Mitapivat (AG-348; PKM2 activator 1020) is a novel, first-in-class oral small molecule allosteric activator of the pyruvate kinase enzyme. Mitapivat has been shown to significantly upregulate both wild-type and numerous mutant forms of erythrocyte pyruvate kinase (PKR), increasing adenosine triphosphate (ATP) production and reducing levels of 2,3-diphosphoglycerate. Given this mechanism, mitapivat has been evaluated in clinical trials in a wide range of hereditary hemolytic anemias, including pyruvate kinase deficiency (PKD), sickle cell disease, and the thalassemias. Mitapivat was approved for the treatment of hemolytic anemia in adults with pyruvate kinase (PK) deficiency in the United States in February 2022, and in the European Union in November 2022.

Ganaxolone (3alpha-hydroxy-3beta-methyl-5alpha-pregnan-20-one) (GNX) is the 3beta-methylated synthetic analog of allopregnanolone; it belongs to a class of compounds referred to as neurosteroids. GNX is an allosteric modulator of GABA(A) receptors acting through binding sites which are distinct from the benzodiazepine binding site. It has activity in a broad range of animal models of epilepsy. GNX has been shown to be well tolerated in adults and children. In early phase II studies, GNX has been shown to have activity in adult patients with partial-onset seizures and epileptic children with history of infantile spasms. It is currently undergoing further development in infants with newly diagnosed infantile spasms, in women with catamenial epilepsy, and in adults with refractory partial-onset seizures. Ganaxolone is a CNS-selective GABAA modulator being developed in three different dose forms (IV, capsule, and liquid) intended to maximize therapeutic reach to adult and pediatric patients in both acute and chronic care settings.Ganaxolone is a synthetic analog of endogenous allopregnanolone, which has been shown to be an effective anticonvulsant by restoring electrical balance to the seizing brain. While allopregnanolone’s anticonvulsant and anti-anxiety activities are well documented, allopregnanolone has the potential to convert back to its metabolic precursor progesterone, which could lead to hormonal side effects. Ganaxolone has been designed with an added methyl group that prevents back conversion to an active steroid which unlocks ganaxolone’s potential for chronic use. In preclinical studies, ganaxolone exhibited potency and efficacy comparable to allopregnanolone. Both ganaxolone and allopregnanolone bind to GABAA at the synaptic and extrasynaptic binding sites. Activity with extrasynaptic GABAA receptors are of particular importance for treating patients who developed tolerance to benzodiazepines and barbiturates. Ganaxolone binds to the GABAA receptors, which opens the pore to allow chloride ions to move into the postsynaptic neuron, leading to the inhibition of neurotransmission.

Carglumic acid is a Carbamoyl Phosphate Synthetase 1 (CPS 1) allosteric modulator. CPS1 is found in the mitochondria and is the first enzyme of the urea cycle, which converts ammonia into urea. Carglumic acid acts as a replacement for NAG in NAGS deficiency patients by activating CPS1 but it does not help to regulate the urea cycle. Carglumic acid under the trade name Carbaglu indicated as adjunctive therapy for the treatment of acute hyperammonemia due to the deficiency of the hepatic enzyme N-acetylglutamate synthase (NAGS). In addition, as maintenance therapy for the treatment of chronic hyperammonemia due to the deficiency of the hepatic enzyme N-acetylglutamate synthase (NAGS). This rare genetic disorder results in elevated blood levels of ammonia, which can eventually cross the blood–brain barrier and cause neurologic problems, cerebral edema, coma, and death.

Acamprosate was the third medication, after disulfiram and naltrexone, to receive U.S. Food and Drug Administration (FDA) approval for postwithdrawal maintenance of alcohol abstinence. The French pharmaceutical company Laboratoires Meram began clinical development and testing of acamprosate in 1982. From 1982 to 1988, acamprosate was tested for safety and for efficacy as a treatment for alcohol dependence. Based on these studies, in 1989 Laboratoires Meram was granted marketing authorization for acamprosate in France under the trade name Aotal®. Since then, acamprosate has been extensively used and studied throughout Europe and, subsequently, in the United States. Although acamprosate has been used in Europe for more than 20 years, it was not approved by FDA until July 2004. Acamprosate became available for use in the United States in January 2005, under the trade name Campral® Delayed-Release Tablets (Merck Santé, a subsidiary of Merck KGaA, Darmstadt, Germany). Campral is currently marketed in the United States by Forest Pharmaceuticals. The mechanism of action of acamprosate in maintenance of alcohol abstinence is not completely understood. Chronic alcohol exposure is hypothesized to alter the normal balance between neuronal excitation and inhibition. in vitro and in vivo studies in animals have provided evidence to suggest acamprosate may interact with glutamate and GABA neurotransmitter systems centrally, and has led to the hypothesis that acamprosate restores this balance. It seems to inhibit NMDA receptors while activating GABA receptors.

Cinacalcet is a positive allosteric modulator of calcium sensing receptor. The drug is approved by FDA (Sensipar trade name) and used for the treatment of secondary hyperparathyroidism in adult patients with chronic kidney disease on dialysis; hypercalcemia in adult patients with parathyroid carcinoma; hypercalcemia in adult patients with primary hyperparathyroidism who are unable to undergo parathyroidectomy.

