Recent advances in pharmacogenetic approaches to anticancer drug development

Selectivity modulation and its prediction in cyclofructan-6 phase for chaotropic ions

BACKGROUND

Modifying additives to alter the selectivity of a single stationary phase and solvent system is appealing in mixed-mode separations. Silica-bonded cyclofructan-6 uniquely binds with cations strongly in the presence of organic solvents and is hydrolytically stable. Perchlorate with inorganic and organic quaternary ammonium cations could adjust retention for molecules with carboxylic acids, sulfonic acids, and nitrogen-containing functional groups, which are common in pharmaceutically relevant molecules. Perchlorate salts of ammonium, lithium, tetrabutylammonium, and tetramethylammonium were assessed for their selectivity in acetonitrile-water eluent systems.

RESULTS

This study provides a mathematical route to accomplish complex selectivity alterations by simply varying the perchlorate counterions. Two predictive tests based on l2-norm and principal component analysis (PCA) were proposed to choose the most distinct perchlorate additive pair for 17 test probes in retention time-space. The l2-norm provides a faster approach to measure variation caused by eluent additives for probe analytes. Ammonium and tetrabutylammonium perchlorate salts showed the maximum "distance" between them. The eluent additives strongly affected the elution times of carboxylic and sulfonic acids, and neutrals were mildly altered. A concentration study on these two additives with probe analytes ruled out a simple ion exchange interaction and suggested a multimodal retention mechanism. All additives yielded high-efficiency separations expected of 2.7 μm core-shell particles.

SIGNIFICANCE

The proposed mathematical tests will assist chromatographers in selecting distinct eluent additives for different classes of separations during method development. The applicability of the eluent selection strategy has been shown with the separation of three different biologically important classes of molecules containing analytes like cocaine, amphetamine, tianeptine, serotonin, lorazepam, and 5-fluorouracil.

How to measure the probability of uracil chain tautomers as nucleotide bases in RNA?

The current research focuses on exploring tautomerism in uracil. 47 tautomers were found that varied in significance in RNA and stability. To discover these molecules, diverse potential energy levels were explored, and corresponding transition states were found in these pathways. But the imperative thing that was taken note in this investigation is that for the first time, a method was detailed for the probability of forming distinctive molecules relative to each other. In this method, the conversion of uracil and its tautomers, which together turn into 47 molecules, was composed as a Markov chain. Then, the transition matrix was explained using its support, whose components are the probability of creating molecules from each step. At last, by multiplying this matrix by n times, the probability of forming different molecules was obtained. Moreover, by solving this matrix at different times, it is conceivable to appear which molecules can be converted to uracil sooner. It was appeared that a few tautomers act as transitory absorption point or temporary terminal states and other molecules, to begin with convert to these molecules before turning into uracil.

Development of a Divergent Synthesis Strategy for 5-Sulfonyl-Substituted Uracil Derivatives

An efficient, diversity-orientated synthesis of 5-sulfone-substituted uracils was established. The use of protecting groups to synthesize sulfones from N-heterocycles was avoided. Various heterocycles were synthesized for the first time from favorable, easily accessible starting materials. Diversity-orientated syntheses are important for the medicinal chemistry of virostatics and chemotherapeutics. This approach provides a broad substrate tolerance and excellent yields of up to 98%.

It Takes Two to Tango, Part II: Synthesis of A-Ring Functionalised Quinones Containing Two Redox-Active Centres with Antitumour Activities

In 2021, our research group published the prominent anticancer activity achieved through the successful combination of two redox centres (ortho-quinone/para-quinone or quinone/selenium-containing triazole) through a copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. The combination of two naphthoquinoidal substrates towards a synergetic product was indicated, but not fully explored. Herein, we report the synthesis of 15 new quinone-based derivatives prepared from click chemistry reactions and their subsequent evaluation against nine cancer cell lines and the murine fibroblast line L929. Our strategy was based on the modification of the A-ring of para-naphthoquinones and subsequent conjugation with different ortho-quinoidal moieties. As anticipated, our study identified several compounds with IC₅₀ values below 0.5 µM in tumour cell lines. Some of the compounds described here also exhibited an excellent selectivity index and low cytotoxicity on L929, the control cell line. The antitumour evaluation of the compounds separately and in their conjugated form proved that the activity is strongly enhanced in the derivatives containing two redox centres. Thus, our study confirms the efficiency of using A-ring functionalized para-quinones coupled with ortho-quinones to obtain a diverse range of two redox centre compounds with potential applications against cancer cell lines. Here as well, it literally takes two for an efficient tango!

