Bergamottin a CYP3A inhibitor found in grapefruit juice inhibits prostate cancer cell growth by downregulating androgen receptor signaling and promoting G0/G1 cell cycle block and apoptosis

Prostate cancer is the second leading cause of cancer related death in American men. Several therapies have been developed to treat advanced prostate cancer, but these therapies often have severe side effects. To improve the outcome with fewer side effects we focused on the furanocoumarin bergamottin, a natural product found in grapefruit juice and a potent CYP3A inhibitor. Our recent studies have shown that CYP3A5 inhibition can block androgen receptor (AR) signaling, critical for prostate cancer growth. We observed that bergamottin reduces prostate cancer (PC) cell growth by decreasing both total and nuclear AR (AR activation) reducing downstream AR signaling. Bergamottin’s role in reducing AR activation was confirmed by confocal microscopy studies and reduction in prostate specific antigen (PSA) levels, which is a marker for prostate cancer. Further studies revealed that bergamottin promotes cell cycle block and accumulates G0/G1 cells. The cell cycle block was accompanied with reduction in cyclin D, cyclin B, CDK4, P-cdc2 (Y15) and P-wee1 (S642). We also observed that bergamottin triggers apoptosis in prostate cancer cell lines as evident by TUNEL staining and PARP cleavage. Our data suggests that bergamottin may suppress prostate cancer growth, especially in African American (AA) patients carrying wild type CYP3A5 often presenting aggressive disease.

Evaluation of 1β-Hydroxylation of Deoxycholic Acid as a Non-Invasive Urinary Biomarker of CYP3A Activity in the Assessment of Inhibition-Based Drug–Drug Interaction in Healthy Volunteers

In this study, we aimed to evaluate the utility of endogenous 1β-hydroxy-deoxycholic acid/total deoxycholic acid ratio (1β-OH-DCA/ToDCA) in spot urine as a surrogate marker of cytochrome P450 3A (CYP3A) activity in the assessment inhibition-based drug–drug interactions in healthy volunteers. This was accomplished through an open-label, three-treatment parallel-arm study in healthy male volunteers from Zimbabwe. Each group received itraconazole (ITZ; 100 mg once daily; n = 10), fluconazole (FKZ; 50 mg once daily; n = 9), or alprazolam (APZ; 1 mg once daily; n = 8) orally. Midazolam (MDZ), dosed orally and intravenously, was used as a comparator to validate the exploratory measures of CYP3A activity and the effects of known inhibitors. Urinary metabolic ratios of 1β-OH-DCA/ToDCA before and after CYP3A inhibitor treatment showed a similar magnitude of inhibitory effects of the three treatments as that measured by oral MDZ clearance. The maximum inhibition effect of a 75% reduction in the 1β-OH-DCA/ToDCA ratio compared to the baseline was achieved in the ITZ group following six once-daily doses of 100 mg. The correlations of the two markers for CYP3A inhibitor treatment were significant (rs = 0.53, p < 0.01). The half-life of urinary endogenous 1β-OH-DCA/ToDCA was estimated as four days. These results suggested that 1β-OH-DCA/ToDCA in spot urine is a promising convenient, non-invasive, sensitive, and relatively quickly responsive endogenous biomarker that can be used for CYP3A inhibition-based drug–drug interaction in clinical studies.

Bergamottin a CYP3A inhibitor found in grapefruit juice inhibits prostate cancer cell growth by downregulating androgen receptor signaling causing cell cycle block and apoptosis

Prostate cancer is the second leading cause of cancer related death in American men. Several therapies have been developed to treat advanced prostate cancer, but these therapies often have severe side effects. To improve the outcome with fewer side effects we focused on the furanocoumarin bergamottin, a natural product found in grapefruit juice and a potent CYP3A inhibitor. Our recent studies have shown that CYP3A5 inhibition can block androgen receptor (AR) signaling, critical for prostate cancer growth. We observed that bergamottin reduces prostate cancer (PC) cell growth by decreasing both total and nuclear AR (AR activation) reducing downstream AR signaling. Bergamottins role in reducing AR activation was confirmed by confocal microscopy studies and reduction in PSA levels. Further studies revealed that bergamottin promotes cell cycle block and accumulates G0/G1 cells. The cell cycle block was accompanied with reduction in cyclin D, cyclin B, CDK4, P-cdc2 (Y15) and P-wee1 (S642). We also observed that bergamottin triggers apoptosis in prostate cancer cell lines as evident by TUNEL staining and PARP cleavage. Our data suggest that bergamottin may be used as an adjunctive nutritional supplement to suppress prostate cancer growth and is of relevance to AA patients carrying wild type CYP3A5 often presenting aggressive disease.

