New-generation androgen receptor signaling inhibitors (ARSIs) in metastatic hormone-sensitive prostate cancer (mHSPC): pharmacokinetics, drug-drug interactions (DDIs), and clinical impact.

INTRODUCTION: The therapeutic scenario of metastatic hormone-sensitive prostate cancer (mHSPC) has dramatically changed in recent years, with the approval of new-generation Androgen Receptor Signaling Inhibitors (ARSIs), in combination with the androgen deprivation therapy (ADT), which was the previous standard of care. Despite showing a similar clinical efficacy, ARSIs, all of which are administered orally, are different in terms of pharmacokinetic and drug-drug interactions (DDIs). AREAS COVERED: This review covers the main pharmacokinetic characteristics of ARSIs that have been approved for the first-line therapy of mHSPC patients, underlying the differences among these molecules and focusing on the known or possible interactions with other drugs. Full-text articles and abstracts were searched in PubMed. EXPERT OPINION: Since prostate cancer occurs mainly in older age, comorbidities and the consequent polypharmacy increase the DDI risk in mHSPC patients who are candidates for ARSI. Waiting for new therapeutic options, in the absence of direct comparisons, pharmacokinetic knowledge is essential to guide clinicians in prescribing ARSI in this setting.

Activity and safety of SHR3680, a novel antiandrogen, in patients with metastatic castration-resistant prostate cancer: a phase I/II trial.

BACKGROUND: Antagonizing the androgen-receptor (AR) pathway is an effective treatment strategy for patients with metastatic castration-resistant prostate cancer (CRPC). Here, we report the results of a first-in-human phase 1/2 study which assessed the safety, pharmacokinetics, and activity of SHR3680 (a novel AR antagonist) in patients with metastatic CRPC. METHODS: This phase 1/2 study enrolled patients with progressive metastatic CRPC who had not been previously treated with novel AR-targeted agents. In the phase 1 dose-escalation portion, patients received oral SHR3680 at a starting daily dose of 40 mg, which was subsequently escalated to 80 mg, 160 mg, 240 mg, 360 mg, and 480 mg per day. In phase 2 dose-expansion portion, patients were randomized to receive daily dose of 80 mg, 160 mg, or 240 mg of SHR3680. The primary endpoint in phase 1 was safety and tolerability and in phase 2 was the proportion of patients with a prostate-specific antigen (PSA) response (≥ 50% decrease of PSA level) at week 12. RESULTS: A total of 197 eligible patients were enrolled and received SHR3680 treatment, including 18 patients in phase 1 and 179 patients in phase 2. No dose-limiting toxicities were reported and the maximum tolerated dose was not reached. Treatment-related adverse events (TRAEs) occurred in 116 (58.9%) patients, with the most common one being proteinuria (13.7%). TRAEs of grade ≥ 3 occurred in only 23 (11.7%) patients, and no treatment-related deaths occurred. Antitumor activities were evident at all doses, including PSA response at week 12 in 134 (68.0%; 95% CI, 61.0-74.5) patients, stabilized bone disease at week 12 in 174 (88.3%; 95% CI, 87.2-95.5) patients, and responses in soft tissue lesions in 21 (34.4%, 95% CI, 22.7-47.7) of 61 patients. CONCLUSION: SHR3680 was well tolerated and safe, with promising anti-tumor activity across all doses tested in patients with metastatic CRPC. The dose of 240 mg daily was recommended for further phase 3 study. TRIAL REGISTRATION: Clinical trials.gov NCT02691975; registered February 25, 2016.

Pharmacokinetics and Use-Testing of Apalutamide Prepared in Aqueous Food Vehicles for Alternative Administration.

