Studies on the intracellular accumulation process of methotrexate and its correlation with the key protein using an LC-MS/MS method: a novel way to realize prospective individualized medication.

High-dose methotrexate (HDMTX) combined with leucovorin (LV) is the first-line drug therapy for many kinds of malignant tumors. However, the specific treatment plans, such as dosage and duration of administration, are usually formulated according to the clinician's experience and therapeutic drug monitoring (TDM) of methotrexate in patients' plasma, which are responsible for strong individual differences of drug usage. A large number of studies have shown that methotrexate targets the inside of the cell. The key cytotoxic component is the methotrexate polyglutamates (MTXPGs) in the cell. The concentration of methotrexate in plasma does not reflect the efficacy and side effects well. Based on mass spectrometry technology, we developed and validated an accurate, sensitive, and stable method to quantify the intracellular MTX (MTXPG1) and its metabolites MTXPG2-7 simultaneously. The lower limit of quantification was 0.100 ng/ml, and the run time was only 3 min. Moreover, our team has already developed two LC-MS/MS-based methods to respectively quantify methotrexate in plasma samples and two key proteins (γ-glutamyl hydrolase [GGH] and folylpolyglutamate synthetase [FPGS]) in peripheral blood mononuclear cells (PBMC). Through these highly sensitive and accurate approaches, we have gained a deep understanding of the whole pharmacokinetic process of MTX and explored the key factors affecting the accumulation process of intracellular active components (MTXPGs). Based on this research, it is possible to find a more effective way to provide an accurate reference for clinical drug use than traditional therapeutic drug monitoring (TDM).

Association of GGH Promoter Methylation Levels with Methotrexate Concentrations in Chinese Children with Acute Lymphoblastic Leukemia.

BACKGROUND: It is known that γ-glutamyl hydrolase (GGH) is involved in the disposition of methotrexate (MTX), and GGH activity is regulated by DNA methylation in acute lymphoblastic leukemia (ALL) cells. The present study explores the methylation status of the GGH promoter in peripheral blood and its association with MTX levels and toxicities in Chinese children with ALL. METHODS: Serum MTX concentrations were determined by fluorescence polarization immunoassay. Methylation quantification and genotyping for GGH rs3758149 and rs11545078 was performed by Sequenom MassARRAY in 50 pediatric patients with ALL. RESULTS: Overall, the investigated region of the GGH promoter was in hypomethylated status. The methylation levels of cytosine phosphate guanine (CpG)_7, CpG_12, CpG_17, and CpG_20 were significantly higher in patients with B-cell ALL than other immunotypes (p<0.05). The methylation levels of CpG_13.14, CpG_17, and CpG_19 showed a significant negative correlation with MTX C24 hr (p<0.05). The methylation level of CpG_8.9 correlated significantly with MTX C42 hrs (p<0.05). The methylation level of CpG_19 was significantly lower in patients with MTX toxicities (p<0.05). CONCLUSIONS: The methylation levels of the GGH promoter might affect MTX exposure and toxicities. These findings provided reasonable explanations for the variability of MTX responses in patients with childhood ALL.

Serum protein gamma-glutamyl hydrolase, Ig gamma-3 chain C region, and haptoglobin are associated with the syndromes of pulmonary tuberculosis in traditional Chinese medicine.

