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Background: Prevention and treatment of metastatic breast cancer (BC) is an unmet clinical need. The retinoic acid derivative fenretinide (FeR) was previously evaluated in Phase I-III clinical trials but, despite its excellent tolerability and antitumor activity in preclinical models, showed limited therapeutic efficacy due to poor bioavailability. We recently generated a new micellar formulation of FeR, Bionanofenretinide (Bio-nFeR) showing enhanced bioavailability, low toxicity, and strong antitumor efficacy on human lung cancer, colorectal cancer, and melanoma xenografts. In the present study, we tested the effect of Bio-nFeR on a preclinical model of metastatic BC., Methods: We used BC cell lines for in vitro analyses of cell viability, cell cycle and migratory capacity. For in vivo studies, we used HER2/neu transgenic mice (neuT) as a model of spontaneously metastatic BC. Mice were treated orally with Bio-nFeR and at sacrifice primary and metastatic breast tumors were analyzed by histology and immunohistochemistry. Molecular pathways activated in primary tumors were analyzed by immunoblotting. Stem cell content was assessed by flow cytometry, immunoblotting and functional assays such as colony formation ex vivo and second transplantation assay in immunocompromised mice., Results: Bio-nFeR inhibited the proliferation and migration of neuT BC cells in vitro and showed significant efficacy against BC onset in neuT mice. Importantly, Bio-nFeR showed the highest effectiveness against metastatic progression, counteracting both metastasis initiation and expansion. The main mechanism of Bio-nFeR action consists of promoting tumor dormancy through a combined induction of antiproliferative signals and inhibition of the mTOR pathway., Conclusion: The high effectiveness of Bio-nFeR in the neuT model of mammary carcinogenesis, coupled with its low toxicity, indicates this formulation as a potential candidate for the treatment of metastatic BC and for the adjuvant therapy of BC patients at high risk of developing metastasis., (© 2024. The Author(s).)

The retinoid fenretinide (FENR) is a promising compound for preventing breast cancer recurrence but faces challenges due to poor solubility and low bioavailability. This study explores the development of dissolving microneedles (MNs) containing FENR-loaded ethosomes for minimally invasive breast cancer chemoprevention, aiming to enhance local drug distribution. Ethosomes were formulated using ethanol, propylene glycol, soya lecithin, water, and polysorbate 80 micelles. MNs were created from poly(vinyl alcohol) and poly(vinylpyrrolidone) hydrogels by adding polymer powder directly into ethosomes suspensions, reducing manufacturing time and cost. Two methods were used to load ethosomes into high-density moulds: 1) only in the needle area, and 2) in both the needle area and baseplate. Dynamic light scattering confirmed nanostructures in the hydrogels and MNs. Micelle-based ethosomes dissolved MNs in 15 min, compared to 30 min for other MNs. Skin deposition studies showed greater drug deposition (up to 10 μg/patch) and enhanced skin permeation of FENR (up to 40 μg) with Method 2. In-vivo studies in rats demonstrated that oral administration resulted in plasma FENR levels below 10 ng/g in the first three hours, whereas MN administration delayed delivery, reaching a maximum plasma concentration of 52 ng/g at 48 h. Skin deposition of FENR from MNs decreased from 3 μg/g on day 1 to <0.3 μg/g by the last day. This study indicates that MNs are a potential minimally invasive dosage form for delivering FENR, offering a new approach for breast cancer chemoprevention., Competing Interests: Declaration of competing interest None., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Fenretinide, a retinoid with a low-toxicity profile that accumulates in the breast, has been shown to prevent second breast cancer in young women. Fenretinide exhibits apoptotic and antiinvasive properties and it improves insulin sensitivity in overweight premenopausal women with insulin resistance. This study aimed to further characterize its role in cancer prevention by measuring circulating biomarkers related to insulin sensitivity and breast cancer risk.Sixty-two women, ages 20 to 46 years, healthy or who had already undergone breast cancer surgery, with a known BRCA1/2 mutation or a likelihood of mutation ≥20% according to the BRCAPRO model, were randomly assigned to receive fenretinide (200 mg/day) or placebo for 5 years (trial registration: EudraCT No. 2009-010260-41). Fasting blood samples were drawn at baseline, 12 and 36 months, and the following biomarkers were analyzed: retinol, leptin, adiponectin, retinol-binding protein 4 (RBP-4), total cholesterol, high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol, triglycerides, glucose, insulin, insulin-like growth factor (IGF-1), IGF-binding protein 3, sex hormone binding globulin (SHBG), testosterone, and vascular endothelial growth factor (VEGF).After 12 months of treatment, we observed a favorable effect of fenretinide on glucose (decrease; P = 0.005), insulin (decrease; P = 0.03), homeostatic model assessment index (decrease; P = 0.004), HDL cholesterol (increase; P = 0.002), even though these effects were less prominent after 36 months. Retinol and retinol-binding protein 4 markedly decreased (P < 0.0001) throughout the study. None of the other measured biomarkers changed., Prevention Relevance: Fenretinide exhibits beneficial effects on the metabolic profile, supporting its clinical use in breast cancer prevention especially in premenopausal women with a positive family history and pathogenic variants in BRCA1/2 genes. This finding requires further investigations in larger trials to confirm its role in breast cancer prevention., (©2024 American Association for Cancer Research.)

The need of pharmacological strategies to preclude breast cancer development motivated us to develop a non-aqueous microemulsion (ME) capable of forming a depot after administration in the mammary tissue and uptake of interstitial fluids for prolonged release of the retinoid fenretinide. The selected ME was composed of phosphatidylcholine/tricaprylin/propylene glycol (45:5:50, w/w/w) and presented a droplet diameter of 175.3 ± 8.9 nm. Upon water uptake, the ME transformed successively into a lamellar phase, gel, and a lamellar phase-containing emulsion in vitro as the water content increased and released 30% of fenretinide in vitro after 9 days. Consistent with the slow release, the ME formed a depot in cell cultures and increased fenretinide IC 50 values by 68.3- and 13.2-fold in MCF-7 and T-47D cells compared to a solution, respectively. At non-cytotoxic concentrations, the ME reduced T-47D cell migration by 75.9% and spheroid growth, resulting in ∼30% smaller structures. The depot formed in vivo prolonged a fluorochrome release for 30 days without producing any sings of local irritation. In a preclinical model of chemically induced carcinogenesis, ME administration every 3 weeks for 3 months significantly reduced (4.7-fold) the incidence of breast tumors and increased type II collagen expression, which might contribute to limit spreading. These promising results support the potential ME applicability as a preventive therapy of breast cancer.

Background: Fenretinide is a synthetic retinoid that can induce cytotoxicity by several mechanisms. Achieving effective systemic exposure with oral formulations has been challenging. An intravenous lipid emulsion fenretinide formulation was developed to overcome this barrier. We conducted a study to establish the maximum tolerated dose (MTD), preliminary efficacy, and pharmacokinetics of intravenous lipid emulsion fenretinide in patients with advanced solid tumors., Methods: Twenty-three patients with advanced solid tumors refractory to standard treatments received fenretinide as a continuous infusion for five consecutive days in 21-day cycles. Five different dose cohorts were evaluated between doses of 905 mg/m 2 and 1414 mg/m 2 per day using a 3 + 3 dose escalation design. A priming dose of 600 mg/m 2 on day 1 was introduced in an attempt to address the asymptomatic serum triglyceride elevations related to the lipid emulsion., Results: The treatment-related adverse events occurring in ≥ 20% of patients were anemia, hypertriglyceridemia, fatigue, aspartate aminotransferase (AST)/alanine aminotransferase (ALT) increase, thrombocytopenia, bilirubin increase, and dry skin. Five evaluable patients had stable disease as best response, and no patients had objective responses. Plasma steady-state concentrations of the active metabolite were significantly higher than with previous capsule formulations., Conclusion: Fenretinide emulsion intravenous infusion had a manageable safety profile and achieved higher plasma steady-state concentrations of the active metabolite compared to previous capsule formulations. Single-agent activity was minimal but combinatorial approaches are under evaluation.

