Phase I Dose Escalation Study of Topical Bexarotene in Women at High Risk for Breast Cancer.

PREVENTION RELEVANCE: Bexarotene is a rexinoid that has been shown to prevent mammary tumors in mouse models but oral dosing has toxicities. This phase I study evaluates topical bexarotene, as a potential chemoprevention agent, for safety and toxicity in high-risk women for breast cancer.

Safety and efficacy of bexarotene in patients with relapsing-remitting multiple sclerosis (CCMR One): a randomised, double-blind, placebo-controlled, parallel-group, phase 2a study.

BACKGROUND: Progressive disability in multiple sclerosis occurs because CNS axons degenerate as a late consequence of demyelination. In animals, retinoic acid receptor RXR-gamma agonists promote remyelination. We aimed to assess the safety and efficacy of a non-selective retinoid X receptor agonist in promoting remyelination in people with multiple sclerosis. METHODS: This randomised, double-blind, placebo-controlled, parallel-group, phase 2a trial (CCMR One) recruited patients with relapsing-remitting multiple sclerosis from two centres in the UK. Eligible participants were aged 18-50 years and had been receiving dimethyl fumarate for at least 6 months. Via a web-based system run by an independent statistician, participants were randomly assigned (1:1), by probability-weighted minimisation using four binary factors, to receive 300 mg/m2 of body surface area per day of oral bexarotene or oral placebo for 6 months. Participants, investigators, and outcome assessors were masked to treatment allocation. MRI scans were done at baseline and at 6 months. The primary safety outcome was the number of adverse events and withdrawals attributable to bexarotene. The primary efficacy outcome was the patient-level change in mean lesional magnetisation transfer ratio between baseline and month 6 for lesions that had a baseline magnetisation transfer ratio less than the within-patient median. We analysed the primary safety outcome in the safety population, which comprised participants who received at least one dose of their allocated treatment. We analysed the primary efficacy outcome in the intention-to-treat population, which comprised all patients who completed the study. This study is registered in the ISRCTN Registry, 14265371, and has been completed. FINDINGS: Between Jan 17, 2017, and May 17, 2019, 52 participants were randomly assigned to receive either bexarotene (n=26) or placebo (n=26). Participants who received bexarotene had a higher mean number of adverse events (6·12 [SD 3·09]; 159 events in total) than did participants who received placebo (1·63 [SD 1·50]; 39 events in total). All bexarotene-treated participants had at least one adverse event, which included central hypothyroidism (n=26 vs none on placebo), hypertriglyceridaemia (n=24 vs none on placebo), rash (n=13 vs one on placebo), and neutropenia (n=10 vs none on placebo). Five (19%) participants on bexarotene and two (8%) on placebo discontinued the study drug due to adverse events. One episode of cholecystitis in a placebo-treated participant was the only serious adverse event. The change in mean lesional magnetisation transfer ratio was not different between the bexarotene group (0·25 percentage units [pu; SD 0·98]) and the placebo group (0·09 pu [0·84]; adjusted bexarotene-placebo difference 0·16 pu, 95% CI -0·39 to 0·71; p=0·55). INTERPRETATION: We do not recommend the use of bexarotene to treat patients with multiple sclerosis because of its poor tolerability and negative primary efficacy outcome. However, statistically significant effects were seen in some exploratory MRI and electrophysiological analyses, suggesting that other retinoid X receptor agonists might have small biological effects that could be investigated in further studies. FUNDING: Multiple Sclerosis Society of the United Kingdom.

Combination of Sulindac and Bexarotene for Prevention of Intestinal Carcinogenesis in Familial Adenomatous Polyposis.

Familial adenomatous polyposis (FAP) is a hereditary colorectal cancer syndrome, which results in the development of hundreds of adenomatous polyps carpeting the gastrointestinal tract. NSAIDs have reduced polyp burden in patients with FAP and synthetic rexinoids have demonstrated the ability to modulate cytokine-mediated inflammation and WNT signaling. This study examined the use of the combination of an NSAID (sulindac) and a rexinoid (bexarotene) as a durable approach for reducing FAP colonic polyposis to prevent colorectal cancer development. Whole transcriptomic analysis of colorectal polyps and matched normal mucosa in a cohort of patients with FAP to identify potential targets for prevention in FAP was performed. Drug-dose synergism of sulindac and bexarotene in cell lines and patient-derived organoids was assessed, and the drug combination was tested in two different mouse models. This work explored mRNA as a potential predictive serum biomarker for this combination in FAP. Overall, transcriptomic analysis revealed significant activation of inflammatory and cell proliferation pathways. A synergistic effect of sulindac (300 µmol/L) and bexarotene (40 µmol/L) was observed in FAP colonic organoids with primary targeting of polyp tissue compared with normal mucosa. This combination translated into a significant reduction in polyp development in ApcMin/+ and ApcLoxP/+-Cdx2 mice. Finally, the reported data suggest miRNA-21 could serve as a predictive serum biomarker for polyposis burden in patients with FAP. These findings support the clinical development of the combination of sulindac and bexarotene as a treatment modality for patients with FAP. PREVENTION RELEVANCE: This study identified a novel chemopreventive regimen combining sulindac and bexarotene to reduce polyposis in patients with FAP using in silico tools, ex vivo, and in vivo models. This investigation provides the essential groundwork for moving this drug combination forward into a clinical trial.

