ALBERT

Description: Disease-free survival (DFS) is short in patients ≥ age 60 or with secondary AML, adverse cytogenetics, or leukostasis at presentation. In such patients, median CR duration is ≤ 8 mos and only 20% achieve 1 yr DFS. Historically, maintenance therapy with low doses of cytotoxic chemotherapy has not prolonged DFS. We tested the hypothesis that Tipifarnib (T) might be active as maintenance therapy for adults with poor-risk AML in first CR after induction and consolidation therapies. Oral T 400 mg bid for 2/3 wks was begun median 2.4 mos (range 1.0–4.1) after start of final consolidation cycle and given for up to 48 wks (16 cycles) to 36 adults with median age 63 (range 27–82), secondary AML 31%, adverse cytogenetics 47%, leukostasis 17%, ≥ 2 risk factors 40%. T was well-tolerated, with only 4 of 36 unable to complete 2 cycles because of constitutional symptoms (1 rash, 3 non-compliant). To date, 256 cycles have been administered (median 8 per pt, range 1–16), with hospitalization required during only 4 (1.5%) cycles (infection 3, bowel obstruction 1). Dose reductions for myelosuppression (400 mg bid to 300 mg bid) occurred in 17/32 (53%) by cycle 3, and 2 (6%) needed platelet transfusions. A total of 9 patients completed all planned 16 cycles of T with a median CR duration of 24 mos (range 15–36+). Five of the 9 remain in continuous CR (CCR) 19+-36+ mos, median 26+), compared with 4 who relapsed after CR of 15–24 mos (median 22). There are 8 additional pts in CCR and still receiving T (2–12 cycles) with CCR 4+-12+ mos. A total of 15 patients progressed while on T at median 6.5 mos CR (range 3.5–12). Median CR duration for all patients is 10+ mos (range 3.5–36+), with 88% ≥ 6 mos and 48% ≥ 12 mos. In 13 “comparable” poor-risk pts (age ≥ 60 46%, secondary AML 25%, adverse cytogenetics 46%, leukostasis 23%) who were eligible for but declined T, 4 are in unmaintained CCR at 14+-25+ mos, 9 have relapsed at median 7.5 mos (5–13 mos). Treatment with T did not have a negative impact on reinduction chemotherapy at relapse, as 6 of 9 patients achieved second CR. Administration of T in CR after induction and consolidation therapy has low toxicity and is associated with prolonged DFS in some adults with poor-risk AML. Phase 3 studies are warranted in this patient population.

