Molecular profile of FLT3-mutated relapsed/refractory patients with AML in the phase 3 ADMIRAL study of gilteritinib.

The phase 3 Study of ASP2215 Versus Salvage Chemotherapy in Patients With Relapsed or Refractory Acute Myeloid Leukemia (AML) With FMS-like Tyrosine Kinase (FLT3) Mutation (ADMIRAL) trial demonstrated the superiority of the FLT3 inhibitor, gilteritinib, to salvage chemotherapy (SC) in patients with FLT3-mutated relapsed or refractory (R/R) AML. Baseline comutations, FLT3-internal tandem duplication (ITD) allelic ratio and length, and treatment-emergent mutations were analyzed in patients in the ADMIRAL trial. Baseline comutations were grouped according to gene subgroups (DNA methylation/hydroxymethylation, transcription, chromatin-spliceosome, receptor tyrosine kinase-Ras signaling, TP53-aneuploidy, NPM1, DNMT3A, DNMT3A/NPM1, WT-1, and IDH1/IDH2). Across all but 1 gene subgroup (TP53-aneuploidy), higher pretransplant response rates and a trend toward longer overall survival were observed with gilteritinib vs SC. Patients with DNMT3A/NPM1 comutations who received gilteritinib had the most favorable outcomes of any molecular subgroup analyzed. Survival outcomes with gilteritinib were not adversely affected by FLT3-ITD allelic ratio, FLT3-ITD length, or multiple FLT3-ITD mutations. Among patients who relapsed on gilteritinib, Ras/mitogen-activated protein kinase (MAPK) pathway and FLT3 F691L gene mutations were the most common mutational events associated with treatment resistance. However, the occurrence of Ras/MAPK pathway gene mutations at baseline did not preclude a clinical benefit from gilteritinib. Acquisition of multiple Ras/MAPK pathway gene mutations at relapse suggests a high level of pathway reactivation is needed to overcome the gilteritinib treatment effect. These findings provide insight into the R/R AML molecular profile and the impact of FLT3 inhibitors on mutational evolution associated with treatment resistance and benefit of gilteritinib across a wide spectrum of molecular and genetic subgroups in FLT3-mutated R/R AML. This trial was registered at www.clinicaltrials.gov as #NCT02421939.

Safety and Antitumor Activity of Repeated ASP3026 Administration in Japanese Patients with Solid Tumors: A Phase I Study.

BACKGROUND AND OBJECTIVE: Anaplastic lymphoma kinase gene rearrangements (ALKr) resulting in EML4-ALK proteins occur in a subset of solid tumors and are targeted by ALK inhibitors. Given the development of drug resistance to ALK inhibitors, ALK inhibitors with different kinase selectivity are required. METHODS: This phase I, non-randomized, open-label study evaluated the dose-limiting toxicity (DLT), safety, pharmacokinetics, and antitumor activity of ASP3026, a second-generation ALK inhibitor, in Japanese patients with solid tumors. Between 1 June 2011 and 20 January 2014, 29 patients received different daily doses of ASP3026 in the escalation (25 mg, n = 3; 50 mg, n = 3; 75 mg, n = 3; 125 mg, n = 4; 200 mg, n = 3; or 325 mg, n = 7) and expansion (200 mg, n = 6) cohorts. RESULTS: Three patients had DLTs at the 325-mg dose: cataract exacerbation, increased aspartate transaminase and alanine transaminase, and impaired hepatic function (all Grade 3 severity). Thus, the maximum tolerated dose was 200 mg. The treatment-emergent adverse event incidence was 100%; the most common events were nausea (n = 8, 27.6%), decreased appetite (n = 10, 34.5%), and fatigue (n = 9, 31.0%) of mild or moderate severity. Six patients were positive for ALK protein and three had ALKr. Two patients achieved partial responses: one with Ewing sarcoma (75-mg dose group) and one with an ALKr-positive inflammatory myofibroblastic tumor (125-mg dose group). CONCLUSION: ASP3026 at a 200-mg dose may provide therapeutic benefit for patients with solid tumors, with a tolerable safety profile. CLINICAL TRIAL REGISTRATION: This study is registered at ClinicalTrials.gov under the identifier NCT01401504 on July 25, 2011.

