Bufalin inhibits CYP3A4 activity in vitro and in vivo

Aim： To investigate the inhibitory interactions of bufalin and CYP3A4. Methods： Recombinant human CYP3A4 was incubated with bufalin in vitro. Bufalin was administered ig and iv to Wistar rats to further estimate its impact on CYP3A4, and midazolam was given to index the activity of CYP3A4. Results： The IC50 of bufalin was 14.52 μmol/L. Bufalin affected CYP3A4 activity with increases in AUC0-t and t1/2, and decreases in CL and the formation of 1-hydroxy-midazolam after ig or iv administration of midazolam （P〈0.05）. An increase in Cmax after ig bufalin administration （P〈0.05） was observed. Conclusion： Bufalin showed a modest but significant inhibition of CYP3A4 both in vitro and in vivo. The likelihood of an interaction between bufalin and the CYP3A4-metabolized drugs in human might not be negated.     

Quantitative prediction of hepatic CYP3A activity using endogenous markers in healthy subjects after administration of CYP3A inhibitors or inducers

Accurate prediction of cytochrome P450 (CYP) 3A activity in the early stage of drug development and in clinical practice is important. This study aimed to evaluate the previously constructed CYP3A activity prediction model after administration of CYP3A inhibitors and inducers and to modify the model for better prediction of CYP3A activity. Healthy male subjects received the following study drugs during three study periods: midazolam alone (control phase); midazolam with 200 mg of itraconazole (CYP3A inhibition phase); and midazolam with 150 mg of rifampicin (CYP3A induction phase). We quantified the concentrations of several endogenous CYP3A markers in both urine and plasma using gas chromatography-mass spectrometry. The urinary markers, including 6β-hydroxy (OH)-cortisol/cortisol, 6β-OH-cortisone/cortisone, 16α-OH-dehydroepiandrosterone (DHEA)/DHEA, 16α-OH-androstenedione (A-dione)/A-dione and 7β-OH-DHEA/DHEA, were significantly correlated with midazolam clearance in both the CYP3A inhibition and induction phases. We constructed a statistical prediction model after integrating data from a previous study to predict midazolam clearance as follows: Ln(midazolam clearance) = 2.5545 + 0.3988 × ln(7β-OH-DHEA/DHEA) + 0.1984 × ln(16α-OH-DHEA/DHEA) + 0.5031 × ln(6β-OH-cortisol/cortisol) – 0.1261 [ln(7β-OH-DHEA/DHEA) × ln(6β-OH-cortisol/cortisol)] (r² = 0.75). We suggest that quantitating endogenous markers in vivo coupled with the statistical prediction model may be useful for predicting CYP3A parameters.     

The utility of CYP3A activity endogenous markers for evaluating drug-drug interaction between sildenafil and CYP3A inhibitors in healthy subjects

Cytochrome P450 (CYP) 3A-related drug-drug interaction (DDI) studies are needed during drug development to determine clinical interaction effects. We aimed to evaluate DDI between sildenafil and two CYP3A inhibitors, clarithromycin and itraconazole, regarding the changes in pharmacokinetics and endogenous markers. An open-label, one-sequence, one-period, two-treatment parallel study was conducted in 32 healthy Korean subjects. Each of 16 subjects were randomly assigned to the clarithromycin and itraconazole groups. Both groups received a single dose of sildenafil 25 mg as a control, and either clarithromycin 250 mg or itraconazole 100 mg was administered four times to inhibit CYP3A activity. Pharmacokinetics of sildenafil showed the similar magnitude of inhibitory effects of the two inhibitors on total CYP3A activity; both inhibitors similarly increased systemic exposure of sildenafil by 2-fold. Urinary 6β–OH–cortisone/cortisone and plasma 4β–OH–cholesterol were significantly decreased after clarithromycin administration but not after itraconazole. A significant correlation between sildenafil CL/F and metabolic markers of CYP3A activity was observed after clarithromycin administration. We confirmed that sildenafil has moderate pharmacokinetic interaction with clarithromycin and itraconazole. Endogenous markers well reflected the CYP3A inhibition of clarithromycin, suggesting possible utility in DDI study with moderate to strong CYP3A inhibition; however, there are limitations in predicting intestinal CYP3A mediated DDI.     

