The utility of bexarotene in mycosis fungoides and Sézary syndrome

Chlormethine gel in combination with other therapies for treatment of mycosis fungoides: a review with patient cases

Topical chlormethine gel has been approved as monotherapy for treatment of adult patients with mycosis fungoides (MF), the most common form of cutaneous T-cell lymphoma. In clinical practice, chlormethine gel is often combined with other skin-directed or systemic therapies to optimize response and target recalcitrant lesions. Positive outcomes with combination regimens using chlormethine gel and topical corticosteroids, phototherapy, retinoids, methotrexate, or interferon-α have been reported in literature. However, there are no treatment guidelines on the use of combination regimens with chlormethine gel. To provide real-world evidence and guidance on the use of chlormethine gel combination regimens, several cases of patients treated with chlormethine gel combined with phototherapy (n = 5), retinoids (n = 16), or mogamulizumab (n = 3) are presented. These different combination regimens showed promising results. Most patients had a complete or partial response following treatment and the combinations were well-tolerated over extended treatment periods. Patients receiving chlormethine gel with retinoids had long-term periods of remission, even after treatment discontinuation. Durations of response of up to 3 years were observed in these patients. This long-term disease control may be the result of disease-modifying effects of chlormethine. Previous studies have shown targeted reductions in malignant T-cell clones in patients treated with chlormethine gel as well as improved post-treatment responses. Further research is needed to determine the effectiveness and safety of combination treatment regimens with chlormethine gel and to assess the impact chlormethine gel has on disease control.

Early intervention of extracorporeal photopheresis for advancing/progressing cutaneous T-cell lymphoma

Patients with cutaneous T-cell lymphoma with progressive disease typically undergo a series of skin-directed and systemic therapy regimens during cycles of response and relapse. Extracorporeal photopheresis (ECP) is an effective and safe systemic treatment option, often reserved for later stages of disease and typically employed after failure of several other therapies. ECP has benefits in response rate, time to next treatment, and tolerability that may support its use earlier in the treatment cycle for advancing/progressing disease.

Harnessing the immune system in the treatment of cutaneous T cell lymphomas

Cutaneous T cell lymphomas are a rare subset of non-Hodgkin's lymphomas with predilection for the skin with immunosuppressive effects that drive morbidity and mortality. We are now appreciating that suppression of the immune system is an important step in the progression of disease. It should come as no surprise that therapies historically and currently being used to treat these cancers have immune modulating functions that impact disease outcomes. By understanding the immune effects of our therapies, we may better develop new agents that target the immune system and improve combinatorial treatment strategies to limit morbidity and mortality of these cancers. The immune modulating effect of therapeutic drugs in use and under development for cutaneous T cell lymphomas will be reviewed.

Cocrystal Prediction of Bexarotene by Graph Convolution Network and Bioavailability Improvement

Bexarotene (BEX) was approved by the FDA in 1999 for the treatment of cutaneous T-cell lymphoma (CTCL). The poor aqueous solubility causes the low bioavailability of the drug and thereby limits the clinical application. In this study, we developed a GCN-based deep learning model (CocrystalGCN) for in-silico screening of the cocrystals of BEX. The results show that our model obtained high performance relative to baseline models. The top 30 of 109 coformer candidates were scored by CocrystalGCN and then validated experimentally. Finally, cocrystals of BEX-pyrazine, BEX-2,5-dimethylpyrazine, BEX-methyl isonicotinate, and BEX-ethyl isonicotinate were successfully obtained. The crystal structures were determined by single-crystal X-ray diffraction. Powder X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis were utilized to characterize these multi-component forms. All cocrystals present superior solubility and dissolution over the parent drug. The pharmacokinetic studies show that the plasma exposures (AUC0-8h) of BEX-pyrazine and BEX-2,5-dimethylpyrazine are 1.7 and 1.8 times that of the commercially available BEX powder, respectively. This work sets a good example for integrating virtual prediction and experimental screening to discover the new cocrystals of water-insoluble drugs.

