First in class dual MDM2/MDMX inhibitor ALRN-6924 enhances antitumor efficacy of chemotherapy in TP53 wild-type hormone receptor-positive breast cancer models.

BACKGROUND: MDM2/MDMX proteins are frequently elevated in hormone receptor-positive (ER+) breast cancer. We sought to determine the antitumor efficacy of the combination of ALRN-6924, a dual inhibitor of MDM2/MDMX, with chemotherapy in ER+ breast cancer models. METHODS: Three hundred two cell lines representing multiple tumor types were screened to confirm the role of TP53 status in ALRN-6924 efficacy. ER+ breast cancer cell lines (MCF-7 and ZR-75-1) were used to investigate the antitumor efficacy of ALRN-6924 combination. In vitro cell proliferation, cell cycle, and apoptosis assays were performed. Xenograft tumor volumes were measured, and reverse-phase protein array (RPPA), immunohistochemistry (IHC), and TUNEL assay of tumor tissues were performed to evaluate the in vivo pharmacodynamic effects of ALRN-6924 with paclitaxel. RESULTS: ALRN-6924 was active in wild-type TP53 (WT-TP53) cancer cell lines, but not mutant TP53. On ER+ breast cancer cell lines, it was synergistic in vitro and had enhanced in vivo antitumor activity with both paclitaxel and eribulin. Flow cytometry revealed signs of mitotic crisis in all treatment groups; however, S phase was only decreased in MCF-7 single agent and combinatorial ALRN-6924 arms. RPPA and IHC demonstrated an increase in p21 expression in both combinatorial and single agent ALRN-6924 in vivo treatment groups. Apoptotic assays revealed a significantly enhanced in vivo apoptotic rate in ALRN-6924 combined with paclitaxel treatment arm compared to either single agent. CONCLUSION: The significant synergy observed with ALRN-6924 in combination with chemotherapeutic agents supports further evaluation in patients with hormone receptor-positive breast cancer.

Essential role of Jun family transcription factors in PU.1 knockdown-induced leukemic stem cells.

Knockdown of the transcription factor PU.1 (encoded by Sfpi1) leads to acute myeloid leukemia (AML) in mice. We examined the transcriptome of preleukemic hematopoietic stem cells (HSCs) in which PU.1 was knocked down (referred to as 'PU.1-knockdown HSCs') to identify transcriptional changes preceding malignant transformation. Transcription factors c-Jun and JunB were among the top-downregulated targets. Restoration of c-Jun expression in preleukemic cells rescued the PU.1 knockdown-initiated myelomonocytic differentiation block. Lentiviral restoration of JunB at the leukemic stage led to loss of leukemic self-renewal capacity and prevented leukemia in NOD-SCID mice into which leukemic PU.1-knockdown cells were transplanted. Examination of human individuals with AML confirmed the correlation between PU.1 and JunB downregulation. These results delineate a transcriptional pattern that precedes leukemic transformation in PU.1-knockdown HSCs and demonstrate that decreased levels of c-Jun and JunB contribute to the development of PU.1 knockdown-induced AML by blocking differentiation and increasing self-renewal. Therefore, examination of disturbed gene expression in HSCs can identify genes whose dysregulation is essential for leukemic stem cell function and that are targets for therapeutic interventions.

Discovery of Sulanemadlin (ALRN-6924), the First Cell-Permeating, Stabilized α-Helical Peptide in Clinical Development.

We report the discovery of sulanemadlin (ALRN-6924), the first cell-permeating, stabilized α-helical peptide to enter clinical trials. ALRN-6924 is a "stapled peptide" that mimics the N-terminal domain of the p53 tumor suppressor protein. It binds with high affinity to both MDM2 and MDMX (also known as MDM4), the endogenous inhibitors of p53, to activate p53 signaling in cells having a non-mutant, or wild-type TP53 genotype (TP53-WT). Iterative structure-activity optimization endowed ALRN-6924 with favorable cell permeability, solubility, and pharmacokinetic and safety profiles. Intracellular proteolysis of ALRN-6924 forms a long-acting active metabolite with potent MDM2 and MDMX binding affinity and slow dissociation kinetics. At high doses, ALRN-6924 exhibits on-mechanism anticancer activity in TP53-WT tumor models. At lower doses, ALRN-6924 transiently arrests the cell cycle in healthy tissues to protect them from chemotherapy without protecting the TP53-mutant cancer cells. These results support the continued clinical evaluation of ALRN-6924 as an anticancer and chemoprotection agent.