Patients may have difficulty swallowing a whole daily dose of 240 mg (4 × 60-mg tablets) of apalutamide. One of the unique properties of apalutamide tablets is easy disintegration and dispersion when mixed into aqueous vehicles, avoiding the need to crush/split the tablets. To evaluate whether this method of apalutamide tablet administration would be conducive in a patient setting, different variations in preparation were evaluated, and one preparation was tested in humans. In vitro compatibility studies evaluated purity, dose, or stability of different variations of apalutamide in applesauce/yogurt/orange juice/green tea. An open-label, randomized, crossover phase 1 study in healthy men determined the bioavailability of an apalutamide-applesauce mixture versus whole tablets based on maximum plasma analyte concentration (Cmax ), area under the plasma analyte concentration-time curve: AUC0-72h and AUC0-168h . Different amounts of applesauce/yogurt/orange juice/green tea as well as durations (up to 6 hours) did not affect the total apalutamide content available. The phase 1 study (n = 12) showed increased total exposure of 5% and peak exposure of 27.6% when comparing the apalutamide-applesauce mixture with whole-tablet administration. Variations in preparation times and total content for applesauce/yogurt/orange juice/green tea did not affect the purity, dose, or stability of apalutamide. An apalutamide-applesauce mixture is a suitable alternative administration method to whole tablets.

A Phase 1 Study to Investigate the Effects of Cortexolone 17α-Propionate, Also Known as Clascoterone, on the QT Interval Using the Meal Effect to Demonstrate ECG Assay Sensitivity.

Cortexolone 17α-propionate, also known as clascoterone, is a potent androgen receptor inhibitor intended for the topical treatment of skin diseases associated with androgenic pathway alterations. In nonclinical studies, cortexolone 17α-propionate was found to have a weak inhibitory effect on human Ether-à-go-go-Related Gene (hERG) potassium channels, which are vital for normal electrical activity in the heart. When used in a cream formulation, little cortexolone 17α-propionate is absorbed. However, the solution formulation developed for the treatment of androgenetic alopecia leads to a measurable systemic concentration and accumulation of the antiandrogen. This phase 1 study assessed the effect of cortexolone 17α-propionate on the QTc interval using concentration-effect analysis and the effect of a meal on QTc to confirm assay sensitivity. Thirty-two volunteers were randomly assigned to receive the active drug or a matching vehicle as placebo. Participants were dosed twice daily on days 1 to 3 (225 mg applied topically as a 7.5% solution 12 hours apart) and once on day 4. Pharmacokinetic and electrocardiogram assessments were performed after supratherapeutic doses. Assay sensitivity was successfully confirmed by using the food effect on the QTc interval. The results of this concentration-QTc analysis demonstrate that cortexolone 17α-propionate and its metabolite/degradation product had no effect on the QTc interval in the concentration range tested.

Next generation risk assessment of human exposure to anti-androgens using newly defined comparator compound values.

Next Generation Risk Assessment (NGRA) can use the so-called Dietary Comparator Ratio (DCR) to evaluate the safety of a defined exposure to a compound of interest. The DCR compares the Exposure Activity Ratio (EAR) for the compound of interest, to the EAR of an established safe level of human exposure to a comparator compound with the same putative mode of action. A DCR ≤ 1 indicates the exposure evaluated is safe. The present study aimed at defining adequate and safe comparator compound exposures for evaluation of anti-androgenic effects, using 3,3-diindolylmethane (DIM), from cruciferous vegetables, and the anti-androgenic drug bicalutamide (BIC). EAR values for these comparator compounds were defined using the AR-CALUX assay. The adequacy of the new comparator EAR values was evaluated using PBK modelling and by comparing the generated DCRs of a series of test compound exposures to actual knowledge on their safety regarding in vivo anti-androgenicity. Results obtained supported the use of AR-CALUX-based comparator EARs for DCR-based NGRA for putative anti-androgenic compounds. This further validates the DCR approach as an animal free in silico/in vitro 3R compliant method in NGRA.

Evaluation of dietary dose administration as an alternative to oral gavage in the rodent uterotrophic and Hershberger assays.

