- Human cytochrome P450 enzymes bind drugs and other substrates mainly through conformational-selection modes. [Journal Article]
- JBJ Biol Chem 2019 May 30
- Cytochrome P450 (P450) enzymes are major catalysts involved in the oxidations of most drugs, steroids, carcinogens, fat-soluble vitamins, and natural products. The binding of substrates to some of th…
Cytochrome P450 (P450) enzymes are major catalysts involved in the oxidations of most drugs, steroids, carcinogens, fat-soluble vitamins, and natural products. The binding of substrates to some of the 57 human P450s and other mammalian P450s is more complex than a two-state system and has been proposed to involve mechanisms such as multiple ligand occupancy, induced-fit, and conformational-selection. Here, we used kinetic analysis of binding with multiple concentrations of substrates and computational modeling of these data to discern possible binding modes of several human P450s. We observed that P450 2D6 binds its ligand rolapitant in a mechanism involving conformational-selection. P450 4A11 bound the substrate lauric acid via conformational-selection, as did P450 2C8 with palmitic acid. Binding of the steroid progesterone to P450 21A2 was also best described by a conformational-selection model. Hexyl isonicotinate binding to P450 2E1 could be described by either a conformational-selection or an induced-fit model. Simulation of the binding of the ligands midazolam, bromocriptine, testosterone, and ketoconazole to P450 3A4 was consistent with an induced-fit or a conformational-selection model, but the concentration dependence of binding rates for varying both P450 3A4 and midazolam concentrations revealed discordance in the parameters, indicative of conformational-selection. Binding of the P450s 2C8, 2D6, 3A4, 4A11, and 21A2 was best described by conformational-selection, and P450 2E1 appeared to fit either mode. These findings highlight the complexity of human P450-substrate interactions and that conformational-selection is a dominant feature of many of these interactions.
- Rolapitant Is a Reversible Inhibitor of CYP2D6. [Journal Article]
- DMDrug Metab Dispos 2019; 47(6):567-573
- Rolapitant [(Varubi), 5S,8S)-8-[[(1R)-1-[3,5 bis(trifluoromethyl phenyl]ethoxy]methyl]-8-phenyl-1,7-diazaspiro[4.5]decan-2-one] is a high-affinity NK1 receptor antagonist that was approved in Septemb…
Rolapitant [(Varubi), 5S,8S)-8-[[(1R)-1-[3,5 bis(trifluoromethyl phenyl]ethoxy]methyl]-8-phenyl-1,7-diazaspiro[4.5]decan-2-one] is a high-affinity NK1 receptor antagonist that was approved in September 2015 as a treatment for nausea and vomiting caused by chemotherapy. In vivo rolapitant moderately inhibits CYP2D6 for at least 7 days after one 180 mg dose. Due to the long inhibition time, we investigated rolapitant as a possible mechanism-based inactivator of CYP2D6. Rolapitant docked in the active site of CYP2D6 and displayed type I binding to CYP2D6 with a K s value of 1.2 ± 0.4 µM. However, in NADPH-, time-, and concentration-dependent assays of CYP2D6 activity, no evidence for mechanism-based inactivation and no metabolites of rolapitant were observed. Stopped-flow binding studies yielded a kon /koff (K d) value of 6.2 µM. The IC50 value for rolapitant inhibition of CYP2D6 activity was 24 µM, suggesting that inhibition is not due to tight binding of rolapitant to CYP2D6. By Lineweaver-Burk analysis, rolapitant behaved as a mixed, reversible inhibitor. The K i values of 20 and 34 µM were determined by Dixon analysis, with bufuralol and dextromethorphan as reporter substrates, respectively, and drug-drug interaction modeling did not predict the reported in vivo inhibition. The interaction of rolapitant with CYP2D6 was also examined in 1 microsecond molecular dynamics simulations. Rolapitant adopted multiple low-energy binding conformations near the active site, but at distances not consistent with metabolism. Given these findings, we do not see evidence that rolapitant is a mechanism-based inactivator. Moreover, the reversible inhibition of CYP2D6 by rolapitant may not fully account for the moderate inhibition described in vivo.
