Borthakur, Gautam

Abstract Background Systemic mastocytosis (SM) is characterized by abnormal proliferation and accumulation of neoplastic mast cells. Patients (pts) with SM are treated with recombinant interferon-alpha or cladribine. Responses to these agents are poor. Malignant mast cells in SM carry, in most cases, a mutation involving codon 816 of the c-KIT gene (D816V) resulting in constitutively activated c-kit receptor tyrosine kinase believed to be important for disease progression. Agents that antagonize this mutated form of c-kit may have clinical benefit in SM. Dasatinib is one such agent, proven effective in pre-clinical in vitro and in vivo models of SM. Study Design In pilot Phase II trial for SM, Dasatinib was administered at 70mg PO BID. Response was assessed after minimum of 3 months (3 cycles) of therapy. Therapy was discontinued in pts who showed no response after 6 cycles of therapy. Response was evaluated following guidelines proposed by Valent et al. (Leuk Res. 25;603–625, 2001). In addition, all symptoms related to SM were recorded and monitored. Results Thus far, a total of 30 pts have been treated; 24 are evaluable for response and toxicity, including 6 with aggressive SM (ASM), 4 with SM and associated hematologic non-mast cell disease (SM-AHNMD; 2 with chronic myelomonocytic leukemia and one each with myelofibrosis [SM-MF; JAK2 mutation positive and abnormal cytogenetics] and hypereosinophilic syndrome [SM-HES; FIP1L1-PDGFRa negative]) and 14 with indolent SM (ISM) with uncontrolled symptoms despite optimal supportive care measures. Median age is 57 years (range, 35–73); these were 10 males and 14 females; time from diagnosis to dasatinib therapy 49 months (range, 0–233), performance status 1 in 23 and 2 in 1 pt. Eleven patients were previously treated: imatinib mesylate in 6; denileukin diftitox in 4; and erythropoietin, interferon-alpha, or cladribine in 2 each. One pt, who had undergone splenectomy, had hepatomegaly prior to start of therapy. Median Hb 12.4g/dL (range, 8.5–15.4), WBC 6.7×109/L, (range, 3.5–53.3), and platelets 263×109/L (range, 60–377); no patient was transfusion dependent. Percent bone marrow mast cell varied from <10% in 9 pts, to 60% in 4 pts; blood tryptase level was ≤20ng/mL (not significant) in 7 pts and >200ng/mL (upper limit of the test) in 7 pts. A total of 94 cycles of therapy were administered. The median number of cycles was 4 (range, 1–8). Ten patients stopped therapy: 1 due to progression of AHNMD to acute leukemia, 1 lost a response (symptomatic improvement), 2 had no response after 3 months of therapy, and 6 due to toxicity. No grade 4 toxicity was observed. Twelve patients decreased the dose of dasatinib to 50mg PO BID, of which four to 40mg PO BID. Two patients (8%) achieved complete remission, one with SM-MF, and one with SM-HES. Both were c-KIT mutation negative and had low, not significant tryptase levels. Both were anemic (Hb 9.4g/dL) and failed erythropoietin therapy, and had abnormal WBC differential; one had low platelets (90×109/L). No significant response in % bone marrow mast cells (4 pts are too early in therapy) or blood tryptase levels have been observed in other patients so far. Symptoms related to SM improved significantly in 7 patients (29%). Conclusion Dasatinib is active in SM (overall response rate 37%). Updated clinical and molecular results will be presented.

