Cytarabine, also known as cytosine arabinoside (ara-C), is a

chemotherapy medication Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs (chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemothe ...

used to treat

acute myeloid leukemia Acute myeloid leukemia (AML) is a cancer of the myeloid line of blood cells, characterized by the rapid growth of abnormal cells that build up in the bone marrow and blood and interfere with haematopoiesis, normal blood cell production. Sympto ...

(AML),

acute lymphocytic leukemia Acute lymphoblastic leukemia (ALL) is a cancer of the lymphoid line of blood cells characterized by the development of large numbers of immature lymphocytes. Symptoms may include feeling tired, pale skin color, fever, easy bleeding or bruisin ...

(ALL),

chronic myelogenous leukemia Chronic myelogenous leukemia (CML), also known as chronic myeloid leukemia, is a cancer of the white blood cells. It is a form of leukemia characterized by the increased and unregulated growth of myeloid cells in the bone marrow and the accumula ...

(CML), and non-Hodgkin's lymphoma. It is given by

injection into a vein Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutrie ...

, under the skin, or into the

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates. CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the bra ...

. There is a liposomal formulation for which there is tentative evidence of better outcomes in lymphoma involving the meninges. Common side effects include

bone marrow suppression Bone marrow suppression also known as myelotoxicity or myelosuppression, is the decrease in production of cells responsible for providing immunity (leukocytes), carrying oxygen ( erythrocytes), and/or those responsible for normal blood clotting ( ...

, vomiting, diarrhea, liver problems, rash, ulcer formation in the mouth, and bleeding. Other serious side effects include loss of consciousness, lung disease, and

allergic reactions Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic dermat ...

. Use during

pregnancy Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occurs by sexual intercourse, but ...

may harm the baby. Cytarabine is in the antimetabolite and

nucleoside analog Nucleoside analogues are nucleosides which contain a nucleic acid analogue and a sugar. Nucleotide analogs are nucleotides which contain a nucleic acid analogue, a sugar, and a phosphate group with one to three phosphates. Nucleoside and nucl ...

families of medication. It works by blocking the function of

DNA polymerase A DNA polymerase is a member of a family of enzymes that catalyze the synthesis of DNA molecules from nucleoside triphosphates, the molecular precursors of DNA. These enzymes are essential for DNA replication and usually work in groups to create ...

. Cytarabine was patented in 1960 and approved for medical use in 1969. It is on the

World Health Organization's List of Essential Medicines The WHO Model List of Essential Medicines (aka Essential Medicines List or EML), published by the World Health Organization (WHO), contains the medications considered to be most effective and safe to meet the most important needs in a health s ...

Medical uses

Cytarabine is mainly used in the treatment of acute myeloid leukaemia,

acute lymphocytic leukaemia Acute lymphoblastic leukemia (ALL) is a cancer of the lymphoid line of blood cells characterized by the development of large numbers of immature lymphocytes. Symptoms may include feeling tired, pale skin color, fever, easy bleeding or bruisin ...

(ALL) and in

lymphoma Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enl ...

s, where it is the backbone of

induction chemotherapy Induction chemotherapy is the first-line treatment of cancer with a chemotherapeutic drug. The goal of induction chemotherapy is to cure the cancer. It may be contrasted with neoadjuvant therapy, with consolidation chemotherapy (intended to k ...

. Cytarabine also possesses

antiviral Antiviral drugs are a class of medication used for treating viral infections. Most antivirals target specific viruses, while a broad-spectrum antiviral is effective against a wide range of viruses. Unlike most antibiotics, antiviral drugs do no ...

activity, and it has been used for the treatment of generalised

herpesvirus ''Herpesviridae'' is a large family of DNA viruses that cause infections and certain diseases in animals, including humans. The members of this family are also known as herpesviruses. The family name is derived from the Greek word ''ἕρπει� ...

infection. However, cytarabine is not very selective in this setting and causes

and other severe side effects. Therefore, ara-C is not a useful antiviral agent in humans because of its toxic profile. Cytarabine is also used in the study of the

nervous system In Biology, biology, the nervous system is the Complex system, highly complex part of an animal that coordinates its Behavior, actions and Sense, sensory information by transmitting action potential, signals to and from different parts of its ...

to control the proliferation of

glial Glia, also called glial cells (gliocytes) or neuroglia, are non-neuronal cells in the central nervous system (brain and spinal cord) and the peripheral nervous system that do not produce electrical impulses. They maintain homeostasis, form m ...

cells in cultures, the amount of glial cells having an important impact on

neuron A neuron, neurone, or nerve cell is an membrane potential#Cell excitability, electrically excitable cell (biology), cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous ...

