Zamboni William C, Jung Laura L, Strychor Sandra, Joseph Erin, Zamboni Beth A, Fetterman Sarah A, Sidone Brian J, Burke Thomas G, Curran Dennis P, Eiseman Julie L
Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, PA, 15213, USA.
Invest New Drugs. 2008 Oct;26(5):399-406. doi: 10.1007/s10637-007-9109-9. Epub 2008 Feb 2.
DB-67 is a silatecan, 7-silyl-modified camptothecin, with enhanced lipophilicity and increased blood stability of the active-lactone ring. The generation of a liposomal formulation of DB-67 may be an attractive method of intravenous (IV) administration and may maintain DB-67 in the active-lactone form. We evaluated the tissue and plasma disposition of DB-67 lactone and hydroxy acid after administration of non-liposomal (NL) and liposomal (L) DB-67 in severe combined immunodeficient (SCID) mice.
NL-DB-67 and L-DB-67 10 mg/kg IV x 1 were administered via a tail vein in SCID mice. After dosing, mice (n = 3 per time point) were euthanized and blood ( approximately 1 ml) and tissue were collected from 5 min to 48 h after administration. DB-67 lactone and hydroxy acid concentrations in plasma and DB-67 total (sum of lactone and hydroxyl acid) concentrations in tissues were determined by high-performance liquid chromatography (HPLC) with fluorescence detection.
Clearance of DB-67 lactone after administration of NL-DB-67 and L-DB-67 were 1.6 and 3.5 l/h/m(2), respectively; DB-67 lactone half-lives after administration of NL-DB-67 and L-DB-67 were 1.4 and 0.9 h, respectively. The percentages of DB-67 lactone in plasma after administration of NL-DB-67 and L-DB-67 were 92% and 89%, respectively. Liver, kidney, spleen, and lung tissues had longer exposure times to DB-67 after administration of L-DB-67 compared with NL-DB-67.
In plasma, the majority of DB-67 remained in the lactone form after administration of NL-DB-67 and L-DB-67. The plasma disposition of DB-67 was similar after administration of NL-DB-67 and L-DB-67, suggesting that most of the DB-67 is immediately released from the L-DB-67 formulation. Following administration of L-DB-67, the higher and longer exposure of DB-67 in the spleen, as compared with NL-DB-67, is consistent with splenic clearance of liposomes by the reticuloendothelial system.
