Tamoxifen Inhibits Cytochrome P450 2C9 Activity in Breast Cancer Patients

Discovery of pharmacological agents for triple-negative breast cancer (TNBC): molecular docking and molecular dynamic simulation studies on 5-lipoxygenase (5-LOX) and nuclear factor kappa B (NF-κB)

Global burden of breast cancer is expected to cross 26 million new cases by 2030. The term 'triple negative breast cancer' (TNBC) refers to lack of expression of hormone receptors (ER, PR and HER2). 5-Lipoxygenase (5-LOX) inhibition promotes breast cancer apoptosis, ferroptosis and inhibits metastases. Nuclear factor kappa B (NF-κB) activation induces cell survival in breast cancer through stimulation of angiogenesis. Therefore, inhibiting NF-B signalling can stop the growth of tumours. In light of these facts, an attempt is made to investigate binding characteristics of LOX inhibitors against 5-LOX (PDB-IDs 3V99 and 6N2W) and NF-κB (PDB-IDs 4KIK and 3DO7) through molecular docking, MM-GBSA calculation, molecular dynamic simulations (MDSs) and drug-likeness analysis. The eight lead molecules A169, A156, A162, A154, A102, A240, A86 and A58 were identified. The higher NF-B inhibiting potential of A169 was discovered through the sequential HTVS, SP docking and XP docking study. The hydrophobic interaction of Leu607, Phe610, Gln557 and Asn554 with 3V99 and Cys99, Glu97 and Arg20 of 4KIK is crucial for the inhibition. The LE, LLE and FQ values of A169 suggest their optimal binding with the target. This study strongly suggests the LOX and NF-κB inhibitory potential of A169, further lead optimisation and biological validation requires for the confirmations.Communicated by Ramaswamy H. Sarma.

Sex-Related Differences in Pharmacological Response to CNS Drugs: A Narrative Review

In the last decades, both animal and human studies have neglected female subjects with the aim of evading a theorized intricacy of feminine hormonal status. However, clinical experience proves that pharmacological response may vary between the two sexes since pathophysiological dissimilarities between men and women significantly influence the pharmacokinetics and pharmacodynamics of drugs. Sex-related differences in central nervous system (CNS) medication are particularly challenging to assess due to the complexity of disease manifestation, drugs’ intricate mechanisms of action, and lack of trustworthy means of evaluating the clinical response to medication. Although many studies showed contrary results, it appears to be a general tendency towards a certain sex-related difference in each pharmacological class. Broadly, opioids seem to produce better analgesia in women especially when they are administered for a prolonged period of time. On the other hand, respiratory and gastrointestinal adverse drug reactions (ADRs) following morphine therapy are more prevalent among female patients. Regarding antidepressants, studies suggest that males might respond better to tricyclic antidepressants (TCAs), whereas females prefer selective serotonin reuptake inhibitors (SSRI), probably due to their tolerance to particular ADRs. In general, studies missed spotting any significant sex-related differences in the therapeutic effect of antiepileptic drugs (AED), but ADRs have sex variations in conjunction with sex hormones’ metabolism. On the subject of antipsychotic therapy, women appear to have a superior response to this pharmacological class, although there are also studies claiming the opposite. However, it seems that reported sex-related differences regarding ADRs are steadier: women are more at risk of developing various side effects, such as metabolic dysfunctions, cardiovascular disorders, and hyperprolactinemia. Taking all of the above into account, it seems that response to CNS drugs might be occasionally influenced by sex as a biological variable. Nonetheless, although for each pharmacological class, studies generally converge to a certain pattern, opposite outcomes are standing in the way of a clear consensus. Hence, the fact that so many studies are yielding conflicting results emphasizes once again the need to address sex-related differences in pharmacological response to drugs.

EXOGENOUS Sex Hormones and Sex Hormone Receptor Modulators in COVID-19: Rationale and Clinical Pharmacology Considerations

Male patients with coronavirus disease 2019 (COVID-19) fare much worse than female patients in COVID-19 severity and mortality according to data from several studies. Because of this sex disparity, researchers hypothesize that the use of exogenous sex hormone therapy and sex hormone receptor modulators might provide therapeutic potential for patients with COVID-19. Repurposing approved drugs or drug candidates at late-stage clinical development could expedite COVID-19 therapy development because their clinical formulation, routes of administration, dosing regimen, clinical pharmacology, and potential adverse events have already been established or characterized in humans. A number of exogenous sex hormones and sex hormone receptor modulators are currently or will be under clinical investigation for COVID-19 therapy. In this review, we discuss the rationale for exogenous sex hormones and sex hormone receptor modulators in COVID-19 treatment, summarize ongoing and planned clinical trials, and discuss some of the clinical pharmacology considerations on clinical study design. To inform clinical study design and facilitate the clinical development of exogenous sex hormones and sex hormone receptor modulators for COVID-19 therapy, clinical investigators should pay attention to clinical pharmacology factors, such as dosing regimen, special populations (i.e., geriatrics, pregnancy, lactation, and renal/hepatic impairment), and drug interactions.

