Folate levels measured by LC-MS/MS in patients with colorectal cancer treated with different leucovorin dosages

Three-Period Bioequivalence Study of Sodium Levofolinate Injection With Calcium Levofolinate for Injection and Sodium Folinate for Injection in Healthy Chinese Subjects

The aim of this study was to compare the bioequivalence and safety of test preparation sodium levofolinate injection with reference preparations of calcium levofolinate for injection and sodium folinate for injection in China. A single-center, randomized, open-label, 3-period, crossover test was conducted on 24 healthy subjects. Plasma concentration of levofolinate, dextrofolinate, and their metabolites l-5-methyltetrahydrofolate and d-5-methyltetrahydrofolate were quantified by a validated chiral-liquid chromatography-tandem mass spectrometry method. All adverse events (AEs) were documented to evaluate safety as they occurred and evaluated descriptively. Pharmacokinetic parameters (maximum plasma concentration, time to maximum concentration, area under the plasma concentration-time curve over the dosing interval, area under the plasma concentration-time curve from time 0 to infinity, terminal elimination half-life, and terminal rate constant) of 3 preparations were calculated. A total of 8 subjects (10 cases) of AEs occurred in this trial. No serious AEs or unexpected serious adverse reactions were observed. Sodium levofolinate was bioequivalent to calcium levofolinate and sodium folinate in Chinese subjects, and the 3 preparations were all well tolerated.

Increasing Dosage of Leucovorin Results in Pharmacokinetic and Gene Expression Differences When Administered as Two-Hour Infusion or Bolus Injection to Patients with Colon Cancer

The combination of 5-fluorouracil (5-FU) and leucovorin (LV) forms the chemotherapy backbone for patients with colorectal cancer. However, the LV administration is often standardized and not based on robust scientific data. To address these issues, a randomized pharmacokinetics study was performed in patients with colon cancer. Thirty patients were enrolled, receiving 60, 200 or 500 mg/m² LV as a single two-hour infusion. Blood, tumor, mucosa, and resection margin biopsies were collected. Folate concentrations were analyzed with LC-MS/MS and gene expression with qPCR. Data from a previous study where patients received LV as bolus injections were used as comparison. Saturation of methylenetetrahydrofolate (MeTHF) and tetrahydrofolate (THF) levels was seen after two-hour infusion and polyglutamated MeTHF + THF levels in tumors decreased with increasing LV dosage. The decrease was associated with decreased FPGS and increased GGH expression, which was not observed after LV bolus injection. In the bolus group, results indicate activation of a metabolic switch possibly promoting TYMS inhibition in response to 5-FU. Different metabolic mechanisms appear to be induced when LV is administered as infusion and bolus injection. Since maximal inhibition of TYMS by the 5-FU metabolite 5-fluoro-2'-deoxyuridine 5'-monophosphate (FdUMP) requires excess polyglutamated MeTHF, the results point in favor of the bolus regimen.

Sensitive and rapid simultaneous quantitation of leucovorin and its major active metabolite 5-methyl-tetrahydrofolate in human plasma using a liquid chromatography coupled with triple quadruple mass spectrometer

Bioanalysis of an endogenous compound such as leucovorin is never an easy task on liquid chromatography tandem mass spectrometer (LC-MSMS). Unless necessary, regulatory guidance discourages to work with surrogate matrix for calibration curve standard preparation. Herein, a selective and sensitive liquid chromatography-tandem mass spectrometry method for simultaneous determination of leucovorin and 5-methyl tetrahydrofolic acid in human plasma was developed and validated. Stable labeled internal standards i.e. leucovorin D₄ and 5- methyl tetrahydrofolic acid ¹³ C₅ were used as internal standards to track and compensate the parent compounds during processing and extraction from plasma. The method involves a rapid solid phase extraction from plasma followed by reverse phase gradient chromatography and mass spectrometry detection with a total run time of 5 minutes. The method was developed and validated from 5-2202 ng/ml for leucovorin and 5-1300 ng/ml for 5-methyl tetrahydrofolic acid. The mean recovery for leucovorin and 5-methyl tetrahydrofolic acid was found to be 100.4% and 100.9 % respectively. The validated method enabled the simultaneous analysis of leucovorin and 5-methyl tetrahydrofolic acid in samples from clinical pharmacokinetic studies of leucovorin. The peak concentration of leucovorin and 5-methyl tetrahydrofolic acid and ranged between 651ng/ml to 883 ng/ml and 518 ng/ml to 635 ng/ml, respectively, in fasted and fed conditions. The terminal half-life values for leucovorin and 5-methyl tetrahydrofolic acid ranged between 9.3 to 10.5 and 9.2 to 17.6 hours, respectively.

