Evaluation of the developmental toxicity of lenalidomide in rabbits

Differential Analysis of Cereblon Neosubstrates in Rabbit Embryos Using Targeted Proteomics

Targeted protein degradation is the selective removal of a protein of interest through hijacking intracellular protein cleanup machinery. This rapidly growing field currently relies heavily on the use of the E3 ligase cereblon (CRBN) to target proteins for degradation, including the immunomodulatory drugs (IMiDs) thalidomide, lenalidomide, and pomalidomide which work through a molecular glue mechanism of action with CRBN. While CRBN recruitment can result in degradation of a specific protein of interest (e.g., efficacy), degradation of other proteins (called CRBN neosubstrates) also occurs. Degradation of one or more of these CRBN neosubstrates is believed to play an important role in thalidomide-related developmental toxicity observed in rabbits and primates. We identified a set of 25 proteins of interest associated with CRBN-related protein homeostasis and/or embryo/fetal development. We developed a targeted assay for these proteins combining peptide immunoaffinity enrichment and high-resolution mass spectrometry and successfully applied this assay to rabbit embryo samples from pregnant rabbits dosed with three IMiDs. We confirmed previously reported in vivo decreases in neosubstrates like SALL4, as well as provided evidence of neosubstrate changes for proteins only examined in vitro previously. While there were many proteins that were similarly decreased by all three IMiDs, no compound had the exact same neosubstrate degradation profile as another. We compared our data to previous literature reports of IMiD-induced degradation and known developmental biology associations. Based on our observations, we recommend monitoring at least a major subset of these neosubstrates in a developmental test system to improve CRBN-binding compound-specific risk assessment. A strength of our assay is that it is configurable, and the target list can be readily adapted to focus on only a subset of proteins of interest or expanded to incorporate new findings as additional information about CRBN biology is discovered.

Animal-free assessment of developmental toxicity: Combining PBPK modeling with the ReproTracker assay

in vitro screening platforms to assess teratogenic potential of compounds are emerging rapidly. ReproTracker is a human induced pluripotent stem cells (hiPSCs)-based biomarker assay that is shown to identify the teratogenicity potential of new pharmaceuticals and chemicals reliably. In its current state, the assay is limited to identifying the potential teratogenic effects and does not immediately quantify a clinical dose relevant to the exposure of chemicals or drugs observable in mothers or fetuses. The goal of this study was to evaluate whether the ReproTracker assay can be extrapolated in vivo and quantitatively predict developmental toxicity exposure levels of two known human teratogens, thalidomide, and carbamazepine. Here, we utilized Physiologically Based Pharmacokinetic (PBPK) modeling to describe the pharmacokinetic behavior of these compounds and conducted an in vitro to in vivo extrapolation (IVIVE) approach to predict human equivalent effect doses (HEDs) that correspond with in vitro concentrations potentially associated with adverse outcomes in ReproTracker. The HEDs derived from the ReproTracker concentration predicted to cause developmental toxicity were close to the reported teratogenic human clinical doses and the HED derived from the rat or rabbit developmental toxicity study. The ReproTracker derived-HED revealed to be sensitive and protective of humans. Overall, this pilot study demonstrated the importance of integrating PBPK model in extrapolating and assessing developmental toxicity in vitro. The combination of these tools demonstrated that they could improve the safety assessment of drugs and chemicals without animal testing.

A New Strategy for the Old Challenge of Thalidomide: Systems Biology Prioritization of Potential Immunomodulatory Drug (IMiD)-Targeted Transcription Factors

