Enhancer trap lines with GFP driven by smad6b and frizzled1 regulatory sequences for the study of epithelial morphogenesis in the developing zebrafish inner ear.

Live imaging in the zebrafish embryo using tissue-specific expression of fluorescent proteins can yield important insights into the mechanisms that drive sensory organ morphogenesis and cell differentiation. Morphogenesis of the semicircular canal ducts of the vertebrate inner ear requires a complex rearrangement of epithelial cells, including outgrowth, adhesion, fusion and perforation of epithelial projections to generate pillars of tissue that form the hubs of each canal. We report the insertion sites and expression patterns of two enhancer trap lines in the developing zebrafish embryo, each of which highlight different aspects of epithelial cell morphogenesis in the inner ear. A membrane-linked EGFP driven by smad6b regulatory sequences is expressed throughout the otic epithelium, most strongly on the lateral side of the ear and in the sensory cristae. A second enhancer trap line, with cytoplasmic EGFP driven by frizzled1 (fzd1) regulatory sequences, specifically marks cells of the ventral projection and pillar in the developing ear, and marginal cells in the sensory cristae, together with variable expression in the retina and epiphysis, and neurons elsewhere in the developing central nervous system. We have used a combination of methods to identify the insertion sites of these two transgenes, which were generated through random insertion, and show that Targeted Locus Amplification is a rapid and reliable method for the identification of insertion sites of randomly inserted transgenes.

Myofiber stretch induces tensile and shear deformation of muscle stem cells in their native niche.

Muscle stem cells (MuSCs) are requisite for skeletal muscle regeneration and homeostasis. Proper functioning of MuSCs, including activation, proliferation, and fate decision, is determined by an orchestrated series of events and communication between MuSCs and their niche. A multitude of biochemical stimuli are known to regulate MuSC fate and function. However, in addition to biochemical factors, it is conceivable that MuSCs are subjected to mechanical forces during muscle stretch-shortening cycles because of myofascial connections between MuSCs and myofibers. MuSCs respond to mechanical forces in vitro, but it remains to be proven whether physical forces are also exerted on MuSCs in their native niche and whether they contribute to the functioning and fate of MuSCs. MuSC deformation in their native niche resulting from mechanical loading of ex vivo myofiber bundles was visualized utilizing mT/mG double-fluorescent Cre-reporter mouse and multiphoton microscopy. MuSCs were subjected to 1 h pulsating fluid shear stress (PFSS) with a peak shear stress rate of 6.5 Pa/s. After PFSS treatment, nitric oxide, messenger RNA (mRNA) expression levels of genes involved in regulation of MuSC proliferation and differentiation, ERK 1/2, p38, and AKT activation were determined. Ex vivo stretching of extensor digitorum longus and soleus myofiber bundles caused compression as well as tensile and shear deformation of MuSCs in their niche. MuSCs responded to PFSS in vitro with increased nitric oxide production and an upward trend in iNOS mRNA levels. PFSS enhanced gene expression of c-Fos, Cdk4, and IL-6, whereas expression of Wnt1, MyoD, Myog, Wnt5a, COX2, Rspo1, Vangl2, Wnt10b, and MGF remained unchanged. ERK 1/2 and p38 MAPK signaling were also upregulated after PFSS treatment. We conclude that MuSCs in their native niche are subjected to force-induced deformations due to myofiber stretch-shortening. Moreover, MuSCs are mechanoresponsive, as evidenced by PFSS-mediated expression of factors by MuSCs known to promote proliferation.

Enasidenib in mutant IDH2 relapsed or refractory acute myeloid leukemia.

