Valrubicin is a semisynthetic analog of the anthracycline doxorubicin, and is administered by infusion directly into the bladder. Valrubicin is an anthracycline that affects a variety of inter-related biological functions, most of which involve nucleic acid metabolism. It readily penetrates into cells, where after DNA intercalation, it inhibits the incorporation of nucleosides into nucleic acids, causes extensive chromosomal damage, and arrests cell cycle in G2. Although valrubicin does not bind strongly to DNA, a principal mechanism of its action, mediated by valrubicin metabolites, is interference with the normal DNA breaking-resealing action of DNA topoisomerase II. Valrubicin is FDA approved drug, sold under the trade name Valstar.

Ilmofosine (1-hexadecylthio; 2-methoxyethyl-racglycero-3-phosphocholine) is a synthetic 1-S-thioether alkyl lysophospholipid derivative with potential antineoplastic activity. In extensive preclinical evaluation against tumor cell lines and in the human tumor colony-forming assay, Ilmofosine was cytotoxic against both leukemias and solid tumors. Ilmofosine was effective against many tumor types, including ovary, non-small cell lung, kidney, and melanoma. Ilmofosine exhibited competitive inhibition of protein kinase C activity with respect to phosphatidyl-serine and inhibited the enzyme activated by diolein.

Edelfosine is a synthetic alkyl-lysophospholipid, a potent immunomodulator and an effective inhibitor of tumor cell proliferation. The cytotoxic effect of edelfosine has been evaluated in a large variety of both tumor (leukemic and solid) and normal cell types, showing a high degree of selectivity towards tumor cells. Like all alkyl-lysophospholipids, Edelfosine incorporates into the cell membrane and does not target the DNA. In many tumor cells, Edelfosine causes selective apoptosis, sparing healthy cells. Edelfosine can activate the Fas/CD95cell death receptor, can inhibit the MAPK/ERK mitogenic pathway and the Akt/protein kinase B (PKB) survival pathway. Edelfosine apoptosis-inducing abilities were studied with several types of cancer, among them multiple myeloma and non-small and small cell lung carcinoma cell lines. In vivo activity against human solid tumors in mice was shown against malignant gynecological tumor cells, like ovarian cancer, and against breast cancer. In vivo biodistribution studies demonstrated a “considerably higher” accumulation of Edelfosine in tumor cells than in other analyzed organs. Several clinical trials were conducted. Among them, a phase I trials with solid tumors or leukemias and phase II with non-small-cell lung carcinomas (NSCLC). In Phase II clinical trial for use of Edelfosine in treating leukemia with bone marrow transplants, it was found to be safe and 'possibly effective'. A phase II trial for the treatment of brain cancers was also reported. It showed encouraging results in stopping the growth of the tumor and a considerable improvement in the “quality of life” of the patients. A phase II trial on the effect of Edelfosine on advanced non-small-cell bronchogenic carcinoma had a “remarkable” “high proportion of patients with stationary tumor status” as result, stable disease after initial progression in 50% of the patients.

Phorbol 12-myristate 13-acetate (PMA) also commonly known as 12-O-Tetradecanoylphorbol-13-acetate (TPA) is a phorbol ester that is commonly used to activate phospholipid-dependent protein kinase (protein kinase C). PMA/ TPA possesses potential antineoplastic effects and was studied in phase II clinical trials together with dexamethasone in patients with relapsed or refractory acute myeloid leukemia. In addition, PMA/ TPA participated in phase I trial for treating patients with hematologic cancer or bone marrow disorder that has not responded to previous treatment. Nevertheless, both clinical trials were terminated. Besides, PMA/ TPA was studied in patients with solid tumors, which had depressed white blood cell and neutrophil counts because of prior treatment with cytotoxic cancer chemotherapeutic drugs. It was shown, that the drug increased the low white blood cell and neutrophil counts toward the normal range.

Gossypol is a substance that is found in the cotton plant. It is removed from the seeds and used for medicine. Gossypol is effective as a nonhormonal male contraceptive; however, it has been documented to have irreversible effects on male fertility. Gossypol is reported to exhibit antioxidant, anticancer, antivirus, antiparasitic, and antimicrobial properties and lower plasma cholesterol. Nausea, emesis, anorexia, diarrhea, altered taste sensation, small intestine obstruction, and fatigue have been recorded in clinical trials as adverse reactions. Large amounts of gossypol can decrease potassium levels in the body. Low potassium levels can increase the side effects of digoxin.

K-252a, a metabolite isolated from the culture broth of Nocardiopsis sp. K-252a, was found to exhibit an extremely potent inhibitory activity on protein kinase C. The IC50 value was 32.9 nM. K252a is a potent inhibitor of various protein kinases including Protein kinase A, Protein kinase C and Protein kinase G. It acts by competition with the ATP binding site with Ki values of 18-25 nM. K252a also acts as a specific and potent inhibitor (IC50 = 3 nM) of Trk receptors and thus selectively blocks the effects of nerve growth factor (NGF) on PC12 cells. At lower concentrations, K252a can act as a neuroprotective compound, promoting survival of primary neuronal cultures. This alkaloid induces apoptosis and cell cycle arrest by inhibiting Cdc2 and Cdc25.4 Recently, K252a was found to improve psoriasis in a SCID mouse-human skin model and to suppress referred mechanical hypersensitivity and neuropeptide up-regulation associated with acute pancreatitis.

Staurosporine is an alkaloid isolated from the culture broth of Streptomyces staurosporesa. It exerts antimicrobial, hypotensive, and cytotoxic activity. The main biological activity of staurosporine is the inhibition of protein kinases through the prevention of ATP binding to the kinase. This is achieved through the stronger affinity of staurosporine to the ATP-binding site on the kinase. Staurosporine is a prototypical ATP-competitive kinase inhibitor in that it binds to many kinases with high affinity, though with little selectivity. It is a potent, cell permeable protein kinase C inhibitor with an IC50 of 0.7 nM. At higher concentration (1-20 nM), staurosporine also inhibits other kinases such as PKA, PKG, CAMKII and Myosin light chain kinase (MLCK). At 50-100 nM, it is a functional neurotrophin agonist, promoting neurite outgrowth in neuroblastoma, pheochromocytoma and brain primary neuronal cultures. At 0.2- 1 uM, staurosporine induces cell apoptosis. Staurosporine is also a potent GSK-3β inhibitor with a reported IC50 value of 15 nM. In research, staurosporine is used to induce apoptosis. It has been found that one way in which staurosporine induces apoptosis is by activating caspase-3. Staurosporine was discovered to have biological activities ranging from anti-fungal to anti-hypertensive. The interest in these activities resulted in a large investigative effort in chemistry and biology and the discovery of the potential for anti-cancer treatment. Staurosporine induces apoptosis by multiple pathways and that the inhibition of more than one kinase is responsible for its potent activity. Because the mechanism of action of staurosporine is distinct from traditional anticancer drugs, this may warrant further preclinical evaluations of the antitumor potential of new staurosporine derivatives either alone or in combination with death ligands or conventional chemotherapeutic drugs.

Chelerythrine is a kind of benzo[c] phenanthridine alkaloids, which is widely found in plant of Fumariaceae, Papaveraceae, Ranunculaceae and Rutaceae families. Chelerythrine is a potent and specific inhibitor of protein kinase C. In addition chelerythrine inhibits pro-survival protein Bcl(XL) thereby inducing apoptosis. It exerts antitumor properties.