Therapy-related acute promyelocytic leukemia (t-APL) is relatively rare, with limited data on outcome after treatment with arsenic trioxide (ATO) compared to standard intensive chemotherapy (CTX). We evaluated 103 adult t-APL patients undergoing treatment with all-trans retinoic acid (ATRA) alone (n=7) or in combination with ATO (n=24), CTX (n=53), or both (n=19). Complete remissions were achieved after induction therapy in 57% with ATRA, 100% with ATO/ATRA, 78% with CTX/ATRA, and 95% with CTX/ATO/ATRA. Early death rates were 43% for ATRA, 0% for ATO/ATRA, 12% for CTX/ATRA and 5% for CTX/ATO/ATRA. Three patients relapsed, two developed therapy-related acute myeloid leukemia and 13 died in remission including seven patients with recurrence of the prior malignancy. Median follow-up for survival was 3.7 years. None of the patients treated with ATRA alone survived beyond one year. Event-free survival was significantly higher after ATO-based therapy (95%, 95% CI, 82-99%) as compared to CTX/ATRA (78%, 95% CI, 64-87%; P=0.042), if deaths due to recurrence of the prior malignancy were censored. The estimated 2-year overall survival in intensively treated patients was 88% (95% CI, 80-93%) without difference according to treatment (P=0.47). ATO when added to ATRA or CTX/ATRA is feasible and leads to better outcomes as compared to CTX/ATRA in t-APL.

MLN4924 (pevonedistat), an inhibitor of the Nedd8 activating enzyme (NAE), has exhibited promising clinical activity in acute myelogenous leukemia (AML). Here we demonstrate that MLN4924 induces apoptosis in AML cell lines and clinical samples via a mechanism distinct from those observed in other malignancies. Inactivation of E3 cullin ring ligases (CRLs) through NAE inhibition causes accumulation of the CRL substrate c-Myc, which transactivates the PMAIP1 gene encoding Noxa, leading to increased Noxa protein, Bax and Bak activation, and subsequent apoptotic changes. Importantly, c-Myc knockdown diminishes Noxa induction; and Noxa siRNA diminishes MLN4924-induced killing. Because Noxa also neutralizes Mcl-1, an anti-apoptotic Bcl-2 paralog often upregulated in resistant AML, further experiments have examined the effect of combining MLN4924 with BH3 mimetics that target other anti-apoptotic proteins. In combination with ABT-199 or ABT-263 (navitoclax), MLN4924 exerts a synergistic cytotoxic effect. Collectively, these results provide new insight into MLN4924-induced engagement of the apoptotic machinery that could help guide further exploration of MLN4924 for AML.

Background.  Molecular profiles may provide insights into the likelihood of responding to traditional cytotoxic chemotherapy as well as important clues to the success of novel targeted agents.  The anti-apoptotic BCL-2 family proteins have previously been shown to facilitate pro-survival and resistance to chemotherapy in AML, multiple myeloma, as well as in other types of cancer. Measuring the function of these proteins using BH3 profiling has proven to provide useful information in predicting AML treatment response with traditional ara-c based treatment. Here, we sought to determine if such an approach might detect response with the addition of Alvocidib to ara-c-based chemotherapy. Mitochrondrial apoptosis signaling was assessed in AML patients treated with Alvocidib, ara-c and mitoxantrone (FLAM).  Methods.  Pretreatment peripheral blood mononuclear cell and bone marrow specimens from 63 patients treated with FLAM were measured for mitochondrial outer membrane permeabilization following incubation with BH3 peptides as a surrogate for BCL-2 protein family function. Results.  Analysis of the priming states (mitochondrial depolarization) in the patients who underwent complete remission (CR), compared with those who did not (NR), revealed that NOXA priming was significantly higher in CR bone marrow samples (median 44.5%) compared with NR samples (median 5.2%, p = 0.006). NOXA is known to interact most directly with MCL1, suggesting that these cancer cells may be MCL1 dependent. An additional multi-peptide algorithm using three BH3 members was also identified (involving BAD, PUMA, and BIM), which may also indirectly support MCL1 dependency. These BH3 priming profiles were both additive to known risk factors associated with clinical response to chemotherapy, including cytogenetic risk factors. Receiver operating characteristic (ROC) curve analysis of NOXA priming plus cytogenetics and MDS history indicated that these variables were highly predictive of response to FLAM (AUC-0.92, p = 0.0002). This correlation is distinct from our previous work which showed that the priming due to the BIM peptide predicts response to traditional ara-c based treatment. This work provides a basis for further studies into the MCL1 dependent action of Alvocidib, as well as a potential biomarker for identification of patients likely to respond to FLAM. Citation Format: Elisha J. Dettman, Steven L. Warner, Camille Doykan, Melissa Arn, Noel Blake, David J. Bearss, Michael Cardone, Bruce D. Smith. Mitochondrial profiling in AML patients treated with an Alvocidib containing regimen reveals MCL1 dependency in responder bone marrow. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3400. doi:10.1158/1538-7445.AM2015-3400

