Mary Riwes

FLT3 mutational status is an independent risk factor for adverse outcomes after allogeneic transplantation in AML.

Allogeneic hematopoietic cell transplantation (HCT) has been increasingly used in the setting of FMS-like tyrosine kinase-3 (FLT3)-mutated AML. However, its role in conferring durable relapse-free intervals remains in question. Herein we sought to investigate FLT3 mutational status on transplant outcomes. We conducted a retrospective cohort study of 262 consecutive AML patients who underwent first-time allogeneic HCT (2008–2014), of whom 171 had undergone FLT3-ITD (internal tandem duplication) mutational testing. FLT3-mutated AML was associated with nearly twice the relapse risk (RR) compared with those without FLT3 mutation 3 years post-HCT (63% vs 37%, P<0.001) and with a shorter median time to relapse (100 vs 121 days). FLT3 mutational status remained significantly associated with this outcome after controlling for patient, disease and transplant-related risk factors (P<0.05). Multivariate analysis showed a significant association of FLT3 mutation with increased 3-year RR (hazard ratio (HR) 3.63, 95% confidence interval (CI): 2.13, 6.19, P<0.001) and inferior disease-free survival (HR 2.05, 95% CI: 1.29, 3.27, P<0.01) and overall survival (HR 1.92, 95% CI: 1.14, 3.24, P<0.05). These data demonstrate high risk of early relapse after allogeneic HCT for FLT3-mutated AML that translates into adverse disease-free and overall survival outcomes. Additional targeted and coordinated interventions are needed to maintain durable remission after allogeneic HCT in this high-risk population.

Infectious Risk after Allogeneic Hematopoietic Cell Transplantation Complicated by Acute Graft-versus-Host Disease

The occurrence of infections after allogeneic hematopoietic stem cell transplantation (HCT) is nearly universal. However, the relationship between infections and graft-versus-host disease (GVHD) is complex and attribution of infectious-related mortality is highly inconsistent, making comparison of infectious complication rates across allogeneic HCT clinical studies difficult. We categorized infectious complications from diagnosis or 1 year before HCT (whichever occurred later) through 2 years after HCT according to timing, frequency, causative organism, severity, and contribution to mortality for 431 consecutive patients who underwent allogeneic HCT from 2008 to 2011. We then assessed the contribution of risk factors, such as the frequency of pre-HCT infections and post-HCT GVHD, on post-HCT infection frequency and severity. We found that each pre-HCT bacterial infection/year leads to an additional 2.15 post-HCT bacterial infection/year (P = .004). Pre-HCT viral and fungal infections were not predictors for post-HCT infections. Acute GVHD (aGVHD) significantly increased the risk of developing life-threatening (hazard ratio [HR], 1.97; 95% confidence interval [CI], 1.33 to 2.90) and fatal (HR, 2.8; 95% CI, 1.10 to 7.08) infections. Furthermore, patients who develop aGVHD experienced ~60% more infections than patients who never develop aGVHD. Quantification of infection frequency and severity for patients with and without GVHD may facilitate comparison of infectious outcomes across allogeneic HCT trials.

Vorinostat plus tacrolimus/methotrexate to prevent GVHD after myeloablative conditioning, unrelated donor HCT