T-cell lymphoid malignancies (TCLMs) are in need of novel and more effective therapies. The histone deacetylase (HDAC) inhibitors and the synthetic cytotoxic retinoid fenretinide have achieved durable clinical responses in T-cell lymphomas as single agents, and patients who failed prior HDAC inhibitor treatment have responded to fenretinide. We have previously shown fenretinide synergized with the class I HDAC inhibitor romidepsin in preclinical models of TCLMs. There exist some key differences between HDAC inhibitors. Therefore, we determined if the pan-HDAC inhibitor vorinostat synergizes with fenretinide. We demonstrated cytotoxic synergy between vorinostat and fenretinide in nine TCLM cell lines at clinically achievable concentrations that lacked cytotoxicity for non-malignant cells (fibroblasts and blood mononuclear cells). In vivo, vorinostat + fenretinide + ketoconazole (enhances fenretinide exposures by inhibiting fenretinide metabolism) showed greater activity in subcutaneous TCLM xenograft models than other groups. Fenretinide + vorinostat increased reactive oxygen species (ROS, measured by 2',7'-dichlorodihydrofluorescein diacetate dye), resulting in increased apoptosis (via transferase dUTP nick end labeling assay) and histone acetylation (by immunoblotting). The synergistic cytotoxicity, apoptosis, and histone acetylation of fenretinide + vorinostat was abrogated by the antioxidant vitamin C. Like romidepsin, vorinostat combined with fenretinide achieved synergistic cytotoxic activity and increased histone acetylation in preclinical models of TCLMs, but not in non-malignant cells. As vorinostat is an oral agent and not a P-glycoprotein substrate it may have advantages in such combination therapy. These data support conducting a clinical trial of vorinostat combined with fenretinide in relapsed and refractory TCLMs., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

Purpose: In a previous study, we demonstrated that the combination of fenretinide with lenalidomide, administered by a novel nanomicellar formulation (FLM), provided a strong antitumor effect in a neuroblastoma TrkB-expressing tumor. In this study, we tested the nanomicellar combination in an MYCN amplified neuroblastoma xenograft to assess its efficacy in different tumor genotypes and evaluate the interactions of the nanomicelles with the tumor cells., Experimental Design: FLM was administered to mice bearing human NLF xenografts to evaluate its efficacy in comparison with the nanomicelles containing fenretinide alone (FM). Confocal laser-scanning fluorescence microscopy images of the NLF cells treated with FLM and FM allowed us to estimate the nanomicelle ability to transport the encapsulated drugs inside the tumor cells. Flow cytometric analysis of the cells from treated tumors was performed to assess the effect of treatment on GD2 expression and NK cell infiltration., Results: FLM and FM decreased the growth of NLF xenografts at comparable extents during the treatment period. Afterwards, FLM induced a progressive tumor regression without regrowth, while FM treatment was followed by regrowth within 15-20 days after the end of treatment. Both FLM and FM were able to penetrate the tumor cells transporting the encapsulated drugs. FLM transported higher amount of fenretinide inside the cells. Also, FLM treatment strongly increased GD2 expression in treated tumors and slightly decreased the NK infiltration compared to FM., Conclusion: FLM treatment induced a superior antitumor response than FM in NLF xenografts, presumably due to the combined effects of fenretinide cytotoxicity and lenalidomide antiangiogenic activity. The ability of FLM to penetrate tumor cells, transporting the encapsulated drugs, substantially improved the therapeutic efficiency of this system. Moreover, the enhancement of GD2 expression in FLM treated tumors offers the possibility to further increase the antitumor effect by the use of anti-GD2 CAR-T cells and anti-GD2 antibodies in combination with FLM in multimodal therapies., Competing Interests: The authors report no conflicts of interest in this work., (© 2020 Orienti et al.)

Fenretinide (4-HPR), as a semi-synthetic retinoid, has apoptosis-promoting effects as a single agent and chemotherapy synergist in vitro . When a human ovarian cancer cells line (A2780s) was treated with both PTX and 4-HPR, there was a synergistic anti-cancer effect demonstrated with a average combination index of 0.44. In this research, a new TPGS-Soluplus ® mixed micelles were developed which encapsulation efficiencies of paclitaxel (PTX) and fenretinide (4-HPR) were as high as 98%, and the average diameter of the micelles was 66.26 nm. Cytotoxicity of the mixed micelles co-delivered with PTX and 4-HPR reduced significantly 7.3 and 25.1 times compared with free drug respectively in A2780s cells. More importantly, in vivo pharmacokinetic study, the loaded drugs in mixed micelles exhibited higher AUC and t 1/2 values than free drugs. Furthermore, in vivo antitumor efficacy experiments demonstrated that PF-TS exhibited superior in vivo antitumor activity on the inhibition rate of tumor growth than other treatment groups (77.8% corresponding tumor growth inhibition in PF-TS treated group vs 19.9, 12.5, and 26.0% of tumor growth inhibition rate in Taxol ® , 4-HPR, and Taxol ® +4-HPR, respectively). Therefore, the mixed micelles of co-deliver PTX and 4-HPR successfully constructed may hopefully be applied to the cancer combination treatment with less toxic effect and more antitumor activity.

The purpose of this study was to develop solid dispersions of fenretinide(4HPR), incorporate them into poly(lactic-co-glycolic)(PLGA) millicylindrical implants, and evaluate the resulting implants in vitro and in vivo for future applications in oral cancer chemoprevention. Due to the extreme hydrophobicity of 4HPR, 4HPR-polyvinylpyrrolidone (PVP) amorphous solid dispersions(ASDs) were prepared for solubility enhancement. The optimal PVP-4HPR ratio of 9/1(w/w) provided a 50-fold solubility enhancement in aqueous media, which was sustained over 1 week. PVP-4HPR ASD particles were loaded into PLGA millicylinders and drug release was evaluated in vitro in PBST and in vivo by recovery from subcutaneous injection in rats. While initial formulations of PLGA PVP-4HPR millicylinders only released 10% 4HPR in vitro after 28 days, addition of the plasticizer triethyl-o-acetyl-citrate(TEAC) into PVP-4HPR ASDs resulted in a 5.6-fold total increase in drug release. Remarkably, the TEAC-PVP-4HPR PLGA implants demonstrated slow, continuous, and nearly complete release over 1 month in vivo compared to a 25% release for our previously reported formulation incorporating solubilizers and pore-forming agents. Hence, a combination of PLGA plasticizer and ASD formation provides an avenue for long-term controlled release in vivo for the exceptionally difficult drug to formulate, 4HPR, and a suitable formulation for future evaluation in rodent models of oral cancer., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier B.V.)

Cystic fibrosis (CF) is the most common genetic disease in Caucasians. CF is manifested by abnormal accumulation of mucus in the lungs, which serves as fertile ground for the growth of microorganisms leading to recurrent infections and ultimately, lung failure. Mucus in CF patients consists of DNA from dead neutrophils as well as mucins produced by goblet cells. MUC5AC mucin leads to pathological plugging of the airways whereas MUC5B has a protective role against bacterial infection. Therefore, decreasing the level of MUC5AC while maintaining MUC5B intact would in principle be a desirable mucoregulatory treatment outcome. Fenretinide prevented the lipopolysaccharide-induced increase of MUC5AC gene expression, without affecting the level of MUC5B, in a lung goblet cell line. Additionally, fenretinide treatment reversed the pro-inflammatory imbalance of fatty acids by increasing docosahexaenoic acid and decreasing the levels of arachidonic acid in a lung epithelial cell line and primary leukocytes derived from CF patients. Furthermore, for the first time we also demonstrate the effect of fenretinide on multiple unsaturated fatty acids, as well as differential effects on the levels of long- compared to very-long-chain saturated fatty acids which are important substrates of complex phospholipids. Finally, we demonstrate that pre-treating mice with fenretinide in a chronic model of P. aeruginosa lung infection efficiently decreases the accumulation of mucus. These findings suggest that fenretinide may offer a new approach to therapeutic modulation of pathological mucus production in CF., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Purpose: Currently >50% of high-risk neuroblastoma (NB) patients, despite intensive therapy and initial partial or complete response, develop recurrent NB due to the persistence of minimal residual disease (MRD) that is resistant to conventional antitumor drugs. Indeed, their low therapeutic index prevents drug-dose escalation and protracted administration schedules, as would be required for MRD treatment. Thus, more effective and less toxic therapies are urgently needed for the management of MRD. To address this aim, we evaluated a new combination of fenretinide and lenalidomide, both endowed with antitumor activity and low-toxicity profiles. New nanomicelles were prepared as carriers for this combination to maximize bioavailability and accumulation at the tumor site because of the enhanced permeability and retention (EPR) effect., Experimental Design: New nanomicelles containing the fenretinide-lenalidomide combination (FLnMs) were prepared by a one-step method, providing high drug encapsulation and micelle dimensions suitable for tumor accumulation. Their administration to mice bearing human NB xenografts allowed us to evaluate their efficacy in comparison with the nanomicelles containing fenretinide alone (FnMs)., Results: Treatment by FLnMs significantly decreased the tumor growth of NB xenografts. FLnMs were more active than FnMs despite comparable fenretinide concentrations in tumors, and lenalidomide alone did not show cytotoxic activity in vitro against NB cells. The tumor mass at the end of treatment with FLnMs was predominantly necrotic, with a decreased Ki-67 proliferation index., Conclusion: FLnMs provided superior antitumor efficacy in NB xenografts compared to FnMs. The enhanced efficacy of the combination was likely due to the antiangiogenic effect of lenalidomide added to the cytotoxic effect of fenretinide. This new nanomicellar combination is characterized by a low-toxicity profile and offers a novel therapeutic option for the treatment of high-risk tumors where the persistence of MRD requires repeated administrations of therapeutic agents over long periods of time to avoid recurrent disease., Competing Interests: The authors report no conflicts of interest in this work., (© 2019 Orienti et al.)

Background: An increasing number of anticancer agents has been proposed in recent years with the attempt to overcome treatment-resistant cancer cells and particularly cancer stem cells (CSC), the major culprits for tumour resistance and recurrence. However, a huge obstacle to treatment success is the ineffective delivery of drugs within the tumour environment due to limited solubility, short circulation time or inconsistent stability of compounds that, together with concomitant dose-limiting systemic toxicity, contribute to hamper the achievement of therapeutic drug concentrations. The synthetic retinoid Fenretinide (4-hydroxy (phenyl)retinamide; 4-HPR) formerly emerged as a promising anticancer agent based on pre-clinical and clinical studies. However, a major limitation of fenretinide is traditionally represented by its poor aqueous solubility/bioavailability due to its hydrophobic nature, that undermined the clinical success of previous clinical trials., Methods: Here, we developed a novel nano-micellar fenretinide formulation called bionanofenretinide (Bio-nFeR), based on drug encapsulation in an ion-pair stabilized lipid matrix, with the aim to raise fenretinide bioavailability and antitumour efficacy., Results: Bio-nFeR displayed marked antitumour activity against lung, colon and melanoma CSC both in vitro and in tumour xenografts, in absence of mice toxicity. Bio-nFeR is suitable for oral administration, reaching therapeutic concentrations within tumours and an unprecedented therapeutic activity in vivo as single agent., Conclusion: Altogether, our results indicate Bio-nFeR as a novel anticancer agent with low toxicity and high activity against tumourigenic cells, potentially useful for the treatment of solid tumours of multiple origin.

