The microtubule-active antitumor compound TTI-237 has both paclitaxel-like and vincristine-like properties.
OBJECTIVE
To compare TTI-237 (5-chloro-6-[2,6-difluoro-4-[3-(methylamino)propoxy]phenyl]-N-[(1S)-2,2,2-trifluoro-1-methylethyl]-[1, 2, 4]triazolo[1,5-a]pyrimidin-7-amine butanedioate) with paclitaxel and vincristine in order to better understand the properties of this new anti-microtubule agent.


METHODS
Tubulin polymerization and depolymerization were followed by turbidimetric assays. Effects of compounds on the binding of [(3)H]guanosine triphosphate ([(3)H]GTP) to tubulin were studied by competition binding assays. Effects of compounds on the phosphorylation of a panel of intracellular proteins were determined by flow cytometry using phosphoprotein-specific antibodies.


RESULTS
At low molar ratios of TTI-237:tubulin heterodimer (about 1:30), TTI-237 enhanced depolymerization kinetics in response to low temperature, but stabilized the aggregates at higher ratios (about 1:4). Similarly, the aggregates induced in microtubule protein by TTI-237 were depolymerized by excess Ca(++) at low TTI-237:tubulin-heterodimer molar ratios, but were stable at higher ratios. TTI-237 inhibited the exchange of [(3)H]GTP at the exchangeable nucleotide site of the tubulin heterodimer, and was similar to vincristine in its effects on the phosphorylation of eight intracellular proteins in HeLa cells.


CONCLUSIONS
TTI-237 has properties that distinguish it from typical vinca-site and taxoid-site ligands, and therefore it may exemplify a new class of microtubule-active compounds.
Beyer
Carl F
CF
Department of Discovery Oncology, Wyeth Research, Pearl River, NY 10965, USA. beyerc@wyeth.com
Zhang
Nan
N
Hernandez
Richard
R
Vitale
Danielle
D
Nguyen
Thai
T
Ayral-Kaloustian
Semiramis
S
Gibbons
James J
JJ
D000970:Antineoplastic Agents / Q000494:pharmacology*; D001704:Biopolymers; D003080:Cold Temperature; D005434:Flow Cytometry; D006160:Guanosine Triphosphate / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D006846:Hydrocarbons, Halogenated / Q000494:pharmacology*; D008870:Microtubules / Q000187:drug effects*; D017239:Paclitaxel / Q000494:pharmacology*; D011869:Radioligand Assay; D014230:Triazoles / Q000494:pharmacology*; D014404:Tubulin / Q000187:drug effects / Q000378:metabolism; D014750:Vincristine / Q000494:pharmacology*
D000970:Antineoplastic Agents; D001704:Biopolymers; D006846:Hydrocarbons, Halogenated; D014230:Triazoles; D014404:Tubulin; D014750:Vincristine; D006160:Guanosine Triphosphate; C521494:cevipabulin; D017239:Paclitaxel