Preclinical evaluation of EC145, a folate-vinca alkaloid conjugate.
We recently developed a new group of folate-conjugated Vinca alkaloids, one of which, EC145, emerged as a candidate for clinical development. Brief treatment of nude mice bearing approximately 100 mm(3) folate receptor-positive human xenografts led to complete response (CR) in 5/5 mice and cures (i.e., remission without a relapse for >90 days post-tumor implantation) in 4/5 mice. Multiple CRs and cures were also noted when EC145 was used to treat mice initially bearing tumors as large as 750 mm(3). Likewise, complete cures (5/5) resulted following the treatment of an aggressive folate receptor-positive J6456 lymphoma model. The activity of EC145 was not accompanied by noticeable weight loss or major organ tissue degeneration. Furthermore, no significant antitumor activity (0/5 CR) was observed in EC145-treated animals that were co-dosed with an excess of a benign folate ligand, thus demonstrating the target-specific activity of EC145. The enhanced therapeutic index due to folate conjugation was also evidenced by the fact that the unconjugated drug (desacetylvinblastine monohydrazide) was found to be completely inactive when administered at nontoxic dose levels and only marginally active when given at highly toxic dose levels. Subsequent dose regimen studies confirmed that EC145 given on a more frequent, qdx5 schedule resulted in the most effective antitumor response as compared with an equivalent total dose given on thrice- or single-injection-per-week schedule. Taken together, these studies show that EC145 has significant antiproliferative activity and tolerability, thus lending support to an ongoing phase 1 trial for the treatment of advanced malignancies.
Reddy
Joseph A
JA
Endocyte, Inc., West Lafayette, Indiana 47906, USA.
Dorton
Ryan
R
Westrick
Elaine
E
Dawson
Alicia
A
Smith
Terri
T
Xu
Le-Cun
LC
Vetzel
Marilynn
M
Kleindl
Paul
P
Vlahov
Iontcho R
IR
Leamon
Christopher P
CP
D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D004334:Drug Administration Schedule; D004354:Drug Screening Assays, Antitumor; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology*; D006801:Humans; D007624:KB Cells; D008223:Lymphoma / Q000188:drug therapy; D051379:Mice; D008807:Mice, Inbred BALB C; D014748:Vinca Alkaloids / Q000008:administration & dosage / Q000494:pharmacology*; D023041:Xenograft Model Antitumor Assays
D000970:Antineoplastic Agents; C520389:EC145; D014748:Vinca Alkaloids; D005492:Folic Acid