Hypoxia-selective 3-alkyl 1,2,4-benzotriazine 1,4-dioxides: the influence of hydrogen bond donors on extravascular transport and antitumor activity.
Tirapazamine (TPZ) and related 1,2,4-benzotriazine 1,4 dioxides (BTOs) are selectively toxic under hypoxia, but their ability to kill hypoxic cells in tumors is generally limited by their poor extravascular transport. Here we show that removing hydrogen bond donors by replacing the 3-NH2 group of TPZ with simple alkyl groups increased their tissue diffusion coefficients as measured in multicellular layer cultures. This advantage was largely retained using solubilizing 3-alkylaminoalkyl substituents provided these were sufficiently lipophilic at pH 7.4. The high reduction potentials of such compounds resulted in rates of metabolism too high for optimal penetration into hypoxic tissue, but electron-donating 6- and 7-substituents moderated metabolism. Pharmacokinetic/pharmacodynamic model-guided screening was used to select BTOs with optimal extravascular transport and hypoxic cytotoxicity properties for evaluation against HT29 human tumor xenografts in combination with radiation. This identified four novel 3-alkyl BTOs providing greater clonogenic killing of hypoxic cells than TPZ at equivalent host toxicity, with the 6-morpholinopropyloxy-BTO 22 being 3-fold more active.
Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, The University of Auckland, New Zealand. m.hay@auckland.ac.nz
Michael P
MP
Hay
Karin
K
Pchalek
Frederik B
FB
Pruijn
Kevin O
KO
Hicks
Bronwyn G
BG
Siim
Robert F
RF
Anderson
Sujata S
SS
Shinde
Victoria
V
Phillips
William A
WA
Denny
William R
WR
Wilson
D000818:Animals; D000970:Antineoplastic Agents / Q000138:chemical synthesis* / Q000493:pharmacokinetics / Q000494:pharmacology; D001692:Biological Transport; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D003131:Combined Modality Therapy; D003497:Cyclic N-Oxides / Q000138:chemical synthesis* / Q000493:pharmacokinetics / Q000494:pharmacology; D004058:Diffusion; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D006860:Hydrogen Bonding; D051379:Mice; D008954:Models, Biological; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000188:drug therapy / Q000378:metabolism / Q000532:radiotherapy; D013329:Structure-Activity Relationship; D014183:Transplantation, Heterologous; D014227:Triazines / Q000138:chemical synthesis* / Q000493:pharmacokinetics / Q000494:pharmacology; D014410:Tumor Stem Cell Assay
D000970:Antineoplastic Agents; D003497:Cyclic N-Oxides; D014227:Triazines