Objectives: This study investigated the antitumor effect of a new nanomicellar complex obtained by combining the antitumor agent fenretinide with a quaternary amphiphilic amine RC16+ also endowed with antitumor activity., Methods: The complex (Fen-RC16+) strongly improved the aqueous solubility of fenretinide (from 1,71 ± 0.08 µg/ml, pure fenretinide to 1500 ± 164 µg /ml, Fen-RC16+ complex) and provided a cytotoxic effect on SH-SY5Y neuroblastoma cell lines resulting from the intrinsic activity of both the complex components. Moreover, the mean size of the nanomicellar complex (ranging from 20 ± 1.97 nm to 40 ± 3.05 nm) was suitable for accumulation to the tumor site by the enhanced permeability and retention effect and the positive charge provided by the quaternary RC16+ induced adsorption of the complex on the tumor cell surface improving the intracellular concentration of fenretinide., Results: All these characteristics made the Fen-RC16+ complex a multitasking system for antitumor therapy., Conclusion: Indeed its in vivo activity, evaluated on SH-SY5Y xenografts, was strong, and the tumor growth did not resume after the treatment withdrawal., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Menopausal symptoms are the main reason for withdrawal in tamoxifen prevention trials. Here, we present Menopause Quality of Life (MenQoL) assessment within a randomized 2 × 2 phase II clinical trial of low-dose tamoxifen and the synthetic retinoid fenretinide. A total of 235 premenopausal women at higher risk for breast cancer were randomized to either tamoxifen 5 mg daily, fenretinide 200 mg daily, their combination, or placebo. Climacteric symptoms were investigated using the MenQoL questionnaire which was self-administered at each visit for 2 years of treatment and for 1 year of follow-up. CYP2D6 was genotyped in subjects taking tamoxifen to study the association with menopausal symptoms. The MenQoL effect size analysis showed no statistically significant difference among the four treatment arms for all four domains (vasomotor, physical, psychosocial, and sexual). Vasomotor symptoms only slightly increased under tamoxifen, with a score at year two of 1.45, 1.21, 0.58, and 1.17 in the combined, tamoxifen, fenretinide, and placebo arms, respectively. Compared with the slow metabolizers, a higher percentage of subjects with CYP2D6 extensive metabolizer genotype complained of a ≥3 score in the vasomotor, psychosocial, and sexual domain in the tamoxifen arms ( P value = 0.01, 0.007, and 0.007, respectively). QoL in premenopausal or perimenopausal women was not significantly worsened by low-dose tamoxifen or fenretinide. Our findings suggest that a low dose of tamoxifen may increase its acceptability for breast cancer prevention., (©2018 American Association for Cancer Research.)

Effective treatment of malignant glioma still remains a formidable challenge due to lack of the effective BBB-permeable drugs and efficient brain delivery methods, and the pharmacotherapy options are very limited. Therefore, to develop an effective therapeutic strategy is a pressing need. In this work, a noncytotoxic drug combination (i.e., simvastatin and fenretinide) was revealed to be potent for treating glioma, which was co-encapsulated into a TPGS-TAT-embedded lactoferrin nanoparticle system for achieving brain-targeted biomimetic delivery via the LRP-1 receptor. It was shown that the lactoferrin nanoparticle repolarized the tumor-associated macrophages from the M2 phenotype to M1 via regulating the STAT6 pathway, as well as induced the ROS-mediated mitochondrial apoptosis by inhibiting the Ras/Raf/p-Erk pathway in the glioma cells. The antiglioma efficacy was further demonstrated in both the subcutaneous and orthotopic glioma models. The repolarization of tumor-associated macrophages not only prompted the ROS generation but also induced the innate immunity (e.g., antitumor cytokine release). This delivery and therapeutic strategy provides a novel modality for the glioma treatment., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Local, long-acting release fenretinide (4HPR) millicylindrical implants were prepared and evaluated for their release kinetics in vivo and their ability to suppress oral cancer tumor explant growth. Poly(lactic-co-glycolic acid)(PLGA) implants were prepared as a function of drug loading and the presence of various excipients (pore-formers, solubilizers, crystallization inhibitors) to enhance release of the insoluble 4HPR. Release kinetics and bioerosion of PLGA were monitored both in vitro in a PBS/Tween 80 buffer and in vivo by recovery of the drug remaining at the injection site. 4HPR was released from PLGA implants much slower in vivo than in the drug solubilizing media in vitro, with a 3-week lag phase and continuous release of >2 months, but showed some release enhancement by addition of solubilizers. Water-soluble PVA/sucrose implants for release of 4HPR served to determine if drug dissolution provided suitable controlled release without the PLGA, and this formulation showed continuous drug release over 6 weeks in vivo. Placement of PLGA-4HPR implants adjacent to oral cancer tumor murine xenografts showed inhibition of tumor growth relative to sham implants, indicating the potential for the local 4HPR delivery approach to be useful for oral cancer chemoprevention., (Copyright © 2017. Published by Elsevier B.V.)

Purpose: A phase I study was conducted to determine the MTD, dose-limiting toxicities (DLT), and pharmacokinetics of fenretinide delivered as an intravenous emulsion in relapsed/refractory hematologic malignancies. Experimental Design: Fenretinide (80-1,810 mg/m 2 /day) was administered by continuous infusion on days 1 to 5, in 21-day cycles, using an accelerated titration design. Results: Twenty-nine patients, treated with a median of three prior regimens (range, 1-7), were enrolled and received the test drug. Ninety-seven courses were completed. An MTD was reached at 1,280 mg/m 2 /day for 5 days. Course 1 DLTs included 6 patients with hypertriglyceridemia, 4 of whom were asymptomatic; 2 patients experienced DLT thrombocytopenia (asymptomatic). Of 11 patients with response-evaluable peripheral T-cell lymphomas, two had complete responses [CR, progression-free survival (PFS) 68+ months; unconfirmed CR, PFS 14+ months], two had unconfirmed partial responses (unconfirmed PR, PFS 5 months; unconfirmed PR, PFS 6 months), and five had stable disease (2-12 cycles). One patient with mature B-cell lymphoma had an unconfirmed PR sustained for two cycles. Steady-state plasma levels were approximately 10 mcg/mL (mid-20s μmol/L) at 640 mg/m 2 /day, approximately 14 mcg/mL (mid-30s μmol/L) at 905 mg/m 2 /day, and approximately 22 mcg/mL (mid-50s μmol/L) at 1,280 mg/m 2 /day. Conclusions: Intravenous fenretinide obtained significantly higher plasma levels than a previous capsule formulation, had acceptable toxicities, and evidenced antitumor activity in peripheral T-cell lymphomas. A recommended phase II dosing is 600 mg/m 2 on day 1, followed by 1,200 mg/m 2 on days 2 to 5, every 21 days. A registration-enabling phase II study in relapsed/refractory PTCL (ClinicalTrials.gov identifier: NCT02495415) is ongoing. Clin Cancer Res; 23(16); 4550-5. ©2017 AACR ., (©2017 American Association for Cancer Research.)

We previously reported that concurrent ketoconazole, an oral anti-fungal agent and P450 enzyme inhibitor, increased plasma levels of the cytotoxic retinoid, fenretinide (4-HPR) in mice. We have now determined the effects of concurrent ketoconazole on 4-HPR cytotoxic dose-response in four neuroblastoma (NB) cell lines in vitro and on 4-HPR activity against two cell line-derived, subcutaneous NB xenografts (CDX) and three patient-derived NB xenografts (PDX). Cytotoxicity in vitro was assessed by DIMSCAN assay. Xenografted animals were treated with 4-HPR/LXS (240 mg/kg/day) + ketoconazole (38 mg/kg/day) in divided oral doses in cycles of five continuous days a week. In one model, intratumoral levels of 4-HPR and metabolites were assessed by HPLC assay, and in two models intratumoral apoptosis was assessed by TUNEL assay, on Day 5 of the first cycle. Antitumor activity was assessed by Kaplan-Meier event-free survival (EFS). The in vitro cytotoxicity of 4-HPR was not affected by ketoconazole (p ≥ 0.06). Ketoconazole increased intratumoral levels of 4-HPR (p = 0.02), of the active 4-oxo-4-HPR metabolite (p = 0.04), and intratumoral apoptosis (p ≤ 0.0006), compared to 4-HPR/LXS-alone. Concurrent ketoconazole increased EFS in both CDX models compared to 4-HPR/LXS-alone (p ≤ 0.008). 4-HPR + ketoconazole also increased EFS in PDX models compared to controls (p ≤ 0.03). Thus, concurrent ketoconazole decreased 4-HPR metabolism with resultant increases of plasma and intratumoral drug levels and antitumor effects in neuroblastoma murine xenografts. These results support the clinical testing of concurrent ketoconazole and oral fenretinide in neuroblastoma., (© 2017 UICC.)