BACKGROUND: Traditional Chinese Medicine (TCM) has been applied in treating tuberculosis (TB) based on the TCM syndromes with the effects of inhibiting Mycobacterium, strengthening the body immune system, and reducing the pulmonary toxicity. We used bioinformatic methods to study the clinical and pathological characteristics of pulmonary TB patients with TCM syndromes. Isobaric tags for relative and absolute quantification - coupled two dimensional liquid chromatography-tandem mass spectrometry (iTRAQ-2DLC-MS/MS) methods were applied to screen differentially expressed serum proteins. METHODS: Pulmonary TB cases were divided into four distinctive TCM syndromes: pulmonary Yin deficiency (PYD) syndrome, hyperactivity of fire due to Yin deficiency (HFYD) syndrome, deficiency of Qi and Yin (DQY) syndrome, and deficiency of Yin and Yang (DYY) syndrome. The serum samples from 214 pulmonary TB patients were collected, and the clinical and pathological data was analyzed by using iTRAQ-2DLC-MS/MS. Finally, the differentially expressed proteins were screened and tested by ELISA. Only 5 patients with DYY syndrome were recruited in 3 years, which were not enough for further research. RESULTS: The DQY cases had higher erythrocyte sedimentation rate (ESR) compared to the PYD and HFYD cases (P=0.0178). 94.44% (12 PYD, 18 HFYD, and 4 DQY before anti-TB treatment) of 36 treated TB cases were transformed to PYD accompanied with the reduction of ESR and absorption of pulmonary lesions. A total of 39 differentially expressed proteins (ratios of >1.3 or <0.75) were found among the three TCM syndromes. Proteomic studies revealed that gamma-glutamyl hydrolase (GGH), Ig gamma-3 chain C region (IGHG3), and haptoglobin (HPT) were specifically over-expressed in PYD (P<0.01), HFYD (P<0.001), and DQY cases (P<0.01), respectively. Furthermore, GGH was significantly higher in PYD cases compared to the HFYD and DQY cases (P<0.01, P<0.001, respectively), whereas IGHG3 was significantly higher in HFYD cases than PYD and DQY cases (P<0.001, P<0.01, respectively). CONCLUSIONS: The results suggest that TCM syndromes are significantly correlated with the pulmonary lesions and ESR. GGH was associated with folate metabolism in PYD cases, IGHG3 was linked to the control of Mycobacterium infection in HFYD patients, and HPT was involved in hypoxia in DQY patients. The present study provides new biological basis to understand the pathological changes and proteomic differences of TB syndromes.

Effect of serum folate status on total folate and 5-methyltetrahydrofolate in human skin.

BACKGROUND: It has been suggested that human skin color adapts to balance the need for vitamin D synthesis in comparison with the protection of DNA and folate from photodegradation. However, the folate content of human skin is unknown and may affect the effectiveness of the antifolate methotrexate for the treatment of psoriasis. OBJECTIVES: We examined whether total folate and 5-methyl-(6S)-tetrahydrofolate (5-MTHF) in human skin can be predicted by serum concentrations and whether there are differences in the proportion of 5-MTHF in dermis compared with epidermis. DESIGN: Total folate (by using a microbiological assay) and 5-MTHF (by using high-pressure liquid chromatography) were measured in fasting serum and fresh skin obtained at surgery by using a recovery validated extraction method. RESULTS: Total folate in human epidermis was shown to be low compared with in many other tissues, and dermal folate was an order-of-magnitude even lower. These concentrations were directly and linearly linked to serum folate status. Although the percentage of 5-MTHF of the total in the dermis was similar to that in other organs, it was especially high in the epidermis and increased to >65% as serum folate decreased. CONCLUSIONS: The high proportion of 5-MTHF in the epidermis, which is further emphasized in subjects with a lower (10-20-nmol/L) serum folate status, points to a special role for this form of folate in skin, perhaps as a protectant from ultraviolet-induced photosensitization reactions. 5-MTHF may also maintain methylation reactions that influence the proliferative activity. These results may help to individualize the treatment of psoriasis patients with methotrexate and folate.

Determination of total folates in infant formula and adult nutritionals by trienzyme extraction and UPLC-MS/MS Quantitation: First Action 2011.06.

The method for "Determination of Total Folates in Infant Formula and Adult Nutritionals by Trienzyme Extraction and UPLC-MS/MS Quantitation" was submitted to the Folate Working Group for consideration for adoption as Official First Action by AOAC INTERNATIONAL. This method uses ultra performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS) to determine the total folates in infant formulas and adult nutritionals after trienzyme digestion. Deconjugation of the various folate polyglutamates to folate monoglutamates is achieved by using rat plasma conjugase after the sample digestion with protease and a-amylase during the trienzyme digestion process. This method shows linearity of folate concentrations in the range of 10-19 100 microg/100 g. Extension of the range to cover folate concentrations of 5-2 000 000 microg/100 g can be achieved with appropriate adjustment of the sample weight and SPE cleanup loading volume. The recoveries ranged from 94.10 to 101.34%.

Glucarpidase, leucovorin, and thymidine for high-dose methotrexate-induced renal dysfunction: clinical and pharmacologic factors affecting outcome.