The oral histone deacetylase (HDAC) inhibitor (vorinostat) is safe and results in low incidence of acute graft-versus-host disease (GVHD) after reduced-intensity conditioning, related donor hematopoietic cell transplantation (HCT). However, its safety and efficacy in preventing acute GVHD in settings of heightened clinical risk that use myeloablative conditioning, unrelated donor (URD), and methotrexate are not known. We conducted a prospective, phase 2 study in this higher-risk setting. We enrolled 37 patients to provide 80% power to detect a significant difference in grade 2 to 4 acute GVHD of 50% compared with a reduction in target to 28%. Eligibility included adults with a hematological malignancy to receive myeloablative HCT from an available 8/8-HLA matched URD. Patients received GVHD prophylaxis with tacrolimus and methotrexate. Vorinostat (100 mg twice daily) was started on day -10 and continued through day +100 post-HCT. Median age was 56 years (range, 18-69 years), and 95% had acute myelogenous leukemia or high-risk myelodysplastic syndrome. Vorinostat was safe and tolerable. The cumulative incidence of grade 2 to 4 acute GVHD at day 100 was 22%, and for grade 3 to 4 it was 8%. The cumulative incidence of chronic GVHD was 29%; relapse, nonrelapse mortality, GVHD-free relapse-free survival, and overall survival at 1 year were 19%, 16%, 47%, and 76%, respectively. Correlative analyses showed enhanced histone (H3) acetylation in peripheral blood mononuclear cells and reduced interleukin 6 (P = .028) and GVHD biomarkers (Reg3, P = .041; ST2, P = .002) at day 30 post-HCT in vorinostat-treated subjects compared with similarly treated patients who did not receive vorinostat. Vorinostat for GVHD prevention is an effective strategy that should be confirmed in a randomized phase 3 study. This trial was registered at www.clinicaltrials.gov as #NCT01790568.

Microbial metabolites and graft versus host disease

The health of mammals is a reflection of the diversity and composition of the intestinal microbiota. Alterations in the composition and functions of the intestinal microbiota have been implicated in multiple disease processes. The impact of the microbiota in health and disease is in part a function of the nutrient processing and release of metabolites. Recent studies have uncovered a major role for microbial metabolites in the function of the host immune system by which they influence disease processes such as acute graft versus host disease (GVHD), which is the main complication of allogeneic hematopoietic cell transplantation (allo‐HCT). The mechanisms of acute GVHD regulation by the complex microbial community and the metabolites released by them are unclear. In this review we summarize major findings of how microbial metabolites interact with the immune system and discuss how these interactions could impact acute GVHD.

Analytic morphomics: A novel CT imaging approach to quantify adipose tissue and muscle composition in allogeneic hematopoietic cell transplantation

Analytic morphomics is a novel methodology that uses high-throughput computed tomography (CT) processing techniques to generate reproducible body measurements (Supplementary Table).1, 2, 3, 4 Body mass index is widely used in clinical and public health studies to predict mortality risk.5 Indeed, we recently examined its impact in allogeneic hematopoietic cell transplantation (HCT) and found that obese patients were at significantly greater risk of mortality compared with normal weight individuals.6 Unfortunately, body mass index does not reliably distinguish adipose tissue mass from muscle mass.7 Therefore, we sought to index patient size using CT measurements.2 The aim of the current study was to apply analytic morphomics in a cohort of allogeneic HCT patients and correlate with clinical outcomes.

Murine Models of Steroid Refractory Graft-versus-Host Disease

Corticosteroids are the first line therapy for acute graft-versus-host disease (GVHD). However, the outcome of steroid refractory GVHD (SR-GVHD) is poor due to a lack of effective treatments. The development of therapies for SR-GVHD is limited by an incomplete understanding of its pathophysiology partly because of the absence of clinically relevant animal models of SR-GVHD. Here we addressed the need for a SR-GVHD animal model by developing both MHC matched multiple minor histocompatibility antigens (miHAs) mismatched and MHC mismatched haploidentical murine models of SR-GVHD. We demonstrate that animals can develop SR-GVHD regardless of whether steroids are initiated early or late post allogeneic bone marrow transplantation (allo-BMT). In general, we observed increased GVHD specific histopathological damage of target organs in SR-GVHD animals relative to steroid responsive animals. Interestingly, we found no significant differences in donor T cell characteristics between steroid refractory and responsive animals suggesting that donor T cell independent mechanisms may play more prominent roles in the pathogenesis of SR-GVHD than was considered previously.

