Inhibition of de novo IgM antibody synthesis by thalidomide as a relevant mechanism of action in leprosy

Thalidomide-Revisited: Are COVID-19 Patients Going to Be the Latest Victims of Yet Another Theoretical Drug-Repurposing?

The coronavirus disease 2019 (COVID-19) pandemic is a worldwide threatening health issue. The progression of this viral infection occurs in the airways of the lungs with an exaggerated inflammatory response referred to as the "cytokine storm" that can lead to lethal lung injuries. In the absence of an effective anti-viral molecule and until the formulation of a successful vaccine, anti-inflammatory drugs might offer a complementary tool for controlling the associated complications of COVID-19 and thus decreasing the subsequent fatalities. Drug repurposing for several molecules has emerged as a rapid temporary solution for COVID-19. Among these drugs is Thalidomide; a historically emblematic controversial molecule that harbors an FDA approval for treating erythema nodosum leprosum (ENL) and multiple myeloma (MM). Based on just one-case report that presented positive outcomes in a patient treated amongst others with Thalidomide, two clinical trials on the efficacy and safety of Thalidomide in treating severe respiratory complications in COVID-19 patients were registered. Yet, the absence of substantial evidence on Thalidomide usage in that context along with the discontinued studies on the efficiency of this drug in similar pulmonary diseases, might cause a significant obstacle for carrying out further clinical evaluations. Herein, we will discuss the theoretical effectiveness of Thalidomide in attenuating inflammatory complications that are encountered in COVID-19 patients while pinpointing the lack of the needed evidences to move forward with this drug.

Thalidomide-Revisited: Are COVID-19 Patients Going to Be the Latest Victims of Yet Another Theoretical Drug-Repurposing?

The coronavirus disease 2019 (COVID-19) pandemic is a worldwide threatening health issue. The progression of this viral infection occurs in the airways of the lungs with an exaggerated inflammatory response referred to as the "cytokine storm" that can lead to lethal lung injuries. In the absence of an effective anti-viral molecule and until the formulation of a successful vaccine, anti-inflammatory drugs might offer a complementary tool for controlling the associated complications of COVID-19 and thus decreasing the subsequent fatalities. Drug repurposing for several molecules has emerged as a rapid temporary solution for COVID-19. Among these drugs is Thalidomide; a historically emblematic controversial molecule that harbors an FDA approval for treating erythema nodosum leprosum (ENL) and multiple myeloma (MM). Based on just one-case report that presented positive outcomes in a patient treated amongst others with Thalidomide, two clinical trials on the efficacy and safety of Thalidomide in treating severe respiratory complications in COVID-19 patients were registered. Yet, the absence of substantial evidence on Thalidomide usage in that context along with the discontinued studies on the efficiency of this drug in similar pulmonary diseases, might cause a significant obstacle for carrying out further clinical evaluations. Herein, we will discuss the theoretical effectiveness of Thalidomide in attenuating inflammatory complications that are encountered in COVID-19 patients while pinpointing the lack of the needed evidences to move forward with this drug.

Thalidomide: an old drug with new action

Thalidomide is a drug that, since its development, has made history in the world of medicine--having been withdrawn and now has returned with a boom as an anticancer and immunomodulatory drug. However, its mode of action in various diseases (i.e. different types of hematologic malignancies, solid tumors) as well as in various infections (i.e. pneumonia, tuberculosis, HIV infection etc.) and related inflammatory conditions is not well understood. As the immune system plays an important role in the pathogenesis of both infection-related as well as noninfectious (i.e. cancer) inflammatory diseases, much research has been done in the past few years to discover and design better immunomodulatory agents. Such immunomodulatory agents should be able to target the immune system in such a way that host suffers minimum damage and normal function of the immune system remains intact. In the present review an attempt is made to highlight the immunomodulatory action of thalidomide in various pathologic conditions.

Lenalidomide alone or lenalidomide plus dexamethasone significantly inhibit IgG and IgM in vitro... A possible explanation for their mechanism of action in treating multiple myeloma

