Sustained remissions in CLL after frontline FCR treatment with very-long-term follow-up.

Chemoimmunotherapy with fludarabine, cyclophosphamide, and rituximab (FCR) achieves durable remissions, with flattening of the progression-free survival (PFS) curve in patients with mutated immunoglobulin heavy chain variable gene (IGHV-M). We updated long-term follow-up results from the original 300-patient FCR study initiated at MD Anderson in 1999. The current median follow-up is 19.0 years. With this extended follow-up, the median PFS for patients with IGHV-M was 14.6 years vs 4.2 years for patients with unmutated IGHV (IGHV-UM). Disease progression beyond 10 years was uncommon. In total, 16 of 94 (17%) patients in remission at 10 years subsequently progressed with the additional follow-up compared with the patients in our prior report in 2015. Only 4 of 45 patients (9%) with IGHV-M progressed beyond 10 years. Excluding Richter transformation, 96 of 300 patients (32%) developed 106 other malignancies, with 19 of 300 (6.3%) developing therapy-related myeloid neoplasms (tMNs), which were fatal in 16 of 19 (84%). No pretreatment patient characteristics predicted the risk of tMNs. In summary, FCR remains an option for patients with IGHV-M chronic lymphocytic leukemia (CLL), with a significant fraction achieving functional cure of CLL. A risk-benefit assessment is warranted when counseling patients, balancing potential functional cure with the risk of late relapses and serious secondary malignancies.

Cyclin-dependent kinase inhibitor fadraciclib (CYC065) depletes anti-apoptotic protein and synergizes with venetoclax in primary chronic lymphocytic leukemia cells.

Fadraciclib (CYC065) is a second-generation aminopurine CDK2/9 inhibitor with increased potency and selectivity toward CDK2 and CDK9 compared to seliciclib (R-roscovitine). In chronic lymphocytic leukemia (CLL), a disease that depends on the over-expression of anti-apoptotic proteins for its survival, inhibition of CDK9 by fadraciclib reduced phosphorylation of the C-terminal domain of RNA polymerase II and blocked transcription in vitro; these actions depleted the intrinsically short-lived anti-apoptotic protein Mcl-1 and induced apoptosis. While the simulated bone marrow and lymph node microenvironments induced Mcl-1 expression and protected CLL cells from apoptosis, these conditions did not prolong the turnover rate of Mcl-1, and fadraciclib efficiently abrogated the protective effect. Further, fadraciclib was synergistic with the Bcl-2 antagonist venetoclax, inducing more profound CLL cell death, especially in samples with 17p deletion. While fadraciclib, venetoclax, and the combination each had distinct kinetics of cell death induction, their activities were reversible, as no additional cell death was induced upon removal of the drugs. The best combination effects were achieved when both drugs were maintained together. Altogether, this study provides a rationale for the clinical development of fadraciclib in CLL, either alone or in combination with a Bcl-2 antagonist.

Ibrutinib Plus Venetoclax for First-line Treatment of Chronic Lymphocytic Leukemia: A Nonrandomized Phase 2 Trial.