The rodent uterotrophic and Hershberger assays evaluate potential estrogenic and (anti)-androgenic effects, respectively. Both US EPA and OECD guidelines specify that test substance is administered daily either by subcutaneous injection or oral gavage. However, dietary administration is a relevant exposure route for agrochemical regulatory toxicology studies due to potential human intake via crop residues. In this study, equivalent doses of positive control chemicals administered via dietary and gavage routes of administration were compared in the uterotrophic (17α-ethinyl estradiol) and Hershberger (flutamide, linuron, dichloro-2,2-bis(4-chlorophenyl) ethane; 4,4'-DDE) assays in ovariectomized and castrated rats, respectively. For all positive control chemicals tested, statistically significant changes in organ weights and decreases in food consumption were observed by both routes of test substance administration. Decreased body weight gain observed for dietary linuron and 4,4'-DDE indicated that the maximum tolerated dose was exceeded. Hershberger dietary administration resulted in a similar blood exposure (AUC24) for each positive control chemical when compared to gavage. Overall, the correlation in organ weight changes for both the uterotrophic and Hershberger assays suggest that dietary administration is an acceptable route of exposure with similar sensitivity to oral gavage dosing for evaluation of the endocrine potential of a test substance and represents a more appropriate route of test substance administration for most environmental exposure scenarios.

Androgen receptor signalling impairs docetaxel efficacy in castration-resistant prostate cancer.

Androgen receptor (AR) signalling drives neoplastic growth and therapy resistance in prostate cancer. Recent clinical data show that docetaxel combined with androgen deprivation therapy improves outcome in hormone-sensitive disease. We studied whether testosterone and AR signalling interferes with docetaxel treatment efficacy in castration-resistant prostate cancer (CRPC). We found that testosterone supplementation significantly impaired docetaxel tumour accumulation in a CRPC model, resulting in decreased tubulin stabilisation and antitumour activity. Furthermore, testosterone competed with docetaxel for uptake by the drug transporter OATP1B3. Irrespective of docetaxel-induced tubulin stabilisation, AR signalling by testosterone counteracted docetaxel efficacy. AR-pathway activation could also reverse long-term tumour regression by docetaxel treatment in vivo. These results indicate that to optimise docetaxel efficacy, androgen levels and AR signalling need to be suppressed. This study lends evidence for continued maximum suppression of AR signalling by combining targeted therapeutics with docetaxel in CRPC.

Quantitative in vitro-to-in vivo extrapolation (QIVIVE) of estrogenic and anti-androgenic potencies of BPA and BADGE analogues.

The goal of the present study was to obtain an in vivo relevant prioritization method for the endocrine potencies of different polycarbonate monomers, by combining in vitro bioassay data with physiologically based kinetic (PBK) modelling. PBK models were developed for a selection of monomers, including bisphenol A (BPA), two bisphenol F (BPF) isomers and four different bisphenol A diglycidyl ethers (BADGEs), using in vitro input data. With these models, the plasma concentrations of the compounds were simulated, providing means to estimate the dose levels at which the in vitro endocrine effect concentrations are reached. The results revealed that, whereas the in vitro relative potencies of different BADGEs (predominantly anti-androgenic effects) can be up to fourfold higher than BPA, the estimated in vivo potencies based on the oral equivalent doses are one to two orders of magnitude lower than BPA because of fast detoxification of the BADGEs. In contrast, the relative potencies of 2,2-BPF and 4,4-BPF increase when accounting for the in vivo availability. 4,4-BPF is estimated to be fivefold more potent than BPA in humans in vivo in inducing estrogenic effects and both 2,2-BPF and 4,4-BPF are estimated to be, respectively, 7 and 11-fold more potent in inducing anti-androgenic effects. These relative potencies were considered to be first-tier estimates, particularly given that the potential influence of intestinal metabolism on the in vivo availability was not accounted for. Overall, it can be concluded that both 2,2-BPF and 4,4-BPF are priority compounds.

Cyproterone acetate-loaded nanostructured lipid carriers: effect of particle size on skin penetration and follicular targeting.

Cyproterone acetate (CPA) is used to treat various skin disorders such as acne, hirsutism, and alopecia. Due to the limited skin penetration of CPA, nanostructured lipid carriers (NLCs) with different size ranges were considered in this study in order to enhance skin penetration and to target hair follicles. Drug loading, drug release and morphological assessment were evaluated for each targeted size (100, 300, and 600 nm). Ex vivo skin penetration was also investigated using Franz diffusion cells. Finally, in vivo follicular targeting was evaluated using rhodamine B-loaded micro and nanoparticles. Results revealed that 60-85% of drug was slowly released from lipid nanoparticles within 72 h. CPA-NLC with average diameter of 600 nm had better penetration and deposition in dermis-epidermis layer, also CPA-NLC 100 and 300 nm significantly increased drug penetration in dermis-epidermis in comparison to free CPA. Follicular targeting results revealed that NLC 300 nm had the best accumulation capacity in hair follicles. CPA-NLC with average diameter of 300 nm could be a promising topical novel drug delivery system for specific targeting of hair follicles and sebaceous glands to treat androgenic skin disorders such as acne, hirsutism, and alopecia.

