Accumulation of methotrexate in systemic tissues after intrathecal administration

Long-Term Constant Subcutaneous Drug Administration

In this chapter, a long-term drug delivery system for preclinical therapeutic research is introduced. By using a subcutaneously implanted ALZET® Osmotic Pumps osmotic pump, continuous zero-order delivery of drugs under investigation that need repeated oral or intravenous dosing is realizable. Compared to traditional delivery systems, implanted osmotic pumps present several advantages, such as that no external connections or researcher intervention is required during infusion and that it is possible to save time by eliminating the need for frequent animal handling and repetitive injection schedules. Most importantly, a stable peripheral concentration of a drug can be obtained using this constant drug delivery system, which would benefit researchers in verifying the efficiency of anti-rheumatoid drugs and establishing safety profiles in preclinical studies.

Systemic absorption of intrathecal methotrexate

Leptomeningeal spread of cancer is rare, difficult to both diagnostically confirm and treat, and associated with a poor prognosis. The blood-brain barrier largely prevents sufficient penetration of systemic therapy to be effective. Direct administration of intrathecal therapy has thus been used as an alternative treatment option. We present a case of breast cancer complicated by leptomeningeal spread. Intrathecal methotrexate was initiated, and the manifestation of systemic side effects suggested systemic absorption. This was subsequently confirmed by blood work showing detectable methotrexate levels following intrathecal administration as well as resolution of symptoms with reduction in the dose of methotrexate administered.

A successful compartmental approach for the treatment of breast cancer brain metastases

BACKGROUND

Brain metastases are challenging daily practice in oncology and remain a compartmental problem since most anti-cancer drugs do not cross the blood-brain barrier at relevant pharmacological concentrations.

METHODS

In a young woman with HER2-overexpressing breast cancer resistant to standard treatments, at the time of brain metastases progression, a ventricular reservoir was implanted for intrathecal drug injections and detailed pharmacokinetic studies.

RESULTS

A first association of intrathecal trastuzumab with intravenous cisplatin was offered to the patient. For trastuzumab, the mean cerebrospinal fluid trough concentration of 53.4 mg/L reached relevant levels, enabling the stabilization of the metastases. Adding intravenous cisplatin was not beneficial, since the cerebrospinal fluid exposure was almost undetectable under 0.08 mg/L. We then offered the patient an intrathecal combination of trastuzumab and methotrexate, because of their in vitro synergic cytotoxicity. The cerebrospinal fluid peak of methotrexate was 1037 µmol/L at 2 h, and the concentrations remained above the theoretical therapeutic concentration. After 2 months of this drug combination, we obtained an excellent response on the brain metastases.

CONCLUSION

Our preliminary study supports the interest of a compartmental approach through a direct administration of drugs into the cerebrospinal fluid for the treatment of breast cancer brain metastases.

Long-Term Constant Subcutaneous Drug Administration

In this chapter, a long-term drug delivery system for preclinical therapeutic research is introduced. By using a subcutaneously implanted ALZET^® osmotic pump, continuous zero-order delivery of drugs under investigation that need repeated oral or intravenous dosing is realizable. Compared to traditional delivery systems, implanted osmotic pumps present several advantages such as that no external connections or researcher intervention is required during infusion and that it is possible to save time by eliminating the need for frequent animal handling and repetitive injection schedules. Most importantly, a stable peripheral concentration of drug is able to be obtained using this constant drug delivery system, which would benefit researchers to verify the efficiency of antirheumatoid drugs and establish safety profiles in preclinical studies.

Side effects of methotrexate therapy for rheumatoid arthritis: A systematic review

Methotrexate (MTX) is used as an anchor disease-modifying anti-rheumatic drugs (DMARDs) in treating rheumatoid arthritis (RA) because of its potent efficacy and tolerability. MTX benefits a large number of RA patients but partially suffered from side effects. A variety of side effects can be associated with MTX when treating RA patients, from mild to severe or discontinuation of the treatment. In this report, we reviewed the possible side effects that MTX might cause from the most common gastrointestinal toxicity effects to less frequent malignant diseases. In order to achieve regimen with less side effects, the administration of MTX with appropriate dose and a careful pretreatment inspection is necessary. Further investigations are required when combining MTX with other drugs so as to enhance the efficacy and reduce side effects at the same time. The management of MTX treatment is also discussed to provide strategies for occurred side effects. Thus, this review will provide scholars with a comprehensive understanding the side effects of MTX administration by RA patients.