Pharmacokinetic interactions among major bioactive components in Radix Scutellariae via metabolic competition

Baicalein (B), wogonin (W) and oroxylin A (OA) are major components in Radix Scutellariae with similar pharmacokinetic properties. Due to the co‐presence of these three flavones in herbal formulations for Radix Scutellariae, they are likely consumed together. The aim of this study is to investigate whether the pharmacokinetics of individual flavones is influenced by each other and the underlying mechanism of the interaction. Various systems were utilized in the current study including a rat in vivo study, a Caco‐2 cell monolayer model and a rat in situ single‐pass intestinal perfusion as well as in vitro enzymatic kinetics studies. The B, W and OA given singly as well as in a mixture were administered and the corresponding pharmacokinetic parameters were calculated and compared. After co‐administration of the three flavones to rats, OA absorption increased significantly in comparison with when OA was administered alone. Mechanistic studies on the Caco‐2 cell monolayer and rat in situ single‐pass intestinal perfusion models revealed that co‐administration of B, W and OA could significantly enhance their absorption and decrease the extent of phase II metabolism. Further in vitro enzymatic study and a transport study in transfected MDCK cells revealed that metabolic competition rather than membrane transporters might contribute to the pharmacokinetic interactions. The co‐presence of multiple active components would result in metabolic interactions, which may induce further changes in pharmacodynamics. Copyright © 2012 John Wiley & Sons, Ltd.     

CYP2C8 but not CYP3A4 is important in the pharmacokinetics of montelukast

AIM

According to product information, montelukast is extensively metabolized by CYP3A4 and CYP2C9. However, CYP2C8 was also recently found to be involved. Our aim was to study the effects of selective CYP2C8 and CYP3A4 inhibitors on the pharmacokinetics of montelukast.

METHODS

In a randomized crossover study, 11 healthy subjects ingested gemfibrozil 600 mg, itraconazole 100 mg (first dose 200 mg) or both, or placebo twice daily for 5 days, and on day 3, 10 mg montelukast. Plasma concentrations of montelukast, gemfibrozil, itraconazole and their metabolites were measured up to 72 h.

RESULTS

The CYP2C8 inhibitor gemfibrozil increased the AUC(0,∞) of montelukast 4.3-fold and its t_1/2 2.1-fold (P < 0.001). Gemfibrozil impaired the formation of the montelukast primary metabolite M6, reduced the AUC and C_max of the secondary (major) metabolite M4 by more than 90% (P < 0.05) and increased those of M5a and M5b (P < 0.05). The CYP3A4 inhibitor itraconazole had no significant effect on the pharmacokinetic variables of montelukast or its M6 and M4 metabolites, but markedly reduced the AUC and C_max of M5a and M5b (P < 0.05). The effects of the gemfibrozil-itraconazole combination on the pharmacokinetics of montelukast did not differ from those of gemfibrozil alone.

CONCLUSIONS

CYP2C8 is the dominant enzyme in the biotransformation of montelukast in humans, accounting for about 80% of its metabolism. CYP3A4 only mediates the formation of the minor metabolite M5a/b, and is not important in the elimination of montelukast. Montelukast may serve as a safe and useful CYP2C8 probe drug.     

Impact of nonlinear midazolam pharmacokinetics on the magnitude of the midazolam-ketoconazole interaction in rats

1. Numerous groups have described the rat as an in vivo model for the assessment and prediction of drug–drug interactions (DDIs) in humans involving the inhibition of cytochrome P450 3A forms. Even for a well-established substrate-inhibitor pair like midazolam-ketoconazole, however, the magnitude of the DDI in rats (e.g. 1.5- to 5-fold) does not relate to what is observed clinically (e.g. 5- to 16-fold).

