Mucocutaneous ulcerations secondary to methotrexate

Although methotrexate (MTX) is used in several medical specialties including dermatology, rheumatology, and oncology, drug-induced mucocutaneous ulcerations rarely are reported. We present a 36-year-old woman with plaque psoriasis and psoriatic arthritis being treated with oral MTX (12.5 mg weekly) and oral methoxsalen plus UVA. Following an increase in MTX dose, she developed erosions and ulcerations on her oral mucosa and within her psoriatic plaques. All erosions and ulcerations healed within 2 weeks upon discontinuation of MTX.

Commentary: a case for minimizing folate supplementation in clinical regimens with pemetrexed based on the marked sensitivity of the drug to folate availability

Pemetrexed is a novel antifolate recently approved for the treatment of pleural mesothelioma and non-small cell lung cancer. In clinical regimens, pemetrexed is administered in conjunction with folic acid to minimize toxicity. However, excessive folate supplementation may also diminish the activity of this agent. The current study demonstrates, in several human solid tumor cell lines, that when extracellular 5-formyltetrahydrofolate levels are increased in vitro, within the range of normal human blood levels, there is a substantial decrease in pemetrexed activity upon continuous exposure to the drug. This was accompanied by a comparable lower level of trimetrexate activity consistent with an expansion of tumor cell folate pools. Likewise, when cells were exposed to pemetrexed with a schedule that simulates in vivo pharmacokinetics, there was markedly less cell killing with higher extracellular folate levels. Data are provided to indicate that 5-formyltetrahydrofolate is an acceptable surrogate for 5-methyltetrahydrofolate, the major blood folate, for this type of in vitro study. These observations and other reports suggest that, in view of the rise in serum folate and fall in serum homocysteine that has accompanied folic acid supplementation of food in the U.S., the addition of folic acid to regimens with pemetrexed should be limited to the lowest recommended level that provides optimal protection from pemetrexed toxicity.

[Pancytopenia induced by two low-dose injections of methotrexate in a patient treated for ulcerative colitis]

A 72 year-old man with steroid-dependent ulcerative colitis was treated with methotrexate at 25 mg subcutaneous weekly. Three days after the second injection of methotrexate a pancytopenia occurred associated with a Klebsiella pneumoniae septicemia which evolution was favourable under treatment. Pancytopenia is a rare but severe adverse effect of low-dose methotrexate therapy. In our patient the risk factors were age upper than 65 years, renal insufficiency and hypoalbuminemia. This report emphasizes the need for a close monitoring of hematologic tests after onset of methotrexate particularly if some risk factors are present.

Methotrexate delivery to the eye using transscleral hydrogel iontophoresis

PURPOSE

To evaluate methotrexate penetration and distribution profile in ocular structures after short low current transscleral hydrogel iontophoresis.

METHODS

Methotrexate iontophoresis was studied in rabbits using drug-loaded hydrogels mounted on a portable iontophoretic device. Drug distribution profile was evaluated 2, 4, and 8 hours after iontophoretic treatment of 1.6 mA/cm2 for 4 min. Ocular drug levels were also determined two hours after iontophoretic treatment of 5 mA/cm2, compared to mock iontophoresis and intravitreal injection of methotrexate.

RESULTS

Therapeutic drug levels were maintained for at least 8 h at the sclera and retina and for 2 h at the aqueous humor following the iontophoretic treatment. After increasing the current density, a twice-higher concentration was achieved at the vitreous and 8 to 20 time higher concentrations at the retina and sclera.

CONCLUSIONS

A short low current non-invasive iontophoretic treatment using methotrexate-loaded hydrogels has a potential clinical value in treating ocular inflammatory diseases and intraocular lymphoma.

Concentrations in plasma, epithelial lining fluid, alveolar macrophages and bronchial mucosa after a single intravenous dose of 1.6 mg/kg of iclaprim (AR-100) in healthy men

OBJECTIVES

A validated microbiological assay was used to measure concentrations of iclaprim (AR-100) in plasma, bronchial mucosa (BM), alveolar macrophages (AM) and epithelial lining fluid (ELF) after a single 1.6 mg/kg intravenous 60 min iv infusion of iclaprim.

METHODS

Male volunteers were randomly allocated to three nominal sampling time intervals 1-2 h (Group A), 3-4 h (Group B) and 5.5-7.0 h (Group C) after the start of the drug infusion.