Liposomal Cytarabine Induces Less Neurocognitive Dysfunction Than Intrathecal Methotrexate in an Animal Model

Liposomal cytarabine is currently being tested clinically as an alternative to intrathecal (IT) methotrexate (MTX) for preventing relapse within the central nervous system among patients with acute lymphoblastic leukemia. To compare the toxicity and cognitive deficits caused by IT MTX versus liposomal cytarabine, juvenile Long Evans rats were treated with IT injections of MTX 1 mg/kg×4 doses over 8 days, or liposomal cytarabine 0.8 mg once. Mean concentrations of free cytarabine in cerebrospinal fluid remained above the cytotoxic threshold of 0.4 μM for 2 weeks after dosing. Animals treated with liposomal cytarabine exhibited normal recognition and spatial memory 4 weeks after injection. In contrast, exposure to IT MTX led to impaired cognitive function. In addition, mean hematocrit on day 11 was significantly lower in the MTX-treated animals (30.8%; 95% confidence interval, 27.0%-34.7%; n=6) compared with that in the liposomal cytarabine-treated animals (39.5%; 95% confidence interval, 38.4%-40.6%; n=6; P<0.0001). Our data suggest that liposomal cytarabine induces fewer neurocognitive deficits and less acute hematologic toxicity compared with IT MTX. Liposomal cytarabine may therefore have therapeutic advantages over IT MTX, if it is equally effective in preventing relapse.

Severe skin toxicity in pediatric oncology patients treated with voriconazole and concomitant methotrexate

We report the occurrence of skin toxicities in pediatric oncology patients on concomitant treatment with voriconazole and methotrexate (MTX). Of 23 patients who received this combination, 11 patients suffered from cheilitis and/or photosensitivity. In contrast, only in 1 of 9 patients who received voriconazole without MTX was photosensitivity observed. A mechanism of action was not able to be identified. We describe two cases with severe skin toxicities. Caution is warranted when using voriconazole and concomitant MTX.

A review of therapeutic challenges and achievements of methotrexate delivery systems for treatment of cancer and rheumatoid arthritis

PURPOSE

Methotrexate (MTX) is one of the most widely studied and effective therapeutics agents available to treat many solid tumors, hematologic malignancies, and autoimmune diseases such as rheumatoid arthritis; however, the poor pharmacokinetic and narrow safety margin of the drug limits the therapeutic outcomes of conventional drug delivery systems. For an improved delivery of MTX, several pathophysiological features such as angiogenesis, enhanced permeability and retention effects, acidosis, and expression of specific antigens and receptors can be used either as targets or as tools for drug delivery.

METHODS

There are many novel delivery systems developed to improve the pitfalls of MTX therapy ranged from polymeric conjugates such as human serum albumin, liposomes, microspheres, solid lipid nanoparticles, polymeric nanoparticles, dendrimers, polymeric micelles, in situ forming hydrogels, carrier erythrocyte, and nanotechnology-based vehicles such as carbon nanotubes, magnetic nanoparticles, and gold nanoparticles. Some are further modified with targeting ligands for active targeting purposes.

RESULTS

Such delivery systems provide prolonged plasma profile, enhanced and specific activity in vitro and in vivo in animal models. Nevertheless, more complementary studies are needed before they can be applied in human.

CONCLUSION

This review deals with the challenges of conventional systems and achievements of each pharmaceutical class of novel drug delivery vehicle.

