A Pilot Study Assessing the Safety and Latency Reversing Activity of Disulfiram in HIV-1-Infected Adults on Antiretroviral Therapy

(See the Editorial Commentary by Tolstrup on pages 891–2.) Combination antiretroviral therapy (ART) has dramatically altered the natural history of human immunodeficiency virus type 1 (HIV-1) infection for most infected individuals with access to treatment [1]. ART reduces plasma HIV-1 RNA to below the limit of clinical detection. It was initially hoped that the virus could be eradicated with 2–3 years of effective ART treatment [2]; however, a latent form of HIV-1 exists in vivo. Stably integrated, transcriptionally silent viral genomes persist in long-lived resting memory CD4+ T cells [3–7]. The stability of this latent reservoir is the major barrier to eradication of HIV-1 [4, 7, 8], requiring patients to remain on ART indefinitely. Given the concern for adverse effects of ART, as well as the financial burden of treatment and need for adherence, strategies to eliminate the latent reservoir have become an urgent research priority. One eradication strategy that has attracted significant attention involves targeting the latent reservoir through the use of drugs that reverse latency without inducing global T-cell activation [9, 10]. This strategy is based on the hypothesis that cells in which latency has been reversed will be targeted by cytolytic CD8+ T cells or will die by viral cytopathic effects [11]. Previous attempts to target latently infected cells by inducing global T-cell activation have proven too toxic for use in humans [12–14]. Subsequent research has focused on identifying compounds that will induce HIV-1 gene expression in latently infected resting CD4+ T cells without activating the cell itself [15]. To this end, several in vitro models have been described that appear to recapitulate the phenotype of HIV-1 latency in resting CD4+ T cells [16–18]. We have described one such model that makes use of Bcl-2–transduced primary CD4+ T cells [16] and performed a high-throughput screen to identify compounds that induce viral gene expression without triggering cellular activation [19]. One hit from this screen was disulfiram, a US Food and Drug Administration (FDA)–approved drug used to treat alcoholism [20]. Disulfiram (bis [diethylthiocarbamoyl] disulphide) inhibits aldehyde dehydrogenase, resulting in an increased concentration of acetaldehyde when alcohol is consumed [21]. This leads to an unpleasant systemic reaction that serves as a deterrent to alcohol consumption [22, 23]. Disulfiram has been in clinical use for several decades [24] and has a well-characterized safety profile [25, 26]. The molecular mechanism of in vitro disulfiram-induced HIV-1 latency reactivation is unclear. Disulfiram undergoes a complex metabolism [26] with the downstream metabolite N,N-diethylthiolcarbamate sulfoxide (DETC-MeSO) primarily responsible for aldehyde dehydrogenase inhibition and resultant clinical effect [27]. In contrast, reactivation of latent HIV-1 in vitro occurs only with the parent compound and first metabolite, diethyldithiocarbamic acid (DDTC) [19]. Subsequent metabolites, including diethyldithiocarbamate methyl ester (DDTC-Me), induce no appreciable HIV-1 reactivation [19]. A recent report found that intracellular depletion of the phosphate and tensin homolog (PTEN) protein by disulfiram led to upregulation of the Akt signaling pathway, resulting in HIV-1 gene transcription in the U1 HIV-1–infected monocyte cell line [28]. This potential molecular mechanism of disulfiram activity is under further investigation. We describe a pilot trial in which we administered 500 mg of disulfiram daily for 14 days to HIV-1–infected patients who had suppression of viremia on ART to determine whether this compound could reactivate latent HIV-1 from resting memory CD4+ T cells. This FDA-approved dose was selected to achieve in vivo concentrations of disulfiram and its metabolites comparable to concentrations that resulted in latency reversal activity in vitro [19]. The safety of higher doses is unknown. We hypothesized that disulfiram treatment would be safe and would result in a transient increase in residual viremia due to virus release from latently infected resting CD4+ T cells and a measureable decline in the size of the latent reservoir.