Lack of in Vivo Cross-Resistance with 4′-Thio-ara-c Against Drug-Resistant Murine P388 and L1210 Leukemias

4′-Thio-β-D-arabinofuranosylcytosine (4′-thio-ara-C), which has shown a broad spectrum of antitumor activity against human tumor systems in mice and is undergoing clinical trials, was evaluated for cross-resistance to seven clinical agents in order to identify potentially useful guides for patient selection for further clinical trials of 4′-thio-ara-C and possible noncross-resistant drug combinations with 4′-thio-ara-C.