Pharmacokinetics and biodistribution of methotrexate conjugated to mannosyl human serum albumin.

The superior efficacy of mannosylated neoglycoprotein-conjugated methotrexate, compared with free drug, in eliminating the parasite burden in both the in-vitro macrophage model and in-vivo mouse model of visceral leishmaniasis has been demonstrated previously. In the present study it was found that: (i) methotrexate conjugated to mannosyl human serum albumin (Man-HSA) was taken up rapidly by the liver and spleen, whereas the free drug was taken up by the kidney; (ii) uptake of the conjugate was ten-fold more efficient in liver macrophages (Kupffer cells) than in hepatocytes; (iii) most of the drug conjugate reached the lysosomes of Kupffer cells; and (iv) the active drug was released in the lysosomes of macrophages to act on Leishmania parasites.