Funded Projects

Withdrawal symptoms associated with current opioid use disorder treatments, such as naltrexone or buprenorphine, can be serious obstacles to successful treatment. This project aims to develop a U.S. Food and Drug Administration-approved sedative medication (dexmedetomidine) as an under-the-tongue film to treat opioid withdrawal symptoms at doses that have minimal ill effects on blood pressure and heart rate. This research will compare the safety and efficacy of dexmedetomidine to lofexidine, which is currently approved to treat opioid withdrawal.

New medication treatment approaches are needed to help address the severe epidemic of opioid use disorder (OUD) and opioid overdose deaths in the U.S. Currently available medications, such as methadone, buprenorphine, and extended release injection naltrexone (XR-NTX; trade name: Vivitrol), are highly efficacious, but their effectiveness in practice is limited by poor adherence, with many patients stopping treatment prematurely and relapsing. The goal of this proposal is to develop an innovative long-acting subcutaneous implanted formulation of naltrexone, the O’Neil Long-Acting Naltrexone Implant (OLANI), toward FDA approval. Expected to produce naltrexone blood levels sufficient to block the effects of opioids for 6 months after implant, OLANI circumvents the need for adherence to monthly injections with XR-NTX and could represent an important new addition to the medical armamentarium for treatment of OUD.

There is a need for pharmacologic treatment options for opioid use disorder (OUD) that do not pose addiction liability and do not require complete withdrawal from opioids prior to treatment. Nonclinical studies support a role for the orexin system in drug seeking; compounds that selectively block signaling at the orexin-1 receptor (OX1R) reduce drug use. C4X3256, a non-opioid, highly selective OX1R antagonist, has a long residence time at the OX1R along with reduced intravenous self-administration and cue-induced reinstatement in animal models of nicotine addiction, suggesting it could be an addiction treatment. Proposed studies will move C4X3256 from preclinical development through Phase I testing in subjects with OUD. The clinical, preclinical, and supporting pharmaceutical development studies proposed will allow C4X3256 to move to Phase II studies.

Extended-release naltrexone (XR-NTX) reduces overdose risk; however, transitioning to XR-NTX requires detoxification, which is a major hurdle. Non-opioid detoxification with an alpha-2 adrenergic receptor agonist, such as lofexidine, may shorten detoxification time, but it does not reduce the subjective effects of withdrawal. Pregabalin potentiates the activity of glutamic acid decarboxylase, inhibits calcium influx and release of excitatory neurotransmitters, raises GABA levels, and is approved for neuropathic pain, for fibromyalgia, and as an adjunctive therapy for adults with partial onset seizures. The study will test whether pregabalin can be combined with lofexidine to better reduce the subjective effects of opioid withdrawal than lofexidine alone and increase the proportion of patients that transition to XR-NTX. Such a dosing combination could lower the detoxification hurdle for patients who are interested in antagonist treatment or who are in settings where it is unavailable or difficult to access.

The adverse effects of morphine and other mu-opioid receptor (MOR) agonists are linked to the ?-arrestin pathway, while analgesia is tied to the G-protein pathway. Pathway specific or “biased” drug development can target G-protein specific agonists that avoid the negative consequences of ?-arrestin signaling activation and produce analgesia. Highly “biased” MOR agonists have promise as effective analgesics but devoid of opioid-induced adverse effects. Preclinical studies compared two compounds, MEB-1166 and MEB-1170, against Oliceridine and morphine. Both compounds displayed no respiratory depression, even at high doses, while morphine and Oliceridine significantly reduced respiratory function. In contrast to morphine, neither MEB-1166 nor MEB-1170 produced conditioned place preference, suggesting an absence of abuse liability. This study will characterize the pharmaceutical and pharmacological profiles and perform liability studies for these compounds.

Chronic pain affects an estimated 100 million Americans, or one third of the U.S. population, and it is the primary reason Americans are on disability. Although many treatments are available for pain, the most potent class of analgesics relies on opioid analogs, whose limitations and well-known adverse effects have contributed to the present opioid crisis. New pharmacotherapies for pain management are sorely needed. MTX1604, a synthetic endomorphin analog, has emerged as a highly effective analgesic that exhibits reduced reward potential and respiratory suppression, and a robust duration of efficacy in a variety of validated animal models of acute, neuropathic, inflammatory, post-operative, and visceral pain. This project will generate additional preclinical characterization data of MTX1604 and advance clinical development toward FDA approval. If successful, this medication development project could offer patients a novel non-addictive, potent, and safe analgesic and thus have a direct impact on the opioid crisis.

