Generation To Tyrosine Kinase Inhibitors Research Articles

Abstract 5843: Exploring the implications of LPAR-1 expression in TKI-resistant NSCLC

Abstract Introduction: Non-small cell lung cancer (NSCLC) is the most common type of lung cancer in the United States with a 5-year survival rate hovering between 20-30%. Mutations in EGFR can initially cause the tumors to respond to tyrosine kinase inhibitors (TKI). Osimertinib, a third generation TKI, is the preferred first or second line of treatment and despite being effective, recent reports indicate that patients develop resistance within 10-18 months of treatment. TKI resistance limits therapeutic options for patients and therefore, alternative strategies are being explored. In this context, Lysophosphatidic acid receptors (LPARs), a family of G-protein coupled receptors consisting of LPARs 1-6 expressed differentially in prostate, breast, ovarian, pancreatic, and brain cancers are being explored as potential targets for drug resistant cancers. Specifically, LPAR-1 has been shown to play a role in tumor cell clonogenicity, migration, and response to therapy in EGFR mutant NSCLC cells. Pharmacological inhibition or CRIPSR based deletion of LPAR-1 in EGFR mutant NSCLC cell lines HCC827 and NCI-H3255, increased TKI sensitivity by reducing clonogenic potential. Further, detailed pathway analysis in TKI sensitive and resistant EGFR mutant cell lines suggests that LPAR-1 expression influences drug sensitivity. Surprisingly, the role of LPAR-1 in TKI sensitivity is not well understood. In the present study, we have performed detailed investigation on the implications of LPAR-1 expression in the development of Osimertinib resistance. Methods: Osimertinib resistant EGFR mutant cell lines (OR) were generated using dose-escalation method and drug-tolerant persisters (DTPs) were generated using a short-term high exposure method. Gene and protein expressions were examined using qPCR and western blotting. Subcutaneous tumor cell derived xenografts were generated for in vivo studies. Results: LPAR-1 is downregulated in Osimertinib resistant NSCLC cells. Further, we also observe that LPAR-1 levels are lower in DTP cells, confirming a progressive loss of LPAR-1 with Osimertinib treatment. In vivo studies in cell derived xenografts correlated with the in vitro studies. Conclusion: Our studies indicate LPAR-1 downregulation correlates to Osimertinib resistance in EGFR mutant NSCLC cell lines. LPAR-1 downregulation has a key role in development of Osimertinib resistance. Future studies will focus on delineating LPAR-1 signaling pathways related to TKI resistance and investigating the effect of LPAR-1 overexpression using CRISPR technology. Citation Format: Varsha Srinivasan, Zhaohui Li, Raghuraman Kannan, Anandhi Upendran. Exploring the implications of LPAR-1 expression in TKI-resistant NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5843.

Clinical outcomes of patients with advanced NSCLC with different EGFR exon 19 deletion subtypes treated with first-line tyrosine kinase inhibitors.

e21034 Background: Epidermal growth factor receptor (EGFR) exon 19 deletion (Ex19del) in non-small cell lung cancer (NSCLC) consists of many subtypes, and their sensitivity to tyrosine kinase inhibitors (TKIs) has not been clearly defined. This study aimed to investigate the clinical outcomes of advanced NSCLC patients with different EGFR ex19del subtypes treated with different TKIs. Methods: We retrospectively analyzed stage IIIB-IV NSCLC patients with EGFR Ex19del and first-line TKIs therapy. E746_A750del was defined as classic group, and the others as non-classic group, which was further divided into subgroups according to deletion with or without insertion, starting codon or length of deletion. The primary endpoint was progression free survival (PFS). Results: There were 17 Ex19del subtypes identified in 101 patients. The frequency of E746_A750del was 64.4% (65/101), and the top three frequent non-classic subtypes were L747_T751del (6.9%, 7/101), L747_P753delinsS (5.9%, 6/101) and E746_S752delinsV (5.0%, 5/101). In all patients, the median PFS (mPFS) of first-line TKIs in classic and non-classic groups were 14.3 months (m) and 19.3 m ( p > 0.05). In non-classic group, the mPFS in deletion with insertion (delins) and without insertion subgroups were 25.3 m and 11.2 m; in deletion starting with E746 and with other codon subgroups were 29.7 m and 19.3 m; and in deletion length of 15 nucleotides (n) and of other length subgroups were 11.2 m and 25.3 m. The mPFS of these non-classic subgroups were not statistically different with that of classic group ( p > 0.05). In all patients, the mPFS of first-line therapy with the 1st, 2nd and 3rd generation TKIs were 17.4 m, 15.6 m and 20.5 m, respectively ( p＞0.05); in classic group, the mPFS were 14.3 m, 16.9 m and 20.5 m, respectively ( p＞0.05). However, in non-classic delins subgroup (29.7 m, 15.6 m and 11.9 m) and in deletion length of ≥18 n subgroup (25.3 m，12.3 m and 11.9 m), the 1st generation TKIs had an insignificantly longest mPFS ( p＞0.05). When resistant to 1st or 2nd generation TKIs, patients in classic group showed a trend of higher incidence of T790M mutation than non-classic group (72.0% vs 43.8%, p = 0.070). In multivariant analysis, pleural metastasis (PM) had interaction with Ex19del grouping, warranting stratification analysis. In patients without PM, the mPFS of first-line TKIs in classic group was significantly shorter than non-classic group (13.8 m and 29.7 m, p = 0.026). However, in patients with PM, the mPFS of classic group was numerically longer than non-classic group (16.9 m and 11.7 m, p > 0.05), with the shortest mPFS in non-classic without insertion subgroup, and in non-classic with 15 n deletion subgroup. Conclusions: In advanced NSCLC patients with EGFR Ex19del, the efficacy of first-line TKIs therapy was affected by the presence of pleural metastasis, Ex19del subtypes and different generation of TKIs.