RESULTS

Mean iclaprim concentrations in plasma, BM, AM and ELF, respectively, were for Group A 0.59 mg/L (SD 0.18), 0.51 mg/kg (SD 0.17), 24.51 mg/L (SD 21.22) and 12.61 mg/L (SD 7.33); Group B 0.24 mg/L (SD 0.05), 0.35 mg/kg (SD 0.17), 7.16 mg/L (SD 1.91) and 6.38 mg/L (SD 5.17); and Group C 0.14 mg/L (SD 0.05), no detectable level in BM, 5.28 mg/L (SD 2.30) and 2.66 mg/L (SD 2.08).

CONCLUSIONS

Iclaprim concentrations in ELF and AM exceeded the MIC(90) for penicillin-susceptible Streptococcus pneumoniae (MIC90 0.06 mg/L), penicillin-intermediate S. pneumoniae (MIC90 2 mg/L), penicillin-resistant S. pneumoniae (MIC90 4 mg/L) for 7, 7 and 4 h, respectively, and Chlamydia pneumoniae (MIC90 0.5 mg/L) for 7 h. Mean iclaprim concentrations in ELF exceeded the MIC90 for Haemophilus influenzae (MIC90 4 mg/L) and Moraxella catarrhalis (MIC90 8 mg/L) for up to 4 and 2 h, respectively; in AM the MIC90 was exceeded for up to 7 h. Furthermore, the MIC90 for methicillin-resistant Staphylococcus aureus of 0.12 mg/L was exceeded at all sites for up to 7 h. These data suggest that iclaprim reaches lung concentrations that should be effective in the treatment of community-acquired pneumonia.

Pemetrexed and Oxaliplatin for Metastatic Colorectal Cancer: Results of a Phase I Mayo Cancer Center Research Consortium Trial, MC0248

PURPOSE

Pemetrexed, an antifolate involved in purine and pyrimidine formation, is a potential alternative to fluoropyrimidines in the treatment of colorectal cancer. A phase I trial was performed to establish the maximum tolerated dose (MTD) of pemetrexed and oxaliplatin when B(12) and folate supplementation is used.

PATIENTS AND METHODS

Patients with metastatic colorectal cancer received folate (> 350 microg) daily and vitamin B(12) (1000 microg) every 9 weeks starting 7 days before chemotherapy. Pemetrexed over 10 minutes and oxaliplatin over 2 hours were given every 3 weeks in escalating dose cohorts.

RESULTS

Twenty-two patients were entered on 6 dose levels. The MTD was established at the highest dose level, pemetrexed 900 mg/m(2) and oxaliplatin 130 mg/m(2). Toxicities related to treatment at the MTD included grade 3 neutropenia and thrombocytopenia. For all dose levels combined, grade 3/4 toxicities included hematologic, neurologic, and gastrointestinal. Nine of 21 evaluable patients responded overall (response rate, 43%). The time to tumor progression was 11.9 months.

CONCLUSION

The MTD was determined to be pemetrexed 900 mg/m(2) and oxaliplatin 130 mg/m(2) every 21 days when folate and B (12) supplementation are used. Because of the observed tolerability and activity of this regimen, further evaluation is warranted.

Caffeine markedly sensitizes human mesothelioma cell lines to pemetrexed

Pemetrexed is a new generation antifolate approved for the treatment of mesothelioma and non-small cell lung cancer. Caffeine is known to augment radiation or chemotherapeutic drug-induced cell killing. The current study addresses the impact of caffeine on the activity of pemetrexed in mesothelioma cell lines. Caffeine enhanced pemetrexed activity in all four mesothelioma cell lines tested (H2052, H2373, H28 and MSTO-211H). Caffeine sensitized H2052 cells in a dose- and schedule-dependent manner, and was associated with a markedly decreased clonogenic survival. Caffeine sensitization occurred only in cells subjected to pulse, but not continuous, exposure to pemetrexed. Similar pemetrexed sensitization was also observed with the clinically better tolerated caffeine analog, theobromine. Pemetrexed sensitization by caffeine was associated with an increase in pemetrexed-induced phosphorylation of ataxia-telangiectasia-mutated (ATM) and Chk1. These data indicate that caffeine and its analog, theobromine, may be a useful approach to enhance pemetrexed-based chemotherapy.