2. Because nonlinear substrate pharmacokinetics (PK) may result in a weaker interaction, it was hypothesized that the lower magnitude of interaction observed in rats was due to the saturation of metabolic pathway(s) of midazolam at the doses used (10–20 mg/kg). Therefore, the inhibitory effects of ketoconazole were reevaluated at lower oral (1 and 5 mg/kg) and intravenous (IV) (1 mg/kg) doses of midazolam.

3. In support of the hypothesis, oral exposure at 5 mg/kg dose of midazolam was 18-fold higher compared to that at 1 mg/kg. Furthermore, when the interaction was investigated at the lower midazolam dose (1 mg/kg), ketoconazole increased the IV and oral exposure of midazolam by 7-fold and 11-fold, respectively. A weaker DDI (1.5- to 1.8-fold) was observed at the higher oral midazolam dose.

4. Collectively, these results suggest that the lower reported interaction in rats is likely due to saturation of midazolam clearance at the doses used. Therefore, when the rat is used as a DDI model to screen and differentiate compounds, or predict CYP3A inhibition in humans, it is important to use low doses of midazolam and ensure linear PK.

     

The effect of CYP3A inhibitors and inducers on the pharmacokinetics of telaprevir in healthy volunteers

AIM

To evaluate the effects of ketoconazole, rifampicin and efavirenz on the pharmacokinetics of telaprevir in healthy volunteers.

METHOD

Results from three clinical studies are described. (1) Volunteers received a single 750 mg dose telaprevir with and without a single 400 mg dose ketoconazole. (2) Volunteers received (a) 1250 mg telaprevir followed by three 750 mg doses given every 8 h and (b) four 1250 mg telaprevir doses given every 8 h, with a single 400 mg dose ketoconazole given with the fourth dose of telaprevir. (3) Volunteers received either a single 750 mg dose telaprevir with or without 600 mg once daily rifampicin, or 750 mg every 8 h telaprevir with and without 600 mg once daily efavirenz.

RESULTS

A single 400 mg dose of ketoconazole increased single dose telaprevir exposure: the geometric least-squares mean ratio (GLSMR, with 90% confidence limits) was 1.24 (1.10, 1.41) for C_max and 1.62 (1.45, 1.81) for AUC(0,∞). However, after multiple doses of telaprevir, there was no discernible effect of ketoconazole on telaprevir exposure. Co-administration of rifampicin at steady-state markedly reduced single dose telaprevir exposure with GLSMRs of 0.14 (0.11, 0.18) for C_max and 0.08 (0.07, 0.11) for AUC(0,∞), whereas efavirenz had a smaller effect on telaprevir exposure when both drugs were co-administered at steady-state, with GLSMRs of 0.91 (0.81, 1.02) for C_max, 0.53 (0.44, 0.65) for C_min, and 0.74 (0.65, 0.84) for AUC(0,8 h).

CONCLUSION

CYP3A inducers, rifampicin and efavirenz, can reduce telaprevir exposure to varying degrees based on their potency. The effect of ketoconazole as an inhibitor of telaprevir metabolism is more pronounced after a single dose of telaprevir than after repeated administration.     

Study on the interactions of pharmacokinetics and liver distributions between rosuvastatin and repaglinide in rats

In the present study,we aimed to investigate the interactions of pharmacokinetics and liver distributions between rosuvastatin and repaglinide in rats.Coadministration of repaglinide (0.5 mg/kg, 1 mg/kg and 2 mg/kg) for 7 d significantly increased the AUC_0–24 and C_max of rosuvastatin (P<0.01), but dramatically decreased the CL/F of rosuvastatin (P<0.01) after a single dose of rosuvastatin (10 mg/kg). There were no obviously changes in the parameters of T_max and t_1/2. Coadministration of repaglinide also decreased the liver distribution of rosuvastatin (P<0.01). Coadministration of rosuvastatin (20 mg/kg) for 7 days significantly increased the AUC_0–12 and C_max of repaglinide (P<0.05), and decreased the CL/F of repaglinide (P<0.01) after a single dose of repaglinide (1 mg/kg). The liver distribution of repaglinide was also decreased (P<0.01). Our animal study indicated that repaglinide could significantly affect the pharmacokinetics and liver distribution of rosuvastatin in rats and vice versa.     