Lenalidomide (len) is an analog of thalidomide (thal), and both are used in the treatment of a diverse group of medical conditions. A common finding in this group is the detection of immunoglobulin in skin lesions, or high levels of immunoglobulin or myeloma protein in serum and urine. While their mechanism(s) of action is not known, the drugs are noted for their ability to modulate monocyte, lymphocyte, and natural killer cell functions; suppression of immunoglobulin synthesis could offer an explanation for their effectiveness in treating multiple myeloma (MM). Our objective was to determine if, on an equimolar basis, thal, len or dexamethasone (dex) could affect pokeweed (PWM)-induced synthesis of IgG, IgM and IL-2. When peripheral blood mononuclear cells were stimulated with PWM, len surpassed thal in suppressing IgM and IgG, and enhancing IL-2. Dex enhanced IgG, and suppressed IL-2. When the stimulated cells were treated with len (an effective promoter of IL-2 and suppressor of IgM and IgG) plus dex (an effective suppressor of IL-2 and enhancer of IgG), the net result was suppression of IgM and IgG. The synthesis of IgM and IgG by putative PWM-stimulated B cell blasts is significantly blocked by len. This suggest that the B-lymphocyte is a targeted cell for len, and that suppression of the synthesis of IgG and IgM could provide an explanation for the mechanism by which len effectively treats MM.

Thalidomide inhibited the synthesis of IgM and IgG whereas Thalidomide+Dexamethasone and Dexamethasone alone acted as co-stimulants with pokeweed and enhanced their synthesis

Thalidomide (Thal) provides effective treatment for erythema nodosum leprosum (ENL). In combination with Dexamethasome (Dex) it is an effective treatment for multiple myeloma (MM) and Waldenström's macroglobulinemia (WM). Thal's mechanism(s) of action in the treatment of these diverse medical conditions is not known, but it could be suppression of immunoglobulin (Ig) synthesis. Mononuclear cells were stimulated with pokeweed (PWM), and treated with Thal, Thal+Dex or Dex. The cultures were assayed for IgM and IgG. The maximum synthesis was expected to occur in cultures stimulated with PWM at 0.5, 5.0 or 10 microg/ml. The test agents at 15 microM each were expected to alter the response. Compared to cultures stimulated with PWM alone, there was significantly less Ig in the cultures containing Thal+PWM, and significantly more Ig in the cultures containing Thal+Dex+PWM or Dex+PWM (Wilcoxon). The median % of maximum was 57 for cultures treated with Thal+PWM; 184 for cultures treated with Thal+Dex+PWM, and 139 for cultures treated with Dex+PWM. Thal also acted as a co-stimulant with PWM and enhanced the synthesis of IL-2, IL-6 and DNA; whereas, Thal+Dex or Dex enhanced Ig synthesis, but suppressed IL-2, IL-6 and cell proliferation. Thal's ability to suppress Ig may explain its activity in ENL, MM and WM. The enhancement of Ig by Dex does not help to explain a role for Dex alone or in combination with Thal for the treatment of MM and WM.

Mechanism of action of lenalidomide in hematological malignancies

Immunomodulatory drugs lenalidomide and pomalidomide are synthetic compounds derived by modifying the chemical structure of thalidomide to improve its potency and reduce its side effects. Lenalidomide is a 4-amino-glutamyl analogue of thalidomide that lacks the neurologic side effects of sedation and neuropathy and has emerged as a drug with activity against various hematological and solid malignancies. It is approved by FDA for clinical use in myelodysplastic syndromes with deletion of chromosome 5q and multiple myeloma. Lenalidomide has been shown to be an immunomodulator, affecting both cellular and humoral limbs of the immune system. It has also been shown to have anti-angiogenic properties. Newer studies demonstrate its effects on signal transduction that can partly explain its selective efficacy in subsets of MDS. Even though the exact molecular targets of lenalidomide are not well known, its activity across a spectrum of neoplastic conditions highlights the possibility of multiple target sites of action.

Thalidomide suppressed the growth of 4T1 cells into solid tumors in Balb/c mice in a combination therapy with the oncolytic fusogenic HSV-1 OncdSyn

PURPOSE

The anti-tumor properties of thalidomide or in combination with an oncolytic herpes virus (OncdSyn) was investigated in a mouse model of human breast cancer.

METHODS

To determine if thalidomide could act alone, 4T1 cells were injected into Balb/c mice. Tumors were sized, and the mice were fed chow or chow-containing thalidomide. After 4 days the tumor volumes were compared. To determine if thalidomide could act with the virus, tumors of mice were injected with phosphate buffered saline (PBS), or fed thalidomide with injections of PBS, or fed thalidomide with injections of OncdSyn, or received injections of OncdSyn.

RESULTS

Thalidomide alone suppressed tumor growth. The most significant treatment occurred in thalidomide-fed-OncdSyn-injected mice. Compared to PBS controls, there was a significant difference in the number of metastatic nodes in the lungs.

CONCLUSIONS

Thalidomide alone delayed tumor growth, but the combination of thalidomide with OncdSyn appeared to produce the best results.