Recurrent mutations in isocitrate dehydrogenase 2 (IDH2) occur in ∼12% of patients with acute myeloid leukemia (AML). Mutated IDH2 proteins neomorphically synthesize 2-hydroxyglutarate resulting in DNA and histone hypermethylation, which leads to blocked cellular differentiation. Enasidenib (AG-221/CC-90007) is a first-in-class, oral, selective inhibitor of mutant-IDH2 enzymes. This first-in-human phase 1/2 study assessed the maximum tolerated dose (MTD), pharmacokinetic and pharmacodynamic profiles, safety, and clinical activity of enasidenib in patients with mutant-IDH2 advanced myeloid malignancies. We assessed safety outcomes for all patients and clinical efficacy in the largest patient subgroup, those with relapsed or refractory AML, from the phase 1 dose-escalation and expansion phases of the study. In the dose-escalation phase, an MTD was not reached at doses ranging from 50 to 650 mg per day. Enasidenib 100 mg once daily was selected for the expansion phase on the basis of pharmacokinetic and pharmacodynamic profiles and demonstrated efficacy. Grade 3 to 4 enasidenib-related adverse events included indirect hyperbilirubinemia (12%) and IDH-inhibitor-associated differentiation syndrome (7%). Among patients with relapsed or refractory AML, overall response rate was 40.3%, with a median response duration of 5.8 months. Responses were associated with cellular differentiation and maturation, typically without evidence of aplasia. Median overall survival among relapsed/refractory patients was 9.3 months, and for the 34 patients (19.3%) who attained complete remission, overall survival was 19.7 months. Continuous daily enasidenib treatment was generally well tolerated and induced hematologic responses in patients for whom prior AML therapy had failed. Inducing differentiation of myeloblasts, not cytotoxicity, seems to drive the clinical efficacy of enasidenib. This trial was registered at www.clinicaltrials.gov as #NCT01915498.

Myotome adaptability confers developmental robustness to somitic myogenesis in response to fibre number alteration.

Balancing the number of stem cells and their progeny is crucial for tissue development and repair. Here we examine how cell numbers and overall muscle size are tightly regulated during zebrafish somitic muscle development. Muscle stem/precursor cell (MPCs) expressing Pax7 are initially located in the dermomyotome (DM) external cell layer, adopt a highly stereotypical distribution and thereafter a proportion of MPCs migrate into the myotome. Regional variations in the proliferation and terminal differentiation of MPCs contribute to growth of the myotome. To probe the robustness of muscle size control and spatiotemporal regulation of MPCs, we compared the behaviour of wild type (wt) MPCs with those in mutant zebrafish that lack the muscle regulatory factor Myod. Myodfh261 mutants form one third fewer multinucleate fast muscle fibres than wt and show a significant expansion of the Pax7+ MPC population in the DM. Subsequently, myodfh261 mutant fibres generate more cytoplasm per nucleus, leading to recovery of muscle bulk. In addition, relative to wt siblings, there is an increased number of MPCs in myodfh261 mutants and these migrate prematurely into the myotome, differentiate and contribute to the hypertrophy of existing fibres. Thus, homeostatic reduction of the excess MPCs returns their number to normal levels, but fibre numbers remain low. The GSK3 antagonist BIO prevents MPC migration into the deep myotome, suggesting that canonical Wnt pathway activation maintains the DM in zebrafish, as in amniotes. BIO does not, however, block recovery of the myodfh261 mutant myotome, indicating that homeostasis acts on fibre intrinsic growth to maintain muscle bulk. The findings suggest the existence of a critical window for early fast fibre formation followed by a period in which homeostatic mechanisms regulate myotome growth by controlling fibre size. The feedback controls we reveal in muscle help explain the extremely precise grading of myotome size along the body axis irrespective of fish size, nutrition and genetic variation and may form a paradigm for wider matching of organ size.

Functional in vivo imaging using fluorescence lifetime light-sheet microscopy.

Light-sheet microscopy has become an indispensable tool for fast, low phototoxicity volumetric imaging of biological samples, predominantly providing structural or analyte concentration data in its standard format. Fluorescence lifetime imaging microscopy (FLIM) provides functional contrast, but often at limited acquisition speeds and with complex implementation. Therefore, we incorporate a dedicated frequency domain CMOS FLIM camera and intensity-modulated laser into a light-sheet setup to add fluorescence lifetime imaging functionality, allowing the rapid acquisition of volumetric data with concentration independent contrast. We then apply the system to image live transgenic zebrafish, demonstrating the capacity to rapidly collect volumetric FLIM data from an in vivo sample.

Ret signalling integrates a craniofacial muscle module during development.

