Ibrutinib modulates the immunosuppressive CLL microenvironment through STAT3-mediated suppression of regulatory B-cell function and inhibition of the PD-1/PD-L1 pathway

Ibrutinib, a covalent inhibitor of Bruton Tyrosine Kinase (BTK), is approved for treatment of patients with relapsed/refractory or treatment-naïve chronic lymphocytic leukemia (CLL). Besides directly inhibiting BTK, ibrutinib possesses immunomodulatory properties through targeting multiple signaling pathways. Understanding how this ancillary property of ibrutinib modifies the CLL microenvironment is crucial for further exploration of immune responses in this disease and devising future combination therapies. Here, we investigated the mechanisms underlying the immunomodulatory properties of ibrutinib. In peripheral blood samples collected prospectively from CLL patients treated with ibrutinib monotherapy, we observed selective and durable downregulation of PD-L1 on CLL cells by 3 months post-treatment. Further analysis showed that this effect was mediated through inhibition of the constitutively active signal transducer and activator of transcription 3 (STAT3) in CLL cells. Similar downregulation of PD-1 was observed in CD4+ and CD8+ T cells. We also demonstrated reduced interleukin (IL)-10 production by CLL cells in patients receiving ibrutinib, which was also linked to suppression of STAT3 phosphorylation. Taken together, these findings provide a mechanistic basis for immunomodulation by ibrutinib through inhibition of the STAT3 pathway, critical in inducing and sustaining tumor immune tolerance. The data also merit testing of combination treatments combining ibrutinib with agents capable of augmenting its immunomodulatory effects.

Cord blood NK cells engineered to express IL-15 and a CD19-targeted CAR show long-term persistence and potent antitumor activity

Chimeric antigen receptors (CARs) have been used to redirect the specificity of autologous T cells against leukemia and lymphoma with promising clinical results. Extending this approach to allogeneic T cells is problematic as they carry a significant risk of graft-versus-host disease (GVHD). Natural killer (NK) cells are highly cytotoxic effectors, killing their targets in a non-antigen-specific manner without causing GVHD. Cord blood (CB) offers an attractive, allogeneic, off-the-self source of NK cells for immunotherapy. We transduced CB-derived NK cells with a retroviral vector incorporating the genes for CAR-CD19, IL-15 and inducible caspase-9-based suicide gene (iC9), and demonstrated efficient killing of CD19-expressing cell lines and primary leukemia cells in vitro, with marked prolongation of survival in a xenograft Raji lymphoma murine model. Interleukin-15 (IL-15) production by the transduced CB-NK cells critically improved their function. Moreover, iC9/CAR.19/IL-15 CB-NK cells were readily eliminated upon pharmacologic activation of the iC9 suicide gene. In conclusion, we have developed a novel approach to immunotherapy using engineered CB-derived NK cells, which are easy to produce, exhibit striking efficacy and incorporate safety measures to limit toxicity. This approach should greatly improve the logistics of delivering this therapy to large numbers of patients, a major limitation to current CAR-T-cell therapies.

ATM function and its relationship with ATM gene mutations in chronic lymphocytic leukemia with the recurrent deletion (11q22.3-23.2)

Approximately 10–20% of chronic lymphocytic leukemia (CLL) patients exhibit del(11q22–23) before treatment, this cohort increases to over 40% upon progression following chemoimmunotherapy. The coding sequence of the DNA damage response gene, ataxia-telangiectasia-mutated (ATM), is contained in this deletion. The residual ATM allele is frequently mutated, suggesting a relationship between gene function and clinical response. To investigate this possibility, we sought to develop and validate an assay for the function of ATM protein in these patients. SMC1 (structural maintenance of chromosomes 1) and KAP1 (KRAB-associated protein 1) were found to be unique substrates of ATM kinase by immunoblot detection following ionizing radiation. Using a pool of eight fluorescence in situ hybridization-negative CLL samples as a standard, the phosphorylation of SMC1 and KAP1 from 46 del (11q22–23) samples was analyzed using normal mixture model-based clustering. This identified 13 samples (28%) that were deficient in ATM function. Targeted sequencing of the ATM gene of these samples, with reference to genomic DNA, revealed 12 somatic mutations and 15 germline mutations in these samples. No strong correlation was observed between ATM mutation and function. Therefore, mutation status may not be taken as an indicator of ATM function. Rather, a direct assay of the kinase activity should be used in the development of therapies.