Apalutamide and its use in the treatment of prostate cancer.

High-risk nonmetastatic castration-resistant prostate cancer is a lethal disease that previously lacked clear treatment options. Progression to bone metastases is associated with significant morbidity and high cost. Apalutamide, an androgen receptor inhibitor, has substantial clinical response in nonmetastatic castration-resistant prostate cancer. Apalutamide + androgen deprivation therapy is well tolerated and improves metastasis-free survival, progression-free survival and time to symptomatic progression, and is associated with a favorable trend of improved overall survival. Future research is needed to elucidate mechanisms of resistance to treatment with androgen signaling inhibitors.

Impact of age on exposure to oral antiandrogen therapies in clinical practice.

BACKGROUND: Oral antiandrogen therapies are predominantly used in older men, but real-life studies evaluating the impact of age on pharmacokinetic exposure are lacking. This study aims to evaluate the impact of age on the pharmacokinetic profiles of abiraterone acetate and enzalutamide in clinical practice. PATIENTS AND METHODS: Retrospective observational study to evaluate the impact of age on the first steady-state sample of patients treated with abiraterone acetate or enzalutamide in routine daily clinical practice. The effect of age on target attainment was assessed. RESULTS: For abiraterone acetate and enzalutamide, 71 and 64 patients were included, respectively. Baseline patients' characteristics and administered doses were not age-dependent. No age-related differences were observed in exposure to the main metabolites of abiraterone acetate, except for active metabolite Δ(4)-Abiraterone (D4A) with a median plasma concentration of 2.5 × 10-3 mg/L in the oldest versus 1.3 × 10-3 mg/L in the youngest age quartile (coefficient of variation, CV, 72%, p = 0.03). For enzalutamide, no significant differences in exposure were found, except for carboxylic acid enzalutamide, having a median plasma concentration of 5.8 mg/L versus 3.9 mg/L in the oldest versus the youngest age quartile (CV 66%, p = 0.03). However, this was driven by one patient aged 99 years old. Age had no significant influence on target attainment of either compound. CONCLUSIONS: This study showed no significant impact of age on the pharmacokinetic profiles of abiraterone acetate and enzalutamide, except for the active metabolite D4A and the inactive metabolite carboxylic acid enzalutamide, both having significantly higher exposure in older males. Target attainments of abiraterone and enzalutamide were not significantly affected by age, which suggests that age has no clinically relevant impact on exposure to these oral antiandrogen therapies. However, the clinical impact of higher exposure to D4A in older males remains undetermined.

Novel Trifluoromethylated Enobosarm Analogues with Potent Antiandrogenic Activity In Vitro and Tissue Selectivity In Vivo.

Prostate cancer often develops antiandrogen resistance, possibly via androgen receptor (AR) mutations, which change antagonists to agonists. Novel therapies with increased anticancer activity, while overcoming current drug resistance are urgently needed. Enobosarm has anabolic effects on muscle and bone while having no effect on the prostate. Here, we describe the activity of novel chemically modified enobosarm analogues. The rational addition of bis-trifluoromethyl groups into ring B of enobosarm, profoundly modified their activity, pharmacokinetic and tissue distribution profiles. These chemical structural modifications resulted in an improved AR binding affinity-by increasing the molecular occupational volume near helix 12 of AR. In vitro, the analogues SK33 and SK51 showed very potent antiandrogenic activity, monitored using LNCaP/AR-Luciferase cells where growth, PSA and luciferase activity were used as AR activity measurements. These compounds were 10-fold more potent than bicalutamide and 100-fold more potent than enobosarm within the LNCaP model. These compounds were also active in LNCaP/BicR cells with acquired bicalutamide resistance. In vivo, using the AR-Luc reporter mice, these drugs showed potent AR inhibitory activity in the prostate and other AR-expressing tissues, e.g., testes, seminal vesicles, and brain. These compounds do not inhibit AR activity in the skeletal muscle, and spleen, thus indicating a selective tissue inhibitory profile. These compounds were also active in vivo in the Pb-Pten deletion model. SK33 and SK51 have significantly different and enhanced activity profiles compared with enobosarm and are ideal candidates for further development for prostate cancer therapy with potentially fewer side effects. Mol Cancer Ther; 17(9); 1846-58. ©2018 AACR.