An appropriate organisation of muscles is crucial for their function, yet it is not known how functionally related muscles are coordinated with each other during development. In this study, we show that the development of a subset of functionally related head muscles in the zebrafish is regulated by Ret tyrosine kinase signalling. Three genes in the Ret pathway (gfra3, artemin2 and ret) are required specifically for the development of muscles attaching to the opercular bone (gill cover), but not other adjacent muscles. In animals lacking Ret or Gfra3 function, myogenic gene expression is reduced in forming opercular muscles, but not in non-opercular muscles derived from the same muscle anlagen. These animals have a normal skeleton with small or missing opercular muscles and tightly closed mouths. Myogenic defects correlate with a highly restricted expression of artn2, gfra3 and ret in mesenchymal cells in and around the forming opercular muscles. ret(+) cells become restricted to the forming opercular muscles and a loss of Ret signalling results in reductions of only these, but not adjacent, muscles, revealing a specific role of Ret in a subset of head muscles. We propose that Ret signalling regulates myogenesis in head muscles in a modular manner and that this is achieved by restricting Ret function to a subset of muscle precursors.

Development of a doubly weighted Gerchberg-Saxton algorithm for use in multibeam imaging applications.

We report on the development of a doubly weighted Gerchberg-Saxton algorithm (DWGS) to enable generation of uniform beamlet arrays with a spatial light modulator (SLM) for use in multiphoton multifocal imaging applications. The algorithm incorporates the WGS algorithm as well as feedback of fluorescence signals from the sample measured with a single-photon avalanche diode (SPAD) detector array. This technique compensates for issues associated with nonuniform illumination onto the SLM, the effects due to aberrations and the variability in gain between detectors within the SPAD array to generate a uniformly illuminated multiphoton fluorescence image. We demonstrate the use of the DWGS with a number of beamlet array patterns to image muscle fibers of a 5-day-old fixed zebrafish larvae.

Skeletal Muscle Regeneration in Zebrafish.

Muscle regeneration models have revealed mechanisms of inflammation, wound clearance, and stem cell-directed repair of damage, thereby informing therapy. Whereas studies of muscle repair are most advanced in rodents, the zebrafish is emerging as an additional model organism with genetic and optical advantages. Various muscle wounding protocols (both chemical and physical) have been published. Here we describe simple, cheap, precise, adaptable, and effective wounding protocols and analysis methods for two stages of a larval zebrafish skeletal muscle regeneration model. We show examples of how muscle damage, ingression of muscle stem cells, immune cells, and regeneration of fibers can be monitored over an extended timecourse in individual larvae. Such analyses have the potential to greatly enhance understanding, by reducing the need to average regeneration responses across individuals subjected to an unavoidably variable wound stimulus.

Migration and differentiation of muscle stem cells are coupled by RhoA signalling during regeneration.

Skeletal muscle is highly regenerative and is mediated by a population of migratory adult muscle stem cells (muSCs). Effective muscle regeneration requires a spatio-temporally regulated response of the muSC population to generate sufficient muscle progenitor cells that then differentiate at the appropriate time. The relationship between muSC migration and cell fate is poorly understood and it is not clear how forces experienced by migrating cells affect cell behaviour. We have used zebrafish to understand the relationship between muSC cell adhesion, behaviour and fate in vivo. Imaging of pax7-expressing muSCs as they respond to focal injuries in trunk muscle reveals that they migrate by protrusive-based means. By carefully characterizing their behaviour in response to injury we find that they employ an adhesion-dependent mode of migration that is regulated by the RhoA kinase ROCK. Impaired ROCK activity results in reduced expression of cell cycle genes and increased differentiation in regenerating muscle. This correlates with changes to focal adhesion dynamics and migration, revealing that ROCK inhibition alters the interaction of muSCs to their local environment. We propose that muSC migration and differentiation are coupled processes that respond to changes in force from the environment mediated by RhoA signalling.

Notch Signaling Regulates Muscle Stem Cell Homeostasis and Regeneration in a Teleost Fish.

Muscle regeneration is mediated by the activity of resident muscle satellite cells (muSCs) that express Pax7. In mouse Notch signaling regulates muSCs during quiescence and promotes muSC proliferation in regeneration. It is unclear if these roles of Notch in regulating muSC biology are conserved across vertebrates or are a mammalian specific feature. We have therefore investigated the role of Notch in regulating muSC homeostasis and regeneration in a teleost fish, the zebrafish. We have also tested whether muSCs show differential sensitivity to Notch during myotome development. In an absence of injury Notch is important for preventing muSC proliferation at the vertical myoseptum. In contrast, Notch signaling promotes proliferation and prevents differentiation in the context of injury. Notch is required for the proliferative response to injury at early and later larval stages, suggesting it plays a similar role in regulating muSCs at developing and adult stages. Our results reveal a conserved role for Notch signaling in regulating muSCs under homeostasis and for promoting proliferation during regeneration in teleost fish.

