The role of lenalidomide in the treatment of patients with chromosome 5q deletion and other myelodysplastic syndromes

Improved Side Effect Profile of Alternate-Day Dosing of Lenalidomide

Myelodysplastic syndrome (MDS) is a heterogeneous hematological condition associated with cytopenia, inadequate blood cell synthesis, and the risk of developing acute myeloid leukemia (AML). Patients are divided into risk groups according to the International Prognostic Scoring System (IPSS) to help direct therapy. Allogeneic stem cell transplantation, despite its limitations, is curative. Medical management, such as the use of lenalidomide, has potential benefits but can cause adverse effects that require dose regimen modification. Lenalidomide is approved for low-risk MDS with 5q deletion (5q- MDS). In this case study, a 79-year-old woman with 5q- MDS was switched from a daily regimen to an alternate-day lenalidomide dose schedule to achieve complete remission with fewer adverse effects. The management of hematological toxicity and the mechanisms of action of lenalidomide are discussed. We recommend individualized treatment strategies and additional research to improve MDS management.

Novel Molecular Mechanism of Lenalidomide in Myeloid Malignancies Independent of Deletion of Chromosome 5q

Lenalidomide as well as other immunomodulatory drugs (IMiDs) have achieved clinical efficacies in certain sub-types of hematologic malignancies, such as multiple myeloma, lower-risk myelodysplastic syndromes (MDS) with a single deletion of chromosome 5q (del(5q)) and others. Despite superior clinical response to lenalidomide in hematologic malignancies, relapse and resistance remains a problem in IMiD-based therapy. The last ten years have witnessed the discovery of novel molecular mechanism of IMiD-based anti-tumor therapy. IMiDs bind human cereblon (CRBN), the substrate receptor of the CRL4 E3 ubiquitin ligase complex. Binding of CRBN with IMiDs leads to degradation of the Ikaros family zinc finger proteins 1 and 3 (IKZF1 and IKZF3) and casein kinase 1 alpha. We have found that lenalidomide-mediated degradation of IKZF1 leads to activation of the G protein-coupled receptor 68 (GPR68)/calcium/calpain pro-apoptotic pathway and inhibition of the regulator of calcineurin 1 (RCAN1)/calcineurin pro-survival pathway in MDS and acute myeloid leukemia (AML). Calcineurin inhibitor Cyclosporin-A potentiates the anti-leukemia activity of lenalidomide in MDS/AML with or without del(5q). These findings broaden the therapeutic potential of IMiDs. This review summarizes novel molecular mechanism of lenalidomide in myeloid malignancies, especially without del(5q), in the hope to highlight novel therapeutic targets.

Loss of 5q in myeloid malignancies - A gain in understanding of biological and clinical consequences

Hemizygous interstitial or terminal deletion of the long arm of chromosome 5 [del(5q)] is a recurrent cytogenetic abnormality in myeloid malignancies, including myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). These deletions cause loss of a large contiguous chromosomal region encompassing more than 30 genes, which results in disease through haploinsufficiency of one or more genes including RPS14. In MDS, del(5q) in isolation is a lower-risk cytogenetic anomaly and is sometimes associated with a unique clinicopathological phenotype, but in AML it represents a higher-risk lesion, often denoting secondary AML arising from prior MDS. Lenalidomide effectively targets the del(5q)-bearing clone in MDS, resulting in sustained erythroid transfusion independence in most patients and cytogenetic remission in a subset of treated patients. Since the initial regulatory approval of lenalidomide for del(5q) MDS in 2005, translational research endeavors in del(5q)-associated myeloid malignancies have improved our understanding of how allelic haploinsufficiency underlies both the hematological phenotype and selective sensitivity to lenalidomide therapy. This review will focus on the molecular pathogenesis of del(5q) in myeloid malignancies, clinical development of lenalidomide and emerging data on lenalidomide-refractory del (5q) MDS, and possible novel targeted therapeutic strategies.