Eltrombopag for management of chronic immune thrombocytopenia (RAISE): a 6-month, randomised, phase 3 study.

BACKGROUND: Eltrombopag is an oral thrombopoietin receptor agonist for the treatment of thrombocytopenia. We aimed to compare the response to once daily eltrombopag versus placebo in patients with chronic immune thrombocytopenia during a 6-month period. METHODS: We undertook a phase 3, double-blind, placebo-controlled study in adults with previously treated immune thrombocytopenia of more than 6 months' duration who had baseline platelet counts lower than 30,000 per µL. Patients were randomly allocated (in a 2:1 ratio) treatment with local standard of care plus 50 mg eltrombopag or matching placebo once daily for 6 months. Randomisation was done centrally with a computer-generated randomisation schedule and was stratified by baseline platelet count (≤ 15,000 per µL), use of treatment for immune thrombocytopenia, and splenectomy status. Patients, investigators, and those assessing data were masked to allocation. Dose modifications were made on the basis of platelet response. Patients were assessed for response to treatment (defined as a platelet count of 50,000-400,000 per µL) weekly during the first 6 weeks and at least once every 4 weeks thereafter; the primary endpoint was the odds of response to eltrombopag versus placebo. Analysis was by intention to treat. This study is registered at ClinicalTrials.gov, number NCT00370331. FINDINGS: Between Nov 22, 2006, and July 31, 2007, 197 patients were randomly allocated to treatment groups and were included in the intention-to-treat analysis (135 eltrombopag, 62 placebo). 106 (79%) patients in the eltrombopag group responded to treatment at least once during the study, compared with 17 (28%) patients in the placebo group. The odds of responding were greater in patients in the eltrombopag group compared with those in the placebo group throughout the 6-month treatment period (odds ratio 8·2, 99% CI 3·59-18·73; p<0·0001). 37 (59%) patients receiving eltrombopag reduced concomitant treatment versus ten (32%) patients receiving placebo (p=0·016). 24 (18%) patients receiving eltrombopag needed rescue treatment compared with 25 (40%) patients receiving placebo (p=0·001). Three (2%) patients receiving eltrombopag had thromboembolic events compared with none in patients on placebo. Nine (7%) eltrombopag-treated patients and two (3%) in the placebo group had mild increases in alanine aminotransferase concentration, and five (4%) eltrombopag-treated patients (vs none allocated to placebo) had increases in total bilirubin. Four (7%) patients taking placebo had serious bleeding events, compared with one (<1%) patient treated with eltrombopag. INTERPRETATION: Eltrombopag is effective for management of chronic immune thrombocytopenia, and could be particularly beneficial for patients who have not responded to splenectomy or previous treatment. These benefits should be balanced with the potential risks associated with eltrombopag treatment. FUNDING: GlaxoSmithKline.

Effect of the nonpeptide thrombopoietin receptor agonist Eltrombopag on bone marrow cells from patients with acute myeloid leukemia and myelodysplastic syndrome.

Thrombocytopenia is a frequent symptom and clinical challenge in patients with myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). Eltrombopag is a small molecule thrombopoietin receptor agonist that might be a new option to treat thrombocytopenia in these diseases, provided that it does not stimulate malignant hematopoiesis. In this work, we studied the effects of Eltrombopag on proliferation, apoptosis, differentiation, colony formation, and malignant self-renewal of bone marrow mononuclear cells of patients with AML and MDS. Malignant bone marrow mononuclear cells did not show increased proliferation, or increased clonogenic capacity at concentrations of Eltrombopag ranging from 0.1 to 30 microg/mL. On the contrary, we observed a moderate, statistically nonsignificant (P = .18), decrease of numbers of malignant cells (mean, 56%; SD, 28%). Eltrombopag neither led to increased 5-bromo-2-deoxyuridine incorporation, decreased apoptosis, an increase of malignant self-renewal, nor enhanced in vivo engraftment in xenotransplantations. Furthermore, we found that Eltrombopag was capable of increasing megakaryocytic differentiation and formation of normal megakaryocytic colonies in patients with AML and MDS. These results provide a preclinical rationale for further testing of Eltrombopag for treatment of thrombocytopenia in AML and MDS.

