Association between CYP3A4/CYP3A5 genetic polymorphisms and treatment outcomes of atorvastatin worldwide: is there enough research on the Egyptian population?

Introduction Atorvastatin is regarded as the most frequently prescribed statin worldwide for dyslipidemia. However, clinical response and risk of adverse effects to statin therapy are associated with genetic variations. Numerous research linked statins pharmacokinetics (PK) variations to genetic polymorphisms in cytochromes P450 (CYPs) metabolic enzymes. Objective This article reviews the association between CYP3A4/5 genetic variations and response to atorvastatin therapy globally, which includes atorvastatin PK, and the risk for adverse reactions, with a hint to the Egyptians. Methods Up to March 30, 2022, electronic medical databases like PubMed, Web of Science, MEDLINE, and Egyptian Knowledge Bank (EKB) were searched. All articles that highlighted the relationship between CYP3A4/5 genetic polymorphisms and atorvastatin efficacy/safety profile were included in this review. Results Initially, 492 articles were retrieved after an exhaustive search. There were 24 articles included according to the inclusion criteria. Findings of association studies of CYP3A4/5 genetic polymorphisms with response to atorvastatin varied among different ethnicities. CYP3A4*1B was associated with better therapeutic outcomes after atorvastatin therapy in Chileans and vice versa in Americans. Caucasians with myalgia while using atorvastatin were at significant risk of suffering severe muscle damage if they were carriers of CYP3A5*3/*3. As far as we can report for the Egyptian population, the impact of CYP3A4/5 genetic variations on the response to atorvastatin therapy was understudied. Conclusion More pharmacogenetic studies amongst diverse populations worldwide, like the Egyptian population, are necessary to detect further atorvastatin-gene interactions. Graphical Abstract


Introduction
Pharmacogenetics is a practical approach that predicts both sub-therapeutic responses to pharmacologic treatments and increased risks of adverse drug reactions [1].Natural genetic variations in human genes result in different responses to drug treatments [2].Pharmacogenetics is essential in assessing the influence of genetic mutations on responses to pharmacologic therapies [3].CYPs metabolize a great deal of clinically used medications [4].Any noticeable change in the levels of the metabolites could occur, in part, due to genetic polymorphisms of these vital enzymes, resulting in changes in the therapeutic outcomes of drugs [5,6].The metabolism of drugs is considered an essential process that determines responses to medications, adverse effects, and pharmacokinetics [6].The strategies of precise medicine will necessitate screening genotypes and phenotypes [7].Several investigations have been conducted to study the influence of CYPs' genetic variations on the pharmacokinetics of drugs [6].In the same context, having CYPs polymorphisms can be considered a risk factor for developing myopathy and hepatic injury due to statin therapy [8].CYPs' genetic variations result in differences in medication responses among people from different ethnicities [9][10][11].
Differences in the pharmacokinetics of statins were related to genetic polymorphisms in metabolic enzymes such as CYP3A4 and CYP3A5 [12].Atorvastatin is considered one of the most recommended medications and the utmost extensively prescribed statin worldwide [13].It is, however, associated with several adverse reactions, such as nausea, nasopharyngitis, insomnia, urinary tract infections, elevation in hepatic enzymes, diarrhea, dyspepsia, myalgia, and arthralgia [14].Statin-related muscle symptoms are the frequently reported statin-induced reactions, whereas liver toxicities and central nervous system manifestations are less common.Statin-induced adverse reactions lead to noticeable morbidities, more costs, and non-adherence or discontinuation of statin therapy [15,16].
In Egypt, 46% of overall deaths are related to cardiovascular diseases (CVD) [17,18].Dyslipidemia increases the risk of CVD.Several studies showed that high blood cholesterol had been found in 37% of Egyptians [18][19][20].
Results of association studies of either CYP3A4 or CYP3A5 genetic polymorphisms with atorvastatininduced adverse reactions or atorvastatin efficacy were controversial or inconsistent [23].Accordingly, this article aims to review the association between CYP3A4/5 genetic variations with response to atorvastatin pharmacological treatment in different ethnic groups, focusing on the Egyptian population.

Study eligibility
This review includes journal articles that are full-text, peer-reviewed, and limited to the English language.The selected articles represented clinical trials, retrospective or prospective observational studies, review articles, or in vitro studies.The nominated articles must include the association between CYP3A4/CYP3A5 polymorphisms and atorvastatin response/safety profile.

