Trifluorothymidine

TAS-102 in gastric cancer: Development and perspectives of a new biochemically modulated fluroropyrimidine drug combination

TAS-102 is a preconstituted drug combination comprising an oral fluoropyrimidine (trifluridine, TFT) and a potent inhibitor of thymidine phosphorylase (tipiracil hydrochloride, TPI). TFT/TPI has recently received Food and Drug Administration (FDA) approval also for the treatment of gastric cancer after at least two lines of chemotherapy. The approval was based on a large phase 3 trial (TAGS), in which TAS-102 showed a 31 % decrease in the risk of death compared with placebo. Here, we review the pharmacological properties, clinical development and potential future directions of TAS-102 in gastric cancer.

Interaction of 5-Methoxymethyl-2′-Deoxyuridine Triphosphate with DNA Polymerases: Effects of the 5-Substituent and Comparison with the Deoxycytidine Derivative

5-Methoxymethyl-2′-deoxyuridine (MMdUrd) is a selective anti-herpes agent that is dependent upon initial phosphorylation by Herpes simplex virus-induced deoxythymidine kinase. In order to determine its mechanism of action, MMdUrd was converted to the 5′-triphosphate (MMdUTP) and the nature of interaction of MMdUTP and dTTP with DNA polymerase of E. coli, HSV-1, and human α was investigated. The order of utilization of deoxyuridine analogues by bacterial and HSV-1 DNA polymerases for DNA synthesis was: dTTP > MMdUTP. In contrast, 5-methoxymethyl-2′-deoxycytidine-5′-triphosphate (MMdCTP) was a better substrate for HSV DNA polymerase compared to dCTP. MMdUTP is a competitive inhibitor of HSV-1 DNA polymerase with respect to dTTP incorporation (Ki = 2.9 × 10−6M). The IC50 values of MMdUTP for both HSV and human αDNA polymerases were 4.5 × 10 −6M. These data suggest that the selective activity of MMdUrd is due to its preferential phosphorylation by viral thymidine kinase and not at the DNA polymerase level. These results may also account for the difference in anti-HSV activity between MMdUrd and its deoxycytidine analogue.

A novel antimetabolite: TAS-102 for metastatic colorectal cancer

TAS-102 is a new oral anti-tumor drug, composed of a thymidine-based nucleoside analog (trifluridine: FTD) and a thymidine phosphorylase inhibitor (tipiracil hydrochloride: TPI). TAS-102 has been shown to significantly improve overall survival and progression-free survival in patients with refractory metastatic colorectal cancer (mCRC) in placebo-controlled randomized phase II and III trials. The current review summarizes mechanisms of action, pharmacokinetics/dynamics and preclinical and clinical data of TAS-102 in colorectal cancer. TAS-102 is a new salvage-line treatment option for patients with mCRC. TAS-102 is well tolerated and has great potential in future clinical drug combination therapies.

Chapter 3 Antiviral drugs: general considerations

The development of an antiviral drug as well as of other drugs is a long process. In most programmes the screening and evaluation start using inhibition of virus multiplication in cell cultures, but in some instances the screening starts in animal models of different viral diseases. In these cases, the mechanism of action has to be analyzed after the in vivo effect has been found. It is not possible to specify precisely the time and resources required in a newly started project to find a compound active against a virus infection but 5-10 years is a reasonable estimation. For some viruses such as herpesviruses, where a number of active inhibitors are already known, the task is simpler than it is to find inhibitors of a virus such as influenza against which only a few active inhibitors have been reported. Evaluation of clinical efficacy in humans is a large and difficult part of the development of an antiviral drug. The number of uncontrolled clinical studies claiming efficacy of different drugs against viral diseases is depressingly large. It is essential to perform double-blind, placebo-controlled and statistically well evaluated studies to be able to judge the clinical efficacy of an antiviral drug. As the knowledge of the detailed natural history and molecular biology of viral diseases and viruses themselves increases, one will obviously have better opportunities to find new drugs. Methods such as X-ray diffraction measurement and NMR determinations will probably lead to a detailed understanding of the structures and interactions taking place at the active site of viral enzymes and their cellular counterparts.

Trifluoromethylation of Alkenyl Bromides and Iodides (Including 5-Iodouracils) with (CF3)2Hgand Cu (“Trifluoromethylcopper”)1

Bromo- and iodoalkenes undergo trifluoromethylation efficiently in DMA with "CF3Cu" generated from (CF3)2Hg and Cu. Variable stereochemical inversion is observed with substrates having a gem-carbonyl group. Substrates having gem-hydrogen, -alkyl, or -alkenyl groups give products with stereochemical retention.