Hepatobiliary laboratory abnormalities among patients with chronic or persistent immune thrombocytopenia (ITP).

Therapies for immune thrombocytopenia (ITP) may be associated with abnormal hepatobiliary laboratory (HBL) values, but the epidemiology of these abnormalities is unknown in the ITP population. The study aim was to provide prevalence and incidence rates, as well as risk factors for abnormal HBL values among a cohort of patients with chronic or persistent primary ITP. Health insurance claims data from 3,244 patients with chronic or persistent ITP was examined to estimate the prevalence of abnormal HBL values: elevated levels of Alanine Aminotransferase (ALT), Aspartate Aminotransferase (AST), total bilirubin, and Alkaline Phosphatase (ALP). Incidence of abnormal HBL values was estimated in a sub cohort of 2557 (79%) patients without evidence of comorbidities related to secondary thrombocytopenia, liver disease, or abnormal HBL values during the 12-month baseline period. The baseline prevalence of ALT and AST > 3x the upper limit of normal (ULN) was 4.6 and 3.7%, respectively. The baseline prevalence of total bilirubin and ALP >1.5x ULN was 4.2 and 3.2%, respectively. The incidence rate of new HBL abnormalities (HBLA) was 1.24/1,000 person-years (95% CI: 0.52-2.56) for ALT>3x ULN and 0.41/1,000 person-years (95% CI: 0.08-1.32) for AST>3x ULN. HBLAs were significantly associated with male gender, liver disease, diabetes, congestive heart failure, lupus, hematological cancers, and HIV infection. In conclusion, the prevalence of HBLA, specifically ALT>3x ULN, among the ITP population is relatively high compared with atrial fibrillation, though within the confidence interval for that estimate. HBLAs were significantly associated with male gender, liver disease, and several other comorbidities, thus, distinguishing drug-induced liver injury in this population is clinically challenging.

Pharmacologic Activation of p53 Triggers Viral Mimicry Response Thereby Abolishing Tumor Immune Evasion and Promoting Antitumor Immunity.

The repression of repetitive elements is an important facet of p53's function as a guardian of the genome. Paradoxically, we found that p53 activated by MDM2 inhibitors induced the expression of endogenous retroviruses (ERV) via increased occupancy on ERV promoters and inhibition of two major ERV repressors, histone demethylase LSD1 and DNA methyltransferase DNMT1. Double-stranded RNA stress caused by ERVs triggered type I/III interferon expression and antigen processing and presentation. Pharmacologic activation of p53 in vivo unleashed the IFN program, promoted T-cell infiltration, and significantly enhanced the efficacy of checkpoint therapy in an allograft tumor model. Furthermore, the MDM2 inhibitor ALRN-6924 induced a viral mimicry pathway and tumor inflammation signature genes in patients with melanoma. Our results identify ERV expression as the central mechanism whereby p53 induction overcomes tumor immune evasion and transforms tumor microenvironment to a favorable phenotype, providing a rationale for the synergy of MDM2 inhibitors and immunotherapy. SIGNIFICANCE: We found that p53 activated by MDM2 inhibitors induced the expression of ERVs, in part via epigenetic factors LSD1 and DNMT1. Induction of IFN response caused by ERV derepression upon p53-targeting therapies provides a possibility to overcome resistance to immune checkpoint blockade and potentially transform "cold" tumors into "hot." This article is highlighted in the In This Issue feature, p. 2945.

Phase 1 Trial of ALRN-6924, a Dual Inhibitor of MDMX and MDM2, in Patients with Solid Tumors and Lymphomas Bearing Wild-type TP53.