- IV aprepitant (Cinvanti) for chemotherapy-induced nausea and vomiting. [Journal Article]
- MLMed Lett Drugs Ther 2018 Dec 03; 60(1561):e200-e201
- An Open-Label, Randomized, Pivotal Bioequivalence Study of Oral Rolapitant. [Journal Article]
- CPClin Pharmacol Drug Dev 2019; 8(2):152-159
- Rolapitant, a selective and long-acting neurokinin-1 receptor antagonist, is approved in an oral formulation for prevention of delayed chemotherapy-induced nausea and vomiting in adults. This pivotal…
Rolapitant, a selective and long-acting neurokinin-1 receptor antagonist, is approved in an oral formulation for prevention of delayed chemotherapy-induced nausea and vomiting in adults. This pivotal open-label, randomized, single-dose, multicenter, parallel-group study assessed the bioequivalence of a single oral dose of 180 mg of rolapitant administered in tablet (2 × 90-mg tablets) or capsule (4 × 45-mg capsules) form in healthy male and female subjects. Blood samples for pharmacokinetic analysis were collected predose and at times up to 912 hours postdose. The rolapitant tablet was considered bioequivalent to the rolapitant capsule if the 90% confidence intervals for the ratios of the geometric means for rolapitant, observed maximum plasma concentration (Cmax), and area under the curve from time 0 extrapolated to infinity (AUC0-∞) were within the 0.80-1.25 range. The pharmacokinetic profiles of the capsule group (n = 43) and tablet group (n = 44) were similar. The geometric mean ratios of Cmax and AUC0-∞ were 0.99 (0.89-1.11) and 1.05 (0.92-1.19), respectively, establishing bioequivalence of the rolapitant tablet and capsule formulations. Both formulations were well tolerated, with a similar incidence of treatment-emergent adverse events in the 2 groups.
- Pharmacokinetic Interactions of Rolapitant With Cytochrome P450 3A Substrates in Healthy Subjects. [Journal Article]
- JCJ Clin Pharmacol 2019; 59(4):488-499
- Rolapitant (Varubi) is a neurokinin-1 receptor antagonist approved for the prevention of chemotherapy-induced nausea and vomiting. Rolapitant is primarily metabolized by the cytochrome P450 3A4 (CYP3…
Rolapitant (Varubi) is a neurokinin-1 receptor antagonist approved for the prevention of chemotherapy-induced nausea and vomiting. Rolapitant is primarily metabolized by the cytochrome P450 3A4 (CYP3A4) enzyme. Unlike other neurokinin-1 receptor antagonists, rolapitant is neither an inhibitor nor an inducer of CYP3A4 in vitro. The objective of this analysis was to examine the pharmacokinetics of rolapitant in healthy subjects and assess drug-drug interactions between rolapitant and midazolam (a CYP3A substrate), ketoconazole (a CYP3A inhibitor), or rifampin (a CYP3A4 inducer). Three phase 1, open-label, drug-drug interaction studies were conducted to examine the pharmacokinetic interactions of orally administered rolapitant with midazolam, rolapitant with ketoconazole, and rolapitant with rifampin. The pharmacokinetic profiles of midazolam and 1-hydroxy midazolam metabolites were essentially unchanged when coadministered with rolapitant, indicating the lack of a clinically relevant inhibition or induction of CYP3A by rolapitant. Coadministration of ketoconazole with rolapitant had no effects on rolapitant maximum concentration and resulted in an approximately 20% increase in the area under the concentration-time curve of rolapitant, suggesting that strong CYP3A inhibitors have minimal inhibitory effects on rolapitant exposure. Repeated administrations of rifampin appeared to reduce rolapitant exposure, resulting in a 33% decrease in maximum concentration and 87% decrease in area under the concentration-time curve from time zero to infinity. Coadministration of rolapitant did not affect the exposure of midazolam. Rifampin coadministration resulted in lower concentrations of rolapitant, and ketoconazole coadministration had no or minimal effects on rolapitant exposure. Rolapitant was safe and well tolerated when coadministered with ketoconazole, rifampin, or midazolam. No new safety signals were reported compared with previous studies of rolapitant.
