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PubMed2001

Bexarotene metabolism in rat, dog, and human, synthesis of oxidative metabolites, and in vitro activity at retinoid receptors.

The metabolism of bexarotene, a rexinoid recently approved in the United States for treatment of cutaneous T-cell lymphoma, was studied using liver slices from untreated rats and dogs, liver microsomes from untreated and pretreated rats, and pooled human liver microsomes. Metabolite profiles were examined in bile and plasma from rats and dogs, and plasma from humans treated with bexarotene. Four metabolites, racemic 6-hydroxy-bexarotene, racemic 7-hydroxy-bexarotene, 6-oxo-bexarotene, and 7-oxo-bexarotene, were synthesized and their binding to, and transactivation of retinoid receptors were examined. Qualitatively similar metabolite profiles were observed in the microsomal and liver slice extracts; the predominant metabolites were 6-hydroxy-bexarotene and glucuronides of parent or hydroxylated metabolites. Pretreatment of rats with bexarotene induced hepatic microsomal bexarotene metabolism. The hydroxy and oxo metabolites were observed in plasma of rats, dogs, and humans treated with bexarotene and 6-hydroxy-bexarotene was a major circulating metabolite. The oxidative metabolites were more abundant relative to parent in plasma from humans than from rat or dog. The predominant biliary metabolites in rat and dog were bexarotene acyl glucuronide and a glucuronide of oxidized bexarotene, respectively. Since bexarotene elimination is primarily biliary in these species, these metabolites represent the main bexarotene metabolites in rats and dogs. The binding of synthetic metabolites to retinoid receptors was much reduced relative to parent compound. The metabolites exhibited minimal activity in transactivating retinoic acid receptors and had reduced activity at retinoid X receptors relative to bexarotene. Thus, while there is substantial systemic exposure to the oxidative metabolites of bexarotene, they are unlikely to elicit significant retinoid receptor activation following bexarotene administration.

Animals↗
PubMed2002

Optimizing bexarotene therapy for cutaneous T-cell lymphoma.

BACKGROUND: Bexarotene (Targretin oral capsules), the first RXR-selective retinoid "rexinoid" approved for all stages of cutaneous T-cell lymphoma (CTCL), had a response rate (RR) of 45% at the optimal dose of 300 mg/m(2) per day in 2 multicenter trials. With hypertriglyceridemia reported at 79%, bexarotene is often administered with lipid-lowering agents (LLAs). Statins (inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase) may modulate class II major histocompatibility class expression and T-cell responses. OBJECTIVE: We attempted to optimize the clinical response to bexarotene by controlling dose-limiting hypertriglyceridemia and combining bexarotene with other active agents. METHODS: We prospectively evaluated 70 patients with CTCL at M. D. Anderson Cancer Center who were treated with oral bexarotene as monotherapy or in combination with other active agents. RESULTS: Fifty-four patients receiving bexarotene monotherapy achieved an overall RR of 48%. Thirteen had stage IA-IIA disease (RR = 53%, 1 complete response [CR]); 41 had stage IIB-IVB disease (RR = 46%, 2 CRs). Forty-two (77%) of these also required one or more LLAs: atorvastatin (n = 29, RR 43%), atorvastatin plus fenofibrate (n = 10, RR 90%), or gemfibrozil (n = 3, RR 33%). Gemfibrozil was discontinued because it increased bexarotene and triglyceride levels. Patients taking 2 LLAs had a significantly higher RR of 90% during monotherapy than those taking one or no LLAs (P <.0001). Forty of 54 patients (74%) received thyroid hormone replacement to normalize thyroxine levels. Four patients receiving monotherapy have complete CRs of >3 years' duration and received maintenance dosing. Sixteen patients with advanced disease treated with bexarotene (225-750 mg/d) in combination with other CTCL therapies achieved an overall RR of 69% (11/16) with concomitant statin therapy. Bexarotene was safely combined with psoralen ultraviolet A (PUVA) plus interferon alfa (IFN-alpha) (n = 2, RR = 50%), with extracorporeal photopheresis (ECP) (n = 8, RR = 75%, 1 CR), with ECP/IFN-alpha (n = 4, RR =50%), with ECP/IFN-alpha/PUVA (n = 1, RR = 100%), and with IFN-alpha/PUVA/topical nitrogen mustard (n = 1, RR = 100%). Two patients receiving IFN-alpha had slight leukopenia, but rhabdomyolysis associated with multiple LLAs did not occur. CONCLUSION: This single-center study supports the safety and efficacy of bexarotene as both a monotherapy and a combination therapy for CTCL. Long durable CRs may be achieved with oral monotherapy. Use of statins with bexarotene may also increase RRs by permitting higher doses to be administered without interruption, by modulating the immune response, or both. When bexarotene is combined with other active CTCL therapies, higher RRs were achieved in patients with advanced disease, without unacceptable side effects.