Several molecular mechanisms of thalidomide embryopathy (TE) have been investigated, from anti-angiogenesis to oxidative stress to cereblon binding. Recently, it was discovered that thalidomide and its analogs, named immunomodulatory drugs (IMiDs), induced the degradation of C2H2 transcription factors (TFs). This mechanism might impact the strict transcriptional regulation of the developing embryo. Hence, this study aims to evaluate the TFs altered by IMiDs, prioritizing the ones associated with embryogenesis through transcriptome and systems biology-allied analyses. This study comprises only the experimental data accessed through bioinformatics databases. First, proteins and genes reported in the literature as altered/affected by the IMiDs were annotated. A protein systems biology network was evaluated. TFs beta-catenin (CTNNB1) and SP1 play more central roles: beta-catenin is an essential protein in the network, while SP1 is a putative C2H2 candidate for IMiD-induced degradation. Separately, the differential expressions of the annotated genes were analyzed through 23 publicly available transcriptomes, presenting 8624 differentially expressed genes (2947 in two or more datasets). Seventeen C2H2 TFs were identified as related to embryonic development but not studied for IMiD exposure; these TFs are potential IMiDs degradation neosubstrates. This is the first study to suggest an integration of IMiD molecular mechanisms through C2H2 TF degradation.

Repurposing Pomalidomide as a Neuroprotective Drug: Efficacy in an Alpha-Synuclein-Based Model of Parkinson's Disease

Marketed drugs for Parkinson's disease (PD) treat disease motor symptoms but are ineffective in stopping or slowing disease progression. In the quest of novel pharmacological approaches that may target disease progression, drug-repurposing provides a strategy to accelerate the preclinical and clinical testing of drugs already approved for other medical indications. Here, we targeted the inflammatory component of PD pathology, by testing for the first time the disease-modifying properties of the immunomodulatory imide drug (IMiD) pomalidomide in a translational rat model of PD neuropathology based on the intranigral bilateral infusion of toxic preformed oligomers of human α-synuclein (H-αSynOs). The neuroprotective effect of pomalidomide (20 mg/kg; i.p. three times/week 48 h apart) was tested in the first stage of disease progression by means of a chronic two-month administration, starting 1 month after H-αSynOs infusion, when an already ongoing neuroinflammation is observed. The intracerebral infusion of H-αSynOs induced an impairment in motor and coordination performance that was fully rescued by pomalidomide, as assessed via a battery of motor tests three months after infusion. Moreover, H-αSynOs-infused rats displayed a 40-45% cell loss within the bilateral substantia nigra, as measured by stereological counting of TH + and Nissl-stained neurons, that was largely abolished by pomalidomide. The inflammatory response to H-αSynOs infusion and the pomalidomide treatment was evaluated both in CNS affected areas and peripherally in the serum. A reactive microgliosis, measured as the volume occupied by the microglial marker Iba-1, was present in the substantia nigra three months after H-αSynOs infusion as well as after H-αSynOs plus pomalidomide treatment. However, microglia differed for their phenotype among experimental groups. After H-αSynOs infusion, microglia displayed a proinflammatory profile, producing a large amount of the proinflammatory cytokine TNF-α. In contrast, pomalidomide inhibited the TNF-α overproduction and elevated the anti-inflammatory cytokine IL-10. Moreover, the H-αSynOs infusion induced a systemic inflammation with overproduction of serum proinflammatory cytokines and chemokines, that was largely mitigated by pomalidomide. Results provide evidence of the disease modifying potential of pomalidomide in a neuropathological rodent model of PD and support the repurposing of this drug for clinical testing in PD patients.

The road (not) taken - Placental transfer and interspecies differences

Species differences are among the main reasons for the high failure rate of preclinical studies. A better awareness and understanding of these differences might help to improve the outcome of preclinical research. In reproduction, the placenta is the central organ regulating fetal exposure to a substance circulating in the maternal organism. Exact information about placental transfer can help to better estimate the toxic potential of a substance. From an evolutionary point of view, the chorioallantoic placenta is the organ with the highest anatomical diversity among species. Moreover, frequently used animal models in reproduction belong to rodents and lagomorphs, two groups that are characterized by the generation of an additional type of placenta, which is crucial for fetal development, but absent from humans: the inverted yolk sac placenta. Taken together, the translatability of placental transfer studies from laboratory animals to humans is challenging, which is supported by the fact that numerous species-dependent toxic effects are described in literature. Thus, reliable human-relevant data are frequently lacking and the toxic potential of chemicals and pharmaceuticals for humans can hardly be estimated, often resulting in recommendations that medical treatments or exposure to chemicals should be avoided for safety reasons. Although species differences of placental anatomy have been described frequently and the need for human-relevant research models has been emphasized, analyses of substances with species-dependent placental transfer have been performed only sporadically. Here, we present examples for species-specific placental transfer, including that of nanoparticles and pharmaceuticals, and discuss potential underlying mechanisms. With respect to the COVID 19-pandemic it might be of interest that some antiviral drugs are reported to feature species-specific placental transfer. Further, differences in placental structure and antibody transfer may affect placental transfer of ZIKA virus.