Fused and Substituted Pyrimidine Derivatives as Profound Anti-Cancer Agents

The rationale behind drug design is the strategic utilization of heterocyclic fragments with specific physicochemical properties to form molecular targeted agents. Among the heterocyclic molecules, pyrimidine has proved to be a privileged pharmacophore for various biological cancer targets. The anti-cancer potential of small molecules with fused and substituted pyrimidines can be enhanced through bioisosteric replacements and altering their ADME parameters. Although several small molecules are used in cancer chemotherapy, oncology therapeutics has various limitations, especially in their routes of administration and their concurrent side effects. Such pernicious effects may be overcome, via selective biological targeting. In this review, the biological targets, to inhibit cancer, have been discussed. The structural activity relationship of fused and substituted pyrimidines was studied. Eco-friendly synthetic approaches for pyrimidine derivatives have also been discussed. This review will give an insight to scientists and researchers of medicinal chemistry discipline to design small molecules having a pyrimidine scaffold with high anti-cancer potential.

5,5-Di-chloro-6-hy-droxy-dihydro-pyrimidine-2,4(1H,3H)-dione: mol-ecular and crystal structure, Hirshfeld surface analysis and the new route for synthesis with Mg(ReO4)2 as a new catalyst

The mol-ecular and crystal structures of the title compound, C4H4Cl2N2O3, were investigated by single-crystal X-ray diffraction and a Hirshfeld surface analysis. The title compound was synthesized by a new type of reaction using Mg(ReO4)2 as a new catalyst and a possible mechanism for this reaction is proposed. The six-membered ring adopts a half-chair conformation. In the crystal, hydrogen bonds connect the mol-ecules into double layers, which are connected to each other by halogen bonds. The Hirshfeld surface analysis revealed that the most important contributions for the crystal packing are from O⋯H/H⋯O (35.8%), Cl⋯Cl (19.6%), Cl⋯H/H⋯Cl (17.0%), H⋯H (8.3%), C⋯O/O⋯C (4.3%), Cl⋯O/O⋯Cl (4.2%) and O⋯O (4.1%) contacts.

Therapeutic potential of uracil and its derivatives in countering pathogenic and physiological disorders

Uracil is one of the most notable pharmacophores in medicinal chemistry as the pyrimidine nucleobase forms an integral part of many commercial drugs. Though the name uracil is usually associated with cancer drugs, there are many uracil-based compounds which can treat different diseases when they are employed. So far, there has been no in-depth review concerning uracil drugs in the market, or in the different stages of clinical trials, including those approved or discontinued. The current work focuses on the importance of uracil and its derivatives in treating different diseases. The use of uracil compounds in treating viral infections, cancer, diabetic, thyroid and autosomal recessive disorders are discussed in the review. The mechanism of action of each uracil drug with emphasis on their structure and properties are discussed in detail. The targeted action of these drugs on sites or on the different stages of a disorder/pathogenic life cycle are also discussed. This review encompasses uracil drugs approved as well as those in development from the 1950's onwards. The utility of uracil in drug discovery and its association with a wide range of diseases is brought forth within this review to demonstrate its potential to a wider audience.

"Watson-Crick G[triple bond, length as m-dash]C"-inspired supramolecular nanodrug of methotrexate and 5-fluorouracil for tumor microenvironment-activatable self-recognizing synergistic chemotherapy

