Clinical data | |
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Other names | ALKS-33; RDC-0313; 3-Carboxamido-4-hydroxynaltrexone |
Routes of administration | By mouth |
Pharmacokinetic data | |
Elimination half-life | 7–9 hours [1] [2] |
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Chemical and physical data | |
Formula | C21H26N2O4 |
Molar mass | 370.449 g·mol−1 |
3D model (JSmol) | |
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Samidorphan (INN , USAN ) is an opioid antagonist that in the form of olanzapine/samidorphan (sold as Lybalvi) is used in the treatment of schizophrenia and bipolar disorder. [1] [3] [4] Samidorphan reduces the weight gain associated with olanzapine. [5] [6] Samidorphan is taken by mouth. [1] [3]
Samidorphan was under development as a standalone medication for various indications but has been discontinued. [7] Buprenorphine/samidorphan for the treatment of major depressive disorder was rejected by the US Food and Drug Administration (FDA) due to insufficient evidence of effectiveness, but remains in preregistration as of September 2021. [8] Development of baclofen/samidorphan has also been discontinued. [9]
Samidorphan has been investigated for the treatment of alcoholism and cocaine addiction by its developer, Alkermes, [10] [11] showing similar efficacy to naltrexone, but possibly with reduced side effects.
It has attracted much more attention as part of the combination product (buprenorphine/samidorphan), where samidorphan is combined with the mixed μ-opioid receptor (MOR) weak partial agonist and κ-opioid receptor (KOR) antagonist buprenorphine, as an antidepressant. Buprenorphine has shown antidepressant effects in some human studies, thought to be because of its antagonist effects at the KOR, but has not been further developed for this application because of its MOR agonist effects and consequent abuse potential. By combining buprenorphine with samidorphan to block the MOR agonist effects, the combination acts more like a selective KOR antagonist, and produces only antidepressant effects, without typical MOR effects such as euphoria or substance dependence being evident. [12] [13]
Samidorphan was also studied in combination with olanzapine, (olanzapine/samidorphan), for use in schizophrenia. [14] A Phase III study found that the addition of samidorphan to olanzapine significantly reduced weight gain compared to olanzapine alone, [15] and the combination was approved for the treatment of schizophrenia and bipolar disorder by the FDA in May 2021, under the brand name Lybalvi. [16] [17]
Side effects of samidorphan include somnolence and gastrointestinal disturbances among others. [1]
Receptor | Ki | EC50 | Emax | IC50 | Imax |
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MOR | 0.052 nM | – | 3.8% | 0.88 nM | 92% |
KOR | 0.23 nM | 3.3 nM | 36% | 38 nM | 57% |
DOR | 2.6 nM | 1.5 nM | 35% | 6.9 nM | 56% |
Samidorphan acts primarily as an antagonist or very weak partial agonist of the μ-opioid receptor (MOR) and to a lesser extent as a partial agonist of the κ-opioid receptor (KOR) and δ-opioid receptor (DOR). [1] [18] [19] In accordance with this profile, samidorphan has been observed to produce some side effects that are potentially consistent with activation of the KOR such as somnolence, sedation, dizziness, and hallucinations in some patients in clinical trials. [20]
The elimination half-life of samidorphan is 7 to 9 hours. [1] [2]
Samidorphan has its origins in academia where 8-carboxamidocyclazocine and naltrexone were utilized in its design and synthesis. [21]
Olanzapine, sold under the brand name Zyprexa among others, is an atypical antipsychotic primarily used to treat schizophrenia and bipolar disorder. It is also sometimes used off-label for treatment of chemotherapy-induced nausea and vomiting and as an appetite stimulant. For schizophrenia, it can be used for both new-onset disease and long-term maintenance. It is taken by mouth or by injection into a muscle.
Aripiprazole, sold under the brand names Abilify and Aristada, among others, is an atypical antipsychotic. It is primarily used in the treatment of schizophrenia, bipolar disorder, and irritability associated with autism spectrum disorder; other uses include as an add-on treatment in major depressive disorder and tic disorders. Aripiprazole is taken by mouth or via injection into a muscle. A Cochrane review found low-quality evidence of effectiveness in treating schizophrenia.
Buprenorphine, sold under the brand name Subutex among others, is an opioid used to treat opioid use disorder, acute pain, and chronic pain. It can be used under the tongue (sublingual), in the cheek (buccal), by injection, as a skin patch (transdermal), or as an implant. For opioid use disorder, the patient must have moderate opioid withdrawal symptoms before buprenorphine can be administered under direct observation of a health-care provider.
Naltrexone, sold under the brand name Revia among others, is a medication primarily used to manage alcohol use or opioid use disorder by reducing cravings and feelings of euphoria associated with substance use disorder. It has also been found effective in the treatment of other addictions and may be used for them off-label. An opioid-dependent person should not receive naltrexone before detoxification. It is taken orally or by injection into a muscle. Effects begin within 30 minutes, though a decreased desire for opioids may take a few weeks to occur.
Alkermesplc is a fully-integrated biopharmaceutical company that focuses on developing medicines for psychiatric and neurological disorders. The company was founded in 1987 by Michael Wall. In September 2011 Alkermes, Inc. merged with Elan Drug Technologies (EDT), the former drug formulation and manufacturing division of Élan Corporation, plc. The company is headquartered in Dublin, and has an R&D center in Waltham, Massachusetts, and a manufacturing facility in Wilmington, Ohio.