Description: Background: Loss of the long arm of chromosome (Ch) 5 or complete loss of Ch 5 is frequent in de novo MDS and AML. Epigenetic modifications of tumor suppressor genes, including aberrant DNA methylation, may play an important role in the progression of MDS and AML. Cell signaling is regulated by a-catenin, which forms a trimolecular complex with E-cadherin (ECAD) and b-catenin that links with actin-containing filaments of the cytoskeleton. Studies have reported reduced expression of a-catenin in MDS and AML patients with 5q deletion as compared to those without 5q deletion. Whether promoter methylation of the a-catenin gene is responsible for this decreased expression is controversial. To explore the potential role of a-catenin in the pathogenesis of AML transformation, we (a) determined the tumor specificity of methylation in AML and non- myeloid malignancies and (b) frequency of methylation in patients with −5/del(5q) MDS/AML and those with normal cytogenetics; (c) performed bioinformatics and experimental analysis of the a-catenin adhesion complex and local 5q31.1 genes to investigate mechanisms of epigenetic silencing; and (d) performed a detailed analysis of primary AML samples correlating promoter methylation, a-catenin expression, and chromatin conformation. Methods and Results: Using methylation sensitive PCR, we found that methylation of the a-catenin promoter gene was specific for myeloid malignancy. No methylation was observed in 19 acute lymphocytic leukemia cases, 20 chronic myelogenous leukemia cases, or in 99 primary gastric and esophageal samples where a-catenin has been implicated as a tumor suppressor gene. In those patients with AML and an associated 5q deletion the frequency was 31% (8/26) as compared to those without a 5q deletion with 13% (16/120). Bioinformatics analyses of the Valk et al., 2004 leukemia database provide supportive data for under expression of a-catenin in non-5/del (5q) AML cases. We quantitated a-catenin mRNA expression by Q-PCR in our cohort. Expression was lowest in AML patients with a-catenin methylation (n=9), but also in a subset of patients without promoter methylation (n=17), suggesting alternative mechanisms of inactivation. In contrast to AML, methylation of a-catenin was rare in myelodysplastic syndrome (MDS). Although p15 was methylated in over 50% of these cases as a positive control, only 2/18 MDS cases with 5q deletion (11%) and 1/13 MDS cases with 5q intact (8%) were methylated at the a-catenin promoter. The three positive cases were RAEB-2 (1) or RAEB-t (2), suggesting that a-catenin methylation may be most important in promoting transformation from MDS to AML. To explain a potential lack of correlation of methylation with decreased a-catenin in MDS and AML, we investigated a-catenin chromatin in a myeloid stem cell progression model and in primary AML samples. We performed chromatin immunoprecipitation on the CTNNA1 promoter using two active chromatin histone marks, H3K9Ac and H3K4me2 and two inactive marks, H3K9me2 and H3K27me3. In cell lines and primary leukemia samples where a-catenin was highly expressed (N=4), activation marks were present and repression marks absent. In cell lines and primary samples with low a-catenin expression and methylation of the promoter (N=4), the opposite pattern was observed. So called “bivalent” chromatin with mixed marks, no a-catenin methylation, and intermediated mRNA expression levels were observed with 7 additional cases (2 cell lines, 5 primary AML). Conclusions: Our data indicate that methylation of a-catenin is common in AML patients with 5q deletion but also observed in cases with normal chromosome 5 copy number. We propose a model of progressive inactivation of the a-catenin locus with AML transformation, with methylation representing a late stage event. The tissue-specificity of our results and in vivo chromatin observations in primary AML samples have implications for the timing and combinatorial therapy of MDS/AML with HDAC inhibitors and methylation inhibitors. Additionally, it appears that inactivation of adhesion molecules (ECAD, a-catenin) are frequent events overall in AML, suggesting a new pathway of transformation from MDS to AML.

Description: Although most patients with cancer respond to therapy, few are cured. Moreover, objective clinical responses to treatment often do not even translate into substantial improvements in overall survival. For example, patients with indolent lymphoma who achieved a complete remission with conventional-dose therapies in the prerituximab era did not experience a survival advantage over similar patients treated with a “watch and wait” approach. Several studies have also shown that neither the magnitude nor the kinetics of clinical response has an impact on survival in multiple myeloma. Recent data suggesting many malignancies arise from a rare population of cells that exclusively maintains the ability to self-renew and sustains the tumor (ie, “cancer stem cells”) may help explain this paradox that response and survival are not always linked. Therapies that successfully eliminate the differentiated cancer cells characterizing the tumor may be ineffective against rare, biologically distinct cancer stem cells. New methods for assessing treatment efficacy must also be developed, as traditional response criteria measure tumor bulk and may not reflect changes in rare cancer stem cell populations. In this article, we discuss the evidence for cancer stem cells in hematologic malignancies and possible ways to begin targeting these cells and measuring clinical effectiveness of such treatment approaches.