Topiramate is an anticonvulsant indicated in the treatment of epilepsy and migraine. Topiramate enhances GABA-activated chloride channels. In addition, topiramate inhibits excitatory neurotransmission, through actions on kainate and AMPA receptors. There is evidence that topiramate has a specific effect on GluR5 kainate receptors. It is also an inhibitor of carbonic anhydrase, particular subtypes II and IV, but this action is weak and unlikely to be related to its anticonvulsant actions, but may account for the bad taste and the development of renal stones seen during treatment. Its possible effect as a mood stabilizer seems to occur before anticonvulsant qualities at lower dosages. Topiramate inhibits maximal electroshock and pentylenetetrazol-induced seizures as well as partial and secundarily generalized tonic-clonic seizures in the kindling model, findings predective of a broad spectrum of antiseizure activities clinically. The precise mechanism of action of topiramate is not known. However, studies have shown that topiramate blocks the action potentials elicited repetitively by a sustained depolarization of the neurons in a time-dependent manner, suggesting a state-dependent sodium channel blocking action. Topiramate also augments the activity of the neurotransmitter gamma-aminobutyrate (GABA) at some subtypes of the GABAAreceptor (controls an integral chloride channel), indicating a possible mechanism through potentiation of the activity of GABA. Topiramate also demonstrates antagonism of the AMPA/kainate subtype of the glutamate excitatory amino acid receptor. It also inhibits carbonic anhydrase (particularly isozymes II and IV), but this action is weak and unlikely to be related to its anticonvulsant actions. Topiramate is used for the treatment and control of partial seizures and severe tonic-clonic (grand mal) seizures and also for the prevention of migraine headaches. In children it is also used for treatment of Lennox-Gastaut syndrome. Topiramate is sold under the brand name Topamax. A combination product containing phentermine and topiramate extended-release called QSYMIA® is indicated for the management of obesity.

Zolpidem is usually used for the treatment of insomnia as a hypnotic drug. It was also suggested to be effective in the treatment of dystonia in some studies. Zolpidem can be one of useful alternative pharmacological treatments for blepharospasm. Zolpidem interacts with a GABA-BZ receptor complex and shares some of the pharmacological properties of the benzodiazepines. In contrast to the benzodiazepines, which non-selectively bind to and activate all BZ receptor subtypes, zolpidem in vitro binds the BZ1 receptor preferentially with a high affinity ratio of the α1/α5 subunits. This selective binding of zolpidem on the BZ1 receptor is not absolute, but it may explain the relative absence of myorelaxant and anticonvulsant effects in animal studies as well as the preservation of deep sleep in human studies of zolpidem tartrate at hypnotic doses.

Midazolam, previously marketed under the trade name Versed, is a medication used for anesthesia, procedural sedation, trouble sleeping, and severe agitation. Midazolam is a short-acting benzodiazepine central nervous system (CNS) depressant. Pharmacodynamic properties of midazolam and its metabolites, which are similar to those of other benzodiazepines, include sedative, anxiolytic, amnesic and hypnotic activities. Benzodiazepine pharmacologic effects appear to result from reversible interactions with the γ-amino butyric acid (GABA) benzodiazepine receptor in the CNS, the major inhibitory neurotransmitter in the central nervous system. The action of midazolam is readily reversed by the benzodiazepine receptor antagonist, flumazenil. Data from published reports of studies in pediatric patients clearly demonstrate that oral midazolam provides safe and effective sedation and anxiolysis prior to surgical procedures that require anesthesia as well as before other procedures that require sedation but may not require anesthesia. The most commonly reported effective doses range from 0.25 to 1 mg/kg in children (6 months to <16 years). The single most commonly reported effective dose is 0.5 mg/kg. Time to onset of effect is most frequently reported as 10 to 20 minutes. The effects of midazolam on the CNS are dependent on the dose administered, the route of administration, and the presence or absence of other medications.

Quazepam is indicated for the treatment of insomnia characterized by difficulty in falling asleep, frequent nocturnal awakenings, and/or early morning awakenings. Quazepam interact preferentially with the benzodiazepine-1 (BZ1) receptors. Most common adverse reactions (>1%): drowsiness, headache, fatigue, dizziness, dry mouth, dyspepsia. Downward of CAN depressant dose adjustment may be necessary due to additive effects.

Alprazolam, a benzodiazepine, is used to treat panic disorder and anxiety disorder. Unlike chlordiazepoxide, clorazepate, and prazepam, alprazolam has a shorter half-life and metabolites with minimal activity. Alprazolam may have significant drug interactions involving the hepatic cytochrome P-450 3A4 isoenzyme. Clinically, all benzodiazepines cause a dose-related central nervous system depressant activity varying from mild impairment of task performance to hypnosis. Unlike other benzodiazepines, alprazolam may also have some antidepressant activity, although clinical evidence of this is lacking. CNS agents of the 1,4 benzodiazepine class presumably exert their effects by binding at stereo specific receptors at several sites within the central nervous system. Their exact mechanism of action is unknown. Benzodiazepines bind nonspecifically to benzodiazepine receptors BNZ1, which mediates sleep, and BNZ2, which affects muscle relaxation, anticonvulsant activity, motor coordination, and memory. As benzodiazepine receptors are thought to be coupled to gamma-aminobutyric acid-A (GABAA) receptors, this enhances the effects of GABA by increasing GABA affinity for the GABA receptor. Binding of the inhibitory neurotransmitter GABA to the site opens the chloride channel, resulting in a hyperpolarized cell membrane that prevents further excitation of the cell.