An opioid antagonist, or opioid receptor antagonist, is a receptor antagonist that acts on one or more of the opioid receptors.
The κ-opioid receptor or kappa opioid receptor, abbreviated KOR or KOP for its ligand ketazocine, is a G protein-coupled receptor that in humans is encoded by the OPRK1 gene. The KOR is coupled to the G protein Gi/G0 and is one of four related receptors that bind opioid-like compounds in the brain and are responsible for mediating the effects of these compounds. These effects include altering nociception, consciousness, motor control, and mood. Dysregulation of this receptor system has been implicated in alcohol and drug addiction.
Nalmefene, sold under the brand name Revex among others, is a medication that is used in the treatment of opioid overdose and alcohol dependence. Nalmefene belongs to the class of opioid antagonists and can be taken by mouth, administered by injection, or delivered through nasal administration.
Diprenorphine, also known as diprenorfin, is a non-selective, high-affinity, weak partial agonist of the μ- (MOR), κ- (KOR), and δ-opioid receptor (DOR) which is used in veterinary medicine as an opioid antagonist. It is used to reverse the effects of super-potent opioid analgesics such as etorphine and carfentanil that are used for tranquilizing large animals. The drug is not approved for use in humans.
Dezocine, sold under the brand name Dalgan, is an atypical opioid analgesic which is used in the treatment of pain. It is used by intravenous infusion and intramuscular injection.
JDTic is a selective, long-acting ("inactivating") antagonist of the κ-opioid receptor (KOR). JDTic is a 4-phenylpiperidine derivative, distantly related structurally to analgesics such as pethidine and ketobemidone, and more closely to the MOR antagonist alvimopan. In addition, it is structurally distinct from other KOR antagonists such as norbinaltorphimine. JDTic has been used to create crystal structures of KOR [ PDB: 4DJH, 6VI4].
Buprenorphine/samidorphan is a combination formulation of buprenorphine and samidorphan which is under development as an add on to antidepressants in treatment-resistant depression (TRD).
Aticaprant, also known by its developmental codes JNJ-67953964, CERC-501, and LY-2456302, is a κ-opioid receptor (KOR) antagonist which is under development for the treatment of major depressive disorder. A regulatory application for approval of the medication is expected to be submitted by 2025. Aticaprant is taken by mouth.
Buprenorphine/naltrexone is an experimental combination drug formulation of buprenorphine, a μ-opioid receptor (MOR) weak partial agonist and κ-opioid receptor (KOR) antagonist, and naltrexone, a MOR and KOR silent antagonist, which is under investigation for the potential treatment of psychiatric disorders. The combination of the two drugs is thought to result in a selective blockade of the KOR and hence fewer MOR activation-related concerns such as euphoria and opioid dependence. It has been found to produce antidepressant-like effects in mice and has recently been found to be effective in the treatment of cocaine dependence in a large clinical trial.
Nalodeine, also known more commonly as N-allylnorcodeine, is an opioid antagonist that was never marketed but is notable as the first opioid antagonist to be discovered. It was first reported in 1915 and was found to block the effects of morphine in animals. This was followed by the clinical introduction of nalorphine (N-allylnormorphine) in 1954, naloxone (N-allyloxymorphone) in 1960, and naltrexone (N-methylcyclopropyloxymorphone) in 1963. Nalmefene (6-desoxy-6-methylene-naltrexone), another structurally related opioid antagonist derivative, was also subsequently introduced, in 1996. In animals, nalodeine both reverses morphine- and heroin-induced respiratory depression and acts as a respiratory stimulant in its own right. Similarly to nalorphine, nalodeine has also been found to act as an agonist of the κ-opioid receptor.
Olanzapine/samidorphan, sold under the brand name Lybalvi, is a fixed-dose combination medication for the treatment of schizophrenia and bipolar I disorder. It contains olanzapine, an atypical antipsychotic, and samidorphan, an opioid antagonist. Samidorphan reduces the weight gain associated with olanzapine while still allowing olanzapine to exert its therapeutic effect. Although Lybalvi still produces transient weight gain of roughly 11 pounds, its metabolic profile is significantly lower than olanzapine alone. The formulation was approved for medical use in the United States in May 2021.
Peripherally acting μ-opioid receptor antagonists (PAMORAs) are a class of chemical compounds that are used to reverse adverse effects caused by opioids interacting with receptors outside the central nervous system (CNS), mainly those located in the gastrointestinal tract. PAMORAs are designed to specifically inhibit certain opioid receptors in the gastrointestinal tract and with limited ability to cross the blood–brain barrier. Therefore, PAMORAs do not affect the analgesic effects of opioids within the central nervous system.
Methoclocinnamox is a selective pseudo-irreversible partial agonist of the μ-opioid receptor (MOR). It shows a mixture of opioid agonist- and antagonist-like effects. The drug has long-lasting effects and is insurmountable by other MOR ligands.
PF-04455242 is an experimental κ-opioid receptor (KOR) antagonist which was under development by Pfizer for the treatment of bipolar depression but was never marketed. Its development was discontinued in early clinical trials. It is taken by mouth.