Comparative Genomics Identifies Putative Interspecies Mechanisms Underlying Crbn-Sall4-Linked Thalidomide Embryopathy

The identification of thalidomide–Cereblon-induced SALL4 degradation has brought new understanding for thalidomide embryopathy (TE) differences across species. Some questions, however, regarding species variability, still remain. The aim of this study was to detect sequence divergences between species, affected or not by TE, and to evaluate the regulated gene co-expression in a murine model. Here, we performed a comparative analysis of proteins experimentally established as affected by thalidomide exposure, evaluating 14 species. The comparative analysis, regarding synteny, neighborhood, and protein conservation, was performed in 42 selected genes. Differential co-expression analysis was performed, using a publicly available assay, GSE61306, which evaluated mouse embryonic stem cells (mESC) exposed to thalidomide. The comparative analyses evidenced 20 genes in the upstream neighborhood of NOS3, which are different between the species who develop, or not, the classic TE phenotype. Considering protein sequence alignments, RECQL4, SALL4, CDH5, KDR, and NOS2 proteins had the biggest number of variants reported in unaffected species. In co-expression analysis, Crbn was a gene identified as a driver of the co-expression of other genes implicated in genetic, non-teratogenic, limb reduction defects (LRD), such as Tbx5, Esco2, Recql4, and Sall4; Crbn and Sall4 were shown to have a moderate co-expression correlation, which is affected after thalidomide exposure. Hence, even though the classic TE phenotype is not identified in mice, a deregulatory Crbn-induced mechanism is suggested in this animal. Functional studies are necessary, especially evaluating the genes responsible for LRD syndromes and their interaction with thalidomide–Cereblon.

Novel agents for the treatment of lymphomas during pregnancy: A comprehensive literature review

Lymphoproliferative diseases occurring during pregnancy present unique diagnostic and therapeutic challenges aiming to achieve maternal cure without impairing fetal health, growth, and survival. These goals are further complicated by the fast-paced emergence of novel therapies and their introduction as standard of care, even in newly diagnosed patients. Due to the rarity of hematological malignancies in pregnancy and the exclusion of pregnancy in almost all clinical trials, available data on the fetal effects of novel drugs are limited to animal models and case reports. The current review addresses the entire multidisciplinary team involved in treating pregnant patients with lymphoproliferative diseases. We describe novel agents according to their mechanism of action, and summarize our knowledge of their effects during the gestational period, particularly those associated with fetotoxicity. Therapeutic dilemmas associated with the employment of these new agents are also discussed.

Contamination of lenalidomide on blister packages after administration and its exposure countermeasures

BACKGROUND

Reliable exposure control measures are needed to avoid occupational exposures from hazardous drugs. However, there is little information on blister packages concerning exposure. We investigated the contamination and exposure control methods of lenalidomide.

MATERIALS AND METHODS

Nine facilities involved with the RevMate program (the Japanese REMS program) participated in this study. Blister packages (10 capsules/ sheet, no cuts) were collected from each institution after the administration of 5-mg Revlimid capsules. Additionally, the safety performance of different gloves was tested.

RESULTS

A total of 18 samples were analyzed and the results revealed that all samples were contaminated with lenalidomide. Our questionnaire revealed that all pharmacists handled the blister packages with their bare hands when they were checking the remaining capsules of lenalidomide. We analyzed gloves made from four different materials (nitrile, polyvinyl chloride, latex, and polyethylene) and found no permeability in any glove type.