PURPOSE: We describe the first-in-human dose-escalation trial for ALRN-6924, a stabilized, cell-permeating peptide that disrupts p53 inhibition by mouse double minute 2 (MDM2) and MDMX to induce cell-cycle arrest or apoptosis in TP53-wild-type (WT) tumors. PATIENTS AND METHODS: Two schedules were evaluated for safety, pharmacokinetics, pharmacodynamics, and antitumor effects in patients with solid tumors or lymphomas. In arm A, patients received ALRN-6924 by intravenous infusion once-weekly for 3 weeks every 28 days; arm B was twice-weekly for 2 weeks every 21 days. RESULTS: Seventy-one patients were enrolled: 41 in arm A (0.16-4.4 mg/kg) and 30 in arm B (0.32-2.7 mg/kg). ALRN-6924 showed dose-dependent pharmacokinetics and increased serum levels of MIC-1, a biomarker of p53 activation. The most frequent treatment-related adverse events were gastrointestinal side effects, fatigue, anemia, and headache. In arm A, at 4.4 mg/kg, dose-limiting toxicities (DLT) were grade 3 (G3) hypotension, G3 alkaline phosphatase elevation, G3 anemia, and G4 neutropenia in one patient each. At the MTD in arm A of 3.1 mg/kg, G3 fatigue was observed in one patient. No DLTs were observed in arm B. No G3/G4 thrombocytopenia was observed in any patient. Seven patients had infusion-related reactions; 3 discontinued treatment. In 41 efficacy-evaluable patients with TP53-WT disease across both schedules the disease control rate was 59%. Two patients had confirmed complete responses, 2 had confirmed partial responses, and 20 had stable disease. Six patients were treated for >1 year. The recommended phase 2 dose was schedule A, 3.1 mg/kg. CONCLUSIONS: ALRN-6924 was well tolerated and demonstrated antitumor activity.

Platelet counts and haemorrhagic diathesis in patients with myelodysplastic syndromes.

OBJECTIVES: Most patients with myelodysplastic syndromes (MDS) present with single or multiple lineage cytopenias in peripheral blood despite a hypercellular bone marrow. Thrombocytopenia, attributable to ineffective platelet production by dysfunctional megakaryocytes, has been estimated to occur in 40-65% of patients. However, there are hardly any studies on the clinical relevance of low platelet counts in MDS. METHODS: We retrospectively analysed data from 2900 patients in the Duesseldorf MDS Registry who were diagnosed at our laboratory between 1982 and 2007. RESULTS: At the time of diagnosis, 43% of the patients had a platelet count lower than 100 000/microL. Platelets were lower than 20 000/microL in 7% of the patients, especially in those with advanced stages of MDS, who showed a higher frequency of thrombocytopenia and platelet transfusion dependency. On multivariate analysis, platelet anisometry, hypocellularity of megakaryopoiesis, maturational defects of megakaryocytes and platelets <20 000/microL were independent variables showing a statistically significant correlation (P < 0.05) with clinical signs of bleeding. Platelets lower than 100 000/microL were associated with significantly shortened survival (P < 0.00005), because of an increased risk of progression to acute myeloid leukaemia (AML) (30% vs. 21%) (P < 0.02) and bleeding (16% vs. 8%) (P = 0.0005). CONCLUSIONS: Thrombocytopenia is a strong predictor of short survival, with or without haemorrhagic complications.

Proteomic identification of interleukin-2 therapy response in metastatic renal cell cancer.

PURPOSE: To detect a predictive protein profile that distinguishes interleukin-2 therapy responders and nonresponders among patients with metastatic renal cell carcinoma we used surface-enhanced laser desorption/ionization time-of-flight mass spectrometry. MATERIALS AND METHODS: Protein extracts from 56 patients with metastatic clear cell patients renal cell carcinoma obtained from radical nephrectomy specimens before interleukin-2 therapy were applied to protein chip arrays of different chromatographic properties and analyzed using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry. A class prediction algorithm was applied to identify a subset of protein peaks with expression values associated with interleukin-2 response status. Multivariate analysis was performed to assess the association between the proteomic profile and interleukin-2 response status, controlling for the effect of lymphadenopathy. RESULTS: From 513 protein peaks we discovered a predictor set of 11 that performed optimally for predicting interleukin-2 response status with 86% accuracy (Fisher's p <0.004, permutation p <0.01). Results were validated in an independent data set with 72% overall accuracy (p <0.05, permutation p <0.01). On multivariate analysis the proteomic profile was significantly associated with the interleukin-2 response when corrected for lymph node status (p <0.04). CONCLUSIONS: We identified and validated a proteomic pattern that is an independent predictor of the interleukin-2 response. The ability to predict the probability of the interleukin-2 response could permit targeted selection of the patients most likely to respond to interleukin-2, while avoiding unwanted toxicity in patients less likely to respond. This proteomic predictor has the potential to significantly aid clinicians in the decision making of appropriate therapy for patients with metastatic renal cell carcinoma.

Dual inhibition of MDMX and MDM2 as a therapeutic strategy in leukemia.