The pharmacokinetics of pamiparib in the presence of a strong CYP3A inhibitor (itraconazole) and strong CYP3A inducer (rifampin) in patients with solid tumors: an open-label, parallel-group phase 1 study

Purpose Pamiparib is an investigational, selective, oral poly(ADP-ribose) polymerase 1/2 (PARP1/2) inhibitor that has demonstrated PARP–DNA complex trapping and CNS penetration in preclinical models, as well as preliminary anti-tumor activity in early-phase clinical studies. We investigated whether the single-dose pharmacokinetic (PK) profile of pamiparib is altered by coadministration of a strong CYP3A inducer (rifampin) or a strong CYP3A inhibitor (itraconazole) in patients with solid tumors. Methods In this open-label, phase 1 study, adults with advanced solid tumors received either oral pamiparib 60 mg (days 1 and 10) and once-daily oral rifampin 600 mg (days 3–11) or oral pamiparib 20 mg (days 1 and 7) and once-daily oral itraconazole 200 mg (days 3–8). Primary endpoints included pamiparib maximum observed concentration (Cmax), and area under the plasma concentration–time curve from zero to last quantifiable concentration (AUC0–tlast) and infinity (AUC0–inf). Secondary endpoints included safety and tolerability. Results Rifampin coadministration did not affect pamiparib Cmax (geometric least-squares [GLS] mean ratio 0.94; 90% confidence interval 0.83–1.06), but reduced its AUC0–tlast (0.62 [0.54–0.70]) and AUC0–inf (0.57 [0.48–0.69]). Itraconazole coadministration did not affect pamiparib Cmax (1.05 [0.95–1.15]), AUC0–tlast (0.99 [0.91–1.09]), or AUC0–inf (0.99 [0.90–1.09]). There were no serious treatment-related adverse events. Conclusions Pamiparib plasma exposure was reduced 38–43% with rifampin coadministration but was unaffected by itraconazole coadministration. Pamiparib dose modifications are not considered necessary when coadministered with CYP3A inhibitors. Clinical safety and efficacy data will be used with these results to recommend dose modifications when pamiparib is coadministered with CYP3A inducers.

Concentration–QTc analysis of quizartinib in patients with relapsed/refractory acute myeloid leukemia

Purpose This analysis evaluated the relationship between concentrations of quizartinib and its active metabolite AC886 and QT interval corrected using Fridericia’s formula (QTcF) in patients with relapsed/refractory acute myeloid leukemia (AML) treated in the phase 3 QuANTUM-R study (NCT02039726). Methods The analysis dataset included 226 patients with AML. Quizartinib dihydrochloride was administered as daily doses of 20, 30, and 60 mg. Nonlinear mixed-effects modeling was performed using observed quizartinib and AC886 concentrations and time-matched mean electrocardiogram measurements. Results Observed QTcF increased with quizartinib and AC886 concentrations; the relationship was best described by a nonlinear maximum effect (Emax) model. The predicted mean increase in QTcF at the maximum concentration of quizartinib and AC886 associated with 60 mg/day was 21.1 ms (90% CI, 18.3–23.6 ms). Age, body weight, sex, race, baseline QTcF, QT-prolonging drug use, hypomagnesemia, and hypocalcemia were not significant predictors of QTcF. Hypokalemia (serum potassium < 3.5 mmol/L) was a statistically significant covariate affecting baseline QTcF, but no differences in ∆QTcF (change in QTcF from baseline) were predicted between patients with versus without hypokalemia at the same quizartinib concentration. The use of concomitant QT-prolonging drugs did not increase QTcF further. Conclusion QTcF increase was dependent on quizartinib and AC886 concentrations, but patient factors, including sex and age, did not affect the concentration–QTcF relationship. Because concomitant strong cytochrome P450 3A (CYP3A) inhibitor use significantly increases quizartinib concentration, these results support the clinical recommendation of quizartinib dose reduction in patients concurrently receiving a strong CYP3A inhibitor. Clinical Trial Registration NCT02039726 (registered January 20, 2014).