Carrier-free nanodrugs, generated via the straightforward small-molecule self-assembly of anticancer drugs, provide a promising route for cancer chemotherapy. However, their low structural stability, lack of targeting specificity, and poor stimulus responsiveness are still limiting their therapeutic effect. Inspired by Watson-Crick G[triple bond, length as m-dash]C base pairing, the FDA-approved chemo-drug methotrexate (MTX, which can bind with folate receptors) and 5-fluorouracil (5-FU, a DNA/RNA synthetase inhibitor) were adopted for direct assembly into self-recognizing MTX-5-FU nanoparticles via "Watson-Crick-like base pairing"-driven precise supramolecular assembly. Sequentially, our synthesized weak acidity-responsive polyethylene glycol (PEG) was inserted onto the nanoparticle surface to temporarily shield the self-targeting function of MTX and prolong the blood circulation time. Once PEG-MTX-5-FU nanoparticles reached the weakly acidic tumor microenvironment, the PEG corona could be cleaved from their surface and then MTX could be re-exposed to recover its self-recognition ability and significantly elevate tumor cell uptake; furthermore, the de-PEGylated MTX-5-FU nanoparticles could respond to the stronger acidity of lysosome, triggering core disassembly and thus the burst release of both MTX and 5-FU. Further in vitro and in vivo studies consistently confirmed that the nanodrugs exhibited preferable accumulation at the tumor sites with highly synergistic chemotherapeutic effects. The supramolecular recognition-inspired, cascade-triggered self-targeting and controlled release of nanodrugs could be a promising strategy to improve synergistic chemotherapy.

Synthesis and evaluation of coumarin derivatives against human lung cancer cell lines

Series of novel coumarin derivatives [I (a–d) and II (a–d)] were successfully synthesized and their structures were determined based on infrared 1H-nuclear magnetic resonance (NMR), HRMS, and single crystal X-ray crystallography. Additionally, the new synthesized compounds were evaluated to identify the molecular characteristics that contribute to their cytotoxicity, which was tested against SK-LU-1, SPC-A-1 and 95D human lung cancer cell lines, using the MTT assay. The results of this study showed that compounds Ic, Id, IIc, and IId exhibited an efficient percentage of inhibition of cell proliferation.

Carbonic anhydrase inhibitory properties of some uracil derivatives

Inhibitors of carbonic anhydrase (CA) have been carried out in many therapeutic applications, especially antiglaucoma activity. In this study, we investigated some uracil derivatives (4–12) to inhibit human CA I (hCA I) and II (hCA II) isoenzymes. The K_I values of the compounds 4–12 are in the range of 0.085–428 µM for hCA I and of 0.1715–645 µM against hCA II, respectively. It is concluded from the kinetic investigations, all compounds used in the study act as competitive inhibitors with substrate, 4-NPA. Uracil derivatives are emerging agents for the inhibiton of carbonic anhydrase which could be used in biomedicine.

Molecular Modeling Studies of Some Uracil and New Deoxyuridine Derivatives

Molecular modeling results reported in this paper are crucial in highlighting the quantitative relationship between the optimized structure and computed molecular properties related to four newly synthesized uracil derivatives with promising biological potential as anticancer bioactive agents. Moreover, 5-fluorouracil (5-FU) and its tautomers and thiouracils molecular properties are studied and correlated with their biological activities. The great medical importance of these and similar molecular systems requires research on their quantitative structure-activity relationships (QSAR) in order to further improve our knowledge about how receptor binding, selectivity, and pharmacological effects are achieved. Modeling is performed in the ground and the first singlet excited states using density functional theory (DFT) and its time-dependent extension (TD-DFT), respectively.

In search of uracil derivatives as bioactive agents. Uracils and fused uracils: Synthesis, biological activity and applications

This review article is an effort to summarize recent developments in researches providing uracil derivatives with promising biological potential. This article also aims to discuss potential future directions on the development of more potent and specific uracil analogues for various biological targets. Uracils are considered as privileged structures in drug discovery with a wide array of biological activities and synthetic accessibility. Antiviral and anti-tumour are the two most widely reported activities of uracil analogues however they also possess herbicidal, insecticidal and bactericidal activities. Their antiviral potential is based on the inhibition of key step in viral replication pathway resulting in potent activities against HIV, hepatitis B and C, the herpes viruses etc. Uracil derivatives such as 5-fluorouracil or 5-chlorouracil were the first pharmacological active derivatives to be generated. Poor selectivity limits its therapeutic application, resulting in high incidences of gastrointestinal tract or central nervous toxicity. Numerous modifications of uracil structure have been performed to tackle these problems resulting in the development of derivatives exhibiting better pharmacological and pharmacokinetic properties including increased bioactivity, selectivity, metabolic stability, absorption and lower toxicity. Researches of new uracils and fused uracil derivatives as bioactive agents are related with modifications of substituents at N(1), N(3), C(5) and C(6) positions of pyrimidine ring. This review is an endeavour to highlight the progress in the chemistry and biological activity of the uracils, predominately after the year 2000. In particular are presented synthetic methods and biological study for such analogues as: 5-fluorouracil or 5-chlorouracil derivatives, tegafur analogues, arabinopyranonucleosides of uracil, glucopyranonucleosides of uracil, liposidomycins, caprazamycins or tunicamycins, tritylated uridine analogues, nitro or cyano derivatives of uracil, uracil-quinazolinone, uracil-indole or uracil-isatin-conjugates, pyrimidinophanes containing one or two uracil units and nitrogen atoms in bridging polymethylene chains etc. In this review is also discussed synthesis and biological activity of fused uracils having uracil ring annulated with other heterocyclic ring.