Thalidomide: mechanisms of action

The classification of thalidomide as an orphan drug with anti-inflammatory actions has led to its off-label use in conditions refractory to other medications. Although the observed clinical effects of thalidomide suggest it to have immunomodulatory capabilities, the mechanism of action is unclear. Here we review both the positive and negative studies of thalidomide at the bench in order to improve our understanding of the possible mechanisms of this drug in treating a variety of diseases at the bedside. Studies on the effects of thalidomide on the innate and adaptive immune system as well as tumorigenesis and angiogenesis are discussed.

Thalidomide suppressed interleukin-6 but not tumor necrosis factor-alpha in volunteers with experimental endotoxemia

An early rationale for using thalidomide to treat erythema nodosum leprosum had been based on some reports that it suppresses tumor necrosis factor-alpha (TNF-alpha). However, in vivo and in vitro studies have yielded variable results, having shown that thalidomide can either enhance or suppress TNF-alpha. Since the course of circulating cytokines like TNF-alpha after infusion of endotoxin into volunteers is reproducible and characteristic, we investigated the effect of thalidomide on endotoxin-induced synthesis of TNF-alpha, interleukin (IL)-6, and IL-8. The cytokine response from 18 placebo-treated subjects who had undergone the endotoxin challenge were pooled with a placebo-treated subject from the current study and were compared with 4 subjects who received thalidomide (100 mg) every 6 h for 5 doses before endotoxin challenge. Thirty minutes after the last dose of thalidomide or placebo, volunteers were infused with 4-ng/kg endotoxin. Plasma was collected and assayed for cytokines by enzyme-linked immunosorbent assay. Endotoxin evoked the synthesis of the cytokines in all volunteers. The peak response for TNF-alpha was 1.5 h, 2.5 h for IL-8, and 3.0 h for IL-6. Thalidomide did not significantly delay the release of cytokines into the circulating blood. At the peak response, thalidomide reduced the concentration of the cytokines in the plasma. Using the area under the dose response curve (AUC(0 to 24) h), thalidomide reduced the AUC for IL-6 by 56%, for IL-8 by 30%, and TNF-alpha by 32%. In this model, thalidomide did not suppress TNF-alpha or IL-8, but it did suppress IL-6 at 4-h postinfusion with lipopolysaccharide (P=0.004), at 6 h (P=0.014), at 12 h (P=0.001), and at 16 h (P=0.012).

The continuing challenges of leprosy

Leprosy is best understood as two conjoined diseases. The first is a chronic mycobacterial infection that elicits an extraordinary range of cellular immune responses in humans. The second is a peripheral neuropathy that is initiated by the infection and the accompanying immunological events. The infection is curable but not preventable, and leprosy remains a major global health problem, especially in the developing world, publicity to the contrary notwithstanding. Mycobacterium leprae remains noncultivable, and for over a century leprosy has presented major challenges in the fields of microbiology, pathology, immunology, and genetics; it continues to do so today. This review focuses on recent advances in our understanding of M. leprae and the host response to it, especially concerning molecular identification of M. leprae, knowledge of its genome, transcriptome, and proteome, its mechanisms of microbial resistance, and recognition of strains by variable-number tandem repeat analysis. Advances in experimental models include studies in gene knockout mice and the development of molecular techniques to explore the armadillo model. In clinical studies, notable progress has been made concerning the immunology and immunopathology of leprosy, the genetics of human resistance, mechanisms of nerve injury, and chemotherapy. In nearly all of these areas, however, leprosy remains poorly understood compared to other major bacterial diseases.

Dermatologic and nondermatologic uses of thalidomide

OBJECTIVE

To review published data on thalidomide, with emphasis on current knowledge about mechanism of action, new and/or potential dermatologic and nondermatologic therapeutic applications, well-known and emerging adverse effects, and current indications for its safe use.

DATA SOURCES

Review articles, in vitro research studies, references from retrieved articles, case reports, and clinical trials were identified from a computerized literature search using MEDLINE and OVID (1966-January 2003) and on the Cochrane Clinical Trials Register (January 2003). Information available from meetings' abstract books, Internet, or pharmaceutical companies was also considered.

STUDY SELECTION AND DATA EXTRACTION

All articles identified as relevant, including those from non-English literature, were considered in an attempt to provide to the reader both the theoretical basis and practical guidelines for thalidomide pharmacotherapy.