The ability to target myeloid leukemia with immunotherapy would represent a significant therapeutic advance. We report here immunological analysis of clinical trials of primary and secondary vaccination with K562/GM-CSF immunotherapy in adult chronic phase chronic myeloid leukemia patients (CML-CP) with suboptimal responses to imatinib mesylate. Using serological analysis of recombinant cDNA expression libraries of K562 with autologous vaccinated patient serum, we have identified 12 novel chronic myeloid leukemia-associated antigens (LAAs). We show that clinical responses following K562/GM-CSF vaccination are associated with induction of high-titer antibody responses to multiple LAAs. We observe markedly discordant patterns of baseline and induced antibody responses in these identically vaccinated patients. No single antigen was recognized in all responses to vaccination. We demonstrate that an additional 'booster' vaccination series can be given safely to those with inadequate responses to initial vaccination, and is associated with more frequent induction of IgG responses to antigens overexpressed in K562 vaccine compared with primary CML-CP. Finally, those with induced immune responses to the same LAAs often shared HLA subtypes and patients with clinical responses following vaccination recognized a partially shared but non-identical spectrum of antigens; both findings have potentially significant implications for cancer vaccine immunotherapy.

Acute myeloid leukemia (AML) remains the most common form of acute leukemia among adults and accounts for the largest number of annual deaths due to leukemias in the United States. The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for AML provide recommendations on the diagnostic evaluation and workup for AML, risk assessment based on cytogenetic and molecular features, treatment options for induction and consolidation therapies for younger and older (age ≥ 65 years) adult patients, and key supportive care considerations.

7065 Background: Sorafenib is a multikinase inhibitor with activity against B-raf, VEGF, and FLT3. Based on preclinical activity in FLT3 mutant AML, sorafenib was studied in refractory acute leukemia. Methods: The primary objective was to determine the safety and tolerability of sorafenib in refractory acute leukemias. Secondary objectives included pharmacokinetics (PK) and pharmacodynamic (PD) effects of sorafenib on FLT3 phosphorylation. Dose escalation began at 400 mg BIDx14days per month, and proceeded through 600 mg BID x 21 days per month. Plasma concentration of sorafenib and its primary metabolite sorafenib N-oxide were measured by LC/MS//MS method. The plasma inhibitory assay was used to measure target inhibition of phosphorylated FLT3 and phosphorylated Erk. Results: Fifteen patients (13 = AML, 2 = ALL) were enrolled (ages 37–85) and treated on three dosing schedules (400 mg BID x 14 d, 400 mg BID x 21 days, 600 mg BID x 21days) of single agent sorafenib. The maximally tolerated dose was 400 mg BID x 21 days per month. Grade 3 or greater toxicities were experienced in 55% of cycles, most common grade 3 or greater toxicities being fatigue (16%) and hypokalemia (13%). No patients met criteria for complete or partial response, but 11 of 15 (73%) patients experienced stable disease as best response, with 6 showing a reduction in bone marrow blasts after only one cycle, half of who experienced a >50% reduction in bone marrow blasts. Interestingly, 2 pts with FLT3-ITD mutations both showed marrow blast response (1 pt >50%). Sorafenib resulted in sustained complete inhibition of FLT3 and Erk as demonstrated in all patients assessed (n = 11). Importantly, this inhibition was maintained throughout treatment cycle and 3/5 pts had FLT3 inhibitory activity 7 days post their last dose. Correlative studies suggest sorafenib N-oxide is an active metabolite. Conclusions: Sorafenib is a potent inhibitor of FLT3 with favorable PK and PD properties. Clinical activity as a single agent was limited to transient reductions in bone marrow blast counts and dose escalation was limited due to toxicities. Based on PK data in conjunction with standard curves for inhibition of FLT3 by sorafenib in plasma, the minimum FLT3 inhibitory dose of sorafenib is likely less than 400 mg BID. No significant financial relationships to disclose.

