ENACT: a protocol for a randomised placebo-controlled trial investigating the efficacy and mechanisms of action of adjunctive N-acetylcysteine for first-episode psychosis

Background

First-episode psychosis (FEP) may lead to a progressive, potentially disabling and lifelong chronic illness; however, evidence suggests that the illness course can be improved if appropriate treatments are given at the early stages. Nonetheless, the efficacy of antipsychotic medications is suboptimal, particularly for negative and cognitive symptoms, and more efficacious and benign treatments are needed. Previous studies have shown that the antioxidant amino acid N-acetylcysteine (NAC) reduces negative symptoms and improves functioning in chronic schizophrenia and bipolar disorder. Research is scarce as to whether NAC is beneficial earlier in the course of illness. The primary aim of this study is to determine the efficacy of treatment with adjunctive NAC (2 g/day for 26 weeks) compared with placebo to improve psychiatric symptoms in young people experiencing FEP. Secondary aims are to explore the neurobiological mechanisms underpinning NAC and how they relate to various clinical and functional outcomes at 26- and 52-week follow-ups.

Methods/design

ENACT is a 26-week, randomised controlled trial of adjunctive NAC versus placebo, with a 26-week non-treatment follow-up period, for FEP. We will be recruiting 162 young people aged 15–25 years who have recently presented to, and are being treated at, the Early Psychosis Prevention and Intervention Centre, Melbourne, Australia. The primary outcome is the Total Score on the Positive and Negative Syndrome Scale which will be administered at baseline, and weeks 4, 8, 12, 26 (primary endpoint), and 52 (end of study). Secondary outcomes include: symptomatology, functioning, quality of life, neurocognition, blood-derived measures of: inflammation, oxidative and nitrosative stress, and magnetic resonance spectroscopy measures of glutathione concentration.

Discussion

Targeted drug development for FEP to date has generally not involved the exploration of neuroprotective agents. This study has the potential to offer a new, safe, and efficacious treatment for people with FEP, leading to better treatment outcomes. Additionally, the neuroprotective dimension of this study may lead to a better long-term prognosis for people with FEP. It has the potential to uncover a novel treatment that targets the neurobiological mechanisms of FEP and, if successful, will be a major advance for psychiatry.

Trial registration

Australian New Zealand Clinical Trials Registry, ID: ACTRN12618000413224. Registered on 21 March 2018.

HLA-DP allele-specific T cell responses to beryllium account for DP-associated susceptibility to chronic beryllium disease

Occupational exposure to small molecules, such as metals, is frequently associated with hypersensitivity reactions. Chronic beryllium (Be) disease (CBD) is a multisystem granulomatous disease that primarily affects the lung, and occurs in approximately 3% of individuals exposed to this element. Immunogenetic studies have demonstrated a strong association between CBD and possession of alleles of HLA-DP containing glutamic acid (Glu) at position 69 in the HLA-DP beta-chain. T cell clones were raised from three patients with CBD in whom exposure occurred 10 and 30 years previously. Of 25 Be-specific clones that were obtained, all were restricted by HLA-DP alleles with Glu at DP beta69. Furthermore, the proliferative responses of the clones were absolutely dependent upon DP beta Glu(69) in that a single amino acid substitution at this position abolished the response. As befits a disease whose pathogenesis involves a delayed type hypersensitivity response, the large majority of Be-specific clones secreted IFN-gamma (Th1) and little or no IL-4 (Th2) cytokines. This study provides insights into the molecular basis of DP2-associated susceptibility to CBD.

Antigen presentation by interferon-gamma-treated thyroid follicular cells inhibits interleukin-2 (IL-2) and supports IL-4 production by B7-dependent human T cells

The consequence of recognition of antigen on antigen-presenting cells that are induced to express major histocompatibility complex (MHC) class II molecules following an inflammatory process is still not clear. In this study, we have investigated the outcome of antigen presentation by epithelial cells and we have used as a model thyroid follicular cells (TFC) that are known to express MHC class II molecules in autoimmune thyroid diseases and acquire the capacity to present autoantigens to T cells infiltrating the thyroid gland. The result show that MHC class II-expressing TFC were unable to stimulate a primary T cell alloresponse, using CD4+ T cells from three HLA-mismatched responders. Phenotypic analysis showed that TFC, after incubation with interferon-gamma, do not express the costimulatory molecules B7-1 (CD80) and -2 (CD86). Addition of murine DAP.3 cells expressing human B7-1 (DAP.3-B7) to cultures containing peripheral blood CD4+ T cells and DR1-expressing TFC led to a proliferative response, suggesting that the failure of TFC to stimulate a primary alloresponse was due to a lack of co-stimulation. Similarly, HLA-DR-restricted, influenza-specific T cell clones dependent on B7 for co-stimulation did not respond to peptide presented by TFC; again the lack of response could be overcome by co-culture of TFC with DAP.3-B7. Furthermore, recognition of antigen on TFC inhibited interleukin-2 (IL-2) production in the B7-dependent T cells. In contrast, in T helper type 0 (Th0) T cells, IL-4 release was not affected by TFC presentation. In addition, antigen presentation by TFC favored IL-4 production relative to IL-2 production by B7-independent Th0 clones. These results suggest that antigen presentation by MHC class II+ TFC may induce tolerance in autoreactive Th1 cells but may simultaneously favors a Th2 response in uncommitted T cells, and thereby support autoantibody production.