Algorithms↗
PubMed2001

Placebo-controlled trial of bexarotene, a retinoid x receptor agonist, as maintenance therapy for patients treated with chemotherapy for advanced non-small-cell lung cancer.

This study was designed as a multicenter, randomized, double-blind, placebo-controlled trial. Patients were randomized by center to placebo (16 patients, 31%), oral bexarotene 300 mg/m2/day (21 patients, 40%), or oral bexarotene 600 mg/m2/day (15 patients, 29%) following demonstration of stable or responsive disease after first-line chemotherapy. The study was prematurely terminated because of slow accrual after 54 patients enrolled. Median time to progression (TTP) from the beginning of study drug treatment was 56 days for placebo, 82 days for moderate-dose bexarotene (300 mg/m2/day), and 128 days for high-dose bexarotene (600 mg/m2/day) (P = 0.56, log-rank test). For prior chemotherapy responders only, median TTP from the beginning of study drug treatment was 56 days for placebo, 146 days for moderate-dose bexarotene, and 177 days for high-dose bexarotene. Of note, there were more chemotherapy responders randomized to the placebo group (63%) than the bexarotene treatment arms (48% and 47%), further supporting a bexarotene-related improvement in TTP. Bexarotene-related toxicity was manageable and consisted primarily of elevated serum triglycerides and asthenia, skin toxicity (dryness, peeling, flaking), thyroid dysfunction, and headache. Because this study was closed prematurely, it does not have the statistical power to detect differences among the treatment groups. This study shows that patients can tolerate bexarotene at initial doses up to 600 mg/m2/day after platinum-based chemotherapy and that bexarotene may have the potential to delay disease progression in patients with advanced non-small-cell lung cancer with previously stable or responsive disease following platinum-based chemotherapy.

Clinical Trial↗
PubMed2005

Biological effects of bexarotene in cutaneous T-cell lymphoma.

OBJECTIVE: To determine the effects of bexarotene on malignant T cells isolated from the peripheral blood of patients with the leukemic variant of cutaneous T-cell lymphoma (Sézary syndrome). DESIGN, SETTING, AND PARTICIPANTS: Peripheral blood mononuclear cells from 9 patients with Sézary syndrome and a high burden of circulating malignant T cells (>50% of peripheral blood mononuclear cells) and 6 healthy volunteers underwent evaluation at a university medical center, to test the effects of bexarotene on T cells. MAIN OUTCOME MEASURES: The capacity of bexarotene to induce apoptosis and its effects on T-cell cytokine production from peripheral blood lymphocytes isolated from patients with Sézary syndrome. RESULTS: Bexarotene produced dose-dependent apoptosis of peripheral blood T cells from patients with Sézary syndrome. The T cells from approximately two thirds of patients were consistently sensitive to bexarotene, whereas those from the remaining one third of patients were consistently resistant to the apoptotic effects of bexarotene. Bexarotene inhibited mitogen-induced interleukin 4 production by the peripheral blood cells of patients with Sézary syndrome, and this effect correlated with sensitivity of patients' cells to apoptosis. In contrast to the retinoic acid receptor-specific retinoid, all-trans retinoic acid, bexarotene does not induce the augmentation of interferon gamma production. CONCLUSIONS: Bexarotene induces apoptosis of malignant T cells from patients with Sézary syndrome, but the cells from a proportion of patients are resistant to the apoptotic effects. Interleukin 4 production, which can play a role in the systemic immunosuppression that characterizes advancing Sézary syndrome, may be inhibited by bexarotene.