人肝CYP3A参与了山冈橐吾碱的代谢及其肝毒性代谢物的形成(英文)

目的　在体外研究山冈橐吾碱在人肝微粒体内的代谢及参与其代谢的主要的CYP4 5 0酶 ,探讨其代谢致毒机理。方法　采用人肝微粒体研究山冈橐吾碱的主要代谢方式和代谢物。在体外运用CYP4 5 0酶的选择性抑制剂和cDNA表达的人肝CYP4 5 0酶 ,探讨其对山冈橐吾碱的代谢及肝毒性的吡咯代谢物形成的影响及参与山冈橐吾碱代谢的主要的CYP4 5 0酶。结果　山冈橐吾碱在人肝微粒体内的主要代谢物为肝毒性的吡咯代谢物 :去氢倒千里光裂碱 ,7 谷胱甘肽基 去氢倒千里光裂碱 ,7,9 二谷胱甘肽基去氢倒千里光裂碱和山冈囊吾酸。CYP4 5 0特异性抑制剂α 萘黄酮 (抑制CYP1A2 )、黄胺苯吡唑 (抑制CYP2C)、奎尼丁 (抑制CYP2D6 )和二乙基二硫代氨基甲酸钠 (抑制CYP2E1)对山冈橐吾碱的代谢无明显的影响。但CYP3A的特异性抑制剂酮康唑和三乙酰竹桃霉素可以显著地抑制山冈橐吾碱的代谢及其吡咯代谢物和结合型吡咯物的形成。此外 ,在cDNA表达的人肝CYP3A4的温孵液中 ,山冈橐吾碱被代谢成相应的吡咯代谢物 ,而山冈橐吾碱在cDNA表达的人肝CYP1A2、CYP2C9、CYP2D6和CYP2E1温孵液中无代谢。结论　山冈橐吾碱在人肝微粒体内的主要代谢方式是形成肝毒性吡咯代谢物 ,CYP3A作为主要的CYP4 5 0酶参与了山冈橐吾碱的代谢及其肝毒性吡咯代谢?     

Multivalent cation and polycation polymer preparations influence pharmacokinetics of dolutegravir via chelation-type drug interactions

Dolutegravir (DTG) is an integrase inhibitor, whose gastrointestinal absorption is impaired by the formation of chelates with multivalent metal cation preparations. However, little is known regarding the interactions of DTG with preparations containing other multivalent metal cations or with polycation polymer preparations. This study examined how the pharmacokinetics of DTG are affected by co-administration with Al(OH)₃, LaCO₃, and the polycation polymers bixalomer (Bxl) and sevelamer (Svl). Prior to oral administration of DTG (5 mg/kg), rats were orally administered Al(OH)₃ (150 or 300 mg/kg), LaCO₃ (50 or 75 mg/kg), Bxl (250 or 500 mg/kg), or Svl (300 or 600 mg/kg). Serum concentrations of DTG were then measured over the next 24 h. Compared to the administration of DTG alone, its co-administration with Al(OH)₃, LaCO₃, Bxl, and Svl led to reduced serum concentration of DTG, and consequently, a significantly reduced area under the curve. These comparisons also revealed a considerable reduction in the maximum concentration, suggesting that the interactions of these agents with DTG in the intestinal tract inhibit absorption of DTG. The above results demonstrate that Al(OH)₃, LaCO₃, Bxl, and Svl affect the pharmacokinetics of DTG and indicate the need for caution when combining any of the above preparations with DTG.     