Pharmacogenetics in clinical practice: considerations for testing

Pharmacogenetics is a rapidly evolving field that will undoubtedly lead to the development of pharmacogenetic tests. Such tests will need to be assimilated into healthcare systems, but represent a further call on scarce healthcare resources. Therefore, in order for a pharmacogenetic test to fulfill its potential beyond the laboratory and into the clinical environment, it must prove itself on a wide range of multifaceted criteria. The test must have proven and reproducible analytical and clinical validity, and stand up to critical appraisal of clinical utility and cost-effectiveness. Pharmacogenetic testing can be considered to be a form of screening, and the experience that has been gained to date in evaluating other forms of screening tests may prove beneficial in evaluating pharmacogenetic technology. It is essential that the goals of pharmacogenetic testing are defined as early as possible to ensure that appropriate studies can be designed to provide the evidence base, and thereby enable appropriate evaluation of the technology by clinicians and healthcare administrators for incorporation into clinical practice. This review focuses on issues that will need to be considered in the scientific assessment of pharmacogenetic testing.

Mixed ligand complexation of some transition metal ions in solution and solid state: spectral characterization, antimicrobial, antioxidant, DNA cleavage activities and molecular modeling

Equilibrium studies of Ni(II), Cu(II) and Zn(II) mixed ligand complexes involving a primary ligand 5-fluorouracil (5-FU; A) and imidazoles viz., imidazole (him), benzimidazole (bim), histamine (hist) and L-histidine (his) as co-ligands(B) were carried out pH-metrically in aqueous medium at 310±0.1K with I=0.15 M (NaClO4). In solution state, the stoichiometry of MABH, MAB and MAB2 species have been detected. The primary ligand(A) binds the central M(II) ions in a monodentate manner whereas him, bim, hist and his co-ligands(B) bind in mono, mono, bi and tridentate modes respectively. The calculated ΔlogK, logX and logX' values indicate higher stability of the mixed ligand complexes in comparison to binary species. Stability of the mixed ligand complex equilibria follows the Irving-Williams order of stability. In vitro biological evaluations of the free ligand(A) and their metal complexes by well diffusion technique show moderate activities against common bacterial and fungal strains. Oxidative cleavage interaction of ligand(A) and their copper complexes with CT DNA is also studied by gel electrophoresis method in the presence of oxidant. In vitro antioxidant evaluations of the primary ligand(A), CuA and CuAB complexes by DPPH free radical scavenging model were carried out. In solid, the MAB type of M(II)5-FU(A)his(B) complexes were isolated and characterized by various physico-chemical and spectral techniques. Both the magnetic susceptibility and electronic spectral analysis suggest distorted octahedral geometry. Thermal studies on the synthesized mixed ligand complexes show loss of coordinated water molecule in the first step followed by decomposition of the organic residues subsequently. XRD and SEM analysis suggest that the microcrystalline nature and homogeneous morphology of MAB complexes. Further, the 3D molecular modeling and analysis for the mixed ligand MAB complexes have also been carried out.