Kinase Domain Mutation Testing and Clinical Outcome in a Nationwide Chronic Myeloid Leukemia Patient Population

Background: ABL1 kinase domain mutations (KDM) are associated with resistance to tyrosine kinase inhibitors (TKI) and inferior outcome in chronic myeloid leukemia (CML) patients. Current guidelines recommend KDM testing in case of failure or resistance during TKI treatment. In this analysis, we aimed to assess (1) the clinical practice of KDM testing in the Netherlands, (2) the observed responses to subsequent TKI in the presence of a KDM in relation to the in vitro half-maximal inhibitory concentration (IC50)-values, and (3) the clinical outcome of patients for whom KDM testing was done. Methods: Data were obtained from a nationwide population based CML registry (Pharos-HemoBase) and six CML-reference centers in the Netherlands. We included adult Ph+ CML patients who were treated with a TKI and who had at least one KDM analysis after December 2005, when second generation TKI became available in the Netherlands. Reasons for KDM testing were categorized in three main groups based on the pattern of TKI failure: (1) primary resistance (no response), (2) suboptimal response and (3) loss of response. A suboptimal response was defined as failure to achieve the ELN response milestones, but with the achievement of at least 1-log BCR::ABL1 reduction. Loss of response was defined as losing a previously achieved ELN response milestone. A cox regression model was used for the survival analysis. Results: A total of 391 KDM analyses performed in 275 patients between December 2015 and March 2022 were included. When focusing on CP CML, most KDM analyses were performed because of a suboptimal TKI response (n=155), however in only nine (6%) a KDM was detected. In patients with primary TKI resistance, a KDM was detected in 17 of 81 analyses (21%). The highest yield of KDM was in patients losing a previously achieved response with 43 of 89 (49%) of analyses showing a mutation. Twenty-five KDM analyses were performed outside the context of TKI failure (e.g. BCR::ABL1 fluctuations but no loss of MMR, molecular relapse after a TFR attempt) and in none of them a mutation was detected. In total, 84 KDM were detected (panel A). Sixty-nine (25%) patients harbored at least one KDM of whom 24 the T315I mutation and eight a compound mutation. Most KDM analyses were done with Sanger Sequencing (SS). Fifty-four TKI treatment lines were assessable for response for patients who harbored a KDM with known in vitro IC50-values for predicted effectiveness of TKI. Of the patients who were treated with a TKI with a good predicted response, 34 of 42 (81%) indeed obtained a durable major molecular response, while seven patients experienced failure (4 no response, 3 loss of response). In patients who were treated with a TKI for which intermediate sensitivity was predicted, 4 of 6 (67%) responded well. In patients who were treated with a TKI for which resistance was predicted, only 3 of 6 (50%) responded. Progression to advanced stage disease (AP/BC), hematopoietic stem cell transplantation (HSCT) and death occurred more often in patients with a KDM compared to patients without a KDM: AP/BC in 25 (36%) versus 29 (14%) patients, HSCT in 20 (29%) versus 43 (21%), death in 26 (38%) versus 29 (14%) and CML-related death in 12 (17%) versus 10 (5%), respectively. Ten-year overall survival (OS) after the first KDM analysis was 49% versus 82% in patients with versus without a KDM, respectively, with a median follow-up of 7.2 years (panel B). The HR of harboring a KDM for OS was 0.355 (95% CI, 0.209-0.603; p<0.001). After correction for age, sex, disease phase and Sokal score, the HR was 0.356 (95% CI, 0.182-0.696; p=0.003). Discussion: This is the first study describing the nationwide practice of KDM testing and assessing the clinical outcome of patients with a KDM in relation to IC50-values. More than 70% of the KDM were detected in patients with primary TKI resistance or in patients who lost a previously achieved response. Observed responses to TKI after the detection of a KDM were mainly in accordance with expected responses based on the IC-value, supporting the use of these in vitro derived predictions in clinical practice. In line with previous studies, the presence of a KDM translated in inferior outcomes with higher prevalence of progressive disease and (CML-related) death. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Clinical Utility and Outcomes Impact of Crystal Digital PCR of Sensitizing and Resistance EGFR Mutations in Patients With Advanced Non-Small Cell Lung Cancer

BackgroundEGFRm represent 15% of advanced NSCLC in European patients. LB for molecular profiling offers a non-invasive alternative to tissue. cdPCR is a high-sensitive and low-cost LB to detect molecular alterations. We aimed to describe cdPCR clinical utility for EGFRm detection in advanced NSCLC. MethodsProspective blood sample collection in patients with advanced NSCLC harbouring EGFRm either at diagnosis, under response or at PD between January 16 and September 20 at Gustave Roussy. LB was performed by cdPCR (Stilla): sensitizing (exon19; exon21 [p.L858R]) and exon 20 p.T790M resistance EGFRm. We defined high tumour burden (high-TB) as >2 metastatic sites. We analysed EGFRm detection by cdPCR and its correlation with progression-free and overall survival (PFS, OS). ResultsA total of 252 blood samples were collected in 140 patients. At baseline (n=25), sensitizing EGFRm were detected in 64% of samples, 88% in patients with high-TB (n=8) and 40% among those with intracranial/intrathoracic isolated lesions (n=5). At PD to tyrosine-kinase inhibitors (TKI) (n=117), detection rate (sensitizing EGFRm) was 56%; 30% in patients with intracranial/thoracic isolated lesions (n=37) vs. 67% in those with high-TB (n=63). At PD to first/second generation TKI (n=81), the p.T790M mutation was found in 22% (18/81); detection rate was 9% for intracranial/thoracic (n=23) vs. 32% for high-TB (n=41) cases. The clearance of EGFRm allelic frequency was correlated with radiological response. The absence of EGFRm detection at TKI-failure was associated with longer OS (39.1 vs. 18.4 months; P=.02). ConclusionscdPCR is a sensitive LB for sensitizing and resistance EGFRm detection. cdPCR positivity was more likely observed in systemic PD cases with high-TB. It is a low-cost EGFRm detecting approach to guide treatment in NSCLC, however metastatic profile should be taken into account.

P59.16 Characterizing the Tumour-Immune Microenvironment in EGFR Mutant NSCLC

Non-small cell lung cancer (NSCLC) comprises around 80% of lung cancers, with mutations in epidermal growth factor receptor (EGFR) effecting approximately 26%. These constitutive activating mutations promote tumour cell proliferation and survival, and are inevitably refractory to tyrosine kinase inhibitors (TKIs) as well as current classes of immune checkpoint immunotherapy (ICI). Third generation TKI Osimertinib offers prolonged disease-free survival, however the reasons for the lack of efficacy of ICI in EGFR mutant tumours remain unclear. The cellular immune composition of the tumour microenvironment is increasingly being recognised as a major factor in host-tumour responses. The use of multispectral immunohistochemistry (IHC) is a valuable tool to investigate the cellular composition of these tumours. Here we compare a cohort of EGFR exon 19 deletion (LREA) tumours to stage matched EGFR wild type (WT) tumours by multispectral IHC. Automated staining was performed for CD8, FoxP3, PD-1, CD68, PD-L1 and cytokeratin markers using MOTiF™ PD-1/PD-L1 lung cancer kit, and slides imaged by Vectra®Polaris™. Image analysis was performed using QuPath, and marker counts were obtained within tumour and adjacent microenvironment compartments Immune cells marked by CD8, FoxP3, PD-1, CD68 composed 5%-30% of total cells in the WT tumours, while LREA tumours contained 5% to 15% of total cells (t-test p = 0.17). While these immune cells trended to be lower in LREA tumours, further investigation into their distribution in a larger cohort of patients is required. The LREA cohort displayed poorer progression free survival (PFS) following resection and platinum therapy than the WT cohort (468 days vs 622 days, p=0.2). Neighbourhood mapping suggested cellular populations within the tumour microenvironment which associated with the different tumour profiles. Our data suggests that tumour intrinsic mechanisms may result in poorer host-tumour responses. One such mechanism is the immunosuppression of the local microenvironment, and we aim to expand this work to encompass a wider cohort of patient tumours and cellular markers.