PURPOSE: To assess the role of the recombinant bacterial enzyme, glucarpidase (carboxypeptidase-G(2)), leucovorin, and thymidine in the management and outcome of patients with high-dose methotrexate (HDMTX) -induced nephrotoxicity. METHODS: Patients with HDMTX-induced nephrotoxicity received one to three doses of intravenous (IV) glucarpidase and leucovorin rescue. The initial cohort (n = 35) also received thymidine by continuous IV infusion. Subsequently, thymidine was restricted to patients with prolonged exposure (> 96 hours) to methotrexate (MTX) or with substantial MTX toxicity at study entry. Plasma MTX, leucovorin, and 5-methyltetrahydrofolate (5-mTHF) concentrations were measured pre- and postglucarpidase. Toxicities were monitored, and logistic regression analysis was used to assess the relationship of baseline characteristics to the development of severe toxicity and death. RESULTS: Glucarpidase was administered at a median of 96 hours (receiving thymidine, n = 44) and 66 hours (not receiving thymidine, n = 56) after the start of the MTX infusion. Plasma MTX concentrations decreased within 15 minutes of glucarpidase by 98.7%. Plasma 5-mTHF concentrations also decreased more than 98% after administration of glucarpidase. Of 12 deaths, six were directly attributed to irreversible MTX toxicity. Presence of grade 4 toxicity before administration of glucarpidase, inadequate initial increase in leucovorin dosing, and administration of glucarpidase more than 96 hours after the start of the MTX infusion were associated with development of grade 4 and 5 toxicity. CONCLUSION: Early intervention with the combination of leucovorin and glucarpidase is highly effective in patients who develop HDMTX-induced renal dysfunction. Severe toxicity and mortality occurred in patients in whom glucarpidase rescue was delayed and occurred despite thymidine administration.

Pharmacokinetics of glucarpidase in subjects with normal and impaired renal function.

Glucarpidase (formerly known as carboxypeptidase G2 or CPG2) is being evaluated for the adjunctive treatment of patients experiencing, or at risk of, methotrexate toxicity attributable to its delayed elimination. Delayed elimination of methotrexate can occur in patients with methotrexate-induced renal toxicity. In this study, glucarpidase pharmacokinetics were assessed in volunteer subjects with normal (n = 8) and severely impaired (n = 4) renal function. Each subject received a single intravenous dose of glucarpidase 50 U/kg (equivalent to 114.5 microg/kg) infused over 5 minutes. The mean maximum serum concentration (C(max)) for glucarpidase in renally impaired subjects was 2.9 microg/mL, the mean half-life (t(1/2)) was 10.0 hours, and the mean area under the serum concentration-time curve from time zero to infinity (AUC(0-infinity)) was 24.5 microg x h/mL. Similar values were found in subjects with normal renal function (mean C(max) 3.1 microg/mL, mean t(1/2) 9.0 hours, and mean AUC(0-infinity) 23.4 microg x h/mL). The results indicated little effect of renal impairment on the serum pharmacokinetics of glucarpidase.

A phase I study of single administration of antibody-directed enzyme prodrug therapy with the recombinant anti-carcinoembryonic antigen antibody-enzyme fusion protein MFECP1 and a bis-iodo phenol mustard prodrug.

PURPOSE: Antibody-directed enzyme prodrug therapy is a two-stage treatment whereby a tumor-targeted antibody-enzyme complex localizes in tumor for selective conversion of prodrug. The purpose of this study was to establish optimal variables for single administration of MFECP1, a recombinant antibody-enzyme fusion protein of an anti-carcinoembryonic antigen single-chain Fv antibody and the bacterial enzyme carboxypeptidase G2 followed by a bis-iodo phenol mustard prodrug. MFECP1 is manufactured in mannosylated form to facilitate normal tissue elimination. EXPERIMENTAL DESIGN: Pharmacokinetic, biodistribution, and tumor localization studies were used to test the hypothesis that MFECP1 localizes in tumor and clears from normal tissue via the liver. Firstly, safety of MFECP1 and a blood concentration of MFECP1 that would avoid systemic prodrug activation were tested. Secondly, dose escalation of prodrug was done. Thirdly, the dose of MFECP1 and timing of prodrug administration were optimized. RESULTS: MFECP1 was safe and well tolerated, cleared rapidly via the liver, and was less immunogenic than previously used products. Eighty-fold dose escalation from the starting dose of prodrug was carried out before dose-limiting toxicity occurred. Confirmation of the presence of enzyme in tumor and DNA interstrand cross-links indicating prodrug activation were obtained for the optimal dose and time point. A total of 28 of 31 patients was evaluable for response, the best response being a 10% reduction of tumor diameter, and 11 of 28 patients had stable disease. CONCLUSIONS: Optimal conditions for effective therapy were established. A study testing repeat treatment is currently being undertaken.