- Errata. [Journal Article]
- IJInt J Pharm Compd 2018 Nov-Dec; 22(6):527
- Ketamine 50-mg/mL Injection, IJPC Jul/Aug 2013 pg 331. "Evaluation of the Stability of Ketoprofen in Pluronic Lecithin Organogel and the Determination of an Appropriate Beyond-use Date" IJPC Jul/Aug …
Ketamine 50-mg/mL Injection, IJPC Jul/Aug 2013 pg 331. "Evaluation of the Stability of Ketoprofen in Pluronic Lecithin Organogel and the Determination of an Appropriate Beyond-use Date" IJPC Jul/Aug 2014 pg 348-350. "Rolapitant Injectable Emulsion with Palonosetron Hydrochloride Admixture" IJPC May/Jun 2018 pg 237.
- Infusion reactions following administration of intravenous rolapitant at an academic medical center. [Journal Article]
- JOJ Oncol Pharm Pract 2018 Oct 22; :1078155218808084
- In 2017, due to a fluid shortage secondary to Hurricane Maria's devastation of Puerto Rico, hospitals and health-systems began to substitute rolapitant for fosaprepitant as part of chemotherapy-induc…
In 2017, due to a fluid shortage secondary to Hurricane Maria's devastation of Puerto Rico, hospitals and health-systems began to substitute rolapitant for fosaprepitant as part of chemotherapy-induced nausea and vomiting prevention and treatment strategies. However, despite advantageous pharmacologic and formulation (e.g. long half-life, quicker time to onset, and lack of first-pass hepatic metabolism) profiles, there seems to be significant risk of infusion-related hypersensitivity reactions associated with the administration of intravenous rolapitant. In January 2018, the U.S. FDA issued a Health Care Provider Letter stating that anaphylaxis, anaphylactic shock, and other serious hypersensitivity reactions have been reported in the postmarketing setting. Importantly, these reactions were observed at a higher rate than initially reported in the phase 1 bioequivalence study that led to FDA approval of intravenous rolapitant (2.8%), with many resulting in hospitalizations. At our institution, rolapitant-induced infusion-related reactions also occurred in more patients than expected (8.7%). Described herein are six cases of infusion-related hypersensitivity reactions with intravenous rolapitant at the North Carolina Cancer Hospital. Due to the quick onset of the infusion-related hypersensitivity reactions with intravenous rolapitant, interpatient differences in pharmacokinetics or pharmacodynamics are unlikely to be the cause. An objective assessment utilizing the Naranjo Causality Scale rates these infusion-related hypersensitivity reactions as definite adverse drug reactions.
- Development of an Efficient and Cost-Effective Enzymatic Process for Production of (R)-[3,5-bis(trifluoromethyl)phenyl] Ethanol Using Carbonyl Reductase Derived from Leifsonia sp. S749. [Journal Article]
- ABAppl Biochem Biotechnol 2019; 188(1):87-100
- (R)-[3,5-bis(trifluoromethyl) phenyl] ethanol [(R)-3,5-BTPE] is a crucial chiral intermediate for the synthesis of the NK-1 receptor antagonists aprepitant, rolapitant and fosaprepitant. The carbonyl…
(R)-[3,5-bis(trifluoromethyl) phenyl] ethanol [(R)-3,5-BTPE] is a crucial chiral intermediate for the synthesis of the NK-1 receptor antagonists aprepitant, rolapitant and fosaprepitant. The carbonyl reductase KR01 from Leifsonia sp. S749, discovered by protein sequence alignment, could convert 3',5'-bis(trifluoromethyl) acetophenone (3,5-BTAP) into (R)-3,5-BTPE with excellent activity and enantioselectivity. In order to enhance the conversion efficiency at high substrate concentrations, the reaction conditions were optimized by response surface analysis. The results showed that 600 g/L 3,5-BTAP was bioreduced to (R)-3,5-BTPE (> 99.9% enantiomeric excess) by the recombinant Escherichia coli/pET-28a (+)-KR01 whole cells, with a 98.3% conversion and 59 g/L/h productivity under the optimized reaction conditions. In addition, the recombinant E. coli cells could be repeatedly used up to seven times in the reaction mixture containing 90% isopropanol (IPA). This is the highest substrate loading and productivity for the bioreduction of 3,5-BTAP by carbonyl reductase ever reported, and this method represents an efficient and cost-effective process for production of (R)-3,5-BTPE.