CML-011: Chronic Myeloid Leukemia: Clinico-Laboratory Patterns and Management Options in Relapsed and Refractory Cases

Context: The patients with the advanced and relapsed chronic myeloid leukemia (CML) experience marked disease burden in terms of symptoms, and unfavorable impact on their life quality and productivity. Objective: The study purpose was to evaluate the diagnosis and prognosis significance of lactate dehydrogenase (LDH) and T315I mutation, as well as the treatment options in the newly diagnosed and relapsed CML. Design: This cohort study included 27 CML patients, treated at the Institute of Oncology between 1995-2021. The venous blood samples were collected for lactate dehydrogenase (LDH) assay and detection of the ABL gene T315I mutation. Setting: The study was related to the outpatient and hospitalized care. Patients: The patients’ age ranged between 20-68 years (average age – 51.3±2, 14 years). The diagnosis of CML was asserted by the quantitative RT-PCR in chronic phase in 26 (96.3%) cases. Main Outcomes Measures: The survival and relapse rates may suggest the biological significance of LDH and T315I mutation. The ECOG-WHO score, p210 BCR-ABL transcript, and the survival should outline the response to tyrosine kinase inhibitors (TKIs). Interventions: Chemotherapy regimens included antimetabolites, alkylating antineoplastic agents, and TKIs. Results: The ECOG-WHO score was 1-3 at diagnosis. LDH ranged between 169–1107 U/L, and was increased in 14 (63.6%) patients, especially in those with leukocytosis over 100 x 109/l. The complete or major molecular responses followed under the TKIs chemotherapy in 16 (59.3%) cases, including 3 (11.1%) with T315I mutation. The relapses developed in 10 (71.4%) patients with the increased LDH and in 5 of 6 patients with T315I. One (3.7%) patient with T315I mutation evolved into the acute phase. The survival ranged between 23-236.8 months (median survival – 95.87±4.51 months) and was lower in cases with T315I mutation and higher LDH level. The ECOG-WHO score reached 0-1 under the treatment with TKIs. Conclusions: The elevated LDH may assess the activity at diagnosis and relapse of CML. T315I mutation and the increased LDH levels correlated with a higher rate of relapses and resistance to the first generation TKIs. Regardless of the chemotherapy line and in relapses, TKIs significantly improved the complete response rate, survival and ECOG-WHO score.

A randomized phase II study comparing nivolumab (NIVO) with carboplatin-pemetrexed (CbPEM) for patients (pts) with EGFR mutation-positive non-small cell lung cancer (NSCLC) who acquire resistance to tyrosine kinase inhibitors (TKIs) not due to a secondary T790M mutation (WJOG8515L).

9037 Background: Although the efficacy of antibodies to programmed cell death–1 (PD-1) appears to be less pronounced in patients with NSCLC harboring epidermal growth factor receptor gene ( EGFR) mutations, patients who develop disease progression (PD) to TKIs due to mechanisms other than secondary T790M mutation of EGFR might be more likely to benefit from NIVO. Here, we report the results of first randomized phase II trial to compare NIVO with the CbPEM in those population. Methods: Pts with advanced EGFR mt NSCLC who experienced PD after EGFR-TKIs were randomized 1:1 to NIVO or CbPEM. Eligibility criteria included the treatment history with TKIs as follow; no evidence of T790M after PD on 1st/2nd generation (gen) TKIs (A) after PD on 3rd gen TKIs as a 2nd line for T790M positive tumor (B) or 3rd gen TKIs as a front-line (C). The primary end point is progression-free survival (PFS) and biomarker analysis were included for exploratory analysis. Results: A total of 102 patients was randomized. Median PFS and overall survival (OS) were 1.7 and 20.7 months (mo), respectively, for NIVO arm (n = 52) versus 5.6 and 19.9 months for CbPEM (n = 50) (Hazard ratio [HR] = 1.92 and 0.88, respectively). Overall response rate and duration of response were 9.6% and 5.3 months for NIVO and 36.0% and 5.5 months for CbPEM. PD-L1 expression on tumor cells and tumor mutation burden (TMB) were evaluated in 77 (TPS 0%. 1-49%, &gt; 50%, n = 46, 20, and 11) and 50 (Median TMB 6.2mt/mb). Immune-related gene expression profiling was under evaluation and the results will be demonstrated in the meeting. The efficacy of NIVO in PD-L1 strong positive (&gt;50%, n = 8) and no evidence of T790M after PD on 1st/2nd gen TKIs (n = 29) was tended to be better than their counterparts. There was no significant correlation between TMB and the efficacy of NIVO. Pneumonitis was observed in one patient (1.0%) for NIVO arm and no new safety signals were noted. Conclusions: NIVO was not associated with longer PFS than CbPEM in selected pts with advanced EGFR mt NSCLC. OS was similar between groups. Baseline PD-L1 status and genetic alteration features may be relevant predictive markers to select pts who would benefit from NIVO. Clinical trial information: jRCTs051180133. [Table: see text]

LncRNA OIP5-AS1 Promotes the Autophagy-Related Imatinib Resistance in Chronic Myeloid Leukemia Cells by Regulating miR-30e-5p/ATG12 Axis.

