Tesaglitazar, a novel dual peroxisome proliferator-activated receptor alpha/gamma agonist, dose-dependently improves the metabolic abnormalities associated with insulin resistance in a non-diabetic population.

AIMS/HYPOTHESIS: Insulin resistance is associated with abnormalities in lipid and glucose metabolism, which are major components of metabolic syndrome and risk factors for vascular disease. This study examined the effect of tesaglitazar (Galida), a novel, dual-acting peroxisome proliferator-activated receptor alpha/gamma agonist, on lipid and glucose metabolism in patients with evidence of insulin resistance. METHODS: A 12-week, multicentre, randomised, double-blind, placebo-controlled, dose-finding study compared the efficacy and safety of oral tesaglitazar (0.1, 0.25, 0.5 and 1.0 mg/day) and placebo in 390 non-diabetic patients with hypertriglyceridaemia (plasma triglyceride concentration >1.7 mmol/l) and abdominal obesity (waist-to-hip ratio >0.90 for men and >0.85 for women). RESULTS: A 1.0-mg dose of tesaglitazar reduced fasting triglycerides (the primary endpoint) by 37% (95% CI: -43% to -30%; p<0.0001), non-HDL-cholesterol by 15% (95% CI: -20% to -10%; p<0.0001) and NEFA by 40% (95% CI: -51% to -27%; p<0.0001), and increased HDL-cholesterol by 16% (95% CI: 8 to -24%; p<0.0001). At the end of treatment there was a dose-dependent increase in patients with pattern A LDL particle diameter (40% at baseline vs 87% at 12 weeks for tesaglitazar 1.0 mg). Tesaglitazar produced significant reductions in fasting insulin concentration (-35%; p<0.0001) and plasma glucose concentration (-0.47 mmol/l; p<0.0001). Respiratory infection and gastrointestinal symptoms were the most common adverse events and were similarly frequent in all groups. CONCLUSIONS/INTERPRETATION: Tesaglitazar was well tolerated and produced significant, dose-dependent improvements in lipid and glucose metabolism and insulin sensitivity. Tesaglitazar may have the potential to prevent vascular complications and delay progression to diabetes in these patients.

[Latent autoimmune diabetes in adults(LADA): part of the clinical spectrum of type-1 diabetes mellitus of autoimmune origin]. / A lassan kialakuló felnóttkori autoimmun diabetes (LADA): az autoimmun eredetú 1-es típusú cukorbetegség klinikai spektrumának része.

According to the most recent classification of diabetes mellitus the latent autoimmune diabetes in adults belongs to the group of type 1 autoimmune diabetes mellitus, as a slowly progressive form. It is not clear whether LADA is a distinct clinical entity or it is a part of the clinical spectrum of type 1 diabetes mellitus. The authors compare the antropologic (body mass index, waist to hip ratio), immunologic (occurrence of islet cell cytoplasmic autoantibodies and autoantibodies against glutamic acid decarboxylase and tyrosin phosphatase), genetic (HLA DR and DQ alleles known to be associated to type 1 diabetes mellitus) characteristics and occurrence of the features of the metabolic syndrome in the groups of type 1 and type 2 diabetes and LADA. 81 type 1 and 190 type 2 diabetics and 38 LADA patients were involved into the study. Freshly diagnosed type 1 diabetics served for controls of the autoantibody study: 48 patients manifested < or = 16 years of age and 89 type 1 diabetics manifested above 16 years of age. The three main diabetic groups differed in age: the average age in the type 1, type 2 and LADA groups were 37, 63 and 58 years respectively. There was no difference among the three groups in gender. The duration of the disease differed significantly between the type 2 and LADA groups (4.0 and 8.0 years respectively). In spite of the shorter duration of the disease in the LADA group, compared to the type 2 diabetics the frequency of insulin dependency was significantly higher in the LADA (81.6%) than in the type 2 group (46.7%). The BMI and WHR were comparable between the type 1 and LADA patients (average values were 23 and 0.83 in type 1 patients and 23.25 and 0.89 in LADA). The type 2 group differed significantly from type 1 and LADA (average values were 29.1 and 0.5). The concentration of glycated hemoglobin was comparable in the three groups. But there was a significant difference in HbA1c concentration between the freshly diagnosed subgroups of type 1 and LADA patients: 10.85% and 8% respectively. The fasting C-peptid levels were significantly higher in the sera of type 2 diabetics (0.75 pmol/l) compared to type 1 (0.2 pmol/l) and LADA patients (0.29 pmol/l). There was a significant difference in C-peptid concentrations between the type 1 and LADA groups, too. The insulin deficiency in LADA seemed to be not as severe as in type 1 diabetes. The serum total cholesterol and triglyceride levels were significantly higher and the HDL cholesterol concentration significantly lower in type 2 diabetics comparing to type 1 and LADA patients and there was no significant difference in this respect between the type 1 and LADA groups. The frequency of occurrence of hypertension differed no significantly between type 2 and LADA, but that of in type 1 diabetes was significantly lower than both type 2 and LADA. The occurrence of multiple autoantibodies (ICA + GADA + anti-IA2) was much more frequent in type 1 diabetes compared to LADA. In the sera of LADA patients the occurrence of ICA and GADA alone or ICA + GADA was characteristic (31.5% - 21.1% - 15.8% respectively). There was no difference between type 1 diabetes and LADA in the occurrence of the alleles of the MHC kown to be associated with type 1 diabetes. The occurrence of the haplotypes HLA DQ2/DR3 and/or DQ8/DR4 was observed in two thirds of type 1 diabetic and LADA patients. Chronic diabetic complications were observed in all of the groups and there was only a secondary connection of the complications with the type of the diabetes. Based on the results the authors suggest that LADA is a part of the clinical spectrum of type 1 diabetes of autoimmune origin.