New acyclonucleosides: synthesis and anti-HIV activity

The synthesis of new acyclic nucleosides is described. These syntheses were accomplished by various methods: glycosylation, selective or total deprotection, oxidation/reduction, chlorination or azidation of hydroxyl groups. The compounds were characterized with NMR, mass and IR spectroscopy. Antiviral properties of these compounds were evaluated on HIV-1 infected cell lines.

Structure-activity relationships and conformational features of antiherpetic pyrimidine and purine nucleoside analogues. A review

A rational approach to the design of antiherpetic nucleoside analogues is based in part on the broad specificity of virus-coded thymidine kinases. Herpes virus thymidine kinase 'activates' many 5-substituted 2'-deoxyuridines, analogues of thymidine (e.g., idoxuridine, trifluridine, edoxudine, brivudine), 5-substituted arabinofuranosyluracil derivatives (e.g., 5-Et-Ara-U, BV-Ara-U, Cl-Ara-U), acyclonucleosides of guanine (e.g., aciclovir, ganciclovir, penciclovir), and purine nucleosides with the pentafuranosyl ring replaced by a cyclobutane ring (e.g., cyclobut-G, cyclobut-A). Activation involves selective, and frequently regiospecific, phosphorylation of these analogues to the 5'-monophosphates. These are further phosphorylated by cellular enzymes to the 5'-triphosphates, which are usually competitive inhibitors of the viral-coded DNA polymerases. Some analogues are also incorporated into viral, and to a lesser extent cellular, DNA. A recent, unusual, exception is human cytomegalovirus, which does not code for a thymidine kinase, but for a protein with the sequence characteristics of protein kinase and which phosphorylates ganciclovir to its 5'-monophosphate. The interaction of the analogues with cellular catabolic enzymes such as uridine and thymidine nucleoside phosphorylases is also discussed, as is the relationship between physicochemical properties (configuration, conformation, electronic and hydrophobic parameters) and antiviral activities, with particular reference to those drugs that are licensed, or under consideration, for clinical use.

Intracellular localization of drugs in cultured tumor cells by ion microscopy and image processing

Several drugs, containing a halogen atom, F or Br, that are being used in antiviral or anticancer therapy, were studied for their localization in cultured cells by ion microanalysis. The association allows to reduce the exposure time to define the intracellular localization of the studied element. The topography of the cells is given by the image of the polyatomic ion 26CN-. The image of the distribution of 81Br- or 19F-, coded in another color scale, can be superimposed, giving a polychromic image of the cell, thus showing the intracellular localization of the compound. MCF-7 tumor cells were cultured in the presence of pyrimidine derivatives. 5-Bromo-2'-deoxyuridine (BUdR) and 5-trifluorothymidine (F3TdR) were localized in the nucleus, 5-fluoro-2'-deoxyuridine (FUdR) in the nucleus and only in some nucleoli. The method is simple and rapid, as compared with techniques using radiolabeled compounds, or with immunocytochemical techniques. It is possible to observe two different compounds in the same cell. It could be applied to other compounds containing a halogen atom.

Chemotherapy of herpesvirus infections

The following paper is intended to review those nucleoside analogs currently licensed for the treatment of herpetic diseases. Potentially efficacious congeners also will be considered. The mechanism of action, preclinical and clinical efficacy, and the problems associated with the use of each nucleoside analog will be described.

Antiviral therapy

Antiviral therapy is gradually coming of age. More agents including interferons as well as combinations of agents can be anticipated in the marketplace. Five antivirals are now approved for use, and there are at least seven that have a strong chance of becoming available.

Analysis of 5-fluoro-2'-deoxycytidine and 5-trifluoromethyl-2'-deoxycytidine and their related antimetabolites by high-performance liquid chromatography

An isocratic, ion-paired, reversed-phase high-performance liquid chromatography technique for the quantitative determination of 5-fluoro-2'-deoxycytidine (FdCyd) and 5-trifluoromethyl-2'-deoxycytidine (F3methyldCyd) and their related antimetabolites is described. Extraction and purification of these compounds from DNA, RNA, and free pools is reviewed diagrammatically. Total analysis time including quantitation of DNA and RNA primary constituents is 45 min. Average combined recoveries for prodrugs and antimetabolites is above 90% with standard deviations of 0.07 and 0.58 and average precisions of 5.51 and 8.30% for FdCyd and F3methyldCyd, respectively. Average coefficients of variation were 3.8 +/- 0.5% for FdCyd and 7.7 +/- 1.0% for F3methyldCyd. Limits of detection were approximately 1 pmol for unlabelled prodrugs and antimetabolites. FdCyd, when generally tritiated with a specific activity of 18 Ci/mmol, was detected in the 5 X 10(-15)-20 X 10(-15) mol (fmol) range depending on sample condition.

