Glioblastoma multiforme (GBM) has a poor prognosis with an overall survival of 14-15 months following surgery, radiation and chemotherapy using temozolomide (TMZ). A major problem is that the tumors acquire resistance to therapy. In an effort to improve the therapeutic efficacy of TMZ, we performed a genome-wide RNA interference (RNAi) synthetic lethality screen to establish a functional gene signature for TMZ sensitivity in human GBM cells. We then queried the Connectivity Map database to search for drugs that would induce corresponding changes in gene expression. By this approach we identified several potential pharmacological sensitizers to TMZ, where the most potent drug was the established antipsychotic agent Thioridazine, which significantly improved TMZ sensitivity while not demonstrating any significant toxicity alone. Mechanistically, we show that the specific chemosensitizing effect of Thioridazine is mediated by impairing autophagy, thereby preventing adaptive metabolic alterations associated with TMZ resistance. Moreover, we demonstrate that Thioridazine inhibits late-stage autophagy by impairing fusion between autophagosomes and lysosomes. Finally, Thioridazine in combination with TMZ significantly inhibits brain tumor growth in vivo, demonstrating the potential clinical benefits of compounds targeting the autophagy-lysosome pathway. Our study emphasizes the feasibility of exploiting drug repurposing for the design of novel therapeutic strategies for GBM. This article is protected by copyright. All rights reserved.

Here, an optical sensor with specific binding sites for sensitive and selective detection of thioridazine hydrochloride (THZ) was prepared. The optosensor was developed based on ZnO quantum dots (QDs) coated with molecularly imprinted polymers (MIPs). Initially, ZnO quantum dots (QDs) were synthesized by precipitation from Zn(CH3COO)2 and NaOH then, reverse microemulsion method was applied for fixing the MIPs layer on the surface of QDs. It was perceived that the fluorescence intensity of the QDs-MIPs quenched with increasing THZ concentration. Several parameters affect the optical sensor response were studied and optimized. Under the optimal conditions, THZ could be determined with a linear dynamic range of 4-120 nmol L-1 and with a low detection limit of 0.43 nmol L-1. The relative standard deviations for 25 and 60 nmol L-1 of THZ were obtained as 4.9% and 3.1%, respectively (three times measurement). High selectivity, simplicity, and cost-efficient for THZ measurement are the most important advantages of the fluorimetric sensor.

Thioridazine is an antipsychotic that has been shown to induce cell death and inhibit self-renewal in a broad spectrum of cancer cells. The mechanisms by which these effects are mediated are currently unknown but are presumed to result from the inhibition of dopamine receptor 2 (DRD2). Here we show that the self-renewal of several, but not all, triple-negative breast cancer cell lines is inhibited by thioridazine. The inhibition of self-renewal by thioridazine in these cells is mediated by DRD2 inhibition. Further, we demonstrate that DRD2 promotes self-renewal in these cells via a STAT3- and IL-6-dependent mechanism. We also show that thioridazine induces a G1 arrest and a loss in cell viability in all tested cell lines. However, the reduction in proliferation and cell viability is independent of DRD2 and STAT3. Our results indicate that although there are cell types in which DRD2 inhibition results in inhibition of STAT3 and self-renewal, the dramatic block in cancer cell proliferation across many cell lines caused by thioridazine treatment is independent of DRD2 inhibition.

Nuclear factor-kB (NF-kB) is a crucial transcription factor in the signal transduction cascade of the inflammatory signaling. Activation of NF-κB depends on the phosphorylation of IκBα by IκB kinase (IKKβ) followed by subsequent ubiquitination and degradation. This leads to the nuclear translocation of the p50- p65 subunits of NF-κB, and further triggers pro-inflammatory cytokine gene expression. Thus, in the need of a more effective therapy for the treatment of inflammatory diseases, specific inhibition of IKKβ represents a rational alternative strategy to the current therapies. A computer-aided drug identification protocol was followed to identify novel IKKβ inhibitors from a database of over 1500 Food and Drug Administration (FDA) drugs. The best scoring compounds were compared with the already known high-potency IKKβ inhibitors for their ability to bind and inhibit IKKβ by evaluating their docking energy. Finally, Thioridazinehydrochloride (TDZ), a potent antipsychotic drug against Schizophrenia was selected and its efficiency in inhibiting IκBα protein degradation and NF-κB activation was experimentally validated. Our study has demonstrated that TDZ blocks IκBα protein degradation and subsequent NF-κB activation to inhibit inflammation. Thus, it is a potential repurposed drug against inflammation.