A Phase 1 Study of Pralatrexate in Combination with Paclitaxel or Docetaxel in Patients with Advanced Solid Tumors

PURPOSE

Pralatrexate is a rationally designed antifolate with greater preclinical antitumor activity than methotrexate. Pralatrexate was synergistic with paclitaxel and with docetaxel in mouse xenograft experiments. This phase 1 study was designed to determine the maximum tolerated dose and toxicity of pralatrexate plus paclitaxel or docetaxel in patients with advanced cancer.

EXPERIMENTAL DESIGN

Pralatrexate was administered i.v. every 2 weeks (days 1 and 15) in a 4-week cycle. Depending on the taxane used and dose being tested, the taxane was administered on days 1 and 15; days 2 and 16; or days 1, 8, and 15. In the latter part of the study, patients in the docetaxel arm were treated with vitamin B(12) and folic acid supplementation to mitigate toxicity and allow pralatrexate dose escalation.

RESULTS

For the combination of pralatrexate plus paclitaxel without vitamin supplementation, dose-limiting stomatitis and peripheral neuropathy were encountered at the lowest dose levels tested. For pralatrexate plus docetaxel plus vitamin supplementation, pralatrexate 120 mg/m(2) plus docetaxel 35 mg/m(2) administered on the same day every other week was defined as the maximum tolerated dose and schedule, with dose-limiting toxicities at higher dose combinations including stomatitis and asthenia. Significant antitumor activity was observed for this combination in patients with non-small-cell lung cancer.

CONCLUSIONS

Pralatrexate (120 mg/m(2)) plus docetaxel (35 mg/m(2)) plus vitamin supplementation is well tolerated with signs of efficacy against non-small-cell lung cancer that merit phase 2 testing.

Dihydrofolate reductase as a target for chemotherapy in parasites

Opportunistic infections are known to cause morbidity and mortality in immunocompromised individuals. In addition, serious infections due to several parasites are also known to affect the quality and duration of life in normal individuals. The importance of dihydrofolate reductase (DHFR) in parasitic chemotherapy arises from its function in DNA biosynthesis and cell replication. DHFR catalyzes the reduction of dihydrofolate (DHF) to tetrahydrofolate (THF), an essential cofactor in the biosynthesis of thymidylate monophosphate (dTMP). Inhibition of DHFR leads to a deficiency of dTMP since DHF cannot be recycled, and thus causes inhibition of cell growth. Methotrexate (MTX) and aminopterin (AMT) were among the first known classical inhibitors of DHFR. Trimethoprim (TMP) and pyrimethamine (PYR) are among the first known non classical inhibitors of DHFR. TMP and PYR are selective but weak inhibitors of DHFR from several parasitic organisms and coadministration of sulfonamides is required to provide synergistic effects for clinical utility. Unfortunately, the side effects associated with sulfa drugs in this combination often result in cessation of therapy. Trimetrexate (TMQ) and piritrexim (PTX) are two potent non classical inhibitors, neither of which exhibit selectivity for pathogen DHFR and must be used with host rescue. However, the current combination therapy suffers from high cost, in addition, several mutations have been reported in the active site of parasitic DHFR rendering the infections refractive to known DHFR inhibitors. The selectivity of TMP is a hallmark in the development of DHFR inhibitors and several efforts have been made to combine the potency of PTX and TMQ with the selectivity of TMP. Thus the structural requirements for DHFR inhibition are of critical importance in the design of antifolates for parasitic chemotherapy. Structural requirements for inhibition have been studied extensively and novel agents that exploit the differences in the active site of human and parasitic DHFR have been proposed. This review discusses the synthesis and structural requirements for selective DHFR inhibition and their relevance to parasitic chemotherapy, since 1995.

Sequence-dependent administration of raloxifene and 5-fluorouracil/pemetrexed protects against pemetrexed cytotoxicity in human bone marrow

BACKGROUND

Pemetrexed (Alimta) is a new-generation multitargeted antifolate that inhibits several key enzymes in the de novo pathways of pyrimidine and purine biosynthesis, including thymidylate synthase (TS), dihydrofolate reductase (DHFR) and glycinamide ribonucleotide formyltransferase (GARFT). Alimta has demonstrated antitumor activity in a broad array of human malignancies, e.g. breast, non-small cell lung cancer, malignant pleural mesothelioma and pancreatic, colorectal, gastric, bladder, head and neck cancer, and is currently in phase III clinical trials. It has been reported that a dose of 600 mg/m2 of pemetrexed showed toxicity to bone marrow and the gastrointestinal system. The aim of this investigation was to evaluate raloxifene (RAL) in combination with 5-fluorouracil (5-FU)/pemetrered multitargeted antifolate (MTA) to determine the most effective regimens and cellular mechanism of action to mitigate pemetrexed cytotoxicity in human bone marrow cells.