The tumor suppressor p53 is often inactivated via its interaction with endogenous inhibitors mouse double minute 4 homolog (MDM4 or MDMX) or mouse double minute 2 homolog (MDM2), which are frequently overexpressed in patients with acute myeloid leukemia (AML) and other cancers. Pharmacological disruption of both of these interactions has long been sought after as an attractive strategy to fully restore p53-dependent tumor suppressor activity in cancers with wild-type p53. Selective targeting of this pathway has thus far been limited to MDM2-only small-molecule inhibitors, which lack affinity for MDMX. We demonstrate that dual MDMX/MDM2 inhibition with a stapled α-helical peptide (ALRN-6924), which has recently entered phase I clinical testing, produces marked antileukemic effects. ALRN-6924 robustly activates p53-dependent transcription at the single-cell and single-molecule levels and exhibits biochemical and molecular biological on-target activity in leukemia cells in vitro and in vivo. Dual MDMX/MDM2 inhibition by ALRN-6924 inhibits cellular proliferation by inducing cell cycle arrest and apoptosis in cell lines and primary AML patient cells, including leukemic stem cell-enriched populations, and disrupts functional clonogenic and serial replating capacity. Furthermore, ALRN-6924 markedly improves survival in AML xenograft models. Our study provides mechanistic insight to support further testing of ALRN-6924 as a therapeutic approach in AML and other cancers with wild-type p53.

Targetable vulnerabilities in T- and NK-cell lymphomas identified through preclinical models.

T- and NK-cell lymphomas (TCL) are a heterogenous group of lymphoid malignancies with poor prognosis. In contrast to B-cell and myeloid malignancies, there are few preclinical models of TCLs, which has hampered the development of effective therapeutics. Here we establish and characterize preclinical models of TCL. We identify multiple vulnerabilities that are targetable with currently available agents (e.g., inhibitors of JAK2 or IKZF1) and demonstrate proof-of-principle for biomarker-driven therapies using patient-derived xenografts (PDXs). We show that MDM2 and MDMX are targetable vulnerabilities within TP53-wild-type TCLs. ALRN-6924, a stapled peptide that blocks interactions between p53 and both MDM2 and MDMX has potent in vitro activity and superior in vivo activity across 8 different PDX models compared to the standard-of-care agent romidepsin. ALRN-6924 induced a complete remission in a patient with TP53-wild-type angioimmunoblastic T-cell lymphoma, demonstrating the potential for rapid translation of discoveries from subtype-specific preclinical models.

Age-related transcription levels of KU70, MGST1 and BIK in CD34+ hematopoietic stem and progenitor cells.

Despite the known longevity of human hematopoietic stem and progenitor cells (HSC), numerous functional impairments of these cells can be observed in an age-dependent manner. However, the molecular alterations associated with aging of HSC are largely unknown. Therefore, we scrutinized gene expression patterns of HSC from newborn, young and old healthy donors. CD34+ HSC were isolated via immuno-magnetic separation and evaluated by FACS analysis. We performed cDNA macroarray analyses on a first set of CD34+ samples (n=13). We found the genes encoding KU-antigen 70 kD (KU70), microsomal glutathione S-transferase 1 (MGST1) and BCL2-interacting killer (BIK) to possess age-related mRNA expression levels. KU70 is a DNA repair gene and part of the DNA-dependent protein kinase (DNA-PK) complex. Its expression was negatively correlated with donor age showing highest expression levels in newborn, 2.6-fold lower levels in young and 6.3-fold lower levels in old donors. The transcription levels of MGST1, a gene protecting against oxidative stress, progressively increased with age. Expression was lowest in newborn, 2.6-fold higher in young and 4.3-fold higher in old donors. BIK is a proapoptotic gene and its expression was positively correlated with donor age: lowest in newborn, 1.8-fold higher in young and 4.1-fold higher in old donors. These findings were confirmed with an independent, second set of CD34+ samples (n=16) by means of quantitative real-time RT-PCR. Elucidation of age-dependent molecular alterations in healthy HSC facilitate a better understanding of functional impairments in hematopoiesis and may become valuable for anti-aging drug development and the emerging field of regenerative medicine.

Reliable engraftment, low toxicity, and durable remissions following allogeneic blood stem cell transplantation with minimal conditioning.