Apoptosis↗
PubMed2004

A phase II multicenter clinical trial of systemic bexarotene in psoriasis.

BACKGROUND: Bexarotene, a novel and unique synthetic P, RXR-selective retinoid, is available as a treatment for cutaneous T-cell lymphoma. In psoriasis, a common retinoid-sensitive disease, no data are available on bexarotene treatment. OBJECTIVE: In this phase II study we investigated the safety, tolerability, and effectiveness of bexarotene in psoriasis at doses of 0.5 to 3.0 mg/kg/day. METHODS: Fifty patients with moderate to severe plaque-type psoriasis were treated with bexarotene in 4 sequential dose-defined panels of 12-13 patients at doses of 1.0, 2.0, 0.5, and 3.0 mg/kg/day for 12-24 weeks. Patients were monitored for safety and clinical efficacy. RESULTS: No serious adverse events related to the drug occurred. Bexarotene was well tolerated in most patients. Most frequently observed adverse events related to bexarotene were hypertriglyceridaemia (56%) and a decrease in free T4 serum levels (54%). Significant improvement of psoriasis after bexarotene at all doses was confirmed by a modified psoriasis area and severity index (mPASI), plaque elevation (PEL), and physician's global assessment (PGA). Overall response rates (> or =50% improvement) for mPASI, PEL, and PGA were 22%, 52%, and 36%, respectively. No significant dose-response effect was established for these parameters. CONCLUSION: The present study indicates an anti-psoriatic effect of bexarotene. Further studies are necessary to assess the optimal dose and the potential for bexarotene as a new therapy for psoriasis.

Adult↗
PubMed2006

A selective retinoid X receptor agonist bexarotene (LGD1069, targretin) inhibits angiogenesis and metastasis in solid tumours.

The present study determined the influence of a retinoid X receptor agonist bexarotene on angiogenesis and metastasis in solid tumours. In the experimental lung metastasis xenograft models, treatment with bexarotene inhibited the development of the lung tumour nodule formation compared to control. In vivo angiogenesis assay utilising gelfoam sponges, bexarotene reduced angiogenesis in sponges containing vascular endothelial growth factor, epidermal growth factor and basic fibroblast growth factor to various extent. To determine the basis of these observations, human breast and non-small-cell lung cancer cells were subjected to migration and invasion assays in the presence of bexarotene. Our data showed that bexarotene decrease migration and invasiveness of tumour cells in a dose-dependent manner. Furthermore, bexarotene inhibited angiogenesis by directly inhibiting human umbilical vein endothelial cell growth and indirectly inhibiting tumour cell-mediated migration of human umbilical vein endothelial cells through Matrigel matrix. Analysis of tumour-conditioned medium indicated that bexarotene decreased the secretion of angiogenic factors and matrix metalloproteinases and increased the tissue inhibitor of matrix metalloproteinases. The ability of bexarotene to inhibit angiogenesis and metastasis was dependent on activation of its heterodimerisation partner peroxisome proliferator-activated receptor gamma. Collectively, our results suggest a role of bexarotene in treatment of angiogenesis and metastasis in solid tumours.

Animals↗
PubMed2003

A multiparameter flow cytometric analysis of the effect of bexarotene on the epidermis of the psoriatic lesion.