Fenretinide (4-HPR) is a synthetic retinoid that has cytotoxic activity against cancer cells. Despite substantial in vitro cytotoxicity, response rates in early clinical trials with 4-HPR have been less than anticipated, likely due to the low bioavailability of the initial oral capsule formulation. Several clinical studies have shown that the oral capsule formulation at maximum tolerated dose (MTD) achieved <10 µmol/L concentrations in patients. To improve bioavailability of 4-HPR, new oral powder (LYM-X-SORB®, LXS) and intravenous lipid emulsion (ILE) formulations are being tested in early-phase clinical trials. ILE 4-HPR administered as five-day continuous infusion achieved over 50 µmol/L at MTD with minimal systemic toxicities; multiple complete and partial responses were observed in peripheral T cell lymphomas. The LXS oral powder 4-HPR formulation increased plasma levels approximately two-fold at MTD in children without dose-limiting toxicities and demonstrated multiple complete responses in recurrent neuroblastoma. The clinical activity observed with new 4-HPR formulations is attributed to increased bioavailability. Phase I and II clinical trials of both LXS 4-HPR and ILE 4-HPR are in progress as a single agent or in combination with other drugs. Impact statement One of the critical components in drug development is understanding pharmacology (especially pharmacokinetics) of the drugs being developed. Often the pharmacokinetic properties, such as poor solubility leading to poor bioavailability, of the drug can limit further development of the drug. The development of numerous drugs has often halted at clinical testing stages, and several of them were due to the pharmacological properties of the agents, resulting in increased drug development cost. The current review provides an example of how improved clinical activity can be achieved by changing the formulations of a drug with poor bioavailability. Thus, it emphasizes the importance of understanding pharmacologic characteristics of the drug in drug development.

T-cell lymphoid malignancies (TCLM) are in need of novel and more effective therapies. The histone deacetylase (HDAC) inhibitor romidepsin and the synthetic cytotoxic retinoid fenretinide both have achieved durable clinical responses in T-cell lymphomas as single agents. We investigated the potential for using these two agents in combination in TCLMs. We demonstrated cytotoxic synergy between romidepsin and fenretinide in 15 TCLM cell lines at clinically achievable concentrations that lacked cytotoxicity for nonmalignant cells (fibroblasts and blood mononuclear cells). In vivo , romidepsin + fenretinide + ketoconazole (enhances fenretinide exposures by inhibiting fenretinide metabolism) showed greater activity in subcutaneous and disseminated TCLM xenograft models than single-agent romidepsin or fenretinide + ketoconazole. Fenretinide + romidepsin caused a reactive oxygen species (ROS)-dependent increase in proapoptotic proteins (Bim, tBid, Bax, and Bak), apoptosis, and inhibition of HDAC enzymatic activity, which achieved a synergistic increase in histone acetylation. The synergistic cytotoxicity, apoptosis, and histone acetylation of fenretinide + romidepsin were abrogated by antioxidants (vitamins C or E). Romidepsin + fenretinide activated p38 and JNK via ROS, and knockdown of p38 and JNK1 significantly decreased the synergistic cytotoxicity. Romidepsin + fenretinide also showed synergistic cytotoxicity for B-lymphoid malignancy cell lines, but did not increase ROS, acetylation of histones, activation of p38 + JNK, or cytotoxicity in nonmalignant cells. Romidepsin + fenretinide achieved synergistic activity in preclinical models of TCLMs, but not in nonmalignant cells, via a novel molecular mechanism. These data support conducting clinical trials of romidepsin + fenretinide in relapsed and refractory TCLMs. Mol Cancer Ther; 16(4); 649-61. ©2017 AACR ., (©2017 American Association for Cancer Research.)

Clinical studies have shown that fenretinide (4-HPR) is an attractive chemopreventive agent for cancer treatment. However, to date, few studies have demonstrated the mechanism of the preventive effect of 4-HPR. In our current study, we revealed that 4-HPR could significantly suppress IL-4/IL-13 induced M2-like polarization of macrophages, which was demonstrated by the reduced expression of M2 surface markers, the down-regulation of M2 marker genes, and the inhibition of M2-like macrophages promoted angiogenesis. Mechanistically, our study suggested that the inhibition of the phosphorylation of STAT6, rather than the generation of oxidative stress, is involved in the 4-HPR-driven inhibition of M2 polarization. More intriguingly, by utilizing adenomatous polyposis coli (APC min/+ ) transgenic mice, we demonstrated that the tumorigenesis was dramatically decreased by 4-HPR treatment accompanied with fewer M2-like macrophages in the tumor tissues, thereby profoundly blocking tumor angiogenesis. These findings, for the first time, reveal the involvement of M2 polarization inhibition in 4-HPR-mediated chemoprevention, which provides a new point of insight and indicates the potential mechanism underlying the chemopreventive effect of 4-HPR., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

Fenretinide, a synthetic retinoid, induces apoptotic cell death in B-cell non-Hodgkin lymphoma (B-NHL) and acts synergistically with rituximab in preclinical models. We report results from a phase I-II study of fenretinide with rituximab for B-NHLs. Eligible diagnoses included indolent B-NHL or mantle cell lymphoma. The phase I design de-escalated from fenretinide at 900 mg/m 2 PO BID for days 1-5 of a 7-day cycle. The phase II portion added 375 mg/m 2 IV rituximab weekly on weeks 5-9 then every 3 months. Fenretinide was continued until progression or intolerance. Thirty-two patients were treated: 7 in phase I, and 25 in phase II of the trial. No dose-limiting toxicities were observed. The phase II component utilized fenretinide 900 mg/m 2 twice daily with rituximab. The most common treatment-related adverse events of grade 3 or higher were rash (n = 3) and neutropenia (n = 3). Responses were seen in 6 (24%) patients on the phase II study, with a median duration of response of 47 months (95% confidence interval, 2-56). The combination of fenretinide and rituximab was well tolerated, yielded a modest overall response rate, but with prolonged remission durations. Further study should focus on identifying the responsive subset of B-NHL., Competing Interests: The authors have declared no conflicts of interest., (© 2017 John Wiley & Sons Ltd.)

Over one third of patients who have undergone oral squamous cell carcinoma (OSCC) surgical resections develop life-threatening and often untreatable recurrences. A variety of drugs, intended for management of recurrent or disseminated cancers, were designed to exploit cancer cells' reliance upon overexpressed receptors and gratuitous signaling. Despite their conceptual promise, clinical trials showed these agents lacked efficacy and were often toxic. These findings are consistent with evasion of pathway-targeted treatments via extensive signaling redundancies and compensatory mechanisms common to cancers. Optimal secondary OSCC chemoprevention requires long-term efficacy with multifaceted, nontoxic agents. Accordingly, this study evaluated the abilities of three complementary chemopreventives, that is, the vitamin A derivative fenretinide (4-HPR, induces apoptosis and differentiation, inhibits signaling proteins, and invasion), the estrogen metabolite 2-methoxyestradiol (2-ME, apoptosis-inducing, antiangiogenic), and the humanized mAb to the IL6R receptor tocilizumab (TOC, reduces IL6 signaling) to suppress OSCC gratuitous signaling and tumorigenesis. Modeling studies demonstrated 4-HPR's high-affinity binding at STAT3's dimerization site and c-Abl and c-Src ATP-binding kinase sites. Although individual agents suppressed cancer-promoting pathways including STAT3 phosphorylation, STAT3-DNA binding, and production of the trans-signaling enabling sIL6R, maximal chemopreventive effects were observed with agent combinations. OSCC tumor xenograft studies showed that locally delivered TOC, TOC+4-HPR, and TOC+4-HPR+2-ME treatments all prevented significant tumor growth. Notably, the TOC+4-HPR+2-ME treatment resulted in the smallest overall increase in tumor volume. The selected agents use diverse mechanisms to disrupt tumorigenesis at multiple venues, that is, intracellular, tumor cell-ECM, and tumor microenvironment; beneficial qualities for secondary chemopreventives. Cancer Prev Res; 10(1); 76-88. ©2016 AACR., (©2016 American Association for Cancer Research.)

