Aclarubicin: An anthracycline produced by Streptomyces galilaeus. It has potent antineoplastic activity.Topoisomerase II Inhibitors: Compounds that inhibit the activity of DNA TOPOISOMERASE II. Included in this category are a variety of ANTINEOPLASTIC AGENTS which target the eukaryotic form of topoisomerase II and ANTIBACTERIAL AGENTS which target the prokaryotic form of topoisomerase II.Amsacrine: An aminoacridine derivative that intercalates into DNA and is used as an antineoplastic agent.Drug Antagonism: Phenomena and pharmaceutics of compounds that inhibit the function of agonists (DRUG AGONISM) and inverse agonists (DRUG INVERSE AGONISM) for a specific receptor. On their own, antagonists produce no effect by themselves to a receptor, and are said to have neither intrinsic activity nor efficacy.Daunorubicin: A very toxic anthracycline aminoglycoside antineoplastic isolated from Streptomyces peucetius and others, used in treatment of LEUKEMIA and other NEOPLASMS.Antibiotics, Antineoplastic: Chemical substances, produced by microorganisms, inhibiting or preventing the proliferation of neoplasms.DNA Topoisomerases, Type II: DNA TOPOISOMERASES that catalyze ATP-dependent breakage of both strands of DNA, passage of the unbroken strands through the breaks, and rejoining of the broken strands. These enzymes bring about relaxation of the supercoiled DNA and resolution of a knotted circular DNA duplex.Carcinoma, Small Cell: An anaplastic, highly malignant, and usually bronchogenic carcinoma composed of small ovoid cells with scanty neoplasm. It is characterized by a dominant, deeply basophilic nucleus, and absent or indistinct nucleoli. (From Stedman, 25th ed; Holland et al., Cancer Medicine, 3d ed, p1286-7)Carcinoma, Ehrlich Tumor: A transplantable, poorly differentiated malignant tumor which appeared originally as a spontaneous breast carcinoma in a mouse. It grows in both solid and ascitic forms.