Pixantrone

Danger

H300 (50%): Fatal if swallowed [Danger Acute toxicity, oral]

P203, P260, P262, P264, P270, P271, P280, P284, P301+P316, P302+P352, P304+P340, P308+P316, P316, P318, P320, P321, P330, P361+P364, P403+P233, P405, and P501 (click each P-code to see the statement)

Aggregated GHS information provided per 2 reports by companies from 2 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

L - Antineoplastic and immunomodulating agents

QL - Antineoplastic and immunomodulating agents

Pixantrone has a wide range of antitumor activity, especially in terms of treating leukemias and lymphomas [3]. Pixantrone lacks cardio-toxic effects. It has postulated that his is because of its redox inactivity and lack and inhibition of doxorubicinol formation in human myocardium. [3]

Pixantrone is an aza-anthracenedione which acts as a DNA intercalator. By intercalating between DNA, with modest affinity, it stimulates DNA cleavage by topoisomerase II. (Pixantrone acts as a poison to topoisomerase II by stabilizing protein-DNA complexes which are usually transient, giving rise to double stranded DNA breaks.) However, pixantrone is believed to have additional mechanisms of action as its potency does not correlate to the degree of double stranded DNA breaks observed. It has been postulated that this second mechanism may be pixantrone-DNA adduct formation. [1] It is important to note that the formation of a pixtantrone-DNA adduct requires pixantrone activation by formaldehyde. Formadehyde may be generated in vitro by hydrogen peroxide, and is derived by various sources in biological systems. It is present in low levels as a result of normal metabolism, and may be present in elevated levels in some haematolgical malignancies. [1] The formation of pixantrone-DNA adducts is thus feasible, and it is believed that a long pixantrone-DNA adduct half life has the potential to maximize DNA damage. It may do so by enhancing the disruption of DNA replication and transcription, and potentially by encourage apoptosis. [1] In explanation of pixantrones lack of cardiotoxicity, it has been elucidated that pixantrone is structurally similar to mitoxantrone; however, instead of a 5,8-dihydroxyphenyl ring (thought to be responsible for cardiotoxicity) it has a nitrogen heteroatom. This nitrogen heteroatom helps to create additional hydrogen bonding sites amd increases pixantrone interaction with DNA and topoisomerase II. [2] Pixantrone's lack of a hydroquinone is believed to render it resistant to one electron reduction. In contrast, doxorubicin - which contains a hydroquinone - experiences one electron redox cycling and ROS formation via NADH dehydrogenase. [3] Pixantrone also does not bind iron, and thus does not produce ROS by redox cycling between oxidative states of iron, as other anthracyclines do. [2] The first line agent doxorubicin is cardiotoxic, in part, due to its ability to redox activate the superoxide anion and hydrogen peroxide, and form a long-lived secondary alcohol metabolite: doxorubicinol. [3] Clearance of doxorubicin from myocardial tissue is incomplete, and it can be found months or years after the last administration. [3] In doxorubicin treated ex vivo cardiac strips, pixantrone formed an N-dealkylated product that inhibited metabolism of residual doxorubicin into doxorubicinol. Additionally, in ex vivo human myocardial strips (doxorubicin naive, and doxorubicin pretreated) pixantrone showed high cardiac uptake without formation of superoxide anion or hydrogen peroxide. Pixantrones lack of cardiotoxicity is thus attributed to its redox inactivity and inhibition of doxorubicinol formation. [3]

Pixantrone does not form secondary alcohol metabolites. [2] Pixantrone hydrolyzes extensively to CT-45886 which is believed to inhibit doxol formation by displacing DOX from the active site of reductases. CT4889 and CT-45890 are also formed.[3]

Compounds that inhibit the activity of DNA TOPOISOMERASE II. Included in this category are a variety of ANTINEOPLASTIC AGENTS which target the eukaryotic form of topoisomerase II and ANTIBACTERIAL AGENTS which target the prokaryotic form of topoisomerase II.

Intravenous administration results in a rapid distribution followed by a slow elimination. [2] In ex vivo myocardial strips, pixantrone is taken up to a higher degree than mitoxantrone. In myocardial strips which are doxorubicin naive pixantrone displays higher uptake than in DOX-loaded myocardial strips. DOX clearance causes membrane effects which may be responsible for this observation. DOX clearance involves rapid passive diffusion through one side of the membrane followed by "flip flop" reorientation of the lipid bilayer. This disorganization of lipids is believed to impair membrane penetration by pixantrone. [3]

Fecally and renally excreted. Urinary elimination of unchanged drug is less than 10%. [2]

9.7-29.7 L/kg. [2]

Plasma clearance is 0.75 - 1.31 L/h/kg. [2]