Highly potent and selective peptide-based inhibitors of the hepatitis C virus serine protease: towards smaller inhibitors.

Structure-activity studies on a hexapeptide N-terminal cleavage product of a dodecamer substrate led to the identification of very potent and highly specific inhibitors of the HCV NS3 protease/NS4A cofactor peptide complex. The largest increase in potency was accomplished by the introduction of a (4R)-naphthalen-1-yl-4-methoxy substituent to the P2 proline. N-Terminal truncation resulted in tetrapeptides containing a C-terminal carboxylic acid, which exhibited low micromolar activity against the HCV serine protease.

[Metabolic syndrome-x at the turn of the millennium (Theoretical aspects with practical consequences)]. / Metabolikus x-szindróma az ezredfordulón. (Elméleti vonatkozások és gyakorlati teendók).

The authors give an overview on the hypothesis of the metabolic syndrome-x in accordance with insulin resistance and hyperinsulinism in triggering the development of type 2 diabetes mellitus with its clinical complexity. Dealing with the criticism of the original hypothesis, they touch the problem of protein-insufficient feeding in utero and consequences later in life. They discuss the recently emerging importance of postprandial hyperglycaemic condition, which might be even more responsible in leading to atherosclerotic lesions than the hyperinsulinism itself. Finally, they deal with the non-pharmacological intervention and drug therapy as well. A short overview of the results of the UKPDS (United Kingdom Prospective Diabetes Study) are also given, pointing out the clinical importance of correct antihyperglycaemic and antihypertensive treatment. The authors emphasise the utmost importance of early prevention in behalf of avoiding type 2 diabetes and cardiovascular complications as well.

Synthesis and biological characterization of sqbazide, a novel biotinylated photoaffinity probe for the study of the human platelet thromboxane A2 receptor.

SQBAzide, a biotinylated, azido derivative of the TXA2 receptor antagonist, SQ31,491, was synthesized and characterized. The compound specifically inhibited human platelet aggregation mediated by TXA2 receptor activation and irreversibly labeled platelet TXA2 receptors upon exposure to ultraviolet light. This probe should prove to be of significant value for the study of the receptor-ligand binding domain.

Discovery of non-peptidic P2-P3 butanediamide renin inhibitors with high oral efficacy.

A new series of non-peptidic renin inhibitors having a 2-substituted butanediamide moiety at the P2 and P3 positions has been identified. The optimized inhibitors have IC50 values of 0.8 to 1.4 nM and 2.5 to 7.6 nM in plasma renin assays at pH 6.0 and 7.4, respectively. When evaluated in the normotensive cynomolgus monkey model, two of the most potent inhibitors were orally active at a dose as low as 3 mg/kg. These potent renin inhibitors are characterized by oral bioavailabilities of 40 and 89% in the cynomolgus monkey. Inhibitor 3z (BILA 2157 BS) was selected as candidate for pre-development.

[Detection of antibodies against pancreatic islet cells in clinical practice]. / Hasnyálmirigy-szigetsejt elleni antitestek vizsgálata a klinikai gyakorlatban.