The impact of FLT3 mutation clearance and treatment response after gilteritinib therapy on overall survival in patients with FLT3 mutation-positive relapsed/refractory acute myeloid leukemia.

The FLT3 inhibitor gilteritinib has clinical activity in patients with FLT3-mutated (FLT3mut+ ) relapsed/refractory (R/R) acute myeloid leukemia (AML). The impact of FLT3 mutation clearance and the achievement of composite complete remission (CRc) and complete remission/complete remission with partial hematologic recovery (CR/CRh) on overall survival (OS) in patients with FLT3mut+ R/R AML treated with single-agent gilteritinib in a phase 1/2 trial were evaluated. Using next-generation sequencing, a FLT3-ITD variant allele frequency of ≤10-4 was used to define FLT3-ITD clearance in patients with no morphologic leukemia (ie, CRc). A total of 108 patients with FLT3-ITD-positive (FLT3-ITD+) R/R AML were analyzed; 95 of these patients had received ≥80-mg/day gilteritinib. Ten of the 95 patients had FLT3-ITD clearance; eight of these 10 patients achieved CRc and were considered negative for measurable residual disease. There was a trend toward longer OS in patients who attained CRc with FLT3-ITD clearance (131.4 weeks) versus those who achieved CRc and did not have FLT3-ITD clearance (n = 41; 43.3 weeks; HR = 0.416; p = 0.066). Among patients treated with ≥80-mg/day gilteritinib who achieved CR/CRh (n = 24), seven had FLT3-ITD clearance. Among patients who received 120-mg/day gilteritinib, those who achieved CR/CRh had a longer median OS (70.6 weeks) and higher 52-week survival probability (66.7%) than patients who did not achieve CR/CRh (n = 71; median OS, 41.7 weeks; 52-week survival probability, 20.2%). Overall, these data suggest that gilteritinib can induce deep molecular responses in patients with FLT3-ITD+ R/R AML, and in the setting of CRc or CR/CRh, these responses may be associated with prolonged survival.

Pharmacokinetic Profile of Gilteritinib: A Novel FLT-3 Tyrosine Kinase Inhibitor.

BACKGROUND AND OBJECTIVE: Gilteritinib is a novel, highly selective tyrosine kinase inhibitor approved in the USA, Canada, Europe, Brazil, Korea, and Japan for the treatment of FLT3 mutation-positive acute myeloid leukemia. This article describes the clinical pharmacokinetic profile of gilteritinib. METHODS: The pharmacokinetic profile of gilteritinib was assessed from five clinical studies. RESULTS: Dose-proportional pharmacokinetics was observed following once-daily gilteritinib administration (dose range 20-450 mg). Median maximum concentration was reached 2-6 h following single and repeat dosing of gilteritinib; mean elimination half-life was 113 h. Elimination was primarily via feces. Exposure to gilteritinib was comparable under fasted and fed conditions. Gilteritinib is primarily metabolized via cytochrome P450 (CYP) 3A4; coadministration of gilteritinib with itraconazole (a strong P-glycoprotein inhibitor and CYP3A4 inhibitor) or rifampicin (a strong P-glycoprotein inducer and CYP3A inducer) significantly affected the gilteritinib pharmacokinetic profile. No clinically relevant interactions were observed when gilteritinib was coadministered with midazolam (a CYP3A4 substrate) or cephalexin (a multidrug and toxin extrusion 1 substrate). Unbound gilteritinib exposure was similar between subjects with hepatic impairment and normal hepatic function. CONCLUSIONS: Gilteritinib exhibits a dose-proportional pharmacokinetic profile in healthy subjects and in patients with relapsed/refractory acute myeloid leukemia. Gilteritinib exposure is not significantly affected by food. Moderate-to-strong CYP3A inhibitors demonstrated a significant effect on gilteritinib exposure. Coadministration of gilteritinib with CYP3A4 or multidrug and toxin extrusion 1 substrates did not impact substrate concentrations. Unbound gilteritinib was comparable between subjects with hepatic impairment and normal hepatic function; dose adjustment is not warranted for patients with hepatic impairment. CLINICAL TRIAL REGISTRATION: NCT02014558, NCT02456883, NCT02571816.