Comparison of the mutagenic activity of 5-hydroxymethyldeoxyuridine with 5-substituted 2'-deoxyuridine analogs in the Ames Salmonella/microsome test

4 antiviral drugs 5-hydroxymethyldeoxyuridine (HMUdR), 5-trifluorothymidine (F3TdR), 5-methoxymethyldeoxyuridine (MMUdR) and 5-ethyldeoxyuridine (EtUdR) have been evaluated for mutagenic activity in the Ames Salmonella/microsome test. The antimetabolites F3TdR and HMUdR were mutagenic in a dose-dependent manner in strain TA100. F3TdR also was mutagenic in strain TA1535. Rat-liver post-mitochondrial supernatant (S9) was not required for mutagenicity.

Antiviral chemotherapy and chemoprophylaxis

Antiviral compounds have been developed for use in chemoprophylaxis and chemotherapy of a variety of infections in humans, including those caused by influenza viruses, respiratory syncytial virus, and herpesviruses. The efficacy of several of these compounds has been demonstrated in rigorously controlled trials. Advances in molecular virology have led to the identification of biochemically defined, virus-specific functions that serve as appropriate targets for the future development of antiviral compounds. Clinical investigators and practicing physicians are now confronting questions previously raised with the use of antibacterial antibiotics. These questions concern appropriate routes of administration for antiviral compounds, optimal dosage regimens, risks of long-term prophylaxis, and the emergence of resistant organisms.

Combination chemotherapy: interaction of 5-methoxymethyldeoxyuridine with trifluorothymidine, phosphonoformate and acycloguanosine against herpes simplex viruses

Methoxymethyldeoxyuridine (MMUdR) when used in combination with either trifluorothymidine (F3TdR) or phosphonoformate (PFA) showed synergistic activity against herpes simplex virus type 1 and type 2 (HSV-1 and HSV-2) in vitro, whereas MMUdR and acycloguanosine (ACG) combination was antagonistic against herpes viruses. HSV-1 mutants resistant to ACG, arabinofuranosyladenine (Ara-A), MMUdR or PFA were isolated. Drug-resistant HSV-1 virus mutants were analyzed for cross sensitivity to ACG, Ara-A, F3TdR, MMUdR, MMUdR-5'-monophosphate (MMUdR-MP) and PFA. The Ara-A-resistant (Ara-AR) virus exhibited 3-fold resistance to MMUdR-MP (ID50 = 105 microM). The ACG-resistant (ACGR) mutant was 160-fold less sensitive to MMUdR (ID50 greater than 1138 microM). The MMUdR-resistant (MMUdRR) mutant remained sensitive to all other antiviral drugs in vitro. Ara-A provided protection against HSV-1 encephalitis in immunosuppressed mice inoculated with a low dose (200 PFU/mouse) of MMUdRR virus or wild-type HSV-1. F3TdR decreased incorporation of tritiated deoxyuridine [( 3H]UdR) in RK-13 cells by 50% at 0.068 microM. Under similar conditions, MMUdR (up to 600 microM) and PFA (up to 208 microM) were without effect on incorporation of [3H]UdR into DNA. In combination chemotherapy experiments, MMUdR (up to 300 microM) used along with F3TdR (up to 1.08 microM) neither decreased nor enhanced cytotoxicity of F3TdR as measured by incorporation of [3H]UdR into cellular DNA. Similarly, MMUdR (up to 300 microM) in combination with PFA (up to 166 microM) was nontoxic to host cells.

Oncogenic transformation of C3H/10T1/2 Cl 8 mouse embryo fibroblasts by inhibitors of nucleotide metabolism