Side effects

One of the unique toxicities of cytarabine is cerebellar toxicity when given in high doses, which may lead to

ataxia Ataxia is a neurological sign consisting of lack of voluntary coordination of muscle movements that can include gait abnormality, speech changes, and abnormalities in eye movements. Ataxia is a clinical manifestation indicating dysfunction of t ...

. Cytarabine may cause granulocytopenia and other impaired body defenses, which may lead to infection, and

thrombocytopenia Thrombocytopenia is a condition characterized by abnormally low levels of platelets, also known as thrombocytes, in the blood. It is the most common coagulation disorder among intensive care patients and is seen in a fifth of medical patients a ...

, which may lead to

hemorrhage Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, vag ...

. Toxicity:

pancreatitis Pancreatitis is a condition characterized by inflammation of the pancreas. The pancreas is a large organ behind the stomach that produces digestive enzymes and a number of hormones. There are two main types: acute pancreatitis, and chronic p ...

leukopenia Leukopenia () is a decrease in the number of leukocytes (WBC). Found in the blood, they are the white blood cells, and are the body's primary defense against an infection. Thus the condition of leukopenia places individuals at increased risk of i ...

, thrombocytopenia,

anemia Anemia or anaemia (British English) is a blood disorder in which the blood has a reduced ability to carry oxygen due to a lower than normal number of red blood cells, or a reduction in the amount of hemoglobin. When anemia comes on slowly, ...

, GI disturbances,

stomatitis Stomatitis is inflammation of the mouth and lips. It refers to any inflammatory process affecting the mucous membranes of the mouth and lips, with or without oral ulceration. In its widest meaning, stomatitis can have a multitude of different ca ...

conjunctivitis Conjunctivitis, also known as pink eye, is inflammation of the outermost layer of the white part of the eye and the inner surface of the eyelid. It makes the eye appear pink or reddish. Pain, burning, scratchiness, or itchiness may occur. The ...

, pneumonitis,

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 ...

, and

dermatitis Dermatitis is inflammation of the skin, typically characterized by itchiness, redness and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become thickened. The area of skin involved can ...

, palmar-plantar erythrodysesthesia. Rarely,

myelopathy Myelopathy describes any neurologic deficit related to the spinal cord. The most common form of myelopathy in humans, '' cervical spondylotic myelopathy (CSM)'', also called ''degenerative cervical myelopathy'', results from narrowing of the spina ...

has been reported after high dose or frequent

intrathecal Intrathecal administration is a route of administration for drugs via an injection into the spinal canal, or into the subarachnoid space so that it reaches the cerebrospinal fluid (CSF) and is useful in spinal anesthesia, chemotherapy, or pa ...

Ara-C administration. When used in protocols designated as high dose, cytarabine can cause cerebral and cerebellar dysfunction, ocular toxicity, pulmonary toxicity, severe GI ulceration and

peripheral neuropathy Peripheral neuropathy, often shortened to neuropathy, is a general term describing disease affecting the peripheral nerves, meaning nerves beyond the brain and spinal cord. Damage to peripheral nerves may impair sensation, movement, gland, or or ...

(rare). To prevent the side effects and improve the therapeutic efficiency, various derivatives of these drugs (including amino acid, peptide, fatty acid and phosphates) have been evaluated, as well as different delivery systems.

Mechanism of action

Cytosine arabinoside combines a

cytosine Cytosine () (symbol C or Cyt) is one of the four nucleobases found in DNA and RNA, along with adenine, guanine, and thymine ( uracil in RNA). It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached ...

base with an

arabinose Arabinose is an aldopentose – a monosaccharide containing five carbon atoms, and including an aldehyde (CHO) functional group. For biosynthetic reasons, most saccharides are almost always more abundant in nature as the "D"-form, or structural ...

sugar. It is an

antimetabolic agent An antimetabolite is a chemical that inhibits the use of a metabolite, which is another chemical that is part of normal metabolism. Such substances are often similar in structure to the metabolite that they interfere with, such as the antifolates ...

with the chemical name of ''1β-arabinofuranosylcytosine''. Certain sponges, where it was originally found, use arabinoside sugars to form a different compound (not part of DNA). Cytosine arabinoside is similar enough to human deoxycytosine to be incorporated into human DNA, but different enough that it kills the cell. Cytosine arabinoside interferes with the synthesis of DNA. Its mode of action is due to its rapid conversion into

cytosine arabinoside triphosphate Arabinofuranosylcytosine triphosphate is a nucleotide that inhibits the synthesis of DNA by acting as an antimetabolic agent against deoxycytidine (a component of DNA). It is the biologically active form of cytarabine Cytarabine, also known ...