Plasma Metabolome Normalization in Rheumatoid Arthritis Following Initiation of Methotrexate and the Identification of Metabolic Biomarkers of Efficacy

Methotrexate (MTX) efficacy in the treatment of rheumatoid arthritis (RA) is variable and unpredictable, resulting in a need to identify biomarkers to guide drug therapy. This study evaluates changes in the plasma metabolome associated with response to MTX in RA with the goal of understanding the metabolic basis for MTX efficacy towards the identification of potential metabolic biomarkers of MTX response. Plasma samples were collected from healthy control subjects (n = 20), and RA patients initiating MTX therapy (n = 20, 15 mg/week) before and after 16 weeks of treatment. The samples were analyzed by a semi-targeted metabolomic analysis, and then analyzed by univariate and multivariate methods, as well as an enrichment analysis. An MTX response was defined as a clinically significant reduction in the disease activity score in 28 joints (DAS-28) of greater than 1.2; achievement of clinical remission, defined as a DAS-28 < 2.6, was also utilized as an additional measure of response. In this study, RA is associated with an altered plasma metabolome that is normalized following initiation of MTX therapy. Metabolite classes found to be altered in RA and corrected by MTX therapy were diverse and included triglycerides (p = 1.1 × 10⁻¹⁶), fatty acids (p = 8.0 × 10⁻¹²), and ceramides (p = 9.8 × 10⁻¹³). Stratification based on responses to MTX identified various metabolites differentially impacted in responders and non-responders including glucosylceramides (GlcCer), phosphatidylcholines (PC), sphingomyelins (SM), phosphatidylethanolamines (PE), choline, inosine, hypoxanthine, guanosine, nicotinamide, and itaconic acid (p < 0.05). In conclusion, RA is associated with significant alterations to the plasma metabolome displaying at least partial normalization following 16 weeks of MTX therapy. Changes in multiple metabolites were found to be associated with MTX efficacy, including metabolites involved in fatty acid/lipid, nucleotide, and energy metabolism.

Metastatic colorectal cancer: Advances in the folate-fluoropyrimidine chemotherapy backbone

Notwithstanding recent treatment advances in metastatic colorectal cancer (mCRC), chemotherapy with a combination of a fluoropyrimidine and a folate agent, often 5-fluorouracil (5-FU) and leucovorin, remains the backbone of treatment regimens for the majority of patients with mCRC. This is despite a recent focus on molecular-targeted treatments and patient stratification according to mutational status or expression levels of specific genes. Intracellular folate concentration was discovered to be pivotal in the cytotoxic efficacy of 5-FU, paving the way to the current standard combination therapy approach. Subsequent discovery that systemic chemotherapy agents, such as irinotecan and oxaliplatin, can further increase the efficacy of 5-FU-based treatments led to the development of several combination chemotherapy regimens, including FOLFOX, FOLFIRI and FOLFOXIRI. Subsequent efforts to optimise 5-FU-based treatments have focused on 5-FU analogues, initially capecitabine and the combination drug tegafur/gimeracil/oteracil (S-1) and then TAS-102, which has recently been evaluated in phase 3 clinical trials for refractory colorectal cancer. Further approaches taken to improve the efficacy of 5-FU chemotherapy regimens have focused on optimising the route and dosing schedules and regulating folate metabolism. Pharmacokinetic variability caused by the requirement for metabolic conversion of leucovorin has been central to recent research, and the development of agents such as arfolitixorin which bypass the need for metabolic conversion remains promising for future therapeutic candidates. In this review, we summarise the evidence leading to the current treatment regimens employing 5-FU and leucovorin, focusing on recent approaches taken to optimise and refine treatments to improve clinical outcomes in patients with mCRC.

