Tafamidis meglumine (Vyndaqel®, Pfizer) is a novel, first-in-class drug for the treatment of transthyretin familial amyloid polyneuropathy (TTR-FAP), a rare neurodegenerative disorder characterized by progressive sensory, motor and autonomic impairment that is ultimately fatal. Pathogenic mutations in the transthyretin (TTR) protein lead to destabilization of its tetrameric structure and subsequent formation of amyloid aggregates. Tafamidis is a small-molecule inhibitor that binds selectively to TTR in human plasma and kinetically stabilizes the tetrameric structure of both wild-type TTR and a number of different mutants. Clinical trials indicate that tafamidis slows disease progression in patients with TTR-FAP and reduces the burden of disease, demonstrating improvement in small and large nerve fiber function, modified body mass index and lower extremity neurological examination. Tafamidis meglumine has been launched for TTR FAP in the EU, Japan, Argentina, Malta and Mexico, and is preregistration in the US for this indication.

Amifampridine (Firdapse), currently approved in the European Union, is the first and only approved drug for the symptomatic treatment of Lambert-Eaton Myasthenic Syndrome (LEMS) in adults, a rare autoimmune disease with the primary symptoms of muscle weakness. In LEMS, the body’s own immune system attacks connections between nerves and muscles and disrupts the ability of nerve cells to send signals to muscle cells. Amifampridine blocks voltage-dependent potassium channels, thereby prolonging pre-synaptic cell membrane depolarization. Prolonging the action potential enhances the transport of calcium into the nerve ending. The resulting increase in intracellular calcium concentrations facilitates exocytosis of acetylcholine containing vesicles, which in turn enhances neuromuscular transmission. Amifampridine phosphate has been granted Orphan Drug Designation and Breakthrough Therapy designation by the FDA for the treatment of Lambert-Eaton Myasthenic Syndrome (LEMS).

Tetrabenazine (trade name Xenazine) is a monoamine depleter and used as the symptomatic treatment of chorea associated with Huntington's disease. Tetrabenazine is a reversible human vesicular monoamine transporter type 2 inhibitor (Ki = 100 nM). It acts within the basal ganglia and promotes depletion of monoamine neurotransmitters serotonin, norepinephrine, and dopamine from stores. It also decreases uptake into synaptic vesicles. Dopamine is required for fine motor movement, so the inhibition of its transmission is efficacious for hyperkinetic movement. Tetrabenazine exhibits weak in vitro binding affinity at the dopamine D2 receptor. The most common adverse reactions, which have occurred in at least 10% of subjects in studies and at least 5% greater than in subjects who received placebo, have been: sedation or somnolence, fatigue, insomnia, depression, suicidal thoughts, akathisia, anxiety, and nausea.

Riluzole, a member of the benzothiazole class, is indicated for the treatment of patients with amyotrophic lateral sclerosis. Its pharmacological properties include the following, some of which may be related to its effect: 1) an inhibitory effect on glutamate release (activation of glutamate reuptake), 2) inactivation of voltage-dependent sodium channels, and 3) ability to interfere with intracellular events that follow transmitter binding at excitatory amino acid receptors. Common adverse reactions include headache, abdominal pain, back pain, vomiting, dyspepsia, diarrhea, dizziness. Riluzole-treated patients that take other hepatotoxic drugs may be at increased risk for hepatotoxicity.

Dextromethorphan is a non-narcotic morphine derivative widely used as an antitussive for almost 40 years. It has attracted attention due to its anticonvulsant and neuroprotective properties. It is a cough suppressant in many over-the-counter cold and cough medicines. In 2010, the FDA approved the combination product dextromethorphan/quinidine for the treatment of pseudobulbar affect. Dextromethorphan suppresses the cough reflex by a direct action on the cough center in the medulla of the brain. Dextromethorphan shows high-affinity binding to several regions of the brain, including the medullary cough center. This compound is an NMDA receptor antagonist and acts as a non-competitive channel blocker. It is one of the widely used antitussives and is used to study the involvement of glutamate receptors in neurotoxicity. Dextromethorphan (DM) is a sigma-1 receptor agonist and an uncompetitive NMDA receptor antagonist. The mechanism by which dextromethorphan exerts therapeutic effects in patients with pseudobulbar affect is unknown. Dextromethorphan should not be taken with monoamine oxidase inhibitors due to the potential for serotonin syndrome. Dextromethorphan is extensively metabolized by CYP2D6 to dextrorphan, which is rapidly glucuronidated and unable to cross the blood-brain barrier.