A Novel Drug, CC-122, Inhibits Tumor Growth in Hepatocellular Carcinoma through Downregulation of an Oncogenic TCF-4 Isoform

Immunomodulatory drugs such as lenalidomide (LEN) have shown significant anti-tumor activity against hematologic malignancies and they may have similar actions on solid tumors as well. We studied the effect of a new analog of the immunomodulatory drugs (CC-122) on the growth of hepatocellular carcinoma (HCC) and explored mechanisms of anti-tumor activity by analyzing expression of a novel oncogenic T-cell factor (TCF)-4 J and its downstream gene activation. LEN and CC-122 significantly reduced the expression levels of TCF-4 J and its target genes (SPP1, AXIN2, MMP7, ASPH, CD24, ANXA1, and CAMK2N1); however, CC-122 was more potent. In a xenograft tumor model with a HAK-1A-TCF-4 J derived stable cells, tumor growth was significantly inhibited by CC-122, but not by LEN or vehicle control. The mice with HCC xenograft tumors treated with CC-122 exhibited decreased TCF-4 J expression compared to LEN and control. Furthermore, expression of TCF-4 J-responsive target genes (SPP1, AXIN2, MMP7, ASPH, JAG1, CD24, ANXA1, and CAMK2N1) was reduced by CC-122 and not by LEN or control. These results suggest that CC-122 inhibits HCC tumor growth through downregulation of the oncogenic TCF-4 J isoform.

Treatment of Lymphoid and Myeloid Malignancies by Immunomodulatory Drugs

Thalidomide and its derivatives (lenalidomide, pomalidomide, avadomide, iberdomide hydrochoride, CC-885 and CC-90009) form the family of immunomodulatory drugs (IMiDs). Lenalidomide (CC5013, Revlimid®) was approved by the US FDA and the EMA for the treatment of multiple myeloma (MM) patients, low or intermediate-1 risk transfusion-dependent myelodysplastic syndrome (MDS) with chromosome 5q deletion [del(5q)] and relapsed and/or refractory mantle cell lymphoma following bortezomib. Lenalidomide has also been studied in clinical trials and has shown promising activity in chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma (NHL). Lenalidomide has anti-inflammatory effects and inhibits angiogenesis. Pomalidomide (CC4047, Imnovid® [EU], Pomalyst® [USA]) was approved for advanced MM insensitive to bortezomib and lenalidomide. Other IMiDs are in phases 1 and 2 of clinical trials. Cereblon (CRBN) seems to have an important role in IMiDs action in both lymphoid and myeloid hematological malignancies. Cereblon acts as the substrate receptor of a cullin-4 really interesting new gene (RING) E3 ubiquitin ligase CRL4CRBN. This E3 ubiquitin ligase in the absence of lenalidomide ubiquitinates CRBN itself and the other components of CRL4CRBN complex. Presence of lenalidomide changes specificity of CRL4CRBN which ubiquitinates two transcription factors, IKZF1 (Ikaros) and IKZF3 (Aiolos), and casein kinase 1α (CK1α) and marks them for degradation in proteasomes. Both these transcription factors (IKZF1 and IKZF3) stimulate proliferation of MM cells and inhibit T cells. Low CRBN level was connected with insensitivity of MM cells to lenalidomide. Lenalidomide decreases expression of protein argonaute-2, which binds to cereblon. Argonaute-2 seems to be an important drug target against IMiDs resistance in MM cells. Lenalidomide decreases also basigin and monocarboxylate transporter 1 in MM cells. MM cells with low expression of Ikaros, Aiolos and basigin are more sensitive to lenalidomide treatment. The CK1α gene (CSNK1A1) is located on 5q32 in commonly deleted region (CDR) in del(5q) MDS. Inhibition of CK1α sensitizes del(5q) MDS cells to lenalidomide. CK1α mediates also survival of malignant plasma cells in MM. Though, inhibition of CK1α is a potential novel therapy not only in del(5q) MDS but also in MM. High level of full length CRBN mRNA in mononuclear cells of bone marrow and of peripheral blood seems to be necessary for successful therapy of del(5q) MDS with lenalidomide. While transfusion independence (TI) after lenalidomide treatment is more than 60% in MDS patients with del(5q), only 25% TI and substantially shorter duration of response with occurrence of neutropenia and thrombocytopenia were achieved in lower risk MDS patients with normal karyotype treated with lenalidomide. Shortage of the biomarkers for lenalidomide response in these MDS patients is the main problem up to now.