OBJECTIVE: Allogeneic blood stem cell transplantation (BSCT) can cure patients with hematologic malignancies by high-dose chemotherapy and allogeneic graft-vs-tumor (GvT) reactions. To avoid high-dose conditioning and evaluate engraftment, toxicity, and GvT reactions, we treated a group of high-risk patients with a minimal intensive conditioning regimen followed by allogeneic BSCT. MATERIALS AND METHODS: Thirty-four patients with lymphoma (11), myeloma (10), chronic myeloid leukemia (4), myelodysplastic syndrome (5), and acute myeloid leukemia (4) were treated with fludarabine (3 x 30 mg/m(2)) and 200 cGy total-body irradiation followed by the infusion of peripheral blood stem cells from related (28) or unrelated (6) donors. Cyclosporine or tacrolimus and mycophenolate mofetile were given posttransplant. Most patients had advanced disease, were intensively pretreated, and had contraindications against conventional myeloablative transplantation. RESULTS: Thirty-two patients (94%) had engraftment of donor cells. Patients with lymphatic malignancies developed complete donor chimerism significantly faster than patients with myeloid malignancies (p < 0.05). Clinical responses were observed in 16 of 27 patients (59%) who had active disease at transplantation. Of 7 patients who were treated in remission, 5 remain free of disease. After a median follow-up of 325 days (range 100-844) 22 patients are alive (65%, 14 CR, 4 PR, 4 PD). Two patients (6%) died of treatment-related complications and 10 patients (29%) died of progressive disease. Acute graft-vs-host-disease (GvHD) of grade II or more developed in 17 patients (50%). Chronic GvHD is present in 10 of 22 patients (45%) who are alive beyond day 100. CONCLUSIONS: Toxicity and survival in this group of high-risk patients are superior to those expected with conventional allogeneic transplantation. GvT reactions frequently occur in conjunction with GvHD and can induce durable remissions in patients with advanced hematologic malignancies.

Bendamustine in the treatment of chronic lymphocytic leukemia: results and future perspectives.

Chronic lymphocytic leukemia (CLL) occurs predominantly in elderly patients. The treatment options for patients with CLL have increased with the introduction of purine analogs, and promising results have been reported with fludarabine and cladribine when these agents are used in newly diagnosed and relapsed disease. Monoclonal antibodies such as alemtuzumab and rituximab are also clinically active in CLL. The use of purine analogs in combination with monoclonal antibodies may provide additional treatment options and this strategy is being studied in patients with relapsed and refractory CLL. Bendamustine is an alkylating agent with properties of a purine analog and is a promising agent in the treatment of CLL. Bendamustine reduces the number of circulating B lymphocytes by over 90% and shows only partial cross-resistance with other alkylating agents, making it an ideal candidate for the treatment of CLL and for use in combination with other alkylating agents. Bendamustine monotherapy can be given to patients whose disease is refractory to standard therapies. The results of a trial using bendamustine as a salvage treatment in patients with relapsed or refractory, heavily pretreated CLL are discussed here. Bendamustine 100 mg/m(2) (days 1 and 2) was found to be an effective treatment for older patients with advanced CLL, with 14 of 21 patients responding. Complete hematologic remission was achieved in six of 21 patients and a further eight patients achieved a partial hematologic remission. The main toxicities were hematologic; nonhematologic side effects were mild and uncommon.

Treatment of secondary myelodysplastic syndrome after heart transplantation with chemotherapy and nonmyeloablative stem-cell transplantation.

BACKGROUND: Treatment of secondary cancer after solid-organ transplantation is difficult because of coexisting medical conditions, reduced organ function, or advanced age in most patients. METHODS: A 60-year-old man developed treatment-related myelodysplastic syndrome (refractory anemia with excess blasts in transformation) 10 years after orthotopic heart transplantation. After remission induction with chemotherapy, the patient received peripheral blood stem cells from his HLA-identical ABO-mismatched (A-->O) sister after conditioning with fludarabine and low-dose total-body irradiation (200 cGy). Postgrafting immunosuppression consisted of mycophenolate mofetil and cyclosporine A. RESULTS: The patient experienced little toxicity from the conditioning regimen and achieved complete donor chimerism within 65 days. Five months after transplant, the patient developed pure red cell aplasia that resolved after treatment. At present, he is alive in complete remission with 100% donor hematopoiesis 940 days after stem-cell transplantation. CONCLUSIONS: Allogeneic blood stem-cell transplantation using minimal conditioning is a new, promising treatment option for patients with hematologic malignancies after solid-organ transplantation.