Case series of cutaneous T-cell lymphomas treated with bexarotene-based therapy.

Bexarotene is useful for both early and advanced cutaneous T-cell lymphoma (CTCL), and is sometimes applied to ultraviolet-tolerant early CTCL patients as one of the first-line therapies in the real world. However, continuous administration of bexarotene is sometimes difficult because of its adverse events (AE). Development of an appropriate protocol for bexarotene that can induce a consistent response for CTCL without severe AE (SAE) is needed. We retrospectively investigated 29 Japanese cases of CTCL and evaluated the efficacy of treatment and incident ratios of all AE and SAE. Objective response rate (ORR) for the overall cohort was 65.5%. ORR of the 300 mg/m2 cohort (conventional dose) was 76.2%, while that of the 150-300 mg/body (low dose) with narrowband ultraviolet B light (NBUVB) cohort was 37.5%. Mean event-free survival was 10.0 months for all patients, 6.7 months for the bexarotene conventional-dose cohort and 19.1 months for the low-dose with NBUVB cohort. The incident ratio of total SAE for all patients was 20.7%. The incident ratio of total SAE was 23.8% for the conventional-dose cohort and 12.5% for the low-dose with NBUVB cohort. Our present study suggests that low-dose bexarotene plus NBUVB therapy is well-tolerated and could be one of the optimal therapies for advanced CTCL.

Efficacy and safety of bexarotene combined with photo(chemo)therapy for cutaneous T-cell lymphoma.

Cutaneous T-cell lymphoma (CTCL) is a chronic condition with low malignancy. International treatment guidelines for CTCL are widely followed in Europe and the USA. Combination therapy with therapeutic agents for CTCL and phototherapy is effective on the basis of European data. The efficacy and safety of combination therapy for Japanese CTCL patients are not established. We investigated the efficacy and safety of combination therapy with photo(chemo)therapy and bexarotene in Japanese CTCL patients. Twenty-five patients received daily oral bexarotene (300 mg/m2 body surface), followed by bath-psoralen plus ultraviolet (UV)-A (PUVA) or narrowband UV-B. Treatment results were evaluated using the modified Severity-Weighted Assessment Tool (mSWAT) and the Physician Global Assessment of Clinical Condition (PGA) up to week 24. Safety was also assessed. Twenty-four weeks after initiating treatment, the total response rate was 80.0% (mSWAT) and 84.0% (PGA). Response rates did not differ when stratified by disease stage. Number of days (mean ± standard deviation) for time to response, duration of response and time to progression determined by the mSWAT were 20.7 ± 9.62, 117.0 ± 43.0 and 163.6 ± 28.8, respectively. T-helper 2 chemokine levels in patients at stage IIA or more decreased significantly at weeks 12 and 24. All patients experienced adverse events and adverse drug reactions. Serious adverse drug reactions included sepsis, anemia and congestive cardiac insufficiency (n = 1 each). Other adverse drug reactions were of mild to moderate severity. Combination therapy with bexarotene and PUVA was safe and effective in Japanese CTCL patients.

Retinoid X receptor agonists attenuates cardiomyopathy in streptozotocin-induced type 1 diabetes through LKB1-dependent anti-fibrosis effects.