Influence of SLCO1B1 in gastric cancer patients treated with EOF chemotherapy

Cytochrome-P450 enzymes, ATP-binding cassette transporters, and solute carriers mediate drug metabolism as metabolic enzymes and membrane transporters, respectively. The present study investigated whether single nucleotide polymorphisms (SNPs) in genes encoding these proteins were predictive or prognostic factors in patients with metastatic gastric cancer (MGC) undergoing chemotherapy. A retrospective study of 108 MGC patients who received epirubicin, oxaliplatin, and 5-fluorouracil (EOF) as first-line treatment was performed. A total of 13 SNPs were genotyped, including SLCO1B1 (rs4149056), SLC2A9 (rs16890979, rs6449213, rs734553), ABCG2 (rs2231142), CYP2C9 (rs1057910, rs1799853), CYP2C19 (rs72552267, rs28399504, rs56337013, rs41291556) and CYP1A2 (rs12720461, rs56107638). The associations between these genotypes and disease-control rate (DCR), progression-free survival (PFS) and overall survival (OS) were analyzed. Patients with SLCO1B1 rs4149056 TT genotype had a significantly shorter OS compared with those with a C allele (CC + CT; 312 vs. 565 days, P=0.039). Multivariate analysis revealed that the rs4149056 TT homozygous genotype was an independent prognostic factor for shorter OS (hazard ratio: 2.565, 95% confidence interval: 1.215–5.415, P=0.014). However, no significant associations between SLCO1B1 rs4149056 and PFS were observed, between the other 12 SNPs and PFS or OS, or between any of the 13 SNPs and DCR. In conclusion, SLCO1B1 rs4149056 TT may be an independent predictor of survival in patients with MCG treated with EOF chemotherapy.

Profound reduction in the tamoxifen active metabolite endoxifen in a patient on phenytoin for epilepsy compared with a CYP2D6 genotype matched cohort

Tamoxifen is a prodrug, requiring cytochrome P450 enzyme-mediated metabolism to form the active metabolite endoxifen. We identified a case of drug-drug interaction involving tamoxifen and phenytoin, associated with a markedly lower endoxifen level than predicted. The patient is a 49-year-old woman, genotyped as a cytochrome P450 2D6 (CYP2D6) extensive metabolizer, chronically taking phenytoin for a seizure disorder. The plasma endoxifen level 2 months after starting tamoxifen was 4.72 nmol/l, the lowest level we have seen in our clinic among patients with CYP2D6 extensive metabolizer genotypes (n=195). To our knowledge, this is the first report documenting the extent of induction in terms of both tamoxifen and endoxifen levels during concomitant phenytoin therapy, and this effect would likely result in loss of therapeutic benefit from tamoxifen. Phenytoin should therefore not be used concurrently with tamoxifen for extended periods of time unless a therapeutic drug (endoxifen) monitoring strategy is utilized.

Oral Chemotherapy Food and Drug Interactions: A Comprehensive Review of the Literature

Oral chemotherapies are associated with medication and food interactions. It is essential that health care providers evaluate patients' concurrent medications to provide accurate patient education, therapeutic monitoring, and alternative recommendations whenever oral chemotherapy is prescribed.

Gender issues in antiepileptic drug treatment

The purpose of this review is to discuss gender-related aspects in the, pharmacokinetics, effects, selection and use of antiepileptic drugs (AED). In general, there are few known gender related differences in pharmacokinetics or efficacy of AEDs. Conversely, gender has a significant influence on the susceptibility to certain adverse effects, not the least those involving alterations in sex hormone metabolism. Particularly relevant are the teratogenic effects of AEDs, with important differences among AEDs in their potential to cause adverse effects on the fetus when used during pregnancy. Pregnancy can also markedly affect the pharmacokinetics of several AEDs, and dose adjustments are often needed during pregnancy to maintain seizure control. Some treatments that are used only by women, such as contraceptive steroids and hormone replacement therapy, can also interact with AEDs to an extent that may affect the utilization of both the AEDs and the other drug.

Effect of atorvastatin on CYP2C9 metabolic activity as measured by the formation rate of losartan metabolite in hypercholesterolaemic patients