The Novel Benzamide Derivative, VKNG-2, Restores the Efficacy of Chemotherapeutic Drugs in Colon Cancer Cell Lines by Inhibiting the ABCG2 Transporter

The overexpression of ATP-binding cassette transporter, ABCG2, plays an important role in mediating multidrug resistance (MDR) in certain types of cancer cells. ABCG2-mediated MDR can significantly attenuate or abrogate the efficacy of anticancer drugs by increasing their efflux from cancer cells. In this study, we determined the efficacy of the novel benzamide derivative, VKNG-2, to overcome MDR due to the overexpression of the ABCG2 transporter in the colon cancer cell line, S1-M1-80. In vitro, 5 μM of VKNG-2 reversed the resistance of S1-M1-80 cell line to mitoxantrone (70-fold increase in efficacy) or SN-38 (112-fold increase in efficacy). In contrast, in vitro, 5 μM of VKNG-2 did not significantly alter either the expression of ABCG2, AKT, and PI3K p110β protein or the subcellular localization of the ABCG2 protein compared to colon cancer cells incubated with the vehicle. Molecular docking data indicated that VKNG-2 had a high docking score (-10.2 kcal/mol) for the ABCG2 transporter substrate-drug binding site whereas it had a low affinity on ABCB1 and ABCC1 transporters. Finally, VKNG-2 produced a significant concentration-dependent increase in ATPase activity (EC50 = 2.3 µM). In conclusion, our study suggests that in vitro, VKNG-2 reverses the resistance of S1-M1-80, a cancer cell line resistant to mitoxantrone and SN-38, by inhibiting the efflux function of the ABCG2 transporter.

Plasma deoxyuridine as a surrogate marker for toxicity and early clinical response in patients with metastatic colorectal cancer after 5-FU-based therapy in combination with arfolitixorin

Purpose

The aim was to explore the correlation between increasing doses of [6R]-5,10-methylenetetrahydrofolate (arfolitixorin) and plasma concentrations of deoxyuridine (dUr) in patients with metastatic colorectal cancer (mCRC), subjected to 5-fluorouracil (5-FU)-based chemotherapy. The aim was further to investigate the possibility to predict toxicity and clinical response during treatment using gender, age, and plasma dUr as explanatory variables.

Methods

Thirty-three patients from the ISO-CC-005 phase I/IIa study, which investigated safety and tolerability of arfolitixorin at four dose levels, were included. Toxicity and clinical response were evaluated after 4 cycles of chemotherapy. Plasma dUr was quantified before (0 h) and 24 h after 5-FU administration at the first (C1) and fourth (C4) cycle using LC–MS/MS. Fit modelling was used to predict toxicity and clinical response.

Results

The dUr levels increased with increasing arfolitixorin dose. Females had higher total and haematological toxicity scores (p = 0.0004 and 0.0089, respectively), and needed dose reduction more often than males (p = 0.012). Fit modeling showed that gender and the dUr levels at C1-0 h and C4-24 h predicted total toxicity (p = 0.0011), whereas dUr C4-0 h alone was associated with gastrointestinal toxicity (p = 0.026). Haematological toxicity was predicted by gender and age (p = 0.0071). The haematological toxicity score in combination with the dUr levels at C1-24 h and C4-24 h predicted early clinical response (p = 0.018).

Conclusion

The dUr level before and during administration of 5-FU and arfolitixorin was predictive for toxicity and early clinical response and could be a potential surrogate marker for thymidylate synthase inhibition in patients with mCRC.

Trial registration

NCT02244632, first posted on ClinicalTrials.gov on September 19, 2014

Electronic supplementary material

The online version of this article (10.1007/s00280-020-04173-2) contains supplementary material, which is available to authorized users.

Folate pathway genes linked to mitochondrial biogenesis and respiration are associated with outcome of patients with stage III colorectal cancer

5-fluorouracil in combination with the folate leucovorin is the cornerstone in treatment of colorectal cancer. Transport of leucovorin into cells, and subsequent metabolic action, require expression of several genes. The aim was to analyze if tumoral expression of genes putatively involved in leucovorin transport, polyglutamation, or metabolism was associated with outcome of patients with stage III colorectal cancer treated with adjuvant chemotherapy. A total of 363 stage III colorectal cancer patients who received adjuvant bolus 5-fluorouracil + leucovorin alone, or in combination with oxaliplatin according to Nordic bolus regimes were included. Expression of 11 folate pathway genes was determined in tumors using quantitative real-time polymerase chain reaction and related to disease-free survival. The median follow-up time was 5 years. During follow-up, 114 (31%) patients suffered from recurrent disease. A high tumoral expression of the genes SLC46A1/PCFT, SLC19A1/RFC-1, ABCC3/MRP3, GGH, and MTHFD1L, which are involved in folate transport, polyglutamation, or metabolism, was associated with longer disease-free survival of the patients. Each of these genes either encodes mitochondrial enzymes or is being regulated by mitochondrial transcription factors. Expression of the SLC46A1/PCFT gene was most strongly associated with disease-free survival, regardless of treatment regimen. In conclusion, the results show that expression of folate pathway genes are associated with outcome of colorectal cancer patients treated with adjuvant 5-fluorouracil in combination with leucovorin. A prospective study needs to be conducted to determine if expression of these genes can be used to predict response to leucovorin and other folates that are now being tested in clinical studies. Moreover, there seems to be a link between folate metabolism and mitochondrial biogenesis and respiration that deserves further exploration.

