliferation. Furthermore, the KCL22rSHP2- cells showed significant reduction in STAT3 (60%) and ERK1/2 (70%) phosphorylation. Our initial results from CML patients (Esposito et al , ASH 2008 Abs 1106) have suggested a differential expression of SHP1 in patients with different response to imatinib treatment. To further explore the role of SHP1 as a determinant of imatinib sensitivity we evaluated the expression of SHP1 in 93 newly-diagnosed CML patients enrolled into the TOPS trial investigating 400mg versus 800mg imatinib (Cortes et al, EHA 2008). The results of this study indicate that the mRNA levels of SHP1, as assessed by QPCR in peripheral blood of patients at the time of enrolment, are significantly different between patients who do or don't achieve Major Molecular Response (MMR) by 12 months (7.9±4.0 vs. 5.9±3.4; p=0.01). Logistic regression was used to estimate regression coefficients and corresponding odds ratio using MMR by 12 months as outcome variable in our model. Since the 25th and 75th percentiles of SHP1 were 4.3 and 8.4, respectively (resulting in an interquartile range of 4.1), statistical analysis shown that a value of 4.1 or more in SHP1 is associated with almost 2-fold odds of achieving MMR by 12 months (OR=1.92; 95% CI=1.12, 3.29; p=0.018). Moreover, in a contingency table, chi-square analysis has been shown a high risk of not achieving MMR by 12 month in those patients with either low SHP1 expression and high Sokal score, when compared with patients with high-intermediate SHP1 expression and low-intermediate Sokal score (p=0.0068). In conclusion, these results suggest that, measuring expression levels of SHP1 could be of value in assessing newly diagnosed CP-CML patients and estimating treatment response, which could help optimizing Gleevec treatment, or recommending patients to more potent TKIs. Supported by Novartis Oncology, Clinical Development, TOPS Clinical Correlative Studies Network Disclosures: Saglio: Novartis: Honoraria; Celgene: Honoraria. Pane:Novartis: Research Funding; Ministero dell'Università/PRIN: Research Funding; Regione Campania: Research Funding; Ministero della Salute/Progetto integrato Oncologia: Research Funding.