Morphological or oncogenic transformation of mouse embryo, C3H/10T1/2 Cl 8 fibroblasts was induced by methotrexate, 5-fluorouracil and 5-fluorodeoxyuridine. It is known that these compounds cause inhibition of thymidylate synthetase and, hence, depletion of deoxythymidine triphosphate (dTTP) and an increased ratio of deoxycytidine triphosphate (dCTP) to dTTP in the deoxyribonucleotide pools that are used for DNA synthesis in mammalian cells. This ratio is, in effect, increased by treating mammalian cells with arabinosyl cytosine and 5-azacytidine, which are converted into analogs of dCTP in mammalian cells and also induce oncogenic transformation of C3H/10T1/2 cells. By contrast, trifluorothymidine, 5-bromodeoxyuridine and 5-iododeoxyuridine, which are analogs of thymidine that in effect reduce the dCTP:dTTP ratio, did not induce oncogenic transformation. Moreover, thymidine was selectively lethal to tumorigenic C3H/10T1/2 cells and inhibited oncogenic transformation in cells treated with 5-fluorodeoxyuridine. These observations suggest that treatments that effectively increase the dCTP:dTTP ratio in mammalian cells facilitate oncogenic transformation of C3H/10T1/2 cells, whereas treatments that have the effect of decreasing this ratio inhibit transformation. However, dCyd did not induce oncogenic transformation of C3H/10T1/2 cells, although it has been shown to increase the dCTP:dTTP ratio in mammalian cells. Thus, increasing this ratio may not be sufficient to cause the transformation.

Physical and biological consequences of incorporation of antiviral agents into virus DNA

The molecular basis for the antiviral activity is discussed for a variety of nucleoside compounds approved for clinical use in the U.S.A. (5-iodo-2'-deoxyuridine, 5-trifluoromethyl-2'-deoxyuridine, 9-beta-D-arabinofuranosyladenine, 9-(2-hydroxyethoxymethyl)guanine), or in clinical trial (E-5-(2-bromovinyl)-2'-deoxyuridine, 1-(2-deoxy-2-fluoro-beta-D-arabinosyl)-5-iodocytosine, 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide), or of specific interest to our laboratory (5-iodo-5'-amino-2',5'-dideoxyuridine, 5'-amino-5'-deoxythymidine). The consequence of incorporation of idoxuridine, the 5'-amino analog of thymidine or the 5'-amino analog of idoxuridine into the DNA of herpes simplex virus type 1 on transcription and translation is emphasized.

Effect of CP-20,961 on genital herpes in guinea pigs

CP-20,961 (N,N-dioctadecyl-N',N'-bis(2-hydroxyethyl)propanediamine) has been reported to be an interferon inducer, an adjuvant and a macrophage activator. In the present study, this compound was used therapeutically and prophylactically to treat genital herpes simplex virus type 2 (HSV-2) infections in guinea pigs. A significant decrease in the incidence of clinical lesions (P less than 0.05) was observed in animals treated intravaginally with 20 mg CP-20,961 (two doses each containing 10 mg) prior to infection. A single dose of 5 mg CP-20,961 reduced the severity of clinical lesions and inhibited virus shedding from the guinea pig vagina. Preliminary findings indicate that CP-20,961 is a potent agent for prevention of genital herpes infection.

Interaction of polymerases with 2'-deoxyuridine-5'-triphosphate spin-labeled at the 5-position

2'-Deoxyuridine-5'-triphosphate spin-labeled at the 5-position with N-[1-oxyl-2,2,6,6-tetramethyl-4-piperidinyl]-O- was found to be an inhibitor of some DNA and RNA polymerases including avian myeloblastosis virus reverse transcriptase. Furthermore, the spin-labeled nucleotide was found to be incorporated internally into polydeoxythymidylic acid via reverse transcriptase to an extent of 1.0 spin-labeled base per 10(3) bases. The incorporation, monitored by electron spin resonance, is analogous to some other nucleotide inhibitors of polymerases, and the results indicate that it may be feasible to obtain sequence specific, spin-labeled DNA, enzymatically.

Different in vitro effects of dual combinations of anti-herpes simplex virus compounds

Five promising antivirals have been tested individually and in pairs on herpes simplex virus (HSV) types 1 (Strain F) and 2 (Strain G) in Vero cells. These are: 9-(2-hydroxyethoxymethyl)guanine (acyclovir, ACV), 9-beta-D-arabinofuranosyladenine (ara-A), 5-trifluorothymidine (TFT), E-5-(2-bromovinyl)-2'-deoxyuridine (BVDU), and phosphonoformate (PFA). Various types of interactions depending on virus type were observed: synergistic [ara-A/TFT; ara-A/BVDU (G); BVDU/PFA (F)]; additive [ACV/ara-A; ACV/TFT; ACV/BVDU; ACV/PFA (G); BVDU/TFT; PFA/ara-A; PFA/TFT]; and sub-additive [ACV/PFA (F); ara-A/BVDU (F) and BVDU/PFA (G)]. Neither antagonism nor interference was noted for any combinations.