MATERIALS AND METHODS

In order to determine the sequence-dependent interaction between MTA, 5-FU and RAL on proliferation, cell viability was carried out using the Quick Cell Proliferation Assay by exposing the HS-5 and MCF-7 cells to (i) MTA, 5-FU and RAL alone, or (ii) RAL 24 h prior to 5-FU followed 2 h later by MTA, or (iii) 5-FU 2 h prior to MTA followed 24 h later by RAL.

RESULTS

The growth rate in MCF-7 in early RAL was 69 +/- 8.65% and late RAL was 36 +/- 4.6% of the control whereas in bone marrow early RAL was 78 +/- 8.65% and late RAL was 52 +/- 5.49% of the control. The late RAL exhibits significant protection against MTA cytotoxicity in bone marrow. The findings were further supported by cell flow cytometry, apoptosis and Western blot analysis data.

CONCLUSION

This study suggests that sequence-dependent administration of RAL (5FU/MTA/RAL), in combination with 5-FU/MTA, protects against MTA toxicity in human bone marrow while maintaining the maximum inhibitory effect of pemetrexed in breast cancer.

Effects of antifolate drugs on the cellular uptake of radiofolates in vitro and in vivo

Targeting the folate receptor (alpha-FR) with radiolabeled folates for the noninvasive diagnosis and therapy of alpha-FR-overexpressing neoplastic tissue is of great interest. However, the tumor uptake of folate-based radiotracers was shown to be low compared with the high renal retention of radioactivity attributable to alpha-FR expression in the proximal tubule cells. In order to increase the tumor uptake of radiofolates, we wanted to stimulate alpha-FR expression or transport through coapplication of the antifolates methotrexate (MTX), raltitrexed (RTX), and pemetrexed (PMX).

METHODS

(99m)Tc-picolylamine monoacetic acid folate ((99m)Tc-PAMA-folate) was used for these studies. The in vitro experiments with antifolates were performed with alpha-FR-positive KB cancer cells. In vivo experiments were performed with KB tumor-bearing athymic nude mice. In vivo images were acquired with a small-animal SPECT/CT scanner.

RESULTS

KB cells incubated with solutions (10 micro mol/L) of MTX, RTX, or PMX for 24 h displayed twice as much (99m)Tc-PAMA-folate uptake as untreated cells. In contrast, KB tumor-bearing mice that received MTX intravenously 24 h before (99m)Tc-PAMA-folate showed significantly lower uptake of the radiofolate in tumors (1.35 +/- 0.33 percentage injected dose per gram of tissue [%ID/g] [mean +/- SD]) and the alpha-FR-positive kidneys (9.35 +/- 1.73 %ID/g) than did control mice (2.33 +/- 0.36 and 18.48 +/- 0.72 %ID/g, respectively, at 4 h after injection). When the antifolate PMX and (99m)Tc-PAMA-folate were injected 1 h apart, the tumor uptake of the radiotracer was unaffected (2.21 +/- 0.34 %ID/g at 4 h after injection), whereas radioactivity in the kidneys was significantly decreased (1.14 +/- 0.18 %ID/g at 4 h after injection). In vivo SPECT/CT studies demonstrated the specific accumulation of (99m)Tc-PAMA-folate in tumors and almost a complete absence of radioactivity in the renal tissue of mice preinjected with PMX.

CONCLUSION

Our data suggest that the preadministration of antifolates improves tumor-to-kidney ratios of radiofolates and opens a "therapeutic window" for folates radiolabeled with particle-emitting nuclides, which could otherwise be nephrotoxic.

Resistance to sulphadrug-based antifolate therapy in malaria: are we looking in the right place?

Sulphadrug treatment failure in malaria therapy cannot solely be ascribed to the build-up of genetic resistance within the parasitic genome. Although numerous in vitro studies have tried to determine the exact genetic markers that could predict treatment outcome in patients, this research has not been conclusive. Sulphadrugs work by competitive inhibition with pABA at one point of the pathway to de novo folate synthesis. However, evidence suggests that the malaria parasite is capable of overcoming this competitive inhibition by switching over to other metabolic pathways, like direct folate salvage from a person's bloodstream. In other words, increased folic acid administration, via diet or supplementation, may have reduced the effectiveness of sulphadrugs more than genetic mutations. Although in vitro studies are valuable for understanding disease mechanisms, we should not forget that the human being is infinitely more complex than any laboratory model.