CYP3A4和P糖蛋白与药物的肠道处置

肠CYP3A4介导的生物转化和P糖蛋白介导的药物主动泵出肠细胞是决定口服药物生物利用度的主要因素。有证据显示CYP3A4和P糖蛋白在小肠不是共同调节的,但两者在药物肠道处置中的协同作用已得到体外试验和动物体内试验的证实。进一步了解两者的相互作用有助于改善CYP3A4/P糖蛋白底物的生物利用度。     

Influence of andrographolide on the pharmacokinetics of warfarin in rats

Context: Andrographolide and warfarin are often used together in clinics in China. However, the herb-drug interaction between andrographolide and warfarin is still unknown.

Objective: This study investigates the herb-drug interaction between andrographolide and warfarin in vivo and in vitro.

Materials and methods: A sensitive and reliable LC-MS/MS method was developed for the determination of warfarin in male Sprague-Dawley rats plasma, and then the pharmacokinetics of orally administered warfarin (0.5?mg/kg) with or without andrographolide (30?mg/kg/day for 7?days) pretreatment was investigated. In addition, Sprague-Dawley rat liver microsomes incubation systems were used to support the in vivo pharmacokinetic data and investigate its potential mechanism.

Results: The method validation results showed that a sensitive and reliable LC-MS/MS method was developed for the determination of warfarin in rat plasma samples. The pharmacokinetic results indicated that co-administration of andrographolide could increase the systemic exposure of warfarin significantly, including area under the curve (118.92?±?18.08 vs. 60.58?±?9.46?μg?×?h/mL), maximum plasma concentration (3.32?±?0.41 vs. 2.35?±?0.25?μg/mL) and t_1/2 (22.73?±?3.28 vs. 14.27?±?2.67?h). Additionally, the metabolic stability of warfarin increased from 23.5?±?4.7 to 38.7?±?6.1?min with the pretreatment of andrographolide, and the difference was significant (p?Discussion and conclusion: In conclusion, andrographolide could increase the systemic exposure of warfarin in rats when andrographolide and warfarin were co-administered, and possibly by slowing down the metabolism of warfarin in rat liver by inhibiting the activity of CYP3A4 or CYP2C9.     

Effect of polymorphic CYP3A5 genotype on the single-dose simvastatin pharmacokinetics in healthy subjects

Simvastatin, a cholesterol-lowering agent, is mainly metabolized by CYP3A4/5. The objective of this study was to investigate the effect of CYP3A5*3 genotype on the pharmacokinetics of simvastatin in humans. Twenty-two men with CYP3A5*1/*1 (n = 4), CYP3A5*1/*3 (n = 8), or CYP3A5*3/*3 (n = 10) genotypes were enrolled. Each subject ingested a 20-mg dose of simvastatin, and plasma simvastatin concentrations were measured for 12 hours after dosing. The mean (+/-SD) area under the plasma concentration-time curve for simvastatin in the CYP3A5*1/*1 carriers (4.94 +/- 2.25 ng x h/mL) was significantly lower than CYP3A5*3/*3 carriers (16.35 +/- 6.37 ng x h/mL; P = .013, Bonferroni test). The mean (+/-SD) oral clearance was also significantly different between CYP3A5*1/*1 carriers (4.80 +/- 2.35 L/h) and CYP3A5*3/*3 carriers (1.35 +/- 0.61 L/h; P < .05, Dunn's test). However, other pharmacokinetic parameters including peak plasma concentrations and half-life did not show any difference between genotype groups. These findings suggest that the polymorphic CYP3A5 gene affects the disposition of simvastatin and provides a plausible explanation for interindividual variability of simvastatin disposition.     

Effect of danshen extract on the activity of CYP3A4 in healthy volunteers

AIMS

To assess the effect of danshen extract on CYP3A4 activity using midazolam as an in vivo probe.