We and others have shown that stresses, including photodynamic therapy (PDT), can disrupt the de novo sphingolipid biosynthesis pathway, leading to changes in the levels of sphingolipids, and subsequently, modulation of cell death. The de novo sphingolipid biosynthesis pathway includes a ceramide synthase-dependent reaction, giving rise to dihydroceramide, which is then converted in a desaturase-dependent reaction to ceramide. In this study we tested the hypothesis that combining Foscan-mediated PDT with desaturase inhibitor fenretinide (HPR) enhances cancer cell killing. We discovered that by subjecting SCC19 cells, a human head and neck squamous cell carcinoma cell line, to PDT+HPR resulted in enhanced accumulation of C16-dihydroceramide, not ceramide. Concomitantly, mitochondrial depolarization was enhanced by the combined treatment. Enhanced activation of caspase-3 after PDT+HPR was inhibited by FB. Enhanced clonogenic cell death after the combination was sensitive to FB, as well as Bcl2- and caspase inhibitors. Treatment of mouse SCCVII squamous cell carcinoma tumors with PDT+HPR resulted in improved long-term tumor cures. Overall, our data showed that combining PDT with HPR enhanced apoptotic cancer cell killing and antitumor efficacy of PDT. The data suggest the involvement of the de novo sphingolipid biosynthesis pathway in enhanced apoptotic cell killing after PDT+HPR, and identify the combination as a novel more effective anticancer treatment than either treatment alone., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Fenretinide is an anticancer drug with low water solubility and poor bioavailability. The goal of this study was to develop biodegradable polymeric nanoparticles of fenretinide with the intent of increasing its apparent aqueous solubility and intestinal permeability. Three biodegradable polymers were investigated for this purpose: two different poly lactide-co-glycolide (PLGA) polymers, one acid terminated and one ester terminated, and one poly lactide-co-glycolide/polyethylene glycol (PLGA/PEG) diblock copolymer. Nanoparticles were obtained by using an emulsification solvent evaporation technique. The formulations were characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and particle size analysis. Dissolution studies and Caco-2 cell permeation studies were also carried out for all formulations. Ultra high performance liquid chromatography coupled with mass spectrometry (UPLC/MS) and ultraviolet detection was used for the quantitative determination of fenretinide. Drug loading and the type of polymer affected the nanoparticles' physical properties, drug release rate, and cell permeability. While the acid terminated PLGA nanoparticles performed the best in drug release, the ester terminated PLGA nanoparticles performed the best in the Caco-2 cell permeability assays. The PLGA/PEG copolymer nanoparticles performed better than the formulations with ester terminated PLGA in terms of drug release but had the poorest performance in terms of cell permeation. All three categories of formulations performed better than the drug alone in both drug release and cell permeation studies., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Retinoids are an important component of neuroblastoma therapy at the stage of minimal residual disease, yet 40-50% of patients treated with 13-cis-retinoic acid (13-cis-RA) still relapse, indicating the need for more effective retinoid therapy. Vorinostat, or Suberoylanilide hydroxamic acid (SAHA), is a potent inhibitor of histone deacetylase (HDAC) classes I & II and has antitumor activity in vitro and in vivo. Fenretinide (4-HPR) is a synthetic retinoid which acts on cancer cells through both nuclear retinoid receptor and non-receptor mechanisms. In this study, we found that the combination of 4-HPR + SAHA exhibited potent cytotoxic effects on neuroblastoma cells, much more effective than 13-cis-RA + SAHA. The 4-HPR + SAHA combination induced caspase-dependent apoptosis through activation of caspase 3, reduced colony formation and cell migration in vitro, and tumorigenicity in vivo. The 4-HPR and SAHA combination significantly increased mRNA expression of thymosin-beta-4 (Tβ4) and decreased mRNA expression of retinoic acid receptor α (RARα). Importantly, the up-regulation of Tβ4 and down-regulation of RARα were both necessary for the 4-HPR + SAHA cytotoxic effect on neuroblastoma cells. Moreover, Tβ4 knockdown in neuroblastoma cells increased cell migration and blocked the effect of 4-HPR + SAHA on cell migration and focal adhesion formation. In primary human neuroblastoma tumor tissues, low expression of Tβ4 was associated with metastatic disease and predicted poor patient prognosis. Our findings demonstrate that Tβ4 is a novel therapeutic target in neuroblastoma, and that 4-HPR + SAHA is a potential therapy for the disease., (Copyright © 2015 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.)

Fenretinide is an effective anti-cancer drug with high in vitro cytotoxicity and low in vivo systemic toxicity. In clinical trials, fenretinide has shown poor therapeutic efficacy following oral administration - attributed to its low bioavailability and solubility. The long term goal of this project is to develop a formulation for the oral delivery of fenretinide. The purpose of this part of the study was to prepare and characterize hydrophilic nanoparticle formulations of fenretinide. Three different ratios of polyvinyl pyrrolidone (PVP) to fenretinide were used, namely, 3:1, 4:1, and 5:1. Both drug and polymer were dissolved in a mixture of methanol and dichloromethane (2:23 v/v). Rotary evaporation was used to remove the solvents, and, following reconstitution with water, a high pressure homogenizer was used to form nanoparticles. The particle size and polydispersity index were measured before and after lyophilization. The formulations were studied by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray powder diffraction (XRPD). The effectiveness of the formulations was assessed by release studies and Caco-2 cell permeability assays. As the PVP content increased, the recovered particle size following lyophilization became more consistent with the pre-lyophilization particle size, especially for those formulations with less lactose. The DSC scans of the formulations did not show any fenretinide melting endotherms, indicating that the drug was either present in an amorphous form in the formulation or that a solid solution of the drug in PVP had formed. For the release studies, the highest drug release among the formulations was 249.2±35.5ng/mL for the formulation with 4:1 polymer-to-drug. When the permeability of the formulations was evaluated in a Caco-2 cell model, the mean normalized flux for each treatment group was significantly higher (p<0.05) from the fenretinide control. The formulation containing 4:1 polymer-to-drug ratio and 6:5 lactose-to-formulation ratio emerged as the optimal choice for further evaluation as a potential oral delivery formulation for fenretinide., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The present study deals with the preparation of albumin nanocapsules containing fenretinide and their evaluation in experimental models of human non-small cell lung cancer. These nanocapsules showed enhanced antitumor activity with respect to free fenretinide due to the solubilization effect of albumin on the hydrophobic drug, known to improve bioavailability. The high expression of caveolin-1 on the A549 cell surface further enhanced the antitumor activity of the nanoencapsulated fenretinide. Caveolin-1 favored albumin uptake and improved the efficacy of the fenretinide-loaded albumin nanocapsules, especially in 3-D cultures where the densely packed 3-D structures impaired drug diffusibility and severely reduced the activity of the free drug. The efficacy of the fenretinide albumin nanocapsules was further confirmed in tumor xenograft models of A549 by the significant delay in tumor progression observed with respect to control after intravenous administration of the novel formulation., From the Clinical Editor: This study describes the preparation of fenretinide containing albumin nanocapsules and their evaluation in experimental models of non-small cell lung cancer, showing enhanced antitumor activity compared to free fenretinide., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Recent evidence indicated that endocan may be a potential cell marker and a new target for cancers including acute leukemia since the serum endocan level in patients with acute leukemia was associated with the status of the disease, i.e., endocan was higly expressed in untreated acute leukemia, but decreased after chemotherapy and increased again during bone marrow regeneration. The present study showed that there was high level expression of endocan in cytoplasm of bone marrow blasts of patients with acute myeloid leukemia or acute lymphoblastic leukemia. The expression level of endocan was significantly decreased when the patients underwent remission after chemotherapy and re-bounces back when the acute leukemia relapsed. No obvious change in expression of endocan was observed before and after chemotherapy if the patients showed no remission after chemotherapy. (N-(4-Hydroxyphenyl)  retinamide), a potent anti-angiogenic agent, could not only down-regulate the expression of vascular epithelial growth factor, but also decrease endocan transcription and expression in NB4 cells, a human acute promyelocytic leukemia cell line. These observations suggest that endocan could act as a predictor for the severity and the prognosis of acute leukemia. The findings could be used as the basis for future targeted therapy directed against bone marrow angiogenesis in acute leukemia treatment.

Successful management of metastatic breast cancer still needs better chemotherapeutic approaches. The combination of fenretinide (4-HPR), a synthetic retinoid inducing apoptosis by ROS generation, and TRAIL, a cell death ligand inducing caspase-dependent apoptosis, might result in more powerful cytotoxic activity. We therefore investigated the cytotoxic activity and resulting cell death mode of this combination in MDA-MB-231 cell line as a representative of metastatic state. Cytotoxicity was assessed by the ATP viability assay while the mode of cell death was determined both morphologically using fluorescence microscopy and biochemically using Western blotting and ELISA. The combination resulted in an additive cytotoxic effect at the doses used. Fragmented and/or pyknotic nuclei, which is a feature of apoptosis, were observed after treatment with fenretinide or TRAIL. However, the combinatorial treatment further increased apoptotic figures. Confirming apoptosis, active caspase-3 and cleaved PARP were increased by fenretinide or TRAIL in both western blotting and ELISA. Again, apoptosis was further increased by the combination. The combination warrants further studies due to its superior cytotoxic activity in the metastatic setting of breast cancer., (Copyright © 2014 Elsevier Masson SAS. All rights reserved.)

Background: Patients with relapsed/refractory stage 4 high-risk neuroblastoma were enrolled on a phase I study (NANT2004-03) of intravenous fenretinide emulsion. Pharmacokinetic samples were collected during and after the infusion, and the levels were measured using an HPLC system. A likely case of a fatal drug interaction between fenretinide, ceftriaxone, and acetaminophen is described, including the pharmacokinetics of fenretinide, laboratory data, and post-mortem autopsy in a pediatric neuroblastoma patient treated on this study., Case Presentation: On Day 4 of a scheduled 5-day-infusion of intravenous fenretinide, the patient developed a fever, acetaminophen was started, ceftriaxone initiated for possible bacteremia, and fenretinide level doubled from 56 to 110 μM. Over the next three days, although blood cultures remained negative, the patient's condition deteriorated rapidly. Acute liver failure was diagnosed on Day 7, and the patient expired on Day 20 of fulminant hepatic failure with associated renal, cardiac, and hemorrhagic/coagulation toxicities. Autopsy showed extensive hemorrhagic necrosis of the liver, marked bile duct proliferation, and abundant hemosiderin, consistent with cholestasis and drug toxicity., Conclusions: After extensive review of patient data, the clinical course, and the literature, we conclude that observed hepatic toxicity was likely due to a drug interaction between fenretinide and concomitant ceftriaxone and acetaminophen. None of the other 16 patients treated on this study experienced significant hepatic toxicity. Although the prevalence of cholestasis with ceftriaxone usage is relatively high, the potential drug interaction with these concomitant medications has not been previously reported. Concomitant use of fenretinide, ceftriaxone, and acetaminophen should be avoided.

