In vitro blood distribution and plasma protein binding of the tyrosine kinase inhibitor imatinib and its active metabolite, CGP74588, in rat, mouse, dog, monkey, healthy humans and patients with acute lymphatic leukaemia.
OBJECTIVE
To determine blood binding parameters of imatinib and its metabolite CGP74588 in humans and non-human species.


METHODS
The blood distribution and protein binding of imatinib and CGP74588 were determined in vitro using (14)C labelled compounds.


RESULTS
The mean fraction of imatinib in plasma (f(p)) was 45% in dog, 50% in mouse, 65% in rat, 70% in healthy humans and up to 92% in acute lymphatic leukaemia (AML) patients. Similarly, f(p) for CGP74588 was low in dog and monkey (30%), higher in rat, mouse and humans (70%) and highest in some AML patients (90%). The unbound fraction of imatinib and CGP74588 in plasma was lower in rat, mouse, healthy humans and AML patients (2.3-6.5% at concentrations < or = 5000 ng ml(-1)) compared to monkey and dog (7.6-19%). Both compounds displayed high binding to human alpha(1)-acid glycoprotein. AML patients had a reduced haematocrit and showed greatest variability in their blood binding parameters.


CONCLUSIONS
Imatinib and CGP74588 displayed very similar blood binding parameters within all species/groups investigated. The five species clustered into two distinct groups with rat, mouse and humans being clearly different from dog and monkey. For both compounds, higher protein binding was associated with a decreased partitioning into blood cells.
Kretz
Olivier
O
Novartis Pharma AG, Basel, Switzerland. olivier.kretz@pharma.novartis.com
Weiss
H Markus
HM
Schumacher
Martin M
MM
Gross
Gerhard
G
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000970:Antineoplastic Agents / Q000097:blood / Q000378:metabolism*; D001549:Benzamides; D004285:Dogs; D005260:Female; D006801:Humans; D000068877:Imatinib Mesylate; D008252:Macaca fascicularis; D008297:Male; D051379:Mice; D008875:Middle Aged; D010879:Piperazines / Q000097:blood / Q000378:metabolism*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000097:blood / Q000378:metabolism*; D011485:Protein Binding; D011743:Pyrimidines / Q000097:blood / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D000970:Antineoplastic Agents; D001549:Benzamides; C464561:CGP 74588; D010879:Piperazines; D011743:Pyrimidines; D000068877:Imatinib Mesylate