Reduced proliferation of non-megakaryocytic acute myelogenous leukemia and other leukemia and lymphoma cell lines in response to eltrombopag.

Leukemia cell lines were treated with eltrombopag or thrombopoietin and their proliferative response was determined. Eltrombopag did not increase proliferation of cell lines that did not express high levels of megakaryocyte markers. Instead, treatment with eltrombopag alone inhibited proliferation of many cell lines (IC(50) range=0.56-21 microg/mL). The addition of other cytokines, such as G-CSF, Epo or Tpo, did not affect the decrease in proliferation. The decrease in proliferation appears to be through a TpoR-independent, nonapoptotic mechanism. These findings suggest that eltrombopag does not enhance, but rather inhibits, proliferation of leukemia cell lines in vitro.

Comparative analyses of the small molecule thrombopoietin receptor agonist eltrombopag and thrombopoietin on in vitro platelet function.

OBJECTIVE: The thrombopoietin receptor (TPOR) is a therapeutic target for treatment of thrombocytopenia because stimulation of this receptor results in enhanced megakaryocyte proliferation, differentiation, and ultimately platelet production. In addition to effects on megakaryocytes, TPOR stimulation also impacts platelet function. The present study examined platelet function following stimulation with the small molecule TPOR agonist eltrombopag. MATERIALS AND METHODS: Platelets were obtained from healthy volunteers, and signal transduction pathway activation was examined in washed platelet preparations. Platelet aggregation was examined in both washed platelet preparations and platelet-rich plasma. Platelet alpha-granule release was determined via fluorescein-activated cell sorting measurement of CD62P. RESULTS: In signal transduction studies of washed human platelets, eltrombopag induced the phosphorylation signal transducers and activators of transcription (STAT) proteins with no phosphorylation of Akt, whereas recombinant human TPO (rhTPO) induced the phosphorylation of Akt as well as STAT-1, -3, and -5. In studies conducted at subthreshold/submaximal concentrations of adenosine diphosphate (ADP) or collagen, eltrombopag pretreatment did not result in platelet aggregation. In contrast, rhTPO acted in synergy with submaximal concentrations of ADP or collagen to induce maximal aggregation under all conditions examined. Similarly, platelet activation as examined via surface expression of CD62P was not enhanced by eltrombopag pretreatment as compared to rhTPO. CONCLUSIONS: These results demonstrate that the nonpeptidyl TPOR agonist eltrombopag stimulates platelet signal transduction with little or no effect on overall platelet function, in contrast to TPO, which significantly primes platelet activation. These data demonstrate that effects of TPOR ligands on platelet function can vary depending on the specific mechanism utilized to stimulate the TPOR.

Differential gene expression of bone marrow-derived CD34+ cells is associated with survival of patients suffering from myelodysplastic syndrome.

One feature of the molecular pathology of myelodysplastic syndromes (MDS) is aberrant gene expression. Such aberrations may be related to patient survival, and may indicate to novel diagnostic and therapeutic targets. Therefore, we aimed at identifying aberrant gene expression that is associated with MDS and patient survival. Bone marrow-derived CD34+ hematopoietic progenitor cells from six healthy persons and 16 patients with MDS were analyzed on cDNA macroarrays comprising 1,185 genes. Thereafter, our patients were followed-up for 54 months. We found differential expression of genes that were hitherto unrecognized in the context of MDS. Differential expression of 10 genes was confirmed by quantitative real-time RT-PCR. Hierarchical cluster analysis facilitated the separation of CD34+ cells of normal donors from patients with MDS. More importantly, it also distinguished MDS-patients with short and long survival. Scrutinizing our cDNA macroarray data for genes that are associated with short survival, we found, among others, increased expression of six different genes that encode the proteasome subunits. On the other hand, the most differentially down-regulated gene was IEX-1, which encodes an anti-apoptotic protein. We confirmed its decreased expression on RNA and protein level in an independent validation set of patient samples. The presented data broadens our notion about the molecular pathology of MDS and may lend itself to better identify patients with short survival. Furthermore, our findings may help to define new molecular targets for drug development and therapeutic approaches for patients with poor prognosis.