Cyclic adenosine monophosphate (cAMP, cyclic AMP or 3'-5'-cyclic adenosine monophosphate) is a molecule that is important in many biological processes; it is derived from adenosine triphosphate (ATP) by adenylate cyclase located on the inner side of the plasma membrane and anchored at various locations in the interior of the cell. Around 1960 Earl W. Sutherland, Jr. showed that cyclic adenosine monophosphate (cAMP) serves as the secondary messenger within the cell. Cyclic AMP works by activating protein kinase A (PKA, or cAMP-dependent protein kinase). PKA is normally inactive as a tetrameric holoenzyme, consisting of two catalytic and two regulatory units with the regulatory units blocking the catalytic centers of the catalytic units. Cyclic AMP binds to specific locations on the regulatory units of the protein kinase, and causes dissociation between the regulatory and catalytic subunits, thus enabling those catalytic units to phosphorylate substrate proteins. It was discovered, that melanocytes require the RAS/RAF/MEK/ERK and the cyclic AMP (cAMP) signaling pathways to maintain the fine balance between proliferation and differentiation. cAMP suppressed CRAF activity in melanocytes and that was essential to suppress the oncogenic potential of CRAF in the cells. When RAS was mutated in melanoma, the cells switched their signaling from BRAF to CRAF. That switch was accompanied by dysregulated cAMP signaling, a step that was necessary to allow CRAF to signal to MEK. Thus, a fundamental switch in RAF isoform usage occurs when RAS was mutated in melanoma, and that occurs in the context of disrupted cAMP signaling. These data have important implications for the development of therapeutic strategies to treat this life-threatening disease.

Guanosine is an endogenous guanine nucleoside. Guanosine was shown to be protective in several in vitro and/or in vivo experimental models of central nervous system (CNS) diseases including ischemic stroke, Alzheimer's disease, Parkinson's disease, spinal cord injury, nociception, and depression. The mechanisms underlying the neurobiological properties of guanosine seem to involve the activation of several intracellular signaling pathways and a close interaction with the adenosinergic system, with a consequent stimulation of neuroprotective and regenerative processes in the CNS. Several guanosine analogues, i.e. acyclovir (and its oral prodrug valaciclovir), penciclovir (in its oral prodrug form, famciclovir) and ganciclovir, are widely used for the treatment of herpesvirus (i.e. HSV-1, HSV-2, VZV and HCMV) infections.

Adenosine triphosphate (ATP) is an adenine nucleotide containing three phosphate groups esterified to the sugar moiety. Adenosine triphosphate is the energy source in living cells. In physiological conditions, the average concentration varies from 3150 mM in mammalian cells to 1500–1900 mM in human blood cells. Extracellular adenosine and adenosine triphosphate (ATP) are involved in biological processes including neurotransmission, muscle contraction, cardiac function, platelet function, vasodilatation, signal transduction and secretion in a variety of cell types. A large family of membrane-bound receptors mediates cell signalling by ATP and adenosine. These purinergic receptors ultimately determine the variety of effects induced by extracellular ATP and adenosine. ATP and adenosine have strong negative chronotropic and dromotropic effects on the mammalian heart. The sensitivity of the sinus node and the atrioventricular node to ATP and adenosine manifests pronounced variability among species. For more than three decades, ATP has been used routinely in Europe in the acute therapy of paroxysmal supraventricular tachycardia. ATPace™, an injectable formulation of adenosine 5′-triphosphate (ATP), was developed by Cordex Pharma, Inc. (Cordex) as a diagnostic and therapeutic drug for the management of cardiac bradyarrhythmias. Extracellular ATP exerts multiple effects in various cell types by activating cell-surface receptors known as P2 receptors. In the heart, ATP suppresses the automaticity of cardiac pacemakers and atrioventricular (AV) nodal conduction via adenosine, the product of its degradation by ecto-enzymes, as well as by triggering a cardio-cardiac vagal reflex. ATP, given as a rapid intravenous bolus injection, has been used since the late 1940s as a highly effective and safe therapeutic agent for the acute termination of reentrant paroxysmal supraventricular tachycardia (PSVT) involving the AV node. In addition, preliminary studies have shown that ATP can also be used as a diagnostic agent for the identification of several cardiac disorders including sinus node dysfunction (sick sinus syndrome), dual AV nodal pathways, long QT syndrome, and bradycardic syncope. The US Food and Drug Administration has approved Cordex formulation for ATP as an Investigational New Drug and two pathways for its marketing approval; one therapeutic, i.e., acute termination of paroxysmal PSVT, and the other diagnostic, i.e., the identification of patients with bradycardic syncope who can benefit from pacemaker therapy. However later ATPace development for the treatment of bradycardia and paroxysmal supraventricular tachycardia was discontinued.

Inosine is a naturally occurring nucleoside which serves as an intermediate in purine metabolism. The metabolism of purines in humans generates a potent antioxidant compound, uric acid, which is known to be a natural scavenger of both oxygen and nitrogen reactive species as well as having chelator properties. Inosine, as a precursor of uric acid, was shown to have neuroprotective effect in vitro and is being tested in phase III of clinical trials for the treatment of Parkinson disease. The treatment with inosine is belived to prevent or slow the disease.

Adenine is a nucleobase (a purine derivative). Its derivatives have a variety of roles in biochemistry including cellular respiration, in the form of both the energy-rich adenosine triphosphate (ATP) and the cofactors nicotinamide adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD). It also has functions in protein synthesis and as a chemical component of DNA and RNA. The shape of adenine is complementary to either thymine in DNA or uracil in RNA

Apaxifylline is an adenosine A1 receptor antagonist that was under investigation with Boehringer Ingelheim as a potential neuroprotective drug for the treatment of dementia. Apaxifylline was able to antagonize scopolamine-induced deficits in the rat in a memory task. A single oral application of apaxifylline 90 min before the rats received the noxious stimulus significantly attenuated the scopolamine-induced deficits observed during the retention trial of the rat in the passive avoidance paradigm. Apaxifylline treatment does not influence motility.