Selection of articles
Screening for eligibility was accomplished through three stages: In stage one, the titles were evaluated for relevance.In stage two, abstracts were screened for being eligible.Finally, in stage 3, full-text articles of selected abstracts were assessed (methodology and results) for their eligibility to be included in this review.Exclusion criteria included non-English language literature, duplicate articles, irrelevant methodology to the objectives, and books.

Data extraction
Data were extracted by (MGM) who separately appraised all the designated articles to extract the relevant ones for this review.One researcher (MGM) accomplished the inclusion process, and in case of uncertainty about article inclusion, a second researcher (MAR) was consulted.

Search results
Figure 1 shows that an initial list of 492 retrieved articles included 141 articles for phase 1, 183 articles for phase 2, 84 articles for phase 3, 84 articles for phase 4, and no articles for phase 5. Regarding phase 1, the 141 articles included 11 articles from PubMed, 26 articles from MEDLINE, 44 from Web of Science, and 60 from EKB.For phase 2, the 183 articles included 12 articles from PubMed, 35 from MEDLINE, 71 from Web of Science, and 65 from EKB.For phase 3, the 84 articles included three articles from PubMed, eight from MEDLINE, eight from Web of Science, and 65 from EKB.Finally, for phase 4, the 84 articles included three articles from PubMed, nine from MEDLINE, nine from Web of Science, and 63 from EKB.Table 1 illustrates eligible and selected articles (i.e., n = 24) included in this review according to the inclusion criteria.

Response to atorvastatin
Table 2 demonstrates the effect of CYP3A4/5 genetic variations on atorvastatin response.
Effects of CYP3A4 polymorphism A review article showed that atorvastatin and several statins' metabolic pathways depend on CYP3A4.Therefore, any mutation in this gene could result in a significant alteration in the PK of these statins [24].The outcome of Maekawa et al. in vitro study illustrated that CYP3A4*16 variant found in East Asia had more than 60% decreased functional activity for atorvastatin.Furthermore, the study concluded that the clinical significance of the results should be examined in other prospective studies [29].In this context, Jani et al. reported that a genetic mutation in CYP3A4 can result in variation in the pharmacologic properties of statins like atorvastatin.The study found that genetic variations in CYP3A4 gene influenced CYP3A4 enzyme activity and affected atorvastatin metabolism in 125 Indian subjects in Gujarat [30].

Positive consequences of polymorphism
Increase in serum HDL-C level: Genetic mutations in CYP3A4 and other five genes affected the therapeutic efficacy of atorvastatin in Indians, suffering from coronary artery disease.Poduri et al. reported CYP3A4 allele (189F/S) was linked to elevated high-density lipoprotein cholesterol (HDL-C) levels after atorvastatin therapy (P<0.05)[31].
Decrease in serum LDL-C level: Peng et al. reported that a single nucleotide polymorphism (SNP) of CYP3A4, rs2242480, was associated with a reduction in serum LDL-C level among Chinese patients with ischemic stroke (P = 0.049) [33].In this context, Kajinami et al. reported that M445T variant of CYP3A4 gene was associated with a significantly lower pretreatment serum LDL-C levels (11.2%) in carriers of this variant relative to non-carriers.In addition, in the M445T allele carriers, a higher LDL-C lowering response to atorvastatin was detected among 340 Americans suffering from primary hypercholesterolemia, although it failed to reach statistical significance [24,34].

Negative consequences of polymorphism
Increase in serum LDL-C level: From the same perspective, CYP3A4 genetic polymorphisms could decrease the pharmacological effect of atorvastatin.For example, Kajinami et al. showed that after 52 weeks of atorvastatin therapy (10 mg/day), the A-290G mutant allele of CYP3A4 (CYP3A4*1B) was related to increased levels of LDL-C in 340 American subjects with hypercholesterolemia (P<0.05)[24,34,35].
Less serum LDL-C level decline: After 8 weeks of atorvastatin treatment (10 mg/day) among 177 Indians, Kadam et al. illustrated that the variant-allele of

