Clinical Response to Upfront Targeted Tyrosine Kinase Inhibitors among Patients with Myeloid/Lymphoid Neoplasms with Eosinophilia and Tyrosine Kinase Gene Fusion

INTRODUCTION

Myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusion (MLN-TK) is an entity encompassed of a heterogeneous group of rare hematopoietic neoplasms that are driven by gene fusion involving PDGDRA/B, FGFR1, JAK2, FLT3 or ETV6::ABL1. Though patients presenting with chronic phase MLN-TK with PDGFRA fusion display a favorable outcome in response to upfront TK inhibitor (TKI) therapy, the outcomes of MLNs driven by other TK fusions are not well described. In this study, we aimed to critically analyze the treatment outcomes of patients with MLN-TK, focusing on the role of upfront TKIs in both chronic- and blast-phase diseases.

METHODS

The retrospective study included patients with confirmed MLN-TK from 3 centers and assessed demographic and clinical variables, treatment, and outcomes.

RESULTS

Forty-two patients with confirmed MLN-TK [PDGFRA (n = 22), PDGFRB (n = 4), FGFR1(n = 10), JAK2 (n = 2); and FLT3 (n = 3)] were included. Fifteen of 25 (60%) chronic-phased patients received upfront TKI therapy had a long-term remission. Nine of 16 (60%) blast-phase patients with upfront TKIs also achieved complete remission and remained alive at a median follow-up of 20 months. All 3 patients with blast phase disease who received upfront chemotherapy without positive response did not respond to subsequent TKI therapy, emphasizing the importance of initiating TKI therapy early. Upfront TKI therapy was associated with longer overall survival in univariate analyses (HR, 0.054 [95% CI, 0.007-0.42]) and multivariate analyses (HR, 0.03 [95% CI, 0.002-0.47]).

CONCLUSION

The outcomes of upfront TKI therapy are excellent for MLN-TK in both chronic and blast phases, regardless of gene abnormalities.

Impact of ABL kinase domain mutations on the outcome of patients with chronic myeloid leukemia (CML)

6588

Background: Patients with CML who develop resistance to imatinib commonly have mutations in the BCR-ABL kinase domain (KDM). Studies looking at outcomes in patients with P-loop versus non-P-loop mutations within the ABL-Kinase Domain have produced conflicting results. Methods: The Total Cancer Care (TCC) database was used to identify patients with CML treated at Moffitt Cancer Center (MCC). Descriptive data were reported, chi square test was used for categorical variables, and Kaplan Meier curves were used for OS and PFS. Log rank test was used to compare survival times between groups. Results: Between 1992 and 2011, 540 CML patients were treated at MCC. Of those, 51% were male and 71% were under the age of 60. Sixty percent (n=322) were diagnosed after 2001. Of the 540 patients, 6.5% (n=35) were found to have mutations of which 26 were detected in patients diagnosed after 2001. Of the 35 patients, 74% (n=26) had single mutations and 26% (n=9) had compound mutations. P-loop mutations were seen in 17% (n=6) and 43% (n=15) had T315I mutations. Patients with KDM progressed to accelerated or blast phase in 46% (n=16) of cases compared to 27% (n=136) without mutations (p=0.03). Median OS was 126 months, 109 months, and not reached in patients with P-loop, T315I, and non-P-loop mutations respectively (p=0.17). The corresponding median PFS was 85 months, 89 months, and not reached (p=0.20). In patients with one mutation median OS was not reached compared to 105 months in patients with compound mutations (p=0.27). After 2001, patients with KDM had a median PFS of 75 months and OS of 126 months while neither was reached in the non-mutation cohort (p=0.007, p=0.26 respectively). Median PFS in patients with single mutations was 85 months versus 10 months in those with compound mutations (p=0.037). Patients with KDM had additional Ph+ clones on cytogenetics in 49% of cases compared with 19% of cases in the non-mutation group (P < 0.005). Conclusions: T315I and P-loop KDM predict PFS and OS in CML patients, and convey a trend for worse prognosis. The presence of additional Ph+ clones in patients with BCR-ABL KDM indicates a higher level of genetic instability and clonal evolution, which may be the contributing factor to poor outcomes.