Neurostimulation techniques, such as transcranial direct current stimulation (tDCS), have been used as interventions for substance use disorders. This is a supplement to the currently NIDA-funded UG3 DA047793, “tDCS to Decrease Opioid Relapse,” which will measure behavioral and brain responses following tDCS stimulation delivered during tasks that use a particular brain network involved in cognitive control, and utilizing FMRI to assess the effects. This supplement allows the researchers to add an EEG measurement to the study, to get a complete picture of how tDCS might affect the function of key brain networks in ways that could be helpful for SUDs.

This U54 Center will use translational research from brain to bedside as a tool for medication development in cocaine use disorder. Preclinical and early phase I clinical PK/PD data will provide information for go/no-go decisions on phase II–III clinical trials with medications that show promise for cocaine use disorder. The overall goal of this research is to create a center that can provide important preclinical and early phase I clinical data to NIDA and pharmaceutical industry partners on novel compounds for cocaine use disorder. The aims related to the theme of the center will be achieved through two cores and three projects: The Administrative Core serves as a general resource for the other projects and the Educational Core, including oversight of fiscal and compliance matters, and will oversee interactions with outside entities, including NIDA and the pharmaceutical industry. The Educational Core will focus on training translational researchers for medication development for addictions across the two institutions.

There is a need to develop a mu-opioid receptor (MOR) treatment with enhanced therapeutic effects and reduced undesirable effects. Recently, several highly selective and potent MOR modulators have been identified as novel leads for opioid use disorder treatment. They all showed more promising pharmacological profiles compared to other known drugs in this category. The current proposal will focus on further development of these leads for preclinical IND-enabling studies and dynamic drug discovery and development pipeline construction. This project plans to further validate therapeutic profiles of the current leads with self-administration and pharmacokinetic studies and expand the small-molecule library to build a dynamic drug discovery and development pipeline. Preclinical IND-enabling studies on the identified lead(s) will be conducted, and in vivo pharmacokinetics and pharmacodynamics profiles of the new hits will be compared with current leads to define the next generation of lead compound(s).

Fentanyl and its analogs are synthetic opioids that are 100 to 10,000 times more potent than morphine. Overdose from these opioids is extremely dangerous due to their ultra-potency and longer half-life than naloxone, the front-line treatment for fentanyl overdose. This research study will develop novel mu opioid receptor antagonists that bind to the same receptor as the opioid drugs and specifically counteract fentanyl and its analogs, thereby reversing the drugs’ acute toxicity more effectively and with fewer side effects than current treatments. The researchers will characterize novel fentanyl derivatives, identify promising compounds, and pursue preclinical development of these compounds as novel reversal agents against the acute toxicity of fentanyl. The goal is to file an Investigational New Drug application with the U.S. Food and Drug Administration.

MCAM is a novel opioid antagonist that can be used for opioid overdose reversal and has advantages over naloxone, including a pseudo-irreversible interaction with the ?-opioid receptor and a longer duration of action. Studies in animal models demonstrate MCAM’s long duration of action against the reinforcing and respiratory-depressant effects of remifentanil and heroin, indicating that could be a better treatment option for opioid use disorder. This project studies the pharmacodynamics of MCAM through animal toxicity and safety studies to establish the necessary and sufficient conditions from which to establish MCAM’s safety and antagonist activity in animals and humans. MCAM may be able to prevent all actions of any ?-receptor opioid drug in humans for a longer period of time than any other antagonist given acutely.

Opioids remain the gold standard for treating moderate to severe pain, but their use is limited by numerous adverse effects, including tolerance, dependence, abuse, and overdose. Adverse effects could be avoided by combining an opioid with another drug, such that smaller doses of the opioid (in combination with another drug) produce the desired therapeutic effect. Direct-acting serotonin type 2 (5-HT2) receptor agonists interact in a synergistic manner with the opioid morphine to produce antinociceptive effects, suggesting a 5-HT2 receptor agonist could be combined with small amounts of an opioid to treat pain, thereby lowering the risk associated with larger doses. Unfortunately, very little is known about interactions between 5-HT2 receptor agonists and other opioids. The proposed studies will evaluate the therapeutic potential of mixtures of opioids and 5-HT2 receptor agonists using highly translatable and well-established procedures to characterize the antinociceptive, respiratory-depressant (overdose), positive-reinforcing (leading to misuse), and discriminative-stimulus (subjective) effects of drug mixtures as well as the impact of chronic treatment on the development of tolerance to and physical dependence on opioids. If successful, these studies will provide proof-of-concept for this innovative approach to pain treatment and evaluate the utility of targeting 5-HT receptors for analgesic drug development.