Synergistic Induction of Folate Receptor β by All-Trans Retinoic Acid and Histone Deacetylase Inhibitors in Acute Myelogenous Leukemia Cells: Mechanism and Utility in Enhancing Selective Growth Inhibition by Antifolates

The folate receptor (FR) type beta is a promising target for therapeutic intervention in acute myelogenous leukemia (AML), owing particularly to its selective up-regulation in the leukemic cells by all-trans retinoic acid (ATRA). Here we show, using KG-1 and MV4-11 AML cells and recombinant 293 cells, that the histone deacetylase (HDAC) inhibitors trichostatin A (TSA), valproic acid (VPA), and FK228 potentiated ATRA induction of FR-beta gene transcription and FR-beta mRNA/protein expression. ATRA and/or TSA did not induce de novo FR synthesis in any of a variety of FR-negative cell lines tested. TSA did not alter the effect of ATRA on the expression of retinoic acid receptor (RAR) alpha, beta, or gamma. Chromatin immunoprecipitation assays indicate that HDAC inhibitors act on the FR-beta gene by enhancing RAR-associated histone acetylation to increase the association of Sp1 with the basal FR-beta promoter. Under these conditions, the expression level of Sp1 is unaltered. A decreased availability of putative repressor AP-1 proteins may also indirectly contribute to the effect of HDAC inhibitors. Finally, FR-beta selectively mediated growth inhibition by (6S) dideazatetrahydrofolate in a manner that was greatly potentiated in AML cells by ATRA and HDAC inhibition. Therefore, the combination of ATRA and innocuous HDAC inhibitors may be expected to facilitate selective FR-beta-targeted therapies in AML.

Intraocular injection of folate antagonist methotrexate induces neuronal differentiation of embryonic stem cells transplanted in the adult mouse retina

Transplanted embryonic stem (ES) cells can be integrated into the retinas of adult mice as well-differentiated neuronal cells. However, the integrated ES cells also have a tumorigenic effect just because they have the ability for multipotential differentiation to various types of tissues. Thus, control of neoplastic potentials of ES cells is very important for the treatment of degenerative or injured diseases. Mouse ES cells carrying the sequence for the green fluorescent protein (GFP) gene were transplanted into adult mouse retinas by intravitreal injections 20 h after intravitreal N-methyl-d-aspartate (NMDA) administration. One week after the ES cell injection, folate antagonist methotrexate (MTX) was injected intravitreally. Eyes were retrieved 4 weeks after ES cell transplantation for histologic analyses. Conventional histological analysis was performed by hematoxylin and eosin staining with the use of paraffin-embedded sections. Neuronal differentiation and teratogenic potential of ES cells were demonstrated by immunohistochemistry. The proliferative activity of transplanted cells was detected by mitotic index, proliferating cell nuclear antigen index and AgNOR count. The incorporation of transplanted ES cells in MTX-treated and non-treated retinas at 4 weeks after transplantation was observed in 8/16 eyes (50%) and 8/16 eyes (50%), respectively. Transplanted ES cells in MTX-treated retina showed increased neuronal differentiation and decreased expression of teratogenic markers, compared with ES cells in non-treated retina. The proliferative activity of transplanted ES cells in MTX-treated retina was lower than that in non-treated retina. These results suggest that intravitreal MTX treatment following transplantation can induce neuronal differentiation in the transplanted ES cells and decrease their proliferative activity.

Ultrastructural changes in rat livers perfused in vitro and in vivo with a high dose of methotrexate