Acute myeloid leukemia (AML) in adolescents and young adults (AYA): The M. D. Anderson Cancer Center (MDACC) experience

7051

Background: AML is a heterogeneous group of hematopoietic neoplasms demonstrating clonal proliferation of myeloid precursors and is typically a disease of older adults. Little is known about outcomes of AYA with AML. Methods: We retrospectively analyzed all patients (pts) with AML treated at MDACC from 1965 to 2008. Pts ages 16 to 21 years (yrs) were defined as AYA. Results: Among 3,934 adult AML pts treated during this period, 163 pts (4%) were AYA with median age of 19 yrs. This cohort included 27 (17%) pts with Core Binding Factor (CBF)-AML [inv(16), t(8:21)] and 19 pts (12%) with acute promyelocytic leukemia (APL). Among the other pts, 50% had diploid cytogenetics, 11% had 5 or 7 abnormalities, 39% had other cytogenetic changes. Antecedent hematologic disorders were present in 33 pts (20%). Among 20 evaluated pts, FLT3 internal tandem duplication (ITD) was present in 4 pts and FLT3 kinase domain mutation was found in 2 pts. Complete remission (CR) rates were 89% for CBF AML, 79% for APL, and 75% for all other pts. Median survival for the total cohort was 1.7 yrs with 36% alive at 3 yrs, and median CR duration of 1.3 yrs (30% CR at 3 yrs). Outcome is better for pts with CBF leukemia (3 yr survival 56%, sustained CR 49%) and APL (3 yr survival 51%, sustained CR 36%) compared to other AML (3 yr survival 28%, sustained CR 24%). CR rates have improved from 71% in 1965–1984, to 85% in 1985–1994, and 83% after 1994. Similarly, overall survival (OS) has increased during the same time periods (3-yr survival 18%, 44%, and 53%, respectively) together with CR duration (3 yr CR duration 21%, 32% and 39%, respectively) as early mortality has decreased (11%, 8%, and 4%, respectively). To compare outcomes of AYA with older adults, we focused on those with diploid cytogenetics.CR for pts ages 16–21 was 81%, with 3 yr survival of 46%; for ages 22–45, CR was 75% and 3 yr survival 36%; for ages 46–60 CR was 68% with 3 yr survival 28%; and for pts age greater than 60, CR was 54% with 3 yr survival of 22%. Conclusions: The outcome of AYA pts with AML is significantly better than for older adults with AML. Despite the advances in treatments over time, there is still significant room for improvement, particularly among those AYA with AML other than CBF and APL. Exploration of new treatment options is needed in this patient population.

No significant financial relationships to disclose.

Phase II study of vorinostat (V) in combination with idarubicin and high-dose cytarabine (IA) as front-line therapy in patients (pts) with high-risk myelodyplsatic syndrome (MDS) or acute myeloid leukemia (AML)

