Despite major improvements in allogeneic hematopoietic cell transplantation over the last decades, corticosteroid-refractory (SR) acute (a) and chronic (c) graft-versus-host disease (GVHD) cause high mortality. Pre-clinical evidence indicates the potent anti-inflammatory properties of the JAK1/2 inhibitor ruxolitinib. In this retrospective survey, 19 stem cell transplant centers in Europe and the United States reported outcome data from 95 patients who had received ruxolitinib as salvage-therapy for SR-GVHD. Patients were classified as having SR-aGVHD (n=54, all grade III or IV) or SR-cGVHD (n=41, all moderate or severe). The median number of previous GVHD-therapies was 3 for both SR-aGVHD (1–7) and SR-cGVHD (1–10). The ORR was 81.5% (44/54) in SR-aGVHD including 25 CRs (46.3%), while for SR-cGVHD the ORR was 85.4% (35/41). Of those patients responding to ruxolitinib, the rate of GVHD-relapse was 6.8% (3/44) and 5.7% (2/35) for SR-aGVHD and SR-cGVHD, respectively. The 6-month-survival was 79% (67.3%–90.7%,95% CI) and 97.4% (92.3%–100%,95% CI) for SR-aGVHD and SR-cGVHD, respectively. Cytopenia and CMV-reactivation were observed during ruxolitinib-treatment in both SR-aGVHD (30/54, 55.6% and 18/54, 33.3%) and SR-cGVHD (7/41, 17.1% and 6/41, 14.6%) patients. Ruxolitinib may constitute a promising new treatment option for SR-aGVHD and SR-cGVHD that should be validated in a prospective trial.

PURPOSE Despite undergoing allogeneic hematopoietic stem cell transplantation (HCT), patients with acute myeloid leukemia (AML) with internal tandem duplication mutation in the FMS-like tyrosine kinase 3 gene ( FLT3-ITD) have a poor prognosis, frequently relapse, and die as a result of AML. It is currently unknown whether a maintenance therapy using FLT3 inhibitors, such as the multitargeted tyrosine kinase inhibitor sorafenib, improves outcome after HCT. PATIENTS AND METHODS In a randomized, placebo-controlled, double-blind phase II trial (SORMAIN; German Clinical Trials Register: DRKS00000591), 83 adult patients with FLT3-ITD–positive AML in complete hematologic remission after HCT were randomly assigned to receive for 24 months either the multitargeted and FLT3-kinase inhibitor sorafenib (n = 43) or placebo (n = 40 placebo). Relapse-free survival (RFS) was the primary endpoint of this trial. Relapse was defined as relapse or death, whatever occurred first. RESULTS With a median follow-up of 41.8 months, the hazard ratio (HR) for relapse or death in the sorafenib group versus placebo group was 0.39 (95% CI, 0.18 to 0.85; log-rank P = .013). The 24-month RFS probability was 53.3% (95% CI, 0.36 to 0.68) with placebo versus 85.0% (95% CI, 0.70 to 0.93) with sorafenib (HR, 0.256; 95% CI, 0.10 to 0.65; log-rank P = .002). Exploratory data show that patients with undetectable minimal residual disease (MRD) before HCT and those with detectable MRD after HCT derive the strongest benefit from sorafenib. CONCLUSION Sorafenib maintenance therapy reduces the risk of relapse and death after HCT for FLT3-ITD–positive AML.

Preliminary evidence suggests that the multikinase inhibitor sorafenib has clinical activity in FLT3-ITD-positive (FLT3-ITD) acute myeloid leukemia (AML). However, the quality and sustainability of achievable remissions and clinical variables that influence the outcome of sorafenib monotherapy are largely undefined. To address these questions, we evaluated sorafenib monotherapy in 65 FLT3-ITD AML patients treated at 23 centers. All but two patients had relapsed or were chemotherapy-refractory after a median of three prior chemotherapy cycles. Twenty-nine patients (45%) had undergone prior allogeneic stem cell transplantation (allo-SCT). The documented best responses were: hematological remission in 24 patients (37%), bone marrow remission in 5 patients (8%), complete remission (with and without normalization of peripheral blood counts) in 15 patients (23%) and molecular remission with undetectable FLT3-ITD mRNA in 10 patients (15%), respectively. Seventeen of the patients without prior allo-SCT (47%) developed sorafenib resistance after a median treatment duration of 136 days (range, 56-270 days). In contrast, allo-SCT patients developed sorafenib resistance less frequently (38%) and significantly later (197 days, range 38-225 days; P ¼ 0.03). Sustained remissions were seen exclusively in the allo-SCT cohort. Thus, sorafenib monotherapy has significant activity in FLT3-ITD AML and may synergize with allogeneic immune effects to induce durable remissions.