IMPORTANCE: Oral targeted therapies have advanced the treatment of chronic lymphocytic leukemia (CLL). These therapies include Bruton tyrosine kinase inhibitors, used as monotherapy, and the Bcl-2 inhibitor venetoclax, typically combined with the CD20 monoclonal antibody. Preclinical studies have shown synergy between Bruton tyrosine kinase inhibitors and the Bcl-2 inhibitor venetoclax. OBJECTIVE: To examine the rate of complete remission, complete remission with incomplete count recovery, and bone marrow-undetectable measurable residual disease (U-MRD) after treatment with the combination of ibrutinib and venetoclax. DESIGN, SETTING, AND PARTICIPANTS: A single-center, phase 2 nonrandomized trial enrolled patients from August 17, 2016, to June 5, 2018. Participants included previously untreated patients with CLL who met International Workshop on CLL 2008 criteria for treatment indication. Patients were required to have at least 1 of the following features: del(17p), TP53-mutated CLL, del(11q), unmutated immunoglobulin heavy-chain variable gene, or age 65 years or older. INTERVENTIONS: Therapy consisted of ibrutinib, 420 mg/d, monotherapy for 3 cycles, thereafter combined with venetoclax (standard weekly dose ramp-up to 400 mg/d) for a total of 24 cycles of combination treatment. Responses were assessed at serial points according to International Workshop on CLL 2008 criteria. Measurable residual disease (MRD) was assessed by multicolor flow cytometry with a sensitivity of 10-4. MAIN OUTCOMES AND MEASURES: Outcomes included complete remission, complete remission with incomplete count recovery, and bone marrow U-MRD rate. RESULTS: Eighty patients (57 [71%] men) were treated; median age was 65 years (range, 26-83 years). The median follow-up for all 80 patients was 38.5 months (range, 5.6-51.1 months). Five patients discontinued the study during the ibrutinib monotherapy phase; the remaining 75 patients received combination therapy. On an intent-to-treat analysis of combined treatment, 45 (56%) patients achieved bone marrow U-MRD remission at 12 cycles and 53 (66%) patients achieved bone marrow U-MRD remission at 24 cycles. Overall, 60 (75%) patients achieved bone marrow U-MRD remission as their best response. Responses were seen across all high-risk subgroups, independent of the immunoglobulin heavy-chain variable gene mutation status, fluorescence in situ hybridization category, or TP53 mutation. The 3-year progression-free survival was 93%, and 3-year overall survival was 96%. No patient had CLL progression; 2 patients developed Richter transformation. CONCLUSIONS AND RELEVANCE: The findings of this study suggest that combination therapy with ibrutinib and venetoclax might be beneficial for previously untreated patients with CLL. Remissions appeared to be durable during a follow-up of more than 3 years, with activity seen across high-risk disease subgroups, including those with del(17p)/TP53-mutated CLL. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02756897.

Ibrutinib, fludarabine, cyclophosphamide, and obinutuzumab (iFCG) regimen for chronic lymphocytic leukemia (CLL) with mutated IGHV and without TP53 aberrations.

Chemoimmunotherapy with combined fludarabine, cyclophosphamide and rituximab (FCR) has been an effective treatment for patients with chronic lymphocytic leukemia (CLL). We initiated a phase II trial for previously untreated patients with CLL with mutated IGHV and absence of del(17p)/TP53 mutation. Patients received ibrutinib, fludarabine, cyclophosphamide, and obinutuzumab (iFCG) for three cycles. Patients who achieved complete remission (CR)/CR with incomplete count recvoery (CRi) with marrow undetectable measurable residual disease (U-MRD) received additional nine cycles of ibrutinib with three cycles of obinutuzumab; all others received nine additional cycles of ibrutinib and obinutuzumab. Patients in marrow U-MRD remission after cycle 12 discontinued all treatment, including ibrutinib. Forty-five patients were treated. The median follow-up is 41.3 months. Among the total 45 treated patients, after three cycles, 38% achieved CR/CRi and 87% achieved marrow U-MRD. After cycle 12, the corresponding numbers were 67% and 91%, respectively. Overall, 44/45 (98%) patients achieved marrow U-MRD as best response. No patient had CLL progression. The 3-year progression-free survival (PFS) and overall survival (OS) were 98% and 98%, respectively. Per trial design, all patients who completed cycle 12 discontinued ibrutinib, providing for a time-limited therapy. Grade 3-4 neutropenia and thrombocytopenia occurred in 58% and 40% patients, respectively. The iFCG regimen with only 3 cycles of chemotherapy is an effective, time-limited regimen for patients with CLL with mutated IGHV and without del(17p)/TP53 mutation.

The multi-kinase inhibitor TG02 induces apoptosis and blocks B-cell receptor signaling in chronic lymphocytic leukemia through dual mechanisms of action.

The constitutive activation of B-cell receptor (BCR) signaling, together with the overexpression of the Bcl-2 family anti-apoptotic proteins, represents two hallmarks of chronic lymphocytic leukemia (CLL) that drive leukemia cell proliferation and sustain their survival. TG02 is a small molecule multi-kinase inhibitor that simultaneously targets both of these facets of CLL pathogenesis. First, its inhibition of cyclin-dependent kinase 9 blocked the activation of RNA polymerase II and transcription. This led to the depletion of Mcl-1 and rapid induction of apoptosis in the primary CLL cells. This mechanism of apoptosis was independent of CLL prognostic factors or prior treatment history, but dependent on the expression of BAX and BAK. Second, TG02, which inhibits the members of the BCR signaling pathway such as Lck and Fyn, blocked BCR-crosslinking-induced activation of NF-κB and Akt, indicating abrogation of BCR signaling. Finally, the combination of TG02 and ibrutinib demonstrated moderate synergy, suggesting a future combination of TG02 with ibrutinib, or use in patients that are refractory to the BCR antagonists. Thus, the dual inhibitory activity on both the CLL survival pathway and BCR signaling identifies TG02 as a unique compound for clinical development in CLL and possibly other B cell malignancies.