Background: Resistance to tyrosine kinase inhibitors (TKIs) in patients with chronic myeloid leukemia (CML) remains a problem in clinical treatment, and the mechanism has not been fully clarified. Autophagy can protect cancer cells under chemotherapeutic stimulation. Long noncoding RNAs (lncRNAs) are critical in drug resistance of CML. The role of lncRNAs in autophagy and drug resistance of CML needs to be further explored. Methods: Western blot and immunofluorescence were used to evaluate the autophagy activity in the drug-resistant CML cell line K562/G01 and its parental cell line K562. Then the sensitivity of K562/G01 cells to the first generation TKI imatinib (IM) after autophagy inhibition was determined by CCK-8 assays. The lncRNA OIP5-AS1 related to the drug resistance of CML cells was determined by Gene Expression Omnibus database analysis. Western blot and drug-sensitivity assays were used to detect changes in autophagy and sensitivity to the IM in resistant CML cells after OIP5-AS1 knockdown. The interactions of OIP5-AS1, miR-30e-5p, and ATG12 were explored by RNA immunoprecipitation and dual-luciferase reporter assays. Results: In this study, we found that autophagy was associated with drug resistance in CML cells. Moreover, the upregulation of OIP5-AS1 in K562/G01 cells was related to the enhancement of autophagy. Knockdown of OIP5-AS1 suppressed autophagy and enhanced the sensitivity of K562/G01 cells to IM. Furthermore, OIP5-AS1 regulated ATG12 by competitively binding miR-30e-5p, thereby affecting autophagy-related drug resistance. Conclusion: Our study reveals that OIP5-AS1 promotes the autophagy-related IM resistance in CML cells by regulating miR-30e-5p/ATG12 axis, providing new insights into the drug resistance mechanism of CML.

Detection of Actionable BCR-ABL1 Kinase Domain (KD) Mutations in Chronic Myeloid Leukemia (CML) Patients with Failure and Warning Response to Tyrosine Kinase Inhibitors (TKIs): Potential Impact of Next-Generation Sequencing (NGS) and Droplet Digital PCR (ddPCR) on Clinical Decision Making

Detection of Actionable BCR-ABL1 Kinase Domain (KD) Mutations in Chronic Myeloid Leukemia (CML) Patients with Failure and Warning Response to Tyrosine Kinase Inhibitors (TKIs): Potential Impact of Next-Generation Sequencing (NGS) and Droplet Digital PCR (ddPCR) on Clinical Decision Making

1534P - TP53 mutations predicts worse prognosis in EGFR-mutated NSCLC patients receiving TKIs in first- or further line of treatment

BackgroundNon-small cell lung cancer (NSCLC) patients carrying epidermal growth factor receptor (EGFR) mutations are sensitive to tyrosine kinase inhibitors (TKIs); nonetheless, about 20% of patients show primary resistance to TKIs. We previously demonstrated the association between TP53 mutations and primary resistance to first-line TKIs in EGFR-mutated adenocarcinoma (ADC) patients. Here we analyze a validation case series of ADC patients treated with first-line TKIs to confirm our previous data, and we assess the association between TP53 status and the prognosis of ADC patients treated with third generation TKIs. MethodsWe considered 136 ADC EGFR-mutated patients treated with a TKI in the first-line setting. Also, we analyzed 42 patients who developed T790M mutation and were treated with a third generation TKI in second- or further line setting. EGFR and TP53 mutation analyses were performed by Sanger Sequencing or Next Generation Sequencing methodologies. TP53 mutations were evaluated in relation to disease control rate (DCR: complete response [CR], partial response [PR] or stable disease [SD]), objective response rate (ORR: CR, PR), progression-free survival (PFS) and overall survival (OS). ResultsOf 136 patients, we found 42 (31%) TP53 mutations: 12 mutations in exon 5 (28.6%), 6 in exon 6 (14.3%), 13 in exon 7 (30.9%), and 11 in exon 8 (26.2%). DCR and ORR were 31.8% and 32.5% in TP3-mutated patients with respect to 68.6% and 67.4% in TP53 wild-type (wt) patients, respectively. Exon 8 TP53-mutated patients had a worse PFS with respect to TP53wt patients (HR 3.19 [1.62-6.27], p=0.001), but not OS. Moreover, we assessed TP53 status in 42 patients who developed a T790M mutation and received a third generation TKI in second or additional lines of treatment. In 30 patients with evaluable clinical response, DCR and ORR were 62.5% and 25% in TP53 mutated patients, with respect to 77.2% and 54.5% in the TP53wt patients, respectively. Data analyses of PFS and OS are ongoing. ConclusionsEGFR-mutated NSCLC patients with concomitant TP53 mutations had a worse clinical response to first-, second-, and third generation TKIs, administrated in any line of treatment. Legal entity responsible for the studyIstituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori (IRST) IRCCS, Meldola, Italy. FundingHas not received any funding. DisclosureAll authors have declared no conflicts of interest.

PB1926 THE RELATIONSHIP BETWEEN OXIDATIVE STRESS LEVELS, BCR-ABL1 TRANSCRIPT VALUES AND TREATMENT WITH TYROSINE KINASE INHIBITORS IN PATIENTS WITH CHRONIC MYELOID LEUKEMIA

Background: Chronic myeloid leukaemia (CML) is a chronic myeloproliferative neoplasm associated with a BCR-ABL1 gene sequence. Some studies have shown that oxidative stress is involved in CML pathogenesis, genomic instability, disease progression and resistance to tyrosine-kinase inhibitors (TKI). Aims: To evaluate reactive oxygen species (ROS) levels and the total antioxidant capacity (TAC) in patients with CML at diagnosis and after treatment with TKI. Methods: ROS and TAC were evaluated in a group of CML patients, diagnosed according to the ELN/WHO criteria, and in a control group of healthy volunteers. Patients were divided by age, sex and treatment. ROS were measured using a CyFlow SPACE Sysmex flow-cytometer (reagents from Abcam). TAC was evaluated using a FLUOstar Omega microplate reader (reagents from Sigma-Aldrich). CML patients were initially prescribed cytoreductive treatment (hydroxyurea) and then first or second generation TKI. Informed consent was obtained from all recruited subjects and the study was approved by the Ethics Committee of the University of Medicine and Pharmacy of Craiova, Romania, approval no. 74/23.02.2017. Results: The study group involved 47 CML patients (mean age 59.89 ± 13.35 years, age range 22-87): 24 males (51.06%, mean age 59.00 ± 14.99 years, age range 22-87) and 23 females (48.94%, mean age 60.83 ± 11.32 years, age range 34-80). Oxidative stress levels were higher in patients with CML vs. controls (p = 0.006): the mean TAC value was lower and the mean ROS level was significantly higher in the CML group vs. controls (TAC: 0.28 mM vs. 0.35 mM; ROS: 10.42 FI vs. 10.07 FI, FI = fluorescence intensity). The mean TAC value was significantly lower for each treatment subgroup vs. controls, and in particular for imatinib and dasatinib subgroups, and the mean ROS value was significantly higher for each treatment subgroup vs. controls. Changes of redox status in CML patients during treatment were related to the BCR-ABL1 transcript value.Summary/Conclusion: In our study, CML patients had at diagnosis higher ROS levels and lower TAC values compared with healthy controls. We observed changes in the redox status of CML patients during treatment. Alterations in the redox status may contribute to genomic instability and disease progression and might also be involved in the development of treatment resistance.