DATA SYNTHESIS

Thalidomide has hypnosedative, antiangiogenic, antiinflammatory, and immunomodulatory properties. Moreover, it has been shown to selectively inhibit the production of tumor necrosis factor-alpha and reduce the expression of various integrin receptors on the membrane of leukocytes and other cell types in a dose-dependent fashion. Controlled trials demonstrated the efficacy of thalidomide in a number of diseases, including erythema nodosum leprosum, lupus erythematosus, aphthosis, graft-versus-host disease, prurigo nodularis, and actinic prurigo. Single case reports or studies in small series have also suggested a possible role for thalidomide in numerous other dermatologic and nondermatologic disorders. Possibly severe and sometimes irreversible risks related to the clinical use of thalidomide include teratogenicity and neurotoxicity.

CONCLUSIONS

Although teratogenicity and neurotoxicity are significant adverse effects requiring cautious use, thalidomide is an effective therapeutic modality in a variety of difficult-to-treat disorders and, providing careful selection of patients, should offer an acceptable risk-to-benefit ratio.

Theoretical basis for the activity of thalidomide

The revival of thalidomide began shortly after the drug was withdrawn from the market because of its teratogenic properties. Therapeutic effects of thalidomide were found accidentally in leprosy patients with erythema nodosum leprosum (ENL). Subsequent research widened the understanding of the activity of thalidomide, and with improved methodology and the augmented background knowledge of immunology it was possible to interpret the properties of thalidomide more coherently. Effects on tumour necrosis factor-alpha (TNFalpha) release play an important role in the ability of thalidomide to affect the immune system. Alteration of synthesis and release of cytokines such as interleukin (IL)-1, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12 and interferon-gamma is involved in the complex mechanisms of thalidomide. Thalidomide targets leucocytes, endothelial cells and keratinocytes, affecting them in a different manner and at different cellular levels. Changes in the density of adhesion molecules alter leucocyte extravasation and the inflammatory response in the tissue involved. Several mechanisms for the teratogenic action of thalidomide are currently under review, but this mode of action of the drug still remains unclear and we review evidence-based hypotheses for the teratogenicity of thalidomide. Thalidomide shows significant clinical impact in several diseases such as ENL in lepromatous leprosy, chronic graft-versus-host disease, systemic lupus erythematosus, sarcoidosis, aphthous lesions in HIV infection, wasting syndrome in chronic illness, inflammatory bowel disease, multiple myeloma and some solid tumours. In 1998 the US Food and Drug Administration approved thalidomide exclusively for the treatment of ENL, and strict conditions were stipulated for its use in order to prevent teratogenic adverse effects. However, despite the promising findings of thalidomide at the molecular level, namely its anti-TNFalpha properties and its intercalation with DNA, and activity in clinical trials, there is still a great need for more intensive research.

Update on therapy--thalidomide in the treatment of lupus

Thalidomide has been shown to be an effective treatment for cutaneous forms of lupus erythematous refractory to other therapies. Thalidomide has very serious side effects, including teratogenicity and neuropathy, which limit its clinical use in lupus to such severe refractory cases. Efficacy has been confirmed in several studies, although recurrence after discontinuation of treatment is frequent. More recent experience suggests that lower doses than originally used may be effective, which may result in a reduction in side effects. Much effort has been expended in studying the mechanisms of action of thalidomide, although as yet it is unclear which of the mechanisms identified to date contribute to its efficacy in treating cutaneous forms of lupus erythematosus. Identification of patients suitable for thalidomide therapy requires a rigorous selection process. Potential side effects should be clearly explained, particularly teratogenicity as many patients are young women. Written consent and a negative pregnancy test must be obtained prior to commencement of therapy. Reliable contraceptive measures should be strictly observed by patients taking thalidomide. Close clinical and neurophysiological supervision using nerve conduction studies should be undertaken.

Thalomid (Thalidomide) capsules: a review of the first 18 months of spontaneous postmarketing adverse event surveillance, including off-label prescribing