Bexarotene: A Rare Cause of Misleading Thyroid Function Tests

Bexarotene is a very rare cause of central hypothyroidism (CH) and its effects have been reported to be dose-dependent; however, the available data in the literature on dose-dependent effects are variable. The standard practice of monitoring thyroid function using thyroid-stimulating hormone (TSH) to adjust levothyroxine (LT4) dose does not apply to bexarotene since it causes CH. In CH, TSH is not reliable. Hence free tetraiodothyronine (fT₄) level is used to monitor and adjust the LT4 dose. We report a case of an 81-year-old Caucasian male with cutaneous T-cell lymphoma (CTCL) who was treated with bexarotene. His pre-treatment TSH was normal at 1.6 µIU/mL (reference range: 0.46-4.68 µIU/mL). Post-bexarotene, the total tetraiodothyronine (T₄) level was within the reference range, but a downward trend was noted. Eventually, total triiodothyronine (T₃) dropped to a low level of 0.61 ng/mL (reference range: 0.97-1.69 ng/mL), and LT4 was initiated. Bexarotene dose was increased, but LT4 was not increased by the primary physician who relied on TSH level, which was low, and hence the existing LT4 dose was maintained. The patient had persistent symptoms of hypothyroidism and, eventually, a diagnosis of CH was made. The symptoms of hypothyroidism improved after normalizing fT₄, with an increase in the LT4 dose. This case represents an example of missed CH due to bexarotene, ­which led to suboptimal LT4 replacement impacting the quality of life for the patient.

Association of APOA5 and APOC3 Genetic Polymorphisms With Severity of Hypertriglyceridemia in Patients With Cutaneous T-Cell Lymphoma Treated With Bexarotene

Importance

Hypertriglyceridemia is the most frequent and limiting adverse effect of bexarotene therapy in cutaneous T-cell lymphoma (CTCL). Despite standard prophylactic measures, there is a wide variability in the severity of this complication, which could be associated with both genetic and environmental factors.

Objectives

To analyze the association between genetic polymorphisms of apolipoprotein genes APOA5, APOC3, and APOE and the severity of hypertriglyceridemia during bexarotene therapy and to optimize patient selection for bexarotene therapy based on adverse effect profile.

Design, Setting, and Participants

This case series study was conducted in 12 university referral hospitals in Spain from September 17, 2014, to February 6, 2015. One hundred twenty-five patients with a confirmed diagnosis of CTCL who had received bexarotene therapy for at least 3 months were enrolled. Nine patients were excluded owing to missing analytic triglyceride level data, leaving a study group of 116 patients. Data on demographic and cardiovascular risk factor were collected, and a complete blood analysis, including lipid profile and genetic analysis from a saliva sample, was performed.

Main Outcomes and Measures

Primary outcomes were the maximal triglyceride levels reported in association with the minor alleles of the polymorphisms studied.

Results

Among 116 patients, the mean (SD) age was 61.2 (14.7) years, 69 (59.5%) were men, and 85 (73.2%) had mycosis fungoides, the most prevalent form of CTCL. During bexarotene therapy, 96 patients (82.7%) experienced hypertriglyceridemia, which was severe or extreme in 8 of these patients (8.3%). Patients who carried minor alleles of the polymorphisms did not show significant differences in baseline triglyceride concentrations. After bexarotene treatment, carriers of at least 1 of the 2 minor alleles of APOA5 c.-1131T>C and APOC3 c.*40C>G showed lower levels of triglycerides than noncarriers (mean [SD], 241.59 [169.91] vs 330.97 [169.03] mg/dL, respectively; P = .02).

Conclusions and Relevance

These results indicate that the screening of APOA5 and APOC3 genotypes may be useful to estimate changes in triglyceride concentrations during bexarotene treatment in patients with CTCL and also to identify the best candidates for bexarotene therapy based on the expected adverse effect profile.

Carboxylation of Aryl Triflates with CO2 Merging Palladium and Visible-Light-Photoredox Catalysts

We report herein a visible-light-promoted, highly practical carboxylation of readily accessible aryl triflates at ambient temperature and a balloon pressure of CO₂ by the combined use of palladium and photoredox Ir(III) catalysts. Strikingly, the stoichiometric metallic reductant is replaced by a nonmetallic amine reductant providing an environmentally benign carboxylation process. In addition, one-pot synthesis of a carboxylic acid directly from phenol and modification of estrone and concise synthesis of pharmaceutical drugs adapalene and bexarotene have been accomplished via late-stage carboxylation reaction. Furthermore, a parallel decarboxylation-carboxylation reaction has been demonstrated in an H-type closed vessel that is an interesting concept for the strategic sector. Spectroscopic and spectroelectrochemical studies indicated electron transfer from the Ir(III)/DIPEA combination to generate aryl carboxylate and Pd(0) for catalytic turnover.

