ALBERT

Description: BCR-ABL kinase domain (KD) mutations are the major mechanism of acquired imatinib resistance in patients (pts) with chronic myeloid leukemia (CML). Second generation tyrosine kinase inhibitors (TKI) are effective against most imatinib resistance mutations but treatment can be hampered by the emergence of secondary drug-resistant clones over time. Furthermore, individual KD mutations differ according to their in vitro transforming potency and tyrosine kinase activity which in vivo upon presence of multiple mutations may result in competition between different clones. Using a novel sensitive and quantitative monitoring approach we systematically investigated the kinetics of drug-resistant mutants on second generation TKI in order to identify patterns of dynamics and to understand mechanisms of polyclonal drug resistance. Fourty CML pts (24 m; median age 64 years, range 39–74) with resistance to imatinib in chronic phase (n=31), accelerated phase (n=7), or blast crisis (n=2) were treated with dasatinib (D, n=20) or nilotinib (N, n=20). Peripheral blood samples taken at baseline and after 3, 6, 9, and 12 months on second generation TKI therapy were subjected to standard genotyping performed by D-HPLC/sequencing and two high-sensitive allele-specific approaches (ligation PCR [L-PCR] and amplification refractory mutation system PCR [ARMS-PCR]) for a panel of 13 key mutations: G250E, Q252H, Y253F/H, E255K/V, V299L, T315I, F311I, F317L, M351T, E355G, F359V. All mutational findings obtained by at least two methods were subjected to quantitative monitoring of BCR-ABLmutant/GUS by ARMS-PCR allowing (i) a dynamical detection range of mutant BCR-ABL over 3 to 4 orders of magnitude and (ii) quantification of the mutant cell subset towards BCR-ABL/GUS ratio. We identified a total of 53 mutated clones in 28 imatinib resistant subjects, of which 46 were assessed quantitatively over time. The following patterns of kinetics were observed: I. A parallel decrease (〉2 orders of magnitude) of BCR-ABLmutant/GUS and BCR-ABL/GUS ratio without further mutations emerging (monoclonal resistance, good molecular response, n=11). II. Persistence of a single mutated clone (change

Description: Mutations in the Abl kinase domain and Bcr-Abl gene amplification have been recognised as the most common mechanisms of resistance to Imatinib (Gleevec) in chronic myeloid leukemia (CML). However, Imatinib resistance by Bcr-Abl independent mechanisms have also been reported. The extracellular signal-regulated protein kinase 5 (Erk5) signalling pathway is involved in cell survival and cell cycle control functions. Interestingly, it was recently reported that ERK5 is important in CML (Buschbeck M., 2005). Bcr/Abl was found to increase the level of Erk5 by stabilizing the protein thus contributing to increased cell survival. In this study we asked whether small interfering RNA (siRNA)-mediated depletion of endogenous Erk5 or overexpression of wild type Erk5 would affect the survival of Imatinib-treated human K562 CML cells. These cells express Bcr-Abl with a wild type kinase domain. Fluorescence activated cell sorting analyses of propidium iodide-stained K562 cells revealed that treatment with 1 μM Imatinib for 24 hrs led to an increase of the apoptotic cell population from 9 to 27 %. The number of cells, arrested in G0/1 phase was also elevated following Imatinib treatment from 66 to 85 %. Overexpression of wild type Erk5 in K562 cells reduced the frequency of Imatinib-induced apoptosis from 27 to 18 % without affecting cell cycle distribution of the living cells. After having established that overexpression of Erk5 renders cells partially resistant to Imatinib treatment we tested the effect of siRNA-mediated depletion of endogenous Erk5 on the viability of K562 cells challenged with Imatinib. Indeed, 42% of K562 cells transfected with siRNA against Erk5 underwent apoptosis after Imatinib treatment. Imatinib induced apoptosis in only 20% of cells transfected with a control siRNA. Furthermore, Erk5 depletion strongly inhibited cell cycle progression in Imatinib-treated K562 cells. Thus, the cell populations in S phase and mitosis were reduced from 22 to 16 % and from 24 to 9 %, respectively. Taken together, our data and those of Buschbeck et al. suggest that ERK5 levels may strongly affect cell survival during Imatinib treatment of CML cells.

