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Immunomodulatory drugs (IMiDs) have improved survival of patients with multiple myeloma (MM) and comprise the therapeutic backbone at all phases of therapy. Although well-tolerated, IMiDs increase rates of venous thromboembolism (VTE). In this phase IV, single-arm pilot study, fifty patients with MM on IMiDs received apixaban 2·5 mg orally twice daily for primary prevention of VTE and were prospectively monitored for six months. The primary safety outcomes were rates of major haemorrhage and clinically relevant non-major haemorrhage over six months. The primary efficacy outcome was the rate of symptomatic VTE over six months. IMiDs used were lenalidomide (58%) or pomalidomide (42%). During the six-month evaluation period, no patients experienced major haemorrhage or VTE. Three patients experienced clinically relevant, non-major haemorrhage which was managed medically, and all were able to resume apixaban. One patient stopped therapy shortly after initiation due to an allergic reaction to apixaban. No patients experienced stroke, myocardial infarction, or death. In this pilot study, low-dose apixaban was safe and well-tolerated as a primary prevention therapy of VTE for patients with MM receiving IMiDs. Further studies are needed to validate low-dose apixaban as a standard primary prevention anti-thrombotic strategy for patients with MM receiving IMiDs.
© 2020 British Society for Haematology and John Wiley & Sons Ltd.

Thalidomide [α-(N-phthalimido)glutarimide] (1) is a sedative and antiemetic drug originally introduced into the clinic in the 1950s for the treatment of morning sickness. Although marketed as entirely safe, more than 10 000 babies were born with severe birth defects. Thalidomide was banned and subsequently approved for the treatment of multiple myeloma and complications associated with leprosy. Although known for more than 5 decades, the mechanism of teratogenicity remains to be conclusively understood. Various theories have been proposed in the literature including DNA damage and ROS and inhibition of angiogenesis and cereblon. All of the theories have their merits and limitations. Although the recently proposed cereblon theory has gained wide acceptance, it fails to explain the metabolism and low-dose requirement reported by a number of groups. Recently, we have provided convincing structural evidence in support of the presence of arene oxide and the quinone-reactive intermediates. However, the ability of these reactive intermediates to impart toxicity/teratogenicity needs investigation. Herein we report that the oxidative metabolite of thalidomide, dihydroxythalidomide, is responsible for generating ROS and causing DNA damage. We show, using cell lines, the formation of comet (DNA damage) and ROS. Using DNA-cleavage assays, we also show that catalase, radical scavengers, and desferal are capable of inhibiting DNA damage. A mechanism of teratogenicity is proposed that not only explains the DNA-damaging property but also the metabolism, low concentration, and species-specificity requirements of thalidomide.

Evidence has been presented for auto-induced human cytochrome P450 3A enzyme involvement in the teratogenicity and clinical outcome of thalidomide due to oxidation to 5-hydroxythalidomide and subsequent metabolic activation in livers. In this study, more relevant human placenta preparations and placental BeWo cells showed low but detectable P450 3A4/5 mRNA expression and drug oxidation activities. Human placental microsomal fractions from three subjects showed detectable midazolam 1´- and 4-hydroxylation and thalidomide 5-hydroxylation activities. Human placental BeWo cells, cultured in the recommended media, also indicated detectable midazolam 1´- and 4-hydroxylation and thalidomide 5-hydroxylation activities. To reduce any masking effects by endogenous hormones used in the recommended media, induction of P450 3A4/5 mRNA and oxidation activities were measured in placental BeWo cells cultured with a modified medium containing 5% charcoal-stripped fetal bovine serum. Thalidomide significantly induced P450 3A4/5, 2B6, and pregnane X receptor (PXR) mRNA levels 2 to 3-fold, but rifampicin only enhanced P450 3A5 and PXR mRNA under the modified media conditions. Under these modified conditions, thalidomide also significantly induced midazolam 1´-hydroxylation and thalidomide 5-hydroxylaion activities 3-fold but not bupropion hydroxylation activity. Taken together, activation of thalidomide to 5-hydroxythalidomide with autoinduction of P450 3A enzymes in human placentas, as well as livers, is suggested in vivo.

1. Pomalidomide has been shown to be potentially teratogenic in thalidomide-sensitive animal species such as rabbits. Screening for thalidomide analogs devoid of teratogenicity/toxicity - attributable to metabolites formed by cytochrome P450 enzymes - but having immunomodulatory properties is a strategic pathway towards development of new anticancer drugs. 2. In this study, plasma concentrations of pomalidomide, its primary 5-hydroxylated metabolite, and its glucuronide conjugate(s) were investigated in control and humanized-liver mice. Following oral administration of pomalidomide (100 mg/kg), plasma concentrations of 7-hydroxypomalidomide and 5-hydroxypomalidomide glucuronide were slightly higher in humanized-liver mice than in control mice. 3. Simulations of human plasma concentrations of pomalidomide were achieved with simplified physiologically-based pharmacokinetic models in both groups of mice in accordance with reported pomalidomide concentrations after low dose administration in humans. 4. The results indicate that pharmacokinetic profiles of pomalidomide were roughly similar between control mice and humanized-liver mice and that control and humanized-liver mice mediated pomalidomide 5-hydroxylation in vivo. Introducing one aromatic amino group into thalidomide resulted in less species differences in in vivo pharmacokinetics in control and humanized-liver mice.