METHODS

A sequential, open-label, two-period pharmacokinetic interaction study design was used to compare midazolam pharmacokinetic parameters before and after 14 days of administration of danshen tablets. Twelve healthy volunteers received a single oral dose (15 mg) of midazolam followed by danshen tablets (four tablets orally, three times a day) for 14 days. On the last day of the study they received four danshen tablets with a 15 mg midazolam tablet and plasma concentrations of midazolam and its corresponding metabolite 1–hydroxylmidazolam were measured prior to and after the administration of danshen tablets periodically for 12 h.

RESULTS

The 90% confidence intervals of C_max,t_1/2, CL/F and AUC(0,∞) of midazolam before and after administration of danshen tablets were (0.559, 0.849), (0.908, 1.142), (1.086, 1.688) and (0.592, 0.921), respectively; and those of C_max, t_1/2 and AUC(0,∞) of 1-hydroxylmidazolam after vs. before administration of danshen tablets were (0.633, 0.923), (0.801, 1.210) and (0.573, 0.980), respectively. Ratios of geometric LS means of C_max(1OHMid) : C_max(Mid) and AUC_max(1OHMid) : AUC_max(Mid) (after vs. before 14-day danshen) were 1.072 and 1.035, respectively.

CONCLUSIONS

Our findings suggest that multiple dose administration of danshen tablets may induce CYP3A4 in the gut. Accordingly, caution should be taken when danshen products are used in combination with therapeutic drugs metabolized by CYP3A.     

Versatile applicability of a grid-based CYP3A4 Template to understand the interacting mechanisms with the small-size ligands; part 3 of CYP3A4 Template study

Modes of interactions of small ligands with CYP3A4 have been defined using the Template established in our previous studies (DMPK. 34: 113–125 2019 and 34 351–364 2019). Interactions of polyaromatic hydrocarbons such as benzo[a]pyrene, pyrene and dibenzo[a,j]acridine were refined with the idea of Right-side movement of ligands at Rings A and B of Template. Expected formation of metabolites from the placements faithfully matched with experimentally observed sites of their metabolisms and also with preferred orders of regio-isomeric metabolite abundances in recombinant CYP3A4 system. In comparison of CYP3A4-ligand data with the placements on simulations, a futile sitting of non-substituted and free rotatable phenyl structures was suggested as a cause of poor oxidations of the phenyl parts of CYP3A4 ligands. These data were in turn indicative of the role of the rotation-ceasing action for the function. Typical inhibitors, ketoconazole, nicardipine, mibefradil and GF-I-1 shared mutuality on their sittings, in which the inhibitor molecules hold a CYP3A4 residue from dual sides on Template. In addition, clotrimazole would be stuck between facial- and rear-side walls of CYP3A4 and interact with ferric iron through nitrogen atom of the imidazole part. These data offered structural bases of CYP3A4-inhibitory actions of ligands.     

Development of template systems for ligand interactions of CYP3A5 and CYP3A7 and their distinctions from CYP3A4 template

Starting from established CYP3A4 Template (DMPK. 2019, and 2020), CYP3A5 and CYP3A7 Templates have been constructed to be reliable tools for verification of their distinct catalytic properties. A distinct occupancy was observed on CYP3A4-selective ligands, but not on the non-selective ligands, in simulation experiments. These ligands often invade into Bay-1 region during the migration from Entrance to Site of oxidation in simulation experiments. These results offered an idea of the distinct localization of Bay-1 residue on CYP3A5 Template, in which the Bay-1 residue stayed closely to Template border. The idea also accounted for the higher oxidation rates of CYP3A5, than of CYP3A4, of noscapine and schisantherin E through their enhanced sitting-stabilization. Typical CYP3A7 substrates such as zonisamide and retinoic acids took their placements without occupying a left side region of Template for their metabolisms. In turn, the occupancies of the left-side region were inevitably observed among poor ligands of CYP3A7. Altered extent of IJK-Interaction or localization of a specific residue at the left-side would thus explain distinct catalytic properties of CYP3A7 on Template. These data suggest the alteration of each one of Template region, from CYP3A4 Template, led to the distinct catalytic properties of CYP3A5 and CYP3A7 forms.     