Validated Chiral LC-ESI-MS/MS Method for the Simultaneous Quantification of Darolutamide Diastereomers and Its Active Metabolite in Mice Plasma: Application to a Pharmacokinetic Study.

A simple, selective and reliable LC-MS/MS method was developed and validated for the simultaneous quantitation of darolutamide diastereomers (diastereomer-1 and diastereomer-2) and its active metabolite i. e. ORM-15341 in mice plasma using warfarin as an internal standard (IS) as per the regulatory guidelines. Plasma samples were extracted by liquid-liquid extraction and the chromatographic separation was achieved on a Chiralpak IA column with an isocratic mobile phase 5 mM ammonium acetate:absolute alcohol (20:80, v/v) at a flow rate of 1.0 mL/min. Detection and quantitation was done by multiple reaction monitoring on a triple quadrupole mass spectrometer following the transitions: m/z 397→202, 395→202 and 307→250 for darolutamide diastereomers, ORM-15341 and the IS, respectively in the negative ionization mode. The calibration curves were linear (r>0.992) in the range of 100-2400 ng/mL for all the analytes. The intra- and inter-day precisions were in the range of 1.25-10.2 and 1.58-12.3; 2.85-5.68 and 1.85-9.58; 2.34-12.1 and 2.58-7.38 for diastereomer-1, diastereomer-2 and ORM-15341, respectively. Both diastereomers and ORM-15341 were found to be stable under different stability conditions. The validated method was applied to a pharmacokinetic study in mice.

In silico binding of 4,4'-bisphenols predicts in vitro estrogenic and antiandrogenic activity.

Bisphenols, anthropogenic pollutants, leach from consumer products and have potential to be ingested and are excreted in waste. The endocrine disrupting effects of highly manufactured bisphenols (BPA, BPS, and BPF) are known, however the activities of others are not. Here, the estrogenic and androgenic activities of a series of 4,4'-bisphenols that vary at the inter-connecting bisphenol bridge were determined (BPA, BPB, BPBP, BPC2, BPE, BPF, BPS, and BPZ) and compared to in silico binding to estrogen receptor-alpha and the androgen receptor. Bioassay results showed the order of estrogenicity (BPC2 (strongest) > BPBP > BPB > BPZ > BPE > BPF > BPA > BPS, r2 = 0.995) and anti-androgenicity (BPC2 (strongest) > BPE, BPB, BPA, BPF, and BPS, r2 = 0.996) correlated to nuclear receptor binding affinities. Like testosterone and the anti-androgen hydroxyflutamide, bisphenol fit in the ligand-binding domain through hydrogen-bonding at residues Thr877 and Asn705, but also interacted at either Cys784/Ser778 or Gln711 through the other phenol ring. This suggests the 4,4'-bisphenols, like hydroxyflutamide, are androgen receptor antagonists. Hydrogen-bond trends between ERα and the 4,4'-bisphenols were limited to residue Glu353, which interacted with the -OH of one phenol and the -OH of the A ring of 17ß-estradiol; hydrogen-bonding varied at the -OH of ring D of 17ß-estradiol and the second phenol -OH group. While both estrogen and androgen bioassays correlated to in silico results, conservation of hydrogen-bonding residues in the androgen receptor provides a convincing picture of direct antagonist binding by 4,4'-bisphenols.

Transdermal Delivery of Luteinizing Hormone-releasing Hormone with Chitosan Microneedles: A Promising Tool for Androgen Deprivation Therapy.