Importance - Multiple myeloma (MM) is the second most common hematological malignant abnormality. The introduction of immunomodulatory drugs (IMiDs) and proteasome inhibitors (PIs) has greatly improved the overall survival of patients with MM. Prevention and treatment of cardiovascular and thrombotic issues associated with novel MM therapies have emerged as important aspects of supportive care in patients with MM.
Observations - We searched PubMed and the Cochrance database for studies published from March 2001 to January 2016. Emerging evidence suggests that both IMiDs and PIs can have cardiovascular (CV) sequelae, which include thromboembolic complications, cardiac, and vascular toxic effects. These complications occur against the backdrop of a high prevalence of CV disease in the MM population as well as the adverse cardiac and vascular effects of MM itself.
Conclusions and Relevance - This review provides an overview of the incidences, clinical presentations, and mechanisms of CV complications in the MM population. We conclude that more research is needed for better screening and preventive strategies to abrogate these toxic effects and improve patient care.

Bioactivation of 5-hydroxy-[carbonyl-(14)C]thalidomide, a known metabolite of thalidomide, by human artificial or native cytochrome P450 3A enzymes, and nonspecific binding in livers of mice was assessed using two-dimensional electrophoresis combined with accelerator mass spectrometry. The apparent major target proteins were liver microsomal cytochrome c oxidase subunit 6B1 and ATP synthase subunit α in mice containing humanized P450 3A genes or transplanted humanized liver. Liver cytosolic retinal dehydrogenase 1 and glutathione transferase A1 were targets in humanized mice with P450 3A and hepatocytes, respectively. 5-Hydroxythalidomide is bioactivated by human P450 3A enzymes and trapped with proteins nonspecifically in humanized mice.

Species differences exist in terms of drug oxidation activities, which are mediated mainly by cytochrome P450 (P450) enzymes. To overcome the problem of species extrapolation, transchromosomic mice containing a human P450 3A cluster or chimeric mice transplanted with human hepatocytes have been introduced into the human toxicology research area. In this review, drug metabolism and disposition mediated by humanized livers in chimeric mice are summarized in terms of biliary/urinary excretions of phthalate and bisphenol A and plasma clearances of the human cocktail probe drugs caffeine, warfarin, omeprazole, metoprolol, and midazolam. Simulation of human plasma concentrations of the teratogen thalidomide and its human metabolites is possible with a simplified physiologically based pharmacokinetic model based on data obtained in chimeric mice, in accordance with reported clinical thalidomide concentrations. In addition, in vivo nonspecific hepatic protein binding parameters of metabolically activated C-drug candidate and hepatotoxic medicines in humanized liver mice can be analyzed by accelerator mass spectrometry and are useful for predictions in humans.

Venous thromboembolism (VTE) is an increasingly recognized problem in the post-hematopoietic stem cell transplantation (HSCT) setting, with a lack of high-quality evidence-based data to recommend best practices. Few patients with hematologic malignancies and even fewer post-HSCT patients were included in randomized trials of VTE prophylaxis and treatment. Prior VTE, GVHD, infections and indwelling venous catheters are risk factors for thrombosis. The increasing use of post-transplant maintenance therapy with lenalidomide in patients with multiple myeloma adds to this risk after autologous HSCT. These patients are also at high risk of bleeding complications because of prolonged thrombocytopenia and managing the competing risks of bleeding and thrombosis can be challenging. This review aims to provide a practical, clinician-focused approach to the prevention and treatment of VTE in the post-HSCT setting.

Plasma concentrations of thalidomide and primary 5-hydroxylated metabolites including 5,6-dihydroxythalidomide and glutathione (GSH) conjugate(s) were investigated in chimeric mice with highly "humanized" liver cells harboring cytochrome P450 3A5*1. Following oral administration of thalidomide (100 mg/kg), plasma concentrations of GSH conjugate(s) of 5-hydroxythalidomide were higher in humanized mice than in controls. Simulation of human plasma concentrations of thalidomide were achieved with a simplified physiologically based pharmacokinetic model in accordance with reported thalidomide concentrations. The results indicate that the pharmacokinetics in humans of GSH conjugate and/or catechol primary 5-hydroxylated thalidomide contributing in vivo activation can be estimated for the first time.

As the use of lenalidomide expands, the poorly understood phenomenon of lenalidomide-induced thyroid abnormalities will increase. In this study, we compared rates of therapy-induced hypothyroidism in 329 patients with diffuse large B-cell lymphoma (DLBCL) treated with conventional chemotherapy (DLBCL-c) or conventional chemotherapy plus lenalidomide (DLBCL-len). We measured serum levels of tumor necrosis factor α, interferon gamma, interleukin 6, interleukin 12, and interleukin 15 before and after treatment. We found a significantly higher rate of therapy-induced hypothyroidism in the DLBCL-len group (25.8% vs. 1.3%), and we found a statistically significant increase in serum tumor necrosis factor α in patients with lenalidomide-induced hypothyroidism.
Copyright © 2015 ISEH - International Society for Experimental Hematology. Published by Elsevier Inc. All rights reserved.