7004

Background: Standard induction therapy for pts with AML has not changed over the last 2 decades nor has the outcome of these pts. We demonstrated in vitro and ex vivo that the combination of an histone deacetylase inhibitor with anthraycline is synergistic (Blood 2006;108:1174); an effect that could be mediated by activation of DNA damage/repair pathways, and found that such combination is safe in phase 1 trial (Blood 2007;110:1842). We designed a phase II study of V with IA as front-line therapy for MDS/AML. Methods: Pts with untreated int-2/high-risk MDS or AML ages 15–65 with adequate liver and renal functions and PS, and EF ≥ 50% were eligible. Pts with CBF were excluded. Initial dose of V was 500 mg orally TID for 3 days followed on day 4 by IA (I:12 mg/m2/dx3; A:1.5g/m2/dx4 over 24 hrs). After induction and if in CR, pt can receive 5 cycles of consolidation with V at the same dose and IA (I:8 mg/m2/dx2; A:0.75g/m2/dx3 over 24 hours) followed by 1 year of maintenance with V. The study was powered to demonstrate improvement in PFS at 7 months and acceptable toxicity. Prior to formal initiation of the phase II, the study had a “run-in” phase to confirm the safety of the triple combination. Correlative studies include analysis of DNA repair/damage pathways. Results: 22 pts have been registered. 3 pts with relapsed/refractory AML were treated in the run-in phase. No excess toxicity was observed; 2 achieved CR and 1 CRp. Following these, 19 pts were enrolled on the phase 2 portion. 17 pts were evaluable. Median age was 49 years. Median WBC at presentation was 12.75 x 109/L. Cytogenetic analysis were abnormal in 12 (71%), complex in 10 (59%). 8 (47%) had secondary disease. 4 (23%) were Flt-3 positive. No unexpected grade 3/4 toxicities have been observed. The CR rate was 82%. 1 pt acheived a marrow CR and 2 pts died during induction. CR were universally associated with CG response. All Flt-3+ pts achieved a CR. Only 2 pts (14%) have relapsed (4 and 5 months). The median PFS has not been reached. Conclusions: The combination of IA and V is safe and active in AML/MDS. No stopping rule has been met. Results will be compared with those of a parallel IA study at MDACC. Correlative analysis are ongoing.

[Table: see text]

Soluble syndecan-1 (sCD138) as a prognostic factor independent of mutation status in patients with chronic lymphocytic leukemia

Syndecan-1 (sCD138) is a transmembrane heparan sulfate-bearing proteoglycan expressed in epithelial cells as well as hematopoietic cells that demonstrate plasmacytoid differentiation. Higher levels of sCD138 correlate with poor outcome in myeloma. We examined the association of circulating sCD138 levels in plasma with clinical behavior in 104 patients with chronic lymphocytic leukemia. sCD138 levels were significantly higher in patients (median, 52.8 ng/ml; range, 13.4-252.7 ng/ml) than in healthy control subjects (median, 19.86; range, 14.49-33.14 ng/ml) (P < 0.01). Elevated sCD138 (>median, 52.8 ng/ml) was associated with significantly shorter survival (P = 0.0004); this association was independent of IgVH mutation status, beta2-microglobulin (beta2-M) level, and treatment history. Patients with mutated IgVH but high sCD138 levels (>52.8 ng/ml) had significantly shorter survival than those with mutated IgVH and lower levels of sCD138. Similarly, patients with unmutated IgVH but high sCD138 levels had significantly shorter survival than those with lower sCD138 levels and unmutated IgVH (P = 0.007). In a multivariate Cox regression model, only Rai stage, beta2-M, and sCD138 remained predictors of survival. These data suggest that sCD138 when combined with beta2-M and Rai stage, may replace the need for testing IgVH mutation status.

Beta-2 microglobulin (B2M) is an independent prognostic factor for clinical outcomes in patients with CLL treated with frontline fludarabine, cyclophosphamide, and rituximab (FCR) regardless of age, creatinine clearance (CrCl)

7034

Introduction: High β2M levels are a risk factor in CLL. PCR therapy has been reported to be better tolerated than FCR in older or with decrease renal function pts (Shanafelt, Blood 108:15a). We assessed the association between age, CrCl, PS, β2M and outcomes in pts treated with FCR. Methods: From 7/99 to 1/04, 300 pts received rituximab 375 mg/m2 D1; fludarabine 25 mg/m2/d D2–3; and cyclophosphamide 250 mg/m2/d D2–3. Serum β2M levels were measured by radioimmunoassay. CrCl was calculated (Cockcroft-Gault equation). Results: The median age was 57 yrs (≥70, 14%). Age ≥70 was associated with fewer FCR courses (p<.0001); lower rates of CR (p=.001), overall response (OR; p=.04), survival (OS; p<.0001), and FFS (p=.008); and higher rates of G3–4 thrombopenia (p<.0001) or anemia (p=.002) compared with age<70. The median CrCl was 90 mL/min (CrCl <70, 27%). Pts with CrCl <70 had higher rates of G3–4 thrombopenia (p=.006) or anemia (p=.01) than others. There were no differences between the 2 groups in the other outcomes. PS was 0 in 40%, 1 in 57%, and 2 in 3% of pts. Better PS was associated with higher rates of CR (p=.007) and FFS (p=.02) but did not affect OR or OS. The median β2M level was 3.7 mg/L (β2M ≥ 4, 43%). The rates of CR, survival, and FFS were lower in pts with β2M ≥ 4 compared with others (p<.0001 each). High β2M levels were associated with older age, lower CrCl levels, poorer PS (p<.0001 each), higher rates of G3–4 neutropenia (p=.005), thrombocytopenia (p=.01), and infections (p=.03), and fewer FCR courses (p=.004). The median follow-up was 5 yrs. The rates of CR, 3-yr OS and 3-yr FFS were 72%, 87% and 76%, respectively. Independent factors predicting response were lower β2M (p=.0004) and lower WBC counts (p=.02). Independent factors predicting longer OS were younger age (p=.001), lower β2M (p=.003) and lower WBC (p=.03). Independent factors predicting longer FFS were lower β2M levels (p=.0006), and lower WBC counts (p=.005). Conclusion: Age ≥70 yrs and poor PS, but not CrCl level were associated with poor clinical outcomes. High β2M levels are an independent adverse prognostic factor for CR, OS, and FFS in the context of other prognostic factors.