S.no Author (s) Main Objective (s)
1 Dagli-Hernandez et al. [15] To review clinical trials on pharmacogenomics of statins regarding the Brazilian population 2 Rosales et al. [21] To evaluate the response to atorvastatin in Chilean hypercholesterolemic patients with PMs a in ABCB1 b , CYP3A5 c , and CYP3A4 c genes 3 Shitara, Sugiyama.[24] To review statins' PK d and physicochemical issues and specific aspects such as PMs a that could affect PK d To explore the impact of microRNA on the inherited malfunctioning CYP3A4/5 c enzymes and atorvastatin metabolism CYP3A4 rs2740574 was associated with a lower LDL-C serum level reductions than the wild-type allele (P<0.05)[36].
Effects of CYP3A5 polymorphism Carriers of at least a copy of CYP3A5*1 allele (wild-type) express CYP3A5 protein, whereas CYP3A5*3 homozygotes are designated as CYP3A5 non-expressors [25].A study reported the genotype frequency of the CYP3A5 genetic variations in 350 unrelated Greek Caucasian cases with primary hypercholesterolemia: 13.4% for expressors and 86.6% for nonexpressors (homozygous) subjects [38].CYP3A5 enzyme is not expressed in about 90% of Caucasians [25].

Negative consequences of polymorphism
Decline in response to atorvastatin: A review by Dagli-Hernandez et al. about clinical trials in Brazilians showed that variations in the CYP3A5 gene were associated with a reduction in response to atorvastatin and simvastatin therapy [15].In the same context, a Brazilian study involving 139 subjects illustrated that the CYP3A5*3A variant (*1D and *3C combined variants) was linked to a decrease in cholesterol-lowering response to atorvastatin-4 weeks therapy in non-African subjects only.In this study, 93 subjects with non-African ancestry were recruited, and the remaining 46 individuals were Africans [35,39].Non-Africans carrying the CYP3A5*3C allele (*3C/*3C genotype) had less decline in serum TC and LDL-C than carriers of CYP3A5*1A allele after atorvastatin treatment (P<0.05).In addition, the CYP3A5*1D analysis illustrated that for the *1D variant (*1D/*1D genotype) among non-Africans, carriers had less reduction of TC and LDL-C levels than carriers of CYP3A5*1A allele after atorvastatin treatment (P<0.05) [39].

Atorvastatin safety profile
Effects of CYP3A4 polymorphism A review by Vrablik et al. indicated that mutant alleles within CYP3A4 have been proposed to be linked to myopathy as an adverse effect of stains.Moreover, CYP3A4 has been indirectly associated with myopathy in atorvastatin users due to its overrepresentation in these patients needing dose reduction or switching from atorvastatin to alternatives [40,41].Furthermore, Xia et al. screened 187 Chinese subjects for wild alleles CYP3A4*1B (rs2740574) and CYP3A4*1G (rs2242480) in addition to other genes involved in atorvastatin metabolism and transport in vivo.However, only six candidates were enrolled to study atorvastatin PK.As a result, atorvastatin's maximum plasma concentration (Cmax) was significantly elevated (high atorvastatin exposure).In addition, one subject of the candidates was terminated during the study due to atorvastatin intolerance [42].However, according to Becker et al. cohort study, the G allele of CYP3A4*1B in Dutch users of atorvastatin or simvastatin was linked to a reduced risk for statin intolerance, specifically among females and carriers of the mutant allele (3435T) of the transporter ABCB1 [41].

Effects of CYP3A5 polymorphism Liu et al. in vitro study
showed that atorvastatin metabolism is decreased and significantly associated with CYP3A5*3.In addition, the two atorvastatin metabolites, para-OH-atorvastatin and ortho-OH-atorvastatin, were significantly reduced in carriers of CYP3A5*3/*3 [43].This finding was consistent with severe muscle damage associated with CYP3A5*3/*3 [43,44].Wilke et al. conducted an American retrospective case-control study on 137 Caucasian subjects with European ancestry.It showed that the CYP3A5*3 variant was allied to the increase in the serum level of creatine kinase (CK) in the case of individuals with myalgia.The study concluded that individuals with myalgia while using atorvastatin were at a high risk of developing a severe myopathy if they were carriers of the CYP3A5*3/*3 genotype (P<0.05)[44,45].Also, the previously mentioned Chinese study on atorvastatin PK by Xia et al. illustrated the significant elevation in atorvastatin Cmax.This risky elevation was also associated with the allele CYP3A5*3(rs776746) in addition to the previously stated genes for atorvastatin metabolism and other two genes for atorvastatin transport: solute carrier organic anion (SLCO) transporter; (SLCO1B1 388A>G (rs2306283) and SLCO1B1 521T>C(rs4149056)) [42].Quite the opposite, a Spanish pharmacogenetic study by Zubiaur et al. on 156 subjects (81 Caucasians, 70 Latin Americans, and 5 Blacks or Arabs) showed that atorvastatin accumulation was higher among CYP3A5*1/*1 carriers than *1/*3 or *3/*3 carriers.The authors justified this novel finding by illustrating the first-pass effect on the administered acid form of atorvastatin.Therefore, regarding the CYP3A5*1/*1 genotype, atorvastatin was metabolized to a greater extent in the gut.This genotype resulted in active metabolites and inhibitors of CYP3A4 (responsible mainly for atorvastatin metabolism).Consequently, CYP3A5*3 variant was significantly linked to lower atorvastatin Cmax than CYP3A5*1 (p = 0.018) [26].