Development of diabetes mellitus caused by pancreatic beta-cell destruction of autoimmune origin is the result of a long lasting process. The most easily examinable feature of this stage is the occurrence of the islet cell antibodies. The sera which are positive for islet cell cytoplasmic antibodies (ICA), examined by indirect immunofluorescence, contain a mixture of antibodies. The glutamic acid decarbocylase (GAD), the tyrosin phosphatase (IA2), the insulin, and the GM2-1 glycolipid can be the targets of these antibodies. One can routinely examine the ICA, the GADA, the IA2 antibodies. The detection of antibodies against insulin (IAA) and GM-2-1 glycolipid is not invented in the routine laboratory work. The aim of the authors was the evaluation of clinical significance of occurrence of islet cell antibodies: one hundred and eighteen nondiabetic children an adult human being without known diabetic first degree relatives and 366 type 1 diabetic children and adult patients served as controls. The authors evaluated the predictive value of the different islet cell antibodies to the development of type 1 diabetes mellitus in 596 nondiabetic children with type 1 diabetic first degree relatives. The authors looked for markers of beta-cell destruction among sera of 320 diabetics manifested after 30 years of age with at least half a year of non-insulin-dependency and in the sera of 68 females suffered from gestational diabetes after 0-14 years of the index pregnancy. Finally the authors report 7 cases in which the examination of islet cell antibodies helped the diagnosis and classification of diabetes mellitus. Indirect immunofluorescence method was used for the detection of ICA, radioimmunoassay for that of GADA and IA2 antibodies. There was no positive reaction for ICA and GADA in the nondiabetic population without diabetic first degree relatives. Among the freshly diagnosed type 1 diabetic children 39% were positive for only ICA, 44% for only GADA and 80% for any antibodies. Among the freshly manifested type 1 diabetic adults ICA positivity only was observed in 21%, GADA positivity only in 7.1% and 93% for any antibodies. From the 595 nondiabetic children with type 1 diabetic first degree relatives 23 were positive for ICA, from whom 5 became diabetic during a two years observation period. These diabetic children had multiplex autoantibodies besides ICA. One child from this group, who was negative for ICA became diabetic, too. Among type 2 diabetic patients 13% were positive for ICA alone, 17% were positive for GADA alone and 27% were positive for any antibodies. The insulin dependency manifested in a short time was associated with antibody positivity. Among the gestational diabetics 10 were found positive for ICA. From them, 7 were type 1 diabetics, and 3 were type 2 diabetics at the time of the detection of antibodies. The authors suggest the need of determination of islet cell antibodies in the group of nondiabetic first degree relatives of type 1 diabetic patients (ICA, GADA, IA2 and IAA), in the group of non-insulin-dependent diabetics (ICA and GADA) as a screening for later insulin dependency, and in gestational diabetes after delivery (ICA) as screening for type 1 diabetes mellitus.

[Insulin dependent (type 1) diabetes mellitus in advanced age]. / Inzulindependens (1. típusú) diabetes mellitus idöskorban.

In everyday praxis diabetes mellitus diagnosed over the age of fifty years, means generally type 2 diabetes. Authors present cases where diabetes, beginning in advanced age, showed typical classical diabetic symptoms, like polyuria, polydipsia, loss of bodyweight. Apart from these signs a rapid decompensation of carbohydrate metabolism characterises this diabetes form. The most significant features are the rapid decrease of serum immunoreactive insulin and C-peptide levels, what is characteristic for the diminishing insulin secretory capacity. The patients had to be switched to insulin therapy within maximum 6 weeks. These patients can be easily differentiated both from type 2 and from the slowly progressing type 1 subtype. We suppose that the pathomechanism of this type of diabetes differs from the classical insulin-dependent form, beginning in young age.

Peptide-based inhibitors of the hepatitis C virus serine protease.

Hexapeptide DDIVPC-OH is a competitive inhibitor of the hepatitis C virus (HCV) NS3 protease complexed with NS4A cofactor peptide. This hexapeptide corresponds to the N-terminal cleavage product of an HCV dodecapeptide substrate derived from the NS5A/5B cleavage site. Structure-activity studies on Ac-DDIVPC-OH revealed that side chains of the P4, P3 and P1 residues contribute the most to binding and that the introduction of a D-amino acid at the P5 position improves potency considerably. Furthermore, there is a strong preference for cysteine at the P1 position and conservative replacements, such as serine, are not well tolerated.