Tamoxifen and fenretinide have been extensively studied and exhibit breast cancer-preventing activity. We aimed to assess their effect on sex hormones, sex hormone binding globulin (SHBG) and retinol, and their association with mammographic density (MD) and breast cancer events. In a double-blind, placebo-controlled trial, premenopausal women at risk for breast cancer were randomized to tamoxifen 5 mg/day, fenretinide, both agents, or placebo for 2 years. We measured MD and circulating concentrations of follicle-stimulating hormone, luteinizing hormone (LH), estradiol, progesterone, testosterone, androstenedione, dehydro-epiandrosteronesulfate, prolactin, SHBG, and retinol at baseline and on yearly intervals. The associations with breast cancer events were evaluated through competing risk and Cox regression survival models. Low-dose tamoxifen markedly and enduringly increased SHBG, whereas the increases in testosterone, estradiol, and prolactin and reduction in LH weakened after 1 year. Fenretinide increased testosterone and androstenedione and decreased retinol. MD correlated directly with SHBG and inversely with retinol. After a median follow-up of 12 years, the 10-year cumulative incidence of breast cancer events was 37 % in women with SHBG ≤ 59.3 nmol/L, 22 % in women with SHBG between 59.3 and 101 nmol/L, and 19 % in women with SHBG > 101 nmol/L (P = 0.018). The difference among SHBG tertiles remained statistically significant at multivariable analysis: HR = 2.26 (95 % CI 1.04, 4.89) for the lowest versus the highest tertile. We conclude that low-dose tamoxifen or fenretinide exhibits favorable hormonal profiles as single agents, further supporting their administration for prevention of breast cancer in premenopause. Notably, SHBG levels were inversely associated with breast neoplastic events.

The combination of fenretinide and selenite on ovarian cancer cells was investigated to assess its effects on proliferation and ability to induce apoptosis. Our results showed that fenretinide and selenite in combination significantly suppress the proliferation of ovarian cancer cells and induced apoptosis (including reactive oxygen species generation, and the loss of mitochondrial membrane potential) compared with either drug used alone. The caspase3/9-dependent pathway was triggered significantly in combination treatment, and moreover, the AMPK pathway also mediated the apoptosis induction in fenretinide and selenite combination. Fenretinide and selenite combination treatment was demonstrated to suppress tumor growth in vivo, this drug combination has been thus found to have an enhanced anti-tumor effect on ovarian cancers cells.

Background: A phase I study was conducted to determine the maximum-tolerated dose, dose-limiting toxicities (DLTs), and pharmacokinetics of fenretinide (4-HPR) delivered in an oral powderized lipid complex (LXS) in patients with relapsed/refractory neuroblastoma., Procedure: 4-HPR/LXS powder (352-2,210 mg/m(2) /day) was administered on Days 0-6, in 21-day courses, by standard 3 + 3 design., Results: Thirty-two patients (median age = 8 years, range 3-27 years) enrolled with 30 evaluable for dose escalation. Prior therapies included stem cell transplantation/support (n = 26), 13-cis-retinoic acid (n = 22), (125/131) I-MIBG (n = 13), and anti-GD2 antibody (n = 6). 170+ courses were delivered. Course 1 DLTs were a Grade 3 (n = 1) alkaline phosphatase at 352 mg/m(2) /day. Other major toxicities were Grade 4 (n = 1) alkaline phosphatases on Courses 5 and 6 at 774 mg/m(2) /day, and Grade 3 (n = 1) ALT/AST elevation on Course 2 at 1,700 mg/m(2) /day. Of 29 response-evaluable patients, six had stable disease (SD) (4-26 courses); four with marrow- or bone disease-only had complete responses (CR) (10-46 courses). 4-HPR plasma levels were several folds higher (P < 0.05) than previously reported using capsular fenretinide. The Day 6 mean peak 4-HPR plasma level at 1,700 mg/m(2) /day was 21 µM. An MTD was not reached., Conclusions: 4-HPR/LXS oral powder obtained higher plasma levels, with minimal toxicity and evidence of anti-tumor activity, than a previous capsule formulation. A recommended phase II schedule of 4-HPR/LXS powder is 1,500 mg/m(2) /day, TID, on Days 0-6, of a 21-day course., (Copyright © 2013 Wiley Periodicals, Inc.)

Neuroblastoma is an embryonal tumor originating from the simpatico-adrenal lineage of the neural crest. It approximately accounts for about 15% of all pediatric oncology deaths. Despite advances in multimodal therapy, metastatic neuroblastoma tumors at diagnosis remain a clinical challenge. Retinoids are a class of compounds known to induce both terminal differentiation and apoptosis/necrosis of neuroblastoma cells. Among them, fenretinide (HPR) has been considered one of the most promising anti-tumor agent but it is partially efficacious due to both poor aqueous solubility and rapid metabolism. Here, we have developed a novel HPR formulation, by which the drug was encapsulated into sterically stabilized nanoliposomes (NL[HPR]) according to the Reverse Phase Evaporation method. This procedure led to a higher structural integrity of liposomes in organic fluids for a longer period of time, in comparison with our previous liposomal formulation developed by the film method. Moreover, NL[HPR] were further coupled with NGR peptides for targeting the tumor endothelial cell marker, aminopeptidase N (NGR-NL[HPR]). Orthotopically xenografted neuroblastoma-bearing mice treated with NGR-NL[HPR] lived statistically longer than mice untreated or treated with free HPR (NGR-NL[HPR] vs both control and HPR: P<0.0001). Also, NL[HPR] resulted in a statistically improved survival (NL[HPR] vs both control and HPR: P<0.001) but to a less extent if compared with that obtained with NGR-NL[HPR] (NGR-NL[HPR] vs NL[HPR]: P<0.01). Staining of tumor sections with antibodies specific for neuroblastoma and for either pericytes or endothelial cells evidenced that HPR reduced neuroblastoma growth through both anti-tumor and anti-angiogenic effects, mainly when delivered by NGR-NL[HPR]. Indeed, in this group of mice a marked reduction of tumor progression, of intra-tumoral vessel counts and VEGF expression, together with a marked down-modulation of matrix metalloproteinases MMP2 and MMP9, was observed. In conclusion, the use of this novel targeted delivery system for the apoptotic and antiangiogenic drug, fenretinide, could be considered as an adjuvant tool in the future treatment of neuroblastoma patients., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Background: Rhabdoid tumors are highly aggressive malignancies affecting infants and very young children. In many instances these tumors are resistant to conventional type chemotherapy necessitating alternative approaches., Methods: Proliferation assays (MTT), apoptosis (propidium iodide/annexin V) and cell cycle analysis (DAPI), RNA expression microarrays and western blots were used to identify synergism of the HDAC (histone deacetylase) inhibitor SAHA with fenretinide, tamoxifen and doxorubicin in rhabdoidtumor cell lines., Results: HDAC1 and HDAC2 are overexpressed in primary rhabdoid tumors and rhabdoid tumor cell lines. Targeting HDACs in rhabdoid tumors induces cell cycle arrest and apoptosis. On the other hand HDAC inhibition induces deregulated gene programs (MYCC-, RB program and the stem cell program) in rhabdoid tumors. These programs are in general associated with cell cycle progression. Targeting these activated pro-proliferative genes by combined approaches of HDAC-inhibitors plus fenretinide, which inhibits cyclinD1, exhibit strong synergistic effects on induction of apoptosis. Furthermore, HDAC inhibition sensitizes rhabdoid tumor cell lines to cell death induced by chemotherapy., Conclusion: Our data demonstrate that HDAC inhibitor treatment in combination with fenretinide or conventional chemotherapy is a promising tool for the treatment of chemoresistant rhabdoid tumors.

Cancer stem cells (CSCs) are resistant to chemotherapy and are ability to regenerate cancer cell populations, thus attracting much attention in cancer research. In this report, we first demonstrated that sphere cells from ovarian cancer cell line A2780 shared many features of CSCs, such as resistance to cisplatin and able to initiate tumors in an efficient manner. Then, we conducted cDNA microarray analysis on spheres from ovarian A2780 cells, and from breast MCF7 and SUM159 cells, and found that molecular pathways underlying spheres from these cancer cell lines were similar to a large extent, suggesting that similar mechanisms are involved in the genesis of CSCs in both ovarian and breast cancer types. In addition, we showed that spheres from these cancer types were highly sensitive to fenretinide, a stimulus of oxidative stress-mediated apoptosis in cancer cells. Thus, our results not only provide important insights into mechanisms underlying CSCs in ovarian and breast cancer, but also lead to the development of more sophisticated protocols of cancer therapy in near future.

This study reports on the preparation and evaluation of amphiphilic macromolecules based on branched polyethylene glycol covalently linked with alkyl hydrocarbon chains. These macromolecules easily dissolved in an aqueous environment, with formation of micellar nanoaggregates endowed with hydrophobic inner cores capable of hosting fenretinide by complexation. The complexes increased fenretinide aqueous solubility, while hindering its release as a free drug in an aqueous environment. Particle size analysis indicated dimensional suitability of the complexes for intravenous administration. Neuroblastoma cell lines (SH-SY5Y and NGP) exhibited increased sensitivity to fenretinide in complex as compared to free drug, associated with higher intracellular concentrations of fenretinide observed after treatment with the complex. Transmission electronic microscopy images revealed endocytosis of the micellar complex. Moreover, fenretinide conversion to its metabolite 4-oxo-fenretinide was delayed in cells treated with the complex, further supporting the hypothesis that fenretinide may be absorbed by micellar transport and exposed to the cytoplasm for conversion to its metabolite only after micelle destabilization., (Copyright © 2012 Elsevier Inc. All rights reserved.)