Human alpha beta T-cell receptor CD4-CD8 T-cell clones are predominantly Th0-like

The cytokine production profile, focusing on interleukin-4 (IL-4), interferon-gamma (IFN-gamma) and interleukin-10 (IL-10) of human CD4+, CD8+ and CD4- CD8- alpha beta T cells cloned from the peripheral blood of healthy individuals was compared. Solid-phase anti-CD3 stimulation of CD4- CD8- alpha beta T cell clones from one individual revealed a significantly increased frequency of IL-4-producing clones (81%), compared to CD4+ T cells (24%) or CD8+ (28%). All five CD4- CD8- alpha beta T-cell clones from two other individuals also produced IL-4. Clones that produced IFN-gamma with undetectable IL-4 production, thus being of the 'classical' Th1 phenotype, were infrequent in CD4- CD8- alpha beta T-cell clones (19%) compared to CD4+ (71%), and CD8+ clones (72%) cloned in OKT3, and CD4+ cells cloned in phytohaemaglutinin A (77%). Unlike previously reported studies with gamma delta cells, the alpha beta CD4- CD8- T cells produced IL-10 at appreciable frequency (38%) in PHA generated clones. The supernatants from anti-CD3 stimulated CD4- CD8- alpha beta T-cell clones contained sufficient IL-4 to activate B cells, enhancing CD23 and surface immunoglobulin M (IgM) expression and co-stimulating B-cell proliferation. These findings suggest that the function of CD4- CD8- alpha beta T cells is distinct from that of most CD4+ or CD8+ T cells.

Methotrexate analogues—XVII

A new analogue of methotrexate was synthesized from 4-amino-4-deoxy-N10-methylpteroic acid and D,L-homocysteic acid. The product (mAPA-HCysA) was bound tightly to L1210 mouse leukemia dihydrofolate reductase (IC50 = 1 nM), inhibited L1210 cell proliferation in culture (IC50 = 0.3 microM), and prolonged the survival of L1210 leukemic mice (98% increase in lifespan at 120 mg/kg, qdx9). Studies on the interaction of mAPA-HCysA with partially purified mouse liver folyl polyglutamate synthetase revealed that mAPA-HCysA was not a substrate. Hence, the increased dose of mAPA-HCysA required to inhibit tumor growth in vitro and in vivo relative to methotrexate may reflect, in part, the inability of this compound to form non-effluxing polyglutamates. Folyl polyglutamate synthetase was competitively inhibited by mAPA-HCysA (K1 = 190 +/- 70 microM) when folate was the variable substrate. Thus, mAPA-HCysA is the first known compound to inhibit both mammalian dihydrofolate reductase and mammalian folyl polyglutamate synthetase.

Methotrexate analogues. 20. Replacement of glutamate by longer-chain amino diacids: effects on dihydrofolate reductase inhibition, cytotoxicity, and in vivo antitumor activity

Chain-extended analogues of methotrexate were synthesized by condensation of 4-amino-4-deoxy-N10-methylpteroic acid with esters of L-alpha-aminoadipic, L-alpha-aminopimelic, and L-alpha-aminosuberic acids, followed by ester hydrolysis with acid or base. Coupling was accomplished in up to 85% yield by the use of the peptide bond forming reagent diethyl phosphorocyanidate at room temperature. The products were found to bind bacterial (Lactobacillus casei) and mammalian (L1210 mouse leukemia) dihydrofolate reductase with an affinity comparable to methotrexate and were also equitoxic to L1210 cells in culture. Cytotoxicity increased up to 3-fold as the number of CH2 groups in the amino acid side chain was extended from two to five. The alpha-aminoadipate and alpha-aminopimelate analogues were poor substrates for carboxypeptidase G1, confirming that this enzyme has a strict requirement for a C-terminal L-glutamic acid residue. The in vivo antitumor activity of the chain-extended analogues against L1210 leukemia in mice was comparable to that of the parent drug on the qd X 9 schedule, but higher doses were required to achieve the same increase in survival. The results were consistent with findings, reported separately, that these compounds are poor substrates for folate polyglutamate synthetase and therefore would not be expected to form gamma-polyglutamates once they enter a cell. This distinctive property has potential therapeutic implications for the treatment of certain MTX-resistant tumors whose resistance may be associated with a lower than normal capacity to form gamma-polyglutamates in comparison with proliferative tissues such as intestinal mucosa or marrow.