The sedative/hypnotic thalidomide was withdrawn from the worldwide market nearly 40 years ago, because of its teratogenic and neurotoxic effects. Thalidomide was later found to very effectively suppress erythema nodosum leprosum (ENL). The US Food and Drug Administration (FDA) has approved Thalomid (thalidomide) capsules for the acute treatment of the cutaneous manifestations of moderate to severe ENL. Thalidomide is currently under investigation for the treatment of a wide variety of diseases, including conditions thought to have an inflammatory or immune basis, malignancies and complications of infection with HIV. Interest in the potential anti-inflammatory, immunomodulatory and anti- angiogenic effects of thalidomide has resulted in off-label use of prescription thalidomide. During the first 18 months of spontaneous postmarketing adverse event surveillance for Thalomid, 1210 spontaneous postmarketing adverse event reports were received for patients treated with prescription thalidomide for all therapeutic indications, including off-label use. The most common adverse events spontaneously reported would have been expected on the basis of the current Thalomid labelling/product information. The current labelling/product information reflects what was known about the risks associated with thalidomide therapy in limited patient populations at the time of the approval of Thalomid. With the postmarketing use of thalidomide in populations other than patients with ENL, it becomes increasingly important to identify patient groups that may be particularly susceptible to specific adverse drug effects and to identify conditions under which specific adverse events may be more likely to occur. Oncology patients may represent a patient population with increased susceptibility to thalidomide-associated adverse effects, including thromboembolic events. Consideration of the spontaneous postmarketing safety surveillance data may help to identify and characterise factors associated with increased risk in this and other patient groups. Serious unexpected adverse events reported with sufficient frequency to signal previously undetected product-event associations for which there may potentially be plausible evidence to suggest a causal relationship have included seizures and Stevens-Johnson syndrome. The potential effects of thalidomide on wound healing are also being closely monitored. Premarketing human clinical trials of drug products are inherently limited in their ability to detect adverse events. Broader postmarketing experience with thalidomide in more varied patient populations and more experience in the setting of long term thalidomide use will increase our ability to detect rare adverse events and to identify signals that may need to be evaluated in more controlled settings.

Potential novel uses of thalidomide: focus on palliative care

Thalidomide, after being banned from the market in the early 1960s because of the worldwide teratogenesis disaster, is currently being rediscovered because of its multiple therapeutic effects in various serious diseases and symptoms. Original studies examined the anxiolytic, mild hypnotic, anti-emetic and adjuvant analgesic properties of this drug. Subsequently, thalidomide was found to be highly effective in managing the cutaneous manifestations of leprosy (erythema nodosum leprosum) and even to be superior to aspirin (acetylsalicylic acid) in controlling leprosy-associated fever. Recent research shows promising results with thalidomide in patients with progressive bodyweight loss related to advanced cancer and HIV infection. Thalidomide therapy of diseases such as tuberculosis, sarcoidosis, aphthous ulcers in HIV syndrome and Behcet's disease, rheumatoid arthritis, multiple myeloma, graft-versus-host disease, pyoderma gangrenosum, inflammatory bowel disease, Sjögren's syndrome, lupus erythematosus and a variety of solid tumours is currently being explored. Furthermore, in preliminary studies, thalidomide has been found to be effective in several syndromes related to advanced cancer, such as the cancer cachexia syndrome, chronic nausea, insomnia, profuse sweating and pain. Whether thalidomide has a therapeutic effect on neoplastic fever has yet to be elucidated. These intriguing features make the use of the drug potentially attractive for palliative care. In addition, by a distinct mechanism of action compared with most other drugs, thalidomide offers the possibility of combined treatment with other agents with non-overlapping toxicities. The mechanism of action of thalidomide is probably based on the suppression of tumour necrosis factor-alpha and the modulation of interleukins. However, it is not possible to identify a single dominant mechanism, since the action of cytokines and the effect of thalidomide appear to be complex. This review article discusses the original uses and teratogenic effects of thalidomide within its historical context and, linking recent research at the molecular level with clinical findings, aims to provide the reader with insight into the current understanding of its biological actions, toxicities and potential benefits.

Lack of in vitro antimicrosporidian activity of thalidomide

Thalidomide was evaluated for its in vitro activity against Encephalitozoon species by using the MRC-5 cell system. A cytotoxic effect was observed for concentrations of 10(1) microg/ml (P < 10(5)) and 5 microg/ml (P < 10(5)). Thalidomide did not significantly inhibit the growth of any of the microsporidia under study. These data suggest that thalidomide is not an etiologic treatment in microsporidial enteritis.

Immunomodulatory assays to study structure-activity relationships of thalidomide

Thalidomide, which has a long history of tragedy because of its ability to cause severe birth defects, is very effective in alleviating erythema nodosum leprosum in leprosy patients and aphthous ulcers in AIDS patients. The causes of these inflammatory diseases and the mechanism by which thalidomide diminishes them are unknown. It has been suggested that modulation of the immune response plays an important role. We found that thalidomide exerts immunomodulatory activity in three bioassays. It suppresses an IgM plaque forming cell response in mice injected with sheep erythrocytes: it inhibits TNF-alpha production by LPS stimulated human mononuclear cells: and it enhances IL-2 production by Con-A stimulated human mononuclear cells. We employed these bioassays to compare the activity of 15 analogs of thalidomide with thalidomide itself. Eight of the compounds were derivatives of the glutarimide moiety of thalidomide and the others were phthalimide or derivatives of the phthalimide moiety of thalidomide. N-hydroxyphthalimide, a simple derivative of phthalimide, was more effective than thalidomide and was also the most effective of the compounds assayed in suppressing the IgM plaque and TNF-alpha responses, but it did not enhance the IL-2 response, instead, it significantly suppressed it.