Repair of DNA damage induced by the novel nucleoside analogue CNDAG through homologous recombination.

PURPOSE: We postulate that the deoxyguanosine analogue CNDAG [9-(2-C-cyano-2-deoxy-1-ß-D-arabino-pentofuranosyl)guanine] likely causes a single-strand break after incorporation into DNA, similar to the action of its cytosine congener CNDAC, and that subsequent DNA replication across the unrepaired nick would generate a double-strand break. This study aimed at identifying cellular responses and repair mechanisms for CNDAG prodrugs, 2-amino-9-(2-C-cyano-2-deoxy-1-ß-D-arabino-pentofuranosyl)-6-methoxy purine (6-OMe) and 9-(2-C-cyano-2-deoxy-1-ß-D-arabino-pentofuranosyl)-2,6-diaminopurine (6-NH2). Each compound is a substrate for adenosine deaminase, the action of which generates CNDAG. METHODS: Growth inhibition assay, clonogenic survival assay, immunoblotting, and cytogenetic analyses (chromosomal aberrations and sister chromatid exchanges) were used to investigate the impact of CNDAG on cell lines. RESULTS: The 6-NH2 derivative was selectively potent in T cell malignant cell lines. Both prodrugs caused increased phosphorylation of ATM and its downstream substrates Chk1, Chk2, SMC1, NBS1, and H2AX, indicating activation of ATM-dependent DNA damage response pathways. In contrast, there was no increase in phosphorylation of DNA-PKcs, which participates in repair of double-strand breaks by non-homologous end-joining. Deficiency in ATM, RAD51D, XRCC3, BRCA2, and XPF, but not DNA-PK or p53, conferred significant clonogenic sensitivity to CNDAG or the prodrugs. Moreover, hamster cells lacking XPF acquired remarkably more chromosomal aberrations after incubation for two cell cycle times with CNDAG 6-NH2, compared to the wild type. Furthermore, CNDAG 6-NH2 induced greater levels of sister chromatid exchanges in wild-type cells exposed for two cycles than those for one cycle, consistent with increased double-strand breaks after a second S phase. CONCLUSION: CNDAG-induced double-strand breaks are repaired mainly through homologous recombination.

Trabectedin Reveals a Strategy of Immunomodulation in Chronic Lymphocytic Leukemia.

Chronic lymphocytic leukemia (CLL) is a B-cell neoplasia characterized by protumor immune dysregulation involving nonmalignant cells of the microenvironment, including T lymphocytes and tumor-associated myeloid cells. Although therapeutic agents have improved treatment options for CLL, many patients still fail to respond. Some patients also show immunosuppression. We have investigated trabectedin, a marine-derived compound with cytotoxic activity on macrophages in solid tumors. Here, we demonstrate that trabectedin induces apoptosis of human primary leukemic cells and also selected myeloid and lymphoid immunosuppressive cells, mainly through the TRAIL/TNF pathway. Trabectedin modulates transcription and translation of IL6, CCL2, and IFNα in myeloid cells and FOXP3 in regulatory T cells. Human memory CD8+ T cells downregulate PD-1 and, along with monocytes, exert in vivo antitumor function. In xenograft and immunocompetent CLL mouse models, trabectedin has antileukemic effects and antitumor impact on the myeloid and lymphoid cells compartment. It depletes myeloid-derived suppressor cells and tumor-associated macrophages and increases memory T cells. Trabectedin also blocks the PD-1/PD-L1 axis by targeting PD-L1+ CLL cells, PD-L1+ monocytes/macrophages, and PD-1+ T cells. Thus, trabectedin behaves as an immunomodulatory drug with potentially attractive therapeutic value in the subversion of the protumor microenvironment and in overcoming chemoimmune resistance.

CNDAC-Induced DNA Double-Strand Breaks Cause Aberrant Mitosis Prior to Cell Death.