The structural integrity of myelin formed by Schwann cells in the peripheral nervous system (PNS) is required for proper nerve conduction and is dependent on adequate expression of myelin genes including peripheral myelin protein 22 (PMP22). Consequently, excess PMP22 resulting from its genetic duplication and overexpression has been directly associated with the peripheral neuropathy called Charcot-Marie-Tooth disease type 1A (CMT1A), the most prevalent type of CMT. Here, in an attempt to identify transcriptional inhibitors with therapeutic value toward CMT1A, we developed a cross-validating pair of orthogonal reporter assays, firefly luciferase (FLuc) and β-lactamase (βLac), capable of recapitulating PMP22 expression, utilizing the intronic regulatory element of the human PMP22 gene. Each compound from a collection of approximately 3,000 approved drugs was tested at multiple titration points to achieve a pharmacological end point in a 1536-well plate quantitative high-throughput screen (qHTS) format. In conjunction with an independent counter-screen for cytotoxicity, the design of our orthogonal screen platform effectively contributed to selection and prioritization of active compounds, among which three drugs (fenretinide, olvanil, and bortezomib) exhibited marked reduction of endogenous Pmp22 mRNA and protein. Overall, the findings of this study provide a strategic approach to assay development for gene-dosage diseases such as CMT1A.

Systemic delivery of fenretinide in oral cancer chemoprevention trials has been largely unsuccessful due to dose-limiting toxicities and subtherapeutic intraoral drug levels. Local drug delivery, however, provides site-specific therapeutically relevant levels while minimizing systemic exposure. These studies evaluated the pharmacokinetic and growth-modulatory parameters of fenretinide mucoadhesive patch application on rabbit buccal mucosa. Fenretinide and blank-control patches were placed on right/left buccal mucosa, respectively, in eight rabbits (30 min, q.d., 10 days). No clinical or histological deleterious effects occurred. LC-MS/MS analyses of post-treatment samples revealed a delivery gradient with highest fenretinide levels achieved at the patch-mucosal interface (no metabolites), pharmacologically active levels in fenretinide-treated oral mucosa (mean: 5.65 μM; trace amounts of 4-oxo-4-HPR) and undetectable sera levels. Epithelial markers for cell proliferation (Ki-67), terminal differentiation (transglutaminase 1-TGase1) and glucuronidation (UDP-glucuronosyltransferase1A1-UGT1A1) exhibited fenretinide concentration-specific relationships (elevated TGase1 and UGT1A1 levels <5 μM, reduced Ki-67 indices >5 μM) relative to blank-treated epithelium. All fenretinide-treated tissues showed significantly increased intraepithelial apoptosis (TUNEL) positivity, implying activation of intersecting apoptotic and differentiation pathways. Human oral mucosal correlative studies showed substantial interdonor variations in levels of the enzyme (cytochrome P450 3A4-CYP3A4) responsible for conversion of fenretinide to its highly active metabolite, 4-oxo-4-HPR. Complementary in vitro assays in human oral keratinocytes revealed fenretinide and 4-oxo-4-HPR's preferential suppression of DNA synthesis in dysplastic as opposed to normal oral keratinocytes. Collectively, these data showed that mucoadhesive patch-mediated fenretinide delivery is a viable strategy to reintroduce a compound known to induce keratinocyte differentiation to human oral cancer chemoprevention trials.

Combination chemotherapy represents the standard-of-care for non-Hodgkin lymphoma. However, the development of new therapeutic regimens is empirical and this approach cannot be used prospectively to identify novel or optimal drug combinations. Quantitative system pharmacodynamic models could promote the discovery and development of combination regimens based upon first principles. In this study, we developed a mathematical model that integrates temporal patterns of drug exposure, receptor occupancy, and signal transduction to predict the effects of the CD20 agonist rituximab in combination with rhApo2L/TNF-related apoptosis inducing ligand or fenretinide, a cytotoxic retinoid, upon growth kinetics in non-Hodgkin lymphoma xenografts. The model recapitulated major regulatory mechanisms, including target-mediated disposition of rituximab, modulation of proapoptotic intracellular signaling induced by CD20 occupancy, and the relative efficacy of death receptor isoforms. The multiscale model coupled tumor responses to individual anticancer agents with their mechanisms of action in vivo, and the changes in Bcl-xL and Fas induced by CD20 occupancy were linked to explain the synergy of these drugs. Tumor growth profiles predicted by the model agreed with cell and xenograft data, capturing the apparent pharmacologic synergy of these agents with fidelity. Together, our findings provide a mechanism-based platform for exploring new regimens with CD20 agonists., (©2012 AACR.)

Objectives: The major limitation to successful chemotherapy of neuroblastoma (NB) is the toxicity and the poor bioavailability of traditional drugs., Methods: We synthesised an amphiphilic dextrin derivative (DX-OL) able to host fenretinide (4-HPR) by complexation. In this study, we have investigated the effects of 4-HPR-loaded amphipilic dextrin (DX-OL/4-HPR) in comparison with 4-HPR alone both in vitro on human NB cells and in vivo in pseudometastatic NB models. The haemolysis assay was used as a measure of the potential damage caused by the pharmaceutical formulation in vivo. Pharmacokinetic experiments were performed to assess drug plasma levels in mice treated with free or complexed 4-HPR., Key Findings: DX-OL/4-HPR exerted a more potent cytotoxic activity on NB cells. Complexed 4-HPR significantly increased the proportion of sub-G1 cells with respect to free 4-HPR. Dextrin derivatives showed no haemolytic activity, indicating their suitability for parenteral administration. DX-OL/4-HPR increased the lifespan and the long-term survival of treated mice over controls. The analysis of drug plasma levels indicates that the complexed drug has a higher AUC due to a reduced clearance from the blood., Conclusions: Our data suggest that DX-OL/4-HPR is an injectable formulation that is able to improve drug aqueous solubility and bioavailability., (© 2011 The Authors. JPP © 2011 Royal Pharmaceutical Society.)

Purpose: Adipokines are linked to obesity and insulin sensitivity and have recently been related to breast cancer risk and prognosis. We investigated the associations of plasma leptin and adiponectin with mammographic density and disease status and assessed their prognostic effect on recurrence-free survival in premenopausal women at risk for breast cancer., Patients and Methods: We measured circulating lipids, insulin-like growth factor 1, glucose, insulin and insulin sensitivity (calculated by homeostasis model assessment [HOMA] index), leptin, adiponectin, and leptin-to-adiponectin ratio in 235 premenopausal women with pT1mic/pT1a breast cancer (n = 21), intraepithelial neoplasia (n = 160), or 5-year Gail risk of 1.3% or greater (n = 54) who participated in a 2 × 2 trial of low-dose tamoxifen, fenretinide, both agents, or placebo over a 2-year period., Results: At baseline, adiponectin levels were directly associated with mammographic density and HDL cholesterol and negatively associated with leptin, leptin-to-adiponectin ratio, body mass index (BMI), and HOMA index. Median adiponectin levels were lower in affected than in unaffected women (P = .006). After a median of 7.2 years and total of 57 breast neoplastic events, there was a 12% reduction in the risk of breast neoplastic events per unit increase of adiponectin (adjusted hazard ratio, 0.88; 95% CI, 0.81 to 0.96; P = .03). There was no interaction between treatment and adiponectin levels., Conclusion: Low adiponectin levels are associated with a history of prior intraepithelial neoplasia or pT1mic/pT1a breast cancer and higher risk of second breast neoplastic events in premenopausal women. The associations are independent of BMI, mammographic density, and treatment. Our findings support the role of adiponectin as a potential target for premenopausal breast cancer prevention and treatment.

Purpose: Lestaurtinib (CEP-701), a multi-kinase inhibitor with potent activity against the Trk family of receptor tyrosine kinases, has undergone early phase clinical evaluation in children with relapsed neuroblastoma. We studied the interaction of CEP-701 with isotretinoin (13cRA) and fenretinide (4HPR), two retinoids that have been studied in children with high-risk neuroblastoma., Methods: In vitro growth inhibition was assessed following a 72-hour drug exposure using the sulforhodamine B (SRB) assay in eight neuroblastoma cell lines with variable TrkB expression. When appropriate, the combination index (CI) of Chou-Talalay was used to characterize the interaction of 13cRA (non-constant ratio) or 4HPR (constant ratio) with CEP-701., Results: The median (range) IC(50) of single-agent CEP-701 across all cell lines was 0.09 (0.08-0.3) μM. The combination of 13cRA and CEP-701 resulted in additive to synergistic interactions in four of the five cell lines studied. Addition of 1 or 5 μM of 13cRA decreased the median (range) CEP-701 IC(50) 1.5-fold (1.1-2.8-fold) and 1.7-fold (1.5-1.8-fold), respectively. With 10 μM 13cRA, less than 50% of cells survived when combined with various concentrations of CEP-701. The combination of 4HPR and CEP-701 trended toward being antagonistic, with a median (range) CI at the ED(50) of 1.3 (1.1-1.5)., Conclusions: The combination of 13cRA and CEP-701 was additive or synergistic in a spectrum of neuroblastoma cell lines, suggesting that these agents can be potentially studied together in the setting of minimal residual disease following intensive chemoradiotherapy for children with high-risk neuroblastoma.