Population Pharmacokinetics of Lenalidomide in Healthy Volunteers and Patients With Hematologic Malignancies

A population pharmacokinetic (PopPK) model of lenalidomide was developed using data pooled from 13 clinical studies (dose range, 5-400 mg) in participants who were considered to have adequate capability for renal excretion of lenalidomide (creatinine clearance [CrCl] > 50 mL/min). The analysis population included 305 healthy volunteers and 83 patients with multiple myeloma or myelodysplastic syndromes. A 1-compartment model with linear absorption and elimination described well the observed data for both healthy volunteers and patients. Covariate analysis suggested lenalidomide apparent clearance was positively correlated with CrCl, and lenalidomide volume of distribution was positively correlated with body weight. Both pharmacokinetic parameters were reduced by 29% in patients, independent of the effect of CrCl or body weight. Despite their statistical significance, effects of study population and body weight are considered clinically unimportant in adult patients with CrCl > 50 mL. After accounting for the above effects, body weight had no significant effect on CL/F, whereas age, sex, race, and mild hepatic impairment had no significant effect on either lenalidomide parameter. The PopPK model should be useful for future modeling of lenalidomide pharmacokinetics in the pediatric population and for further comparison of pharmacokinetic properties among structurally similar immunomodulatory drugs.

Molecular mechanisms of the progression of myelodysplastic syndrome to secondary acute myeloid leukaemia and implication for therapy

Myelodysplastic syndrome (MDS) includes a heterogeneous group of clonal haematological stem cell disorders characterized by dysplasia, cytopenias, ineffective haematopoiesis, and an increased risk of progression to acute myeloid leukaemia (AML), which is also called secondary AML (sAML). Approximately one-third of patients with MDS will progress to sAML within a few months to a few years, and this type of transformation is more common and rapid in patients with high-risk MDS (HR-MDS). However, the precise mechanisms underlying the evolution of MDS to sAML remain unclear. Currently, chemotherapy for sAML has minimal efficacy. The only method of curing patients with sAML is allogeneic haematopoietic stem cell transplantation (Allo-HSCT). Unfortunately, only a few patients are appropriate for transplantation because this disease primarily affects older adult patients. Additionally, compared to de novo AML, sAML is more difficult to cure, and the prognosis is often worse. Therefore, it is important to clarify the molecular mechanisms of the progression of MDS to sAML and to explore the potent drugs for clinical use. This review will highlight several molecular mechanisms of the progression of MDS to sAML and new therapeutic strategies of this disease.

Risk of secondary primary malignancies in maintenance therapy for multiple myeloma

SUMMARY There have been many advances in the treatment of patients with multiple myeloma over the past decade. As a result, the average life expectancy of patients with MM has improved. New medications, including immunomodulatory drugs (thalidomide, lenalidomide and pomalidomide) and proteasome inhibitors (bortezomib and carfilzomib) have entered clinical practice. On average, these medications are easier to tolerate than traditional chemotherapy allowing for long-term use of these drugs in a maintenance fashion. Clinical trials have appeared to establish the benefit of lower dose maintenance therapy for MM patients after induction chemotherapy and/or autologous stem cell transplant. These medications have been shown to improve not only the progression-free survival of patients, but also improve their overall survival compared with observation alone in some pivotal studies. With long-term maintenance therapy, a notable increase in secondary primary malignancies has been described. The exact mechanism behind this increase is uncertain, but may relate to the persistence of CD34+ cells in the setting of continued immunomodulatory exposure. Despite the concern of secondary primary malignancies, the risk:benefit ratio still favors maintenance therapy in many patients with multiple myeloma.

Alterations in the ribosomal machinery in cancer and hematologic disorders

Ribosomes are essential components of the protein translation machinery and are composed of more than 80 unique large and small ribosomal proteins. Recent studies show that in addition to their roles in protein translation, ribosomal proteins are also involved in extra-ribosomal functions of DNA repair, apoptosis and cellular homeostasis. Consequently, alterations in the synthesis or functioning of ribosomal proteins can lead to various hematologic disorders. These include congenital anemias such as Diamond Blackfan anemia and Shwachman Diamond syndrome; both of which are associated with mutations in various ribosomal genes. Acquired uniallelic deletion of RPS14 gene has also been shown to lead to the 5q syndrome, a distinct subset of MDS associated with macrocytic anemia. Recent evidence shows that specific ribosomal proteins are overexpressed in liver, colon, prostate and other tumors. Ribosomal protein overexpression can promote tumorigenesis by interactions with the p53 tumor suppressor pathway and also by direct effects on various oncogenes. These data point to a broad role of ribosome protein alterations in hematologic and oncologic diseases.