No significant financial relationships to disclose.

Salvage therapy following failure or relapse after FCR chemo-immunotherapy as initial treatment for chronic lymphocytic leukemia (CLL)

7009

Background: CLL treatment evolved from single agents to combination chemotherapy to chemo-immunotherapy e.g. fludarabine and rituximab (FR) or with cyclophosphamide (FCR). Reports usually describe initial response, time-to-treatment failure (TTF), and survival. Follow-up of relapsed/failed patients (pts) is rarely reported. This report summarizes our experience with such pts after FCR. Methods: 300 pts initially treated with FCR were analyzed. 15 pts failed, 6 died in remission, six developed Richter's transformation (RT) or another malignancy (14) or relapsed (77). Ten have not required therapy. Results: 67 pts received first salvage therapy (S1) with a variety of regimens. The median age was 59 years and 70% were male. Most pts were Rai stage III - IV (56%). Median TTF after initial FCR was 31 months. Initial FCR responses were CR (36 pts), NPR (10 pts), PR (14 pts), and failure (7 pts). Following S1 therapy, CR was obtained in 17%, NPR (8%) and PR (14%). Initial FCR response of CR or NPR, Rai stage, and β2-microglobulin significantly predicted S1 response. The initial TTF did not predict salvage response. OR rate for FCR-based regimen alone or with alemtuzumab (A) or lumilixamab was 62%, rituximab (R) regimens (31%) and A + R (6/9, 67%). Median survival after S1 therapy was 30 months (28 deaths) and was significantly longer for CR/NPR pts (46 months) than PR/Fail (10 months) P<.001. Duration of initial FCR response, β2-microglobulin level and Rai stage predicted survival (P<.01) but the S1 regimens did not. 9/13 pts who eventually received an allogeneic transplant (allo SCT) are still alive (8 in CR). Conclusions: The results of salvage therapy following FCR initial treatment are unsatisfactory. Patients who failed to obtain a CR or NPR to FCR or S1 therapy should be considered for allo SCT.

No significant financial relationships to disclose.

Seventy percent of complete responders remain in continuous remission: Five-year follow-up of 300 patients treated with fludarabine, cyclophosphamide, and rituximab (FCR) as initial therapy of CLL