Lenalidomide plus dexamethasone for relapsed or refractory multiple myeloma.

BACKGROUND: Lenalidomide is a structural analogue of thalidomide with similar but more potent biologic activity. This phase 3, placebo-controlled trial investigated the efficacy of lenalidomide plus dexamethasone in the treatment of relapsed or refractory multiple myeloma. METHODS: Of 351 patients who had received at least one previous antimyeloma therapy, 176 were randomly assigned to receive 25 mg of oral lenalidomide and 175 to receive placebo on days 1 to 21 of a 28-day cycle. In addition, all patients received 40 mg of oral dexamethasone on days 1 to 4, 9 to 12, and 17 to 20 for the first four cycles and subsequently, after the fourth cycle, only on days 1 to 4. Patients continued in the study until the occurrence of disease progression or unacceptable toxic effects. The primary end point was time to progression. RESULTS: The time to progression was significantly longer in the patients who received lenalidomide plus dexamethasone (lenalidomide group) than in those who received placebo plus dexamethasone (placebo group) (median, 11.3 months vs. 4.7 months; P<0.001). A complete or partial response occurred in 106 patients in the lenalidomide group (60.2%) and in 42 patients in the placebo group (24.0%, P<0.001), with a complete response in 15.9% and 3.4% of patients, respectively (P<0.001). Overall survival was significantly improved in the lenalidomide group (hazard ratio for death, 0.66; P=0.03). Grade 3 or 4 adverse events that occurred in more than 10% of patients in the lenalidomide group were neutropenia (29.5%, vs. 2.3% in the placebo group), thrombocytopenia (11.4% vs. 5.7%), and venous thromboembolism (11.4% vs. 4.6%). CONCLUSIONS: Lenalidomide plus dexamethasone is more effective than high-dose dexamethasone alone in relapsed or refractory multiple myeloma. (ClinicalTrials.gov number, NCT00424047 [ClinicalTrials.gov].).

Lenalidomide plus dexamethasone for relapsed multiple myeloma in North America.

BACKGROUND: Lenalidomide, an oral immunomodulatory drug that is similar to thalidomide but has a different safety profile, has clinical activity in relapsed or refractory multiple myeloma. METHODS: Patients in the United States and Canada who had received at least one previous therapy for multiple myeloma but who required additional treatment were randomly assigned to receive either 25 mg of lenalidomide or placebo on days 1 to 21 of a 28-day cycle. Both groups also received 40 mg of oral dexamethasone on days 1 to 4, 9 to 12, and 17 to 20 for the first four cycles. After the fourth cycle, 40 mg of dexamethasone was administered only on days 1 to 4. Safety, clinical response, time to progression, and overall survival were assessed. RESULTS: We assigned 177 patients to the lenalidomide group and 176 to the placebo group. Complete, near-complete, or partial responses occurred in 108 patients (61.0%) in the lenalidomide group and in 35 patients (19.9%) in the placebo group (P<0.001); complete responses occurred in 14.1% and 0.6%, respectively (P<0.001). The median time to progression was 11.1 months in the lenalidomide group and 4.7 months in the placebo group (P<0.001). Median overall survival times in the two groups were 29.6 months and 20.2 months, respectively (P<0.001). Grade 3 or 4 adverse events were reported in 85.3% of the lenalidomide group and in 73.1% of the placebo group; these events resulted in study discontinuation in 19.8% and 10.2%, respectively. Grade 3 or 4 neutropenia and venous thromboembolism were more common in the lenalidomide group than in the placebo group (41.2% vs. 4.6% and 14.7% vs. 3.4%, respectively; P<0.001 for both comparisons). CONCLUSIONS: Lenalidomide plus dexamethasone is superior to placebo plus dexamethasone in patients with relapsed or refractory multiple myeloma. (ClinicalTrials.gov number, NCT00056160 [ClinicalTrials.gov].).

Lenalidomide plus dexamethasone is more effective than dexamethasone alone in patients with relapsed or refractory multiple myeloma regardless of prior thalidomide exposure.