Long-term administration of luteinizing hormone-releasing hormone analogs (LHRHa) is the main type of androgen-deprivation therapy (ADT) for lethal prostate cancer. A fully insertable microneedle system, composed of embeddable chitosan microneedles and a dissolvable polyvinyl alcohol/polyvinyl pyrrolidone supporting array, was developed for sustained delivery of LHRHa to the skin. A porcine cadaver skin test showed that chitosan microneedles can be fully embedded within the skin and microneedle-created micropores reseal within 7 days. The measured LHRHa loading amount was 73.3±2.8 µg per microneedle patch. After applying goserelin-containing microneedles to mice, serum LH levels increased initially and then declined below baseline at day 7. In contrast, serum testosterone levels increased to reach a peak at day 14 and then declined to a castration level at day 21. Additionally, such a castration level was maintained for 2 weeks. Therefore, transdermal delivery of goserelin with embeddable chitosan microneedles can produce a castrated state in mice. Such a system is a promising, feasible means of delivering ADT.

Androgen deprivation therapy for the treatment of prostate cancer: a focus on pharmacokinetics.

INTRODUCTION: Medical therapy has undergone many changes as our understanding of prostate cancer cell biology has improved. Androgen deprivation therapy (ADT) remains the mainstay of therapy for metastatic disease. Metastatic castrate-resistant prostate cancer (CRPC) is an important concern since we are unable to stop progression with currently available agents. Areas covered: Pharmacologic ADT is the most commonly used treatment for metastatic prostate cancer. Multiple agents are available for both first-line and second-line use: antiandrogens, estrogens, luteinizing hormone-releasing hormone agonists/antagonists, and CYP17 inhibitors. With adoption of these drugs, it is important to consider their pharmacokinetic and pharmacodynamic properties. Many undergo metabolism through cytochrome P450. Levels may be altered with co-administration of drugs acting as enzyme inhibitors or inducers. Understanding mechanism of action, metabolism, and excretion of these drugs allows clinicians to provide the best therapeutic care while minimizing adverse events. Expert opinion: Many men with metastatic prostate cancer will progress to castration resistance. An understanding of resistance mechanisms at the cellular level has revealed new drug targets with hopes of halting or reversing progression of metastatic disease. Second-line agents, traditionally reserved for CRPC, are being studied in metastatic castrate-sensitive prostate cancer, and may offer practice-changing evidence supporting their use.

Relation between plasma trough concentration of abiraterone and prostate-specific antigen response in metastatic castration-resistant prostate cancer patients.

BACKGROUND: Abiraterone (ABI) is a major oral agent for the treatment of metastatic castration-resistant prostate cancer (mCRPC) patients but its systemic exposure is subject to a large inter-individual variability. We aimed to explore the relationship between ABI trough plasma concentration and prostate-specific antigen (PSA) response in mCRPC patients and to identify the critical determinants for its activity. PATIENTS AND METHODS: This is a monocentric prospective observational study in mCRPC patients treated with ABI. The plasmatic concentration of ABI at steady state was measured using liquid chromatography with fluorescence detection. The primary objective was to study the relationship between mean ABI plasma exposure (ABI Cmin) and 3-month PSA response. RESULTS: From 2012 to 2016, 61 mCRPC patients were eligible for pharmacokinetic/pharmacodynamic assessment. Thirty-eight patients experienced PSA response (62%, [confidence interval {CI} 95% 50-78]). In univariate analysis, ABI Cmin was 1.5-fold higher in responders: 12.0 ng/mL (CI 95% 9.4-15.6) versus 8.0 ng/mL (CI 95% 5.8-11.6; P = 0.0015). In multivariate analysis, only ABI Cmin was independently associated with PSA response (odds ratio = 1.12 [CI 95% 1.01-1.25], P = 0.004). By receiver operating characteristic analysis, the optimal threshold for ABI Cmin was 8.4 ng/mL. Progression-free survival (PFS) was significantly higher in patients with ABI Cmin above 8.4 ng/mL (hazard ratio 0.55, [CI 95% 0.31-0.99], 12.2 [CI 95% 9.2-19.5] versus 7.4 [CI 95% 5.5-14.7] months otherwise, P = 0.044). CONCLUSIONS: We showed that ABI trough concentration correlates with PSA response and PFS. Moreover, we could determine a cut-off value of plasmatic concentration for PSA response. Altogether, ABI concentration monitoring appears as a new approach to improve clinical outcome in mCPRC patients.