Methotrexate is an antifolate that is widely used in the treatment of malignant tumours and other diseases. The present study was undertaken to examine the short-term effects of high doses of methotrexate (HD-MTX) on the ultrastructure and metabolic activity of isolated rat livers. The authenticity of the drug-induced changes was substantiated by the concomitant use of in vivo experiments. Isolated rat livers were infused with HD-MTX via the portal vein for 3 hours (total dose for each liver 2000 mg). For in vivo experiments, each rat received a single intravenous injection of a maximum tolerated dose of MTX (100 mg/kg body weight) that allowed the animals to survive for 3 days. At the end of each experimental period, MTX-treated and control livers were processed for light microscopy (LM), scanning (SEM) and transmission electron (TEM) microscopy. Oxygen consumption and thyroxine metabolism were measured in treated and control isolated livers. With the exception of a few minor differences, the structural changes in the hepatocytes after MTX treatment in vitro and vivo were similar. There were focal changes consisting of disruption of normal hepatic plates and swelling and vacuolation of the hepatocytes, with no clear evidence of restriction to a specific hepatic zone. SEM revealed striking changes in the plasma membrane, the microvillar system, intercellular junctions and the sinusoidal endothelium. TEM revealed disorganized endoplasmic reticulum, dispersion of the polyribosomes, a variety of mitochondrial changes, and glycogen redistribution. In MTX-treated isolated rat livers, the uptake of tetraiodothyronine (T4) was not affected, but triiodothyronine (T3) release was impaired. Oxygen consumption was increased in livers treated with MTX. Employing an organotypic liver perfusion model in conjunction with the in vivo experiment and the use of SEM, TEM and hepatic thyroxine measurements, this investigation revealed that infusion of HD-MTX induced early ultrastructual changes in cell membrane, intercellular junctions and cell organelles and disturbance in the functional integrity of the hepatocytes in isolated rat liver.

[Pneumocystis jirovecii pneumonia: an old disease with a new name]

Pneumocystis jirovecii pneumonia has historically been one of the most common opportunistic pneumonias and life-threatening infectious complications in HIV-infected patients. After the introduction of combination antiretroviral therapy, the incidence of Pneumocystis pneumonia and other opportunistic infections has decreased dramatically. Nowadays Pneumocystis pneumonia still occurs in patients unaware of their HIV status, in those not receiving combination antiretroviral therapy, or in those in whom it is ineffective due to resistance. Age factor is the diagnosis delaying one: patients aged more than 50 years are diagnosed with AIDS later than younger persons. Pneumocystis was thought to be a species of protozoa. Over the last 20 years, Pneumocystis has been shown to be a fungus, to be genetically diverse, host species specific, to colonize individuals with minor immunosuppression, and to cause clinical disease by "new" infection in addition to reactivation of latent childhood-acquired infection. Recently, the microorganism Pneumocystis carinii causing disease in humans has been renamed to Pneumocystis jirovecii. This article presents a clinical case of late diagnosis of Pneumocystis jirovecii pneumonia in a 62-year-old patient unaware of her HIV status and a review of literature reflecting epidemiological issues of Pneumocystis jirovecii and latest discoveries related to Pneumocystis as well as the rationale for renaming it.

Targeted drug delivery with dendrimers: comparison of the release kinetics of covalently conjugated drug and non-covalent drug inclusion complex

Dendrimers have unique characteristics including monodispersity and modifiable surface functionality, along with highly defined size and structure. This makes these polymers attractive candidates as carriers in drug delivery applications. Drug delivery can be achieved by coupling a drug to polymer through one of two approaches. Hydrophobic drugs can be complexed within the hydrophobic dendrimer interior to make them water-soluble or drugs can be covalently coupled onto the surface of the dendrimer. Using both methods we compared the efficacy of generation 5 PAMAM dendrimers in the targeted drug delivery of methotrexate coupled to the polymer. The amine-terminated dendrimers bind to negatively charged membranes of cells in a non-specific manner and can cause toxicity in vitro and in vivo. To reduce toxicity and to increase aqueous solubility, modifications were made to the surface hydroxyl groups of the dendrimers. For targeted drug delivery, the dendrimer was modified to have a neutral terminal functionality for use with surface-conjugated folic acid as the targeting agent. The complexation of methotrexate within a dendrimer changes the water insoluble drug into a stable and readily water-soluble compound. When this dendrimer complexed drug, however, was placed in a solution of phosphate buffered saline, the methotrexate was immediately released and displayed diffusion characteristics identical to free methotrexate. Covalently coupled methotrexate dendrimer conjugates were stable under identical conditions in water and buffered saline. Cytotoxicity tests showed that methotrexate as the dendrimer inclusion complex had an activity identical to the free drug in vitro. In contrast, folic acid targeted dendrimer with covalently conjugated methotrexate specifically killed receptor-expressing cells by intracellular delivery of the drug through receptor-mediated endocytosis. This study demonstrates that while drug as a dendrimer inclusion complex is readily released and active in vitro, covalently conjugated drug to dendrimer is better suited for specifically targeted drug delivery.