Important genes in the pathogenesis of 5q- syndrome and their connection with ribosomal stress and the innate immune system pathway

Myelodysplastic syndrome (MDS) with interstitial deletion of a segment of the long arm of chromosome 5q [del(5q)] is characterized by bone marrow erythroid hyperplasia, atypical megakaryocytes, thrombocythemia, refractory anemia, and low risk of progression to acute myeloid leukemia (AML) compared with other types of MDS. The long arm of chromosome 5 contains two distinct commonly deleted regions (CDRs). The more distal CDR lies in 5q33.1 and contains 40 protein-coding genes and genes coding microRNAs (miR-143, miR-145). In 5q-syndrome one allele is deleted that accounts for haploinsufficiency of these genes. The mechanism of erythroid failure appears to involve the decreased expression of the ribosomal protein S14 (RPS14) gene and the upregulation of the p53 pathway by ribosomal stress. Friend leukemia virus integration 1 (Fli1) is one of the target genes of miR145. Increased Fli1 expression enables effective megakaryopoiesis in 5q-syndrome.

Pharmacokinetics, metabolism and excretion of [(14)C]-lenalidomide following oral administration in healthy male subjects

Purpose

Assessment of the absorption, metabolism and excretion of [¹⁴C]-lenalidomide in healthy male subjects following a single oral dose.

Methods

Six healthy male subjects were administered a single 25 mg oral suspension dose of [¹⁴C]-lenalidomide. Blood (plasma), semen and excreta were collected. Mass balance assessments were done by radioactivity measurements. Metabolite profiling and quantitation were accomplished using liquid chromatography with mass spectrometric and radiochemical detection.

Results

[¹⁴C]-Lenalidomide was rapidly absorbed (T_max 0.77–1.0 h), and the levels declined with a terminal half-life of approximately 3 h, with similar profiles for total blood and plasma radioactivity as well as plasma lenalidomide. The whole blood to plasma radioactivity exposure levels were comparable, suggesting equal distribution between plasma and blood cells. On average, 94% of the administered radioactivity was recovered within 10 days, with >88% recovered within 24 h. Urinary excretion was the primary route of elimination (90% of radioactive dose), with minor amounts excreted in feces (4%). Semen contained a small amount of the radioactive dose (0.0062%). Lenalidomide was the primary radioactive component in plasma (92% of the [¹⁴C]-area under the concentration–time curve) and urine (>90% of the radioactivity in urine). The remaining radioactivity was composed of primarily two metabolites: 5-hydroxy-lenalidomide and N-acetyl-lenalidomide, each accounting for less than 5% of the total radioactivity as well as lenalidomide levels in plasma and excreta.

Conclusions

In summary, following oral administration, lenalidomide is highly absorbed and bioavailable, metabolized minimally, and eliminated predominantly via urinary excretion in the unchanged form in humans.

TP53 mutations in low-risk myelodysplastic syndromes with del(5q) predict disease progression

PURPOSE

To determine the frequency of TP53 mutations and the level of p53 protein expression by immunohistochemistry (IHC) in low-risk myelodysplastic syndromes (MDS) with del(5q) and to assess their impact on disease progression.

PATIENTS AND METHODS

Pre- and postprogression bone marrow (BM) samples from 55 consecutive patients with International Prognostic Scoring System low risk (n = 32) or intermediate-1 risk (n = 23) were studied by next-generation sequencing of TP53. IHC for p53 was performed on 148 sequential BM samples.

RESULTS

TP53 mutations with a median clone size of 11% (range, 1% to 54%) were detected in 10 patients (18%) already at an early phase of the disease. Mutations were equally common in low-risk and intermediate-1-risk patients and were associated with evolution to acute myeloid leukemia (5 of 10 v 7 of 45; P = .045). Nine of 10 patients carrying mutations showed more than 2% BM progenitors with strong p53 staining. The probability of a complete cytogenetic response to lenalidomide was lower in mutated patients (0 of 7 v 12 of 24; P = .024).