Successful of Chemo-Free Treatment with Dasatinib and Blinatumomab in a Pediatric EBF1-PDGFRβ Positive Acute Lymphoblastic Leukemia

Recently, a novel subgroup of B Cell Precursor (BCP) Acute Lymphoblastic Leukemia (ALL), called Philadelphia-like (Ph-like) ALL, has been described. This high-risk group, despite the absence of BCR-ABL1 rearrangement, shows genomic abnormalities that result in aberrant expression of cytokine receptors genes or tyrosine-kinase-activating signaling. These patients are poor responder to conventional chemotherapy but potentially sensitive to Tyrosine-Kinase Inhibitors (TKIs).Herein we report the case of a 10 year-old girl who received diagnosis of precursor B-ALL on February 2018. She started therapy according to observational protocol ALL 2017 of the Italian Association of Pediatric Hemato-Oncology (AIEOP). After pre-phase, the patient resulted prednisone poor responder and continued induction therapy, including daunorubicin, vincristine, PEG-L-Asparaginase, prednisone and intrathecal methotrexate. Bone marrow evaluation showed persistence of disease on day 15 (88% of lymphoblasts) and 33 (60% of blasts) in flow cytometry. At the end of IA induction phase, Minimal Residual Disease (MRD) in RT-PCR showed high positivity (marker 1 = 7.2x10-1, marker 2= 8.11x10-1). At this time, further molecular studies, using RNA targeted next generation sequencing (PanCancer, Illumina), revealed the presence of EBF1-PDGFRβ gene fusion.Since the patient was resistant to conventional therapy and literature's evidences demonstrated potential sensitivity of EBF1-PDGFRβ to TKIs therapy, we decided to add dasatinib, a second generation TKI, to IB induction, with cyclophosphamide, cytarabine and 6-mercapthopurine. After one week of therapy, clinical course was complicated by Klebsiella Pneumoniae sepsis, followed by digestive hemorrhage. Since we retained that the hemorrhagic event could be related to dasatinib, the drug was temporarily discontinued. However, bone marrow evaluation, after only 10 days of dasatinib administration, showed hematologic remission (3% of lymphoblast) and MRD reduction >1 logarithm (markers 1=1-10-2 e markers 2= 9.9 x 10-3).Given the resistance to chemotherapy alone and the excellent response to dasatinib but its related toxicity in combination, we decided to start immunotherapy with blinatumomab, a bi-specific CD3-CD19 monoclonal antibody, alternated to dasatinib, in order to achieve MRD negativity before to proceed with allogeneic hematopoietic stem cell transplantation (HSCT) from HLA-identical sibling. The patient received 2 courses of blinatumomab for 28 days continuous infusion (15 mcg/mq days 1-28), interspersed by 15 days of dasatinib (60 mg/mq/day). After the first cycle the patient achieved complete hematological remission and MRD negativity. MRD negativity was confirmed after first course of dasatinib, second course of blinatumomab and second course of dasatinib. Dasatinib, given alone, was well tolerated and no serious adverse event were reported. Actually, the patient is undergoing HSCT by HLA-identical sister.To our knowledge, only few cases of EBF1-PDGFRβ ALL, treated with TKIs, are described in literature and this is the first in which MRD negativity was obtained with a sequential combination of dasatinib and blinatumumomab, a chemo-free approach, showing efficacy and good tolerability. This case highlights also that screening for targetable lesions at diagnosis or in case of resistance to induction phase is mandatory to identify patients who might benefit from alternative therapies as TKIs, immunotherapy or their combination. A longer follow-up is required to definitively establish the long-term efficacy of this biological approach in our patient. Nevertheless, it is interesting to speculate that alternative treatment with TKIs or immunotherapy could avoid, in the future, an intensive chemotherapy, or probably a transplant approach in selected patients, in order to achieve a durable cure in these Ph-like patients. DisclosuresLocatelli:Bellicum: Consultancy, Membership on an entity's Board of Directors or advisory committees; bluebird bio: Consultancy; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Miltenyi: Honoraria; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Parasole:Baxalta: Membership on an entity's Board of Directors or advisory committees; behring: Consultancy; jazz: Honoraria, Speakers Bureau.

140PD Complex epidermal growth factor receptor (EGFR) mutations and responses to tyrosine kinase inhibitors (TKIs) in advanced lung adenocarcinomas

Background: Two or more different epidermal growth factor receptor (EGFR) mutations can be detected within a single tumor sample, which represents complex mutations. However, the frequency and efficacy of tyrosine kinase inhibitor (TKI) treatments for patients harboring these mutations are unknown. Methods: From January 2011 to January 2017, patients diagnosed with EGFR mutation were screened. The effectiveness of TKIs in patients with complex mutations was retrospectively analyzed. Results: A total of 16,840 subjects were screened, with 5898 positive patients. 187 patients (3.2% of all EGFR mutant patients) had complex EGFR mutations with 95 of advanced lung adenocarcinoma patients were treated with TKIs. The objective response rate (ORR) for patients who had Del-19 + 21L858R (Group A, n = 27), Del-19/21L858R + atypical mutations (Group B, n = 28), double atypical mutations (Group C, n = 20) and complex mutations with primary drug-resistant pattern (Group D, n = 20) were 72.7%, 54.2%, 66.7% and 15.0%, respectively. Median progression free survival (PFS) in the four groups were 18.2 months (95% CI, 12.0 months to 24.4 months), 10.1 months (95% CI, 6.5 months to 13.7 months), 11.1 months (95% CI, 6.8 months to 15.4 months) and 1.4 months (95% CI, 0.2 months to 2.5 months), respectively. Conclusions: These results suggest on the largest sample size that EGFR–TKI therapy is effective in patients with Del-19 + 21L858R, Del-19/21L858R + atypical mutations and double atypical mutations, but less effective in patients with primary drug–resistant pattern. Patients with the Del-19 + 21L858R mutations may therefore benefit more from treatment with first–generation TKIs. Legal entity responsible for the study: Bo Zhang Funding: Has not received any funding Disclosure: All authors have declared no conflicts of interest.

Detection and Clinical Significance of Abundance of EGFR Mutation

Non-small cell lung cancer (NSCLC) patients, with sensitive epidermal growth factor receptor (EGFR) mutations react well to tyrosine kinase inhibitors (TKIs). However, the efficacy of TKIs on patients with the same mutant types differs dramatically. It is implied that the different quantities of mutant alleles could be one of the reasons underlying. Patients with high abundance of EGFR mutation might benefit more from TKIs. There are no universal standards for the definition of EGFR mutant abundance. Abundance could be semi-quantified according to the different sensitivities of detection methods, quantified with quantifying detection techniques such as digital PCR or next generation sequencing, or quantified based on the expression of mutant proteins. The different abundances of primary and metastatic diseases could reflect the heterogeneity of the tumors. The pre-treatment level or the dynamic change of EGFR mutant abundance could help observe the course of the diseases and predict the efficacy of TKIs. TKIs resistance could be detected by change of abundance prior to image manifestations. Besides, the abundance of T790M could also predict drug efficacy and resistance of the first and third generation TKIs. Thus the detection of EGFR mutant abundance has important clinical significance. The standardization and correction of abundance needs more exploration.