A short exploration of selected sensitive CYP3A4 substrates (Probe Drug)

Background: CYP450 enzymes in the liver have a significant role in the metabolism of xenobiotics. Probe drug strategy is broadly used to evaluate the pharmacodynamic & pharmacokinetic Drug/ herb-drug interactions/ Fooddrug interactions. Probe drugs guarantee the exact pathway of drug metabolism in the liver by its targeted tractability property. The CYP3A4 isoenzyme metabolizes majority of the drugs (65%). Methods: The characters of targeted probe drugs were observed from admetSAR (version2) online database. Results: Midazolam is widely used as a probe drug because of its peculiar character. Midazolam, affirms the accurate and consistent prediction of pharmacokinetic mediated drug interactions even within nanogram concentrations either within sight of and without a potent CYP3A inhibitor. Remarkably midazolam is used as CYP3A4 substrate in the majority of in vivo studies. Conclusion: However, midazolam shows a good response in all clinical studies because of its lesser half-life and bioavailability when compared with other probe drugs.

In Vitro and In Vivo Assessment of Metabolic Drug Interaction Potential of Dutasteride with Ketoconazole

Dutasteride (DUT) is a selective, potent, competitive, and irreversible inhibitor of both type-1 and type-2 5α-reductase (5AR) commonly used in the treatment of benign prostatic hyperplasia and androgenetic alopecia. In the present study, we developed a simple and sensitive high-performance liquid chromatography with fluorescence detection (HPLC-FL) method for simultaneous determination of DUT and its major active metabolite, 6β-hydroxydutasteride (H-DUT). Next, the pharmacokinetic interactions of DUT with ketoconazole (KET), a potent CYP3A inhibitor, were comprehensively investigated. In vivo rat intravenous and oral studies revealed that the pharmacokinetics of DUT and H-DUT were significantly altered by the co-administration of KET. Furthermore, the in vitro microsomal metabolism, blood distribution, and protein-binding studies suggest that the altered pharmacokinetics of DUT could be attributed primarily to the inhibition of the DUT metabolism by KET. To the best of our knowledge, this is the first study to show the drug interaction potential of DUT with azole antifungal drugs including KET, together with a newly developed HPLC-FL method for the simultaneous quantification of DUT and H-DUT.

Exposure-Response of Quizartinib Efficacy in Patients with Relapsed/Refractory AML

