Lorcaserin for Cannabis Use Disorder

Cannabis use disorder (CUD) is a major public health problem associated with significant psychiatric and medical morbidity, poor performance, and legal consequences.4 4.2 million people in the United States meet criteria for CUD.5 15% of all admissions for substance abuse treatment were related to cannabis as the primary, presenting problem in 2014 and 86% of those admissions were referred for ambulatory care.6 Despite the large number of patients with CUD seeking outpatient treatment, the investigators have limited options available. While evidence-based practices (EBP), and specifically psychotherapies, have been studied to treat CUD and various approaches have been shown to have clinical utility,7-9 many patients have difficulty achieving significant reductions in their use or sustained abstinence.10 This is further complicated by patients' limited access to EBPs,11 frequent poor adherence by therapists in the community to EBP interventions,12-14 and challenges in treating CUD with EBPs when available in community settings.10 Finding effective medications for the treatment of CUD is essential. There are no FDA approved medications for CUD. A number of pharmacological treatment trials for CUD have been performed.1* While some agents have shown promise,15-17 no medication strategy has emerged as clearly efficacious in producing abstinence.1,18 As the changing legal landscape influences patients' goals for reductions in cannabis use as compared to abstinence only, and with increasing support from the research community, future studies need to identify medications that lead to reductions in cannabis use.

Impulsivity has been linked to the predisposition,19 severity,20 and poor treatment outcomes21, 22 in cannabis users and CUD, making it a prime pharmacology target. Notably, there is an entwined relationship between cannabis and impulsivity. Impulsivity as a neurobehavioral trait is associated with cannabis use,and acute and chronic use of cannabis has been shown to exacerbate impulsivity, with some mixed evidence likely attributable to diverse constructs of impulsivity used across studies. While the investigators may not be able to fully determine which came first—the impulsivity or the cannabis use, further research is needed to demonstrate whether reductions across constructs of impulsivity can lead to improvements in CUD, and vice versa. Over the last two decades, 5HT2C receptor agonists have been shown to alter neurobiological systems of addiction and relevant drug use behavior in the preclinical literature by increasing inhibitory control on mesolimibic dopamine processes and resultant incentive motivation based behaviors,23 both directly and indirectly, particularly with regards to their impact on reducing impulsivity.24 In 2012, lorcaserin, a selective 5HT2C receptor agonist, was approved by the FDA, allowing for clinical exploration of its role in the treatment of substance use disorders, including CUD.25 Recently, a fully powered clinical trial of lorcaserin for tobacco smoking cessation was positive.26 The primary purpose of this study is therefore to investigate the effect of lorcaserin on reductions in cannabis use and multiple constructs of impulsivity in outpatient treatment-seeking individuals with CUD.

Additionally, the investigators will make use of the technological application of ecological momentary assessments (EMA), to collect real-time data at key time intervals during the study on participants' use of cannabis and other substances in addition to measuring impulsive traits through self-initiated, fixed and random phone prompts. This will be a 13-week randomized, double-blind, placebo-controlled trial, with week 1 focused on baseline assessments of impulsivity (through EMA in vivo and at study visits), weeks 2-3 of medication lead-in, and week 4 targeting a reduced cannabis use/quit day through week 13. This "proof of concept" study will provide Dr. Brezing with training in randomized controlled trial operations, multiple constructs to measure impulsivity, utilization of technology as a measurement tool, and identification of outcomes that may prove important to reductions in cannabis use.

Primary Aims:

(Aim 1) Examine the effect of lorcaserin compared to placebo, on reductions in cannabis use among treatment-seeking outpatients with CUD, with the primary outcome measured by average weekly mean episodes of any cannabis use (including edibles, vaping, and other variable potency cannabinoid products) per day. (Aim 2) Examine the effect of lorcaserin compared to placebo on behavioral and self-report measures of impulsivity among individuals with CUD during the medication lead-in phase (weeks 2-3).

Secondary Aim: If the hypotheses of the Primary Aims are supported, the investigators will examine whether reductions in impulsivity (during weeks 2-3) mediates the effect of lorcaserin on cannabis use (during weeks 8-13).

Exploratory Aims: To explore the effect of lorcaserin compared to placebo on (1) drop-out rates, (2) time to discontinuation from study, (3) treatment adherence, and (4) nicotine use.