Contribution of common polymorphisms in reduced folate carrier and gamma-glutamylhydrolase to methotrexate polyglutamate levels in patients with rheumatoid arthritis.

We investigated whether polymorphisms in reduced folate carrier (SLC19A1 G80A) and gamma-glutamyl-hydrolase (GGH-401C/T) are predictive of methotrexate polyglutamate (MTXPG) levels in patients with rheumatoid arthritis treated with weekly low-dose methotrexate (MTX). Adult patients treated with MTX were enrolled in a multicentred study. Blood was drawn at the time of the visit, DNA was extracted and red blood cell (RBC) MTXPG levels (up to the penta-order of glutamation) were measured by high-performance liquid chromatography-fluorometry. A G80A polymorphism in SLC19A1 and a -401C/T promoter polymorphism in GGH were measured by polymerase chain reaction-restriction fragment length polymorphism. Multivariate linear and logistic regressions were used to predict long-chain RBC MTXPG3-5. In 226 adult patients receiving MTX (median 15 mg range: 5-25 mg) median RBC long-chain MTXPG3-5 was 56 nmol/l (range < 5-224 nmol/l). A total of 35 patients carried the SLC19A1 80AA genotype whereas 36 patients carried the GGH-401TT genotype. Weekly MTX dose, age, presence of the SLC19A1 80AA and GGH-401TT genotypes predicted independently and significantly MTXPG3-5 levels (global r = 0.38; P < 0.0001). Patients with the GGH-401TT genotype were 4.8-fold [odds ratio (OR) 95% confidence interval (CI) 1.8-13.0; P = 0.002] more likely to have MTXPG3-5 below the group median compared to patient carriers of the GGH-401CC or CT genotype. Conversely, those with the SLC19A1 80AA genotype were 3.4-fold more likely to have MTXPG3-5 levels above the group median compared to those with the SLC19A1 80GG or 80GA genotype (OR CI 95% 1.4-8.4; P = 0.007). These data demonstrate that polymorphisms in SLC19A1 and GGH affect polyglutamation of MTX.

A phase I trial of antibody directed enzyme prodrug therapy (ADEPT) in patients with advanced colorectal carcinoma or other CEA producing tumours.

Antibody-directed enzyme prodrug therapy is a targeted therapy in which a prodrug is activated selectively at the tumour site by an enzyme, which has been targeted to the tumour by an antibody (antibody-enzyme conjugate). Previous clinical trials have shown evidence of tumour response, however, the activated drug had a long half-life, which resulted in dose-limiting myelosuppression. Also, the targeting system, although giving high tumour to blood ratios of antibody-enzyme conjugate (10 000 : 1) required administration of a clearing antibody in addition to the antibody-enzyme conjugate. The purpose of this current study therefore was to attempt tumour targeting of the antibody-enzyme conjugate without the clearing antibody, and to investigate a new prodrug (bis-iodo phenol mustard, ZD2767P) whose activated form is highly potent and has a short half-life. Twenty-seven patients were treated with antibody-directed enzyme prodrug therapy using A5CP antibody-enzyme conjugate and ZD2767P prodrug, in a dose-escalating phase I trial. The maximum tolerated dose of ZD2767P was reached at 15.5 mg m(-2)x three administrations with a serum carboxypeptidase G2 level of 0.05 U ml(-1). Myelosuppression limited dose escalation. Other toxicities were mild. Patients' quality of life was not adversely affected during the trial as assessed by the measures used. There were no clinical or radiological responses seen in the study, but three patients had stable disease at day 56. Human anti-mouse antibody and human anti-carboxypeptidase G2 antibody were produced in response to the antibody enzyme conjugate (A5CP). The antibody-enzyme conjugate localisation data (carboxypeptidase G2 enzyme levels by HPLC on tumour and normal tissue samples, and gamma camera analysis of I-131 radiolabelled conjugate) are consistent with inadequate tumour localisation (median tumour: normal tissue ratios of antibody-enzyme conjugate of less than 1). A clearance system is therefore desirable with this antibody-enzyme conjugate or a more efficient targeting system is required. ZD2767P was shown to clear rapidly from the circulation and activated drug was not measurable in the blood. ZD2767P has potential for use in future antibody-directed enzyme prodrug therapy systems.