CONCLUSION

We conclude that the spent blister package is a potential source of exposure to lenalidomide. All medical staff and caregivers should wear gloves when they handle lenalidomide.

Neuroprotection by the Immunomodulatory Drug Pomalidomide in the Drosophila LRRK2WD40 Genetic Model of Parkinson's Disease

The search for new disease-modifying drugs for Parkinson's disease (PD) is a slow and highly expensive process, and the repurposing of drugs already approved for different medical indications is becoming a compelling alternative option for researchers. Genetic variables represent a predisposing factor to the disease and mutations in leucine-rich repeat kinase 2 (LRRK2) locus have been correlated to late-onset autosomal-dominant PD. The common fruit fly Drosophila melanogaster carrying the mutation LRRK2 loss-of-function in the WD40 domain (LRRK2^WD40), is a simple in vivo model of PD and is a valid tool to first evaluate novel therapeutic approaches to the disease. Recent studies have suggested a neuroprotective activity of immunomodulatory agents in PD models. Here the immunomodulatory drug Pomalidomide (POM), a Thalidomide derivative, was examined in the Drosophila LRRK2^WD40 genetic model of PD. Mutant and wild type flies received increasing POM doses (1, 0.5, 0.25 mM) through their diet from day 1 post eclosion, until postnatal day (PN) 7 or 14, when POM's actions were evaluated by quantifying changes in climbing behavior as a measure of motor performance, the number of brain dopaminergic neurons and T-bars, mitochondria integrity. LRRK2^WD40 flies displayed a spontaneous age-related impairment of climbing activity, and POM significantly and dose-dependently improved climbing performance both at PN 7 and PN 14. LRRK2^WD40 fly motor disability was underpinned by a progressive loss of dopaminergic neurons in posterior clusters of the protocerebrum, which are involved in the control of locomotion, by a low number of T-bars density in the presynaptic bouton active zones. POM treatment fully rescued the cell loss in all posterior clusters at PN 7 and PN 14 and significantly increased the T-bars density. Moreover, several damaged mitochondria with dilated cristae were observed in LRRK2^WD40 flies treated with vehicle but not following POM. This study demonstrates the neuroprotective activity of the immunomodulatory agent POM in a genetic model of PD. POM is an FDA-approved clinically available and well-tolerated drug used for the treatment of multiple myeloma. If further validated in mammalian models of PD, POM could rapidly be clinically tested in humans.

Is omphalocele a non-specific malformation in New Zealand White rabbits?

We evaluated the incidence of omphalocele, a malformation that occurs sporadically in many studies. We assembled data on external malformations using all treatment groups from every study published in three major journals over the past 35 years using New Zealand White rabbits. Fifty-eight papers were included: 4905 litters and 36,977 fetuses. Omphalocele was reported in 43% and was among the most common defects, occurring at a rate of 1.10% (litter) and 0.16% (fetus). The defect did not appear to be treatment-related, although it may have been in two studies, based on rate and dose-responsiveness. Removing these two studies from the analysis, the defect was still prevalent (0.77% litter, 0.11% fetal incidence). Three studies evaluated the effects of food restriction and omphalocele was observed with food restriction in two of them, suggesting that decreased maternal weight gain or food consumption may be causal. Otherwise, it appears to be spontaneous and common.

Thalidomide and its analogues: A review of the potential for immunomodulation of fibrosis diseases and opthalmopathy

The US Food and Drug Administration approved thalidomide and its analogues for the treatment of erythema nodosum leprosum, in spite of the notoriety of reports of severe birth defects in the middle of the last century. As immunomodulatory drugs, thalidomide and its analogues have been used to effectively treat various diseases. In the present review, preclinical data about the effects of thalidomide and its analogues on the immune system are integrated, including the effects of cytokines on transdifferentiation, the anti-inflammatory effect, immune cell function regulation and angiogenesis. The present review also investigates the latest developments of thalidomide as a therapeutic option for the treatment of idiopathic pulmonary fibrosis, skin fibrosis, and ophthalmopathies.

