Phase I Multicenter, Open-label, Clinical and Pharmacokinetic Study of PM01183 in Combination with Fixed Doxorubicin 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 doxorubicin, to characterize the safety profile and feasibility of this combination, to characterize the pharmacokinetics (PK) of this combination, to obtain preliminary information on the clinical antitumor activity,to explore the feasibility, safety and efficacy of a potential improvable dose of this combination in selected tumor types [i.e. small cell lung cancer (SCLC) and endometrial cáncer] and to evaluate the pharmacogenomics (PGx) in tumor samples of patients exposed to PM01183 and doxorubicin at the RD in order to assess potential markers of response and/or resistance.