Effect of feeding on circulating micronutrient concentrations in the Burmese python (Python molurus).

Burmese pythons (Python molurus) regulate digestive performance and metabolism with the ingestion of each meal. To explore the python's postprandial responses, we monitored the concentrations of blood micronutrients and homocysteine during fasting and for 15 days after feeding. Plasma folate concentrations peaked with a 270% increase over fasting levels 3 days after feeding, whereas plasma B-12 peaked with a 66% increase within 1 day. Erythrocyte folate concentrations were highest 15 days after feeding with a 44% increase. The major plasma folate was 5-methyltetrahydrofolate during fasting and was non-5-methyltetrahydrofolate during digestion, whereas erythrocytes contained polyglutamyl forms of non-5-methyltetrahydrofolate. Plasma homocysteine concentrations peaked with a 56% increase 3 days after feeding, and were markedly greater than those of mammals. Plasma zinc and copper did not change significantly. Plasma zinc concentrations were 20 times greater than plasma copper and approximately 30 times higher than those of mammals. Pythons showed a significant postprandial decline of 25% in hematocrit. Plasma pyridoxal 5'-phosphate (coenzyme form of vitamin B-6) was not detected probably due to its tight protein binding. Most micronutrient concentrations appear to plateau 3 days after feeding, suggesting that pythons have relatively rapid homeostasis of micronutrients despite the ingestion of large meals.

[Role of bioantioxidants depression and deficiency of protease inhibitor alpha 1-antitrypsin in mechanisms activating free radical oxidation and proteolysis in chronic pancreatitis]. / Rol' depressii bioantioksidantov i defitsita ingibitora proteaz alpha1-antitripsina v mekhanizme aktivatsii svobodnoradikal'nogo okisleniia i proteoliza pri khronicheskom pankreatite.

AIM: To elucidate the reason and mechanisms of neutralization of protease inhibitors and antioxidants by proteolytic enzymes and oxidants. MATERIALS AND METHODS: The trial included 92 patients with exacerbation of chronic pancreatitis. 47 of them had chronic recurrent pancreatitis (CRP), 45 patients had chronic fibrozing pancreatitis (CFP). Measurements were made of blood catalase and ceruloplasmin (according to P. Hubl, R. Breschneider and O. Houchin, respectively), alpha1-antitrypsin (by Reiderman), schiff bases (by B. Fletcher et al.), dienic conjugates (by Z. Placer), serum acid phosphatase (by Bodansky), acid phosphatase of polynuclear cells (by R. Nartsissiv), NBT-test was made according to B. Park. RESULTS: Exacerbation of CRP was associated with enhancement of free radical lipid peroxidation (FPOL), release of proteolytic and lysosomal enzymes from acinar cells, a fall in catalase level. Catalase depression depends on the level of blood lysosomal enzymes and partially on FPOL activity. In CFP moderate activity of FPOL and trypsin is associated with normal levels of lysosomal enzymes and catalase. In both pancreatitis forms, alpha1-antitrypsin levels are low. This lowering is primary and unrelated with inflammatory process in the pancreas. A trypsin rise in both forms depends on lowering of alpha1-antitrypsin which via trypsin inhibits formation of lysosomal enzymes in polynuclear cells. Inability of protease inhibitor to block proteolytic (lysosomal) enzymes manifests in initial intraacinar activation of trypsin from trypsinogen, in inflammatory focus under polynuclear cells release of lysosomal enzymes and in proteolytic enzymes release from the affected acinar structures. CONCLUSION: Lack of alpha1-antitrypsin--protease inhibitor--and depression of antioxidant catalase are main and intermediate elements in activation of mechanisms of proteolytic aggression and FPOL.