Description: Based on our results in animal models and promising results in HLA-haploidentical setting (L. Luznik, Blood 2002 and BBMT 2008), we studied whether high dose Cy alone is sufficient as GVHD prophylaxis after myeloablative HLA-matched related or unrelated BMT in patients with advanced, poor risk, hematologic malignancies. One hundred and seventeen consecutive patients (median age 48, range 23–65; 36 de novo AML, 23 2° AML (arising from previous MDS/MPD or therapy-related), 13 high-risk MDS, 9 ALL, 8 CML, 3 CLL, 5 MM, 9 NHL and 11 HL), of whom the majority (57%) were not in remission, received HLA-matched related (n=78) or unrelated (n=39) BMT. Conditioning consisted of oral or IV busulfan (pharmacokinetically adjusted) on days −7 to −3 and Cy (50 mg/kg/day) on days −2 and −1. Cy (50 mg/kg/day) was also given on days +3, and +4 as a sole agent for GVHD prophylaxis. All patients received bone marrow allografts without growth factor support. Three patients failed to engraft, but two were successfully rescued with a second allograft. The cumulative incidence of non-relapse mortality (NRM) at day 100 and 1 year after transplantation was 8.5% and 16%, respectively. Of the 18 patients dying of NRM, 2 were from VOD, 3 from non infectious pneumonia, 3 were from GVHD, 3 from sepsis/bacterial infections, 4 from MOF, and 3 of CNS/organ hemorrhage. The incidences of acute grade II–IV and grade III–IV GVHD were 43% and 11%, respectively. With a median follow-up of 19 months, 66 (56.4%) patients are alive, of whom 52 (44.4%) are in complete remission. Only 7/66 related and 4/32 unrelated patients developed chronic GVHD (classic limited in 7, overlap syndrome limited in 1, and classic extensive in 3 patients). Since in a competing risk model (relapse and death as competing risks) the cumulative incidence of chronic GVHD remained low, we analyzed the impact of the preceding history of acute GVHD and systemic immunosuppressive treatment given beyond the originally prescribed prophylaxis with high dose Cy on the incidence of chronic GVHD. Only one patient without a preceding history of acute GVHD developed de novo chronic GVHD. Overall, 3 patients with grade II–IV acute GVHD were untreated, 10 patients received steroids alone, 31 received steroids + a calcineurin inhibitor (CNI), and 7 received steroids + non CNI-based agents. The use of CNI for the treatment of acute GVHD did not appear to influence the development of chronic GVHD: 6/31 (19%) patients who received CNI-based immunosuppressive treatment developed chronic GVHD compared to 3/20 (15%) patients who did not. These results suggest that highdose of post-transplantation Cy is effective as the sole prophylaxis for acute and chronic GVHD after HLA-matched related or unrelated BMT. This approach is associated with rapid immunologic recovery as indicated by the low incidence of opportunistic infections, as well as a low incidence of acute and especially chronic GVHD. Further clinical and correlative studies are needed to elucidate the mechanisms behind the unique effectiveness of post-transplantation Cy on the prevention of acute and chronic GVHD.

Description: We have developed a useful surrogate assay for monitoring the efficacy of FLT3 inhibition in patients treated with oral FLT3 inhibitors. The plasma inhibitory activity (PIA) for FLT3 correlates with clinical activity in patients treated with CEP-701 and PKC412. Using the PIA assay, along with in vitro phosphorylation and cytotoxicity assays in leukemia cells, we compared PKC412 and its metabolite, CGP52421, with CEP-701. While both drugs could effectively inhibit FLT3 in vitro, CEP-701 was more cytotoxic to primary samples at comparable levels of FLT3 inhibition. PKC412 appears to be more selective than CEP-701 and therefore less effective at inducing cytotoxicity in primary acute myeloid leukemia (AML) samples in vitro. However, the PKC412 metabolite CGP52421 is less selective than its parent compound, PKC412, and is more cytotoxic against primary blast samples at comparable levels of FLT3 inhibition. The plasma inhibitory activity assay represents a useful correlative tool in the development of small-molecule inhibitors. Our application of this assay has revealed that the metabolite CGP52421 may contribute a significant portion of the antileukemia activity observed in patients receiving oral PKC412. Additionally, our results suggest that nonselectivity may constitute an important component of the cytotoxic effect of FLT3 inhibitors in FLT3-mutant AML.