- Evolving role of neurokinin 1-receptor antagonists for chemotherapy-induced nausea and vomiting. [Review]
- OTOnco Targets Ther 2018; 11:6459-6478
- To examine pharmacologic and clinical characteristics of neurokinin 1 (NK1)-receptor antagonists (RAs) for preventing chemotherapy-induced nausea and vomiting (CINV) following highly or moderately em…
To examine pharmacologic and clinical characteristics of neurokinin 1 (NK1)-receptor antagonists (RAs) for preventing chemotherapy-induced nausea and vomiting (CINV) following highly or moderately emetogenic chemotherapy, a literature search was performed for clinical studies in patients at risk of CINV with any approved NK1 RAs in the title or abstract: aprepitant (capsules or oral suspension), HTX019 (intravenous [IV] aprepitant), fosaprepitant (IV aprepitant prodrug), rolapitant (tablets or IV), and fixed-dose tablets combining netupitant or fosnetupi-tant (IV netupitant prodrug) with the 5-hydroxytryptamine type 3 (5HT3) RA palonosetron (oral or IV). All NK1 RAs are effective, but exhibit important differences in efficacy against acute and delayed CINV. The magnitude of benefit of NK1-RA-containing three-drug vs two-drug regimens is greater for delayed vs acute CINV. Oral rolapitant has the longest half-life of available NK1 RAs, but as a consequence should not be administered more frequently than every 2 weeks. In general, NK1 RAs are well tolerated; however, IV rolapitant was recently removed from US distribution, due to hypersensitivity and anaphylaxis, and IV fosaprepitant is associated with infusion-site reactions and hypersensitivity presumed related to its polysorbate 80 excipient. Also, available NK1 RAs have potential drug-drug interactions. Adding an NK1 RA to 5HT3 RA and dexamethasone significantly improves CINV control vs the two-drug regimen. Newer NK1 RAs offer more formulation options, higher acute-phase plasma levels, or improved tolerability, and increase clinicians' opportunities to maximize benefits of this important class of antiemetics.
New Search Next
- A Phase 1 Assessment of the QT Interval in Healthy Adults Following Exposure to Rolapitant, a Cancer Supportive Care Antiemetic. [Journal Article]
- CPClin Pharmacol Drug Dev 2018 Sep 26
- This 2-part study evaluated the QT/QTc prolongation potential and safety and pharmacokinetics of the antiemetic rolapitant, a neurokinin-1 receptor antagonist. Part 1 was a randomized, placebo-contro…
This 2-part study evaluated the QT/QTc prolongation potential and safety and pharmacokinetics of the antiemetic rolapitant, a neurokinin-1 receptor antagonist. Part 1 was a randomized, placebo-controlled single-dose-escalation study assessing the safety of a single high dose of rolapitant. Part 2 was a randomized, placebo- and positive-controlled, double-blind parallel-group study including 4 treatment arms: rolapitant at the highest safe dose established in part 1, placebo, moxifloxacin 400 mg (positive control), and rolapitant at the presumed therapeutic dose (180 mg). Among 184 adults, rolapitant was absorbed following oral administration under fasting conditions, with a median Tmax of 4 to 6 hours (range, 2-8 hours) and was safe at all doses up to 720 mg. No differences in mean change in QTcF were observed between placebo and rolapitant from baseline or at any point. At any point, the upper bound of the confidence interval for the mean difference between placebo and rolapitant was no greater than 4.4 milliseconds, and the mean difference between placebo and rolapitant was no greater than 1.7 milliseconds, suggesting an insignificant change in QTc with rolapitant. Rolapitant is safe and does not prolong the QT interval at doses up to 720 mg relative to placebo in healthy adults.