Busulfan

Absorption

Completely absorbed from the gastrointestinal tract. Busulfan is a small, highly lipophilic molecule that crosses the blood-brain-barrier. The absolute bioavailability, if a single 2 mg IV bolus injection is given to adult patients, is 80% ± 20%. In children (1.5 - 6 years old), the absolute bioavailability was 68% ± 31%. When a single oral dose is given to patients, the area under the curve (AUC) was 130 ng?hr/mL. The peak plasma concentration when given orally is 30 ng/mL (after dose normalization to 2 mg). It takes 0.9 hours to reach peak plasma concentration after dose normalization to 4 mg.

Toxicity

Signs of overdose include allergic reaction, unusual bleeding or bruising, sudden weakness or unusual fatigue, persistent cough, congestion, or shortness of breath; flank, stomach or joint pain; pronounced nausea, vomiting, diarrhea, dizziness, confusion, or darkening of the skin, chills, fever, collapse, and loss of consciousness.

Description

Chemically, busulfan is classified as an alkyl sulfonate. One or both of the methylsulfonate ester moieties can be displaced by the nucleophilic N7 of guanine, leading to monoalkylated and cross-linked DNA. The extent of alkyl sulfonate–mediated DNA interstrand cross-linking has been shown to vary with the length of the alkyl chain between sulfonate esters, with the tetramethylene-containing busulfan showing less interstrand cross-linking capability than hexamethylene, methylene, or octamethylene analogues. Intrastrand cross-linking also occurs, preferentially at 5′-GA-3′ but also at 5′-GG-3′ sequences. Alkylation of Cys sulfhydryl groups is yet another mechanism of cytotoxicity.

Description

Busulfan, a common name for the dimethanesulfonate ester of 1,4-butanediol, is an older chemotherapy drug sold under the trade names Myleran, Busulfex, and many others. It was described as a leukemia treatment by inventor Geoffrey M. Timmins in a 1959 US Patent to Burroughs Wellcome (Tuckahoe, NY; now part of GlaxoSmithKline).
Busulfan’s mode of action is as a bifunctional alkylating agent, which has an immunosuppressive effect on bone marrow. It stops tumor growth by cross-linking guanine bases in DNA double-helix strands. This makes the strands unable to uncoil and separate. Because this process is necessary for DNA replication, the tumor cells can no longer divide. In addition, busulfan adds methyl groups where they do not belong, which leads to DNA miscoding.
Almost a decade before the Timmins patent was issued, busulfan was implicated in the death of a 67-year-old breast cancer patent. An anonymous 1950 article in the British Medical Journal titled “Death after new drug” compared busulfan to the properties of nitrogen mustards, war gases that were also being tried as anticancer agents. The article suggested that busulfan behaved anomalously in the body compared with other compounds with similar properties.
Despite this mishap and its dangerous properties (see the hazard information table), busulfan continued to be developed as a cancer drug. In 1999, it was approved by the US Food and Drug Administration for treating chronic myeloid leukemia. Its use was soon reduced because of the emergence of Novartis’s imatinib1, which was approved by the FDA for treating cancer 2 years after busulfan. Imitanib, however, has its own adverse effects and is more expensive, and busulfan is still on the market. It is currently listed as an orphan drug by the FDA.
1. CAS Reg. No. 152459-95-5.

Chemical properties

White Crystalline Solid

Originator

Myleran,Burroughs- Wellcome,US,1954

The Uses of Busulfan

Busulfan USP (Myleran) is used to treat Chronic granulocytic leukemia; other myeloproliferative disorders.

The Uses of Busulfan

Alkylating agent with antileukemic activity. Antineoplastic

The Uses of Busulfan

Antineoplastic alkylating agent, the palliative treatment of chronic myeloid leukemia, and insect sterilant.

What are the applications of Application

Busulfan is a DNA alkylating agent that causes DNA damage by cross-linking DNA and proteins

Indications

For use in combination with cyclophosphamide as a conditioning regimen prior to allogeneic hematopoietic progenitor cell transplantation for chronic myelogenous (myeloid, myelocytic, granulocytic) leukemia (FDA has designated busulfan as an orphan drug for this use). It is also used as a component of pretransplant conditioning regimens in patients undergoing bone marrow transplantation for acute myeloid leukemia and nonmalignant diseases.

Background

Busulfan is a bifunctional alkylating agent, having a selective immunosuppressive effect on bone marrow. It is not a structural analog of the nitrogen mustards. It has been used in the palliative treatment of chronic myeloid leukemia (myeloid leukemia, chronic), but although symptomatic relief is provided, no permanent remission is brought about. According to the Fourth Annual Report on Carcinogens (NTP 85-002, 1985), busulfan is listed as a known carcinogen.

Definition

ChEBI: A methanesulfonate ester that is butane-1,4-diol in which the hydrogens of the hydroxy groups are replaced by methanesulfonyl groups. An alkylating antineoplastic agent, it is used for the treatment of chronic myeloid leukemia (although it has been largely replaced by newer drugs). It is also used as an insect sterilant.