Targeting prostate cancer with compounds possessing dual activity as androgen receptor antagonists and HDAC6 inhibitors.

While enzalutamide and abiraterone are approved for treatment of metastatic castration-resistant prostate cancer (mCRPC), approximately 20-40% of patients have no response to these agents. It has been stipulated that the lack of response and the development of secondary resistance to these drugs may be due to the presence of AR splice variants. HDAC6 has a role in regulating the androgen receptor (AR) by modulating heat shock protein 90 (Hsp90) acetylation, which controls the nuclear localization and activation of the AR in androgen-dependent and independent scenarios. With dual-acting AR-HDAC6 inhibitors it should be possible to target patients who don't respond to enzalutamide. Herein, we describe the design, synthesis and biological evaluation of dual-acting compounds which target AR and are also specific towards HDAC6. Our efforts led to compound 10 which was found to have potent dual activity (HDAC6 IC50=0.0356µM and AR binding IC50=<0.03µM). Compound 10 was further evaluated for antagonist and other cell-based activities, in vitro stability and pharmacokinetics.

In vitro metabolism of methiocarb and carbaryl in rats, and its effect on their estrogenic and antiandrogenic activities.

In this work, we examined the metabolism of the carbamate insecticides methiocarb and carbaryl by rat liver microsomes and plasma, and its effect on their endocrine-disrupting activities. Methiocarb and carbaryl were not enzymatically hydrolyzed by rat liver microsomes, but were hydrolyzed by rat plasma, mainly to methylthio-3,5-xylenol (MX) and 1-naphthol, respectively. When methiocarb was incubated with rat liver microsomes in the presence of NADPH, methiocarb sulfoxide was formed. The hydrolysis product, MX, was also oxidized to the sulfoxide, 3,5-dimethyl-4-(methylsulfinyl)phenol (SP), by rat liver microsomes in the presence of NADPH. These oxidase activities were catalyzed by cytochrome P450 and flavin-containing monooxygenase. Methiocarb and carbaryl both exhibited estrogen receptor α (ERα) and ERß agonistic activity. MX and 1-naphthol showed similar activities, but methiocarb sulfoxide and SP showed markedly decreased activities. On the other hand, methiocarb and carbaryl exhibited potent antiandrogenic activity in the concentration range of 1×10(-6)-3×10(-5) M. Their hydrolysis products, MX, and 1-naphthol also showed high activity, equivalent to that of flutamide. However, methiocarb sulfoxide and SP showed relatively low activity. Thus, hydrolysis of methiocarb and carbaryl and oxidation of methiocarb to the sulfoxide markedly modified the estrogenic and antiandrogenic activities of methiocarb and carbaryl.

Development of Suppositories Containing Flutamide-Loaded Alginate-Tamarind Microparticles for Rectal Administration: In Vitro and in Vivo Studies.

In the present work the absorption of flutamide from suppositories containing hydrophilic tamarind alginate microparticles after rectal administration in rats was investigated with the purpose of enhancing bioavailability and to avoid hepatic toxicity. Microparticles were developed by ionic gelation method and optimized using one factorial design of response surface methodology. The optimized batch of microparticles had tamarind gum-sodium alginate (1 : 3) ratio and showed entrapment efficiency 94.969% and mucoadhesion strength 94.646% with desirability of 0.961. Suppositories loaded with microparticles were developed by fusion method using poloxamer 407 and poloxamer 188 in combination as suppository base. Kinetic analysis of the release data of microparticle-loaded suppositories showed time-independent release of drug. Higher values of 'n' (>0.89) represent Super Case II-type drug release. The pharmacokinetics of flutamide from flutamide tamarind alginate microparticle-loaded suppository were compared with oral suspension. Cmax of microparticle-loaded suppository was significantly larger than that of oral suspension (1.711 and 0.859 µg/mL, respectively).