7008

Background: The early results of 224 CLL patients receiving the FCR regimen were previously reported (JCO 23:4079). Mature follow-up data (median 62 months for survivors) is now available for the complete cohort of 300 patients. Methods: Eligible patients were =16 years old with previously untreated CLL requiring therapy. Median age was 57 years (31%=60 years, 14% =70 years), and 61% & 36% were in modified Rai intermediate & high risk categories respectively. Prognostic factors: B2m >2x normal 42% (n=295), CD38 positive 28% (n=253), abnormal metaphase cytogenetics 29% (n=221), IgVH unmutated 66% (n=94), ZAP-70 positive 49% (n=88). The planned six cycles of therapy were completed in 74% patients. Results: Responses were: 72% CR, 11% nodular PR (PRn) & 12% PR. On multivariate analysis, CR rates were inferior in patients with B2m >2N (p=0.001) and white cell count >150 × 109/L (p=0.01). Rai stage, CD38 positivity, IGVH mutational status and ZAP-70 positivity were not associated with inferior CR. Median Times to Progression (TTP) were 80 months for CR (n=216), 80 months for PRn (n=32) & 27 months for PR (n=36), with 77%, 65% and 28% projected to be progression-free at five years; projected 5 yr survival were 90%, 81% and 37% respectively. Restricting the analysis to 190 patients with at least five years followup, actual 5 yr TTP and 5yr survival were 70% & 88% respectively in complete responders. Five cases of Richter transformation and eight cases of MDS/AML occurred during remission, with projected 5 yr risk of 2% & 3% respectively. When compared with a historical cohort of patients receiving fludarabine (n=190) or fludarabine and cyclophosphamide/mitoxantrone (n=140) in multivariate analysis, FCR was independently associated with superior TTP (p<0.001) and survival (p<0.001). Conclusion: FCR is the most effective CLL frontline regimen reported to date. 70% of complete responders remain progression-free at five years.

No significant financial relationships to disclose.

A phase I study of the combination of a DNA topoisomerase inhibitor, idarubicin, with the histone deacetylase inhibitor vorinostat, in advanced acute leukemia

7066

Background: Vorinostat (suberoylanilide hydroxamic acid, SAHA) is a histone deacetylase inhibitor (HDACi) with single agent activity in patients with advanced leukemia. HDACi lead to the acetylation of histones and facilitate an open chromatin configuration. Idarubicin potently inhibits DNA topoisomerase (topo) II by forming stable complexes with it, and eventually leading to ds-DNA breaks and apoptosis. Because of their effect on the chromatin of dividing cells, we postulated that the pairing of an HDACi with a topo II inhibitor, would have antileukemia activity. We tested this in vitro in leukemia cell lines and have shown that the combination of idarubicin and SAHA is synergistic. Methods: To test this clinically, we developed a phase I trial of the combination of idarubicin and SAHA, given in 2 different schedules, in advanced leukemia. In schedule A, idarubicin 12 mg/m2 daily for 3 days is given concurrently with SAHA, orally TID for 14 days (starting at 100 mg). In schedule B, SAHA is only given for 3 days. Only SAHA was dose-escalated, following a classic 3+3 schema, with the plan to treat 10 patients at the MTD. If both schedules were open at any given time, patients were randomized among them. Results: So far, 20 patients have been treated: 8 in schedule A and 12 in B. Median age of the patients is 56 (21–80). Of the patients enrolled thus far, 19 (95%) had relapsed, refractory AML, 1 had MDS, and 8 out of the 20 (40%) had diploid cytogenetics. In schedule A, a dose of idarubicin at 12 mg/m2 and SAHA at 100 mg was found to be above the MTD, with the DLT's being myelosuppression, encephalopathy, and dysphagia. Dose escalation of schedule B continues currently at a dose of SAHA at 400 mg. No severe grade 3 or 4 toxicities have been observed on this schedule. No cardiac toxicity has been observed. So far, 2 CR and 2 complete marrow responses have been observed. All of these patients had failed previous anthracycline-based chemotherapy. Induction of γ-H2AX, histone acetylation, and induction of topo II and p21CIP1 mRNA expression are being evaluated, as well as pharmacokinetic characteristics of both agents. Conclusion: The combination of idarubicin with SAHA is safe and active, and SAHA could be incorporated in the treatment of front-line AML.

No significant financial relationships to disclose.