Gilteritinib is a clinically active FLT3 inhibitor with broad activity against FLT3 kinase domain mutations.

Gilteritinib is the first FMS-like tyrosine kinase 3 (FLT3) tyrosine kinase inhibitor (TKI) approved as monotherapy in acute myeloid leukemia with FLT3 internal tandem duplication and D835/I836 tyrosine kinase domain (TKD) mutations. Sequencing studies in patients have uncovered less common, noncanonical (NC) mutations in FLT3 and have implicated secondary TKD mutations in FLT3 TKI resistance. We report that gilteritinib is active against FLT3 NC and TKI resistance-causing mutations in vitro. A mutagenesis screen identified FLT3 F691L, Y693C/N, and G697S as mutations that confer moderate resistance to gilteritinib in vitro. Analysis of patients treated with gilteritinib revealed that 2/9 patients with preexisting NC FLT3 mutations responded and that secondary TKD mutations are acquired in a minority (5/31) of patients treated with gilteritinib. Four of 5 patients developed F691L mutations (all treated at <200 mg). These studies suggest that gilteritinib has broad activity against FLT3 mutations and limited vulnerability to resistance-causing FLT3 TKD mutations, particularly when used at higher doses.

Gilteritinib or Chemotherapy for Relapsed or Refractory FLT3-Mutated AML.

BACKGROUND: Patients with relapsed or refractory acute myeloid leukemia (AML) with mutations in the FMS-like tyrosine kinase 3 gene (FLT3) infrequently have a response to salvage chemotherapy. Gilteritinib is an oral, potent, selective FLT3 inhibitor with single-agent activity in relapsed or refractory FLT3-mutated AML. METHODS: In a phase 3 trial, we randomly assigned adults with relapsed or refractory FLT3-mutated AML in a 2:1 ratio to receive either gilteritinib (at a dose of 120 mg per day) or salvage chemotherapy. The two primary end points were overall survival and the percentage of patients who had complete remission with full or partial hematologic recovery. Secondary end points included event-free survival (freedom from treatment failure [i.e., relapse or lack of remission] or death) and the percentage of patients who had complete remission. RESULTS: Of 371 eligible patients, 247 were randomly assigned to the gilteritinib group and 124 to the salvage chemotherapy group. The median overall survival in the gilteritinib group was significantly longer than that in the chemotherapy group (9.3 months vs. 5.6 months; hazard ratio for death, 0.64; 95% confidence interval [CI], 0.49 to 0.83; P<0.001). The median event-free survival was 2.8 months in the gilteritinib group and 0.7 months in the chemotherapy group (hazard ratio for treatment failure or death, 0.79; 95% CI, 0.58 to 1.09). The percentage of patients who had complete remission with full or partial hematologic recovery was 34.0% in the gilteritinib group and 15.3% in the chemotherapy group (risk difference, 18.6 percentage points; 95% CI, 9.8 to 27.4); the percentages with complete remission were 21.1% and 10.5%, respectively (risk difference, 10.6 percentage points; 95% CI, 2.8 to 18.4). In an analysis that was adjusted for therapy duration, adverse events of grade 3 or higher and serious adverse events occurred less frequently in the gilteritinib group than in the chemotherapy group; the most common adverse events of grade 3 or higher in the gilteritinib group were febrile neutropenia (45.9%), anemia (40.7%), and thrombocytopenia (22.8%). CONCLUSIONS: Gilteritinib resulted in significantly longer survival and higher percentages of patients with remission than salvage chemotherapy among patients with relapsed or refractory FLT3-mutated AML. (Funded by Astellas Pharma; ADMIRAL ClinicalTrials.gov number, NCT02421939.).

Clinical profile of gilteritinib in Japanese patients with relapsed/refractory acute myeloid leukemia: An open-label phase 1 study.

