Ampakine

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CX-516, one of the earliest and a prototypical ampakine. CX-516-2D-skeletal.svg
CX-516, one of the earliest and a prototypical ampakine.

Ampakines or AMPAkines are a subgroup of AMPA receptor positive allosteric modulators with a benzamide or closely related chemical structure. [1] [2] They are also known as "CX compounds". [1] Ampakines take their name from the AMPA receptor (AMPAR), a type of ionotropic glutamate receptor with which the ampakines interact and act as positive allosteric modulators (PAMs) of. [1] Although all ampakines are AMPAR PAMs, not all AMPAR PAMs are ampakines.

Contents

They are currently being investigated as potential treatment for a range of conditions involving mental disability and disturbances such as Alzheimer's disease, Parkinson's disease, schizophrenia, treatment-resistant depression (TRD) or neurological disorders such as attention deficit hyperactivity disorder (ADHD), among others. [1]

More recently developed ampakine compounds are much more potent and selective for the AMPA receptor target, and while none of the newer selective ampakine compounds have yet come onto the market, various ampakines are in clinical trials. [1]

Development

Cortex Pharmaceutical ampakines CX-546, CX-516, and CX-614. Cortex pharm AMPAkines.svg
Cortex Pharmaceutical ampakines CX-546, CX-516, and CX-614.

A wide range of ampakines have been developed by RespireRx, which hold patents covering most medical uses of this class of drugs. The best known compounds that have come out of the RespireRx drug development program are CX-516 (Ampalex), CX-546, CX-614, CX-691 (farampator), and CX-717. ORG-26576 was developed by RespireRx but then licensed to Organon for development.

Several other compounds such as CX-701, CX-1739, CX-1763 and CX-1837 have also been announced as being under current investigation, and while little information has yet been released about them, CX-1739 is believed to be the most potent compound in this class to date, reportedly some 5x the potency of CX-717.

Presently, CX717 is in phase II clinical trials as a possible non-stimulant pharmacotherapy in the treatment of ADHD. [3] As the AMPA receptors also mediate respiratory drive, CX717 is also being investigated as a therapy in opioid-induced respiratory depression and spinal-cord injury.

Mechanism of action

Ampakines work by allosterically binding to a type of ionotropic glutamate receptor, called AMPA receptors.

The ampakines are mostly low-impact AMPAR PAMs, though with some exceptions, such as tulrampator (S-47445, CX-1632).

Side effects

Few side effects have been determined, but an ampakine called farampator (CX-691) has side effects including headache, drowsiness, nausea, and impaired episodic memory. [4]

Medical applications

An ampakine called CX456 has been proposed as a treatment for Rett syndrome, after favorable testing in an animal model. [5]

Ampakines have been investigated by DARPA to treat sleep deprivation-induced cognitive decline. [6]

See also

Related Research Articles

<span class="mw-page-title-main">AMPA receptor</span> Transmembrane protein family

The α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (also known as AMPA receptor, AMPAR, or quisqualate receptor) is an ionotropic transmembrane receptor for glutamate (iGluR) and predominantly Na+ ion channel that mediates fast synaptic transmission in the central nervous system (CNS). It has been traditionally classified as a non-NMDA-type receptor, along with the kainate receptor. Its name is derived from its ability to be activated by the artificial glutamate analog AMPA. The receptor was first named the "quisqualate receptor" by Watkins and colleagues after a naturally occurring agonist quisqualate and was only later given the label "AMPA receptor" after the selective agonist developed by Tage Honore and colleagues at the Royal Danish School of Pharmacy in Copenhagen. The GRIA2-encoded AMPA receptor ligand binding core (GluA2 LBD) was the first glutamate receptor ion channel domain to be crystallized.

<span class="mw-page-title-main">Ligand-gated ion channel</span> Type of ion channel transmembrane protein

Ligand-gated ion channels (LICs, LGIC), also commonly referred to as ionotropic receptors, are a group of transmembrane ion-channel proteins which open to allow ions such as Na+, K+, Ca2+, and/or Cl to pass through the membrane in response to the binding of a chemical messenger (i.e. a ligand), such as a neurotransmitter.

<span class="mw-page-title-main">CX717</span> Ampakine

CX717 is an ampakine compound created by Christopher Marrs and Gary Rogers in 1996 at Cortex Pharmaceuticals. It affects the neurotransmitter glutamate, with trials showing the drug improves cognitive functioning and memory.