BACKGROUND: A new retinoid, bexarotene (Targretin), was recently investigated in a large multicentre trial for its efficacy and safety in psoriasis. Bexarotene is a novel retinoid X receptor (RXR)-selective ligand. OBJECTIVES: The aim was to study the effect of bexarotene in psoriasis by analysing markers for epidermal differentiation, proliferation and inflammation in epidermal single cell suspensions from lesions of patients with psoriasis treated with various doses of bexarotene. METHODS: Thirty-four patients with moderate to severe plaque psoriasis participated in this study and were assigned in sequence to four different dose regimens: 0.5, 1, 2 and 3 mg kg-1 once daily. Before and after 12 weeks of bexarotene treatment, punch biopsies were taken from lesional skin from which epidermal single cell suspensions were prepared using an optimized thermolysin protocol. A sum of scores was determined for each biopsy site, based on a four-point scale for erythema, induration and desquamation. An improved multiparameter flow cytometric assay was used that enabled simultaneous assessment of epidermal proliferation, various aspects of differentiation and epidermal inflammation. The following variables were measured simultaneously: relative DNA content, relative cell size, keratin (K) 10, K6 and vimentin expression. RESULTS: The psoriasis area and severity index (PASI) and sum of scores for the individual psoriatic lesion each showed a statistically significant decrease of 28% after 12 weeks of bexarotene treatment (P < 0.001). However, no significant dose-response effect was found. The total percentage of K10+ cells showed a significant increase of 43% (P < 0.01). The total population of K6 expressing cells did not show significant changes. Regarding the subpopulations of K6 single, K10 single and K6 and 10 co-expressing cells, a significant increase of 77% was seen in the K10+ K6- cells (P < 0.05), a significant decrease of 33% in K10- K6+ cells (P < 0.01), and no significant changes in the remaining population of K10+ K6+ cells. After 12 weeks of treatment with bexarotene no significant changes in epidermal proliferation and inflammation were shown. CONCLUSIONS: The present study indicates a direct effect of RXR activation by bexarotene on the transition of proliferation-associated keratinization into normal keratinization. Although no direct effect of bexarotene on DNA content in the total K10- cells was shown, further studies on subpopulations within the germinative layer such as stem cells and transit amplifying cells might be worthwhile.

Adult↗
PubMed2002

Induction of apoptosis by bexarotene in cutaneous T-cell lymphoma cells: relevance to mechanism of therapeutic action.

PURPOSE: Bexarotene is the first synthetic rexinoid approved for the treatment of all stages of cutaneous T-cell lymphoma (CTCL) however the mechanism of bexarotene action is unknown. We examined the effects of bexarotene on induction of apoptosis and expression of its cognate receptors in well-established CTCL cell lines (MJ, Hut78, and HH). EXPERIMENTAL DESIGN: CTCL cells were treated with 0.1, 1, and 10 microM bexarotene for 24, 48, 72, and 96 h. Apoptosis was determined by flow-cytometry analysis of sub-G(1) hypodiploid nuclei and annexin V binding populations. Apoptosis-associated proteins and retinoid receptors were detected by Western blots. RESULTS: Bexarotene treatment at 1 and 10 microM for 96 h increased the number of cells with sub-G1 populations and annexin V binding in a dose-dependent manner compared with vehicle controls (DMSO) in all three cell lines, respectively. Bexarotene treatment suppressed the expression of retinoid X receptor alpha and retinoic acid receptor alpha proteins in all three lines compared with untreated controls. Bexarotene treatment decreased the protein levels of survivin, activated caspase-3, and cleaved poly(ADP-Ribose) polymerase, but had no obvious effect on expression of Fas/Fas ligand and bcl-2 proteins in all three CTCL lines. CONCLUSIONS: Bexarotene treatment at clinically relevant concentrations causes apoptosis of CTCL cell lines in association with activation of caspase-3 and cleavage of poly(ADP-Ribose) polymerase, as well as down-regulation of retinoid X receptor alpha, retinoic acid receptor alpha, and survivin. These findings support apoptosis as a mechanism for bexarotene therapy in CTCL.

Annexin A5↗
PubMed2006

Prevention of lung cancer progression by bexarotene in mouse models.