Description: Rationale: Dasatinib (DAS) and interferon have different modes of action and may have synergistic activity in CML, due to both antineoplastic and immunostimulatory mechanisms. Addition of pegylated interferon (PegIFN) to imatinib therapy in CP-CML has in previous clinical trials (French SPIRIT and NordCML002) resulted in deeper molecular responses. Thus, an optimal combination of DAS and PegIFN may increase the proportion of patients who reach deep molecular response with potential for treatment-free remission (TFR). Design: Newly diagnosed CP-CML patients were treated with DAS (Sprycel, BMS) 100 mg OD as single drug for three months. Thereafter weekly subcutaneous injections of Peg-IFN α2b (PegIntron, MSD) were added to DAS; from end of month 3 (M3) to M6, 15µg/week, thereafter 25µg/week until M15. Primary end points were safety and the rate of MMR at M12. The doses of PegIFN were lower than in the SPIRIT and NordCML002 studies to increase adherence. Population: Forty patients were included at 14 university centers. One patient was lost to follow-up after M6. All patients were included in analysis up to M12. Mean and median age was 48 years (range 19-71). The proportions of high risk patients were 25% (Sokal), 15% (Hasford), and 15% (EUTOS). Safety and dosing: Treatment was well tolerated with expected DAS and PegIFN related side effects. Six patients had seven serious adverse events (AEs), all hospitalizations. 1 episode each of bradycardia/atrial fibrillation (possibly PegIFN-related), headache (DAS), fever (PegIFN), anaphylaxis-like reaction (PegIFN), fever/malaise/headache (PegIFN), pneumonia and a knee effusion (both unrelated). One pleural effusion occurred (grade 2, 3%). Grade 3-4 neutropenia and thrombocytopenia occurred in 6 and 9 patients respectively. Prolonged hematological toxicity (〉2 months) occurred in 8 patients, causing dosing problems in 5. One patient suffered grade 3 depression. Grade 3 flu-like symptoms occurred in 2 patients. One patient had lipase elevation grade 3 and one patient developed hypothyroidism attributed to PegIFN. Grade 2 dermal AEs like rash and acne occurred in about 20%, attributable to both drugs. 94% (DAS) and 76% (PegIFN) of assigned dose was given. Dose reductions occurred in 19 patients for DAS and 20 patients for PegIFN. Two patients discontinued DAS and switched to nilotinib, 1 for headache at M3 and 1 at M12 for lack of efficacy/hematological toxicity. Two patients could not start PegIFN for hematological toxicity (one lost to follow-up after M6). PegIFN was discontinued because of bradycardia/atrial fibrillation (1 patient), anaphylaxis (1 patient), flu-like syndrome (2 patients) and long-term hematological toxicity (2 patients). At 12 months 31/38 pats (82%) were still on PegIFN, a higher proportion than in the French Spirit or NordCML002 studies. Efficacy: We have used the DAS arm of the Dasision study (Kantarjian NEJM 2010) as a historical control. Early response at M3 was very similar between studies. In the present and the Dasision cohorts respectively, 18% vs 16% missed the 10% BCR-ABLIS landmark, 66% vs 56% achieved a CCyR and 8% vs 8% achieved MMR. At M6, three months after introduction of PegIFN, a steep increase in MMR rate was observed compared with Dasision. This was also reflected in deep responses, MR4.0 (see tables) and MR4.5 at M12, 18% vs 5%. The primary efficacy endpoint was MMR at M12, 82% vs 46%. Table 1.MMRDAS+PegIFN (%)DAS (Dasision)(%)Difference (%)M3880M6532726M9663927M12824636Table 2.MR4.0DAS+PegIFN (%)DAS (Dasision) (%)Difference (%)M3303M620614M938830M12481236 Progressions and treatment failure defined by ELN 2013: Failures: No progression was noted. At M3, 2 patients still had 〉95% Ph+ metaphases (MF). At M6, four patients (11%) had 〉 35% Ph+MF or 〉10% BCR-ABL levels. At M12, one patient failed CCgR and two more patients failed

Description: Background: In chronic myeloid leukemia (CML) the combination treatment of tyrosine kinase inhibitors (TKIs) with interferon-α (IFN-α) has proved to be effective and well-tolerated. IFN-α has long-term immunomodulatory effects, and when combined to TKI therapy, it may increase the success rates for treatment free remission. In our recent clinical trial NordCML007, a low-dose pegylated IFN-α was combined with dasatinib therapy. As dasatinib is also known to have immunostimulatory effects (activation of T and NK cells and downregulation of regulatory T cells), we aimed to monitor the immune effects of dasatinib and IFN-α combination treatment. Methods: 40 newly diagnosed CML patients participated in the NordCML007 clinical trial (NCT01725204). Patients were treated with 100 mg dasatinib QD and after 3 months IFN-α treatment was added (first 3 months 15 μg/week, then 25 μg/week of pegylated IFN-α). After 12 months of combination treatment, patients resumed to dasatinib monotherapy. In this immunological substudy, peripheral blood samples were collected at the diagnosis, 3, 12, and 24 months after the start of therapy. T- and NK-cells were phenotyped with multicolor flow cytometry, and their function (degranulation and cytokine secretion) was studied. In addition, a multiplexed cytokine and growth factor panel was performed (Proseek Multiplex Inflammation I96×96, Olink). Results: Dasatinib monotherapy led to an increase of NK-cell frequencies when compared to pre-treatment values (median diagnosis 6.8% vs. 3 months 12.8%, p