A 20-mer phosphorothioate oligodeoxynucleotide (ODN) directed against human C-raf kinase (CGP 69846A or ISIS 5132) was analyzed for its antitumor activity either alone or in combination therapy. Combination studies with CGP 69846A and standard chemotherapeutic agents (cisplatin, mitomycin C, tamoxifen, or Adriamycin) were performed in nude mice that had been transplanted s.c. with a variety of human tumors (breast, prostate, colon, small cell lung, large cell lung, and squamous lung carcinomas). For the majority of the combinations studied, additive antitumor effects with CGP 69846A and the cytotoxins were found. The combination of CGP 69846A with cisplatin or mitomycin C showed superadditive antitumor activities against NCI-H69 small cell lung carcinomas with complete tumor responses. CGP 69846A, in combination with cisplatin, showed superadditive antitumor effects against PC3 human prostate carcinomas with tumor cures, and in combination with mitomycin C, superadditive antitumor effects of CGP 69846A with tumor cures against NCI-H460 large cell lung carcinoma were found. These effects appeared to be sequence-specific because a mismatched control ODN was completely without effect as a single agent against NCI-H69 human small cell lung cancers. The combination of the mismatched control ODN with mitomycin C or cisplatin did not influence the antitumor activity of the cytotoxins against NCI-H69 human small cell lung cancers, indicating that the superadditive antitumor effects observed for CGP 69846A in combination with cisplatin or mitomycin C are the result of a sequence-specific mechanism of action in NCI-H69 human small cell lung cancers.

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