CYP3A4 and MDR Mediated Interactions in Drug Therapy

Multiple drug therapy is recommended in many disease states including AIDS, cancer, diabetes, and stroke. Therefore, drug-drug interactions can result in changes in pharmacological or toxicological response following concomitant administration of many therapeutic agents. It has become evident that two factors i.e. drug efflux pump- P-glycoprotein (MDR gene product) and metabolizing enzyme- CYP3A4 play major roles in this process. These two key proteins regulate all pharmacokinetic and pharmacodynamic interactions through the process of drug absorption, metabolism, disposition and elimination. Co-administration of two or more drugs can affect these processes due to altered functions of P-glycoprotein (P-gp) and CYP3A4 and consequently change clinical response and final outcome. After co-administration, some drugs may induce the activity of P-gp and/or CYP3A4 resulting in subtherapeutic blood levels and therapeutic failure due to reduced absorption and/or increased metabolism. Conversely, inhibition(s) of P-gp and/or CYP3A4 can cause enhanced plasma concentration and therefore, drug toxicity. Overlapping substrate specificities to these proteins make it difficult to understand perplexing pharmacokinetic interactions with multidrug regimens. Inter-patient variability of drug response can occur due to change in genetic profiles, intake of food, herbal supplement, and recreational drugs. In this review, we have outlined several clinically important CYP and MDR-mediated drug-drug interactions of antiretroviral agents, antineoplastic agents, azole antifungals, statins, methadone, antibacterials, cardiovascular medicines, immune modulators, recreational drugs and herbal agents. Mechanisms by which such drug interactions occur have been briefly discussed in some of the examples.     

Lack of effect of tofacitinib (CP-690,550) on the pharmacokinetics of the CYP3A4 substrate midazolam in healthy volunteers: confirmation of in vitro data

AIMS

To investigate inhibitive and inductive effects of tofacitinib (CP-690,550), a Janus kinase inhibitor, on CYP3A4 function via in vitro and in vivo studies.

METHODS

In vitro experiments were conducted to assess the inhibition and induction potential of tofacitinib for major drug metabolizing enzymes (CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6 and CYP3A4). A phase 1, randomized, open-label, two-way crossover study ({"type":"clinical-trial","attrs":{"text":"NCT00902460","term_id":"NCT00902460"}}NCT00902460) was conducted to confirm the lack of inhibitive/inductive effect on a sensitive CYP3A4 substrate, midazolam, in healthy subjects. Midazolam pharmacokinetics were assessed over 24 h following single dose 2 mg administration prior to administering tofacitinib and after twice daily dosing of tofacitinib 30 mg for 6 days. The primary endpoint was midazolam area under the concentration–time profile, from time 0 to infinity (AUC(0,∞)).

RESULTS

In vitro studies demonstrated low potential for CYP inhibition (IC₅₀ estimates tofacitinib >30 µm), CYP3A4 mRNA induction (observed at tofacitinib concentrations ≥25 µm) and no effect on enzymatic activity of CYP substrates. In the human study, AUC(0,∞) adjusted geometric mean ratio for midazolam plus tofacitinib to midazolam alone was 103.97% [90% confidence interval (CI) 95.57, 113.12], wholly within the pre-specified acceptance region (80, 125). The 90% CI for the ratio of adjusted geometric means of maximum plasma concentration (C_max) (95.98, 108.87) was also wholly within this acceptance region.

CONCLUSIONS

These data confirm a lack of an inhibitive or inductive effect of tofacitinib on CYP3A activity in humans and, in conjunction with in vitro data, support the conclusion that tofacitinib is unlikely to influence the CYP enzyme system as a whole.