CONCLUSION

By using sensitive deep-sequencing technology, we demonstrated that TP53 mutated populations may occur at an early disease stage in almost a fifth of low-risk MDS patients with del(5q). Importantly, mutations were present years before disease progression and were associated with an increased risk of leukemic evolution. TP53 mutations could not be predicted by common clinical features but were associated with p53 overexpression. Our findings indicate a previously unrecognized heterogeneity of the disease which may significantly affect clinical decision making.

Immunosuppressive therapy for myelodysplastic syndromes: refining the indications

Myelodysplastic syndromes (MDS) are often associated with autoimmune processes that contribute to the cytopenias that characterize this disease group. Ten years ago, several investigators described improvement in the cytopenia of MDS following immunosuppressive treatments (IST) with antithymocyte globulin or cyclosporine. These findings have since been widely confirmed. The consensus is that about 30% of unselected transfusion-dependent patients with MDS given IST have sustained hematologic responses and can regain transfusion independence. Over the past decade, prognostic features have been defined that accurately identify the subset of patients most likely to benefit from IST. With increasing knowledge about the pathophysiology of myelosuppression in MDS, we are beginning to define the immunosuppressive agents and schedules with the greatest chance of causing hematologic improvement. Significantly, long-term follow-up indicates that IST responders have a better progression-free survival than comparable patients with MDS who do not receive IST.

Characterization of chromosome arm 20q abnormalities in myeloid malignancies using genome-wide single nucleotide polymorphism array analysis

Deletion of the long arm of chromosome 20 is a common abnormality associated with myeloid malignancies. We characterized abnormalities of chromosome 20 as defined by metaphase cytogenetics (MC) in patients with myeloid neoplasms to define commonly deleted regions (CDR) and commonly retained regions (CRR) using genome-wide, high resolution single nucleotide polymorphism array (SNP-A) analysis. We reviewed the MC results of a cohort of 1,162 patients with myeloid malignancies, including myelodysplastic syndromes (MDS), MDS/myeloproliferative neoplasia (MDS/MPN), and acute myeloid leukemia (AML). We further analyzed a subcohort of 532 patients by SNP-A using the Affymetrix Genome-Wide Human SNP Array 6.0 and GeneChip Human Mapping 250K Nsp arrays. By MC, 5% (54/1,162) harbored a deletion of 20q; in 30% (16/54), del(20q) was the sole cytogenetic abnormality. By SNP-A analysis, we identified del(20q) in 23 patients, 3 not detected by MC. In four cases, monosomy 20 with a marker chromosome by MC was proven to be an interstitial deletion of 20q by SNP-A. We defined 2 CDR and 2 CRR on chromosome arm 20q: CDR1 spanned 2.5 Mb between bands 20q11.23 and 20q12, while CDR2 encompassed 1.8 Mb within 20q13.12. CRR1 spanned 1.9 Mb within 20q11.21 and CRR2 encompassed 2.5 Mb within 20q13.33. In contrast to other chromosomes frequently affected by deletions, no somatic copy neutral loss of heterozygosity (CN-LOH) was detected. Our data suggest that SNP-A is useful for the detection of cryptic aberrations of chromosome 20q and allows for a more precise characterization of complex karyotypes. Furthermore, SNP-A allowed definition of a CDR on 20q.

Effect of lenalidomide therapy on hematopoiesis of patients with myelodysplastic syndrome associated with chromosome 5q deletion

BACKGROUND

Lenalidomide improves erythropoiesis in patients with low/intermediate-1 risk myelodysplastic syndrome and interstitial deletion of the long arm of chromosome 5 [del(5q)]. The aim of this study was to explore the effect of lenalidomide treatment on the reserves and functional characteristics of bone marrow hematopoietic progenitor/precursor cells, bone marrow stromal cells and peripheral blood lymphocytes in patients with low/intermediate-1 risk myelodysplastic syndrome with del(5q).

DESIGN AND METHODS

We evaluated the number and clonogenic potential of bone marrow erythroid/myeloid/megakaryocytic progenitor cells using clonogenic assays, the apoptotic characteristics and adhesion molecule expression of CD34(+) cells by flow cytometry, the hematopoiesis-supporting capacity of bone marrow stromal cells using long-term bone marrow cultures and the number and activation status of peripheral blood lymphocytes in ten patients with low/intermediate-1 risk myelodysplastic syndrome with del(5q) receiving lenalidomide.