Pharmacogenetic Biomarkers as Tools for Pharmacoepidemiology of Severe Adverse Drug Reactions

Preclinical Research

The development of new genomic technologies has led to an exponential increase in the number of biomarkers for drug safety and efficacy. Pharmacogenomics has the potential to impact clinically relevant outcomes in drug dosing, efficacy, toxicity, and prediction of adverse drug reactions (ADRs). Genotype‐based prescribing is anticipated to improve the overall efficacy rates and minimize ADRs, making personalized medicine a reality. Genome‐wide association studies have been increasingly applied to pharmacogenetics. Severe ADRs are a major issue for drug therapy because they can cause serious disorders and can be life threatening. For severe ADRs, significant associations have been reported for drug‐induced liver injury, statin‐induced myopathy, increased risk of hemorrhagic complications of anticoagulant use, drug‐induced torsade de pointes, drug‐induced long QT, and severe cutaneous ADRs. This review summarizes the current position concerning the clinical and pharmacoepidemiological relevance of pharmacogenetic biomarkers in ADR prediction and prevention, with an emphasis on genetic risk factors and biomarkers for three specific severe ADRs.

Synthesis and antitumor activity of conjugates of 5-Fluorouracil and emodin

A series of conjugates of 5-Fluorouracil (5-FU) and emodin were synthesized by coupling trimethyl emodin with N(1), N(3) dialkylated 5-FU. The 5-FU moiety contained various substituents at the N(3)-position were linked to the 2-position of trimethyl emodin via a methylene linkage. Their cytotoxicity against three cancer cell lines and one noncancerous cell were studied. The results revealed that some of conjugates exhibited better or comparable in vitro antitumor activity to 5-FU and emodin and low toxicity in the normal cell. The structure-activity relationship study showed N(3)-aromatic substituent was important for their cytotoxic activity.

Fluoroquinolone efflux mediated by ABC transporters

Quinolones and fluoroquinolones are broad spectrum bactericidal drugs, which are widely used in both human and veterinary medicine. These drugs can quite easily enter cells and are often used to treat intracellular pathogens. Some fluoroquinolones have been reported to undergo efflux, which could explain their low bioavailability. There is a growing need to understand resistance mechanisms to quinolones, involving for instance mutations or the action of efflux pumps. Several members of the ATP-binding cassette (ABC) drug efflux transporter family (MDR, MRP, ABCG2) significantly affect the pharmacokinetic disposition of quinolones. Active secretory mechanisms common to all fluoroquinolones have been suggested, as well as competition between fluoroquinolones at transporter sites. For grepafloxacin and its metabolites, MRP2 has been demonstrated to mediate biliary excretion. However, MDR1 is responsible for grepafloxacin intestinal secretion. Recently it has been shown that ciprofloxacin and enrofloxacin are efficiently transported ABCG2 substrates which are actively secreted into milk. It appears that multiple ABC transporters contribute to the overall secretion of fluoroquinolones. The objective of this work is to review the recent advances in insights into ABC transporters and their effects on fluoroquinolone disposition and resistance including data on drug secretion into milk.

Palladium-Catalyzed Carbonylative Annulation Reaction of 2-(1-Alkynyl)benzenamines: Selective Synthesis of 3-(Halomethylene)indolin-2-ones

A novel and selective palladium-catalyzed carbonylative annulation process for the synthesis of 3-(halomethylene)indolin-2-ones was demonstrated. In the presence of PdX2 and CuX2, 3-(halomethylene)indolin-2-ones were selectively obtained from the carbonylative annulations of 2-(1-alkynyl)benzenamines with CO in moderate to good yields.

Toward individualized treatment: prediction of anticancer drug disposition and toxicity with pharmacogenetics

A great deal of effort has been spent in defining the pharmacokinetics and pharmacodynamics of investigational and registered anticancer agents. Often, there is a marked variability in drug handling between individual patients, which contributes to variability in the pharmacodynamic effects of a given dose of a drug. A combination of physiological variables, genetic characteristics (pharmacogenetics) and environmental factors is known to alter the relationship between the absolute dose and the concentration-time profile in plasma. A variety of strategies are now being evaluated in patients with cancer to improve the therapeutic index of anticancer drugs by implementation of pharmacogenetic imprinting through genotyping or phenotyping individual patients. The efforts have mainly focused on variants in genes encoding the drug-metabolizing enzymes thiopurine S-methyltransferase, dihydropyrimidine dehydrogenase, members of the cytochrome P450 family, including the CYP2B, 2C, 2D and 3A subfamilies, members of the UDP glucuronosyltransferase family, as well as the ATP-binding cassette transporters ABCB1 (P-glycoprotein) and ABCG2 (breast cancer resistance protein). Several of these genotyping strategies have been shown to have substantial impact on therapeutic outcome and should eventually lead to improved anticancer chemotherapy.