The impact of thalidomide use in birth defects in Brazil

Although the thalidomide tragedy occurred more than 50 years ago, the medication is still being used worldwide for different reasons, and several aspects regarding its teratogenicity remain unsolved. Despite the strict regulation implemented, new cases of thalidomide embryopathy (TE) are still being registered in Brazil. Furthermore, the molecular processes that lead to malformations when the embryo is exposed to thalidomide have not yet been fully identified. In this article, we perform a critical analysis of thalidomide's history in Brazil, highlighting aspects of the occurrence of TE over the decades. Finally, we present the main perspectives and challenges for ongoing surveillance and prevention of TE in Brazil. The effective control of dispensing thalidomide, especially in areas where leprosy is endemic, is one of the most important and challenging points. Furthermore, the emergence of thalidomide analogues is fast approaching, and their availability would pose additional concerns. The understanding of the molecular mechanisms and targets of thalidomide in both experimental and human models is essential for generating new insights into teratogenic mechanisms, so that safer thalidomide analogues can be developed.

A novel effect of thalidomide and its analogs: suppression of cereblon ubiquitination enhances ubiquitin ligase function

The immunomodulatory drug (IMiD) thalidomide and its structural analogs lenalidomide and pomalidomide are highly effective in treating clinical indications. Thalidomide binds to cereblon (CRBN), a substrate receptor of the cullin-4 really interesting new gene (RING) E3 ligase complex. Here, we examine the effect of thalidomide and its analogs on CRBN ubiquitination and its functions in human cell lines. We find that the ubiquitin modification of CRBN includes K48-linked polyubiquitin chains and that thalidomide blocks the formation of CRBN-ubiquitin conjugates. Furthermore, we show that ubiquitinated CRBN is targeted for proteasomal degradation. Treatment of human myeloma cell lines such as MM1.S, OPM2, and U266 with thalidomide (100 μM) and its structural analog lenalidomide (10 μM) results in stabilization of CRBN and elevation of CRBN protein levels. This in turn leads to the reduced level of CRBN target proteins and enhances the sensitivity of human multiple myeloma cells to IMiDs. Our results reveal a novel mechanism by which thalidomide and its analogs modulate the CRBN function in cells. Through inhibition of CRBN ubiquitination, thalidomide and its analogs allow CRBN to accumulate, leading to the increased cullin-4 RING E3 ligase-mediated degradation of target proteins.

Advances in treating chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most prevalent type of leukemia, affects mostly elderly CLL patients, and is incurable without allogeneic transplantation. Although classic chemo(immuno)therapy is still the standard of care for patients in need of treatment, this paradigm might change in the near future with the advent of new therapeutic agents targeting major pathogenic pathways in CLL.

Pomalidomide in the treatment of multiple myeloma and perspectives in other hematological malignancies

SUMMARY 

Pomalidomide is an immunomodulatory drug recently approved by the US FDA and EMA for the treatment of refractory and relapsed multiple myeloma. Pomalidomide appears to be more potent and less toxic than thalidomide and lenalidomide and has proven to be effective in a proportion of patients already exposed and refractory to these agents. The approved combination of pomalidomide and weekly dexamethasone offers clinical benefit to at least one-third of patients with multiple myeloma that have failed both bortezomib and lenolidomide treatment. This review will focus on the preclinical data and clinical experience in this setting. Off-label use of pomalidomide, mainly its combination with other active drugs for multiple myeloma and the role of pomalidomide in other hematologic malignancies still remain to be explored in depth and are discussed briefly.