Studies on the C-terminal of hexapeptide inhibitors of the hepatitis C virus serine protease.

Replacement of the C-terminal carboxylic acid functionality of peptide inhibitors of hepatitis C virus (HCV) NS3 protease (complexed with NS4A peptide cofactor) by activated carbonyl groups does not produce any substantial increase in potency. These latter inhibitors also inhibit a variety of other serine and cysteine proteases whereas the carboxylic acids are specific. Norvaline was identified as a chemically stable replacement for the P1 residue of Ac-DDIVPC-OH which was also compatible with activated carbonyl functionalities.

Peptidomimetic inhibitors of the human cytomegalovirus protease.

The development of peptidomimetic inhibitors of the human cytomegalovirus (HCMV) protease showing sub-micromolar potency in an enzymatic assay is described. Selective substitution of the amino acid residues of these inhibitors led to the identification of tripeptide inhibitors showing improvements in inhibitor potency of 27-fold relative to inhibitor 39 based upon the natural tetrapeptide sequence. Small side chains at P1 were well tolerated by this enzyme, a fact consistent with previous observations. The S2 binding pocket of HCMV protease was very permissive, tolerating lipophilic and basic residues. The substitutions tried at P3 indicated that a small increase in inhibitor potency could be realized by the substitution of a tert-leucine residue for valine. Substitutions of the N-terminal capping group did not significantly affect inhibitor potency. Pentafluoroethyl ketones, alpha,alpha-difluoro-beta-keto amides, phosphonates and alpha-keto amides were all effective substitutions for the activated carbonyl component and gave inhibitors which were selective for HCMV protease. A slight increase in potency was observed by lengthening the P1' residue of the alpha-keto amide series of inhibitors. This position also tolerated a variety of groups making this a potential site for future modifications which could modulate the physicochemical properties of these molecules.

Synthesis of O-methylsulfonyl derivatives of D-glucose as potential alkylating agents for targeted drug delivery to the brain. Evaluation of their interaction with the human erythrocyte GLUT1 hexose transporter.

In order to obtain hydrophilic analogues of 1,4-dimethylsulfonyloxybutane (busulfan) with enhanced selectivity and improved brain penetration, we have synthesized 6-O-methylsulfonyl-D-glucose, 3-O-methylsulfonyl-D-glucose, 3,6-di-O-methylsulfonyl-D-glucose, 4-O-methylsulfonyl-D-glucose, and 4,6-di-O-methylsulfonyl-D-glucose, and we have studied their interactions with the human erythrocyte GLUT1 hexose transport system. Mesylation of OH-4 and OH-6 of glucose resulted in a slightly diminished affinity for the GLUT1 glucose transporter, whereas mesylation of OH-3 led to complete loss of affinity.

[The value of certain parameters in the diagnosis and detection of metabolic X syndrome]. / Az egyes vizsgálati paraméterek értéke a metabolikus X-szindróma diagnózisában és felkutatásában.

Authors summarise their 5-year long experiences on 343 patients about diagnostic methods of metabolic syndrome X and offer a simple possibility for screening of the jeopardized individuals. In a group of patients with hypertension and central obesity (group I: with 2 insulin resistant condition), 229 (89%) out of 255 cases met the basic criteria of the syndrome X which were hypertension, central obesity and high insulin levels for the corresponding blood sugar levels during oral glucose tolerance test (probable insulin resistance). Dyslipidemia was missing in 20% of these people. Hyperinsulinism occurred in 85%, glucose intolerance in 53%, presumable insulin resistance in 90% of cases. Insulin resistance was characterised by late hyperinsulinism (90 and 120 min.) during oral glucose tolerance test. This was the case in people with "diabetoid" glucose responses too, suggesting an early failure of glucose tolerance and/or insulin secretion. Components of syndrome X were present with a lower frequency in 24 patients with obesity (group II), in 35 patients with hypertension (group III) and in 29 patients without obesity or hypertension (group IV), as well. According to central obesity and hypertension, syndrome X could be screened by a probability of 90%. This can be helpful in prevention of NIDDM and coronary heart disease.

Synthesis of glucose-chlorambucil derivatives and their recognition by the human GLUT1 glucose transporter.

