Ziconotide (SNX–111; Prialt), also called intrathecal ziconotide (ITZ) because of its administration route, is an atypical analgesic agent for the amelioration of severe and

chronic pain Chronic pain is classified as pain that lasts longer than three to six months. In medicine, the distinction between acute and chronic pain is sometimes determined by the amount of time since onset. Two commonly used markers are pain that continue ...

. Derived from ''

Conus magus ''Conus magus'', common name the magical cone, is a species of sea snail, a marine gastropod mollusk in the family Conidae, the cone snails and their allies. Like all species within the genus ''Conus'', these snails are predatory and venomous. ...

'', a cone snail, it is the synthetic form of an ω-

conotoxin A conotoxin is one of a group of neurotoxic peptides isolated from the venom of the marine cone snail, genus ''Conus''. Conotoxins, which are peptides consisting of 10 to 30 amino acid residues, typically have one or more disulfide bonds. Cono ...

peptide. It is 1,000 times as powerful as morphine. In December 2004 the

Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...

approved ziconotide when delivered as an infusion into the cerebrospinal fluid using an intrathecal pump system.

Discovery

Ziconotide is derived from the toxin of the

cone snail A cone is a three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the apex or vertex. A cone is formed by a set of line segments, half-lines, or lines con ...

species ''

''. Scientists have been intrigued by the effects of the thousands of chemicals in marine snail toxins since the initial investigations in the late 1960s by

Baldomero Olivera Baldomero Olivera (born 1941) is a Filipino chemist known for discovery of many cone snail toxins important for neuroscience. These molecules, called conotoxins, led to a breakthrough in the study of ion channels and neuromuscular synapses. He di ...

. Olivera, now a professor of biology in the

University of Utah The University of Utah (U of U, UofU, or simply The U) is a public research university in Salt Lake City, Utah. It is the flagship institution of the Utah System of Higher Education. The university was established in 1850 as the University of De ...

, was inspired by accounts of the deadly effects of these toxins from his childhood in the Philippines. Ziconotide was discovered in the early 1980s by University of Utah research scientist Michael McIntosh, when he was barely out of high school and working with Baldomero Olivera. Ziconotide was developed into an artificially manufactured drug by Elan Corporation. It was approved for sale under the name Prialt by the U.S. Food and Drug Administration on December 28, 2004, and by the

European Commission The European Commission (EC) is the executive of the European Union (EU). It operates as a cabinet government, with 27 members of the Commission (informally known as "Commissioners") headed by a President. It includes an administrative body ...

on February 22, 2005. Azur Pharma acquired worldwide rights (except Europe) to Prialt in 2010.

Mechanism of action

Ziconotide is a hydrophilic molecule that is freely soluble in water and is practically insoluble in methyl t-butyl ether. Ziconotide acts as a selective N-type voltage-gated calcium channel blocker. This action inhibits the release of pro-

nociceptive Nociception (also nocioception, from Latin ''nocere'' 'to harm or hurt') is the sensory nervous system's process of encoding noxious stimuli. It deals with a series of events and processes required for an organism to receive a painful stimulus, c ...

neurochemical A neurochemical is a small organic molecule or peptide that participates in neural activity. The science of neurochemistry studies the functions of neurochemicals. Prominent neurochemicals Neurotransmitters and neuromodulators *Glutamate is the ...

s like glutamate,

calcitonin gene-related peptide Calcitonin gene-related peptide (CGRP) is a member of the calcitonin family of peptides consisting of calcitonin, amylin, adrenomedullin, adrenomedullin 2 ( intermedin) and calcitonin‑receptor‑stimulating peptide. Calcitonin is mainly produ ...

(CGRP), and

substance P Substance P (SP) is an undecapeptide (a peptide composed of a chain of 11 amino acid residues) and a member of the tachykinin neuropeptide family. It is a neuropeptide, acting as a neurotransmitter and as a neuromodulator. Substance P and its clo ...

in the brain and

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the sp ...

, resulting in pain relief.

Therapeutic use

Due to the profound side effects or lack of efficacy when delivered through more common routes, such as orally or intravenously, ziconotide must be administered intrathecally (i.e. directly into the spinal fluid). As this is the most expensive and invasive method of drug delivery and involves additional risks of its own, ziconotide therapy is generally considered appropriate (as evidenced by the range of use approved by the FDA in the US) only for “management of severe chronic pain in patients for whom intrathecal (IT) therapy is warranted and who are intolerant of or refractory to other treatment, such as systemic

analgesics An analgesic drug, also called simply an analgesic (American English), analgaesic (British English), pain reliever, or painkiller, is any member of the group of drugs used to achieve relief from pain (that is, analgesia or pain management). It ...