Diabetic cardiac fibrosis increases ventricular stiffness and facilitates the occurrence of diastolic dysfunction. Retinoid X receptor (RXR) plays an important role in cardiac development and has been implicated in cardiovascular diseases. In the present study, we investigated the effects of RXR agonist treatment on streptozotocin (STZ)-induced diabetic cardiomyopathy (DCM) and the underlying mechanism. Sprague-Dawley (SD) rats induced by STZ injection were treated with either RXR agonist bexarotene (Bex) or vehicle alone. Echocardiography was performed to determine cardiac structure and function. Cardiac fibroblasts (CFs) were treated with high glucose (HG) with or without the indicated concentration of Bex or the RXR ligand 9-cis-retinoic acid (9-cis-RA). The protein abundance levels were measured along with collagen, body weight (BW), blood biochemical indexes and transforming growth factor-ß (TGF-ß) levels. The effects of RXRα down-regulation by RXRα small interfering RNA (siRNA) were examined. The results showed that bexarotene treatment resulted in amelioration of left ventricular dysfunction by inhibiting cardiomyocyte apoptosis and myocardial fibrosis. Immunoblot with heart tissue homogenates from diabetic rats revealed that bexarotene activated liver kinase B1 (LKB1) signaling and inhibited p70 ribosomal protein S6 kinase (p70S6K). The increased collagen levels in the heart tissues of DCM rats were reduced by bexarotene treatment. Treatment of CFs with HG resulted in significantly reduced LKB1 activity and increased p70S6K activity. RXRα mediated the antagonism of 9-cis-RA on HG-induced LKB1/p70S6K activation changes in vitro. Our findings suggest that RXR agonist ameliorates STZ-induced DCM by inhibiting myocardial fibrosis via modulation of the LKB1/p70S6K signaling pathway. RXR agonists may serve as novel therapeutic agents for the treatment of DCM.

Bexarotent Attenuated Chronic Constriction Injury-Induced Spinal Neuroinflammation and Neuropathic Pain by Targeting Mitogen-Activated Protein Kinase Phosphatase-1.

It is widely accepted that neuroinflammation in the spinal cord contributes to the development of central sensitization in neuropathic pain. Mitogen-activated protein kinase (MAPK) activation plays a vital role in the development of neuroinflammation in the spinal cord. In this study, we investigated the effect of bexarotene (bex), a retinoid X receptor agonist, on MAPKs activation in chronic constriction injury (CCI)-induced neuropathic pain. The data showed that daily treatment with bex 50 mg/kg significantly alleviated CCI-induced nociceptive hypersensitivity in rats. Bex 50 mg/kg/day inhibited CCI-induced MAPKs (p38MAPK, ERK1/2, and JNK) activation and upregulation of proinflammatory factors (IL-1ß, tumor necrosis factor-α and IL-6). Bex also reversed CCI-induced microglia activation in the ipsilateral spinal cord. Furthermore, bex treatment significantly upregulated MKP-1 in the spinal cord. These effects were completely abrogated by MKP-1 inhibitor BCI. These results indicated that bex relieved CCI-induced neuroinflammation and neuropathic pain by targeting MKP-1. Therefore, bex might be a potential agent for the treatment of neuropathic pain. PERSPECTIVE: Bex could relieve neuropathic pain behaviors in animals by reversing MKP-1 downregulation and MAPKs activation in the spinal cord. Therapeutic applications of bex may be extended beyond cutaneous T-cell lymphoma.

Optimal control strategies for inhibition of protein aggregation.

Protein aggregation has been implicated in many medical disorders, including Alzheimer's and Parkinson's diseases. Potential therapeutic strategies for these diseases propose the use of drugs to inhibit specific molecular events during the aggregation process. However, viable treatment protocols require balancing the efficacy of the drug with its toxicity, while accounting for the underlying events of aggregation and inhibition at the molecular level. To address this key problem, we combine here protein aggregation kinetics and control theory to determine optimal protocols that prevent protein aggregation via specific reaction pathways. We find that the optimal inhibition of primary and fibril-dependent secondary nucleation require fundamentally different drug administration protocols. We test the efficacy of our approach on experimental data for the aggregation of the amyloid-ß(1-42) peptide of Alzheimer's disease in the model organism Caenorhabditis elegans Our results pose and answer the question of the link between the molecular basis of protein aggregation and optimal strategies for inhibiting it, opening up avenues for the design of rational therapies to control pathological protein aggregation.

Long-term efficacy and safety of bexarotene for Japanese patients with cutaneous T-cell lymphoma: The results of a phase 2 study (B-1201).