A limitation of the use of chemotherapeutic agents against intracerebral tumors lies on their poor uptake into the central nervous system. An approach to enhance brain delivery is to design agents that are transported into the brain by one of the saturable nutrient carriers of the blood-brain barrier, the highly efficient brain and erythrocyte glucose transporter isoform GLUT1. Since the GLUT1 hexose transporter of the blood-brain barrier is also present on erythrocytes, new compounds designed to be transported by the GLUT1 transporter were studied on human erythrocytes, which represent unique, easily accessible human GLUT1 expressing cells. In this paper we describe the synthesis of four glucose-chlorambucil derivatives, namely methyl 6-O-4[bis(2-chloroethyl)amino]benzenebut anoyl-beta-D-glucopyranosi de (3), 6-O-4-[bis(2-chloroethyl)amino]benzenebu tanoyl-D-glucopyranose (6), methyl 6-[4-[bis(2-chloroethyl)amino]benzenebut anoylamido]-6-deoxy-beta-D-glucopyranoside (9) and 6-[4-[bis(2-chloroethyl)amino]benzenebut anoyl amido]-6-deoxy-D-glucopyranose (10), and the study of their interactions with the GLUT1 transporter of the human erythrocytes. All four compounds were able to inhibit [14C]glucose uptake in a concentration-dependent manner. One of them, compound 6, exhibited an approximately 160-fold higher inhibition of [14C]glucose uptake by the GLUT1 transporter than glucose itself. Compound 6 was also able to inhibit [3H]cytochalasin B binding to erythrocytes with approximately 1000-fold higher efficacy than does glucose. The inhibition of glucose uptake was entirely reversible, indicating that it was not due to alkylation of a nucleophilic group of the hexose transporter. The above results suggested specific interactions of compound 6 with the hexose transporter protein. Uptake studies of [14C]compound 6 indicated, in addition, some non-specific interactions with intact and open erythrocyte membranes: only a small amount of the bound [14C]compound 6 can be displaced by cytochalasin B. Collectively, these findings led us to conclude that the interactions of compound 6 with GLUT1 are presumably that of a non-transported inhibitor.

[Current interpretation of type 2 diabetes mellitus (NIDDM)]. / A 2. típusú cukorbetegség (NIDDM) korszerü szemlélete.

The author introduces the classification of type 2. (NIDDM) diabetes. Special focus has to be directed to the slowly progressing type 1. (IDMM) form, which is masked behind the clinical picture of type 2. (NIDDM) diabetes. He points out the difficulties of differential-diagnosis among young diabetics. He draws attention on the growing importance of impaired glucose tolerance. Typical type 2 (NIDDM) diabetics seem to be members of a widened clinical entity, where hyperglycaemia is only one of the vascular and metabolic disorders. Basis of this multimetabolic syndrome lies on insulin resistance/hyperinsulinaemia. The syndrome seems to commence far before open diabetes can be diagnosed. A targeted screening for these patients might lead to a better infarct mortality rate in Hungary.

Production of highly specific monoclonal antibodies to monensin and development of a microELISA to detect this antibiotic.

Monensin, a polyether antibiotic of molecular weight 671 Da, was converted into a hemisuccinate and covalently linked to bovine serum albumin via the mixed anhydride method. Using this immunogen, polyclonal anti-monensin antibodies were raised in rabbits and monoclonal antibodies were prepared from mice. The specificity of the anti-monensin antibodies was examined by using several structural analogues as the immunogen and by performing direct binding and competitive microELISA assays on Terasaki plates. Rabbit polyclonal antibodies had a dissociation constant (KD) of 5.5 x 10(-8) M for monensin and reacted with nigericin, an antibiotic structurally related to monensin. In contrast, a mouse monoclonal antibody, 2H8, reacted only with monensin and had a much lower KD = 3 x 10(-8) M for monensin. Monoclonal antibody 2H8 was used to develop a competitive microELISA able to detect as little as 5 ng/ml of monensin in solution which corresponds to 75 pg or 110 fmol of this hapten per Terasaki well.

[Clinical picture of slow-evolving insulin-dependent diabetes mellitus]("1 1/2")]. / A lassan kialakuló inzulin dependens diabetes mellitus ("1 1/2") klinikuma.