Bexarotene (Targretin), is a synthetic high-affinity RXR receptor agonist with limited affinity for RAR receptors. Bexarotene has shown efficacy in a phase I/II trial of non-small-cell lung cancers. However, the chemopreventive efficacy of bexarotene has not been determined in mouse lung cancer models. In this study, we have investigated the ability of bexarotene to inhibit lung tumor progression in the mutant A/J mouse models with genetic alterations in p53 or K-ras, two of the most commonly altered genes in human lung tumorigenesis. Mice were administered vinyl carbamate (VC), a carcinogen, by a single intraperitoneal injection (i.p.) at 6 weeks of age. Bexarotene was given by gavage starting at 16 weeks after VC and was continued for 12 weeks. Although all mice developed lung tumors, only 7% of lung tumors were adenocarcinomas in wild-type mice, whereas 22 and 26% of lung tumors were adenocarcinomas in p53 transgenic or K-ras heterozygous deficient mice. Bexarotene inhibited both tumor multiplicity and tumor volume in mice of all three genotypes. Furthermore, bexarotene reduced the progression of adenoma to adenocarcinoma by approximately 50% in both p53(wt/wt)K-ras(ko/wt) and p53(wt/wt)K-ras(wt/wt) mice. Thus, bexarotene appears to be an effective preventive agent against lung tumor growth and progression.

Adenocarcinoma↗
PubMed2006

The RXR agonist bexarotene improves cholesterol homeostasis and inhibits atherosclerosis progression in a mouse model of mixed dyslipidemia.

OBJECTIVE: The activity of the antitumoral agent bexarotene (Targretin, Bexarotene) depends on its binding to the nuclear retinoid-X receptor (RXR) and subsequent transcriptional regulation of target genes. Through RXR activation, bexarotene may modulate numerous metabolic pathways involved in atherosclerosis. Here, we investigated the effect of bexarotene on atherosclerosis progression in a dyslipidemic murine model, the human apolipoprotein E2 knockin mouse, that develops essentially macrophage-laden lesions. METHODS AND RESULTS: Atherosclerotic lesions together with different metabolic pathways involved in atherosclerosis were investigated in mice treated or not with bexarotene. Bexarotene protects from atherosclerosis development in mice, at least in part by improving the circulating cholesterol distribution profile likely via a marked decrease of dietary cholesterol absorption caused by modulation of intestinal expression of genes recently identified as major players in this process, Niemann-Pick-C1-Like1 (NPC1L1) and CD13. This atheroprotection appears despite a strong hypertriglyceridemia. Moreover, bexarotene treatment only modestly modulates inflammatory gene expression in the vascular wall, but markedly enhanced the capacity of macrophages to efflux cellular lipids. CONCLUSIONS: These data provide evidence of a favorable pharmacological effect of bexarotene on atherosclerosis despite the induction of hypertriglyceridemia, likely via a beneficial action on intestinal absorption and macrophage efflux.

ATP Binding Cassette Transporter, Subfamily G, Mem↗
PubMed2001

Multi-institutional phase I/II trial of oral bexarotene in combination with cisplatin and vinorelbine in previously untreated patients with advanced non-small-cell lung cancer.

PURPOSE: Bexarotene (Targretin; Ligand Pharmaceuticals, Inc, San Diego, CA) is a retinoid-X-receptor (RXR)-selective retinoid with preclinical antitumor activity in squamous cell cancers. In this phase I/II trial, we combined bexarotene with cisplatin and vinorelbine in the treatment of patients with non-small-cell lung cancer (NSCLC). PATIENTS AND METHODS: Forty-three patients who had stage IIIB NSCLC with pleural effusion or stage IV NSCLC and had received no prior therapy received bexarotene in combination with cisplatin (100 mg/m2) and vinorelbine (alternating doses of 30 mg/m2 and 15 mg/m2). In the phase I portion, the daily dose of bexarotene was escalated in cohorts of three patients from 150 mg/m2 to 600 mg/m2, beginning 1 week before the start of the cisplatin-vinorelbine regimen. Once the maximum-tolerated dose (MTD) of bexarotene was determined, the study entered the phase II portion. Response rate was the primary end point; median survival time and 1-year survival rate were secondary end points. RESULTS: In the phase I portion, the daily MTD of bexarotene was determined to be 400 mg/m2. Eight of 43 patients exhibited major responses. Seven (25%) of the 28 patients in the phase II portion responded to treatment. The median survival time in the phase II portion was 14 months; nine (32%) of the 28 patients were still alive at a minimum follow-up of 2 years. One-year and projected 3-year survival rates were 61% and 30%, respectively. The most common grade 3 and 4 adverse events were hyperlipemia, leukopenia, nausea, vomiting, pneumonia, dyspnea, anemia, and asthenia. Grade 3 and 4 laboratory abnormalities with incidences greater than 5% were decreased hemoglobin levels and WBC, absolute neutrophil, and absolute lymphocyte counts and increased prothrombin time and creatinine and amylase levels. Of the two cases of pancreatitis, one required hospitalization and both were associated with increased triglyceride levels. There was one death secondary to renal insufficiency unrelated to bexarotene treatment. CONCLUSION: In patients with advanced NSCLC, bexarotene with cisplatin and vinorelbine yielded acceptable phase II response rates (25%) and was associated with better-than-expected survival (14-month median survival time; 61% 1-year, 32% 2-year, and 30% projected 3-year survival rates). The regimen should be studied in larger clinical trials.