Phase I Study of Piritrexim and Gemcitabine in Patients With Advanced Solid Tumors

OBJECTIVES

In this phase I study, the combination of piritrexim and gemcitabine was given to establish the maximum tolerated dose and the recommended phase II dose, and to determine a toxicity and efficacy profile.

METHODS

Fifty-two patients with normal and impaired renal function were enrolled on this phase I study. The starting dose was piritrexim 10 mg 3 times daily (5 days of the week for 3 weeks and 1 week off each 28-day cycle) and gemcitabine 1000 mg/m2 on days 1, 8, and 15. The piritrexim was escalated in a stepwise fashion with this dose of gemcitabine and then with gemcitabine 1000 mg/m2 for days 1 and 15.

RESULTS

The recommended phase II dose of this combination was felt to be piritrexim 50 mg/day (10 mg every morning, 20 mg every noon, and 20 mg every evening) with gemcitabine 1000 mg/m2 on days 1, 8, and 15, and piritrexim 75 mg/day (25 mg thrice daily) with gemcitabine 1000 mg/m2 on days 1 and 15. Neutropenia and thrombocytopenia were the most often reported toxicity. Dose-limiting toxicity was thrombocytopenia in both groups. The number of renal-impaired patients enrolled was too small to establish a maximum tolerated dose for this group (piritrexim became unavailable), but the combination was tolerated in the patients with impaired renal dysfunction. There was 1 complete response, 1 partial response, and 1 minimal response.

CONCLUSION

The combination of piritrexim and gemcitabine was determined to be tolerable in heavily pretreated patients for use in solid tumors.

Severe encephalopathy induced by the first but not the second course of high-dose methotrexate mirrored by plasma homocysteine elevations and preceded by extreme differences in pretreatment plasma folate

Plasma homocysteine has recently been associated with the occurrence of methotrexate-related neurotoxicity. We observed extreme elevations of homocysteine in a 9-year-old boy presenting with leukemia treated with the ALL-BFM 95 protocol. Coma occurred at about the 71st hour from the first methotrexate administration, and lasted for 30 h but MRI and CT studies showed no intracranial pathology. The second course of high-dose methotrexate was administered with no complications. Homocysteine areas under the curve (AUC) were calculated as the sum of areas of rectangles during the 6-hour intervals from T(0) to T(72) hours (AUC(0--72)) and methotrexate AUCs were evaluated using MW/PHARM 3.3 software. The AUC of homocysteine during the first, toxic course was 5.2 times higher than AUC during the second administration, whereas AUC of methotrexate also differed by a factor of 5. Plasma concentrations of folate prior to the first and the second courses, respectively, were 4.4 versus 45 micromol/l making this difference the most striking discriminator between the two courses. Mutation analysis showed that the patient was heterozygous for the C 677 T mutation in the MTHFR gene. We suggest that plasma homocysteine, pretreatment plasma folate and possibly the presence of MTHFR mutations may be biomarkers of methotrexate toxicity and possibly its antifolate effect targeted towards the tumor as well.

Update on malignant mesothelioma

Mesotheliomas are uncommon in the United States, with an incidence of about 3,000 new cases per year (or a risk of about 11 per million Americans per year). Incidence and mortality, however, are probably underestimated. Most are associated with asbestos, although some have arisen in ports of prior radiation, and a reported association with simian virus (SV)40 remains controversial. About 85% of mesotheliomas arise in the pleura, about 91% in the peritoneum, and a small percentage in the pericardium or tunica vaginalis testis. The histology of about half of mesotheliomas is epithelial (tubular papillary), with the remainder sarcomatous or mixed. Multicystic mesotheliomas and well-differentiated papillary mesotheliomas are associated with long survival in the absence of treatment and should be excluded from clinical trials intended for the usual rapidly lethal histologic variants of the disease. The median survival is under a year, although longer median survivals for selected patients, particularly those with epithelial histology, have been reported in some combined-modality studies. Recent randomized trials have shown significant improvement in time to progression and survival for the addition of new antifolates to platinum-based chemotherapy.