Rediscovering thalidomide: a review of its mechanism of action, side effects, and potential uses

Thalidomide, a hypnosedative drug introduced in the 1950s, has been used in a variety of dermatologic conditions during the past few decades. Although originally withdrawn from the world market on discovery of its teratogenic effect, it has since been selectively reintroduced for use in various disorders thought to have an autoimmune or inflammatory basis. A review of the literature focused on clinical uses of thalidomide in the treatment of dermatologic diseases was performed. Diseases for which thalidomide has been found effective include erythema nodosum leprosum, prurigo nodularis, actinic prurigo, discoid lupus erythematosus, aphthous stomatitis, Behçet's syndrome, and graft-versus-host disease. Side effects such as teratogenicity and peripheral neuropathy remain its limiting factor. Thalidomide is a useful addition to the therapeutic armamentarium for treatment-resistant dermatoses as long as proper vigilance for adverse effects is maintained.

Immunostimulatory effect of thalidomide in normal C57BL/6 mice is compatible with stimulation of a highly connected central immune system

Although thalidomide has been used with success in the treatment of increasing numbers of autoimmune diseases, the therapeutic effects have not been satisfactorily explained so far. We describe here some findings that may contribute to a better understanding of the immunomodulatory effects of this drug. Several immunological changes were observed after treating C57BL/6 mice with 3 mg of thalidomide. The numbers of natural IgM PFC against sheep red blood cells were increased in the spleen, and occasionally a dramatic oscillatory increase in the numbers of non-specific splenic IgM and IgG PFC was observed in these mice. However, these oscillatory increases were progressively lower, after two and three treatments with thalidomide at 20-day intervals. Furthermore, the absolute numbers of splenic CD5+ B and CD5- B lymphocytes were increased whereas depletion of CD4+ CD8+ cells in the thymus and of lymphoid cells in the bone marrow was seen after a single treatment with 3 mg of thalidomide. Taken together, these results suggest that thalidomide stimulates both peripheral and central immune systems and consequently enhances the connectivity of the central immune system.

Thalidomide does not perturb CD2, CD4, CD5, CD8, HLA-DR, or HLA-A, B, C molecules in vitro on the membranes of cells with immune potential

Thalidomide dramatically relieves the signs and symptoms of erythema nodosum leprosum (ENL). ENL is an acute inflammatory complication of lepromatous leprosy. The cause(s) of ENL as well as the mechanism of action of thalidomide in arresting ENL are unknowns. It has been suggested that ENL is the consequence of a transient activation of a cell-mediated-immune (CMI) response to Mycobacterium leprae. To initiate a CMI response, an interaction between adhesion and/or signal transducing molecules on T-cells and molecules on antigen presenting cells would occur. An alteration, induced by thalidomide, of one or more of the molecules on T-cells or antigen presenting cells that are essential to maintaining the reactive state of ENL, could explain Thalidomide's ability to attenuate ENL. Thalidomide did not modify: (a) adhesion and/or signal transducing molecules such as CD2, CD4, CD5 and CD8, or (b) molecules that facilitate antigen presentation such as HLA-DR, HLA-A, HLA-B, or HLA-C.

The thalidomide analog, EM 12, enhances 1,2-dimethylhydrazine-induction of rat colon adenocarcinomas

Young male Sprague-Dawley rats in 3 groups were fed a basal diet supplemented with 0.10 wt. % each of thalidomide and its imide-analog of much higher teratogenicity, EM 12. Following an induction period of 17 days on the diets, all animals were injected subcutaneously with 1,2-dimethylhydrazine at 20 mg/kg for a total of 20 weekly doses and killed on week 18 after the 20th injection. The total number of colon adenocarcinomas and their occurrence in the proximal and distal portions for the thalidomide-treated rats were similar to those of the respective controls. However, the EM 12-fed group elicited statistically significant increases both in the total and ascending colon-based adenocarcinomas as compared with the control findings, in keeping with its greater teratogenicity and embryotoxicity. The numbers of small intestinal adenocarcinomas were equally higher in the imide-fed groups in contrast to the control frequency.