This analysis assessed the efficacy and safety of lenalidomide + dexamethasone in patients with relapsed or refractory multiple myeloma (MM) previously treated with thalidomide. Of 704 patients, 39% were thalidomide exposed. Thalidomide-exposed patients had more prior lines of therapy and longer duration of myeloma than thalidomide-naive patients. Lenalidomide + dexamethasone led to higher overall response rate (ORR), longer time to progression (TTP), and progression-free survival (PFS) versus placebo + dexamethasone despite prior thalidomide exposure. Among lenalidomide + dexamethasone-treated patients, ORR was higher in thalidomide-naive versus thalidomide-exposed patients (P = .04), with longer median TTP (P = .04) and PFS (P = .02). Likewise for dexamethasone alone-treated patients (P = .03 for ORR, P = .03 for TTP, P = .06 for PFS). Prior thalidomide did not affect survival in lenalidomide + dexamethasone-treated patients (36.1 vs 33.3 months, P > .05). Thalidomide-naive and thalidomide-exposed patients had similar toxicities. Lenalidomide + dexamethasone resulted in higher rates of venous thromboembolism, myelosuppression, and infections versus placebo + dexamethasone, independent of prior thalidomide exposure. Lenalido-mide + dexamethasone was superior to placebo + dexamethasone, independent of prior thalidomide exposure. Although prior thalidomide may have contributed to inferior TTP and PFS compared with thalidomide-naive patients, these parameters remained superior compared with placebo + dexamethasone; similar benefits compared with placebo + dexamethasone were not evident for thalidomide-exposed patients in terms of overall survival. Studies were registered at http://www.clinicaltrials.gov under NCT00056160 and NCT00424047.

Better quality of response to lenalidomide plus dexamethasone is associated with improved clinical outcomes in patients with relapsed or refractory multiple myeloma.

BACKGROUND: This retrospective pooled analysis of two phase III trials (MM-009/MM-010) compared clinical outcomes of patients who achieved a complete response or very good partial response to treatment with lenalidomide plus dexamethasone with the outcomes of those who only achieved a partial response. DESIGN AND METHODS: Patients (n=353) received lenalidomide (25 mg/day for 21 days of each 28-day cycle) plus dexamethasone (40 mg on days 1-4, 9-12, and 17-20 for four cycles, and only on days 1-4 after the first four cycles). Time to response, duration of response, time-to-progression, overall survival, and adverse events were investigated for patients who had a complete or very good partial response and compared with those of patients who had a partial response. RESULTS: At the time of unblinding, 32% of patients had achieved a complete or very good partial response and 28% had a partial response. Half (50.5%) of the patients who had a partial response as their initial response achieved a complete or very good partial response with further treatment. The probability of achieving a complete or very good partial response with continued lenalidomide treatment decreased with delayed achievement of a partial response (by cycle 4 versus later); however, it remained clinically significant. With an extended follow-up of 48 months, the median response duration, time-to-progression, and overall survival were longer in patients with a complete or very good partial response than in those with a partial response (24.0 versus 8.3 months, P<0.001; 27.7 versus 12.0 months, P<0.001; not reached versus 44.2 months, P=0.021, respectively). The benefit of a complete or very good partial response was independent of when it was achieved. CONCLUSIONS: Continuing treatment with lenalidomide plus dexamethasone to achieve best response, in the absence of disease progression and toxicity, provided deeper remissions and greater clinical benefit over time for patients in this study.

Muscle defects due to perturbed somite segmentation contribute to late adult scoliosis.

Scoliosis is an abnormal bending of the body axis. Truncated vertebrae or a debilitated ability to control the musculature in the back can cause this condition, but in most cases the causative reason for scoliosis is unknown (idiopathic). Using mutants for somite clock genes with mild defects in the vertebral column, we here show that early defects in somitogenesis are not overcome during development and have long lasting and profound consequences for muscle fiber organization, structure and whole muscle volume. These mutants present only mild alterations in the vertebral column, and muscle shortcomings are uncoupled from skeletal defects. None of the mutants presents an overt musculoskeletal phenotype at larval or early adult stages, presumably due to compensatory growth mechanisms. Scoliosis becomes only apparent during aging. We conclude that adult degenerative scoliosis is due to disturbed crosstalk between vertebrae and muscles during early development, resulting in subsequent adult muscle weakness and bending of the body axis.

Expanded safety experience with lenalidomide plus dexamethasone in relapsed or refractory multiple myeloma.

