ICD-10 Specific code C91.0: Acute lymphoblastic leukaemia

Aclarubicin is an anthracycline antibiotic produced by Streptomyces galilaeus and also has potent antineoplastic activity. It is less cardiotoxic than doxorubicin and daunorubicin. The mechanism of action of aclarubicin is based on its capacity to insert its trisaccharide chain into the minor DNA groove: poison of topoisomerase I, inhibitor of topoisomerase II, eviction of histones from nucleosomes, but also inhibitor of the 20S proteasome.

Asparaginase hydrolyses asparagine to aspartic acid and ammonia. In contrast to normal cells, lymphoblastic tumour cells have a very limited capacity for synthesising asparagine because of a significantly reduced expression of asparagine synthetase. Therefore, they require asparagine which diffuses from the extracellular environment. As a result of asparaginase-induced asparagine depletion in serum, protein synthesis in lymphoblastic tumour cells is disturbed while sparing most normal cells.

Clofarabine is a purine nucleoside anti-metabolite. Its antitumour activity is believed to be due to 3 mechanisms. Clofarabine produces DNA polymerase inhibition resulting in termination of DNA chain elongation and/or DNA synthesis/repair and ribonucleotide reductase inhibition with reduction of cellular deoxynucleotide triphosphate (dNTP) pools. Clofarabine also produces disruption of mitochondrial membrane integrity with the release of cytochrome C and other proapoptotic factors leading to programmed cell death even in non-dividing lymphocytes.

Cyclophosphamide has been demonstrated to have a cytostatic effect in many tumour types. The active metabolites of cyclophosphamide are alkylating agents which transfer alkyl groups to DNA during the process of cell division, thus preventing normal synthesis of DNA.

Cytarabine (ARA-C) is metabolised in vivo to ARA-CTP phosphorylated compound. This competitively inhibits DNA polymerase and may also inhibit certain acid kinase enzymes.

Daunorubicin is an anthracycline glycoside antibiotic and is a potent antileukaemic agent. It also has immunosuppressant effects. Daunorubicin may involve binding to DNA by intercalation between base pairs and inhibition of DNA and RNA synthesis by template disordering and steric obstruction.

Idarubicin is a DNA intercalating anthracycline which interacts with the enzyme topoisomerase II and has an inhibitory effect on nucleic acid synthesis. Idarubicin has been shown to have a higher potency with respect to daunorubicin and to be an effective agent against murine leukaemia and lymphomas both by i.v. and oral routes.

Ifosfamide is an antineoplastic, a cytotoxic alkylating agent. It is a prodrug and shows no in vitro cytotoxic activity until activated by microsomal enzymes. The cytotoxic activity of ifosfamide (alkylation of the nucleophilic centres in the cells) is associated with the activated oxazaphosphorine ring hydroxylated at the C4 atom which interacts with DNA-DNA cross linking. This activity manifests itself by blocking the late S and early G2 phases of the cell cycle.

Mercaptopurine is an inactive pro-drug which acts as a purine antagonist but requires cellular uptake and intracellular anabolism to thioguanine nucleotides for cytotoxicity. The mercaptopurine metabolites inhibit de novo purine synthesis and purine nucleotide interconversions. The thioguanine nucleotides are also incorporated into nucleic acids and this contributes to the cytotoxic effects of the active substance.

Methotrexate (4-amino-10-methylfolic acid) is a folic acid antagonist which inhibits the reduction of folic acid and increase of tissue cells. Methotrexate enters the cell through an active transport mechanism of reduced folates. As a result of polyglutamation of methotrexate caused by the folylpolyglutamylate enzyme, the duration of the cytotoxic effect of the drug substance in the cell increases.

Methylprednisolone is a synthetic glucocorticoid and a methyl derivative of prednisolone. Methylprednisolone is a potent anti-inflammatory agent with the capacity to profoundly inhibit the immune system.

Pegaspargase is a covalent conjugate of Escherichia coli-derived L-asparaginase with monomethoxypolyethylene glycol. The mechanism of action of L-asparaginase is the enzymatic cleavage of the amino acid L-asparagine into aspartic acid and ammonia. Depletion of L-asparagine in blood results in inhibition of protein-synthesis, DNA-synthesis and RNA-synthesis, especially in leukaemic blasts which are not able to synthesise L-asparagine, thus undergoing apoptosis.

Prednisolone is a glucocorticoid which has anti-inflammatory activity. Naturally occurring glucocorticoids (hydrocortisone and cortisone), which also have salt-retaining properties, are used as replacement therapy in adrenocortical deficiency states. Their synthetic analogs are primarily used for their potent anti-inflammatory effects in disorders of many organ systems.

Thiotepa is a polyfunctional cytotoxic agent related chemically and pharmacologically to the nitrogen mustard. The radiomimetic action of thiotepa is believed to occur through the release of ethylene imine radicals that, as in the case of irradiation therapy, disrupt the bonds of DNA, e.g. by alkylation of guanine at the N-7, breaking the linkage between the purine base and the sugar and liberating alkylated guanine.

Vindesine is an antineoplastic agent derived from vinblastine, like the other vinca alkaloids it causes mitotic arrest in metaphase by binding to microtubular protein.