Incorporation of the clinically active deoxycytidine analogue 2'-C-cyano-2'-deoxy-1-ß-D-arabino-pentofuranosyl-cytosine (CNDAC) into DNA generates single-strand breaks that are subsequently converted to double-strand breaks (DSB). Here, we investigated the cellular manifestations of these breaks that link these mechanisms to cell death, and we further tested the relevance of DNA repair pathways in protection of cells against CNDAC damage. The present investigations demonstrate that following exposure to CNDAC and a wash into drug-free medium, chromosomal aberrations, DNA strand breaks, and multinucleate cells arose. These portended loss of viability and were dependent upon exposure time, CNDAC concentration, and passage through mitosis. Following a pulse incubation with CNDAC, live cell imaging using GFP-tagged histone H2B as a marker demonstrated a normal rate of progression to mitosis, but a concentration-dependent delay in passage to a second mitosis. Progression through mitosis was also delayed and accompanied by formation of multinucleate cells. CNDAC-treated cells lacking XPF-ERCC1 nuclease function showed a 16-fold increase in chromosome aberrations. Chromosomal damage in Rad51D-mutant cells (homologous recombination repair deficient) were even more severely affected with extensive aberrations. Rodent or human Polq (POLQ) mutant cells, defective in Pol θ-mediated alternative end joining, did not show enhanced cellular sensitivity to CNDAC. These findings are consistent with formation of DSBs in the second S-phase following exposure, resulting in chromosome aberrations, aberrant mitoses, and subsequent apoptosis.

Oncogenic KRAS Reduces Expression of FGF21 in Acinar Cells to Promote Pancreatic Tumorigenesis in Mice on a High-Fat Diet.

BACKGROUND & AIMS: Obesity is a risk factor for pancreatic cancer. In mice, a high-fat diet (HFD) and expression of oncogenic KRAS lead to development of invasive pancreatic ductal adenocarcinoma (PDAC) by unknown mechanisms. We investigated how oncogenic KRAS regulates the expression of fibroblast growth factor 21, FGF21, a metabolic regulator that prevents obesity, and the effects of recombinant human FGF21 (rhFGF21) on pancreatic tumorigenesis. METHODS: We performed immunohistochemical analyses of FGF21 levels in human pancreatic tissue arrays, comprising 59 PDAC specimens and 45 nontumor tissues. We also studied mice with tamoxifen-inducible expression of oncogenic KRAS in acinar cells (KrasG12D/+ mice) and fElasCreERT mice (controls). KrasG12D/+ mice were placed on an HFD or regular chow diet (control) and given injections of rhFGF21 or vehicle; pancreata were collected and analyzed by histology, immunoblots, quantitative polymerase chain reaction, and immunohistochemistry. We measured markers of inflammation in the pancreas, liver, and adipose tissue. Activity of RAS was measured based on the amount of bound guanosine triphosphate. RESULTS: Pancreatic tissues of mice expressed high levels of FGF21 compared with liver tissues. FGF21 and its receptor proteins were expressed by acinar cells. Acinar cells that expressed KrasG12D/+ had significantly lower expression of Fgf21 messenger RNA compared with acinar cells from control mice, partly due to down-regulation of PPARG expression-a transcription factor that activates Fgf21 transcription. Pancreata from KrasG12D/+ mice on a control diet and given injections of rhFGF21 had reduced pancreatic inflammation, infiltration by immune cells, and acinar-to-ductal metaplasia compared with mice given injections of vehicle. HFD-fed KrasG12D/+ mice given injections of vehicle accumulated abdominal fat, developed extensive inflammation, pancreatic cysts, and high-grade pancreatic intraepithelial neoplasias (PanINs); half the mice developed PDAC with liver metastases. HFD-fed KrasG12D/+ mice given injections of rhFGF21 had reduced accumulation of abdominal fat and pancreatic triglycerides, fewer pancreatic cysts, reduced systemic and pancreatic markers of inflammation, fewer PanINs, and longer survival-only approximately 12% of the mice developed PDACs, and none of the mice had metastases. Pancreata from HFD-fed KrasG12D/+ mice given injections of rhFGF21 had lower levels of active RAS than from mice given vehicle. CONCLUSIONS: Normal acinar cells from mice and humans express high levels of FGF21. In mice, acinar expression of oncogenic KRAS significantly reduces FGF21 expression. When these mice are placed on an HFD, they develop extensive inflammation, pancreatic cysts, PanINs, and PDACs, which are reduced by injection of FGF21. FGF21 also reduces the guanosine triphosphate binding capacity of RAS. FGF21 might be used in the prevention or treatment of pancreatic cancer.