Advances in individual prediction of methotrexate toxicity: a review

As the cure rates for haematological malignancies have improved, the exploration of the balance between efficacy and side effects has become a major research target. The antifolate methotrexate is widely used in the treatment of acute lymphoblastic leukaemia, non-Hodgkin lymphoma, and osteosarcoma. Even when given identical methotrexate doses, patients vary significantly in their response and pattern of toxicities. This diversity can, to some extent, be linked to sequence variations in genes involved in drug absorption, metabolism, excretion, cellular transport, and effector targets or target pathways. In the coming years pharmacogenomics is expected to change our approaches to individualised therapy with methotrexate. However, genetic polymorphisms affect the pharmacokinetics and dynamics of all the drugs a patient receive as well as the normal tissues tolerance to a given drug exposure. Thus, although high-throughput techniques will allow mapping of tens of thousands of genetic polymorphisms in one run, it will be a major challenge to dissect out which of these have the strongest impact on efficacy and toxicity and hence should be the targets for intervention. This paper discusses the pharmacology of methotrexate and reviews studies on haematological malignancies that have attempted to predict the risk of toxicity by specific clinical or genetic features.

Genome-wide interrogation of germline genetic variation associated with treatment response in childhood acute lymphoblastic leukemia

CONTEXT

Pediatric acute lymphoblastic leukemia (ALL) is the prototype for a drug-responsive malignancy. Although cure rates exceed 80%, considerable unexplained interindividual variability exists in treatment response.

OBJECTIVES

To assess the contribution of inherited genetic variation to therapy response and to identify germline single-nucleotide polymorphisms (SNPs) associated with risk of minimal residual disease (MRD) after remission induction chemotherapy.

DESIGN, SETTING, AND PATIENTS

Genome-wide interrogation of 476,796 germline SNPs to identify genotypes that were associated with MRD in 2 independent cohorts of children with newly diagnosed ALL: 318 patients in St Jude Total Therapy protocols XIIIB and XV and 169 patients in Children's Oncology Group trial P9906. Patients were enrolled between 1994 and 2006 and last follow-up was in 2006.

MAIN OUTCOME MEASURES

Minimal residual disease at the end of induction therapy, measured by flow cytometry.

RESULTS

There were 102 SNPs associated with MRD in both cohorts (median odds ratio, 2.18; P < or = .0125), including 5 SNPs in the interleukin 15 (IL15) gene. Of these 102 SNPs, 21 were also associated with hematologic relapse (P < .05). Of 102 SNPs, 21 were also associated with antileukemic drug disposition, generally linking MRD eradication with greater drug exposure. In total, 63 of 102 SNPs were associated with early response, relapse, or drug disposition.

CONCLUSION

Host genetic variations are associated with treatment response for childhood ALL, with polymorphisms related to leukemia cell biology and host drug disposition associated with lower risk of residual disease.

Pharmacodynamic properties of methotrexate and Aminotrexate during weekly therapy

4-Amino-pteroyl-glutamic acid (Aminotrexate; AMT) has several advantages over the related antifolate methotrexate (MTX), including greater potency, complete oral bioavailability, and greater accumulation by leukemic blasts in vitro. We compared the pharmacodynamic properties of AMT (given orally at 4 mg/m2 in two divided doses per week) and MTX (100 mg/m2 in four divided doses per week) among children with acute lymphoblastic leukemia. We find AMT and MTX to have equivalent penetration into the bone marrow compartment of these patients, as indicated by the steady-state concentrations within mature red blood cells (RBCs). However, MTX concentrations in the cerebrospinal fluid after oral dosage are significantly greater than AMT. To confirm these clinical observations, mice were treated four weekly injections of AMT or MTX, at a 1:20 dosage ratio, and tissue antifolate content was then determined over the subsequent 22 days. We confirm the selective exclusion of AMT from the CNS compartment, while showing equivalent accumulation of AMT and MTX in the RBCs, liver, spleen, kidneys and testes. Finally, we demonstrate that AMT, MTX, and their predominant polyglutamate species are equipotent inhibitors of their target intracellular enzyme dihydrofolate reductase, emphasizing the critical nature of steady-state tissue accumulation in determining the relative cytotoxic potency of these two antifolates.