Gilteritinib, a novel, highly specific, potent fms-like tyrosine kinase 3/AXL inhibitor, demonstrated antileukemic activity in patients with relapsed/refractory (R/R) acute myeloid leukemia (AML). In this open-label phase 1 study (NCT02181660), Japanese patients (aged ≥18 years) with R/R AML received once-daily gilteritinib, escalating from 20 to 300 mg/d. Primary endpoints were safety/tolerability, including the maximum tolerated dose (MTD) and the recommended dose (RD); secondary endpoints were antileukemic activity and pharmacokinetics (PK). Twenty-four Japanese patients with R/R AML received once-daily oral gilteritinib in 1 of 6 dose-escalation cohorts (20, 40, 80, 120, 200, and 300 mg/d). Gilteritinib was well tolerated. The MTD was 200 mg/d; dose-limiting toxicities were grade 3 tumor lysis syndrome (120 mg/d; n = 1); and grade 3 elevated blood lactate dehydrogenase, amylase, blood creatine phosphokinase levels, and syncope (all n = 2; 300 mg/d). The RD was 120 mg/d. The most common drug-related grade ≥3 adverse events were thrombocytopenia (n = 4 [16.7%]) and increased blood creatine phosphokinase (n = 3 [12.5%]). Gilteritinib had a dose-proportional PK profile. Among patients with mutated fms-like tyrosine kinase 3, the overall response rate (ORR) was 80% (n = 4 of 5; complete remission [CR] with incomplete platelet recovery, 1 [20%]; CR with incomplete hematologic recovery, 2 [40%]; partial remission (PR), 1 [20%]). Among patients with wild-type fms-like tyrosine kinase 3, ORR was 36.4%; (n = 4 of 11; CR, 1 [9.1%]; CR with incomplete platelet recovery, 2 [18.2%]; PR, 1 [9.1%]). In conclusion, gilteritinib was well tolerated and demonstrated antileukemic activity in a Japanese R/R AML population.

A next-generation sequencing-based assay for minimal residual disease assessment in AML patients with FLT3-ITD mutations.

Internal tandem duplications in fms-like tyrosine kinase 3 (FLT3-ITDs) are common in acute myeloid leukemia (AML) and confer a poor prognosis. A sensitive and specific assay for the detection of minimal residual disease (MRD) in FLT3-ITD mutated AML could guide therapy decisions. Existing assays for MRD in FLT3-ITD AML have not been particularly useful because of limited sensitivity. We developed a sensitive and specific MRD assay for FLT3-ITD mutations using next-generation sequencing. The initial validation of this assay was performed by spiking fixed amounts of mutant DNA into wild-type DNA to establish a sensitivity of detection equivalent to ≥1 FLT3-ITD-containing cell in 10 000, with a minimum input of 100 000 cell equivalents of DNA. We subsequently validated the assay in bone marrow samples from patients with FLT3-ITD AML in remission. Finally, we analyzed bone marrow samples from 80 patients with FLT3-ITD relapsed/refractory AML participating in a trial of a novel FLT3 inhibitor, gilteritinib, and demonstrated a relationship between the mutation burden, as detected by the assay, and overall survival. This novel MRD assay is specific and 2 orders of magnitude more sensitive than currently available polymerase chain reaction- or next-generation sequencing-based FLT3-ITD assays. The assay is being prospectively validated in ongoing randomized clinical trials.

Selective inhibition of FLT3 by gilteritinib in relapsed or refractory acute myeloid leukaemia: a multicentre, first-in-human, open-label, phase 1-2 study.