The authors investigated the difficulties of differential diagnosis in diabetes, beginning in young age. They analysed the case records of fifteen young diabetics. The authors pointed out, that clinical diagnosis, carried out early, has utmost importance both of theoretical and practical significance, for correct classification according to the type of diabetes determines the therapy. In building the diagnosis, the clinician needs correct anamnestical, clinical data, immunogenetic markers (ICA, HLA), and the capacity of endogenous insulin secretion as well. In three patients they have observed a long period without insulin treatment that could be classified as remission phase. In eleven cases the treatment has started with oral antidiabetic drugs, one patient has got at he very beginning insulin treatment. At present, there is only one patient, still taking oral drugs. This diabetics has an ICA positivity in high titer, but he is refusing the recommended exogenous insulin treatment. In all of their cases the amount of injected daily insulin is low (0.3-0.6 IU/body weight/24 hours). Authors state by their careful analysis, that in all of their 15 diabetics there is existing a slowly developing type I IDDM, I/b, or very recently 1 1/2 diabetes form. The so called autoimmune form--described originally by Bottazzo--could have been disclosed in all of their cases.

[Hypertension and multimetabolic syndrome]. / Hipertónia és multimetabolikus szindróma.

The occurrence of multi-metabolic syndrome was studied by authors on 31 patients with obesity of android type and hypertension. Plasma glucose and plasma insulin levels were investigated during oral glucose tolerance test, plasma lipid levels were determined, furthermore body mass index and waist/hip ratio were calculated. It was considered that in 65 percent of the cases the presence of multi-metabolic syndrome could have been proved. Dyslipidemia in 22 cases, hyperinsulinemia in 20 cases, deterioration of the carbohydrate metabolism in 14 cases could be demonstrated. The negative correlation between glucose- and insulin-responses to glucose challenge may suggest the presence of insulin resistance. No significant difference was found in metabolic parameters between men and women. The multi-metabolic syndrome is regarded by authors as a process which may lead to both type 2 diabetes mellitus and atherosclerosis. According to their appearance about two third of these patients could be screened. Authors emphasize the great significance of this problem and the importance of early diagnosis and prevention.

Plasma lipoprotein (a) concentration and phenotypes in diabetes mellitus.

Patients with Type 1 (insulin-dependent) and Type 2 (non-insulin-dependent) diabetes mellitus are at increased risk of developing atherosclerotic vascular diseases. A variety of lipoprotein abnormalities have been described as being associated with this increased risk. In this study, apo(a) isoform frequencies and lipoprotein(a) [Lp(a)] concentrations were determined in Type 1 and Type 2 diabetic patients in order to investigate a possible contribution of Lp(a) to the increased risk for atherosclerosis in diabetes. No significant differences in plasma Lp(a) concentrations were found in two ethnically different populations (Austrians from the province of Tyrol and Hungarians from Budapest) in either type of diabetes when compared to respective control groups (91 Type 1 and 112 Type 2 diabetic patients vs 202 control subjects in the Hungarian study and 44 Type 1 diabetic and 44 Type 2 diabetic vs 125 control subjects in the Austrian study). There were also no significant apo(a) isoform frequency differences between both patient groups and control subjects in the two study groups. These data, obtained from two large ethnically different populations, provide no evidence of a contribution of Lp(a) to the increased risk for atherosclerosis in diabetes.

Fatty acid conjugates of 2'-deoxy-5-fluorouridine as prodrugs for the selective delivery of 5-fluorouracil to tumor cells.

We have prepared a novel class of prodrugs by coupling 2'-deoxy-5-fluorouridine (5dFU) to oleic (18:1) and docosahexaenoic (22:6) acids, respectively. The cytotoxic activity of the drug and its conjugates (5dFU-18:1 and 5dFU-22:6) has been assayed in vitro upon HT-29, a colon carcinoma cell line of human origin. After short term (2-hr) treatments with the drugs, both fatty acid conjugates of 5dFU showed cytotoxic activity in a dose-dependent way, while 5dFU alone was devoid of toxic effects within the whole range of concentrations (10-200 microM) tested. Following long term (24- or 48-hr) incubations only a fraction of the HT-29 cell population was sensitive to 5dFU, the rest of the population being resistant even at the highest concentration tested (200 microM). In contrast, 5dFU-oleic acid and, particularly, 5dFU-docosahexaenoic acids appeared toxic for the whole population of HT-29 cells under the same experimental conditions. The considerable gain in cell toxicity and, to a lesser extent, in selectivity resulted from the conjugation since the toxic effect of the drug alone was not modified when equimolar mixtures of 5dFU and fatty acids were assayed. These results confirm a previous study on the cytotoxicity of fatty acid derivatives of chlorambucil toward malignant lymphoblastoid cells and reinforce the potential use of fatty acid conjugates as efficient anti-tumor prodrugs.