The novel detection of EGFR-T790M mutations in exhaled breath condensate.

9032 Background: The EGFR-T790M somatic mutation is the most common mechanism of resistance to Tyrosine Kinase Inhibitors (TKI) in NSCLC. However patients with advanced disease are not always amenable to repeat biopsy for further molecular analysis. Developing non-invasive methods to detect T790M in cell-free DNA (cfDNA), in the absence of tissue is being actively investigated. Furthermore these 'liquid biopsies' may also overcome the problem of tumour genomic heterogeneity. Unfortunately the sensitivity of plasma for T790M detection has been disappointing with a significant chance of a false negative result. Exhaled breath condensate (EBC) is an easily collected sample and is known to harbour cfDNA, including lung cancer mutations. We explored the potential of EBC as a novel method of T790M detection. Methods: We recruited 26 patients who were either 1) known T790M positive pre/during Osimertinib therapy or 2) other mEGFR positive patients on 1st/2nd generation TKI. We collected matched plasma and EBC samples in the majority of cases. EBC samples were collected using the RTube device. Plasma was collected using standard EDTA tubes and extracted within 90 minutes. Using UltraSEEK chemistry, a targeted PCR for ultra-sensitive somatic mutation profiling on the MassARRAY system (Agena Bioscience), we compared the performance of EBC to plasma for the detection of T790M. Results: See Table. Conclusions: In this pilot study we describe the first ever report of the successful and consistent detection of T790M in the EBC of patients with EGFR mutated NSCLC, using a commercially available targeted assay. Our results suggest EBC is responsive to recognised dynamic molecular changes that occur on TKI treatment. We believe this makes EBC analysis an attractive avenue for future research, to optimise the detection of T790M mutations in liquid biopsies. [Table: see text]

An EBMT Prospective Non-Interventional Study of Outcomes and Toxicity of Allogeneic Stem Cell Transplantation in Chronic Myeloid Leukemia Patients Previously Treated with Second Generation Tyrosine Kinase Inhibitors

Introduction: Allogeneic stem cell transplantation (SCT) remains a treatment option for patients with chronic myeloid leukemia (CML) that fail to respond to tyrosine kinase inhibitors (TKI). While the use of Imatinib seems to have no adverse impact on outcomes after transplant, little is known on the effects of prior use of second generation TKI (2GTKI). We present the results of a prospective non-interventional study (NIS) performed by the European Group for Blood and Marrow Transplantation (EBMT) of all consecutive allogeneic SCT for patients diagnosed with CML from 2009 to 2013.Methods: A prospective follow up of pre and post-transplant data was carried out by the EBMT Leiden office, including TKI therapy data, MED-B and a specific MED-C post transplant data. A total of 94 EBMT centers from 32 countries included 437 patients.Results: We present the results of the 383 patients that fulfilled all the inclusion criteria and had median follow-up of 37 months (1-77). The median age was 45 years (18-68) and 251 (65%) were males. Disease status at the start of 2GTKI was: First chronic phase - CP1 (123, 46%), Accelerated phase or >CP1 (67, 25%) and blast crisis (75, 28%). The choice of 2GTKI was: Dasatinib (155, 40%), Nilotinib (64, 17%) and a sequential combination of Dasatinib/Nilotinib with or without Bosutinib/Ponatinib (164, 43%). In addition, 29% of patients that received Dasatinib were in CP1 at the start of 2GTKI and at the time of SCT compared with 45% at the start and 40% at SCT for patients treated with Nilotinib. For patients that received both TKI in sequential combination, 63% were in CP1 at the start of 2GTKI but only 46% reached the SCT in CP1. Overall disease status at SCT was CP1 in 139 patients (38%), AP in 163 (45%) and BC in 59 (16%).The median interval from diagnosis to SCT was 22 months (2 - 267) and the median interval between starting 2GTKI and SCT was 10 months (1 - 191). The donor was an HLA identical sibling in 130 cases (35%) and unrelated in 244 (65%). The majority of SCT were performed using PBSC (295, 77%), while 272 (71%) were myeloablative and 111 (29%) reduced intensity conditioning. The EBMT score was low (0-2) in 26 (7%), intermediate (3-4) in 216 (62%) and high (5-7) in 107 (31%). Primary graft failure (PGF) occurred in 10 (3%) cases, while the incidence of acute GVHD was 34% (95% CI 29-39) and chronic GVHD (CGVHD) was 60% at 5 years (95% CI 54-66). CGVHD occurred at a median of 5.7 months (3-61) post SCT. Other post SCT complications included veno-occusive disease of the liver (VOD) in 6 cases (2%) and severe infection in 195 (65%). There were no differences in post-transplant complications amongst the 3 different 2GTKI subgroups. Overall non-relapse mortality was 18% (95% CI 14-22) at 12 months and 24% (95% CI 19-29) at 5 years. Relapse incidence was 36% (95% CI 29-42), overall survival was 56% (95% CI 50-62) and relapse-free survival was 40% (95% CI 33-47) at 5 years. Overall survival was 67% (95% CI 59-75) at 5 years for patients in CP1. No differences in post-transplant outcomes were found amongst the 3 different 2GTKI subgroups. However, the EBMT score, performance status and disease stage at 2GTKI and at SCT were predictive of overall and progression-free survival.Discussion: This prospective study demonstrates the feasibility of performing allogeneic SCT in CML patients previously treated with 2GTKI. The rate of post-transplant complications including graft failure, VOD, infections, GVHD and non-relapse mortality seems comparable to that of patients treated with Imatinib or TKI-naïve. We observed no differences between outcomes for patients receiving Dasatinib, Nilotinib or any other combination of 2GTKI (including Bosutinib and Ponatinib) pre-SCT. However, patients receiving Dasatinib were more likely to proceed to SCT in advanced phase than in CP1. Patients in CP1 have a very good overall survival despite prior treatment with 2GTKI. Of note, even after 2GTKI, the EBMT score remains a strong predictor of overall and disease-free survival for CML patients undergoing allogeneic SCT. [Display omitted] [Display omitted] DisclosuresSchouten:Sanofi: Consultancy; Novartis: Consultancy. de Witte:Novartis: Honoraria, Research Funding; Celgene: Consultancy; Incyte: Consultancy. Kröger:Neovii: Honoraria, Research Funding; Sanofi: Honoraria, Research Funding; Riemser: Honoraria, Research Funding; Novartis: Honoraria, Research Funding.