Administration, Oral↗
PubMed2006

Phase II trial of bexarotene capsules in patients with advanced non-small-cell lung cancer after failure of two or more previous therapies.

PURPOSE: To evaluate the effect of bexarotene on survival in patients with relapsed non-small-cell lung cancer (NSCLC). PATIENTS AND METHODS: Patients with stage IIIB NSCLC with pleural effusion or stage IV NSCLC, who had Eastern Cooperative Oncology Group performance status 0 to 2, and were previously treated with > or = two different regimens that must have included a platinum and a taxane, received oral bexarotene 400 mg/m2/d plus concomitant levothyroxine and a lipid-lowering agent. Primary efficacy end point was survival. RESULTS: For the 146 assessable patients treated with bexarotene, median age was 66 years (range, 34 to 87 years), 51% were men, and the median number of prior regimens was three (range, one to seven). The overall median survival was 5 months (95% CI, 4 to 7 months) and the 1-year survival was 23% (95% CI, 16% to 31%). Survival was significantly longer in patients with bexarotene-induced hypertriglyceridemia and/or skin rash. In 26 patients who had both adverse effects, the median and 1-year survival rates were 12 months (95% CI, 8 to 15 months) and 48%, respectively. In 40 patients who had neither adverse effect, median and 1-year survival rates were 2 months (95% CI, 2 to 5 months) and 15%, respectively (P = .0002). Twenty patients (14%) discontinued therapy because of bexarotene-related toxicity. For the remaining patients, adverse reactions to bexarotene were generally mild to moderate. CONCLUSION: In the intent-to-treat population, bexarotene given as third or subsequent line of therapy for relapsed NSCLC did not achieve the intended median survival of 6 months. Survival may have been extended in patients who developed bexarotene-induced hypertriglyceremia and/or skin rash. It is important to confirm these observations in a randomized controlled trial.

Administration, Oral↗
PubMedDate not supplied

Bexarotene.

Bexarotene is a selective retinoid X receptor (RXR) agonist. It binds to, and activates RXRs which function as ligand-activated transcription factors that control gene expression. This leads to modulation of cell growth, apoptosis, and differentiation. In patients with refractory or persistent early stage cutaneous T cell lymphoma (CTCL), the overall response rate was 54% after oral bexarotene 300 mg/m2/day. The overall response rate in patients with refractory or persistent advanced stage CTCL was 45% at the same dosage. An overall response rate of 63% was reported after topical bexarotene 0.1 to 1% twice daily in patients with early stage CTCL. Another trial reported an overall response rate of 44% after topical bexarotene 1% once daily escalated up to 4 times daily. Plaque elevation was significantly reduced, and the severity of moderate to severe psoriasis was substantially improved in patients receiving oral bexarotene 0.5 to 2 mg/kg/day. At clinically relevant oral dosages, bexarotene significantly decreases levels of serum thyrotropin and free thyroxine. The most common adverse events associated with oral bexarotene are hypertriglyceridemia, hypercholesterolemia, central hypothyroidism and headache. Reversible acute pancreatitis has occurred during oral bexarotene therapy. Adverse events associated with the topical formulation are limited to rash, pruritus, and pain.