High-dose imatinib mesylate treatment in patients (Pts) with untreated early chronic phase (CP) chronic myeloid leukemia (CML): 2.5-year follow-up

6535

Background: The standard dose (SD) of imatinib for CP CML is currently 400 mg daily, but higher doses (HD) may be more effective. We conducted 2 consecutive trials using HD imatinib (i.e., 400mg twice daily) in previously untreated early CP CML pts. This is an updated analysis of the longer follow-up. Methods: A total of 175 previously untreated pts received HD imatinib. We compared the results with a previous study using SD imatinib (400mg/day) in untreated pts with early CP CML (N=50). Results: Cytogenetic and molecular responses were evaluable in 222 pts (N=49 at SD, 173 at HD) and 217 pts (N=46 at SD, 171 at HD), respectively. In HD group, Sokal risk classification was good in 69%, intermediate in 29%, and poor in 11% of pts. There were no differences in pre-treatment characteristics between two groups. The median age was 48 years in both groups. Median follow-up is 53 months for SD and 30 months for HD group. Patients treated with HD had a higher rate of complete cytogenetic responses (90% vs 78% with SD, p=0.03) and these occurred earlier, with 69% achieving this response after 6 months of therapy vs 45% with SD (p=0.001). The cumulative incidence of major molecular response was significantly better in HD group (p=0.03), and this response was also observed earlier in HD group: at 12 months 54% in HD and 24% in SD group had achieved this response (p=0.001). At 24 months, 19/70 (27%) evaluable pts with HD versus 3/31 (10%) of pts in SD group achieved complete molecular remission. Four pts (2%) in HD group and 4 pts (8%) in SD group have progressed to advanced phases (p=0.05). There was a trend in favor of the HD group for transformation-free-survival but it was not statistically significant (p=0.07). Overall survival is excellent in both groups (24 month survival, 99% with HD vs 98% with SD; p=0.24). Grade 3 or 4 hematologic toxicity was more frequent in HD group whereas extramedullary toxicity was similar in two groups. The median actual dose in HD group was 800 mg at 12 months, with 39% patients requiring dose reduction at some point. Conclusions: High-dose imatinib provides higher rates of complete cytogenetic responses and earlier molecular responses with some increase myelosupression. The long-term benefit of earlier responses remains to be demonstrated.

[Table: see text]

A phase II study of fludarabine (F), cyclophosphamide (C), and mitoxantrone (M) plus rituximab (R) (FCM-R) in previously untreated patients (pts) with CLL ≤ 70 years (yrs)

6607

Background: Rituximab plus chemotherapy has demonstrated higher and better quality responses (MRD-negative) than chemotherapy alone. FCR produced overall response rates of 95% and complete remissions in 73%. Responses were lower in pts ≥ 70 years and β2M levels > 2 × ULN, and myelosuppression-associated complications were more frequent. High response rates of 60% and 88% have been reported with FCM in pts with relapsed and untreated CLL. We here report results of FCM plus rituximab and pegfilgrastim in patients ≤ 70 yrs. with previously untreated CLL. Methods: Pts ≤ 70 yrs with untreated, symptomatic CLL (NCI-WG criteria) were eligible. Pts were excluded for β2M > 2 × ULN and ECOG PS > 2. For course 1, doses of fludarabine were 25 mg/m2 i.v. daily d2–4, cyclophosphamide 250 mg/m2 i.v. daily d2–4, mitoxantrone 6 mg/m2 i.v. d2, and rituximab 375 mg/m2 i.v. d1. Pegfilgrastim was 6 mg s.c. on d4. Courses were repeated q4–6 wks. For courses 2–6, FCM started day 1 with rituximab 500 mg/m2. Study endpoints included evaluation of efficacy (clinical and 2-color flow [CD5/CD19] response rate after 3 and 6 cycles) and toxicity. Results: Twenty-three pts have been treated, 19 are evaluable for response after 3 and 11 pts after 6 cycles. Median age: 57 yrs (38–69). Twelve pts (52%) were male. Rai stage ≥ 3 was present in 17%. Median β2M was 2.7 mg/dL (1.4–4) and median WBC 59.9 × 109/L (5.6–355). Unfavorable FISH abnormalities were present in 3/17 (18%), unmutated IgVH in 9/12 (75%), and ZAP-70 immunohistochemistry was positive in 10/14 (71%) pts. After 3 cycles, all 19 pts responded (4 [21%] CR, 5 [26%] nPR, 10 [53%] PR). Six pts (32%) had <1% CD5/CD19-positive cells in the marrow. Response rates after 6 cycles: 2 (18%) CR, 1 (9%) nPR), 8 (73%) PR (PR due only to failure to recover counts in 7 pts) for an OR rate of 100%. Six pts (55%) had < 1% CD5/CD19-positive marrow cells at 6 months. Only 2 pts stopped prematurely because of persistent neutropenia. Conclusions: FCM-R achieves high clinical response rates. The frequency of pts with flow cytometry response < 1% CD5/CD19-positive cells was similar to FCR. Myelosuppression-related complications were infrequent. Use of hematopoietic growth factors with chemoimmunotherapy regimens is recommended.