Treatment of Rheumatoid Arthritis Using Combination of Methotrexate and Tripterygium Glycosides Tablets-A Quantitative Plasma Pharmacochemical and Pseudotargeted Metabolomic Approach

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by chronic destructive synovitis and is associated with progressive disability, systemic difficulties, premature death, and socioeconomic costs. Early intervention with disease-modifying antirheumatic drugs (DMARDs) like methotrexate (MTX) and its combination regimen would provide obvious benefits to patients, healthcare systems and society. MTX and tripterygium glycosides tablets (TGT_S) are most frequently prescribed medicines for RA, and the combination of them occurs frequently in anti-RA prescriptions. While the underlying combination mechanisms and the affected variation of drug blood level remain unclear. According to the American College of Rheumatology criteria for improvement, clinical evaluation following three treatment groups (i.e., MTX and TGT_S mono- and combined groups) were carried out at baseline and at the end of 12 weeks in a randomized controlled clinical trial. To monitor the affected variation of drug blood level and perturbation of metabolites caused by MTX plus TGT_S combined to treat active RA, the collected plasma samples were analyzed using RRLC-QqQ-MS and UHPLC-QE Orbitrap HRMS instruments. As a result, 39 metabolites including 7 MTX-related metabolites, 13 TGT_S-related migratory ingredients and 19 characteristic endogenous metabolites, were quantitatively determined in plasma samples of RA patients after oral administration. The potential mechanism of MTX and TGT_S combination were preliminarily elucidated on the aspect of clinical biochemical test indicators integrated with quantitative plasma pharmacochemistry and the pseudotargeted metabolomics.

Relationship between folate concentration and expression of folate-associated genes in tissue and plasma after intraoperative administration of leucovorin in patients with colorectal cancer

Purpose

The aim of study was to investigate the relationship between folate concentration and expression of folate-associated genes in tumour, mucosa and plasma of patients with colorectal cancer, after intraoperative administration of bolus leucovorin (LV).

Methods

Eighty patients were randomized into four groups to receive 0, 60, 200, or 500 mg/m² LV, respectively. Tissue and plasma folate concentrations were assessed by LC–MS/MS. Gene expression of ABCC3/MRP3, FPGS, GGH, MTHFD1L, SLC46A1/PCFT, and SLC19A1/RFC-1 was determined using quantitative PCR.

Results

The folate concentration in tumour increased with increasing dosage of LV. Half of the patients treated with 60 mg/m² did not reach a level above the levels of untreated patients. A significant correlation between folate concentration in tumour and mucosa was found in untreated patients, and in the group treated with 60 mg/m² LV. The 5-MTHF/LV ratio correlated negatively with folate concentration in mucosa, whereas a positive correlation was found in tumour of patients who received 200 or 500 mg/m² LV. A positive correlation was found between folate concentration and expression of all genes, except MTHFD1L, in patients who received LV. There was a negative correlation between 5-MTHF concentration in plasma of untreated patients and expression of GGH and SLC46A1/PCFT in tumour.

Conclusions

The results indicate the possibility of using the individual plasma 5-MTHF/LV ratio after LV injection as a surrogate marker for tissue folate concentration. Expression of several folate-associated genes is associated with folate concentration in tissue and plasma and may become useful when predicting response to LV treatment.

Electronic supplementary material

The online version of this article (10.1007/s00280-018-3690-9) contains supplementary material, which is available to authorized users.