Methotrexate analogues. 15. A methotrexate analogue designed for active-site-directed irreversible inactivation of dihydrofolate reductase

N alpha-(4-Amino-4-deoxy-N10-methylpteroyl)-N epsilon-(iodoacetyl)-L-lysine (1) was synthesized as a potential active-site-directed irreversible inhibitor of dihydrofolate reductase (DHFR). In an ultraviolet spectrophotometric assay of dihydrofolate reduction of Lactobacillus casei DHFR, 1 and methotrexate (MTX, 4-amino-4-deoxy-N10-methylpteroyl-L-glutamic acid) had ID50 values of 4.5 and 6.2 nM. The corresponding ID50 values in a competitive radioligand binding assay against [3H]MTX were 31 and 16 nM. Thus, as reversible inhibitors of this enzyme over a short exposure time, 1 and MTX had comparable activity. On the other hand, when L. casei DHFR was incubated for up to 6 h with 0.1 or 1.0 microM 1, a progressive decrease in the ability of [3H]MTX to subsequently displace the drug was observed. When MTX itself was used at the same concentrations, the extent of displacement of [3H]MTX did not decrease with time. These results were consistent with rapid reversible binding of 1 to the enzyme, followed more slowly by covalent bond formation near the active site. The pH profile for this effect followed a curve with a sigmoidal shape. The apparent inflection point near pH 7.2 was consistent with alkylation of a histidine residue.

Methotrexate analogues. 14. Synthesis of new gamma-substituted derivatives as dihydrofolate reductase inhibitors and potential anticancer agents

The gamma-tert-butyl ester (1), gamma-hydrazide (2), gamma-n-butylamide (3), and gamma-benzylamide (4) derivatives of methotrexate (MTX) were synthesized from 4-amino-4-deoxy-N10-methylpteroic acid (APA) and the appropriate blocked L-glutamic acid precursors with the aid of the peptide bond forming reagent diethyl phosphorocyanidate. The affinity of these side chain modified products for dihydrofolate reductase (DHFR) from Lactobacillus casei and L1210 mouse leukemic cells was determined spectrophotometrically or by competitive radioligand binding assay, and their cytotoxicity was evaluated against L1210 leukemic cells in culture. The results provide continuing support for the view that the "gamma-terminal region" of the MTX side chain is an attractive site for molecular modification of this anticancer agent.

Methotrexate analogues. 13. Chemical and pharmacological studies on amide, hydrazide, and hydroxamic acid derivatives of the glutamate side chain

Carbodiimide-mediated condensation of 4-amino-4-deoxy-N10-methylpteroic acid (APA) with several alkyl, aralkyl, and aryl amines, in the presence or absence of N-hydroxysuccinimide, was employed in order to prepare new lipid-soluble bis(amide) derivatives of methotrexate (MTX) as potential prodrugs. MTX dianilide was likewise prepared, in comparable yield, from APA and L-glutamic acid dianilide via the mixed carboxylic--carbonic anhydride method. Dihydrazide and bis(N-methylhydrazide) derivatives of MTX were formed readily from MTX diethyl ester. However, reaction with hydroxylamine led to MTX gamma-monohydroxamic acid as the sole isolated product. The bis adduct appears to form, but is unstable during workup. The identity of the product was confirmed by independent mixed anhydride synthesis from APA and the gamma-monohydroxamate of L-glutamic acid. Treatment of MTX dimethyl ester with N,N-dimethylhydrazine unexpectedly yielded MTX gamma-monomethyl ester. MTX dianilide was active against L1210 leukemia in mice, with a +155% increase in life span at a dose of 160 mg/kg given ip in 10% Tween 80 on a q3d X 3 schedule. The bis(p-chlorobenzylamide), bis(p-methoxybenzylamide), and dihydrazide were also active against L1210 leukemia in vivo, but to a lesser extent than the dianilide. The gamma-monohydroxamic acid derivative showed activity (+111% ILS at 40 mg/kg) similar to that of MTX and was found to bind to a partially purified dihydrofolate reductase preparation from L1210 cells with an ID50 of 0.005 microM as compared to 0.007 microM for MTX. In vivo experiments in mice indicated that the pharmacokinetic properties of this compound and of MTX are similar but failed to demonstrate any advantage over MTX in terms of selective uptake into tumor (sc implanted P388 leukemia) or improved penetration of the central nervous system. The activities of the dianilide, bis(benzylamide), and dihydrazide derivatives in vivo are of interest in view of their low toxicity relative to MTX against cells in culture, which suggests that these derivatives are probably acting as prodrugs in the intact animal.

Comparative effects of citrovorum factor and carboxypeptidase G1 on cerebrospinal fluid-methotrexate pharmacokinetics

A comparison between citrovorum factor (CF) and carboxypeptidase G1 (CPDG1) rescue with respect to cerebrospinal fluid (CSF)-methotrexate (MTX) disappearance was studied in a patient with recurrent medulloblastoma who had a ventriculoperitoneal shunt. CPDG1 rescue resulted in a prolonged CSF-MTX half-life of 16.5-23 hours in comparison with CF rescue where the CSF-MTX half-life was 6.5-7.2 hours. There was a positive clinical response measured by loss of bone pain, increased physical activity, and almost complete clearing of CSF blast cells. CPDG1 rescue after high-dose MTX may provide more intense and selective treatment for meningeal neoplasms.