, which damages DNA when the

cell cycle The cell cycle, or cell-division cycle, is the series of events that take place in a cell that cause it to divide into two daughter cells. These events include the duplication of its DNA ( DNA replication) and some of its organelles, and sub ...

holds in the

S phase S phase (Synthesis Phase) is the phase of the cell cycle in which DNA is replicated, occurring between G1 phase and G2 phase. Since accurate duplication of the genome is critical to successful cell division, the processes that occur during ...

(synthesis of DNA). Rapidly dividing cells, which require DNA replication for

mitosis In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is maint ...

, are therefore most affected. Cytosine arabinoside also inhibits both DNA and

RNA polymerase In molecular biology, RNA polymerase (abbreviated RNAP or RNApol), or more specifically DNA-directed/dependent RNA polymerase (DdRP), is an enzyme that synthesizes RNA from a DNA template. Using the enzyme helicase, RNAP locally opens the ...

s and

nucleotide Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecul ...

reductase enzymes needed for DNA synthesis. Cytarabine is the first of a series of cancer drugs that altered the sugar component of

nucleosides Nucleosides are glycosylamines that can be thought of as nucleotides without a phosphate group. A nucleoside consists simply of a nucleobase (also termed a nitrogenous base) and a five-carbon sugar (ribose or 2'-deoxyribose) whereas a nucleotid ...

. Other cancer drugs modify the base. Cytarabine is often given by continuous intravenous infusion, which follows a biphasic elimination – initial fast clearance rate followed by a slower rate of the analog. Cytarabine is transported into the cell primarily by hENT-1. It is then monophosphorylated by deoxycytidine kinase and eventually cytarabine-5´-triphosphate, which is the active metabolite being incorporated into DNA during DNA synthesis. Several mechanisms of resistance have been reported. Cytarabine is rapidly deaminated by cytidine deaminase in the serum into the inactive uracil derivative. Cytarabine-5´-monophosphate is deaminated by deoxycytidylate deaminase, leading to the inactive uridine-5´-monophosphate analog. Cytarabine-5´-triphosphate is a substrate for SAMHD1. Furthermore, SAMHD1 has been shown to limit the efficacy of cytarabine efficacy in patients. When used as an

, cytarabine-5´-triphosphate functions by inhibiting viral DNA synthesis. Cytarabine is able to inhibit herpesvirus and vaccinia virus replication in cells during tissue culture. However, cytarabine treatment was only effective for herpesvirus infection in a murine model. In mice, Ara-CTP (cytarabine-5'-triphosphate) blocks memory consolidation, but not short term memory, of a context fear conditioning event.Colón-Cesario M, Wang J, Ramos X, García HG, Dávila JJ, Laguna J, Rosado C, Peña de Ortiz S. An inhibitor of DNA recombination blocks memory consolidation, but not reconsolidation, in context fear conditioning. J Neurosci. 2006 May 17;26(20):5524-33. doi: 10.1523/JNEUROSCI.3050-05.2006. PMID: 16707804; PMCID: PMC6675301 The blockage of memory consolidation was proposed to be due to the inhibition by Ara-CTP of the DNA

non-homologous end joining Non-homologous end joining (NHEJ) is a pathway that repairs double-strand breaks in DNA. NHEJ is referred to as "non-homologous" because the break ends are directly ligated without the need for a homologous template, in contrast to homology direct ...

pathway. Thus transient DNA breakage followed by non-homologous end joining appear to be necessary steps in the formation of a long-term memory of an event.

History

Isolation of arabinose-containing nucleotides from the Caribbean sponge ''Cryptotheca crypta'' (now '' Tectitethya crypta'') together with the realization that these compounds could act as DNA synthesis chain terminators led to exploration of these novel nucleotides as potential anticancer therapeutics. Cytarabine was first synthesized in 1959 by Richard Walwick, Walden Roberts, and Charles Dekker at the

University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant u ...

. It was approved by the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...

in June 1969, and was initially marketed in the U.S. by Upjohn under the

trade name A trade name, trading name, or business name, is a pseudonym used by companies that do not operate under their registered company name. The term for this type of alternative name is a "fictitious" business name. Registering the fictitious name ...

Cytosar-U.

Names

It is also known as ara-C (arabinofuranosyl cytidine). * Cytosar-U * Tarabine PFS (Pfizer) * Depocyt (longer-lasting liposomal formulation) * AraC

References

External links

ADAP drugs
page on cytarabine

page on cytarabine

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