, adjunctive therapies or IT morphine”. Research is ongoing to determine whether ziconotide can be formulated in a way that would allow it to be administered by less invasive means. However, this must be weighed against the high level of

pain management Pain management is an aspect of medicine and health care involving relief of pain (pain relief, analgesia, pain control) in various dimensions, from acute and simple to chronic and challenging. Most physicians and other health professionals pr ...

, both in terms of degree and length, and the apparent lack of tolerance and other signs of dependence even after extended treatment along with the need for alternatives to other therapies that have not worked for the patient. Ziconotide is also contraindicated for patients with certain preexisting mental disorders (e.g. psychosis) due to evidence that they are more susceptible to certain severe side effects.prialt.com

Adverse reactions

The most common side effects are dizziness, nausea, confusion,

nystagmus Nystagmus is a condition of involuntary (or voluntary, in some cases) eye movement. Infants can be born with it but more commonly acquire it in infancy or later in life. In many cases it may result in reduced or limited vision. Due to the invol ...

, and headache. Others may include weakness,

hypertonia Hypertonia is a term sometimes used synonymously with spasticity and rigidity in the literature surrounding damage to the central nervous system, namely upper motor neuron lesions. Impaired ability of damaged motor neurons to regulate descending ...

, ataxia, abnormal vision,

anorexia Anorexia nervosa, often referred to simply as anorexia, is an eating disorder characterized by low weight, food restriction, body image disturbance, fear of gaining weight, and an overpowering desire to be thin. ''Anorexia'' is a term of Gre ...

, somnolence, unsteadiness on feet,

vertigo Vertigo is a condition where a person has the sensation of movement or of surrounding objects moving when they are not. Often it feels like a spinning or swaying movement. This may be associated with nausea, vomiting, sweating, or difficulties w ...

, urinary retention, pruritus, increased sweating, diarrhea, nausea, vomiting,

asthenia Weakness is a symptom of a number of different conditions. The causes are many and can be divided into conditions that have true or perceived muscle weakness. True muscle weakness is a primary symptom of a variety of skeletal muscle diseases, i ...

fever Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using val ...

, rigors,

sinusitis Sinusitis, also known as rhinosinusitis, is inflammation of the mucous membranes that line the sinuses resulting in symptoms that may include thick nasal mucus, a plugged nose, and facial pain. Other signs and symptoms may include fever, head ...

, muscle spasms, myalgia,

insomnia Insomnia, also known as sleeplessness, is a sleep disorder in which people have trouble sleeping. They may have difficulty falling asleep, or staying asleep as long as desired. Insomnia is typically followed by daytime sleepiness, low energy, ...

, anxiety, amnesia, tremor, memory impairment, and induced psychiatric disorders. Other side effects which are less frequent but still clinically significant include auditory and visual hallucinations, thoughts of suicide, acute kidney failure, atrial fibrillation, cardiovascular accident,

sepsis Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...

, new or worsening depression, paranoia, disorientation, meningitis, and

seizures An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with l ...

. Therefore, it is contraindicated in people with a history of psychosis,

schizophrenia Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social wit ...

, clinical depression, and bipolar disorder. Recent incidents suggesting a link between intrathecal ziconotide treatment and increased risk of suicide have led to calls for strict and ongoing psychiatric monitoring of patients to avoid suicide occurring in vulnerable individuals. There is no known antidote.

Structure

Ziconotide is a peptide with the

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha a ...

sequence H- Cys- Lys- Gly-Lys-Gly- Ala-Lys-Cys- Ser- Arg- Leu- Met- Tyr- Asp-Cys-Cys- Thr-Gly- Ser-Cys-Arg-Ser-Gly-Lys-Cys-NH₂ (CKGKGAKCSRLMYDCCTGSCRSGKC-NH2) and contains 3

disulfide In biochemistry, a disulfide (or disulphide in British English) refers to a functional group with the structure . The linkage is also called an SS-bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups. In ...

bonds (Cys1-Cys16, Cys8-Cys20, and Cys15-Cys25).

Patents

The drug was patented by Neurex Corp., a U.S. company purchased in 1998 by

Élan Elan Corporation plc was a major drugs firm based in Dublin, Ireland, which had major interests in the United States. It was listed on the New York Stock Exchange as ELN, the Irish Stock Exchange as ELN.I, and the London Stock Exchange as ELN. ...

Corporation, plc of Ireland. U.S. patents assigned to Elan include , , , and .

References

External links

* * {{Portal bar , Medicine Analgesics Calcium channel blockers Peptides