Indications

Busulfan (Myleran) is a bifunctional methanesulfonic ester that forms intrastrand cross-linkages with DNA. The drug is well absorbed after oral administration and has a plasma half-life of less than 5 minutes. Metabolites and degradation products are excreted primarily in the urine.
Busulfan is used in the palliative treatment of chronic granulocytic leukemia. Daily oral therapy results in decreased peripheral white blood cells and improved symptoms in almost all patients during the chronic phase of the disease. Excessive uric acid production from rapid tumor cell lysis should be prevented by coadministration of allopurinol.
At usual therapeutic dosages, busulfan is selectively toxic to granulocyte precursors rather than lymphocytes. Thrombocytopenia and anemia and less commonly, nausea, alopecia, mucositis, and sterility also may occur. Unusual side effects of busulfan include gynecomastia, a general increase in skin pigmentation, and interstitial pulmonary fibrosis.

Manufacturing Process

3.6 grams of redistilled 1,4-butanediol were dissolved in 10 ml of pyridine and the solution was cooled in ice and water. 9.6 grams of redistilled methanesulfonyl- chloride were added dropwise at such a rate that the temperature did not rise above 20°C. The solution was then allowed to stand at room temperature to; 30 minutes, during which time the temperature rose to 60°C. A thick precipitate of pyridine hydrochloride was formed.
The mass was cooled in ice water and was treated with 30 ml of ice cold water. On agitation, a white crystalline precipitate was formed. This was filtered off and washed well with ice cold water and allowed to drain on the pump. It weighed 7.8 grams and had a melting point of 100°C. 3.5 grams of the material were recrystallized from acetone and ether to give small white needles, having a melting point of 106°-107°C, unchanged by further recrystallization.

brand name

Myleran (GlaxoSmithKline).

Therapeutic Function

Antineoplastic

General Description

White crystals or powder.

General Description

As an alternative to utilizing aziridines as electrophilic species,it was found that simply utilizing a carbon chain terminated atboth ends by leaving groups gave compounds capable of actingas cross-linking agents.Busulfan utilizestwo sulfonate functionalities as leaving groups separated by afour-carbon chain that reacts with DNA to primarily form intrastrandcross-link at 5'-GA-3' sequences.The sulfonatesare also subject to displacement by the sulfhydryl functionsfound in cysteine and glutathione, and metabolic products areformed as a result of nucleophilic attack by these groups togenerate sulfonium species along with methane sulfonicacid.This is followed by conversion to tetrahydrothiophene,and further oxidation products are subsequently produced togive the sulfoxide and sulfone. The cyclic sulfone known assulfolane may be further oxidized to give 3-hydroxysulfolane.

General Description

Busulfan is available as 2-mg tablets for oral administrationand 10-mL vials for IV administration in the treatment ofchronic myelogenous leukemia (CML) and in high-dosetherapy for refractory leukemia with bone marrow transplant.The agent is well absorbed when given orally, well distributedinto tissues, and crosses the blood-brain barrier.Metabolism occurs in the liver to give mainly methane sulfonic acid by the action of glutathione-S-transferase. Other identified metabolites in humanshave included tetrahydrothiophene-1-oxide, sulfalene,primarily in the urine, and the terminal elimination half-lifeis 2.5 hours. Adverse effects include dose-limiting myelosuppression;nausea and vomiting that occur commonly butare generally mild; and pulmonary symptoms including interstitialpulmonary fibrosis, which is referred to as “busulfanlung,” occurs belatedly (1–10 years posttreatment) andalthough rare, it is severe. Other adverse effects includemucositis, skin rash, impotence, amenorrhea, infertility, hepatoxicity,insomnia, anxiety, and an increased risk of secondarymalignancies. At normal doses, the agent is welltolerated except for the myelosuppression that occurs. Thishas allowed for high-dose therapy with the agent when accompaniedby bone marrow transplant to counter the myelosuppressiveeffects.

Air & Water Reactions

Busulfan is an alkylating agent which hydrolyzes in water. .

Reactivity Profile

Busulfan is an alkylating agent which hydrolyzes in water. . Strong reducers may yield hydrogen sulfide.

Hazard

Extremely toxic, carcinogen, clastogenic, teratogenic, immunosuppressive, delayed bone marrow aplasia, cataracts, pigmentation, pulmonary thrombosis, cardiotoxic effects, thrombocytopenia.

Fire Hazard

Flash point data for Busulfan are not available. Busulfan is probably combustible.

Pharmacokinetics

Busulfan is an antineoplastic in the class of alkylating agents and is used to treat various forms of cancer. Alkylating agents are so named because of their ability to add alkyl groups to many electronegative groups under conditions present in cells. They stop tumor growth by cross-linking guanine bases in DNA double-helix strands - directly attacking DNA. This makes the strands unable to uncoil and separate. As this is necessary in DNA replication, the cells can no longer divide. In addition, these drugs add methyl or other alkyl groups onto molecules where they do not belong which in turn leads to a miscoding of DNA. Alkylating agents are cell cycle-nonspecific and work by three different mechanisms, all of which achieve the same end result - disruption of DNA function and cell death. Overexpression of MGST2, a glutathione s-transferase, is thought to confer resistance to busulfan. The role of MGST2 in the metabolism of busulfan is unknown however.