Common nature in the effects of thalidomide on embryo-fetal development in Kbl:JW and Kbl:NZW rabbits

The effects of thalidomide on the embryo-fetal development (EFD) of rabbit fetuses and the sensitive periods (SP) for the various malformations were compared between Kbl:JW and Kbl:NZW rabbits to investigate possible strain differences. The post-implantation loss rate and number of placental remnants were increased and the number of live fetuses was decreased in both of the strains in the EFD study and in Kbl:NZW at 300 mg/kg dosed on GD 7-8 in the SP study. In the external and skeletal examinations, head, limb and tail malformations were observed in both the strains in the EFD and SP studies at the same dose levels in the same dosing period. In the visceral examination, hydrocephaly, cardiovascular malformations, absent pulmonary intermedial lobe, diaphragmatic hernia and/or abnormal liver lobation were also observed in both of the strains in the EFD and SP studies at the same dose levels and in the same dosing period. Plasma concentrations of thalidomide were equivalent between the two strains in the SP study. There were strain differences in some parameters, such as the post-implantation loss rate and the frequencies of malformations in forelimb and hindlimb and pulmonary intermedial lobe, but similar types of malformations or variations were induced at the same dose levels on the same dosing period in both strains. Therefore, it is concluded that there were no essential differences in sensitivity of the fetuses to thalidomide between Kbl:JW and NZW rabbits and both of the strains are useful to evaluate the teratogenic effects of thalidomide.

Human cytochrome P450 oxidation of 5-hydroxythalidomide and pomalidomide, an amino analogue of thalidomide

The sedative and antiemetic drug thalidomide [α-(N-phthalimido)glutarimide] was withdrawn in the early 1960s because of its potent teratogenic effects but was approved for the treatment of lesions associated with leprosy in 1998 and multiple myeloma in 2006. The mechanism of teratogenicity of thalidomide still remains unclear, but it is well-established that metabolism of thalidomide is important for both teratogenicity and cancer treatment outcome. Thalidomide is oxidized by various cytochrome P450 (P450) enzymes, the major one being P450 2C19, to 5-hydroxy-, 5'-hydroxy-, and dihydroxythalidomide. We previously reported that P450 3A4 oxidizes thalidomide to the 5-hydroxy and dihydroxy metabolites, with the second oxidation step involving a reactive intermediate, possibly an arene oxide, that can be trapped by glutathione (GSH) to GSH adducts. We now show that the dihydroxythalidomide metabolite can be further oxidized to a quinone intermediate. Human P450s 2J2, 2C18, and 4A11 were also found to oxidize 5-hydroxythalidomide to dihydroxy products. Unlike P450s 2C19 and 3A4, neither P450 2J2, 2C18, nor 4A11 oxidized thalidomide itself. A recently approved amino analogue of thalidomide, pomalidomide (CC-4047, Actimid), was also oxidized by human liver microsomes and P450s 2C19, 3A4, and 2J2 to the corresponding phthalimide ring-hydroxylated product.

Thalidomide Embryopathy: An Enigmatic Challenge

Thalidomide remains one of the world’s most notorious drugs due to the severe birth defects it induced in children between 1957 and 1962. Yet, to some this drug is a lifesaver, as it now enjoys renaissance in the treatment for a wide range of conditions including leprosy, multiple myeloma, Behcet’s disease, and some cancers. However, thalidomide has also been linked to causing a new generation of thalidomide survivors in Brazil, where the drug is used to treat leprosy. Surprisingly how thalidomide causes birth defects and how it acts in the treatment of clinical conditions are still far from clear. In the past decade great strides in our understanding of the actions of the drug, as well as molecular targets, have been made. The purpose of this review is to look at the recent work carried out into understanding how thalidomide causes birth defects, it’s molecular targets and the challenges that remain to be elucidated. These challenges include identifying clinically relevant but nonteratogenic forms of the drug, and the mechanisms underlying phocomelia and species specificity.