Antibody-directed enzyme prodrug therapy: efficacy and mechanism of action in colorectal carcinoma.

In antibody-directed enzyme prodrug therapy, an enzyme conjugated to an antitumor antibody is given i.v. and localizes in the tumor. A prodrug is then given, which is converted to a cytotoxic drug selectively in the tumor. Ten patients with colorectal carcinoma expressing carcinoembryonic antigen received antibody-directed enzyme prodrug therapy with A5B7 F(ab')2 antibody to carcinoembryonic antigen conjugated to carboxypeptidase G2 (CPG2). A galactosylated antibody directed against the active site of CPG2 (SB43-gal) was given to clear and inactivate circulating enzyme. A benzoic acid mustard-glutamate prodrug was given when plasma enzyme levels had fallen to a predetermined safe level, and this was converted by CPG2 in the tumor into a cytotoxic form. Enzyme levels derived from quantitative gamma camera imaging and from direct measurements in plasma and tumor biopsies showed that the median tumor:plasma ratio of enzyme exceeded 10000:1 at the time of prodrug administration. Enzyme concentrations in the tumor (median, 0.47 units g(-1)) were sufficient to generate cytotoxic levels of active drug. The concentration of prodrug needed for optimal conversion (Km) of 3 microM was achieved. Prodrug conversion to drug was shown by finding detectable levels of drug in plasma. There was evidence of tumor response; one patient had a partial response, and six patients had stable disease for a median of 4 months after previous tumor progression (one of these six had a tumor marker response). Manageable neutropenia and thrombocytopenia occurred. Conditions for effective antitumor therapy were met, and there was evidence of tumor response in colorectal cancer.

Enzymatic deconjugation of erythrocyte polyglutamyl folates during preparation for folate assay: investigation with reversed-phase liquid chromatography.

Erythrocyte (RBC) folates occur mainly as 5-methyltetrahydrofolate polyglutamates. Determination of RBC folate concentration requires an initial deconjugation of these polyglutamates. In this study, existing HPLC methods were adapted to investigate the rate and extent of this deconjugation process. The action of endogenous plasma pteroyl-polyglutamate hydrolase activity was strongly affected by the conditions of sample preparation, with pH of the incubation mixture more critical to effective deconjugation than incubation time. Dilution of whole blood with 10 g/L ascorbic acid yielded fast hydrolysis of long-chain polyglutamates, and total conversion to 5-methyltetrahydrofolate monoglutamate occurred after 90 min of incubation at 37 degrees C. In contrast, dilution of whole blood with 10 g/L sodium ascorbate, with up to 90 min of incubation at 37 degrees C, yielded a mixture of polyglutamates of 5-methyltetrahydrofolate (glun = 1-8). As documented by direct HPLC analysis and in concurrent assays with Lactobacillus casei, acidification provided by ascorbic acid can have dramatic effects on the measurement of RBC folates.

Homocysteine and folate concentrations in blood from patients treated with hemodialysis.

Plasma homocysteine and plasma and erythrocyte folate concentrations before and after hemodialysis were measured in 31 patients with ESRD. Homocysteine and folate were measured by HPLC-fluorometric and microbiological methods, respectively. The mean plasma homocysteine level declined from 36.8 to 24.2 mumol/L during hemodialysis, indicating that homocysteine can be partly removed by hemodialysis (P < 0.0001). Mean plasma folate concentration before hemodialysis was 46.4 nmol/L and decreased to 25.9 nmol/L after hemodialysis (P < 0.0001), whereas mean erythrocyte folate concentration did not change (1295 and 1385 nmol/L before and after hemodialysis, respectively). Plasma folate concentrations showed a significant negative correlation with homocysteine concentrations before and after hemodialysis (r = -0.53, P < 0.003, and r = -0.59, P < 0.001, respectively). Furthermore, there were significant negative correlations between plasma homocysteine and erythrocyte folate concentrations both before (r = -0.60, P < 0.0005) and after hemodialysis (r = -0.49, P < 0.005). All patients had homocysteine concentrations over 12.0 mumol/L before hemodialysis, and only three had homocysteine concentrations lower than 12.0 mumol/L after hemodialysis. Although significant correlations existed between homocysteine and folate concentrations, the majority of the patients in this study appeared to have adequate folate nutriture as assessed by blood folate concentrations. It remains to be determined whether patients with ESRD have an altered homocysteine metabolism.