Abstract 5-azacitidine (5-AZA) is standard of care in the first-line setting for higher-risk patients with Myelodysplastic Syndrome (MDS). However, 40-50% of patients are refractory to 5-AZA and most responders ultimately demonstrate disease progression within 2 years, often progressing to AML. For patients refractory to 5-AZA, 2-year survival probability is low (15%). Thus, there is a need for more effective initial and second-line therapies for patients with higher-risk MDS. The Inhibitors of Apoptosis (IAP) Proteins are a family of molecules that suppress apoptotic cell death. Expression of IAPs is dysregulated in MDS, suggesting a potential path for therapeutic intervention. SMAC (second mitochondrial activator of caspases) is an IAP antagonist, resulting in caspase activation, inhibition of NF-kB and increased apoptosis. Birinapant is a potent bivalent SMAC mimetic with improved tolerability and therapeutic index compared to other SMAC mimetics. This Phase Ib/2a study was designed primarily to determine the MTD and recommended Phase 2 dose and schedule of birinapant in combination with 5-AZA in patients with higher-risk MDS who are naïve or have relapsed or are refractory to 5-AZA. To date, 11 patients have been enrolled in the Phase 1b portion of the study, including 7 with IPSS classification high-risk MDS (5 male, 2 female; median age 75, range 64-82) and 4 with intermediate-risk MDS (2 male, 2 female; median age 72.5, range 65-84). All patients received standard 5-AZA, administered via either intravenous (IV) or subcutaneous (SC) routes, at 75 mg/m2 for 7 days of a 28-day cycle in combination with birinapant. Birinapant was administered IV twice weekly (Days 1 and 4) for either 3 of 4 weeks or 4 of 4 weeks per 28-day cycle at a dose of 13 mg/m2. No cycle 1 dose-limiting toxicities have been observed. Adverse events ≥ Grade 2 observed in two or more patients and judged to be related to treatment were rash/pruritis (Grade 2, 2 patients), thrombocytopenia (Grade 4, 2 patients) and neutropenia (Grade 4, 1 patient; Grade 3, 1 patient). Two SAEs, Grade 3 abdominal soft tissue necrosis with abdominal pain in the area of subcutaneous injections of 5-AZA, and Grade 3 cellulitis were judged to be related to treatment. These local injection site reactions/cellulitis were more severe than usually expected with SC 5-AZA, suggesting an on target pharmacodynamic (TNF mediated) localized synergistic effect in skin, but were not observed with IV administration. Both occurred after cycle 1 and were not considered DLTs. Data showing inhibition of NF-kB, a downstream pro-survival molecule activated by IAPs, in circulating blast cells from patients treated with birinapant at a dose of 13 mg/m2 twice weekly for 3 weeks out of 4, suggests that birinapant is pharmacologically active at this dosing schedule. Based on these and other pharmacodynamic data, despite not determining the formal MTD, the Phase 2 dosing regimen has been established as birinapant administered at 13 mg/m2 IV twice weekly for 3 weeks of a 28-day cycle in combination with 5-AZA at 75 mg/m2 by IV infusion for 7 days of a 28-day cycle. Although not a primary endpoint, evidence of clinical activity in 5-AZA resistant/refractory patients was observed in 2 of 11 patients to date, with an additional good clinical response in a 5-AZA naive high-risk MDS/CMML patient. One patient with prior 5-AZA-refractory MDS (cytogenetics: hypodiploid and +11q) showed bone marrow (BM) blast count reduction from 25% to 2% after 1 cycle of 5-AZA/birinapant treatment. Another patient with MDS (cytogenetics: +X; +19; +21) refractory to single-agent 5-AZA showed BM blast count reduction from 21% to 7% after 2 cycles. A third patient with treatment-naïve MDS/CMML-2 (cytogenetics: 46, XY, inv(6)(p11.2q15), t(6;21)(q21;q22) ) who had received prior hydroxyurea demonstrated BM blast count reduction from 17% to 2% after 3 cycles and underwent hematopoietic stem cell transplant. Several patients remain on study and are in active follow-up. This Phase 1b trial provide data for an acceptable safety profile of the first combination of a SMAC mimetic (birinapant) administered with IV 5-AZA. Early signs of clinical activity including in 5-AZA naïve and refractory patients were observed. These results provide rationale for a randomized Phase 2 study comparing birinapant in combination with 5-AZA against 5-AZA alone in the first-line setting for patients with higher-risk MDS. Disclosures Borthakur: Tetralogic Pharmaceuticals: Research Funding. Foran:TetraLogic Pharmaceuticals: Research Funding. Wang:Tetralogic Pharmaceuticals: Research Funding. Rakkar:Tetralogic Pharmaceuticals: Research Funding. Hager:Tetralogic Pharmaceuticals: Research Funding. Frey:Tetralogic Pharmaceuticals: Research Funding. Andreeff:TetraLogic Pharmaceuticals: Research Funding. Carter:Tetralogic Pharmaceuticals: Research Funding. Minderman:Tetralogic Pharmaceuticals: Research Funding. Russell:Tetralogic Pharmaceuticals: Employment. Tibes:Tetralogic Pharmaceuticals: Research Funding.