BACKGROUND: Internal tandem duplication mutations in FLT3 are common in acute myeloid leukaemia and are associated with rapid relapse and short overall survival. The clinical benefit of FLT3 inhibitors in patients with acute myeloid leukaemia has been limited by rapid generation of resistance mutations, particularly in codon Asp835 (D835). We aimed to assess the highly selective oral FLT3 inhibitor gilteritinib in patients with relapsed or refractory acute myeloid leukaemia. METHODS: In this phase 1-2 trial, we enrolled patients aged 18 years or older with acute myeloid leukaemia who either were refractory to induction therapy or had relapsed after achieving remission with previous treatment. Patients were enrolled into one of seven dose-escalation or dose-expansion cohorts assigned to receive once-daily doses of oral gilteritinib (20 mg, 40 mg, 80 mg, 120 mg, 200 mg, 300 mg, or 450 mg). Cohort expansion was based on safety and tolerability, FLT3 inhibition in correlative assays, and antileukaemic activity. Although the presence of an FLT3 mutation was not an inclusion criterion, we required ten or more patients with locally confirmed FLT3 mutations (FLT3mut+) to be enrolled in expansion cohorts at each dose level. On the basis of emerging findings, we further expanded the 120 mg and 200 mg dose cohorts to include FLT3mut+ patients only. The primary endpoints were the safety, tolerability, and pharmacokinetics of gilteritinib. Safety and tolerability were assessed in the safety analysis set (all patients who received at least one dose of gilteritinib). Responses were assessed in the full analysis set (all patients who received at least one dose of study drug and who had at least one datapoint post-treatment). Pharmacokinetics were assessed in a subset of the safety analysis set for which sufficient data for concentrations of gilteritinib in plasma were available to enable derivation of one or more pharmacokinetic variables. This study is registered with ClinicalTrials.gov, number NCT02014558, and is ongoing. FINDINGS: Between Oct 15, 2013, and Aug 27, 2015, 252 adults with relapsed or refractory acute myeloid leukaemia received oral gilteritinib once daily in one of seven dose-escalation (n=23) or dose-expansion (n=229) cohorts. Gilteritinib was well tolerated; the maximum tolerated dose was established as 300 mg/day when two of three patients enrolled in the 450 mg dose-escalation cohort had two dose-limiting toxicities (grade 3 diarrhoea and grade 3 elevated aspartate aminotransferase). The most common grade 3-4 adverse events irrespective of relation to treatment were febrile neutropenia (97 [39%] of 252), anaemia (61 [24%]), thrombocytopenia (33 [13%]), sepsis (28 [11%]), and pneumonia (27 [11%]). Commonly reported treatment-related adverse events were diarrhoea (92 [37%] of 252]), anaemia (86 [34%]), fatigue (83 [33%]), elevated aspartate aminotransferase (65 [26%]), and increased alanine aminotransferase (47 [19%]). Serious adverse events occurring in 5% or more of patients were febrile neutropenia (98 [39%] of 252; five related to treatment), progressive disease (43 [17%]), sepsis (36 [14%]; two related to treatment), pneumonia (27 [11%]), acute renal failure (25 [10%]; five related to treatment), pyrexia (21 [8%]; three related to treatment), bacteraemia (14 [6%]; one related to treatment), and respiratory failure (14 [6%]). 95 people died in the safety analysis set, of which seven deaths were judged possibly or probably related to treatment (pulmonary embolism [200 mg/day], respiratory failure [120 mg/day], haemoptysis [80 mg/day], intracranial haemorrhage [20 mg/day], ventricular fibrillation [120 mg/day], septic shock [80 mg/day], and neutropenia [120 mg/day]). An exposure-related increase in inhibition of FLT3 phosphorylation was noted with increasing concentrations in plasma of gilteritinib. In-vivo inhibition of FLT3 phosphorylation occurred at all dose levels. At least 90% of FLT3 phosphorylation inhibition was seen by day 8 in most patients receiving a daily dose of 80 mg or higher. 100 (40%) of 249 patients in the full analysis set achieved a response, with 19 (8%) achieving complete remission, ten (4%) complete remission with incomplete platelet recovery, 46 (18%) complete remission with incomplete haematological recovery, and 25 (10%) partial remission INTERPRETATION: Gilteritinib had a favourable safety profile and showed consistent FLT3 inhibition in patients with relapsed or refractory acute myeloid leukaemia. These findings confirm that FLT3 is a high-value target for treatment of relapsed or refractory acute myeloid leukaemia; based on activity data, gilteritinib at 120 mg/day is being tested in phase 3 trials. FUNDING: Astellas Pharma, National Cancer Institute (Leukemia Specialized Program of Research Excellence grant), Associazione Italiana Ricerca sul Cancro.

First-in-human, open-label dose-escalation and dose-expansion study of the safety, pharmacokinetics, and antitumor effects of an oral ALK inhibitor ASP3026 in patients with advanced solid tumors.