Trial Watch: Lenalidomide-based immunochemotherapy

Lenalidomide is a synthetic derivative of thalidomide currently approved by the US Food and Drug Administration for use in patients affected by multiple myeloma (in combination with dexamethasone) and low or intermediate-1 risk myelodysplastic syndromes that harbor 5q cytogenetic abnormalities. For illustrative purposes, the mechanism of action of lenalidomide can be subdivided into a cancer cell-intrinsic, a stromal, and an immunological component. Indeed, lenalidomide not only exerts direct cell cycle-arresting and pro-apoptotic effects on malignant cells, but also interferes with their physical and functional interaction with the tumor microenvironment and mediates a robust, pleiotropic immunostimulatory activity. In particular, lenalidomide has been shown to stimulate the cytotoxic functions of T lymphocytes and natural killer cells, to limit the immunosuppressive impact of regulatory T cells, and to modulate the secretion of a wide range of cytokines, including tumor necrosis factor α, interferon γ as well as interleukin (IL)-6, IL-10, and IL-12. Throughout the last decade, the antineoplastic and immunostimulatory potential of lenalidomide has been investigated in patients affected by a wide variety of hematological and solid malignancies. Here, we discuss the results of these studies and review the status of clinical trials currently assessing the safety and efficacy of this potent immunomodulatory drug in oncological indications.

Pomalidomide is nonteratogenic in chicken and zebrafish embryos and nonneurotoxic in vitro

Thalidomide and its analog, Lenalidomide, are in current use clinically for treatment of multiple myeloma, complications of leprosy and cancers. An additional analog, Pomalidomide, has recently been licensed for treatment of multiple myeloma, and is purported to be clinically more potent than either Thalidomide or Lenalidomide. Using a combination of zebrafish and chicken embryos together with in vitro assays we have determined the relative anti-inflammatory activity of each compound. We demonstrate that in vivo embryonic assays Pomalidomide is a significantly more potent anti-inflammatory agent than either Thalidomide or Lenalidomide. We tested the effect of Pomalidomide and Lenalidomide on angiogenesis, teratogenesis, and neurite outgrowth, known detrimental effects of Thalidomide. We found that Pomalidomide, displays a high degree of cell specificity, and has no detectable teratogenic, antiangiogenic or neurotoxic effects at potent anti-inflammatory concentrations. This is in marked contrast to Thalidomide and Lenalidomide, which had detrimental effects on blood vessels, nerves, and embryonic development at anti-inflammatory concentrations. This work has implications for Pomalidomide as a treatment for conditions Thalidomide and Lenalidomide treat currently.

Update on immunomodulatory drugs (IMiDs) in hematologic and solid malignancies

INTRODUCTION

Thalidomide and its analogs [small molecule immunomodulatory drugs (IMiDs®)] are among the most successful new therapeutic agents of recent years. Thalidomide is now an integral part of multiple myeloma (MM) therapy. Lenalidomide has been approved for the treatment of patients with relapsed MM and 5q-myelodysplastic syndromes (MDS). Currently, more than 400 clinical trials are evaluating the activity of lenalidomide, alone or in combination with other conventional or novel therapies, in newly diagnosed MM and 5q-MDS. Based on their broad range of actions within the tumor microenvironment, IMiDs are currently also evaluated in a wide variety of additional hematologic and solid malignancies.

AREAS COVERED

This paper reviews the historic development of thalidomide and its derivatives and presents novel insights into their mode of action. Moreover, it discusses up-to-date clinical trials investigating IMiDs and potential future research and therapeutic perspectives in MM and other malignancies.

EXPERT OPINION

Although IMiDs have emerged as powerful agents for the treatment of hematologic and solid tumors, more preclinical and clinical studies are urgently needed both to increase our knowledge of their mechanisms of action, and to optimize their clinical use, in order to further improve the patient's quality of life and survival.

Correlation of chemical structure with reproductive and developmental toxicity as it relates to the use of the threshold of toxicological concern

In the absence of toxicological data on a chemical, the threshold of toxicological concern (TTC) approach provides a system to estimate a conservative exposure below which there is a low probability of risk for adverse health effects. The original toxicology dataset underlying the TTC was based on NOELs from repeat dose studies. Subsequently there have been several efforts to assess whether or not these limits are also protective for reproductive/developmental effects. This work expands the database of chemicals with reproductive and developmental data, presents these data in a comprehensive and transparent format and groups the chemicals according to the TTC "Cramer Class" rules. Distributions of NOAELs from each of these classes were used to assess whether the previously proposed TTC values based on repeat dose data are protective for reproductive/developmental toxicity endpoints as well. The present analysis indicates that, for each Cramer Class, the reproductive and developmental endpoints would be protected at the corresponding general TTC tiers derived by Munro et al. (1996).