Laquinimod is a new orally available carboxamide derivative, which is currently developed for relapsing remitting (RR) and chronic progressive (CP) forms of multiple sclerosis (MS; RRMS or CPMS) as well as neurodegenerative diseases. The mechanism of action of laquinimod is not fully elucidated because the molecular target is not known. Treatment with laquinimod led to a significant and persistent increase in brain-derived neuroprotective factor (BDNF) serum levels compared to placebo treatment. In human studies, a decrease of pro-inflammatory and an increase of anti-inflammatory cytokines have been measured. After commercial launch the unexpected severe cardiac adverse events (AEs) such as serositis, pericarditis, and myocardial infarction were detected.

Subarachnoid haemorrhage (SAH) following cerebral aneurysm rupture or trauma can result in the induction of secondary ischaemic brain damage via a decrease in microvascular perfusion, a disruption of the blood-brain barrier and consequent vasogenic oedema, and the delayed spasm of the major cerebral arteries (i.e. vasospasm). It is increasingly apparent that oxygen radical-induced, iron-catalyzed lipid peroxidation (LP) within the subarachnoid blood and vascular wall plays a key role in the occurrence of these secondary events. Tirilazad mesylate, is a nonglucocorticoid, 21-aminosteroid, is a potent cytoprotective inhibitor of LP that works by a combination of radical scavenging and membrane stabilizing properties. It has been demonstrated to attenuate the acute and delayed vascular consequences of SAH and to protect the brain against ischaemic insults. Tirilazad mesylate has been proposed to treat acute ischaemic stroke. When tested on animal models, tirilazad protects brain tissue, and reduces brain damage. However, the drug fails to treat, and even worsens a stroke when studied on a human being.

Xaliproden is an orally active 5HT1-A receptor antagonist that was being developed by Sanofi. It has been evaluated for the treatment of Alzheimer's disease and amyotrophic lateral sclerosis (ALS), and protection against peripheral neurotoxicity associated with certain cancer chemotherapies. Two large, 18-month, clinical trials of xaliproden (monotherapy or adjunctive therapy, respectively) in patients with mild to moderate AD (MMSE, 16–26, inclusive) were completed in 2007. Failure to demonstrate sufficient efficacy in both trials resulted in cancelation of the xaliproden development program for AD in September 2007.

Dimethyl fumarate (DMF) is the methyl ester of fumaric acid. DMF was initially recognized as a very effective hypoxic cell radiosensitizer. Later, DMF combined with three other fumaric acid esters (FAE) was licensed in Germany as oral therapy for psoriasis (trade name Fumaderm). Phase III clinical trials found that DMF (BG-12) successfully reduced relapse rate and increased time to progression of disability in multiple sclerosis (trade name Tecfidera). DMF is thought to have immunomodulatory properties without significant immunosuppression. The mechanism of action of dimethyl fumarate in multiple sclerosis is not well understood. It is thought to involve dimethyl fumarate degradation to its active metabolite monomethyl fumarate (MMF) then MMF up-regulates the Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) pathway that is activated in response to oxidative stress. Dimethyl fumarate is marketed under the brand name Tecfidera.

Dalfampridine is a potassium channel blocker, used as a research tool in characterizing subtypes of the potassium channel. Dalfampridine has also been used as a drug, to manage some of the symptoms of multiple sclerosis, and is indicated for symptomatic improvement of walking in adults with several variations of the disease. The mechanism by which dalfampridine exerts its therapeutic effect has not been fully elucidated. Dalfampridine is a broad spectrum potassium channel blocker. In animal studies, dalfampridine has been shown to increase conduction of action potentials in demyelinated axons through inhibition of potassium channels.