BACKGROUND: ASP3026 is a second-generation anaplastic lymphoma kinase (ALK) inhibitor that has potent in vitro activity against crizotinib-resistant ALK-positive tumors. This open-label, multicenter, first-in-human phase I study ( NCT01284192 ) assessed the safety, pharmacokinetic profile, and antitumor activity of ASP3026. METHODS: Advanced solid tumor patients received oral ASP3026 in 3 + 3 dose-escalation cohorts at doses of 25-800 mg once daily in 28-day cycles. The endpoints were to identify the maximum tolerated dose (MTD), the recommended phase II dose (RP2D), and the pharmacokinetic profile of ASP3026. A phase Ib expansion cohort enrolled patients with metastatic, crizotinib-resistant ALK-positive solid tumors at the RP2D, and response was evaluated by RECIST 1.1. RESULTS: The dose-escalation cohort enrolled 33 patients, including three crizotinib-resistant, ALK-positive patients, and the dose-expansion cohort enrolled another 13 crizotinib-resistant, ALK-positive non-small cell lung cancer (NSCLC) patients. ASP3026 demonstrated both linear pharmacokinetics and dose-proportional exposure for area under the plasma concentration-time curve and maximum concentration observed with a median terminal half-life of 35 h, supporting the daily dosing. Grade 3 rash and elevated transaminase concentrations were dose-limiting toxicities observed at 800 mg; hence, 525 mg daily was the MTD and RP2D. The most common treatment-related adverse events were nausea (38%), fatigue (35%), and vomiting (35 %). Among the 16 patients with crizotinib-resistant ALK-positive tumors (15 NSCLC, 1 neuroblastoma), eight patients achieved partial response (overall response rate 50%; 95% confidence interval 25-75%) and seven patients (44%) achieved stable disease. CONCLUSIONS: ASP3026 was well tolerated and had therapeutic activity in patients with crizotinib-resistant ALK-positive advanced tumors. TRIAL REGISTRATION: ClinTrials.gov: NCT01284192.

The Patient Perspective on Living with Acute Myeloid Leukemia.

INTRODUCTION: Acute myeloid leukemia (AML) imposes significant burden on patients, their families, and the healthcare system. Published literature has reported many AML signs and symptoms, as well as their impact on patients. However, there are no publications on the experience of living with AML from the patient's perspective. In this study, we performed qualitative interviews with patients with AML to understand their experience. METHODS: Participants were recruited from the US and Japan. All patients were screened to assess eligibility, and were divided into four subgroups (i.e., newly-diagnosed, high-intensity chemotherapy; newly-diagnosed, low-intensity chemotherapy; relapse/refractory; and post-transplant). Patients were interviewed over the phone by a trained researcher and asked about their day-to-day experience with AML. Signs/symptoms and impacts were coded, analyzed using Atlas.ti software, and reported as frequencies, with the medians of patient-reported disturbance levels (0-10) computed for each symptom and impact. RESULTS: The most commonly reported sign/symptom in the US was fatigue (95.7%), followed by bruising and weakness (both 78.3%), and in Japan, nausea (94.4%), followed by fatigue and headache (both 88.9%). The most commonly reported impact in the US was a decreased ability to maintain social/familial roles (91.3%), followed by anxiety and a decreased ability to function (both 87.0%), and most commonly reported in Japan was anxiety, a decreased ability to function, and remission uncertainty (94.4%). CONCLUSION: Although the frequency of signs/symptoms and their level of disturbance varied between the US and Japan, there was remarkable consistency in the types of signs/symptoms and impacts reported across all patients. The consistency in the experience of the disease across patients suggests that measurement of AML experience can be achieved by using the same tool for most, if not all, of these patients. FUNDING: Astellas Pharma Inc., Northbrook, IL, USA.

Differences in the phenotype, cytokine gene expression profiles, and in vivo alloreactivity of T cells mobilized with plerixafor compared with G-CSF.