The present study (B-1201 clinical trial) was conducted as a multicenter, open-label, single-arm phase II study to evaluate the long-term safety, tolerability and efficacy of bexarotene. This study enrolled 10 Japanese adults aged more than 20 years with cutaneous T-cell lymphoma (CTCL) who completed the 24-week study period of the B-1101 trial. The objective response rate (ORR) was 53.8% (95% confidence interval, 25.1-80.8). In the early stage (IB), the ORR was 60% (3/5 cases). In the advanced stage (IIB and IIIA), the ORR was 57.1% (4/7 cases). The median time to response was 58 days (range, 27-168). The median treatment duration was 380 days (range, 33-1674). The median duration of response (DOR) could not be reached during the study period. The longest DOR reached 1618 days at the end of the B-1201 trial. Nine patients (56.3%) in the full analysis set (FAS) population experienced dose reduction of bexarotene. Common drug-related adverse events in the FAS population included hypothyroidism (93.8%), hypertriglyceridemia (81.3%), hypercholesterolemia (81.3%), leukopenia (68.8%) and neutropenia (56.3%). Dose-limiting toxicity (DLT) was present in five (38.5%) of the 13 patients in the 300 mg/m2 cohort. Of the five patients, four developed grade 3 neutropenia and one developed grade 4 hypertriglyceridemia. All DLT cases recovered after the discontinuation of bexarotene. None of the five patients discontinued this trial because of DLT. The B-1201 trial shows the long-term safety of oral bexarotene for Japanese patients with CTCL, despite frequent dose reduction.

Optimized Bexarotene Aerosol Formulation Inhibits Major Subtypes of Lung Cancer in Mice.

Bexarotene has shown inhibition of lung and mammary gland tumorigenesis in preclinical models and in clinical trials. The main side effects of orally administered bexarotene are hypertriglyceridemia and hypercholesterolemia. We previously demonstrated that aerosolized bexarotene administered by nasal inhalation has potent chemopreventive activity in a lung adenoma preclinical model without causing hypertriglyceridemia. To facilitate its future clinical translation, we modified the formula of the aerosolized bexarotene with a clinically relevant solvent system. This optimized aerosolized bexarotene formulation was tested against lung squamous cell carcinoma mouse model and lung adenocarcinoma mouse model and showed significant chemopreventive effect. This new formula did not cause visible signs of toxicity and did not increase plasma triglycerides or cholesterol. This aerosolized bexarotene was evenly distributed to the mouse lung parenchyma, and it modulated the microenvironment in vivo by increasing the tumor-infiltrating T cell population. RNA sequencing of the lung cancer cell lines demonstrated that multiple pathways are altered by bexarotene. For the first time, these studies demonstrate a new, clinically relevant aerosolized bexarotene formulation that exhibits preventive efficacy against the major subtypes of lung cancer. This approach could be a major advancement in lung cancer prevention for high risk populations, including former and present smokers.

Quantitative Prediction of Oral Bioavailability of a Lipophilic Antineoplastic Drug Bexarotene Administered in Lipidic Formulation Using a Combined In Vitro Lipolysis/Microsomal Metabolism Approach.

For performance assessment of the lipid-based drug delivery systems (LBDDSs), in vitro lipolysis is commonly applied because traditional dissolution tests do not reflect the complicated in vivo micellar formation and solubilization processes. Much of previous research on in vitro lipolysis has mostly focused on rank-ordering formulations for their predicted performances. In this study, we have incorporated in vitro lipolysis with microsomal stability to quantitatively predict the oral bioavailability of a lipophilic antineoplastic drug bexarotene (BEX) administered in LBDDS. Two types of LBDDS were applied: lipid solution and lipid suspension. The predicted oral bioavailability values of BEX from linking in vitro lipolysis with microsomal stability for lipid solution and lipid suspension were 34.2 ± 1.6% and 36.2 ± 2.6%, respectively, whereas the in vivo oral bioavailability of BEX was tested as 31.5 ± 13.4% and 31.4 ± 5.2%, respectively. The predicted oral bioavailability corresponded well with the oral bioavailability for both formulations, demonstrating that the combination of in vitro lipolysis and microsomal stability can quantitatively predict oral bioavailability of BEX. In vivo intestinal lymphatic uptake was also assessed for the formulations and resulted in <1% of the dose, which confirmed that liver microsomal stability was necessary for correct prediction of the bioavailability.

Treatment of Rosai-Dorfman disease with oral bexarotene: a case series.

Background: Rosai-Dorfman disease (RDD) is a rare histiocytic proliferative disorder of unknown etiology. The skin is the most frequent extranodal site of RDD involvement and may be the only organ involved. While RDD is an indolent self-limited disease, treatment is needed in patients with extensive, persistent or progressive disease, or if cosmetic disfigurement or physical impairment significantly affects the patient. There is no specific treatment for RDD, and multiple therapeutic approaches have been described with variable success rates. Ojective: To demonstrate the clinical efficacy of oral bexarotene for RDD. Materials and methods: Descriptive retrospective case series of three patients with RDD receiving oral bexarotene. Results: Two patients had excellent response and regression of their skin lesions was achieved with long-term therapy. In the other patient, pruritus was promptly controlled while the lesions did not seem to regress and treatment was discontinued after five months. Conclusions: Our case series is the first report in the literature of the use of oral bexarotene as an effective and safe treatment for RDD.