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Individuals with acute myeloid leukemia (AML) harboring an internal tandem duplication (ITD) in the gene encoding Fms-related tyrosine kinase 3 (FLT3) who relapse after allogeneic hematopoietic cell transplantation (allo-HCT) have a 1-year survival rate below 20%. We observed that sorafenib, a multitargeted tyrosine kinase inhibitor, increased IL-15 production by FLT3-ITD leukemia cells. This synergized with the allogeneic CD8 T cell response, leading to long-term survival in six mouse models of FLT3-ITD AML. Sorafenib-related IL-15 production caused an increase in CD8CD107aIFN-γ T cells with features of longevity (high levels of Bcl-2 and reduced PD-1 levels), which eradicated leukemia in secondary recipients. Mechanistically, sorafenib reduced expression of the transcription factor ATF4, thereby blocking negative regulation of interferon regulatory factor 7 (IRF7) activation, which enhanced IL-15 transcription. Both IRF7 knockdown and ATF4 overexpression in leukemia cells antagonized sorafenib-induced IL-15 production in vitro. Human FLT3-ITD AML cells obtained from sorafenib responders following sorafenib therapy showed increased levels of IL-15, phosphorylated IRF7, and a transcriptionally active IRF7 chromatin state. The mitochondrial spare respiratory capacity and glycolytic capacity of CD8 T cells increased upon sorafenib treatment in sorafenib responders but not in nonresponders. Our findings indicate that the synergism of T cells and sorafenib is mediated via reduced ATF4 expression, causing activation of the IRF7-IL-15 axis in leukemia cells and thereby leading to metabolic reprogramming of leukemia-reactive T cells in humans. Therefore, sorafenib treatment has the potential to contribute to an immune-mediated cure of FLT3-ITD-mutant AML relapse, an otherwise fatal complication after allo-HCT.