Clinical Use

Busulfan is used in the treatment of chronic myelogenous leukemia and can be administered either orally or by IV infusion.

Side Effects

Serious bone marrow hypoplasia and myelosuppression are possible with this agent, and recovery from busulfaninduced pancytopenia can take up to 2 years.

Safety Profile

Confirmed carcinogen producing leukemia, kidney, and uterine tumors. Experimental neoplastigenic and tumorigenic data. Poison by ingestion, subcutaneous, intraperitoneal, intravenous, and possibly other routes. Ingestion by pregnant women can cause cancer of the reproductive system of the fetus includtng the uterus. Human teratogenic effects by ingestion and possibly other routes include developmental abnormaltties of the eye, ear, craniofacial area including the nose and tongue, gastrointestinal system, endocrine system, urogenital system, and other unspecified areas. Other human reproductive effects by ingestion and possibly other routes include: impotence, changes in the uterus, cervix, and vagina, and menstrual-cycle dtsorders. Experimental reproductive effects. Human systemic effects by ingestion: general arteriolar or venous ddation of the eye, changes in structure or function of salivary glands. When heated to decomposition it emits toxic fumes of SOx. See also SULFONATES.

Synthesis

Busulfan, 1,4-butandioldimethansulfonate (30.2.3.1), is made by reacting butandiol with methanesulfonyl chloride.

Potential Exposure

Those involved in the manufacture,formulation, or use of this compound which finds application as an insect sterilant, and as a chemotherapeutic agenttaken orally to treat some kinds of leukemia.

Veterinary Drugs and Treatments

Busulfan may be useful in the adjunctive therapy of chronic granulocytic leukemias or polycythemia vera in small animals. Not commonly used in veterinary medicine.

Drug interactions

Potentially hazardous interactions with other drugs
Antibacterials: concentration increased by metronidazole.
Antipsychotics: avoid with clozapine, increased risk of agranulocytosis.
Antifungals: metabolism inhibited by itraconazole, monitor for signs of busulfan toxicity.

First aid

If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately with wateror normal saline for 20
30 min, occasionally lifting upperand lower lids. Seek medical attention immediately. If thischemical contacts the skin, remove contaminated clothingand wash immediately with soap and water. Seek medicalattention immediately. If this chemical has been inhaled,remove from exposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped.Transfer promptly to a medical facility. When this chemicalhas been swallowed, get medical attention. Give large quantities of water and induce vomiting. Do not make an unconscious person vomit.

Carcinogenicity

1,4-Butanediol dimethanesulfonate is known to be a human carcinogen based on sufficient evidence of carcinogenicity from studies in humans.

Metabolism

Busulfan is extensively metabolizes in the hepatic. Busulfan is predominantly metabolized by conjugation with glutathione, both spontaneously and by glutathione S-transferase (GST) catalysis. GSTA1 is the primary GST isoform that facilitates the the metabolism of busulfan. Other GST isoforms that are also involved are GSTM1 and GSTP1. At least 12 metabolites have been identified among which tetrahydrothiophene, tetrahydrothiophene 12-oxide, sulfolane, and 3-hydroxysulfolane were identified. These metabolites do not have cytotoxic activity.

Metabolism

Busulfan is extensively metabolised in the liver, mainly by conjugation with glutathione, either spontaneously or mediated by the enzyme glutathione-S-transferase. About 12 inactive metabolites have been identified, which are excreted in the urine. About 1% of busulfan is excreted unchanged. Elimination in the faeces is considered to be negligible.

storage

Color Code—Blue: Health Hazard/Poison: Storein a secure poison location. Store in a refrigerator and protect from exposure to oxidizers or moisture. A regulated,marked area should be established where this chemical is handled, used, or stored in compliance with OSHAStandard 1910.1045.

Shipping

The label requirement for medicine, solid, toxic,n.o.s. is “POISONOUS/TOXIC MATERIALS.” Medicine,solid, toxic, n.o.s., fall in Hazard Class 6.1 and busulfanfalls in Packing Group II.

Incompatibilities

Oxidizers, moist air, and water.

References

[1]. probin v, wang y, zhou d. busulfan-induced senescence is dependent on ros production upstream of the mapk pathway. free radic biol med, 2007, 42(12): 1858-1865.
[2]. probin v, wang y, bai a, et al. busulfan selectively induces cellular senescence but not apoptosis in wi38 fibroblasts via a p53-independent but extracellular signal-regulated kinase-p38 mitogen-activated protein kinase-dependent mechanism. j pharmacol exp ther, 2006, 319(2): 551-560.
[3]. choi yj, ok dw, kwon dn, et al. murine male germ cell apoptosis induced by busulfan treatment correlates with loss of c-kit-expression in a fas/fasl- and p53-independent manner. febs lett, 2004, 575(1-3): 41-51.