[Table: see text]

Dynamics of molecular response to dasatinib (BMS-354825) in patients (pts) with chronic myelogenous leukemia (CML) resistant or intolerant to imatinib

6525

Background: Mutations in the BCR-ABL kinase domain are a common mechanism (40%) of imatinib-resistance. Dasatinib is 300-fold more potent than imatinib against Abl and has activity against all BCR-ABL mutants, except T315I. We investigated the molecular response to dasatinib in pts with CML intolerant or resistant to imatinib. Methods: Fifty-three pts in chronic (CP) (n=29), accelerated (AP) (n=14) and blast (BP) (n=10) phase CML received dasatinib for a median of 22 wks (range, 7 to 42). Pts had received a median of 4 therapies (range, 1 to 8) including imatinib (n=53), IFN (n=32), and AMN107 (n=9). Imatinib was stopped (41 resistant and 12 intolerant) after a median of 34 mo (range, 2.5 to 82). Quantitative reverse transcription PCR in peripheral blood samples was performed prior to dasatinib and every 3 mo thereafter. Median BCR-ABL/ABL ratio (%) at dasatinib start was 78.34 (range, 0.009 to 100). Twenty-four of 42 assessed pts harbored 16 different BCR-ABL mutants. The most common mutations were H396R (n=5), G250E (n=4), and M351T (n=3). Results: BCR-ABL reductions occurred in 48 (90%) pts: <1-log in 12 (23%) pts (7 CP, 2 AP, 3 BP) after a median of 12 wks (range, 4 to 38); >1-log in 15 (28%) pts (5 CP, 6 AP, 4 BP) after a median of 12 wks (range, 4 to 35); >2-logs in 10 (19%) pts (7 CP, 2 AP, 1 BP) after a median of 14.5 wks (range, 4 to 36) and >3-logs in 9 (17%) pts (5CP, 3 AP, 1 BP) after a median of 16 wks (range, 4 to 36). BCR-ABL/ABL ratio <0.05 was seen in 5 (9.5%) CP pts. After a median follow-up of 26 wks (range, 6 to 41), 12 (23%) pts stopped dasatinib due to death (n=2), disease progression (n=6), BMT (n=1), or intolerance (n=3). Dose reductions (31/53, 58%) were associated with BCR-ABL increments in 13 pts (>1 log in 10). Twenty-nine (55%) pts had at least 1 follow-up PCR analysis after their lowest transcript level, and in 9 pts the BCR-ABL/ABL ratio increased >1 log (F359V, Y253H, S348L, H396P, F317L, G250E, F359C), in 4 pts >2 logs (E255V/K, V299L) and in 2 pts >3 logs (F359V, H396R). T315 mutants have not been detected. Conclusion: Dasatinib is associated with significant molecular responses in imatinib-resistant/intolerant CML across multiple BCR-ABL mutants. Longer follow-up is needed to define the stability and durability of these responses.

[Table: see text]

Phase I/II study of the combination of 5-azacytidine(5-AC), all-trans retinoic acid (ATRA) and valproic Acid (VPA) in patients with myelodysplastic syndrome (MDS) and leukemia