An LC-MS chemical derivatization method for the measurement of five different one-carbon states of cellular tetrahydrofolate

The cofactor tetrahydrofolate (THF) is used to reduce, oxidize, and transfer one-carbon (1C) units required for the synthesis of nucleotides, glycine, and methionine. Measurement of intracellular THF species is complicated by their chemical instability, signal dilution caused by variable polyglutamation, and the potential for interconversion among these species. Here, we describe a method using negative mode liquid chromatography-mass spectrometry (LC-MS) to measure intracellular folate species from mammalian cells. Application of this method with isotope-labeled substrates revealed abiotic interconversion of THF and methylene-THF, which renders their separate quantitation particularly challenging. Chemical reduction of methylene-THF using deuterated sodium cyanoborohydride traps methylene-THF, which is unstable, as deuterated 5-methyl-THF, which is stable. Together with proper sample handling and LC-MS, this enables effective measurements of five active folate pools (THF, 5-methyl-THF, methylene-THF, methenyl-THF/10-formyl-THF, and 5-formyl-THF) representing the biologically important 1C oxidation states of THF in mammalian cells. Graphical abstract Chemical derivatization with deuterated cyanoborohydride traps unstable methylene-THF as isotope-labeled 5-methyl-THF, enabling accurate quantification by LC-MS.

Leucovorin Enhances the Anti-cancer Effect of Bortezomib in Colorectal Cancer Cells

Colorectal cancer is a major cancer type worldwide. 5-fluorouracil, often given with leucovorin, is the most commonly used drug in colorectal cancer chemotherapy, yet development of drug resistance to 5-fluorouracil in colorectal cancer cells is the primary cause of chemotherapy failure. Most patients receiving intravenous 5-fluorouracil develop side effects. Leucovorin, due to its vitamin-like profile, has few side-effects. Drug repurposing is the application of approved drugs to treat new indications. In this study, we performed a novel drug-repurposing screening to identify Food and Drug Administration-approved chemotherapeutic compounds possessing synergistic activity with leucovorin against colorectal cancer cells. We found that the combination of bortezomib and leucovorin enhanced caspase activation and increased apoptosis in colorectal cancer cells better than either agent alone. Further, the synergistic induction of apoptosis and inhibition of tumor growth were also observed in mouse colorectal cancer xenografts. These data support leucovorin enhances the anti-cancer effect of bortezomib and present this novel combinatorial treatment against colorectal cancer.

Multiplexed Dosing Assays by Digitally Definable Hydrogel Volumes

Stable and low-cost multiplexed drug sensitivity assays using small volumes of cells or tissue are in demand for personalized medicine, including patient-specific combination chemotherapy. Spatially defined projected light photopolymerization of hydrogels with embedded active compounds is introduced as a flexible and cost-efficient method for producing multiplexed dosing assays. The high spatial resolution of light projector technology defines multiple compound doses by the volume of individual compound-embedded hydrogel segments. Quantitative dosing of multiple proteins with a dynamic range of 1-2 orders of magnitude is demonstrated using fluorescently labeled albumins. The hydrogel matrix results from photopolymerization of low-cost poly(ethylene glycol) diacrylates (PEGDA), and tuning of the PEGDA composition enables fast complete dosing of all tested species. Dosing of hydrophilic and hydrophobic compounds is demonstrated using two first-line chemotherapy regimens combining oxaliplatin, SN-38, 5-fluorouracil, and folinic acid, with each compound being dosed from a separate light-defined hydrogel segment. Cytotoxicity studies using a colorectal cancer cell line show equivalent effects of dissolved and released compounds. Further control of the dosing process is demonstrated by liposomal encapsulation of oxaliplatin, stable embedding of the liposomes in hydrogels for more than 3 months, and heat-triggered complete release of the loaded oxaliplatin.

Phase 1 dose de-escalation trial of the endogenous folate [6R]-5,10-methylene tetrahydrofolate in combination with fixed-dose pemetrexed as neoadjuvant therapy in patients with resectable rectal cancer

Background Modufolin® ([6R]-5,10-methylene tetrahydrofolate; [6R]-MTHF) is an endogenous biomodulator that is being developed as an alternative to leucovorin, a folate prodrug used in the treatment of colorectal cancer. The objective of this phase 1 dose de-escalation trial was to estimate the minimum tolerated dose of [6R]-MTHF to be used in combination with pemetrexed 500 mg/m² in the neoadjuvant treatment of patients with rectal cancer. Methods Adult patients (≥18 years) with resectable rectal adenocarcinoma were allocated to [6R]-MTHF doses of 500, 100, 50, and 10 mg/m² in combination with pemetrexed 500 mg/m². [6R]-MTHF was administered as an intravenous (i.v.) bolus injection 1 week prior to the first dose of pemetrexed and then once weekly for 9 weeks; pemetrexed was administered by i.v. infusion once every 21 days for three cycles. Results Twenty-four patients (mean [SD] age, 63.1 [12.9] years) were enrolled in the study. A total of 72 treatment-related adverse events (AEs) were reported, of which the most common were fatigue (n = 17; 23.6 %), nausea (n = 10; 13.9 %), and diarrhea (n = 5; 6.9 %). The incidence of treatment-related AEs by [6R]-MTHF dose level (500, 100, 50, 10 mg/m²) was 11.1 % (n = 8), 13.9 % (n = 10), 45.8 % (n = 33), and 29.2 % (n = 21), respectively. There were no dose-limiting toxicities, and only two (2.8 %) treatment-related AEs were grade 3 in severity. Of the 11 serious AEs reported, none were considered to be related to [6R]-MTHF treatment. Conclusions The results of this phase 1 study indicate that the estimated minimum tolerated dose of [6R]-MTHF was 100 mg/m² once weekly in combination with pemetrexed 500 mg/m². The low toxicity profile of [6R]-MTHF supports its further evaluation as a component of systemic chemotherapy in the management of colon and rectal cancer.