Abstract Abstract 677 Background: Activating mutations of NRAS and KRAS (‘RAS’) are found in 10–30% of myeloid malignancies. Evidence of constitutive activation of the RAS-RAF-MEK-ERK pathway, however, is more ubiquitous. Trametinib is a potent, selective, allosteric inhibitor of MEK1/2 that inhibits proliferation of myeloid cell lines in vitro. A Phase I/II study of single, daily, oral dosing of trametinib in myeloid malignancies is ongoing. Here we report the results from Phase I/II patients receiving the recommended Phase II dose (RP2D) of 2 mg. Methods: Patient eligibility was limited to patients with relapsed/refractory myeloid malignancies and adequate hepatic, renal and cardiac function. There were no hematologic eligibility criteria. Patients were prospectively screened for KRAS mutations at amino acids 12, 13 and for NRAS mutations at amino acids 12, 13 and 61. Clinical response was assessed using International Working Group (2003 and 2006) criteria for acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS), respectively. Pharmacodynamic marker (pERK) analysis was conducted in phase II patients with patient paired (pre/during treatment) blood and bone marrow samples. Results: Eighty-seven (9 in Phase I and 78 in Phase II) patients received 2 mg of trametinib daily: AML (n=66), MDS (n=11), chronic myelomonocytic leukemia (CMML) (n=7) or other (n=3) (RAS mutations, n=57; RAS wild type, n=15 and RAS unknown, n=15). Median age was 68 years (range 21–87) and for close to half of the patients, trametinib was 3 3rd line of therapy. Trametinib exhibited a long effective half-life with small peak/trough ratios, and the exposure profile maintained time above preclinical target threshold for the 24-hour dosing period. Results of the pharmacodynamic analysis indicated an on-target effect of trametinib. Responses by RAS mutation status for Phase I/II subjects are summarized in Table 1. Responding patients have continued therapy for median of 16.9 weeks (range, 10.9 – 36.7). Drug-related grade 3/4 adverse events (AEs) were encountered in 31/87 (36%) of the Phase I/II patients and there was one grade 5 drug-related AE,cerebrovascular accident. Hepatic toxicities (9%), gastrointestinal disorders (7%) and rash (5%) were the most frequent grade 3/4 AEs. AEs possibly related to inhibition of MEK signaling were blurred vision (total,13%; grade 3, 1%) and decreased cardiac ejection fraction (total, 9%; grade 3, 6%); events were generally reversible. Conclusion: At the RP2D of trametinib (2 mg orally daily), trametinib has shown promising clinical activity and responses (CR/CRp/Marrow CR/MLFS/PR) were almost exclusively seen in patients with refractory myeloid malignancies characterized by somatic RAS mutations. Expansion of the CMML cohort for RAS positive subjects is ongoing. Disclosures: Borthakur: GlaxoSmithKline, Sigma-Tau, Eisai, XBiotech: Research Funding. Off Label Use: Trametinib, to report outcome of clinicla trial to audience at ASH meeting. Foran:GlaxoSmithKline: Research Funding. Platzbecker:GlaxoSmithKline: Honoraria, Research Funding. Giagounidis:GlaxoSmithKline: Honoraria. Ottmann:GlaxoSmithKline: Clinical trial participation Other. Kadia:GlaxoSmithKline: Research Funding. Bauman:GlaxoSmithKline: Employment, Equity Ownership. Wu:GlaxoSmithKline: Employment. Liu:GlaxoSmithKline: Employment. Schramek:GlaxoSmithKline: Employment. Zhu:GlaxoSmithKline: Employment. Wissel:GlaxoSmithKline: Employment, Equity Ownership.