Lenalidomide promotes p53 degradation by inhibiting MDM2 auto-ubiquitination in myelodysplastic syndrome with chromosome 5q deletion

Allelic deletion of the RPS14 gene is a key effector of the hypoplastic anemia in patients with myelodysplastic syndrome (MDS) and chromosome 5q deletion (del(5q)). Disruption of ribosome integrity liberates free ribosomal proteins to bind to and trigger degradation of mouse double minute 2 protein (MDM2), with consequent p53 transactivation. Herein we show that p53 is overexpressed in erythroid precursors of primary bone marrow del(5q) MDS specimens accompanied by reduced cellular MDM2. More importantly, we show that lenalidomide (Len) acts to stabilize MDM2, thereby accelerating p53 degradation. Biochemical and molecular analyses showed that Len inhibits the haplodeficient protein phosphatase 2A catalytic domain alpha (PP2Acα) phosphatase resulting in hyperphosphorylation of inhibitory serine-166 and serine-186 residues on MDM2, and displaces binding of RPS14 to suppress MDM2 autoubiquitination whereas PP2Acα overexpression promotes drug resistance. Bone marrow specimens from del(5q) MDS patients resistant to Len overexpressed PP2Acα accompanied by restored accumulation of p53 in erythroid precursors. Our findings indicate that Len restores MDM2 functionality in the 5q- syndrome to overcome p53 activation in response to nucleolar stress, and therefore may warrant investigation in other disorders of ribosomal biogenesis.

Phase 1, pharmacokinetic (PK) and pharmacodynamic (PD) study of of the Hsp-90 inhibitor, KOS-1022 (17-DMAG), in patients with refractory hematological malignancies

2081

Background: Disruption of Hsp90-client protein heterocomplexes leads to degradation of a variety of oncoproteins. KOS-1022, an Hsp90 inhibitor and water-soluble geldanamycin derivative, is in trials in patients with solid tumors. Compared to a prior geldanamycin derivative (17-AAG), KOS-1022 is ∼3–5 fold more potent (comparing in vitro cytotoxicity or the MTD in toxicology studies on the same schedule). Primary study objectives: establish safety and MTD of KOS-1022 in patients with advanced hematologic malignancies; characterize PK and PD. Methods: Escalating doses of KOS-1022 are given IV over 1 h twice weekly for 2 out of 3 weeks. Plasma KOS-1022 concentrations (1st and 4th infusion, Cycle 1) are quantitated by LC/MS/MS. Pre and on-study CD34+ bone marrow and peripheral blasts undergo flow cytometry to quantify Hsp70/90, pAKT/total AKT, markers of apoptosis and proliferation. Response in AML pts used IWG criteria. Results: 13 pts have been enrolled at doses of 8 (n=4), 16 (n=6), 24 (n=1) and 32 mg/m2 (n=2). All were AML (except 1 CML). Most (n=11) patients had 2–3 prior induction regimens. DLT was seen in 2 pts at 32 mg/m2 (acute myocardial infarction and elevation of troponin). Both patients had significant co-morbidity, including (1) prior myocardial infarction and (2) progressive AML with a similar troponin elevation during induction chemotherapy prior to study. Common drug-related toxicities (all Grade 1–2): fatigue, nausea, diarrhea and arthralgias. From 8 to 32 mg/m2, approximately linear PK was observed. Mean terminal half-lives varied from 13.0–31.2 hours. Day 1 clearance for 8, 16 and 32 mg/m2 was 5.6, 9.7 and 10.8 L/hr/m2; mean Vz (L/m2) for these groups were 238, 433 and 489. Although pre-infusion drug was quantifiable on Day 11 in most patients, Day 11/Day 1 AUC0–25h ratio was 0.96. Activity in AML: 2 CRi and 1 SD x 9 cycles were observed. Comparing BMAs taken at Day 8 and Day 15 to baseline: decreased Hsp90 (41% to 13%), increased Hsp70 (8% to 84%) with decreased pAKT (Ser), pAKT (Thr) and total AKT in CD34+ cells. Conclusions: KOS-1022 appears to be well tolerated, with preliminary signs of clinical and biologic activity in refractory leukemia. MTD has not been defined. Plasma PK is linear over this dose range.

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