Distribution of the novel antifolate pemetrexed to the brain

Pemetrexed disodium is a novel antifolate that exhibits potent inhibitory effects on multiple enzymes in folate metabolism. Phase II/III clinical trials have shown that pemetrexed is effective against various solid tumors. Like methotrexate, pemetrexed may be useful in treatment of primary and secondary brain tumors. In this study, we examined the central nervous system (CNS) distribution of pemetrexed and the interaction with an organic anion transport inhibitor indomethacin. Male Wistar rats were administered pemetrexed by either single intravenous bolus or constant intravenous infusion. Unbound pemetrexed in blood and brain was measured by simultaneous arterial blood and frontal cortex microdialysis sampling. In the i.v. bolus experiments, indomethacin was administered by i.v. bolus (10 mg/kg) followed by i.v. infusion (0.1 mg/kg/h) in a crossover manner. In the infusion experiments, the same dose of indomethacin was administered after a steady state was reached for pemetrexed. CNS distributional kinetics was analyzed by compartmental and noncompartmental methods. Both bolus and infusion studies showed that pemetrexed has a limited CNS distribution. The mean area under concentration-time curve (AUC)(brain)/AUC(plasma) ratio of unbound pemetrexed was 0.078 +/- 0.038 in the i.v. bolus study. The pemetrexed steady-state brain-to-plasma unbound concentration ratio after i.v. infusion was 0.106 +/- 0.054. The distributional clearance into the brain was approximately 10% of the clearance out of the brain in both the compartmental and noncompartmental analyses. Indomethacin had no effect on either the brain-to-plasma AUC ratio or the steady-state brain-to-plasma concentration ratio. The distribution of pemetrexed into the brain is limited, and an efflux clearance process, such as an efflux transporter, may be involved.

Pharmacokinetics Following Intraventricular Administration of Chemotherapy in Patients with Neoplastic Meningitis

Intraventricular administration of chemotherapy is one approach to overcoming the limited distribution of anticancer drugs and their active metabolites into the CNS. This form of regional chemotherapy has led to effective treatment of occult and overt meningeal leukaemia in humans. In contrast, the efficacy of this therapy is extremely limited in the treatment of leptomeningeal dissemination of various solid tumours. Pharmacokinetic studies of the commonly intraventricularly applied anticancer agents in humans have demonstrated that, using low drug doses, very high drug concentrations can be achieved in the cerebrospinal fluid (CSF) and relatively high concentrations in the leptomeninges but not in the brain tissue and the plasma. Therefore, this approach is not an effective treatment for bulky disease of brain tissue, and results in minimal systemic toxicity. In comparison with intralumbar administration, lower interpatient variability of CSF drug concentrations and improved clinical efficacy were observed. 'Concentration x time' schedules, i.e. frequent small drug doses over a short period, enable long-term CSF exposure to cytotoxic drug concentrations while avoiding excessively high and potentially neurotoxic drug concentrations. The technique of ventriculolumbar cerebrospinal perfusion delivers continuously high drug concentrations throughout the CSF for several hours, but its widespread use is limited by the technical complexities of this approach. In this article, the dosages, schedules and pharmacokinetic data of routinely used intraventricular agents in humans, e.g. methotrexate, cytarabine, glucocorticoids and thiotepa, are outlined in detail. In addition, pharmacokinetic data of investigational agents for intraventricular administration (diaziquone, DTC 101, mercaptopurine, mafosfamide, etoposide, topotecan, nimustine [ACNU] and bleomycin) are presented. Better understanding of the CSF pharmacology of these drugs is an essential prerequisite for safe, effective administration of these drugs. Investigational efforts are underway to verify the feasibility and efficacy of different dosages, schedules and combination therapies of these new intra-CSF agents. Current and future clinical research should also focus on methods allowing the delivery of tumoricidal drug concentrations for extended periods into the CSF and the brain tissue while minimising neurotoxicity and systemic toxicity (e.g. liposomal drug preparations, monoclonal antibodies, immunotoxins and gene therapy).

Systemic methotrexate exposure is greater after intrathecal than after oral administration

PURPOSE

To compare systemic exposure after intrathecal and oral methotrexate administration.