Graft failure after allogeneic blood or marrow transplantation, although generally uncommon, can be a devastating complication. This report includes the outcome of nine patients who received a salvage transplant for failure to engraft after one (n=8) or 2 (n=1) prior transplants. Eight patients received allografts from the original donor. All received fludarabine 30 mg/m(2) i.v. and alemtuzumab 20 mg i.v. daily from days -6 to -2. Daily CYA was begun on day -2, and the allograft was infused on day 0. The therapy was well tolerated with low toxicity, and all nine patients engrafted, recovering neutrophils at a median of 12 days after transplant. Four patients died: two of relapse, one of a fungal infection in the setting of GVHD and one of multiple sclerosis. The combination of fludarabine and alemtuzumab is an effective and well-tolerated salvage conditioning regimen for patients who experience graft failure after blood or marrow transplants.

Despite extensive study in many malignancies, maintenance therapy has clinically benefited only two diseases: acute lymphocytic leukemia ( ALL) and acute promyelocytic leukemia ( APL). ALL maintenance therapy utilizes low- dose 6- mercaptopurine ( 6MP) and methotrexate ( MTX), while maintenance in APL primarily consists of all- trans- retinoic acid ( ATRA). 6MP and MTX as used in ALL are also now usually added to maintenance ATRA for APL, based on data suggesting an improved disease- free survival. Although the mechanism of action of MTX and 6MP as maintenance is unknown, low- dose cytotoxic agents are potent inducers of differentiation in vitro. Thus, we studied whether maintenance therapy in ALL, like ATRA in APL, may be inducing terminal differentiation of ALL progenitors. The APL cell line NB4, the ALL cell lines REH and RS4; 11, and patients' ALL blasts were incubated with ATRA, 6MP, and MTX in vitro. All three drugs inhibited the clonogenic growth of the APL and ALL cell lines without inducing immediate apoptosis, but associated with induction of phenotypic differentiation. The three drugs similarly upregulated lymphoid antigen expression, while decreasing CD34 expression, on patients' ALL blasts. These data suggest that induction of leukemia progenitor differentiation plays an important role in the mechanism of action of maintenance therapy in ALL.

Most cases of acute leukemia can be assigned to the myeloid, B or T lineage. In a few cases, definitive assignment cannot be achieved because blasts express antigens of more than one lineage. A subset of these, referred to as acute bilineal leukemias (aBLLs), is characterized by the presence of more than one population of blasts, each comprising a single lineage. We identified 19 cases of aBLL, including 10 mixed T and myeloid (T-My) and nine mixed B and myeloid (B-My); no mixed B and T cases were identified. Cytogenetic data were available for 16 patients. Three of seven patients with B-My had a t(9; 22)(q34q11.2), two had 11q23 translocations and one had del(9). Two of nine patients with T-My had 2p13 translocations; five had other unrelated abnormalities. Of 16 patients with outcome data, only six achieved complete remission and only two remain free of disease 2.5 and 4.5 years after chemotherapy or stem cell transplantation. aBLL is a rare disease that combines B or T and myeloid blasts. Cytogenetic abnormalities of t(9; 22) and 11q23 are common in, and may be restricted to, B-My cases, while T-My cases have frequent but generally non-recurring abnormalities. Both types of aBLL are associated with poor outcome.