OAB-14, a bexarotene derivative, improves Alzheimer's disease-related pathologies and cognitive impairments by increasing ß-amyloid clearance in APP/PS1 mice.

The pathogenesis of Alzheimer's disease (AD) is complex, though the clinical failures of anti-AD candidates targeting Aß production (such as ß- and γ-secretase inhibitors) make people suspect the Aß hypothesis, in which the neurotoxicity of Aß is undoubtedly involved. According to studies, >95% of AD patients with sporadic AD are primarily associated with abnormal Aß clearance. Therefore, drugs that increase Aß clearance are becoming new prospects for the treatment of AD. Here, the novel small molecule OAB-14, designed using bexarotene as the lead compound, significantly alleviated cognitive impairments in amyloid precursor protein (APP)/presenilin 1 (PS1) transgenic mice after administration for 15 days or 3 months. OAB-14 rapidly cleared 71% of Aß by promoting microglia phagocytosis and increasing IDE and NEP expression. This compound also attenuated the downstream pathological events of Aß accumulation, such as synaptic degeneration, neuronal loss, tau hyperphosphorylation and neuroinflammation in APP/PS1 mice. Moreover, OAB-14 had no significant effect on body weight or liver toxicity after acute and chronic treatment. OAB-14 was well tolerated and its maximum-tolerated dose in mice was >4.0 g/kg. Based on these findings, OAB-14 represents a promising new candidate for AD treatment.

Lipophilic activated ester prodrug approach for drug delivery to the intestinal lymphatic system.

The intestinal lymphatic system plays an important role in the pathophysiology of multiple diseases including lymphomas, cancer metastasis, autoimmune diseases, and human immunodeficiency virus (HIV) infection. It is thus an important compartment for delivery of drugs in order to treat diseases associated with the lymphatic system. Lipophilic prodrug approaches have been used in the past to take advantage of the intestinal lymphatic transport processes to deliver drugs to the intestinal lymphatics. Most of the approaches previously adopted were based on very bulky prodrug moieties such as those mimicking triglycerides (TG). We now report a study in which a lipophilic prodrug approach was used to efficiently deliver bexarotene (BEX) and retinoic acid (RA) to the intestinal lymphatic system using activated ester prodrugs. A range of carboxylic ester prodrugs of BEX were designed and synthesised and all of the esters showed improved association with chylomicrons, which indicated an improved potential for delivery to the intestinal lymphatic system. The conversion rate of the prodrugs to BEX was the main determinant in delivery of BEX to the intestinal lymphatics, and activated ester prodrugs were prepared to enhance the conversion rate. As a result, an 4-(hydroxymethyl)-1,3-dioxol-2-one ester prodrug of BEX was able to increase the exposure of the mesenteric lymph nodes (MLNs) to BEX 17-fold compared to when BEX itself was administered. The activated ester prodrug approach was also applied to another drug, RA, where the exposure of the MLNs was increased 2.4-fold through the application of a similar cyclic activated prodrug. Synergism between BEX and RA was also demonstrated in vitro by cell growth inhibition assays using lymphoma cell lines. In conclusion, the activated ester prodrug approach results in efficient delivery of drugs to the intestinal lymphatic system, which could benefit patients affected by a large number of pathological conditions.

Emerging roles of bexarotene in the prevention, treatment and anti-drug resistance of cancers.

INTRODUCTION: Retinoic acid X receptors play key roles in tumor cell proliferation, differentiation, apoptosis and angiogenesis via transcriptional regulation. Bexarotene is a specific RXRs agonist which has been granted by FDA approval for the clinical treatment of cutaneous T cell lymphoma (CTCL). Its cancer prevention and treatment potentials in various tumors have been under investigation over the past decade. Areas covered: This review summarizes the efficacy and underlying mechanisms of bexarotene for the treatment of multiple cancers based on the launched clinical trials as well as the basic studies. Expert commentary: In general, bexarotene is an active and reasonable chemoprevention and treatment for various cancers and its combination regimen with other cytotoxic agents or targeted drugs may significantly enhance efficacy and at the same time reduce toxicity due to their nonoverlapping side effects. However, only a subpopulation of bexarotene treated patients benefited from bexarotene administration in most cases. The level of RXRs may serve as a preliminary indicator for the bexarotene response in cancers such as non-small cell lung cancer, acute myeloid leukemia, breast cancer, thyroid cancer and melanoma. Further identification and verification of bexarotene response biomarkers may finally lead to the personalized clinical application of bexarotene on cancers beyond CTCL.