Description: The farnesyltransferase inhibitor tipifarnib exhibits modest activity against acute myelogenous leukemia. To build on these results, we examined the effect of combining tipifarnib with other agents. Tipifarnib inhibited signaling downstream of the farnesylated small G protein Rheb and synergistically enhanced etoposide-induced antiproliferative effects in lymphohematopoietic cell lines and acute myelogenous leukemia isolates. We subsequently conducted a phase 1 trial of tipifarnib plus etoposide in adults over 70 years of age who were not candidates for conventional therapy. A total of 84 patients (median age, 77 years) received 224 cycles of oral tipifarnib (300-600 mg twice daily for 14 or 21 days) plus oral etoposide (100-200 mg daily on days 1-3 and 8-10). Dose-limiting toxicities occurred with 21-day tipifarnib. Complete remissions were achieved in 16 of 54 (30%) receiving 14-day tipifarnib versus 5 of 30 (17%) receiving 21-day tipifarnib. Complete remissions occurred in 50% of two 14-day tipifarnib cohorts: 3A (tipifarnib 600, etoposide 100) and 8A (tipifarnib 400, etoposide 200). In vivo, tipifarnib plus etoposide decreased ribosomal S6 protein phosphorylation and increased histone H2AX phosphorylation and apoptosis. Tipifarnib plus etoposide is a promising orally bioavailable regimen that warrants further evaluation in elderly adults who are not candidates for conventional induction chemotherapy. These clinical studies are registered at www.clinicaltrials.gov as #NCT00112853.

Description: Previous studies demonstrated that ataxia telangiectasia mutated– and Rad3-related (ATR) kinase and its downstream target checkpoint kinase 1 (Chk1) facilitate survival of cells treated with nucleoside analogs and other replication inhibitors. Recent results also demonstrated that Chk1 is depleted when cells are treated with heat shock protein 90 (Hsp90) inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG). The present study examined the effects of 17-AAG and its major metabolite, 17-aminogeldanamycin (17-AG), on Chk1 levels and cellular responses to cytarabine in human acute myelogenous leukemia (AML) cell lines and clinical isolates. Cytarabine, at concentrations as low as 30 nM, caused activating phosphorylation of Chk1, loss of the phosphatase Cdc25A, and S-phase slowing. Conversely, treatment with 100 to 300 nM 17-AAG for 24 hours caused Chk1 depletion that was accompanied by diminished cytarabine-induced S-phase accumulation, decreased Cdc25A degradation, and enhanced cytotoxicity as measured by inhibition of colony formation and induction of apoptosis. Additional studies demonstrated that small inhibitory RNA (siRNA) depletion of Chk1 also sensitized cells to cytarabine, whereas disruption of the phosphatidylinositol 3-kinase (PI3k) signaling pathway, which is also blocked by Hsp90 inhibition, did not. Collectively, these results suggest that treatment with 17-AAG might represent a means of reversing checkpoint-mediated cytarabine resistance in AML.

Description: Telomerase activity (TA) is required within normal cells capable of long-term replication, including stem cells and is upregulated in many cancers. In the absence of TA or presence of TA inhibitors, the progressive shortening of telomeres ultimately results in cellular senescence and/or apoptosis. These observations support that TA inhibitors represent a novel class of anti-tumor agents. Much evidence suggests that human cancers display a hierarchical cellular organization that mirrors normal tissues. Cancer stem cells (CSC) are derived from the malignant transformation of normal stem cells and progenitors and retain the capacity to self-renew. Moreover, CSC give rise to differentiated tumor cells that form the bulk of the tumor mass, but have little or no capacity for long-term proliferation. We recently demonstrated that the malignant CD138+ plasma cells in multiple myeloma (MM) have limited replicative potential; instead they arise from the differentiation of clonogenic CSC that resemble normal memory B cells (CD138negCD19+CD27+). In addition, several groups have demonstrated that telomerase inhibitors are active against human MM cell lines in vitro and in vivo. We examined TA in CD138+ plasma cells and CD138neg precursors, and studied the effects of telomerase inhibition against both cell populations. We isolated CD138+ and CD138neg cells by FACS from three human MM cell lines (RPMI 8225, NCI-H929, and U266) and measured TA using a PCR-based assay of activity. For each cell line, TA was detectable within both the CD138neg and CD138+ cell populations. GRN163L is a lipid conjugated 13 nucleotide thio-phosphoramidate oligonucleotide that acts as a potent and specific active site inhibitor of telomerase. We found that treatment with GRN163L (0.1–5μM) markedly reduced TA within 48 hours. To examine the effects of telomerase inhibition on clonogenic growth, we continuously cultured CD138+ and CD138neg RPMI 8226 cells with GRN163L (1μM). Cells were collected weekly, washed to remove GRN163L, and then plated in methylcellulose to assess colony formation. We found that GRN163L was active against both CD138+ and CD138neg cells and eliminated the colony forming potential of both by 5 weeks. Similarly, we found that GRN163L inhibited the in vitro clonogenic growth of CD138neg MM CSC isolated from the bone marrow aspirates of patients with MM. These data demonstrate that TA is detectable within both immature MM CSC and mature MM plasma cells, and that CSC from both cell lines and primary clinical samples are targeted by the telomerase inhibitor GRN163L. Therefore, this agent may offer a novel therapeutic approach to myeloma as well as other diseases in which CSC have been identified.