HMG-CoA reductase inhibitors (statins) have a potential to interact with substrates of the drug-metabolizing enzyme cytochrome P450 2C9 (CYP2C9). This may lead to concentration-dependent toxicity such as skeletal muscle side effects. Atorvastatin, a widely used statin, is presently inadequately investigated in vivo with regard to effects on CYP2C9 activity in human beings. The aim of this study was to determine the effect of atorvastatin on the activity of CYP2C9 in a group of Turkish hypercholesterolaemic patients. We prospectively investigated the atorvastatin effect on CYP2C9 activity in a sample of Turkish hypercholesterolaemia patients (11 women, 7 men) who commenced atorvastatin (10 mg/day). Losartan was used as a probe drug to determine CYP2C9 metabolic activity. A single 25-mg oral dose of losartan was given to the patients before, on the first day and after the fourth week of the atorvastatin treatment. Urinary concentrations of losartan and its metabolite, E3174, were measured by high-pressure liquid chromatography (HPLC). Urinary losartan/E3174 ratios were used as an index of CYP2C9 activity. As the baseline enzyme activity may influence the extent of drug-drug interactions, the CYP2C9*2 and 2C9*3 alleles were identified by using PCR-RFLP. In the patients with the CYP2C9*1*1 genotype (n = 12), atorvastatin treatment did not cause a significant change in losartan/E3174 ratios (medians; 95% CI) neither after the first day (0.73; 0.34-1.61) nor at the fourth week (0.71; 0.36-1.77) of the treatment as compared with the baseline activity (0.92; 0.57-1.74, p = 0.38). Similarly, no significant change in the baseline CYP2C9 activity (0.91; 0.30-1.60) was observed in patients with the CYP2C9*1*2 genotype as compared with those of the first day (1.08; 0.08-2.72) and fourth week (0.64; 0.0-3.82) of the atorvastatin treatment (n = 4, p = 0.86). These observations in a hypercholesterolaemic patient sample suggest that atorvastatin does not have a significant effect on enzymes encoded by the CYP2C9*1*1 and CYP2C9*1*2 genotypes when co-administered with a CYP2C9 substrate, losartan.

CYP2C8 and CYP2C9 polymorphisms in relation to tumour characteristics and early breast cancer related events among 652 breast cancer patients

Background:

CYP2C8/9 polymorphisms may influence breast cancer-free survival after diagnosis due to their role in the metabolism of tamoxifen, paclitaxel, and other chemotherapy. cytochrome P450 (CYP)2C8/9 metabolise arachidonic acid to epoxyeicosatrienoic acids, which enhance migration and invasion in vitro and promote angiogenesis in vivo. We aimed to investigate the frequency of CYP2C8/9 polymorphisms in relation to breast tumour characteristics and disease-free survival.

Methods:

A prospective series of 652 breast cancer patients from southern Sweden was genotyped for CYP2C8*3, CYP2C8*4, CYP2C9*2, and CYP2C9*3. Blood samples and questionnaires were obtained pre- and postoperatively. Clinical information and tumour characteristics were obtained from patients' charts and pathology reports.

Results:

Frequencies of CYP2C8/9 polymorphisms were similar to healthy European populations. Significantly less node involvement (P=0.002) and fewer PR+ tumours (P=0.012) were associated with CYP2C8*4. Median follow-up was 25 months and 52 breast cancer-related events were reported. In a multivariate model, CYP2C8/9*3/*1*/*2/*1 was the only factor associated with increased risk for early events in 297 tamoxifen-treated, ER-positive patients, adjusted HR 2.54 (95%CI 1.11–5.79). The effect appeared to be driven by CYP2C8*3, adjusted HR 8.56 (95%CI 1.53–51.1).

Conclusion:

Polymorphic variants of CYP2C8/9 may influence breast tumour characteristics and disease-free survival in tamoxifen-treated patients.

Safety of Concomitant Tamoxifen and Warfarin

Objective:

To review the literature regarding the potential interaction between tamoxifen and warfarin.

Data Sources:

A search of MEDLINE from 1948 to August 20, 2009, was performed using the search terms tamoxifen, warfarin, drug interactions, and cytochrome P450 2C9. EMBASE was searched (1980–week 33, 2009), using the search terms tamoxifen and warfarin, for articles limited to use in humans and published in English, then further narrowed to drug interactions. Bibliographic review was conducted but did not reveal any additional references.

Study Selection and Data Extraction:

All sources evaluated were published in English and included original case reports, letters, and medical record or database reviews that described an interaction between warfarin and tamoxifen.

Data Synthesis:

Since tamoxifen therapy and cancer increase the risk of venous thromboembolism, warfarin may be prescribed to these patients. However, product information, primary literature, and tertiary literature describe concomitant use of tamoxifen and warfarin as a contraindication since this may increase the level of anticoagulation and the risk of bleeding complications. Although the exact mechanism of the interaction is unknown, one theory is that tamoxifen inhibits CYP2C9, which metabolizes the S-isomer of warfarin. Five publications were identified including 2 letters, 2 individual case reports, and 2 retrospective reviews (1 of the case reports was included in a medical record review). Collectively, these articles described a total of 31 patients taking warfarin and tamoxifen concomitantly, with 8 patients experiencing bleeding complications.

Conclusions:

Although concomitant use of warfarin and tamoxifen is deemed a contraindication, evidence regarding this potential interaction is limited. Therefore, safety of concomitant use of tamoxifen and warfarin may be similar to that of other drugs that interact with warfarin, requiring consistent and careful monitoring. However, more evidence is needed to warrant the routine use of this combination.