Plerixafor (Mozobil) is a CXCR4 antagonist that rapidly mobilizes CD34(+) cells into circulation. Recently, plerixafor has been used as a single agent to mobilize peripheral blood stem cells for allogeneic hematopoietic cell transplantation. Although G-CSF mobilization is known to alter the phenotype and cytokine polarization of transplanted T cells, the effects of plerixafor mobilization on T cells have not been well characterized. In this study, we show that alterations in the T cell phenotype and cytokine gene expression profiles characteristic of G-CSF mobilization do not occur after mobilization with plerixafor. Compared with nonmobilized T cells, plerixafor-mobilized T cells had similar phenotype, mixed lymphocyte reactivity, and Foxp3 gene expression levels in CD4(+) T cells, and did not undergo a change in expression levels of 84 genes associated with Th1/Th2/Th3 pathways. In contrast with plerixafor, G-CSF mobilization decreased CD62L expression on both CD4 and CD8(+) T cells and altered expression levels of 16 cytokine-associated genes in CD3(+) T cells. To assess the clinical relevance of these findings, we explored a murine model of graft-versus-host disease in which transplant recipients received plerixafor or G-CSF mobilized allograft from MHC-matched, minor histocompatibility-mismatched donors; recipients of plerixafor mobilized peripheral blood stem cells had a significantly higher incidence of skin graft-versus-host disease compared with mice receiving G-CSF mobilized transplants (100 versus 50%, respectively, p = 0.02). These preclinical data show plerixafor, in contrast with G-CSF, does not alter the phenotype and cytokine polarization of T cells, which raises the possibility that T cell-mediated immune sequelae of allogeneic transplantation in humans may differ when donor allografts are mobilized with plerixafor compared with G-CSF.

Adult human mesenchymal stem cells added to corticosteroid therapy for the treatment of acute graft-versus-host disease.

The unique immunomodulatory properties of mesenchymal stem cells (MSCs) make them a rationale agent to investigate for graft-versus-host disease (GVHD). Human MSCs were used to treat de novo acute GVHD (aGVHD). Patients with grades II-IV GVHD were randomized to receive 2 treatments of human MSCs (Prochymal(R)) at a dose of either 2 or 8 million MSCs/kg in combination with corticosteroids. Patients received GVHD prophylaxis with tacrolimus, cyclosporine, (CsA) or mycophenolate mofetil (MMF). Study endpoints included safety of Prochymal administration, induction of response to Prochymal, and overall response of aGVHD by day 28, and long-term safety. Thirty-two patients were enrolled, with 31 evaluable: 21 males, 10 females; median age 52 years (range: 34-67). Twenty-one patients had grade II, 8 had grade III, and 3 had grade IV aGVHD. Ninety-four percent of patients had an initial response to Prochymal (77% complete response [CR] and 16% partial response [PR]). No infusional toxicities or ectopic tissue formations were reported. There was no difference with respect to safety or efficacy between the low and high Prochymal dose. In conclusion, Prochymal can be infused safely into patients with aGVHD and induces response in a high proportion of GVHD patients.

Chimeric receptor mRNA transfection as a tool to generate antineoplastic lymphocytes.

mRNA transfection is a useful approach for temporal cell reprogramming with minimal risk of transgene-mediated mutagenesis. We applied this to redirect lymphocyte cytotoxicity toward malignant cells. Using the chimeric immune receptor (CIR) constructs anti-CD19 CIR and 8H9 CIR, we achieved uniform expression of CIRs on virtually the entire population of lymphocytes. We reprogrammed CD3+ CD8+, CD3+ CD4+, and natural killer (NK ) cells toward autologous and allogeneic targets such as B cells, Daudi lymphoma, primary melanoma, breast ductal carcinoma, breast adenocarcinoma, and rhabdomyosarcoma. The reprogramming procedure is fast. Although most of the experiments were performed on lymphocytes obtained after 7-day activation, only 1-day activation of T cells with anti-CD3, anti-CD28 antibodies, and interleukin-2 is sufficient to develop both lymphocyte cytotoxicity and competence for mRNA transfer. The entire procedure, which includes lymphocyte activation and reprogramming, can be completed in 2 days. The efficiency of mRNA-modified human T cells was tested in a murine xenograft model. Human CD3+CD8+ lymphocytes expressing anti-CD19 CIR mRNA inhibited Daudi lymphoma growth in NOD=SCID mice. These results demonstrate that a mixed population of cytotoxic lymphocytes, including T cells together with NK cells, can be quickly and simultaneously reprogrammed by mRNA against autologous malignancies. With relatively minor modifications the described method of lymphocyte reprogramming can be scaled up for cancer therapy.

Synthetic messenger RNA as a tool for gene therapy.