Variants in the SLCO1B3 Gene: Interethnic Distribution and Association with Paclitaxel Pharmacokinetics

To explore retrospectively the relationships between paclitaxel pharmacokinetics and three known, non-synonymous single-nucleotide polymorphisms (SNPs) in SLCO1B3, the gene encoding organic anion transporting polypeptide (OATP)1B3. Accumulation of [(3)H]paclitaxel was studied in Xenopus laevis oocytes injected with cRNA of Oatp1b2, OATP1A2, OATP1B1, OATP1B3, OAT1, OAT3, OCT1, and NTCP. The 334T>G (Ser112Ala), 699G>A (Met233Ile), and 1564G>T (Gly522Cys) loci of SLCO1B3 were screened in 475 individuals from five ethnic groups and 90 European Caucasian cancer patients treated with paclitaxel. Only OATP1B3 was capable of transporting paclitaxel to a significant extent (P=0.003). The 334T>G and 699G>A SNPs were less common in the African-American and Ghanaian populations (P<0.000001). Paclitaxel pharmacokinetics were not associated with the studied SNPs or haplotypes (P>0.3). The studied SNPs in SLCO1B3 appear to play a limited role in the disposition of paclitaxel, although their clinical significance in other ethnic populations remains to be investigated.

Role of the liver-specific transporters OATP1B1 and OATP1B3 in governing drug elimination

Members of the organic anion transporting polypeptide (OATP) family are responsible for the cellular uptake of a broad range of endogenous compounds and xenobiotics in multiple tissues. This review focuses on OATP1B1 and -1B3, which are specifically expressed in the liver and considered to be of particular importance for hepatic drug elimination and drug pharmacokinetics. Recent literature has indicated that inhibition of these transporters may result in drug-drug interactions. Furthermore, genetic polymorphisms in the genes encoding OATP1B1 and -1B3 have been described that increase or decrease transport in vitro and in vivo. Alteration of transporter function by either of these mechanisms may contribute to interindividual variability in drug disposition and response. In this review an update of this rapidly emerging field is provided.

Taxane pharmacogenetics

The taxanes paclitaxel and docetaxel exert their anticancer activity by stabilizing microtubules during cell division. There is significant interindividual variability in response and toxicity between paclitaxel and docetaxel. Interpatient variability also exists for response and toxicity from each drug. Variability within genes involved in paclitaxel and/or docetaxel metabolism and transport exists. However, to date there is little evidence to suggest useful markers for the selection of individualized therapy. Epigenetic regulation of taxane pathway genes may play a large role in explaining the variability in toxicity and response.

Genotyping and phenotyping cytochrome P450: Perspectives for cancer treatment

As most anticancer agents display a narrow therapeutic window, patients may be susceptible to (extreme) toxicities or a lowered therapeutic outcome if not dosed adequately. Therefore, it is important to study factors which affect the pharmacokinetics and pharmacodynamics of these drugs. Among these, the contribution of genetic variation in drug metabolizing enzymes on the metabolism of anticancer agents has gathered interest, as it may potentially explain a substantial amount of interpatient variability in pharmacokinetics and drug response. Cytochrome P450, an oxidative enzyme-system involved in the breakdown of many drugs, is currently studied for correlations between genetic polymorphisms and anticancer drug metabolism. Also, alternative ways to predict the expression of cytochrome P450 have been developed (phenotyping measures) which may have additional value in creating a lowered interpatient variability, to minimize side-effects and maximize therapeutic efficacy.

TYMS and DPYD polymorphisms in a Turkish population

OBJECTIVE

The thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) enzymes affect the outcome of 5-fluorouracil (5-FU)-based chemotherapy. Genetic polymorphisms of the thymidylate synthase (TYMS) and dihydropyrimidine dehydrogenase (DPYD) genes that may affect chemotherapy are described. The aim of this study was to determine the frequencies of TYMS and DPYD polymorphisms in healthy Turkish individuals.