Ibrutinib and Venetoclax for First-Line Treatment of CLL.

BACKGROUND: Ibrutinib, an inhibitor of Bruton's tyrosine kinase, and venetoclax, an inhibitor of B-cell lymphoma 2 protein, have been approved for patients with chronic lymphocytic leukemia (CLL). Preclinical investigations have indicated potential synergistic interaction of their combination. METHODS: We conducted an investigator-initiated phase 2 study of combined ibrutinib and venetoclax involving previously untreated high-risk and older patients with CLL. All patients had at least one of the following features: chromosome 17p deletion, mutated TP53, chromosome 11q deletion, unmutated IGHV, or an age of 65 years or older. Patients received ibrutinib monotherapy (420 mg once daily) for 3 cycles, followed by the addition of venetoclax (weekly dose escalation to 400 mg once daily). Combined therapy was administered for 24 cycles. Response assessments were performed according to International Workshop on Chronic Lymphocytic Leukemia 2008 criteria. Minimal residual disease was assessed by means of multicolor flow cytometry in bone marrow (sensitivity, 10-4). RESULTS: A total of 80 patients were treated. The median age was 65 years (range, 26 to 83). A total of 30% of the patients were 70 years of age or older. Overall, 92% of the patients had unmutated IGHV, TP53 aberration, or chromosome 11q deletion. With combined treatment, the proportions of patients who had complete remission (with or without normal blood count recovery) and remission with undetectable minimal residual disease increased over time. After 12 cycles of combined treatment, 88% of the patients had complete remission or complete remission with incomplete count recovery, and 61% had remission with undetectable minimal residual disease. Responses were noted in older adults and across all high-risk subgroups. Three patients had laboratory evidence of tumor lysis syndrome. The adverse-event profile was similar to what has been reported with ibrutinib and venetoclax. CONCLUSIONS: In this study, combined venetoclax and ibrutinib was an effective oral regimen for high-risk and older patients with CLL. (Funded by AbbVie and others; ClinicalTrials.gov number, NCT02756897.).

Creating novel translation inhibitors to target pro-survival proteins in chronic lymphocytic leukemia.

The viability of chronic lymphocytic leukemia (CLL) is critically dependent upon staving off death by apoptosis, a hallmark of CLL pathophysiology. The recognition that Mcl-1, a major component of the anti-apoptotic response, is intrinsically short-lived and must be continually resynthesized suggested a novel therapeutic approach. Pateamine A (PatA), a macrolide marine natural product, inhibits cap-dependent translation by binding to the initiation factor eIF4A. In this study, we demonstrated that a synthetic derivative of PatA, des-methyl des-amino PatA (DMDAPatA), blocked mRNA translation, reduced Mcl-1 protein and initiated apoptosis in CLL cells. This action was synergistic with the Bcl-2 antagonist ABT-199. However, avid binding to human plasma proteins limited DMDAPatA potency, precluding further development. To address this, we synthesized a new series of PatA analogs and identified three new leads with potent inhibition of translation. They exhibited less plasma protein binding and increased cytotoxic potency toward CLL cells than DMDAPatA, with greater selectivity towards CLL cells over normal lymphocytes. Computer modeling analysis correlated their structure-activity relationships and suggested that these compounds may act by stabilizing the closed conformation of eIF4A. Thus, these novel PatA analogs hold promise for application to cancers within the appropriate biological context, such as CLL.

Phase 1/2 study of DFP-10917 administered by continuous intravenous infusion in patients with recurrent or refractory acute myeloid leukemia.