Transfection of human cells with DNA in biomedical applications carries the risk of insertional mutagenesis. Transfection with mRNA avoids this problem; however, in vitro production of mRNA, based on preliminary DNA template cloning in special vectors, is a laborious and time-consuming procedure. We report an efficient vectorfree method of mRNA production from polymerase chain reaction-generated DNA templates. For all cell types tested mRNA was transfected more readily than DNA, and its expression was highly uniform in cell populations. Even cell types relatively resistant to transfection with DNA could express transfected mRNA well. The level of mRNA expression could be controlled over a wide range by changing the amount of input RNA. Cells could be efficiently and simultaneously loaded with several different transcripts. To test a potential clinical application of this method, we transfected human T lymphocytes with mRNA encoding a chimeric immune receptor directed against CD19, a surface antigen widely expressed in leukemia and lymphoma. The transfected mRNA conferred powerful cytotoxicity to T cells against CD19+ targets from the same donor. These results demonstrate that this method can be applied to generate autologous T lymphocytes directed toward malignant cells.

Early reconstitution of the T-cell repertoire after non-myeloablative peripheral blood stem cell transplantation is from post-thymic T-cell expansion and is unaffected by graft-versus-host disease or mixed chimaerism.

To study immune recovery after non-myeloablative, reduced-intensity stem cell allografts (NST) and T-cell-depleted myeloablative transplants (TCD), we measured T-cell subset recovery by flow cytometry, T-cell repertoire by spectratyping and thymic T-cell output using a T-cell receptor excision circle (TREC) assay. We found a rapid and comparable increase in lymphocyte numbers in both NST and TCD, supporting the presence of a powerful drive for lymphocyte recovery after transplant. Spectratyping on d 45 and 100 revealed almost complete normalization of the T-cell repertoire in NST patients by d 45, whereas TCD patients demonstrated marked skewing of the repertoire, persisting to d 100. After NST, there was a significantly higher number of TREC-positive CD4+ and CD8+ cells (P = 0.02 and P = 0.01 respectively). However, in both NST and TCD, early T-cell recovery after transplant appeared to result entirely from post-thymic T cells, the expansion pattern of which is most influenced by the starting T-cell dose, but not markedly by graft-versus-host disease (GVHD) or mixed chimaerism. These results define important qualitative differences in the T-cell repertoire according to the type of transplant schedule used.

Antithymocyte globulin for treatment of the bone marrow failure associated with myelodysplastic syndromes.

BACKGROUND: Almost half of the deaths that result from myelodysplastic syndromes are due to cytopenia associated with bone marrow failure. Treatment is mostly supportive care. OBJECTIVE: To determine whether treatment with antithymocyte globulin improves cytopenia and reverses dependence on red blood cell transfusions in patients with myelodysplastic syndromes. DESIGN: Single-treatment, prospective study. SETTING: Tertiary referral center. PATIENTS: 61 patients with myelodysplastic syndromes. INTERVENTION: Antithymocyte globulin, 40 mg/kg of body weight, given daily for 4 days. MEASUREMENTS: Evaluation of bone marrow, blood counts, transfusions, progression, and survival for a median of 30 months (range, 1 to 88 months). RESULTS: Within 8 months of treatment, 21 of 61 patients (34%) no longer required red blood cell transfusions. This independence from transfusions was maintained in 17 responders (81%) for a median of 36 months (range, 3 to 72 months). Ten of 21 patients (47.5%) with severe thrombocytopenia had sustained platelet count increases, and 6 of 11 patients (55%) with severe neutropenia had sustained neutrophil counts of greater than 1 x 10(9) cells/L. Characteristics favorable for response were younger patient age (P = 0.005) and lower platelet counts (P = 0.038). One of the 21 responders (5%) and 22 of the 40 nonresponders (55%) died before the end of the study (P = 0.008). One of the 21 responders (5%) and 13 of the 40 nonresponders (33%) had disease progression (P = 0.086). CONCLUSIONS: Although this study was a nonrandomized, single-treatment study, 34% of patients treated with antithymocyte globulin became transfusion independent. Response was associated with a statistically significant longer survival and an almost significant decreased time to disease progression. Treatment with antithymocyte globulin did not seem to be detrimental because historical overall median survival times were similar to those of nonresponders.