Lenalidomide gained Food and Drug Administration (FDA) approval for treatment of patients with relapsed or refractory multiple myeloma (MM) in combination with dexamethasone in June 2006. In April 2005, the FDA and patient advocacy groups requested an expanded access programme to both provide lenalidomide to patients likely to benefit and obtain additional safety information. Relapsed/refractory MM patients received lenalidomide 25 mg/d (days 1-21) and dexamethasone 40 mg/d (days 1-4, 9-12, and 17-20 of cycles 1-4; days 1-4 only from cycle 5 onwards), in 4-week cycles until disease progression, study drug discontinuation, or lenalidomide approval. Of the 1438 patients enrolled, approximately 60% were male, median age was 64 years, and 61.7% had Durie-Salmon stage III disease. Median time on study was 15.4 weeks (range: 0.1-49.1) and median dose was 25 mg. The most common adverse events (AEs) were haematological (49%), gastrointestinal (59%), and fatigue (55%). The most common grade > or =3 AEs were haematological (45%), fatigue (10%), and pneumonia (7%). The most common serious AEs were pneumonia (8%), pyrexia (4%), and deep-vein thrombosis (3%). Primary cause of death was disease progression (10%). Safety data confirmed known AEs of lenalidomide plus dexamethasone therapy in patients with relapsed/refractory MM.

Lenalidomide in combination with dexamethasone at first relapse in comparison with its use as later salvage therapy in relapsed or refractory multiple myeloma.

This subset analysis of data from two phase III studies in patients with relapsed or refractory multiple myeloma (MM) evaluated the benefit of initiating lenalidomide plus dexamethasone at first relapse. Multivariate analysis showed that fewer prior therapies, along with beta(2)-microglobulin (< or = 2.5 mg/L), predicted a better time to progression (TTP; study end-point) with lenalidomide plus dexamethasone treatment. Patients with one prior therapy showed a significant improvement in benefit after first relapse compared with those who received two or more therapies. Patients with one prior therapy had significantly prolonged median TTP (17.1 vs. 10.6 months; P = 0.026) and progression-free survival (14.1 vs. 9.5 months, P = 0.047) compared with patients treated in later lines. Overall response rates were higher (66.9% vs. 56.8%, P = 0.06), and the complete response plus very good partial response rate was significantly higher in first relapse (39.8% vs. 27.7%, P = 0.025). Importantly, overall survival was significantly prolonged for patients treated with lenalidomide plus dexamethasone with one prior therapy, compared with patients treated later in salvage (median of 42.0 vs. 35.8 months, P = 0.041), with no differences in toxicity, dose reductions, or discontinuations despite longer treatment. Therefore, lenalidomide plus dexamethasone is both effective and tolerable for second-line MM therapy and the data suggest that the greatest benefit occurs with earlier use.

Melphalan, prednisone, and lenalidomide for newly diagnosed myeloma: kinetics of neutropenia and thrombocytopenia and time-to-event results.

BACKGROUND: Initial analysis of the combination melphalan, prednisone, plus lenalidomide (MPR) showed significant antimyeloma activity in patients with untreated multiple myeloma, with neutropenia and thrombocytopenia as the most frequent side effects. This updated analysis reassessed the kinetics of neutropenia and thrombocytopenia as well as the safety and efficacy of MPR. PATIENTS AND METHODS: A total of 21 patients with newly diagnosed myeloma received melphalan 0.18 mg/kg on days 1-4, prednisone 2 mg/kg on days 1-4, and lenalidomide 10 mg daily on days 1-21 for nine 28-day cycles, followed by maintenance therapy with lenalidomide 10 mg daily on days 1-21. RESULTS: Grade 3/4 neutropenia occurred in 52% of the patients, and granulocyte colonystimulating factor was administered in 43%. The mean neutrophil counts at the start of each MPR cycle, during nadir, and after 6 months of maintenance were 2.69 x 109/L, 1.43 x 109/L, and 2.11 x 109/L, respectively. Grade 3/4 thrombocytopenia occurred in 24% of the patients. Platelet transfusions were required by 1 patient (5%) with a platelet count of 16 x 109/L; however, no thrombocytopenia-associated bleeding was reported. The mean platelet counts at the start of each cycle, during nadir, and after 6 months of maintenance were 174 x 109/L, 121 x 109/L, and 158 x 109/L, respectively. Median follow-up was 29.6 months, median progression-free survival was 28.5 months, and 2-year overall survival was 91%. CONCLUSION: MPR is a promising regimen with manageable hematologic toxicity.

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.