Expression of Folate Pathway Genes in Stage III Colorectal Cancer Correlates with Recurrence Status Following Adjuvant Bolus 5-FU-Based Chemotherapy

Colorectal cancer is commonly treated with 5-fluorouracil and 5-formyltetrahydrofolate (leucovorin). Metabolic action of leucovorin requires several enzymatic steps that are dependent on expression of corresponding coding genes. To identify folate pathway genes with possible impact on leucovorin metabolism, a retrospective study was performed on 193 patients with stage III colorectal cancer. Relative expression of 22 genes putatively involved in leucovorin transport, polyglutamation and metabolism was determined in tumor and mucosa samples using quantitative real-time polymerase chain reaction. After surgery, patients received adjuvant 5-fluorouracil-based bolus chemotherapy with leucovorin during six months, and were followed for 3 to 5 years. Cox regression analysis showed that high tumoral expression of the genes SLC46A1/PCFT (proton-coupled folate transporter) and SLC19A1/RFC-1 (reduced folate carrier 1) correlated significantly (p < 0.001 and p < 0.01, respectively) with a decreased risk of recurrent disease, measured as disease-free survival (DFS). These two genes are involved in the transport of folates into the cells and each functions optimally at a different pH. We conclude that SLC46A1/PCFT and SLC19A1/RFC-1 are associated with DFS of patients with colorectal cancer and hypothesize that poor response to 5-fluorouracil plus leucovorin therapy in some patients may be linked to low expression of these genes. Such patients might need a more intensified therapeutic approach than those with high gene expression. Future prospective studies will determine if the expression of any of these genes can be used to predict response to leucovorin.

A pharmacokinetic and pharmacodynamic investigation of Modufolin® compared to Isovorin® after single dose intravenous administration to patients with colon cancer: a randomized study

PURPOSE

Leucovorin is commonly used as folate supplement in 5-fluorouracil-based chemotherapy, but needs to be converted to active 5,10-methylenetetrahydrofolate (methyleneTHF) intracellularly. This provides for interindividual differences. MethyleneTHF has recently been developed into the stable, distributable drug, Modufolin®. The aim was to compare the concentration of folate metabolites in tumor, mucosa, and plasma of patients with colon cancer after administration of Modufolin® or Isovorin® (levo-leucovorin).

METHODS

Thirty-two patients scheduled for colon resection were randomized to receive Modufolin® or Isovorin® at dosage of 60 or 200 mg/m². The study drug was given as one i.v. bolus injection after anesthesia. Plasma was collected for pharmacokinetic (PK) analysis before, during, and after surgery. Tissue biopsies were collected at surgery. Folate metabolites were analyzed by LC-MS/MS.

RESULTS

MethyleneTHF and THF concentrations were significantly higher in mucosa (p < 0.01, both dosages) and tumors (p < 0.01, 200 mg/m²) after Modufolin® as compared to Isovorin® administration. The results correlated with PK observations. The Modufolin® to Isovorin® C(max) ratio for methyleneTHF was 113 at 200 mg/m² and 52 at 60 mg/m²; the AUC(last) ratios were 17 and 9, respectively. The THF plasma concentrations were also higher after Modufolin® administration (C(max) ratio 23, AUC(last) ratio 13 at 200 mg/m²; C(max) ratio 15, AUC(last) ratio 11 at 60 mg/m²).

CONCLUSION

Modufolin® administration resulted in significantly higher methyleneTHF levels than Isovorin® and may potentially increase the efficacy of 5-fluorouracil-based chemotherapy. The results encourage further evaluation of Modufolin® as a substitute to Isovorin® including the potential clinical benefits.