Fenretinide and tamoxifen have additive antitumor effects preclinically. We performed a randomized, placebo-controlled, double-blind adjuvant trial in breast cancer patients treated for 5 years with tamoxifen, with or without fenretinide. Between October 1995 and October 1999, 426 postmenopausal women with hormone receptor-positive breast cancer were randomized. Patients were monitored for efficacy and toxicity. Four hundred and nineteen patients were evaluable. The study was terminated early due to slow accrual. There were no significant differences between treatment groups in DFS, TTR or survival. More patients stopped treatment early on the fenretinide arm than on placebo (P = 0.02). Grade 3/4 toxicities, including visual problems and musculoskeletal complaints were more common in patients receiving fenretinide (P = 0.007). A Night Blindness Questionnaire was used to monitor nyctalopia, which was slightly, but not significantly, more common on fenretinide. In this underpowered study, no significant difference was observed in efficacy between treatment groups. This trial provides important toxicity information about fenretinide, a retinoid that has been used in the prevention setting, because it is the only placebo-controlled, double-blind randomized study ever performed.

Purpose: Fenretinide (4-HPR) is a cytotoxic retinoid with minimal systemic toxicity that has shown clinical activity against recurrent high-risk neuroblastoma. To identify possible synergistic drug combinations for future clinical trials, we determined whether ABT-737, a small-molecule BH3-mimetic that inhibits most proteins of the antiapoptotic Bcl-2 family, could enhance 4-HPR activity in neuroblastoma., Experimental Design: Eleven neuroblastoma cell lines were tested for the cytotoxic activity of 4-HPR and ABT-737 as single agents and in combination using the DIMSCAN fluorescence digital imaging cytotoxicity assay. The effect of these agents alone and in combination on mitochondrial membrane depolarization and apoptosis (by flow cytometry), cytochrome c release, caspases, Bax-α, t-Bid, and Bak activation, and subcutaneous xenografts in nu/nu mice was also determined., Results: Multilog synergistic cytotoxicity was observed for the drug combination in all of the 11 neuroblastoma cell lines tested, including MDR lines and those insensitive to either drug as single agents. 4-HPR + ABT-737 induced greater mitochondrial membrane depolarization and mitochondrial cytochrome c release, greater activation of caspases, Bax-α, t-Bid, and Bak, and a higher level of apoptosis than either drug alone. In vivo, 4-HPR + ABT-737 increased the event-free survival of the MDR human neuroblastoma line CHLA-119 implanted subcutaneously in nu/nu mice (194.5 days for the combination vs. 68 days for ABT-737 and 99 days for 4-HPR)., Conclusion: Thus, the combination of 4-HPR with a BH3-mimetic drug warrants clinical trials in recurrent neuroblastoma.

Purpose: To determine the response rate to oral capsular fenretinide in children with recurrent or biopsy proven refractory high-risk neuroblastoma., Experimental Design: Patients received 7 days of fenretinide: 2,475 mg/m(2)/d divided TID (<18 years) or 1,800 mg/m(2)/d divided BID (≥18 years) every 21 days for a maximum of 30 courses. Patients with stable or responding disease after course 30 could request additional compassionate courses. Best response by course 8 was evaluated in stratum 1 (measurable disease on CT/MRI ± bone marrow and/or MIBG avid sites) and stratum 2 (bone marrow and/or MIBG avid sites only)., Results: Sixty-two eligible patients, median age 5 years (range 0.6-19.9), were treated in stratum 1 (n = 38) and stratum 2 (n = 24). One partial response (PR) was seen in stratum 2 (n = 24 evaluable). No responses were seen in stratum 1 (n = 35 evaluable). Prolonged stable disease (SD) was seen in 7 patients in stratum 1 and 6 patients in stratum 2 for 4 to 45+ (median 15) courses. Median time to progression was 40 days (range 17-506) for stratum 1 and 48 days (range 17-892) for stratum 2. Mean 4-HPR steady-state trough plasma concentrations were 7.25 μmol/L (coefficient of variation 40-56%) at day 7 course 1. Toxicities were mild and reversible., Conclusions: Although neither stratum met protocol criteria for efficacy, 1 PR + 13 prolonged SD occurred in 14/59 (24%) of evaluable patients. Low bioavailability may have limited fenretinide activity. Novel fenretinide formulations with improved bioavailability are currently in pediatric phase I studies., (©2011 AACR)

Purpose: To develop fenretinide oral mucoadhesive patch formulations and evaluate their in vitro and in vivo release performance for future site-specific chemoprevention of oral cancer., Methods: Solubilization of fenretinide in simulated saliva (SS) was studied by incorporating nonionic surfactants (Tween® 20 and 80, and Brij® 35 and 98), bile salts (sodium salt of cholic, taurocholic, glycocholic, and deoxycholic acids), phospholipid (lecithin), and novel polymeric solubilizer (Souplus®). Adhesive (polycarbophil: hydroxypropyl methylcellulose 4KM) and drug release (Fenretinide/Eudragit® RL PO with or without solubilizers) layers were prepared by solvent casting. Oral mucoadhesive patches were formed by attaching drug and adhesive layers onto backing layer (Tegaderm™ film). Physical state of drug in Eudragit® films was examined by X-ray diffraction (XRD). Evaluation of in vitro and in vivo fenretinide release from the patch was conducted in SS containing 5%w/v sodium deoxycholate and rabbits, respectively. Fenretinide was quantified by HPLC., Results: Tween® 20 and 80, Brij® 98, and sodium deoxycholate exhibited the highest fenretinide solubilization potential among the solubilizers. Drug loading efficiency in Eudragit® films was 90%-97%. XRD suggested fenretinide was amorphous in solubilizer-free and solubilizer-loaded films. Solubilizer-free patch exhibited poor in vitro and in vivo controlled drug release behavior. Increases in drug loading (5-10 wt%) or changes in polymeric matrix permeability did not provide continuous drug release. Co-incorporation of either single or mixed solubilizers in fenretinide/Eudragit® patches, (20 wt% Tween® 20, Tween® 80 and sodium deoxycholate or 20 wt% Tween® 80 + 40 wt% sodium deoxycholate solubilizers) led to significantly improved continuous in vitro/in vivo fenretinide release., Conclusion: Fenretinide/Eudragit® RL PO patches with 20 wt% Tween® 80 + 40 wt% sodium deoxycholate solubilizers exhibit excellent release behavior for further preclinical and/or clinical evaluation in oral cancer chemoprevention.

Purpose: Metastatic melanoma is characterized by extremely poor survival rates and hence novel therapies are urgently required. The ability of many anticancer drugs to activate autophagy, a lysosomal-mediated catabolic process which usually promotes cell survival, suggests targeting the autophagy pathway may be a novel means to augment therapy., Experimental Design: Autophagy and apoptosis were assessed in vitro in human melanoma cell lines in response to clinically achievable concentrations of the endoplasmic reticulum (ER) stress-inducing drugs fenretinide or bortezomib, and in vivo using a s.c. xenograft model., Results: Autophagy was activated in response to fenretinide or bortezomib in B-RAF wild-type cells, shown by increased conversion of LC3 to the autophagic vesicle-associated form (LC3-II) and redistribution to autophagosomes and autolysosomes, increased acidic vesicular organelle formation and autophagic vacuolization. In contrast, autophagy was significantly reduced in B-RAF-mutated melanoma cells, an effect attributed partly to oncogenic B-RAF. Rapamycin treatment was unable to stimulate LC3-II accumulation or redistribution in the presence of mutated B-RAF, indicative of de-regulated mTORC1-dependent autophagy. Knockdown of Beclin-1 or ATG7 sensitized B-RAF wild-type cells to fenretinide- or bortezomib-induced cell death, demonstrating a pro-survival function of autophagy. In addition, autophagy was partially reactivated in B-RAF-mutated cells treated with the BH3 mimetic ABT737 in combination with fenretinide or bortezomib, suggesting autophagy resistance is partly mediated by abrogated Beclin-1 function., Conclusions: Our findings suggest inhibition of autophagy in combination with ER stress-inducing agents may represent a means by which to harness autophagy for the therapeutic benefit of B-RAF wild-type melanoma., (©2011 AACR.)

Background: The synthetic retinoid fenretinide (N-(4-hydroxyphenyl)retinamide, 4-HPR) has shown promising anticancer activity in preclinical studies, but its limited oral bioavailability has hindered clinical assessment. A novel lipid matrix, Lym-X-Sorb (LXS), was evaluated to improve fenretinide bioavailability and attain higher plasma concentrations., Patients and Methods: Adults with refractory malignancies were administered fenretinide/LXS oral powder in 2 divided doses over 24 h for 7 consecutive days every 21 days in a standard phase I dose-escalation study with pharmacokinetic analysis., Results: The principal toxicities observed were diarrhea, reversible night blindness, and allergic reaction. The maximum tolerated dose regimens were 1,000 mg/m(2)/day divided into 2 daily doses for 7 days, every 21 days, and 800 mg/m(2)/day divided into 3 daily doses for 7 consecutive days, every 21 days., Conclusion: Better fenretinide formulations are needed to improve adult patient acceptability and compliance and to achieve the consistent systemic exposures associated with activity in preclinical models.