Thalidomide treatment for chronic graft-versus-host disease

The treatment of chronic graft-versus-host disease (GVHD) may present a difficult therapeutic problem. We used thalidomide to treat six patients with severe chronic GVHD who failed to respond to standard immunosuppressive agents. Four of the six patients showed a clear response to thalidomide, with the fifth patient showing a partial response. The best results were seen in patients with chronic cutaneous GVHD. Two of the patients developed neurophysiological evidence of a peripheral neuropathy, associated with clinical signs in one patient. Measurement of thalidomide plasma levels and pharmacokinetic curves showed a significant inter-patient variation. Peak plasma levels varied from 0.47 to 1.46 micrograms/ml. Thalidomide has a role to play in the management of chronic GVHD and further studies are needed.

Thalidomide in the treatment of graft-versus-host disease

The success of allogeneic bone marrow transplantation has been restricted by the occurrence of graft-versus-host disease (GVHD). Attempts at prevention and treatment of GVHD have resulted in only a limited improvement and the morbidity and mortality rate remains high. Thalidomide has been known to have immunosuppressive properties for over 20 years, but it has only recently been used in GVHD. Evidence is now accumulating as to its value both in animal models, and in humans where most benefit has been seen in chronic GVHD. We report our experience using thalidomide in GVHD following allogeneic bone marrow transplantation and review the literature.

The effect of thalidomide on experimental autoimmune myasthenia gravis

Thalidomide is reported to have immunosuppressive and anti-inflammatory effects which have led to its use in the treatment of a number of immune-mediated disorders including leprosy, prurigo, discoid lupus, and Behcet's disease. In addition, thalidomide has recently been used to prevent immunological rejection phenomena following skin and bone-marrow grafts. The immune responses in these conditions are thought to be cell-mediated. However, little is known about the effectiveness of thalidomide in suppressing antibody-mediated immune responses. In the present study, we have examined the effect of thalidomide in a model antibody-mediated autoimmune disorder--experimental autoimmune myasthenia gravis (EAMG). To induce EAMG, Lewis rats were immunized with acetylcholine receptor (AChR) purified from the electric organ of Torpedo californicus. Groups of rats were treated daily, either with thalidomide in excess of doses reported to prevent graft-versus-host (GVH) disease in bone-marrow-transplanted rats, or with control treatments. Our results show that thalidomide failed to inhibit AChR antibody production despite good absorption and high blood levels of the drug. This suggests that thalidomide is not likely to be generally useful in the treatment of antibody-mediated autoimmune conditions. However the selective effect of thalidomide in suppressing certain presumably cellular immune responses, while sparing antibody production, is inherently interesting, and merits further study.

Enhancement of antibody response and delayed-type hypersensitivity by thalidomide in mice

Renewed interest in thalidomide stemmed from the suggestion by several authors that it might prove useful against immune-related diseases. Despite interesting preliminary findings, little is actually known regarding its immunoenhancing properties in vivo. Male and female Swiss mice, aged 6-8 wk, were given 0.5 or 25 mg/kg/day of thalidomide orally for 4 wk. Various immunological parameters were then assessed. When compared to controls, mice exposed to the higher dose presented with a significantly increased thymus weight index, whereas spleen weight index remained unchanged. Anti-sheep erythrocyte plaque-forming cells and hemagglutinin titers were increased by 44% and 29%, respectively. Contact hypersensitivity to picryl chloride was enhanced by 62%. Finally, colloidal carbon clearance was not altered. Interestingly, the lower dose (5 mg/kg/day) exerted no effect whatsoever.

IgM and IgG antibodies to phenolic glycolipid I from Mycobacterium leprae in leprosy: insight into patient monitoring, erythema nodosum leprosum, and bacillary persistence