BACKGROUND: DFP-10917, a deoxycytidine nucleoside analogue, has a unique mechanism of action resulting in leukemic cell death when administered for prolonged periods at low doses. The current phase 1/2 study investigated the safety, maximum tolerated dose, and evidence of antileukemic activity for DFP-10917 administered by 7-day or 14-day continuous intravenous infusion in patients with recurrent or refractory acute myeloid leukemia (AML). METHODS: In the phase 1 dose escalation portion of the study, patients were administered DFP-10917 by 7-day continuous intravenous infusion plus 21-day rest (stage 1) or 14-day continuous intravenous infusion plus 14-day rest (stage 2). The primary objectives of phase 1 were to determine the maximum tolerated dose, the phase 2 dose, and the dose-limiting toxicities (DLTs) of DFP-10917. The primary objectives of phase 2 were to evaluate the overall response rate of DFP-10917 using complete response (CR), CR without platelet recovery (CRp), CR with incomplete blood count recovery (CRi) or partial response. RESULTS: In stage 1 of phase 1 (4-35 mg/m2 /day as a 7-day continuous intravenous infusion), a DLT of grade 3 diarrhea occurred at a dose of 35 mg/m2 /day. In stage 2 of phase 1, a dose of 10 mg/m2 /day as a 14-day continuous intravenous infusion resulted in DLTs of prolonged hypocellularity, abdominal pain, diarrhea, and vomiting. The dose of 6 mg/m2 /day as a 14-day continuous intravenous infusion was found to be well tolerated and was selected for phase 2. Response rates in patients in phase 2 (N = 29) were 20.7% CR, 3.4% CRp, and 24.1% CRi. The overall response rate was 48.3% (95% confidence interval, 29.4%-67.5%). CONCLUSIONS: DFP-10917 as a 14-day continuous intravenous infusion at a dose of 6 mg/m2 /day can be administered safely and appears to be effective in patients with recurrent or refractory AML. A phase 3 investigation comparing DFP-10917 monotherapy versus standard of care in an early recurrent or refractory AML setting is warranted.

Comprehensive Ara-C SNP score predicts leukemic cell intracellular ara-CTP levels in pediatric acute myeloid leukemia patients.

AIM: Cytarabine (Ara-C), a mainstay of acute myeloid leukemia (AML) treatment, is a prodrug requiring activation to ara-CTP for its antileukemic activity. Aim of this study was to evaluate impact of genetic variants in the key genes involved in ara-C metabolism on the leukemic cell intracellular levels of ara-CTP. METHOD: We investigated SNPs in 14 ara-C metabolic-pathway genes, for association with intracellular ara-CTP levels, in leukemic cells obtained post-initiation of cytarabine infusion in pediatric AML patients (n = 68). RESULTS: Nine SNPs were significantly associated with leukemic cell intracellular concentration of ara-CTP. A comprehensive ara-CTP-SNP-score (ACSS) was further developed from top four SNPs identified in regression model. Patients were classified into three groups based on ACSS: high-ACSS (score >0), intermediate-ACSS (score = 0) and low-ACSS (score <0). ACSS designation was significant predictor of intracellular ara-CTP levels (p = 0.00012), suggesting a cumulative or synergistic effect of the significant SNPs. CONCLUSION: ACSS score designation holds promise in definfing ara-C dose. Validation of the clinical utility of ACSS score in other independent cohorts will help identification of patients with potentially lower or higher levels of the ara-CTP in leukemic cells, thereby opening up opportunities for dose management to reduce toxicity and enhance efficacy.

Targeting BRCA1/2 deficient ovarian cancer with CNDAC-based drug combinations.

PURPOSE: The mechanism of action of CNDAC (2'-C-cyano-2'-deoxy-1-ß-D-arabino-pentofuranosyl-cytosine) is unique among deoxycytidine analogs because upon incorporation into DNA it causes a single strand break which is converted to a double strand break after DNA replication. This lesion requires homologous recombination (HR) for repair. CNDAC, as the parent nucleoside, DFP10917, and as an oral prodrug, sapacitabine, are undergoing clinical trials for hematological malignancies and solid tumors. The purpose of this study is to investigate the potential of CNDAC for the therapy of ovarian cancer (OC). METHODS: Drug sensitivity was evaluated using a clonogenic survival assay. Drug combination effects were quantified by median effect analysis. RESULTS: OC cells lacking function of the key HR genes, BRCA1 or BRCA2, were more sensitive to CNDAC than corresponding HR proficient cells. The sensitization was associated with greater levels of DNA damage in response to CNDAC at clinically achievable concentrations, manifested as chromosomal aberrations. Three classes of CNDAC-based drug combinations were investigated. First, the PARP1 inhibitors, rucaparib and talazoparib, were selectively synergistic with CNDAC in BRCA1/2 deficient OC cells (combination index < 1) at a relatively low concentration range. Second, cisplatin and oxaliplatin had additive combination effects with CNDAC (combination index ~ 1). Finally, paclitaxel and docetaxel achieved additive cell-killing effects with CNDAC at concentration ranges of the taxanes similar for both BRCA1/2 deficient and proficient OC cells. CONCLUSIONS: This study provides mechanistic rationales for combining CNDAC with PARP inhibitors, platinum compounds and taxanes in ovarian cancer lacking BRCA1/2 function.