METHODS

Genotyping analyses of the promoter enhancer region of TYMS (TSER) and the exon 14-skipping mutation of the DPYD (DPYD*2A) genes were conducted in 250 unrelated, healthy volunteers from the central region of Turkey using a PCR-based assay.

RESULTS

The distribution of the TSER*2/*2, *2/*3 and *3/*3 genotypes were 17.6%, 48.8%, and 33.6%, respectively. The frequencies of the TSER*2 and *3 alleles in the Turkish population were 0.42 and 0.58, respectively. No individuals with the variant DPYD*2A allele were identified in the study group.

CONCLUSION

The frequency of the TSER*3 allele among members of the Turkish population was similar to frequencies observed in other Caucasian populations but was lower than those found in Japanese and Chinese populations.

Association of CYP2C8, CYP3A4, CYP3A5, and ABCB1 polymorphisms with the pharmacokinetics of paclitaxel

PURPOSE

To retrospectively evaluate the effects of six known allelic variants in the CYP2C8, CYP3A4, CYP3A5, and ABCB1 genes on the pharmacokinetics of the anticancer agent paclitaxel (Taxol).

EXPERIMENTAL DESIGN

A cohort of 97 Caucasian patients with cancer (median age, 57 years) received paclitaxel as an i.v. infusion (dose range, 80-225 mg/m(2)). Genomic DNA was analyzed using PCR RFLP or using Pyrosequencing. Pharmacokinetic variables for unbound paclitaxel were estimated using nonlinear mixed effect modeling. The effects of genotypes on typical value of clearance were evaluated with the likelihood ratio test within NONMEM. In addition, relations between genotype and individual pharmacokinetic variable estimates were evaluated with one-way ANOVA.

RESULTS

The allele frequencies for the CYP2C8*2, CYP2C8*3, CYP2C8*4, CYP3A4*3, CYP3A5*3C, and ABCB1 3435C>T variants were 0.7%, 9.2%, 2.1%, 0.5%, 93.2%, and 47.1%, respectively, and all were in Hardy-Weinberg equilibrium. The population typical value of clearance of unbound paclitaxel was 301 L/h (individual clearance range, 83.7-1055 L/h). The CYP2C8 or CYP3A4/5 genotypes were not statistically significantly associated with unbound clearance of paclitaxel. Likewise, no statistically significant association was observed between the ABCB1 3435C>T variant and any of the studied pharmacokinetic variables.

CONCLUSIONS

This study indicates that the presently evaluated variant alleles in the CYP2C8, CYP3A4, CYP3A5, and ABCB1 genes do not explain the substantial interindividual variability in paclitaxel pharmacokinetics.

Genetic diversity and new therapeutic concepts

The differences in medicinal drug responses among individuals had been known for quite some time. Some patients exhibit a life-threatening adverse reaction while others fail to show an expected therapeutic effect. Intermediate responses between the above two extreme cases are also known. In fact, it has been recently reported that approximately 100,000 deaths and more than 2 million hospitalizations annually in the United States are due to properly prescribed medications. This interindividual variability could be due in part to genetically determined characteristics of target genes or drug metabolizing enzymes. This has now been substantiated by a variety of studies. We know that "one size fits all" is not correct. Therefore, the application of pharmacogenetic concepts to clinical practice is an excellent goal in the postgenomic era. The successful completion of the human genome project provided necessary molecular tools, such as high-throughput SNP genotyping, HapMap, and microarray, that can be applied to develop proper therapeutic options for individuals. Recently, there have been considerable scientific, corporate, and policy interest in pharmacotherapy. However, identification of causal variations in a target gene is only a starting point, and the progress in this rapidly developing field is slower than expected. One major drawback could be due to the multigene determinant of drug response that requires a genome-wide screening. Additionally, application of pharmacogenetic knowledge into clinical practice requires a high level of accuracy, precision (risk/benefit ratio), and strict regulations. This is because the pharmacogenetic approach raises several ethical, moral, and legal questions. It is also necessary that both health professionals and the general public must be urgently educated. Despite these limitations, translation of pharmacogenomic data into clinical practice would certainly provide better opportunities to increase the safety and efficacy of medicine in the future.