Pegylated liposomal formulations contain
lipid conjugated to
polyethylene glycol. The disposition of encapsulated
drug is dictated by the composition of the
liposome, thus altering the pharmacokinetic (PK) profile of the
drug. Allometric scaling is based on a power-log relationship between
body weight (W) and drug clearance (CL) among mammals and has been used to compare the disposition of nonliposomal drugs across species. The objectives of this study were to use allometric scaling to: (1) compare the disposition of pegylated liposomal drugs across speciesand determine the best scaling model and (2) predict PK parameters of pegylated liposomal drugs in humans. The PK of pegylated liposomal
CKD-602 (S-CKD602),
doxorubicin (Doxil®), and
cisplatin (SPI-077) were compared. PK studies ofS-CKD602, Doxil®, and
SPI-077 were performed at the maximum tolerated dose (MTD) in male and female mice, rats, dogs and patients with refractory solid
tumors. The allometric equation used to evaluate the relationship between W and CL in each species was CL = a(W)(m) (a = empirical coefficient; m = allometric exponent). Substitution of physiological variables other than
body weight, such as factors representative of the mononuclear phagocyte system (MPS) were evaluated. Dedrick Plots and Maximum Life-Span Potential (MLP) were used to determine scaling feasibility. Standard allometry demonstrated a relationship between clearance of S-CKD602, Doxil®, and
SPI-077 and body, spleen, liver, and kidney weights, total monocyte count, and spleen and liver blood flow. However, using scaling to predict CL of these agents in humans often resulted in differences >30%. Despite a strong correlation between
body weight and MPS-associated variables with CL among preclinical species, the use of the equations did not predict CL. Thus, new methods of allometric scaling and measures of MPS function need to be developed.