Thalidomide: the tragedy of birth defects and the effective treatment of disease

Thalidomide was a widely used drug in the late 1950s and early 1960s for the treatment of nausea in pregnant women. It became apparent in the 1960s that thalidomide treatment resulted in severe birth defects in thousands of children. Though the use of thalidomide was banned in most countries at that time, thalidomide proved to be a useful treatment for leprosy and later, multiple myeloma. In rural areas of the world that lack extensive medical surveillance initiatives, thalidomide treatment of pregnant women with leprosy has continued to cause malformations. Research on thalidomide mechanisms of action is leading to a better understanding of molecular targets. With an improved understanding of these molecular targets, safer drugs may be designed. The thalidomide tragedy marked a turning point in toxicity testing, as it prompted United States and international regulatory agencies to develop systematic toxicity testing protocols; the use of thalidomide as a tool in developmental biology led to important discoveries in the biochemical pathways of limb development. In celebration of the Society of Toxicology's 50th Anniversary, which coincides with the 50th anniversary of the withdrawal of thalidomide from the market, it is appropriate to revisit the lessons learned from the thalidomide tragedy of the 1960s.

Incorporating novel agents in the treatment of myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are a group of heterogeneous clonal stem cell (SC) disorders that mainly affect the elderly population. They are characterized by ineffective hematopoiesis which results in quantitative and qualitative cellular defects and high incidence of leukemic transformation. Recent advances in MDS research have led to the development of novel agents which appears to improve remission rates and survival when compared to best supportive care. Currently azacitidine, decitabine, and lenalidomide are approved by the US FDA for the treatment of MDS, while the activity of other novel agents such as histone deacetylase inhibitors, farnesyl-transferase inhibitors, novel thrombopoietic agents, and anti-angiogenesis molecules is under evaluation. Erythropoietin-stimulating agents, iron chelating therapy and thrombopoietin receptor ligands may also improve quality of life and possibly prolong survival in MDS patients. The only treatment modality that can achieve long-term survival is the allogeneic SC transplantation which is given only in selected patients. Moreover the heterogeneity of MDS and the patient's advanced age and co-morbidity are significant factors besides cytogenetics, IPSS and WPSS that should be taken into account during the decision-making process. Therefore clinicians should treat patients with MDS on an individual basis aiming the increase of the response rates and the decrease of treatment-associated toxicities. This can only be achieved through the better understanding of the MDS subgroups. If we can better define MDS subgroups we will be able to identify patients who will benefit from the incorporation of the novel agents, as monotherapy or in combinations regimens along with supportive care.

RevAssist: a comprehensive risk minimization programme for preventing fetal exposure to lenalidomide

Lenalidomide (Revlimid) is an immunomodulatory drug and an analogue of thalidomide, a known teratogen. To prevent fetal exposure, in the US lenalidomide is available only under a special restricted distribution programme called RevAssist. Under this risk minimization programme, only prescribers and contract pharmacies registered with the programme are able to prescribe and dispense the product. Patients must be advised of, agree to and comply with the requirements of the RevAssist programme in order to receive lenalidomide through a registered prescriber. A total of 15 584 patients were registered in the RevAssist programme during the first year lenalidomide was on the market. There were four reports of false-positive beta-human chorionic gonadotrophin measurements in patients aged 43-57 years. Mandatory patient and prescriber surveys have shown discrepant responses that were resolved by risk management intervention specialists 99% of the time. The voluntary patient surveys have shown understanding of the risks of lenalidomide use and of behaviours necessary to minimize risks in >95% of females of childbearing potential and adult males. To date, there have been no reports of pregnancy in female patients or female partners of male patients. The pharmacy audit findings showed compliance with RevAssist was high. Although RevAssist is labour-intensive, time-consuming and costly, it continues to be effective in preventing fetal exposure to lenalidomide.