Anticarcinogenic Agents↗
PubMed2004

Systemic treatment of psoriatic patients with bexarotene decreases epidermal proliferation and parameters for inflammation, and improves differentiation in lesional skin.

BACKGROUND: Bexarotene, a novel synthetic retinoid X receptor (RXR)-selective retinoid, has been reported to have antiproliferative and apoptotic stimulating effects in cutaneous T-cell lymphoma. In benign, hyperproliferative, and retinoid sensitive disorders, such as psoriasis, bexarotene has not been evaluated so far and no information on these parameters is available. OBJECTIVE: In the present study, immunohistochemical parameters for proliferation, differentiation, inflammation, and apoptosis were investigated in a group of bexarotene-treated psoriatic patients. METHODS: Twenty-nine patients with plaque-type psoriasis were treated for 12 weeks with oral bexarotene in four dose-defined treatment panels. Treatment was initiated in the following consecutive order: 1.0 mg/kg/day, 2.0 mg/kg/day, 0.5 mg/kg/day, and 3.0 mg/kg/day. Biopsies for immunohistochemical analysis were taken at the baseline and after 12 weeks of treatment. RESULTS: Significant reductions in Ki-67, keratin 16, transglutaminase, dermal CD4, epidermal CD8, and inflammation scores were seen after bexarotene treatment in combination with a significant increase in keratin 10. No induction of keratin 13 and 19 and no alterations in apoptosis associated p53 expression were observed. Apart from a weak significant dose-response effect for Ki-67, no other significant dose-response effects were seen. CONCLUSION: We have demonstrated efficacy of oral bexarotene in psoriasis in doses up to 3.0 mg/kg/day during 12 weeks of treatment for proliferation, differentiation, and inflammation parameters. Studies investigating higher doses of bexarotene in a larger number of patients are necessary to reveal potentially dose-related immunohistochemical effects of this new rexinoid and to elucidate the role of RXR-signaling in retinoid-associated keratin expression.

Administration, Oral↗
PubMed2006

Minimizing adverse side-effects of oral bexarotene in cutaneous T-cell lymphoma: an expert opinion.

Bexarotene is an oral retinoid therapy that is effective for the treatment of early and advanced-stage cutaneous T-cell lymphoma (CTCL) in patients who have failed on other therapies. However, bexarotene treatment is associated with unavoidable side-effects, in particular hypertriglyceridaemia and hypothyroidism, which are manageable with adequate concomitant medications and are reversible on cessation of treatment. A pragmatic strategy for minimizing bexarotene-associated hypertriglyceridaemia and hypothyroidism is suggested, based on data from the studies with bexarotene in CTCL and on day-to-day experience with this agent in the clinical setting. The strategy anticipates that these common adverse events are likely to occur and recommends the early use of preventive therapy to lower triglycerides and elevate thyroid hormone levels in the blood, followed by subsequent monitoring, dose adjustment during bexarotene treatment, and titration of the daily bexarotene dose from 150 to 300 mg m(-2), which is optimal for most patients. When further information becomes available on how bexarotene interacts with lipid metabolism and thyroid function, the management approach suggested here may need to be changed.

Anticarcinogenic Agents↗
PubMedDate not supplied

Effects of oral bexarotene (targretin) on the minimal erythema dose for broadspectrum UVB light.