Somatic Mutations in Epigenetic Modifiers Identified Using Next Generation Sequencing (NGS) in Diagnostic Samples of CML-CP Can Predict Poor Outcome on Imatinib Which Is Abrogated By Frontline 2G-TKI Therapy

Background: While chronic myeloid leukaemia (CML) originates from a single genetic aberration (BCR-ABL1) remarkably heterogeneity characterises treatment response and outcome. Most CML patients respond well to tyrosine kinase inhibitors (TKI), particularly 2nd generation (2G) TKI but a significant minority shows resistance and a proportion experience progression. At diagnosis there are currently no biomarkers for patients at higher risk of progression who could be treated with more effective treatment or be selected for BMT at an early stage of therapy. Such biomarkers may also provide useful prognostic information in addition to the most valid biomarker to date, the BCR-ABL1 IS ratio during the first 3-6-12 months of TKI therapy.Aims: The aim of our study is to analyse a panel of mutations in epigenetic modifiers in pre-treatment CML-CP using Ion Torrent next-generation sequencing (IONT-NGS) to assess the prognostic value of potential mutations as novel biomarkers of response to 1st and 2G TKI and risk of progression to advanced phase disease.Methods: 100 samples from untreated patients with newly diagnosed CML-CP were included in the study, 62 from patients treated frontline with imatinib (IM) and 38 with a 2G-TKI (31 dasatinib, 4 nilotinib, 3 bosutinib). The patients were classified as TKI responders (R) (34 IM, 22 2G-TKI) or non-responders (NR) (28 IM, 16 2G-TKI) based on BCR-ABL1 IS ratio at 3 months. DNA was extracted from CD34+ cells isolated from diagnostic samples, while DNA from T cells was used as constitutional non-leukemic control to exclude confounding germline mutations. Samples from healthy donors (n=14) and CML blast crisis (BC) (n=5) patients were used as negative and positive controls, respectively. We used a custom panel covering the coding region of 71 epigenetic enzymes. After sequencing data processing was performed excluding variants of low quality, common in the general population with minor allele frequency (maf) >1% or present in the healthy controls, we analysed the genomic data and integrated them with annotated clinical data.Results: After using a variant reduction pipeline, 164 non-synonymous variants that affected protein function were identified: 52 somatic and 112 germline. The somatic mutations (including missense, nonsense, frameshift insertions and splice site variants) were confined to 30 genes, with ASXL1, IKZF1, CREBBP beingthe most frequently mutated (n=9, 7 and 4 respectively). The mutations were detected in 34/100 (34%) CML-CP patients (19/62 IM and 15/38 2G-TKI), in higher proportion in NR (19/44, 43%) compared to R (15/56, 27%; p=0.027). We next correlated the presence of mutations with overall survival (OS), TKI failure free survival (TFFS) and progression free survival (PFS). IM patients carrying somatic mutations demonstrated a poorer response to IM [HR=2.1 (1-4.4 95% CI), p=0.05] and were more likely to progress to advanced phase [HR=3.1 (1-9.4 95% CI), p=0.03] (Figure 1). Nonsense mutations in particular (in ASXL1, IKZF1, DNMT3A, EP300) were found in 4 IM NR vs 1 R and their presence led to poor OS [HR= 6.1 (1.6-23 95% CI), p=0.002] and PFS [HR= 5.4 (1.4-21 95% CI), p=0.006]. As these were observed in 5 patients, further testing is required to corroborate this initial observation. Multivariate analysis revealed that both increased Sokal score and occurrence of somatic mutations negatively influenced outcome: somatic mutations detected in 6/24 low and in 8/13 high Sokal IM patients were associated with worse OS and PFS compared to unmutated patients with the same Sokal score. Among 38 patients treated with 2G-TKI, neither somatic mutations (including nonsense variants) nor combination of somatic mutations with Sokal score had any influence on OS, TFFS, PFS, neither did the presence of germline mutations in either IM or 2G-TKI patients.Summary/Conclusion: Somatic mutations identified using IONT-NGS on 71 epigenetic modifiers potentially predict 1st generation (IM) patient poor survival, drug failure and progression to advance phase disease. However, the more effective therapeutic effect of 2G-TKI seems to overcome the poor prognostic influence of such mutations though further validation on larger cohort of patients may be required to validate preliminary data. Our results suggest that occurrence of somatic mutations at diagnosis have the potential to identify patients who would benefit from upfront treatment with 2G-TKI. [Display omitted] DisclosuresApperley:Incyte: Speakers Bureau; Novartis: Honoraria, Speakers Bureau; Ariad: Honoraria, Speakers Bureau; Pfizer: Honoraria, Speakers Bureau; Bristol Myers Squibb: Honoraria, Speakers Bureau.

High Frequencies of Compound BCR-ABL Mutations and Their Association with Imatinib Resistant, Disease Progression and Late Chronic Phase Disease in Pakistani Chronic Myeloid Leukemia Patients Necessitate the Inclusion of Molecular Testing in Routine Clinical Settings

Introduction: BCR-ABL kinase mutations are the most common reason of resistance to tyrosine kinase inhibitors (TKIs) in chronic myeloid leukemia (CML) patients1. Hence, determination of BCR-ABL mutation status at the time of resistance, disease progression and subsequent drug switching is an integral component of North American and European clinical guidelines 1,2. Compound BCR-ABL mutations have been emerged as one of the major issues in TKI-based therapy of CML, which cause new patterns of drug resistance, including resistance to ponatinib 3. This study wascarried out to find out association of BCR-ABL mutations with treatment outcome in CML patients.Materials & Methods: 150 CML patients were investigated for BCR-ABL mutations using direct sequencing as previously reported 4. SPSS version 19 (IBM, Chicago, IL, USA.) was employed for statistical analysis.Results: 78 (52%) patients were males and 72 (48%) females, with median age 34 years (range: 9-62) (Table 1). Ninety (60%) were IM sensitive and 60 (40%) IM resistant. 72 mutations were detected in 28 (46.7%) patients, with 71.4% patients having compound (2-5) mutations. 14 mutations were detected in 7 IM sensitive patients in late chronic or advanced phases. E355G was the most common mutation (Fig 1). P-loop mutations were found only in IM resistant patients at advanced phases (Fig 2). Elevated TLC, advanced phases and suboptimal responses were associated with IM resistance and mutations. Higher complete hematological and complete cytogenetic responses were seen in patients without mutations (Fig 3). 7-year OS and EFS were 80.4% and 55.6%, respectively (Figs 4-5). Higher survivals were associated with IM sensitivity, low or intermediate Sokal risk, chronic phase, complete hematologic response and complete cytogenetic response.Discussion: Our results show association of BCR-ABL mutations with IM resistance, disease progression and late chronic phase 1,4. Therefore, we recommend BCR-ABL mutation detection for late chronic phase CML patients as well. High frequency of compound mutations in IM resistant patients poses a threat to CML patients by complicated drug resistant patterns, including resistance to 3rd generation TKIs 3,6,7. Therefore, we recommend regular monitoring of CML patients for BCR-ABL mutations and associated drug response in all patients at risk of BCR-ABL mutations and drug resistance.