Discussion
The association studies of CYP3A4 and CYP3A5 polymorphisms with response to atorvastatin treatment were inconsistent [21,23].

Effects of CYP3A4 polymorphism
As mentioned in this review, Rosales et al. researched Chilean subjects and showed that CYP3A4*1B was associated with better therapeutic outcomes after atorvastatin therapy [21].However, the same variant (CYP3A4*1B) was linked to high levels of LDL-C in Americans after atorvastatin treatment, as reported by Kajinami et al. [24,34,35].On the other hand, research on the Indian population has shown no significant relation between the CYP3A4*1B gene (rs2740574) and low values of LDL-C as a response to atorvastatin therapy [31,46].Reports for CYP3A4*1B metabolic activity were conflicting [34].Rosales et al. attributed the positive therapeutic consequences after atorvastatin treatment to CYP3A4 metabolic lower activity in vivo due to the CYP3A4*1B allele.However, the study was restricted by the sample size [21].On the contrary, Kajinami et al. found serum LDL-C elevation was consistent with CYP3A4-increased enzyme activity [34].

Effects of CYP3A5 polymorphism
In Greek subjects, Kolovou et al. showed that although HDL-C levels did not vary meaningfully after atorvastatin treatment, the LDL-C, TC, and triglyceride (TG) serum levels were decreased significantly in both genotypes CYP3A5*3/*3 and CYP3A5*1/*3 [38].In addition, Kivistö et al., while researching European Caucasian subjects, revealed that the CYP3A5*3 variant led to an enhanced response to atorvastatin [24,25,35].However, the Brazilian study showed that the CYP3A5*3A variant was associated with a decreased cholesterol-lowering response to atorvastatin in subjects with non-African ancestry [35,39].
In contrast, research on Chilean patients showed that both the G and A alleles of the CYP3A5*3 (rs776746) variant did not affect response to atorvastatin treatment [21].In addition, a retrospective cohort study performed among Caucasian subjects illustrated no association between the CYP3A5*3 allele and atorvastatin PK [23,47].Differences among the mentioned studies indicate that the relationship between the CYP3A5*3 allele and response to atorvastatin could depend on factors such as the period of treatment and ethnicity [39].

Effects of CYP3A4 polymorphism
In Chinese subjects, Xia et al. showed that CYP3A4*1B(rs2740574) and other genes involved in atorvastatin metabolism and transport in vivo were associated with risky high atorvastatin exposure [42].However, in Dutch users of atorvastatin or simvastatin, according to the research of Becker et al. the same variant CYP3A4*1B was associated with a low risk for statin intolerance [41].
Conversely, an open-label randomized study illustrated that CY3A4*1B (rs2740574) was not associated with atorvastatin therapy intolerance, the elevation of CK, or muscle pain in Caucasians as well as African American subjects [23,48].

Effects of CYP3A5 polymorphism
Regarding Caucasian subjects, Wilke et al. concluded that patients with myalgia while using atorvastatin were at significant risk of suffering severe muscle damage if they were carriers of CYP3A5*3/*3 [44,45].However, Zubiaur et al. reported that high risky atorvastatin exposure was associated with CYP3A5*1/*1.Noticeably, more research is required regarding the controversy with this novel finding [26].
In opposition, a study involving Han Chinese patients demonstrated that the G allele of the CYP3A5*3 (rs776746) variant was not associated with myotoxicity as an adverse effect of atorvastatin therapy [49].Furthermore, the same result was demonstrated in a case-control study in which indigenous American, sub-Saharan, East Asian, and European subjects were recruited [23,50].To identify the frequencies of CYP3A5*3 b and SLCO1B3 d (T334G) in chronic myeloid leukemia cases receiving imatinib therapy and assess the impact of these polymorphisms on the response to imatinib 6 Abo El Fotoh, et al. [57] To determine the effect of CYP3A5*3 b and SCN1A e c.3184 A/G polymorphisms on pharmaco-resistance in Egyptian epileptic pediatric patients