6563

Background: The combination of a hypomethylating agent with a histone deacetylase inhibitor (HDACI) has synergistic activity. The combination of ATRA with either a hypomethylating agent or a HDACI restores ATRA sensitivity in resistant cells. The combination of VPA and ATRA has activity in patients with MDS. Based on this, we developed a phase I/II study of the combination of 5-AC, VPA and ATRA for patients with MDS or AML. Methods: The dose of 5-AC was fixed: 75 mg/m2 sq daily × 7. ATRA dose was: 45 mg/m2 orally daily × 5 starting on day 3. Three dose levels of VPA were studied: 50, 62.5 and 75 mg/kg orally daily × 7. The phase I portion of the study followed a 3+3 design. Patients with high risk MDS (≥10% blasts) or relapsed/refractory AML and patients older than 60 years with untreated disease and adequate renal, hepatic functions and performance status were eligible. Results: Nineteen patients were registered and 16 were evaluable. Median age was 68 years (5–78). All, but one patient with MDS had AML. Median number of prior therapies was 2 (0–5). Twelve patients (75%) had abnormal cytogenetics. At a VPA dose of 50 mg/kg, 1 of 6 patients developed grade 3 confusion; at 62.5 mg/kg, 0 of 6, and at 75 mg/kg, 2 of 6. One patient had a CR, 2 a complete marrow response (marrow blasts < 5%), and 1 a CRP (same criteria as of CR but without complete platelet recovery), overall response rate was 30% of 13 patients that have completed 1 course. All 4 responses occurred during the first cycle. The CR occurred at a VPA dose of 75mg/kg. The other 3 responses occurred at 62.5 and 75 mg/kg. One out of 2 previously untreated older patients achieved a CR. To assess the hypomethylating effect of 5-AC, we used the LINE assay. Median LINE methylation pretreatment was 62.5% (57–67%), declined to 58% by day 7 and returned to baseline by day 0 of next cycle (p<0.001). Analysis of histone acetylation and gene re-expression are ongoing. Conclusions: The combination of 5-AC with VPA and ATRA is well tolerated. The dose of 62.5 mg/kg daily × 7 is currently being expanded. Significant clinical activity was observed and the effects are potentially mediated by the synergistic action of the combination including induction of DNA hypomethylation and histone acetylation.

[Table: see text]

The combination of oxaliplatin, fludarabine (FLU), cytarabine (Ara-c), and rituximab (R) (OFAR) in patients with Richter’s Transformation and FLU-refractory CLL

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Background: Patients with (FLU-ref) CLL and Richter’s transformation (RT) have a very poor prognosis. Oxaliplatin (OX), a platinum analog with a 1,2-diaminocyclohexamine carrier ligand, has a different activity and side effect profile from cisplatin. OX covalently binds DNA, inducing DNA intra- and inter-strand cross-links. FLU and Ara-c act synergistically to inhibit excision-repair of DNA cross-links, thereby providing the rationale for combining OX, FLU, Ara-c, and R (OFAR). Methods: The phase I portion of a phase I/II study of the OFAR regimen had increasing doses of OX. The OFAR regimen consists of OX 17.5, 20, or 25mg/m2, d1–4; fludarabine 30mg/m2, d2,3; Ara-c 1gm/m2, d2,3; and rituximab 375mg/m2, d3. Courses were given every 4 wks; patients received Neulasta 6mg each course and prophylaxis for tumor lysis, DNA virus’, and PCP. Results: 19 patients enrolled in phase I; 1 received no treatment, 8 had RT, and 10 had FLU-ref CLL. Patients received OX 17.5mg/m2 (3), 20mg/m2 (8), or 25mg/m2 (7). Patients receiving at least 1 course were evaluable for toxicity and could receive up to 6 courses. There were no dose-limiting toxicities, defined as any ≥ G3, non-hematologic, treatment-related toxicity. The major toxicity was hematologic and appeared OX-dose dependent. Neutropenia (G3–4) was experienced by 1/3, 6/8, and 7/7 patients treated at 17.5, 20, and 25mg/m2 OX levels, respectively. Thrombocytopenia (G3–4) was experienced by 2/3, 8/8, and 7/7 of patients treated at 17.5, 20, and 25mg/m2m OX levels, respectively. There were no treatment-related deaths. Five patients continue treatment on the phase I portion, and results will be evaluable, with 3 responders, including 2 complete, in the 7 evaluable patients with RT. Among the 10 FLU-ref patients, there are 5 PRs; treatment continues for 3 of them. Pharmacodynamic analyses demonstrate enhanced killing by OX in the presence of FLU and Ara-c. Conclusions: The OFAR regimen is safe and active for treating patients with RT and FLU-ref CLL. This trial continues to accrue patients to confirm efficacy.

No significant financial relationships to disclose.