RESULTS

Compared to baseline, lenalidomide treatment significantly decreased the proportion of bone marrow CD34+ cells, increased the proportion of CD36(+)/GlycoA(+) and CD36(-)/GlycoA(+) erythroid cells and the percentage of apoptotic cells within these cell compartments. Treatment significantly improved the clonogenic potential of bone marrow erythroid, myeloid, megakaryocytic colony-forming cells and increased the proportion of CD34(+) cells expressing the adhesion molecules CD11a, CD49d, CD54, CXCR4 and the SLAM antigen CD48. The hematopoiesis-supporting capacity of bone marrow stroma improved significantly following treatment, as demonstrated by the number of colony-forming cells and the level of stromal-derived factor-1 alpha and intercellular adhesion molecule-1 in long-term bone marrow culture supernatants. Lenalidomide treatment also increased the proportion of activated peripheral blood T lymphocytes.

CONCLUSIONS

The beneficial effect of lenalidomide in patients with lower risk myelodysplastic syndrome with del(5q) is associated with significant increases in the proportion of bone marrow erythroid precursor cells and in the frequency of clonogenic progenitor cells, a substantial improvement in the hematopoiesis-supporting potential of bone marrow stroma and significant alterations in the adhesion profile of bone marrow CD34(+) cells.

Inhibition of metastatic potential in colorectal carcinoma in vivo and in vitro using immunomodulatory drugs (IMiDs)

BACKGROUND

Thalidomide and lenalidomide are FDA approved for the treatment of multiple myeloma and, along with pomalidomide, are being investigated in various other cancers. Although these agents display immunomodulatory, anti-angiogenic and anti-apoptotic effects, little is known about their primary mode of therapeutic action in patients with cancer.

METHODS

As part of a continuing research effort, we have investigated the effects of these agents on the metastatic capacity of murine colorectal cancer cell lines both in vivo and in vitro. Allied to these, we have studied their effects on the molecular pathways associated with metastasis.

RESULTS

Results indicate that thalidomide, lenalidomide and pomalidomide significantly inhibit the metastatic capability of colorectal carcinoma cells. Anchorage-independent growth, used as a coarse indicator of transformation, was significantly reduced, as were migratory capacity and invasive competence. In addition, an in vivo experimental metastasis model also showed that treatment with the drugs resulted in a significantly lower number of metastatic pulmonary nodules relative to control mice. Allied to these cellular and phenotypic changes were alterations in molecular markers of metastasis and in intracellular signalling competency.

CONCLUSIONS

These results provide evidence that in addition to their immunomodulatory effects, thalidomide, lenalidomide and pomalidomide can impair the metastatic capacity of tumours, and that this mechanism may involve alterations to cell signalling functionality.

Venous thromboembolism in myelodysplastic syndrome patients receiving lenalidomide: results from postmarketing surveillance and data mining techniques

BACKGROUND AND OBJECTIVES

Multiple myeloma treatment with lenalidomide-based regimens is associated with risk of venous thromboembolism (VTE), particularly during concomitant use with erythropoiesis-stimulating agents (ESAs). The risk of VTE in myelodysplastic syndrome (MDS) patients treated with lenalidomide is not well characterized and the background risk in untreated patients is not known. This study set out to determine the reporting rate of VTE in MDS patients on lenalidomide in the two years of postmarketing experience in the US, and to investigate whether there is a disproportional signal of VTE in MDS patients on lenalidomide by screening the US FDA Adverse Event Reporting System (AERS) safety database.

METHODS

The MDS population exposed to lenalidomide was obtained from RevAssist, the company's proprietary restrictive distribution programme. VTE reports were identified from the company's postmarketing surveillance safety database. The FDA AERS database was used for disproportionality analysis, and signal scores computed using three algorithms: multi-item gamma Poisson shrinker (MGPS), proportional reporting ratio (PRR), and reporting odds ratios (ROR).

RESULTS

A total of 7764 MDS patients were prescribed lenalidomide during the first two years of commercial use in the US. VTE representing deep vein thrombosis and pulmonary embolism was reported in 41 patients, a reporting rate of 0.53%. The computed signal scores did not exceed the statistical threshold for identification of a significant disproportional signal for VTE in MDS reports involving use of lenalidomide without concomitant use of ESAs. However, a disproportional signal of VTE was detected in MDS reports where lenalidomide was concurrently used with ESAs.

