Evaluation of C-5 propynyl pyrimidine-containing oligonucleotides in vitro and in vivo.
Inclusion of C-5 propynyl pyrimidines in phosphorothioate antisense oligonucleotides (ASOs) has been shown to significantly increase their potency for inhibiting gene expression in vitro. This increased potency is believed to be the result of enhanced binding affinity to target RNA. Our results show that C-5 propynyl pyrimidine-modified oligonucleotides caused an increase in the melting temperature (T(m)) of both oligodeoxynucleotides (ODNs) and 2'-O-(2-methoxy)ethyl (2'-MOE)-modified oligonucleotides. The in vitro data show a moderate increase in potency for an antisense oligodeoxynucleotide containing C-5 propynyl pyrimidines targeting the murine PTEN (MMAC1) transcript. Second-generation 2'-MOE chimeric ASOs containing C-5 propynyl pyrimidines showed no improvement in potency in PTEN target reduction in vitro or in vivo compared to their nonpropyne-modified parent. These results suggest that increasing affinity for target RNA beyond that achieved with the 2'-MOE modification does not further increase potency in cell-based assays. To evaluate whether this observation held true for in vivo applications, we evaluated both compounds in mice. We were unable to establish a dose-response relationship with C-5 propynyl pyrimidine-modified ODNs because of severe toxicity. The toxicity was characterized by mortality in animals receiving 50 mg/kg and an increase in infiltrating cells and apoptotic cells in livers of mice receiving 20 mg/kg. C-5 propynyl pyrimidine-modified chimeric oligonucleotides exhibited decreased hepatotoxicity compared with C-5 propynyl-modified ODNs but did not exhibit an increase in potency compared with unmodified chimeric oligonucleotides. The hepatotoxicity could be further limited if incorporation of propynyl pyrimidines was restricted to 2'-MOE nucleosides.
Shen
Lijiang
L
Isis Pharmaceuticals, Carlsbad, CA 92008, USA.
Siwkowski
Andrew
A
Wancewicz
Edward V
EV
Lesnik
Elena
E
Butler
Madeline
M
Witchell
Donna
D
Vasquez
Guillermo
G
Ross
Bruce
B
Acevedo
Oscar
O
Inamati
Gopal
G
Sasmor
Henri
H
Manoharan
Muthiah
M
Monia
Brett P
BP
D000410:Alanine Transaminase / Q000097:blood; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001219:Aspartate Aminotransferases / Q000097:blood; D001483:Base Sequence; D001921:Brain / Q000098:blood supply; D002460:Cell Line; D004334:Drug Administration Schedule; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D007274:Injections, Intraperitoneal; D008099:Liver / Q000187:drug effects; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D015394:Molecular Structure; D016376:Oligonucleotides, Antisense / Q000008:administration & dosage / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology* / Q000633:toxicity; D009929:Organ Size / Q000187:drug effects; D011742:Pyrimidine Nucleotides / Q000737:chemistry*; D012313:RNA / Q000032:analysis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D014162:Transfection
D016376:Oligonucleotides, Antisense; D011742:Pyrimidine Nucleotides; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D012313:RNA; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase