Role of lipophilicity in determining cellular uptake and antitumour activity of gold phosphine complexes.
OBJECTIVE
The lipophilic cation [Au(I)(dppe)2]+ [where dppe is 1,2-bis(diphenylphosphino)ethane] has previously demonstrated potent in vitro antitumour activity. We wished to determine the physicochemical basis for the cellular uptake of this drug, as well as of analogues including the 1:2 adducts of Au(I) with 1,2-bis(di-n-pyridylphosphino)ethane (dnpype; n = 2, 3 and 4), and to compare in vitro and in vivo antitumour activity.


RESULTS
Logarithmic IC50 values for the CH-1 cell line bore a parabolic dependence on drug lipophilicity, as measured either by high-performance liquid chromatography or by n-octanol-water partition. Cellular uptake of drug, as measured by inductively coupled plasma mass spectrometry, varied by over three orders of magnitude over the series. Logarithmic uptake had a parabolic dependence on drug lipophilicity but a linear relationship to logarithmic IC50 values. Free drug concentrations were determined under the culture conditions and logarithmic free drug IC50 values and uptake rates were linearly related to lipophilicity. Uptake of drug in vivo in tissue from murine colon 38 tumours was approximately proportional to the dose administered. Host toxicity varied according to lipophilicity with the most selective compound having an intermediate value. This compound was also the most active of those tested in vivo, giving a growth delay of 9 days following daily intraperitoneal dosing (10 days) at 4 micromol kg(-1) day(-1). It was also significantly more active than another lipophilic cation, MKT-077.


CONCLUSIONS
Alteration of lipophilicity of aromatic cationic antitumour drugs greatly affects cellular uptake and binding to plasma proteins. Changes in lipophilicity also affect host toxicity, and optimal lipophilicity may be a critical factor in the design of analogues with high antitumour activity.
McKeage
M J
MJ
Department of Pharmacology and Clinical Pharmacology, Faculty of Medical and Health Science, University of Auckland School of Medicine, New Zealand. m.mckeage@auckland.ac.nz
Berners-Price
S J
SJ
Galettis
P
P
Bowen
R J
RJ
Brouwer
W
W
Ding
L
L
Zhuang
L
L
Baguley
B C
BC
D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000493:pharmacokinetics* / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005260:Female; D006801:Humans; D008055:Lipids / Q000737:chemistry; D051379:Mice; D009368:Neoplasm Transplantation; D050607:Organogold Compounds; D009942:Organometallic Compounds / Q000737:chemistry / Q000493:pharmacokinetics* / Q000494:pharmacology; D009943:Organophosphorus Compounds / Q000737:chemistry / Q000493:pharmacokinetics* / Q000494:pharmacology; D010051:Ovarian Neoplasms / Q000378:metabolism*; D010720:Phosphines / Q000737:chemistry / Q000493:pharmacokinetics* / Q000494:pharmacology; D011485:Protein Binding; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D008055:Lipids; D050607:Organogold Compounds; D009942:Organometallic Compounds; D009943:Organophosphorus Compounds; D010720:Phosphines; C050185:bis(1,2-bis(diphenylphosphino)ethane)gold(I)