Introduction: Quizartinib is a once-daily, oral, highly potent and selective FLT3 inhibitor that has shown clinical activity in patients with relapsed/refractory acute myeloid leukemia (AML) with FLT3 internal tandem duplications in the phase 3 QuANTUM-R trial (Cortes et al, Lancet Oncol 2019; NCT02039726). In this analysis, exposure-response relationships of select efficacy endpoints of quizartinib were evaluated. Methods: Analysis was conducted for the following 2 studies separately: phase 2 study APS2689-CL-2004 and phase 3 QuANTUM-R study. Phase 2 study APS2689-CL-2004 enrolled 76 patients who were randomized to receive quizartinib 30 or 60 mg once daily (26.5 and 53.0 mg free base, respectively). Dose escalation was allowed and no dose reduction for strong cytochrome P450 3A (CYP3A) inhibitors was made in this study. In QuANTUM-R, 245 patients were randomized to receive quizartinib. The quizartinib dosing regimen was 30 mg/day and then escalated to 60 mg/day after 2 weeks if QTcF was ≤ 450 ms. Patients receiving a concurrent strong CYP3A inhibitor initiated quizartinib at 20 mg/day, with an increase to 30 mg/day, because concomitant use of a strong CYP3A inhibitor approximately doubles quizartinib exposure. Efficacy endpoints included in the analysis were rate of composite complete remission (CRc; complete remission (CR) + complete remission with incomplete platelet recovery + complete remission with incomplete hematologic recovery), duration of CRc, and overall survival (OS). Exposure measures in individual patients, such as average daily area under the curve (AUC), maximum concentration, and trough concentration, were obtained from a population pharmacokinetic analysis of quizartinib plasma concentration data (Kang et al, EHA 2019) and then used for correlating with the efficacy endpoints. Logistic regression analysis was used for CRc rate, and time-to-event analysis was performed for the duration of CRc and OS. The effect of quizartinib exposure on the percentage of subjects achieving bone marrow (aspirate) blasts of < 5% in QuANTUM-R was also assessed. Results: Patients were divided into 4 quartile groups according to average daily quizartinib AUC for the investigation of exposure-response relationships for OS and the duration of CRc. The lowest exposure quartile group showed shorter OS than the higher 3 quartile groups. The overall median OS from the intent-to-treat (ITT) population was 6.2 months in the phase 3 study; the median OS in the lowest exposure quartile group (Q1) was 4.5 months, whereas the median OS in the highest exposure quartile group (Q4) was 9.6 months (Fig. 1). Analysis of OS for the phase 2b study APS2689-CL-2004 demonstrated a similar trend, in which the lower AUC quartile demonstrated decreased OS. The overall OS from the ITT population was 5.2 months in the phase 2 study, and the median OS in Q1 and Q4 was 4.6 and 6.9 months, respectively (Fig. 2). Consistent with analyses for OS, the duration of CRc showed a trend of shorter duration of response in the lower AUC quartiles in both studies. Additionally, the lower AUC quartile appeared to result in a smaller proportion of subjects who achieved blast reduction of < 5% (ie, 33.3% in Q1 vs 45.6% to 52.6% in Q2 to Q4). However, no apparent trend of exposure-response relationship was shown for CRc (P > .05 from logistic regression analysis). Conclusions: Exposure-response analysis suggests a consistent trend for reduced clinical benefit at lower quizartinib AUC quartiles across various efficacy endpoints (but not CRc) in both the phase 2 and phase 3 studies. Current analysis supports the recommended dosing regimen of 30-mg starting dose with escalation to 60 mg as the target clinical dose. Figure Disclosures Kang: Daiichi Sankyo: Employment. Passarell:Cognigen Corporation: Employment. Abutarif:Daiichi Sankyo: Employment, Equity Ownership. Mendell:Daiichi Sankyo, Inc.: Employment. Yin:Daiichi Sankyo: Employment.

Assessing Drug Interaction and Pharmacokinetics of Loxoprofen in Mice Treated with CYP3A Modulators

Loxoprofen (LOX) is a non-selective cyclooxygenase inhibitor that is widely used for the treatment of pain and inflammation caused by chronic and transitory conditions. Its alcoholic metabolites are formed by carbonyl reductase (CR) and they consist of trans-LOX, which is active, and cis-LOX, which is inactive. In addition, LOX can also be converted into an inactive hydroxylated metabolite (OH-LOXs) by cytochrome P450 (CYP). In a previous study, we reported that CYP3A4 is primarily responsible for the formation of OH-LOX in human liver microsomes. Although metabolism by CYP3A4 does not produce active metabolites, it can affect the conversion of LOX into trans-/cis-LOX, since CYP3A4 activity modulates the substrate LOX concentration. Although the pharmacokinetics (PK) and metabolism of LOX have been well defined, its CYP-related interactions have not been fully characterized. Therefore, we investigated the metabolism of LOX after pretreatment with dexamethasone (DEX) and ketoconazole (KTC), which induce and inhibit the activities of CYP3A, respectively. We monitored their effects on the PK parameters of LOX, cis-LOX, and trans-LOX in mice, and demonstrated that their PK parameters significantly changed in the presence of DEX or KTC pretreatment. Specifically, DEX significantly decreased the concentration of the LOX active metabolite formed by CR, which corresponded to an increased concentration of OH-LOX formed by CYP3A4. The opposite result occurred with KTC (a CYP3A inhibitor) pretreatment. Thus, we conclude that concomitant use of LOX with CYP3A modulators may lead to drug–drug interactions and result in minor to severe toxicity even though there is no direct change in the metabolic pathway that forms the LOX active metabolite.