A phase I/II randomized trial of clofarabine or fludarabine added to idarubicin and cytarabine for adults with relapsed or refractory acute myeloid leukemia.

The purine nucleoside analogues clofarabine and fludarabine are active in acute myeloid leukemia (AML). We conducted a phase I/II randomized study of idarubicin and cytarabine with either clofarabine (CIA) or fludarabine (FIA) for relapsed or refractory AML. Clofarabine 15 mg/m2 was identified as the recommended phase II dose. Eighty-one patients were assigned using adaptive randomization to CIA (n = 48) or FIA (n = 33). The complete response (CR)/CR without platelet recovery rate did not differ between CIA and FIA (38% versus 30%, respectively; p = .50). In both arms, more than half of patients who had received only one prior line of therapy achieved remission. The median event-free survival for CIA and FIA was 2.0 and 1.9 months (p = .48), and the median overall survival was 6.3 and 4.7 months, respectively (p = .28). No significant differences in adverse events or early mortality rates were observed. Overall, CIA and FIA resulted in similar response rates and survival in patients with relapsed/refractory AML.

TDP1 is Critical for the Repair of DNA Breaks Induced by Sapacitabine, a Nucleoside also Targeting ATM- and BRCA-Deficient Tumors.

2'-C-cyano-2'-deoxy-1-ß-d-arabino-pentofuranosylcytosine (CNDAC) is the active metabolite of the anticancer drug, sapacitabine. CNDAC is incorporated into the genome during DNA replication and subsequently undergoes ß-elimination that generates single-strand breaks with abnormal 3'-ends. Because tyrosyl-DNA phosphodiesterase 1 (TDP1) selectively hydrolyzes nonphosphorylated 3'-blocking ends, we tested its role in the repair of CNDAC-induced DNA damage. We show that cells lacking TDP1 (avian TDP1-/- DT40 cells and human TDP1 KO TSCER2 and HCT116 cells) exhibit marked hypersensitivity to CNDAC. We also identified BRCA1, FANCD2, and PCNA in the DNA repair pathways to CNDAC. Comparing CNDAC with the chemically related arabinosyl nucleoside analog, cytosine arabinoside (cytarabine, AraC) and the topoisomerase I inhibitor camptothecin (CPT), which both generate 3'-end blocking DNA lesions that are also repaired by TDP1, we found that inactivation of BRCA2 renders cells hypersensitive to CNDAC and CPT but not to AraC. By contrast, cells lacking PARP1 were only hypersensitive to CPT but not to CNDAC or AraC. Examination of TDP1 expression in the cancer cell line databases (CCLE, GDSC, NCI-60) and human cancers (TCGA) revealed a broad range of expression of TDP1, which was correlated with PARP1 expression, TDP1 gene copy number and promoter methylation. Thus, this study identifies the importance of TDP1 as a novel determinant of response to CNDAC across various cancer types (especially non-small cell lung cancers), and demonstrates the differential involvement of BRCA2, PARP1, and TDP1 in the cellular responses to CNDAC, AraC, and CPT. Mol Cancer Ther; 16(11); 2543-51. ©2017 AACR.

A randomized phase 2 study of idarubicin and cytarabine with clofarabine or fludarabine in patients with newly diagnosed acute myeloid leukemia.