Identification of prodrug, active drug, and metabolites in an ADEPT clinical study.

Antibody-directed enzyme prodrug therapy (ADEPT) involves two phases. The first is an antibody-enzyme conjugate that localizes to tumor. The second phase is a prodrug that is administered when the enzyme-conjugate has cleared from blood and other nontumor tissues. In the pilot-scale clinical trial, the prodrug has been measured--in the plasma of patients, by liquid chromatography (HPLC) and by liquid chromatography-mass spectrometry (LC-MS). Active drug has been detected and metabolites identified. An indirect measurement of enzyme-conjugate in the plasma of patients has also been developed.

Synthesis and biological evaluation of poly-gamma-glutamyl metabolites of 10-deazaaminopterin and 10-ethyl-10-deazaaminopterin.

The chemical synthesis of a series of poly-gamma-glutamyl metabolites of the experimental anticancer drugs 10-deazaaminopterin (10-DAAM) and 10-ethyl-10-deazaaminopterin (10-EDAAM) has been carried out by the solid-phase procedure. The synthetic products were identical with the poly-gamma-glutamyl metabolites of radiolabeled 10-DAAM and 10-EDAAM produced by normal mouse tissues with regard to elution volume from [(diethylamino)ethyl]cellulose columns and susceptibility to hydrolysis by human plasma folylpolyglutamate hydrolase. Poly-gamma-glutamyl metabolites with a glutamate chain length of up to four glutamate residues were detected in the tissues. The antifolate activity was evaluated with methotrexate (MTX) sensitive and MTX-resistant strains of Lactobacillus casei and Streptococcus faecium. In general, inhibitory potency decreases with increasing Glu chain length. However there are two exceptions. Addition of one Glu residue to 10-DAAM enhances its potency for MTX-resistant L. casei and addition of one Glu residue to 10-EDAAM enhances its potency for the MTX-sensitive L. casei. As shown earlier for MTX polyglutamates, polyglutamylation greatly enhances the inhibitory potency of 10-DAAM and 10-EDAAM for L. casei thymidylate synthase. MTX polyglutamates are 15-30 times more inhibitory than the corresponding 10-DAAM derivatives and 30-60 times more inhibitory than the corresponding 10-EDAAM derivatives. Polyglutamylation of 10-DAAM had little influence on its ability to inhibit L. casei dihydrofolate reductase; however, with 10-EDAAM, addition of one or two Glu residues enhanced its inhibitory potency 2.3-fold.

Properties of folic acid gamma-glutamyl hydrolase (conjugase) in rat bile and plasma.

The properties of folic acid gamma-glutamyl hydrolase (conjugase) [EC 3.4.12.10] in rat bile and plasma were investigated. Conjugase activity in bile showed two pH optima; one at pH 4.5-5.0 and one at pH 6.7-7.5. The enzyme activity in plasma had a broad pH--profile with an optimum at pH 6.2-7.5. Conjugase activity from both bile and plasma was inhibited in the presence of the sulfhydryl reagent, p-hydroxymercuriphenylsulfonate, and stimulated in the presence of 2-mercaptoethanol. Conjugase activity in bile was inhibited by Zn2+ at pH 7.5 but not at pH 4.5 and was much more stable to heat at pH 4.5. No separation of the biliary conjugase activity measured at the two different pH values was obtained by Sephadex G-150 chromatography. Secretion of biliary conjugase was essentially constant over a 6-hour period when activity was assayed at pH 4.5 or pH 7.5. The enzyme in bile converted pteroyltriglutamate to a mixture of about 5% glutamate an 95% gamma-glutamylglutamate at either pH, whereas the enzyme in plasma produced 23% glutamate and 77% gamma-glutamylglutamate. The possible contribution of biliary conjugase to intestinal absorption of folate polyglutamates is discussed.