Molecular genetic and cytogenetic determinants of primary resistance or loss of the response to treatment with tyrosine kinase inhibitors in patients with chronic myeloid leukemia.

Aim of this study was to analyze molecular genetic and cytogenetic reasons for disease resistance to tyrosine kinase inhibitors (TKI) imatinib (IM) and nilotinib (NI) in patients with chronic myeloid leukemia (CML). Material and methods. A group of 32 CML patients with primary or acquired resistance to TKI treatment was investigated. Cytogenetic response was determined by conventional karyotyping with differential banding. Presence of BCR-ABL kinase domain mutations was investigated by direct sequencing. Results and discussion. The frequency of mutations was 37% (12 patients) with prevailing occurrence of mutations with low sensitivity to nilotinib – E255K/V; Т315I; F359V; Y253H. In 47% of the cases (15 patients) additional chromosome aberrations (ACA) were revealed which could also be the reason for TKI resistance in patients without BCR/ABL mutations. Patients with detected mutations of BCR/ABL gene were either switched to nilotinib or treated with increased dose of IM. Cytogenetic response was achieved in only 2 patients with mutations and in 12 patients without them. Frequency of blast crisis development did not differ significantly in both groups. Conclusions. Among the investigated patients with CML resistant to IM BCR/ABL gene mutations were detected in more than third of the cases whereas ACA were found in almost half of the group. Taking into account revealed prevalence of mutations not sensitive to the 2nd generation TKI nilotinib, investigation of mutational status has to be obligatory in all patients for whom treatment correction is considered. Presence of ACA should also be taken into account in patients requiring administration of the second line TKI since they can adversely influence expected treatment response as well.

Molecular Response to Tyrosine Kinase Inhibitors (TKIs) for Chronic Myeloid Leukemia (CML). an Update on Experience at Tawam Hospital, Abudhabi, UAE in the Light of ELN Guidelines

BackgroundChronic Myeloid Leukemia (CML) is a clonal myeloproliferative disorder characterized by the presence of a balanced reciprocal translocation involving the long arms of chromosomes 9 and 22. The fusion gene that is created by this translocation (BCR-ABL1) encodes for a constitutively active protein tyrosine kinase that is primarily responsible for the leukemic phenotype.Targeted therapy with Tyrosine Kinase Inhibitors (TKIs) has become the recommended first-line treatment for patients with CML. Commercially available TKIs include Imatinib, Nilotinib, Dasatinib, Ponatinib and Bosutinib. The first three drugs are approved for first line therapy while the later 2 are for resistant disease. Monitoring of the response to therapy is done with quantification of the BCR-ABL transcripts by RQ-PCR–based molecular technique.MethodsRetrospective review of charts of patients diagnosed with CML between January 2010 and June 2014. Data points were measured at 3, 6, 12, and 24 months post initiation of therapy and results were documented as per ELN guidelines.Results56 patients were diagnosed with CML. The median age was 33 years (range 19-73 years). Male to female ratio was 4:1. Sokal score was calculated for 53 patients (data for 3 patients was incomplete) 21 were low risk, 24 were intermediate risk and 8 were high risk.7 patients were lost from follow up after diagnosis and are excluded from analysis. 1 patient has not reached the 3 month mark and is also excluded from analysis. 13 patients were started on initial treatment with Imatinib 400 mg while 35 with second generation TKIs (Dasatinib 100 mg daily or Nilotinib 300 mg BID) daily as upfront therapy.With a median follow up of 27 months (range 3 month to 51 months) 4/13 (30%) patients on Imatinib as first line therapy were able to achieve optimal repsone (one at a dose of 600 mg daily). 8 patients were switched to second line therapy and 7/8 patients have achieved MMR (1 patient remains in full cytogenetic relapse due to non-compliance). 35 patients were treated with 2ndgeneration TKIs as first line therapy. 22 out of 35 (62 %) patients have achieved optimal results within 18 months of front line therapy . Second line therapy was initiated in patients achieving suboptimal results or intolerance in 11 patients. 5 of these patients subsequently achieved MMR while 5 remain with suboptimal results. 1 patient had disease progression while one was lost to follow-up after achieving a partial cytogenetic response at 6 months.Interestingly 12 (25%) patients achieved MMR/CMR within 6 months of starting TKIs. Of these only 1 was on Imatinib while the rest were on 2ndgeneration TKIs. MMR 4.5 or undetectable levels of bcr-abl transcript have been documented in 10 patients (20 %) for the whole cohort.4 patients had disease progression on TKI (treatment failure rate of 8 %). One patient had disease progression to accelerated and then blast crisis (lymphoid and myeloid) while the other 3 patients are alive with only CHR with one resistant to all TKIs, one with intolerance of all TKIs and one secondary to noncompliance.ConclusionWe have previously reported on our experience with CML. We have now updated our report with a larger cohort of patients. The median age remains much lower as compared to Western countries, just reflecting differences in the age distribution of the population in the UAE with 80% being below the age of 65 years.MMR report from Enestnd trial is 67-71% in favor of Nilotinib as compared to Imatinib 44%, while the Dasision trial reported a MMR of 44 % in favor of Dasatinib with faster rate to response. Our results mirror the results of these phase 3 randomized trial with optimal response of 62 % with second generation TKIs% as compared to 30 % with Imatinib as front line therapy.Expatriates accounts for approximately 80% of the population in the UAE and many are temporary employed, having limited health care coverage, limited financial means as well as limited possibilities to attend regular follow-ups. This leads to compliance problems, loss from follow-up and suboptimal management and monitoring of their disease. These factors also complicate any chance of treatment free period for patients who achieve undetectable levels of bcr-abl transcripts. Additionally absence of technology for mutational analysis makes it impossible to determine underlying reasons for suboptimal response with accuracy. DisclosuresAlam:BMS: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Hussain:BMS: Honoraria; Novartis: Honoraria. Lal:BMS: Honoraria; novartis: Honoraria.