Trimodal cancer treatment: beneficial effects of combined antiangiogenesis, radiation, and chemotherapy

It has been suggested that chemotherapy and radiotherapy could favorably be combined with antiangiogenesis in dual anticancer strategy combinations. Here we investigate the effects of a trimodal strategy consisting of all three therapy approaches administered concurrently. We found that in vitro and in vivo, the antiendothelial and antitumor effects of the triple therapy combination consisting of SU11657 (a multitargeted small molecule inhibitor of vascular endothelial growth factor and platelet-derived growth factor receptor tyrosine kinases), Pemetrexed (a multitargeted folate antimetabolite), and ionizing radiation were superior to all single and dual combinations. The superior effects in human umbilical vein endothelial cells and tumor cells (A431) were evident in cell proliferation, migration, tube formation, clonogenic survival, and apoptosis assays (sub-G1 and caspase-3 assessment). Exploring potential effects on cell survival signaling, we found that radiation and chemotherapy induced endothelial cell Akt phosphorylation, but SU11657 could attenuate this process in vitro and in vivo in A431 human tumor xenografts growing s.c. on BALB/c nu/nu mice. Triple therapy further decreased tumor cell proliferation (Ki-67 index) and vessel count (CD31 staining), and induced greater tumor growth delay versus all other therapy regimens without increasing apparent toxicity. When testing different treatment schedules for the A431 tumor, we found that the regimen with radiotherapy (7.5 Gy single dose), given after the institution of SU11657 treatment, was more effective than radiotherapy preceding SU11657 treatment. Accordingly, we found that SU11657 markedly reduced intratumoral interstitial fluid pressure from 8.8 +/- 2.6 to 4.2 +/- 1.5 mm Hg after 1 day. Likewise, quantitative T2-weighed magnetic resonance imaging measurements showed that SU11657-treated mice had reduced intratumoral edema. Our data indicates that inhibition of Akt signaling by antiangiogenic treatment with SU11657 may result in: (a) normalization of tumor blood vessels that cause prerequisite physiologic conditions for subsequent radio/chemotherapy, and (b) direct resensitization of endothelial cells to radio/chemotherapy. We conclude that trimodal cancer therapy combining antiangiogenesis, chemotherapy, and radiotherapy has beneficial molecular and physiologic effects to emerge as a clinically relevant antitumor strategy.

Myelopathy due to intrathecal chemotherapy: report of six cases

Intrathecal chemotherapy and systemic chemotherapy are used for both prophylaxis and treatment of central nervous system disease in hematologic malignancies. However, intrathecal treatment has some adverse effects, such as arachnoiditis, progressive myelopathy, and leukoencephalopathy. The authors describe six children in whom myelopathy and adhesive arachnoiditis developed after administration of intrathecal chemotherapy including methotrexate, cytosine arabinoside, and prednisolone. Urinary retention and incontinence, the main presenting complaints in all patients, developed within 12 hours after intrathecal therapy and spontaneously resolved within 7 days. Two patients were unable to walk. In these two, weakness in the lower extremities gradually recovered by 1 month but urinary incontinence did not improve. None of the children had sensory loss. On follow-up periodic recurrent urinary tract infection was noted in four patients. MRI findings corresponded to arachnoiditis. No response was recorded on tibial nerve somatosensory evoked potentials in all patients. Intrathecal chemotherapy, especially methotrexate, can cause spinal cord dysfunction in children with acute lymphoblastic leukemia and non-Hodgkin's lymphoma. Arachnoiditis should be kept in mind as a causative factor in recurrent urinary tract infection in patients receiving intrathecal chemotherapy.

High-Dose Methotrexate in Acute Lymphoblastic Leukemia: Where Is the Evidence for Its Continued Use?

High-dose intravenous methotrexate is an important component of many effective chemotherapeutic regimens for childhood acute lymphoblastic leukemia (ALL). Its use has a strong pharmacologic rationale: to overcome mechanisms of resistance of the malignant cells and to achieve cytotoxic concentrations in sanctuary sites for lymphoblasts. Although therapeutic progress in ALL during the past 4 decades has been closely associated with more widespread use of intravenous methotrexate and in progressively larger doses, little data exist to clearly support the use of high-dose intravenous methotrexate over a regimen of prolonged administration of low-dose methotrexate. The implied superiority of intravenous methotrexate mainly stems from studies that used identical leucovorin rescue with low-dose methotrexate or from studies of upfront window therapy in untreated children with ALL in which single standard doses of oral methotrexate were compared with high-dose intravenous methotrexate with leucovorin rescue. The evidence favoring administration of intravenous methotrexate for children with ALL is critically reviewed. Despite its extensive use, high-dose intravenous methotrexate has not been proved conclusively to be more effective than less toxic, less labor intensive, and less costly methods of methotrexate administration.