Serum IgM and IgG antibodies against Mycobacterium leprae-derived phenolic glycolipid I (PG) were determined in leprosy patients, contacts, and controls by enzyme-linked immunosorbent assay (ELISA). Anti-PG IgM levels increased from the tuberculoid (TT) to the lepromatous (LL) pole of the disease spectrum. There was a positive linear correlation between anti-PG IgM and bacillary index (BI). Patients with erythema nodosum leprosum (ENL) had lower levels of serum anti-PG IgM than non-ENL patients of comparable BI, suggesting that anti-PG IgM is involved in the pathogenesis of ENL. Initial observations indicate that high anti-PG IgM levels in bacillary-negative patients might reflect bacillary persistence. A study of 2 different substrate reagents in the ELISA [2,2'-azino-di(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), 0.1 mM H2O2, serum diluted 1:20, and o-phenylenediamine (OPD), 5 mM H2O2, serum diluted 1:300] showed generally good correlation in detection of anti-PG IgM. However the OPD system detected more paucibacillary disease (BT), while the ABTS system detected the significant effect of ENL on the relationship between BI and anti-PG IgM. Anti-PG IgM was clearly dominant over anti-PG IgG. However, certain patients, including several patients who had upgraded from LL and borderline lepromatous leprosy (BL), showed high levels of anti-PG IgG. Since studies have shown that LL patients are selectively deficient in cell-mediated immunity, T-cell products may be required for the IgM to IgG isotype switch. We conclude that anti-PG IgM is useful for monitoring the bacillary load in individual patients and should prove useful for leprosy control strategies.

[Effect of thalidomide on serum levels of immunoglobulins IgM and IgA, rheumatoid factor and isohemagglutinins anti-A and anti-B in patients with lepromatous leprosy. A double-blind study]

Um estudo duplo-cego foi conduzido em pacientes portadores de lepra lepromatosa estável, para avaliar a resposta à administração de talidomida 100 mg por dia, por 18 dias, dos níveis séricos de IgM e IgA e dos títulos de fator reumatóide e isohemaglutininas anti-A e anti-B. Nenhum efeito significativo foi detectado ao fim deste período.

Thalidomide therapy. An open trial

In an open trial, 35 patients suffering from a variety of dermatologic conditions were treated with thalidomide. The drug was shown to be a valuable addition to the therapeutic armamentarium; however, the occurrence of a peripheral neuropathy will limit its use just as its teratogenic side effects have done for many years.

Differential inhibition of protein synthesis: a possible biochemical mechanism of thalidomide teratogenesis

A theory concerning the chemical and biochemical mechanisms of thalidomide teratogenesis is presented. A considerable body of evidence suggests that the glutarimide ring of thalidomide may exert its biological activity because of its resemblance to the imide pyrimidines thymine and uracil. In addition to the glutarimide ring, thalidomide contains a moderately reactive phthalimide moiety, which allows the spontaneous formation of various glutarimide derivatives in fetal tissues. A model is proposed in which the phthalimide group reacts with small nucleophiles, most likely the polyamines, to produce a derivative(s) having a similar biochemical potential to that of cycloheximide, a glutarimide which is a powerful inhibitor of the elongation phase of protein synthesis. Interference in the elongation phase results in the selective inhibition of the translation of messages which have a high translational efficiency. Evidence is reviewed concerning the differential inhibition or protein synthesis by cycloheximide and the effects of this inhibition on various biochemical and biological processes which are critical during development and differentiation. A similar biochemical activity by the putative thalidomide derivative(s) could explain its extreme teratogenic potential. A number of parallels between the biological effects of thalidomide and cycloheximide are discussed which support the idea that a similar biochemical activity is involved. The theory readily explains many of the observed biological effects of thalidomide including the large difference between fetal and adult toxicity. In addition, evidence is reviewed which suggests that the teratogenic properties of a number of drugs which are structurally related to thalidomide may have a common chemical basis due to the similarity of their imide core structures to thymine and uracil.

Teratogen metabolism: activation of thalidomide and thalidomide analogues to products that inhibit the attachment of cells to concanavalin A coated plastic surfaces

Thalidomide metabolites inhibited the attachment of tumor cells to concanavalin A coated polyethylene surfaces. Thalidomide, itself, was non-inhibitory. Thalidomide activation to inhibitory products required hepatic microsomes, an NADPH-generating system, and molecular oxygen. Production of inhibitory metabolites was unaffected by either epoxide hydrolase or 1,2-epoxy-3,3,3-trichloropropane (TCPO), an inhibitor of epoxide hydrolase endogenous to hepatic S9 fraction. Therefore, the attachment inhibitor was probably not an arene oxide. Inhibition was not accompanied by cytotoxicity, as judged by trypan blue exclusion. Although uninduced hepatic microsomes from mice, rats and dogs had similar abilities to activate thalidomide, microsomes from Aroclor 1254 induced rats were relatively inactive in the system. Inhibitory metabolites were generated from the thalidomide analogues EM8 , EM12 , EM16 , EM87 , EM136 , EM255 , E350 , phthalimide, phthalimido-phthalimide, indan, 1- indanone and 1,3- indandione . Glutarimide , glutamic acid and phthalic acid did not activate to inhibitory products.