BACKGROUND: Fludarabine and clofarabine are purine nucleoside analogues with established clinical activity in patients with acute myeloid leukemia (AML). METHODS: Herein, the authors evaluated the efficacy and safety of idarubicin and cytarabine with either clofarabine (CIA) or fludarabine (FIA) in adults with newly diagnosed AML. Adults with newly diagnosed AML who were deemed suitable for intensive chemotherapy were randomized using a Bayesian adaptive design to receive CIA (106 patients) or FIA (76 patients). Patients received induction with idarubicin and cytarabine, plus either clofarabine or fludarabine. Responding patients could receive up to 6 cycles of consolidation therapy. Outcomes were compared with a historical cohort of patients who received idarubicin and cytarabine. RESULTS: The complete remission/complete remission without platelet recovery rate was similar among patients in the CIA and FIA arms (80% and 82%, respectively). The median event-free survival was 13 months and 12 months, respectively (P = .91), and the median overall survival was 24 months and not reached, respectively (P = .23), in the 2 treatment arms. CIA was associated with more adverse events, particularly transaminase elevation, hyperbilirubinemia, and rash. Early mortality was similar in the 2 arms (60-day mortality rate of 4% for CIA vs 1% for FIA; P = .32). In an exploratory analysis of patients aged <50 years, FIA was found to be associated with improved survival compared with idarubicin and cytarabine (2-year event-free survival rate: 58% vs 30% [P = .05] and 2-year overall survival rate: 72% vs 36% [P = .009]). CONCLUSIONS: CIA and FIA have similar efficacy in younger patients with newly diagnosed AML, although FIA is associated with a better toxicity profile. Cancer 2017;123:4430-9. © 2017 American Cancer Society.

Combining Anti-Mir-155 with Chemotherapy for the Treatment of Lung Cancers.

Purpose: The oncogenic miR-155 is upregulated in many human cancers, and its expression is increased in more aggressive and therapy-resistant tumors, but the molecular mechanisms underlying miR-155-induced therapy resistance are not fully understood. The main objectives of this study were to determine the role of miR-155 in resistance to chemotherapy and to evaluate anti-miR-155 treatment to chemosensitize tumors.Experimental Design: We performed in vitro studies on cell lines to investigate the role of miR-155 in therapy resistance. To assess the effects of miR-155 inhibition on chemoresistance, we used an in vivo orthotopic lung cancer model of athymic nude mice, which we treated with anti-miR-155 alone or in combination with chemotherapy. To analyze the association of miR-155 expression and the combination of miR-155 and TP53 expression with cancer survival, we studied 956 patients with lung cancer, chronic lymphocytic leukemia, and acute lymphoblastic leukemia.Results: We demonstrate that miR-155 induces resistance to multiple chemotherapeutic agents in vitro, and that downregulation of miR-155 successfully resensitizes tumors to chemotherapy in vivo We show that anti-miR-155-DOPC can be considered non-toxic in vivo We further demonstrate that miR-155 and TP53 are linked in a negative feedback mechanism and that a combination of high expression of miR-155 and low expression of TP53 is significantly associated with shorter survival in lung cancer.Conclusions: Our findings support the existence of an miR-155/TP53 feedback loop, which is involved in resistance to chemotherapy and which can be specifically targeted to overcome drug resistance, an important cause of cancer-related death. Clin Cancer Res; 23(11); 2891-904. ©2016 AACR.

Targeting BTK through microRNA in chronic lymphocytic leukemia.

Bruton's tyrosine kinase (BTK) is a critical mediator of survival in B-cell neoplasms. Although BTK inhibitors have transformed therapy in chronic lymphocytic leukemia (CLL), patients with high-risk genetics are at risk for relapse and have a poor prognosis. Identification of novel therapeutic strategies for this group of patients is an urgent unmet clinical need, and therapies that target BTK via alternative mechanisms may fill this niche. Herein, we identify a set of microRNAs (miRs) that target BTK in primary CLL cells and show that the histone deacetylase (HDAC) repressor complex is recruited to these miR promoters to silence their expression. Targeting the HDACs by using either RNA interference against HDAC1 in CLL or a small molecule inhibitor (HDACi) in CLL and mantle cell lymphoma restored the expression of the BTK-targeting miRs with loss of BTK protein and downstream signaling and consequent cell death. We have also made the novel and clinically relevant discovery that inhibition of HDAC induces the BTK-targeting miRs in ibrutinib-sensitive and resistant CLL to effectively reduce both wild-type and C481S-mutant BTK. This finding identifies a novel strategy that may be promising as a therapeutic modality to eliminate the C481S-mutant BTK clone that drives resistance to ibrutinib and provides the rationale for a combination strategy that includes ibrutinib to dually target BTK to suppress its prosurvival signaling.