AbstractBackgroundAlthough the prognosis of core‐binding factor (CBF) acute myeloid leukemia (AML) is better than other subtypes of AML, 30% of patients still relapse and may require allogeneic hematopoietic cell transplantation (alloHCT). However, there is no validated widely accepted scoring system to predict patient subsets with higher risk of relapse.MethodsEleven centers in the US and Europe evaluated 247 patients with t(8;21)(q22;q22).ResultsComplete remission (CR) rate was high (92.7%), yet relapse occurred in 27.1% of patients. A total of 24.7% of patients received alloHCT. The median disease‐free (DFS) and overall (OS) survival were 20.8 and 31.2 months, respectively. Age, KIT D816V mutated (11.3%) or nontested (36.4%) compared with KIT D816V wild type (52.5%), high white blood cell counts (WBC), and pseudodiploidy compared with hyper‐ or hypodiploidy were included in a scoring system (named I‐CBFit). DFS rate at 2 years was 76% for patients with a low‐risk I‐CBFit score compared with 36% for those with a high‐risk I‐CBFit score (P < 0.0001). Low‐ vs high‐risk OS at 2 years was 89% vs 51% (P < 0.0001).ConclusionsI‐CBFit composed of readily available risk factors can be useful to tailor the therapy of patients, especially for whom alloHCT is not need in CR1 (ie, patients with a low‐risk I‐CBFit score).

BACKGROUNDRAS/RAF/mitogen‐activated protein kinase activation is common in myeloid malignancies. Trametinib, a mitogen‐activated protein kinase kinase 1 (MEK1)/MEK2 inhibitor with activity against multiple myeloid cell lines at low nanomolar concentrations, was evaluated for safety and clinical activity in patients with relapsed/refractory leukemias.METHODSThis phase 1/2 study accrued patients with any relapsed/refractory leukemia in phase 1. In phase 2, this study accrued patients with relapsed/refractory acute myeloid leukemia (AML) or high‐risk myelodysplastic syndromes (MDS) with NRAS or KRAS mutations (cohort 1); patients with AML, MDS, or chronic myelomonocytic leukemia (CMML) with a RAS wild‐type mutation or an unknown mutation status (cohort 2); and patients with CMML with an NRAS or KRAS mutation (cohorts 3).RESULTSThe most commonly reported treatment‐related adverse events were diarrhea, rash, nausea, and increased alanine aminotransferase levels. The phase 2 recommended dose for Trametinib was 2 mg orally daily. The overall response rates were 20%, 3%, and 27% for cohorts 1, 2, and 3, respectively, and this indicated preferential activity among RAS‐mutated myeloid malignancies. Repeated cycles of trametinib were well tolerated with manageable or reversible toxicities; these results were similar to those of other trametinib studies.CONCLUSIONSThe selective, single‐agent activity of trametinib against RAS‐mutated myeloid malignancies validates its therapeutic potential. Combination strategies based on a better understanding of the hierarchical role of mutations and signaling in myeloid malignancies are likely to improve the response rate and duration. Cancer 2016;122:1871–9. © 2016 American Cancer Society.

RAS is an oncogene frequently mutated in human cancer. RAS mutations have been reported in 10–15% of cases of acute myeloid leukemia (AML) but they appear to be less frequent among patients with myelodysplastic syndrome (MDS). The impact of RAS mutations in patients with MDS is unclear. We conducted a retrospective study in 1,067 patients with newly diagnosed MDS for whom RAS mutational analysis was available. Overall, 4% of patients carried mutant RAS alleles. Notably, FLT3 mutations, which were found in 2% of patients, were mutually exclusive with RAS mutations. Patients with RAS mutations had a higher white blood cell count as well as bone marrow blasts compared with patients carrying wild‐type RAS. However, no differences were observed between both groups regarding the risk of AML transformation (9% vs. 7%) and overall survival (395 days vs. 500 days, P = 0.057). In summary, RAS mutations are infrequent in patients with MDS and do not appear to negatively impact their outcome. Am. J. Hematol. 88:365–369, 2013. © 2013 Wiley Periodicals, Inc.