Successful Treatment of Advanced Primary Cutaneous Peripheral T-Cell Lymphoma with Oral Bexarotene Monotherapy

Bexarotene is a third-generation retinoid X receptor-selective retinoid that is widely used for the early treatment of advanced-stage cutaneous T-cell lymphomas. In this report, we describe a case of successful treatment of advanced primary cutaneous peripheral T-cell lymphoma not otherwise specified (PTCL-NOS) with oral bexarotene monotherapy. After the administration of oral bexarotene at a dose of 300 mg/m²/day, all skin lesions and lymph nodes regressed, and complete remission was achieved for 1 year. Our case suggested that bexarotene monotherapy could be one of the possible therapies for the treatment of primary cutaneous PTCL-NOS.

Retinoic acid receptor alpha drives cell cycle progression and is associated with increased sensitivity to retinoids in T-cell lymphoma

Peripheral T-cell lymphomas (PTCLs) are aggressive non-Hodgkin lymphomas with generally poor outcomes following standard therapy. Few candidate therapeutic targets have been identified to date. Retinoic acid receptor alpha (RARA) is a transcription factor that modulates cell growth and differentiation in response to retinoids. While retinoids have been used to treat some cutaneous T-cell lymphomas (CTCLs), their mechanism of action and the role of RARA in CTCL and other mature T-cell lymphomas remain poorly understood. After identifying a PTCL with a RARAR394Q mutation, we sought to characterize the role of RARA in T-cell lymphoma cells. Overexpressing wild-type RARA or RARAR394Q significantly increased cell growth in RARAlow cell lines, while RARA knockdown induced G1 arrest and decreased expression of cyclin-dependent kinases CDK2/4/6 in RARAhigh cells. The retinoids, AM80 (tamibarotene) and all-trans retinoic acid, caused dose-dependent growth inhibition, G1 arrest, and CDK2/4/6 down-regulation. Genes down-regulated in transcriptome data were enriched for cell cycle and G1-S transition. Finally, RARA overexpression augmented chemosensitivity to retinoids. In conclusion, RARA drives cyclin-dependent kinase expression, G1-S transition, and cell growth in T-cell lymphoma. Synthetic retinoids inhibit these functions in a dose-dependent fashion and are most effective in cells with high RARA expression, indicating RARA may represent a therapeutic target in some PTCLs.

Successful Treatment of Primary Cutaneous Peripheral T-Cell Lymphoma Presenting Acquired Ichthyosis with Oral Bexarotene Monotherapy

Acquired ichthyosis (AI) is a reactive cutaneous manifestation that can be associated with malignant hematological disease, including cutaneous T-cell lymphoma (CTCL). Since it is difficult to distinguish AI from ichthyosiform mycosis fungoides, to select the treatment for CTCL with ichthyosis-like appearance and to evaluate its efficacy is sometimes challenging. In this report, we describe a case of primary cutaneous peripheral T-cell lymphoma not otherwise specified presenting AI successfully treated with oral bexarotene. In the present case, the administration of oral bexarotene was not only effective for lymphoma cells infiltrating ulcers and nodules, but it also eliminated AI.

Targeting Retinoid Receptors to Treat Schizophrenia: Rationale and Progress to Date

This review provides the rationale and reports on the progress to date regarding the targeting of retinoid receptors for the treatment of schizophrenia and schizoaffective disorder and the role of retinoic acid in functions of the normal brain, and in psychotic states. After a brief introduction, we describe the normal function of retinoic acid in the brain. We then examine the evidence regarding retinoid dysregulation in schizophrenia. Finally, findings from two add-on clinical trials with a retinoid (bexarotene) are discussed. The authors of this review suggest that targeting retinoid receptors may be a novel approach to treat schizophrenia and schizoaffective disorder. Further studies are warranted.