Phase I multicenter, open-label, clinical and pharmacokinetic study of PM01183 in combination with gemcitabine in non-heavily pretreated patients with selected advanced solid tumors to determine the maximum tolerated dose (MTD) and the recommended dose (RD) of PM01183 in combination with gemcitabine, to characterize the safety profile and feasibility of this combination in patients with selected advanced solid tumors, to characterize the pharmacokinetics (PK), to obtain preliminary information on the clinical antitumor activity in non-heavily pretreated selected solid tumor patients and to evaluate the pharmacogenomics (PGx) in tumor samples of patients exposed, in order to assess potential markers of response and/or resistance.