CYP3A4/5 polymorphisms among Egyptian population
As far as we can report for the Egyptians, the effect of CYP3A4/5 genetic polymorphisms on the response to atorvastatin treatment was understudied.However, some pharmacogenetic studies on Egyptians (Table 3) were performed to better define "Egyptian" genetic variants and assess their significance for common disease states or drugs other than the one under investigation [51].Regarding CYP3A4 genetic variations among Egyptians, pharmacogenomic research performed at the pediatric hospital, Faculty of Medicine, Mansoura University has reported an allele frequency of 2% for the CYP3A4*22 allele.It is the first study illustrating the CYP3A4*22 variant frequency in the Egyptian population [52].Moreover, the frequency of an additional variant rs4646437 in the CYP3A4 gene was reported in another Egyptian study to be 20%.The study involved 50 Egyptian patients after kidney transplantation at the Renal Transplantation Unit of Alexandria University Hospital [53].
Concerning CYP3A5*3 polymorphism among Egyptians, a study was conducted at the adult oncology department, National Cancer Institute, Cairo University.The results showed that the frequency of CYP3A5*3 was higher at 81.5% in acute myeloid leukemia cases compared to controls [54].Another Egyptian study at Urology and Nephrology Center, Mansoura University Hospital, published in August 2020, demonstrated that the CYP3A5*3 allele was the most prevalent variant (85.53%) in 76 renal transplantation recipients.This study was the first Egyptian research focusing on the personalization of tacrolimus doses in Egyptian cases according to the CYP3A5 genotypes [55].Another research on Egyptian cases of chronic myeloid leukemia (CML) was performed at the Hematology Department, Medical Research Institute, Alexandria University.This research was designed to illustrate the role of CYP3A5*3 polymorphism in determining the response to imatinib in 86 CML Egyptian cases.The results showed that the frequency of CYP3A5*3 was 53% and 69% in 78 (early chronic phase) cases and eight (accelerated phase) cases, respectively [56].Moreover, another Egyptian pharmacogenetic research on 130 epileptic children was held at Pediatrics Department, Menoufia University Hospital.The research aimed to show the role of CYP3A5*3 genetic variation in predicting resistance to antiepileptic medications in Egyptian epileptic pediatric cases.The prevalence of CYP3A5*3 was 76.9% and 77.7% in epileptic (n=130) and control (n=65) participants, respectively [57].Due to the limited data about pharmacogenes of significant clinical importance, 145 healthy unrelated Egyptian children were included in research at Mansoura University Children's Hospital.This pharmacogenomic research aimed to screen common genetic variants in certain CYPs, including CYP3A5, among the Egyptian population.The prevalence of variant 6986A>G (rs776746) in the gene CYP3A5 was 86.2% [52].
Findings of association studies of CYP3A4/5 genetic polymorphisms with response to atorvastatin treatment varied among different ethnicities.CYP3A4*1B (rs2740574) and CYP3A5*3 (rs776746) were reported in the literature as either associated with the risk for atorvastatin intolerance in a particular population or associated with a low possibility for risky atorvastatin exposure in another population.In addition, both variants were reported to be either associated with better therapeutic outcomes after atorvastatin treatment in a definite population or with poor therapeutic consequences in another.Focusing on the Egyptian population, both alleles C and T of the variant CYP3A4*1B (rs2740574) in the CYP3A4 gene, as far as we know, were not studied before.In addition, the effects of genetic polymorphisms of both CYP3A4 (rs2740574 C/T) and CYP3A5*3 (rs776746 T/C) on atorvastatin PK or its induced adverse effects were not previously studied in Egyptians.Consequently, prospective pharmacogenomics studies amongst Egyptians will assist many people in this population suffering from hypercholesterolemia and are at high risk of CVD complications.Therefore, the outcomes would tailor atorvastatin treatment based on the patient's genotype.

Conclusions
CYP3A4/5 genetic variants have been studied for their potential associations with response to atorvastatin treatment.However, the findings differed according to ethnicity.Therefore, more pharmacogenetic research in various populations worldwide, like the Egyptian population, is required to elucidate the impact of genetic polymorphism of these CYP enzymes on atorvastatin response and risk of side effects with genotype-guided dosing and precision medicine initiatives.

Table 1
Main objectives of the 24 articles eligible for inclusion in this review

Table 2
et al. studied 46 Europeans Overview of CYP3A4/5 polymorphisms effect on the response to atorvastatin

Table 3
Main objectives of the articles that investigated CYP3A4/5 polymorphisms among the Egyptian population