Photo(chemo)therapy and oral retinoid therapy for psoriasis or cutaneous T-cell lymphoma are frequently combined to obtain an enhanced therapeutic effect with lower safety risks. Bexarotene, a new RXR-selective retinoid (rexinoid), has been developed for the treatment of cutaneous T-cell lymphoma and has recently been investigated in the treatment of psoriasis. In the present study the UV-modulating properties of bexarotene were evaluated by assessment of the minimal erythema dose (MED) for UVB light. In 11 patients participating in a phase II study of oral bexarotene 0.5 mg/kg/day (7 patients) or 3.0 mg/kg/day (4 patients) for plaque-type psoriasis, MED tests were performed on uninvolved psoriatic skin on the lower back of the subjects before and after 12-week treatment. Clinical scores of erythema and determination of the MED 24 h after irradiation did not show statistically significant changes between the exposed areas before and after bexarotene treatment or between the two doses tested. No photosensitizing reactions were observed. This study demonstrates that a single exposure to UVB irradiation is well tolerated in patients treated with bexarotene 0.5-3.0 mg/kg/day and suggests that it is not necessary to take precautions with respect to short-term effects of sun exposure during bexarotene treatment. Further study of bexarotene photo(chemo)therapy in cutaneous T-cell lymphoma and psoriasis is warranted.

Administration, Oral↗
PubMed2005

The retinoid X receptor agonist bexarotene (Targretin) synergistically enhances the growth inhibitory activity of cytotoxic drugs in non-small cell lung cancer cells.

This study was designed to evaluate, using preclinical models of non-small cell lung cancer (NSCLC), the growth inhibitory effects of the retinoid X receptor (RXR) agonist bexarotene (LGD1069, Targretin) in combination with cytotoxic agents currently used as standard first-line therapy in advanced disease. Although single-agent bexarotene had modest growth inhibitory effects in several cell lines, efficacy was observed only in the micromolar range (>1muM), which approximates the plasma C(max) measured in pharmacokinetic studies in patients. However, when combined with paclitaxel or vinorelbine, bexarotene produced a concentration-dependent enhancement of the growth inhibitory activities of paclitaxel and vinorelbine. Formal synergy analysis using the Calu3 cell line demonstrated that the combination of bexarotene with either cytotoxic agent produced synergistic activity (combination index, CI<1). The in vitro observations were confirmed in vivo in a NSCLC xenograft tumor model (Calu3), where both bexarotene/paclitaxel and bexarotene/vinorelbine combinations produced significantly greater antitumor effects than the single agents. These results demonstrate that bexarotene can cooperate with widely used cytotoxic agents to decrease the growth of NSCLC tumor cells both in vitro and in vivo, and suggest the potential benefit of adding a RXR-selective agonist in combination with chemotherapy for NSCLC treatment. Furthermore, the data support the clinical observation from phase I/IIa trials suggesting that bexarotene has beneficial effects on survival when used in combination with cytotoxic agents in advanced NSCLC.

Animals↗
PubMed2005

The selective retinoid X receptor agonist bexarotene (LGD1069, Targretin) prevents and overcomes multidrug resistance in advanced breast carcinoma.

Acquired drug resistance represents a major challenge in the therapeutic management of breast cancer patients. We reported previously that the retinoid X receptor-selective agonist bexarotene (LGD1069, Targretin) was efficacious in treating animal models of tamoxifen-resistant breast cancer. The goal of this study was to evaluate the effect of bexarotene on development of acquired drug resistance and its role in overcoming acquired drug resistance in advanced breast cancer. Paclitaxel, doxorubicin, and cisplatin were chosen as model compounds to determine the effect of bexarotene on the development of acquired drug resistance. Human breast cancer cells MDA-MB-231 were repeatedly treated in culture with a given therapeutic agent with or without bexarotene for 3 months. Thereafter, cells were isolated and characterized for their drug sensitivity. Compared with parental cells, cells treated with a single therapeutic agent became resistant to the therapeutic agent, whereas cells treated with the bexarotene combination remained chemosensitive. Cells with acquired drug resistance, when treated with the combination, showed increased sensitivity to the cytotoxic agent. Furthermore, cells treated with the combination regimen had reduced invasiveness and angiogenic potential than their resistant counterparts. These in vitro findings were further confirmed in an in vivo MDA-MB-231 xenograft model. Our results suggest a role for bexarotene in combination with chemotherapeutic agents in prevention and overcoming acquired drug resistance in advanced breast carcinoma.

ATP Binding Cassette Transporter, Subfamily B, Mem↗