Racetams are a class of drugs that share a pyrrolidone nucleus. Some, such as piracetam, aniracetam, oxiracetam, pramiracetam and phenylpiracetam are considered nootropics. Others such as levetiracetam, brivaracetam, and seletracetam are anticonvulsants.

<span class="mw-page-title-main">Glutamate receptor</span> Cell-surface proteins that bind glutamate and trigger changes which influence the behavior of cells

Glutamate receptors are synaptic and non synaptic receptors located primarily on the membranes of neuronal and glial cells. Glutamate is abundant in the human body, but particularly in the nervous system and especially prominent in the human brain where it is the body's most prominent neurotransmitter, the brain's main excitatory neurotransmitter, and also the precursor for GABA, the brain's main inhibitory neurotransmitter. Glutamate receptors are responsible for the glutamate-mediated postsynaptic excitation of neural cells, and are important for neural communication, memory formation, learning, and regulation.

<span class="mw-page-title-main">CX-516</span> Chemical compound

CX-516 is an ampakine and nootropic that acts as an AMPA receptor positive allosteric modulator and had been undergoing development by a collaboration between Cortex, Shire, and Servier. It was studied as a potential treatment for Alzheimer's disease under the brand name Ampalex, and was also being examined as a treatment for ADHD.

<span class="mw-page-title-main">Farampator</span> Chemical compound

Farampator is an ampakine drug. It was developed by Cortex Pharmaceuticals, and licensed to Organon BioSciences for commercial development. Following the purchase of Organon by Schering-Plough in 2007, the development license to farampator was transferred. The development of farampator was eventually terminated, reportedly due to concerns about cardiac toxicity.

<span class="mw-page-title-main">CX614</span> Chemical compound

CX-614 is an ampakine drug developed by Cortex Pharmaceuticals. It has been investigated for its effect on AMPA receptors.

<span class="mw-page-title-main">CX-546</span> Chemical compound

CX-546 is an ampakine drug developed by Cortex Pharmaceuticals.

<span class="mw-page-title-main">Metabotropic glutamate receptor 2</span> Mammalian protein found in humans

Metabotropic glutamate receptor 2 (mGluR2) is a protein that, in humans, is encoded by the GRM2 gene. mGluR2 is a G protein-coupled receptor (GPCR) that couples with the Gi alpha subunit. The receptor functions as an autoreceptor for glutamate, that upon activation, inhibits the emptying of vesicular contents at the presynaptic terminal of glutamatergic neurons.

RespireRx Pharmaceuticals Inc. is a pharmaceutical company based in Glen Rock, New Jersey specializing in positive allosteric modulators of the AMPA receptor known as Ampakines.

<span class="mw-page-title-main">LY-404187</span> Chemical compound

LY-404187 is an AMPA receptor positive allosteric modulator which was developed by Eli Lilly and Company. It is a member of the biarylpropylsulfonamide class of AMPA receptor potentiators.

In pharmacology and biochemistry, allosteric modulators are a group of substances that bind to a receptor to change that receptor's response to stimuli. Some of them, like benzodiazepines or alcohol, function as psychoactive drugs. The site that an allosteric modulator binds to is not the same one to which an endogenous agonist of the receptor would bind. Modulators and agonists can both be called receptor ligands.

Within the science of molecular biology and cell biology, for human genetics, the GRIA2 gene is located on chromosome 4q32-q33. The gene product is the ionotropic AMPA glutamate receptor 2. The protein belongs to a family of ligand-activated glutamate receptors that are sensitive to alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA). Glutamate receptors function as the main excitatory neurotransmitter at many synapses in the central nervous system. L-glutamate, an excitatory neurotransmitter, binds to the Gria2 resulting in a conformational change. This leads to the opening of the channel converting the chemical signal to an electrical impulse. AMPA receptors (AMPAR) are composed of four subunits, designated as GluR1 (GRIA1), GluR2 (GRIA2), GluR3 (GRIA3), and GluR4(GRIA4) which combine to form tetramers. They are usually heterotrimeric but can be homodimeric. Each AMPAR has four sites to which an agonist can bind, one for each subunit.[5]

<span class="mw-page-title-main">Pesampator</span> Chemical compound

Pesampator is a positive allosteric modulator (PAM) of the AMPA receptor (AMPAR), an ionotropic glutamate receptor, which is under development by Pfizer for the treatment of cognitive symptoms in schizophrenia. It was also under development for the treatment of age-related sensorineural hearing loss, but development for this indication was terminated due to insufficient effectiveness. As of July 2018, pesampator is in phase II clinical trials for cognitive symptoms in schizophrenia.