Introduction: Most patients with FLT3-ITD-positive AML, who relapse after allogenic stem cell transplantation (allo-SCT) die from their disease. Whether prophylactic FLT3-ITD inhibition with sorafenib can prevent AML relapse and improve outcome of patients in complete hematological remission (CHR) after allo-SCT is unknown and was tested in the SORMAIN trial. Methods: This randomized, double blind, placebo-controlled study was done at 14 centers in Germany and Austria. Patients with FLT3-ITD+ AML, aged 18 years or older, who had undergone allogenic stem cell transplantation from a HLA-matched sibling donor, 10/10 or 9/10 HLA-matched unrelated donor, and who were in confirmed CHR at the time of screening between day +30 and day +100 post allo-SCT, were included. Patients were randomly assigned (1:1) to receive either sorafenib (starting dose: 2 x 1 tbl. [2 x 200mg] qd, increasing every 14d to up to 2 x 2 tbl. [2 x 400mg] qd according to tolerability) or placebo (2 x 1 or 2 tbl. qd) for up to 24 months. Randomization was done centrally. In case of drug related adverse events, study medication could be interrupted, stepwise reduced to a minimum of 2 x 1 tbl. qd, temporarily withheld and recommenced at a lower dose level. FLT3-ITD diagnostics was done centrally at baseline and at time of relapse. In relapsing patients, off-label compassionate use of sorafenib was possible. The primary endpoint was relapse-free survival (RFS) as defined by either hematological relapse or death from any cause. The secondary endpoint was overall survival (OS). We here report the final RFS analysis. The OS results will be unblinded only prior to the ASH meeting and will be reported there. The SORMAIN study was terminated prior to full recruitment because of slow accrual. SORMAIN was registered with the European Clinical Trials Database (EudraCT 2010-018539-16) and the German Clinical Trials Register (DRKS00000591). Results: Between October 29, 2010, and May 17, 2016, 83 patients (41 males, 42 females) were randomized and included in the primary analysis (placebo, n=40; sorafenib, n=43). Median age was 54 years (IQR 47.75 - 61.33) for the entire study population and not significantly different between sorafenib and placebo groups. With a median follow up of 41.8 months after randomization (IQR 24.1 - 42.5), median RFS was 30.9 months (lower bound of 95% CI 5.2 months) in the placebo group versus not reached in the sorafenib group, corresponding to a 2-year RFS of 53,3 % (95% CI 36.5-67.5) in the placebo versus 85.0 % (69.5-93.0) in the sorafenib group (hazard ratio [HR] 0.39, 95% CI; 0.18 -0.85; P=0.0135) (Fig. 1). Overall, sorafenib was well tolerated. The most common grade 3-4 adverse event in both groups was acute GvHD (seven [ 17.5%] in the placebo group vs. nine [20.9%] in the sorafenib group. Conclusion: Sorafenib maintenance therapy after allo-SCT is feasible and significantly reduces the risk of relapse or death in patients with FLT3-ITD positive AML. OS results will be presented at the meeting. Figure 1. Figure 1. Disclosures Burchert: Bristol Myers Squibb: Honoraria, Research Funding; Bayer: Research Funding; Pfizer: Honoraria; AOP Orphan: Honoraria, Research Funding; Novartis: Research Funding. Bug:Amgen: Honoraria; Neovii: Other: Travel Grant; Novartis Pharma: Honoraria, Research Funding; Astellas Pharma: Other: Travel Grant; Jazz Pharmaceuticals: Other: Travel Grant; Celgene: Honoraria; Janssen: Other: Travel Grant. Finke:Riemser: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Other: travel grants, Research Funding; Neovii: Consultancy, Honoraria, Other: travel grants, Research Funding; Medac: Consultancy, Honoraria, Other: travel grants, Research Funding. Stelljes:Pfizer: Consultancy, Honoraria, Research Funding; MSD: Consultancy; JAZZ: Honoraria; Amgen: Honoraria; Novartis: Honoraria. Rollig:Bayer: Research Funding; Janssen: Research Funding. Wäsch:Pfizer: Honoraria. Lang:Novartis: Membership on an entity's Board of Directors or advisory committees, Other: Travel, Research Funding. Ehninger:Cellex Gesellschaft fuer Zellgewinnung mbH: Employment, Equity Ownership; GEMoaB Monoclonals GmbH: Employment, Equity Ownership; Bayer: Research Funding. Serve:Bayer: Research Funding. Kroeger:Neovii: Honoraria, Research Funding; JAZZ: Honoraria; Sanofi: Honoraria; Celgene: Honoraria, Research Funding; Riemser: Honoraria, Research Funding; Novartis: Honoraria, Research Funding. Götze:JAZZ Pharmaceuticals: Honoraria; Novartis: Honoraria; Takeda: Honoraria, Other: Travel aid ASH 2017; Celgene: Honoraria, Research Funding. Schmid:Jazz Pharma: Honoraria, Other: Travel grant, Speakers Bureau. Wolf:BMS: Honoraria, Research Funding; Pfizer: Honoraria; Novartis: Honoraria, Research Funding; AOP Orphan: Honoraria, Research Funding. Thiede:AgenDix: Other: Ownership; Novartis: Honoraria, Research Funding. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Bethge:Miltenyi Biotec GmbH: Consultancy, Honoraria, Research Funding; Neovii GmbH: Honoraria, Research Funding.

It is unknown, why only a minority of chronic myeloid leukemia (CML) patients sustains treatment free remission (TFR) after discontinuation of tyrosine kinase inhibitor (TKI) therapy in deep molecular remission (MR). Here we studied, whether expression of the T-cell inhibitory receptor (CTLA-4)-ligand CD86 (B7.2) on plasmacytoid dendritic cells (pDC) affects relapse risk after TKI cessation. CML patients in MR displayed significantly higher CD86pDC frequencies than normal donors (P<0.0024), whereas TFR patients had consistently low CD86pDC (n=12). This suggested that low CD86pDC might be predictive of TFR. Indeed, in a prospective analysis of 122 patients discontinuing their TKI within the EURO-SKI trial, the one-year relapse-free survival (RFS) was 30.1% (95% CI 15.6-47.9) for patients with >95 CD86pDC per 10 lymphocytes, but 70.0% (95% CI 59.3-78.3) for patients with <95 CD86pDC (hazard ratio (HR) 3.4, 95%CI: 1.9-6.0; P<0.0001). Moreover, only patients with <95 CD86pDC derived a significant benefit from longer (>8 years) TKI exposure before discontinuation (HR 0.3, 95% CI 0.1-0.8; P=0.0263). High CD86pDC counts significantly correlated with leukemia-specific CD8 Tcell exhaustion (Spearman correlation: 0.74, 95%-CI: 0.21-0.92; P=0.0098). Our data demonstrate that CML patients with high CD86pDC counts have a higher risk of relapse after TKI discontinuation.

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