We completed a phase 1 dose-escalation trial to evaluate the safety of a dopamine receptor D2 (DRD2) antagonist thioridazine (TDZ), in combination with cytarabine. Thirteen patients 55 years and older with relapsed or refractory acute myeloid leukemia (AML) were enrolled. Oral TDZ was administered at 3 dose levels: 25 mg (n = 6), 50 mg (n = 4), or 100 mg (n = 3) every 6 hours for 21 days. Intermediate-dose cytarabine was administered on days 6 to 10. Dose-limiting toxicities (DLTs) included grade 3 QTc interval prolongation in 1 patient at 25 mg TDZ and neurological events in 2 patients at 100 mg TDZ (gait disturbance, depressed consciousness, and dizziness). At the 50-mg TDZ dose, the sum of circulating DRD2 antagonist levels approached a concentration of 10 μM, a level noted to be selectively active against human AML in vitro. Eleven of 13 patients completed a 5-day lead-in with TDZ, of which 6 received TDZ with hydroxyurea and 5 received TDZ alone. During this period, 8 patients demonstrated a 19% to 55% reduction in blast levels, whereas 3 patients displayed progressive disease. The extent of blast reduction during this 5-day interval was associated with the expression of the putative TDZ target receptor DRD2 on leukemic cells. These preliminary results suggest that DRD2 represents a potential therapeutic target for AML disease. Future studies are required to corroborate these observations, including the use of modified DRD2 antagonists with improved tolerability in AML patients. This trial was registered at www.clinicaltrials.gov as #NCT02096289.

Staphylococcus aureus has developed resistance towards the most commonly used anti-staphylococcal antibiotics. Therefore, there is an urgent need to find new treatment opportunities. A new approach relies on the use of helper compounds, which are able to potentiate the effect of antibiotics. A well-studied helper compound is thioridazine, which potentiates the effect of the β-lactam antibiotic dicloxacillin against Methicillin-resistant Staphylococcus aureus (MRSA). In order to identify thioridazine's mechanism of action and how it potentiates the effect of dicloxacillin, we generated thioridazine resistant strains of MRSA USA300 by serial passage experiments. Selected strains were whole-genome sequenced to find mutations causing thioridazine resistance. Genes observed to be mutated were attempted deleted in MRSA USA300. The cls gene encoding a cardiolipin synthase important for synthesis of the membrane lipid cardiolipin was found to be mutated in thioridazine resistant strains. Deletion of this gene resulted in a two-fold increased Minimum inhibitory concentrations (MIC) value for thioridazine compared to the wild type and decreased susceptibility similar to the thioridazine resistant strains. Since cardiolipin likely plays a role in resistance towards thioridazine, it might also be important for the mechanism of action behind the potentiating effect of thioridazine. TDZ is known to intercalate into the membrane and we show here that TDZ can depolarize the plasma membrane. However, our results indicate that the membrane potential reducing effect of TDZ is independent of the resistance mechanism.

Eleven clinical Klebsiella pneumoniae fluoroquinolone-resistant isolates were tested to access the potential of adjuvant therapies to reduce antimicrobial resistance using fixed concentrations of the chemosensitizers chlorpromazine (CPZ), thioridazine (TZ), phenylalanine-arginine-β-naphthylamide (PAβN), and 1-(1-naphthylmethyl)-piperazine-(NMP) with varying concentrations of antimicrobial agents nalidixic acid (NAL), ciprofloxacin (CIP), moxifloxacin (MXF), tetracycline (TET), and chloramphenicol (CHL). Ethidium bromide dye was used together with the chemosensitizers to investigate permeabilization effects. NMP was assessed for its capacity to reduce the mass of biofilm alone and in combination with CIP and MXF. Of the selected chemosensitizers, NMP exhibited the greatest capacity to reverse resistance and inhibit efflux, based on the concentrations tested. Susceptibility to antimicrobial agents including (fluoro)quinolones, TET, and CHL were found to be increased in the presence of NMP, in a concentration-dependent manner. PAβN also demonstrated similar effects when combined with the chemosensitizers tested. In the case of half of the isolates studied, NMP alone reduced preformed biofilm biomass. Combinations of latter along with CIP or MXF were also found to reduce the mass of preformed biofilm, in the case of only some of the bacterial isolates. The capacity of NMP to reduce antimicrobial resistance could be of relevance as a strategy to limit bacterial colonization on abiotic surfaces.

Because there is no published experience with thioridazine during breastfeeding, an alternate drug may be preferred, especially while nursing a newborn or preterm infant.

Because there is no published experience with mesoridazine during breastfeeding, other antipsychotic agents are preferred.