<span class="mw-page-title-main">Mibampator</span> Chemical compound

Mibampator is a positive allosteric modulator (PAM) of the AMPA receptor (AMPAR), an ionotropic glutamate receptor, which was under development by Eli Lilly for the treatment of agitation/aggression in Alzheimer's disease but was never marketed. It reached phase II clinical trials prior to the discontinuation of its development.

<span class="mw-page-title-main">Tulrampator</span> Chemical compound

Tulrampator is a positive allosteric modulator (PAM) of the AMPA receptor (AMPAR), an ionotropic glutamate receptor, which is under development by RespireRx Pharmaceuticals and Servier for the treatment of major depressive disorder, Alzheimer's disease, dementia, and mild cognitive impairment. Tulrampator was in phase II clinical trial for depression, but failed to show superiority over placebo. There are also phase II clinical trials for Alzheimer's disease and phase I trials for dementia and mild cognitive impairment.

<span class="mw-page-title-main">AMPA receptor positive allosteric modulator</span>

AMPA receptor positive allosteric modulators are positive allosteric modulators (PAMs) of the AMPA receptor (AMPR), a type of ionotropic glutamate receptor which mediates most fast synaptic neurotransmission in the central nervous system.

<span class="mw-page-title-main">Willardiine</span> Chemical compound

Willardiine (correctly spelled with two successive i's) or (S)-1-(2-amino-2-carboxyethyl)pyrimidine-2,4-dione is a chemical compound that occurs naturally in the seeds of Mariosousa willardiana and Acacia sensu lato. The seedlings of these plants contain enzymes capable of complex chemical substitutions that result in the formation of free amino acids (See:#Synthesis). Willardiine is frequently studied for its function in higher level plants. Additionally, many derivates of willardiine are researched for their potential in pharmaceutical development. Willardiine was first discovered in 1959 by R. Gmelin, when he isolated several free, non-protein amino acids from Acacia willardiana (another name for Mariosousa willardiana) when he was studying how these families of plants synthesize uracilyalanines. A related compound, Isowillardiine, was concurrently isolated by a different group, and it was discovered that the two compounds had different structural and functional properties. Subsequent research on willardiine has focused on the functional significance of different substitutions at the nitrogen group and the development of analogs of willardiine with different pharmacokinetic properties. In general, Willardiine is the one of the first compounds studied in which slight changes to molecular structure result in compounds with significantly different pharmacokinetic properties.

References

  1. 1 2 3 4 5 Froestl W, Muhs A, Pfeifer A (2012). "Cognitive enhancers (nootropics). Part 1: drugs interacting with receptors". J. Alzheimers Dis. 32 (4): 793–887. doi:10.3233/JAD-2012-121186. PMID   22886028.
  2. O'Neill, M. J.; Bleakman, D.; Zimmerman, D. M.; Nisenbaum, E. S. (2004). "AMPA Receptor Potentiators for the Treatment of CNS Disorders". Current Drug Targets. CNS and Neurological Disorders. 3 (3): 181–194. doi:10.2174/1568007043337508. PMID   15180479.
  3. "Ampakines Platform Summary Report" (PDF).
  4. Wezenberg, E.; Verkes, R. J.; Ruigt, G. S.; Hulstijn, W.; et al. (2007). "Acute Effects of the Ampakine Farampator on Memory and Information Processing in Healthy Elderly Volunteers". Neuropsychopharmacology. 32 (6): 1272–1283. doi: 10.1038/sj.npp.1301257 . PMID   17119538.
  5. Ogier, M.; Wang, H.; Hong, E.; Wang, Q.; et al. (2007). "Brain-derived Neurotrophic Factor Expression and Respiratory Function Improve after Ampakine Treatment in a Mouse Model of Rett Syndrome". Journal of Neuroscience. 27 (40): 10912–10917. doi:10.1523/JNEUROSCI.1869-07.2007. PMC   6672830 . PMID   17913925.
  6. Saletan, William (2008-07-16). "Night of the Living Meds: The U.S. military's sleep-reduction program". Slate . Retrieved 2012-04-05.

Further reading