Description: Myelodysplastic syndromes (MDS) are a complex and heterogeneous group of hematopoietic stem cell malignancies that are generally incurable outside allo BMT. The toxicities of allo BMT, specifically graft-vs-host disease (GVHD) and end organ toxicity, have limited its use in this traditionally older group of patients (pts) who often have medical co-morbidities. Efforts to apply allo BMT to more pts have focused on reducing the toxicities. Graft manipulation, including TCD, and reduced-intensity conditioning (RIC) regimens have been shown to decrease the upfront mortality of allo BMT; yet improvements in overall survival have been limited due to associated increased post-BMT relapse rates and increased graft failure. Myeloid growth factors have been used commonly, though not systematically, following allo BMT to speed engraftment. Our data, and that of others, suggest that myeloid growth factors may also have anti-tumor properties in MDS by impacting differentiation pathways and/or through their immunomodulatory effects. We developed a clinical trial to determine if the addition of GM-CSF could safely decrease the relapse rate following a TCD allo BMT in pts with high risk MDS. Pts with MDS ≤ 65 undergoing evaluation for a matched sibling allo BMT at the Sidney Kimmel Cancer Center at Johns Hopkins were considered eligible. Pts received a TCD allograft (elutriation and CD34 isolation) following a myeloablative busulfan/cytoxan preparative regimen; GM-CSF @ 250 mcg/m2/day from Day +5 until ANC 〉2000/m3 × 3 days and then 125mcg/m2/day subcutaneously thru Day +60. A total of 43 pts were treated on the protocol with a median age of 56 (range 30 to 65) yrs. Forty pts had poor risk MDS (cytogenetics and IPSS) and 3 pts had AML upon retrospective pathology review. The addition of GM-CSF was well tolerated post-allo BMT with only 1 pt unable to complete the full dose, planned therapy. The overall survival @ 1 and 3 years was 54% and 50% respectively while the event free survival @ 1 and 3 years was 47% and 33% respectively with median follow-up in the surviving group of 37.5 months. Treatment related toxicity was low with a 9% cumulative incidence of grade III/IV aGVHD and a transplant-related mortality (TRM) of 21% (9/43) with 4 deaths related to GVHD, 4 related to engraftment, and 1 secondary to venoocclusive disease. Cumulative incidence of relapse at data analysis was 40% (17/43) with one patient achieving remission after donor lymphocyte infusion. Engraftment failure was seen in only 9% (4/43) of pts. Taken together, ablative preparative regimens followed by TCD allo BMT can safely be used in older MDS pts with the addition of GM-CSF resulting in acceptable engraftment without increased toxicity. Myeloablative conditioning with TCD and prolonged post-transplant GM-CSF produced favorable results in this group of older, high-risk MDS patients. The role of high dose conditioning for alloBMT for MDS is unclear, but the TRM was similar to the low mortality reported with RIC regimens, and the graft failure and relapse rates may be superior.