Clofarabine is a

purine Purine is a heterocyclic aromatic organic compound that consists of two rings ( pyrimidine and imidazole) fused together. It is water-soluble. Purine also gives its name to the wider class of molecules, purines, which include substituted purines ...

nucleoside 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 nucleoti ...

antimetabolite 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 antifolate ...

marketed in the United States and Canada as Clolar. In Europe and Australia/New Zealand the product is marketed under the name Evoltra. It is FDA-approved for treating relapsed or refractory

acute lymphoblastic 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 bruis ...

(ALL) in children after at least two other types of treatment have failed. Some investigations of effectiveness in cases of

acute myeloid leukaemia 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 normal blood cell production. Symptoms may inclu ...

(AML) and juvenile myelomonocytic leukaemia (JMML) have been carried out. Ongoing trials are assessing its efficacy for managing other cancers.

Approval

Clolar was

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 ...

(FDA) approved 28 December 2004. (Under accelerated approval regulations requiring further clinical studies.)

Side effects

Tumor lysis syndrome Tumor lysis syndrome (TLS) is a group of metabolic abnormalities that can occur as a complication from the treatment of cancer, where large amounts of tumor cells are killed off ( lysed) from the treatment, releasing their contents into the blo ...

(TLS). Clofarabine quickly kills leukaemia cells in the blood. The body may react to this. Signs include hyperkalemia, hyperuricemia, and hyperphosphatemia. TLS is very serious and can lead to death if it is not treated right away. * Systemic inflammatory response syndrome (SIRS): symptoms include fast breathing, fast heartbeat, low blood pressure, and fluid in the lungs. *Bone marrow problems (suppression). Clofarabine can stop the bone marrow from making enough

red blood cells Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "hol ...

white blood cells White blood cells, also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from mult ...

, and

platelets Platelets, also called thrombocytes (from Greek θρόμβος, "clot" and κύτος, "cell"), are a component of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping, thereby ...

. Serious side effects that can happen because of bone marrow suppression include severe infection (

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 ...

), bleeding, and

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, t ...

. *Effects on

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 ...

and

breastfeeding Breastfeeding, or nursing, is the process by which human breast milk is fed to a child. Breast milk may be from the breast, or may be expressed by hand or pumped and fed to the infant. The World Health Organization (WHO) recommends that bre ...

. Girls and women should not become pregnant or breastfeed during treatment which may harm the baby. *

Dehydration In physiology, dehydration is a lack of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mil ...

and

low blood pressure Hypotension is low blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood. Blood pressure is indicated by two numbers, the systolic blood pressure (the top number) and the di ...

. Clofarabine can cause

vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenter ...

and

diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin w ...

which may lead to low body fluid (dehydration). Signs and symptoms of dehydration include dizziness, lightheadedness, fainting spells, or decreased

urination Urination, also known as micturition, is the release of urine from the urinary bladder through the urethra to the outside of the body. It is the urinary system's form of excretion. It is also known medically as micturition, voiding, uresis, ...

. *Other side effects. The most common side effects are stomach problems (including vomiting, diarrhea, and

nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of th ...

), and effects on blood cells (including low red blood cells count, low white blood cell count, low platelet count,

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 infection). Clofarabine can also cause

tachycardia Tachycardia, also called tachyarrhythmia, is a heart rate that exceeds the normal resting rate. In general, a resting heart rate over 100 beats per minute is accepted as tachycardia in adults. Heart rates above the resting rate may be normal ( ...

and can affect the

liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it i ...

and

kidneys The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; bloo ...

Contraindications

*pregnancy or planned pregnancy *breast-feeding *liver problems *kidney problems

Drug interactions

*nephrotoxic drugs *hepatotoxic drugs

Delivery

*By

intravenous infusion 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 ...

. *Dosage is a 2-hour infusion (52 mg/m²) every day for five days. The cycle is repeated every 2 to 6 weeks. *Regular blood tests to monitor his or her blood cells, kidney function, and liver function.

Biology

Clofarabine is a second-generation purine nucleoside analog designed to overcome biological limitations observed with ara-A and fludarabine. A 2´(S)-fluorine in clofarabine significantly increased the stability of the glycosidic bond in acidic solution and toward phosphorolytic cleavage as compared to fludarabine. A chlorine substitution at the 2-position of the adenine base avoids production of a 2-fluoroadenine analog, a precursor to the toxic 2-fluoro-adenosine-5´-triphosphate and prevents deamination of the base as compared to ara-A. Clofarabine can be administered intravenously or given orally. Clofarabine enters cells via hENT1, hENT2, and hCNT2, where upon it is phosphorylated by deoxycytidine kinase to generate clofarabine-5´-monophosphate. The rate-limiting step in clofarabine metabolism is clofarabine-5´-diphosphosphate. Clofarabine-5´-triphosphate is the active-metabolite, and it inhibits ribonucleotide reductase, resulting in a decrease cellular dNTP concentrations, which promotes greater incorporation of clofarabine-5´-triphosphate during DNA synthesis. Embedded clofarabine-5´-monophosphate in the DNA promotes polymerase arrest at the replication fork, triggering DNA repair mechanisms that without repair lead to DNA strand breaks in vitro and cytochrome c-mediated apoptosis in vitro. Studies using cell lines have shown that clofarabine-5´-triphosphate can also be incorporated into RNA. Mechanisms of resistance and turnover have been reported. Clofarabine-resistance arises from decreased deoxycytidine kinase activity in vitro. ABC transporter ABCG2 promotes export of clofarabine-5´-monophosphate and thus limits the cytotoxic effects of this analog in vivo. Biochemically, clofarabine-5’-triphosphate was shown to be substrate for SAMHD1, thus potentially limiting the amount of active compound in cells.

References

External links

* {{Portal bar , Medicine Organofluorides Organochlorides Purines Purine antagonists Arabinosides Halohydrins Sanofi Hydroxymethyl compounds