PATIENTS AND METHODS

We analyzed red cell methotrexate polyglutamate concentrations with a sensitive radioligand-binding assay in 80 patients enrolled in the Children's Cancer Group (CCG) trial 1922 for acute lymphoblastic leukemia. Methotrexate concentrations were measured 7 days after the last doses of intrathecal and oral routes, using patients as their own controls. Intrathecal methotrexate was given on an age-adjusted schedule. Data was normalized to the actual dose received per body surface area.

RESULTS

The mean red cell methotrexate concentration 7 days after the last of four weekly intrathecal doses of methotrexate was 178 pmol/mL red blood cells, which was significantly greater than the result 7 days after subsequent weekly oral methotrexate of 122 pmol/mL (P = 0.00001). Intrathecal dosing resulted in an average systemic exposure ratio of 1.7 to 1 compared with oral administration.

CONCLUSION

Intrathecal methotrexate administration results in significantly greater systemic exposure than oral administration. Our data support the hypothesis that the systemic effect of intrathecal methotrexate affects ALL therapy.

Acute neurotoxicity in children with B-lineage acute lymphoblastic leukemia (B-ALL) treated with intermediate risk protocols

BACKGROUND

This study describes the incidence of acute neurotoxicity (NT) in children with B-lineage acute lymphoblastic leukemia (ALL) treated with three intermediate risk protocols that differ in the intensity of central nervous system (CNS) "prophylaxis. "

PROCEDURE

A total of 122 patients (64 boys; median age 5.3 years) with B-lineage ALL without CNS leukemia diagnosed between February 1987 and December 1997 were enrolled in the intermediate risk (IR) protocols: Associazione Italiana di Ematologia ed Oncologia Pediatrica (AIEOP)-ALL 87 (n = 33), 91 (n = 51), and 95 (n = 38). Presymptomatic CNS therapy consisted of intrathecal methotrexate (six doses) and cranial irradiation (18 Gy) in the IR AIEOP 87 study, and extended triple intrathecal therapy with methotrexate, cytarabine, and prednisone depending on age in the IR AIEOP-ALL 91 and 95 protocols (20 and 17 total doses, respectively). World Health Organization (WHO) grade 4 acute neurotoxicity criteria were employed. Patients with neurologic symptoms, in addition to physical examination, underwent EEG, computed tomography (CT) and/or magnetic resonance imaging (MRI), and lumbar puncture to exclude CNS leukemia and infection.

RESULTS

Acute NT was not reported in AIEOP-ALL 87 treated patients, but we observed acute NT in 3 out of 51 (5.8%) AIEOP-ALL 91 patients, and in 7 out of 38 (18.4%) AIEOP-ALL 95 patients.

CONCLUSIONS

There was an increased incidence of acute NT in our patients with ALL treated with current intermediate risk protocols. The intensification of treatment, however, bettered event free survival (EFS) to 58%, 72% and 85% in IR AIEOP 87, 91 and 95 studies, respectively.

Intrathecal methotrexate-induced megaloblastic anemia in patients with acute leukemia

OBJECTIVE

To evaluate the occurrence of megaloblastic anemia induced by the infusion of therapeutic or prophylactic methotrexate in patients with acute leukemia.

DESIGN

Data on 3 patients with acute leukemia receiving intrathecal methotrexate were prospectively analyzed.

SETTING

Large tertiary-care center.

RESULTS

All 3 patients with acute leukemia developed megaloblastic anemia confirmed by examination of the bone marrow aspirate and biopsy. Two of the 3 patients had low folic acid levels, while all patients had normal serum B(12) levels. All patients responded favorably to a therapeutic trial of folic acid. The median time for recovery of the hematologic parameters in these patients was 7 days.

CONCLUSIONS

Intrathecally administered methotrexate may result in megaloblastic changes in the bone marrow of leukemic patients. The morphologic clues suggestive of folate deficiency in patients with acute leukemia may be masked by coexisting factors, such as the effects of cytotoxic treatment, prior transfusions, or persistent changes from the leukemic clone itself. Caution should be exercised to avoid attributing these changes to the neoplastic process, since the prognosis and treatment for the conditions involved are totally different. Repeat examination of the bone marrow, obtaining folic acid and vitamin B(12) levels, and a therapeutic trial of folic acid may help identify and reverse these changes.