We examined development risks for new cancer drugs. For the full study period, the estimated clinical approval success rate for cancer compounds was 13.4% (9.9% for the first half of the study period, 19.8% for the second half). Small molecules had a somewhat higher clinical approval success rate than did large molecules (14.3 vs. 11.5%). Compounds studied solely in hematologic indications had markedly higher estimated clinical approval success rates than did compounds studied only in solid tumor indications (36.0 vs. 9.8%). The first, second, and third cancer indications pursued had estimated clinical approval success rates of 9.0, 8.2, and 6.9%, respectively. Success rates of second and third indications were found to be highly dependent on the success or failure of the first indication pursued (54.9 and 42.4%, respectively, for second and third indications if the first indication is a success, but 2.5 and 1.8%, respectively, if the first indication is a failure).