Microbial metabolite sensor GPR43 controls severity of experimental GVHD

Microbiome-derived metabolites influence intestinal homeostasis and regulate graft-versus-host disease (GVHD), but the molecular mechanisms remain unknown. Here we show the metabolite sensor G-protein-coupled receptor 43 (GPR43) is important for attenuation of gastrointestinal GVHD in multiple clinically relevant murine models. GPR43 is critical for the protective effects of short-chain fatty acids (SCFAs), butyrate and propionate. Increased severity of GVHD in the absence of GPR43 is not due to baseline differences in the endogenous microbiota of the hosts. We confirm the ability of microbiome-derived metabolites to reduce GVHD by several methods, including co-housing, antibiotic treatment, and administration of exogenous SCFAs. The GVHD protective effect of SCFAs requires GPR43-mediated ERK phosphorylation and activation of the NLRP3 inflammasome in non-hematopoietic target tissues of the host. These data provide insight into mechanisms of microbial metabolite-mediated protection of target tissues from the damage caused allogeneic T cells.The microbial metabolite sensor GPR43 has been previously shown to be a crucial modulator of immune responses. Here the authors show GPR43 is required for controlling disease pathology severity in the context of experimental models of GVHD.

α1-Antitrypsin Infusion for treatment of Steroid Resistant Acute Graft-versus-Host Disease

Corticosteroid resistance after acute graft-versus-host disease (SR-aGVHD) results in high morbidity and mortality after allogeneic hematopoietic cell transplantation. Current immunosuppressive therapies for SR-aGVHD provide marginal effectiveness because of poor response or excessive toxicity, primarily from infection. α1-Antitrypsin (AAT), a naturally abundant serine protease inhibitor, is capable of suppressing experimental GVHD by downmodulating inflammation and increasing ratios of regulatory (Treg) to effector T cells (Teffs). In this prospective multicenter clinical study, we sought to determine the safety and response rate of AAT administration in SR-aGVHD. Forty patients with a median age of 59 years received intravenous AAT twice weekly for 4 weeks as first-line treatment of SR-aGVHD. The primary end point was overall response rate (ORR), the proportion of patients with SR-aGVHD in complete (CR) or partial response by day 28 without addition of further immunosuppression. Treatment was well tolerated without drug-related adverse events. A significant increase in serum levels of AAT was observed after treatment. The ORR and CR rates by day 28 were 65% and 35%, respectively, and included responses in all aGVHD target organs. At day 60, responses were sustained in 73% of patients without intervening immunosuppression. Infectious mortality was 10% at 6 months and 2.5% within 30 days of last AAT infusion. Consistent with preclinical data, correlative samples showed an increase in ratio of activated Tregs to Teffs after AAT treatment. These data suggest that AAT is safe and may be potentially efficacious in treating SR-aGVHD. This trial was registered at www.clinicaltrials.gov as #NCT01700036.

IAPs protect host target tissues from graft-versus-host disease in mice

Inhibitors of apoptosis proteins (IAPs) regulate apoptosis, but little is known about the role of IAPs in the regulation of immunity. Development of IAP inhibition by second mitochondria-derived activator of caspase (SMAC) mimetics is emerging as a novel therapeutic strategy to treat malignancies. We explored the role of IAPs in allogeneic immunity with 2 distinct yet complementary strategies, namely, chemical and genetic approaches, in clinically relevant models of experimental bone marrow transplantation (BMT). The small-molecule pan-IAP inhibitor SMAC mimetic AT-406 aggravated gastrointestinal graft-versus-host disease (GVHD) in multiple models. The role of specific IAPs in various host and donor cellular compartments was explored by utilizing X-linked IAP (XIAP)- and cellular IAP (cIAP)-deficient animals as donors or recipients. Donor T cells from C57BL/6 cIAP1-/- or XIAP-/- animals demonstrated equivalent GVHD severity and allogeneic responses, both in vivo and in vitro, when compared with B6 wild-type (B6-WT) T cells. By contrast, when used as recipient animals, both XIAP-/- and cIAP1-/- animals demonstrated increased mortality from GVHD when compared with B6-WT animals. BM chimera studies revealed that cIAP and XIAP deficiency in host nonhematopoietic target cells, but not in host hematopoietic-derived cells, is critical for exacerbation of GVHD. Intestinal epithelial cells from IAP-deficient animals showed reduced levels of antiapoptotic proteins as well as autophagy-related protein LC3 after allogeneic BMT. Collectively, our data highlight a novel immune cell-independent but target tissue-intrinsic role for IAPs in the regulation of gastrointestinal damage from GVHD.