CONCLUSION

The VTE reporting rate for MDS patients receiving lenalidomide during the first two years of postmarketing exposure was low (0.53%). Disproportionality analysis demonstrated a statistically meaningful association of VTE with lenalidomide concomitantly used with ESAs in MDS patients, but the association was not statistically significant when lenalidomide was used in the absence of ESAs.

Myelodysplastic syndromes: diagnosis and staging

Myelodysplastic syndromes (MDS) represent a heterogeneous group of hematologic disorders characterized by ineffective hematopoiesis and an increased risk of developing acute myelogenous leukemia (AML). Accurate diagnosis of MDS can be difficult, and its classification requires evaluation of cytopenias, bone marrow morphology, blast percentage, and cytogenetics. These factors, as well as patient performance status and red blood cell transfusion dependence, can be used to predict prognosis in MDS. Accurate diagnosis and classification are essential for subgroup identification and prognostic assessment of patients with MDS. This article reviews essential criteria for staging and subgroup classification and summarizes prognostic scoring systems that aid in risk stratification and selection of optimal therapy. Classification systems such as the World Health Organization (WHO) classification are widely used but do not always provide sufficient prognostic information. This limitation led to the creation of the International Prognostic Scoring System (IPSS). However, this system was designed to be used only at diagnosis and may not be suitable for serial assessment of patients whose disease can evolve over time. The WHO classification-based prognostic scoring system (WPSS) permits dynamic estimation of survival and risk of AML transformation at multiple time points during the natural course of MDS. Prognostic scoring systems such as WPSS allow for prediction of survival and risk of leukemic evolution at any time during the course of the disease. Such an approach may provide a useful adjunct for clinical decision making, including selection of appropriate treatment options.

Lenalidomide: in vitro evaluation of the metabolism and assessment of cytochrome P450 inhibition and induction

PURPOSE

To assess the potential for drug-drug interactions between lenalidomide and substrates and inhibitors of cytochrome P450 (CYP) isozymes.

METHODS

In vitro metabolism of lenalidomide by human liver microsomes, recombinant human CYPs and human hepatocytes was evaluated. The inhibitory and inductive effects of lenalidomide on the CYP activities were evaluated in human liver microsomes and cultured human hepatocytes, respectively.

RESULTS

In vitro incubation of lenalidomide with human liver microsomes, recombinant-CYP isozymes, and human hepatocytes did not result in Phase I or Phase II metabolism, confirming the low propensity of lenalidomide for metabolism in vivo in humans. In vitro, lenalidomide did not inhibit CYP isozymes in human liver microsomes and did not induce CYP activities in cultured human hepatocytes.

CONCLUSIONS

Lenalidomide is not a substrate, inhibitor, or inducer of CYP group of enzymes; clinically relevant pharmacokinetic drug-drug interactions are unlikely to occur between lenalidomide and co-administered CYP substrates or inhibitors.

Allogeneic stem cell transplantation for myelodysplastic syndrome

Although it is only used to treat a minority of patients with myelodysplastic syndromes, stem cell transplantation (SCT) is the only proven curative treatment for this condition. Because MDS occurs in a population of older adults with significant comorbidities, reduced-intensity conditioning (RIC) regimens have been particularly important in extending safe SCT to the large MDS population over the age of 60 years. Extension of the unrelated donor pool together with the introduction of umbilical cord blood transplants in adults has extended the number of patients with suitable donors. Nevertheless overall mortality from SCT is greater than 50% because of relapse and non-relapse mortality (NRM). New developments to improve outcome include the tailoring of the transplant approach to the individual based on age and comorbidity, and the use of pretransplant chemotherapy to reduce disease bulk prior to transplant, as well as the introduction of post-transplant immunotherapy (pre-emptive donor lymphocyte infusions) and chemotherapy to prevent relapse. Further improvements in transplant outcome await better ways to reconstitute immunity and amplify the graft-versus-leukemia (GVL) effect without causing graft-versus-host disease (GVHD), as well as further extension of the donor pool and exploration of risk-adapted regimens for the population of MDS in their seventh to eighth decade.