8-Chloroadenosine-3',5'-cyclic-monophosphate (8-Cl-cAMP), an analog of c-AMP, is a novel antineoplastic agent. It has been shown to be effective against different human cancer cell lines modulating the cellular signal transduction pathway, thereby causing growth inhibition, cell differentiation, and apoptosis. 8-Cl-cAMP preferentially binds to the R2 subunit of protein kinase A (PKA) and induces rapid R2 up-regulation and eventual R1 subunit down-regulation. It has potent inhibitory effects on a wide variety of human cancer cell lines, with an IC50 ranging from 0.1 to 20 uM. The IC50 falls with the length of drug exposure. It can suppress c-myc and c-ras proto-oncogenes in vitro and in vivo. It was shown that 8-Cl-cAMP induces cell growth inhibition through AMP-activated protein kinase (AMPK) activation with p38 MAPK acting downstream of AMPK in this signaling pathway. 8-Cl-cAMP induced apoptosis, apparently through activation of the p38 MAPK pathway by inducing progressive phosphorylation of the p38 mitogen-activated protein kinase (MAPK), via activation of AMPK by its metabolite 8-Cl-adenosine. 8-Cl-cAMP does not significantly inhibit the growth of NIH 3T3 cells, rat kidney fibroblasts, mammary epithelial cells, or peripheral blood lymphocytes, nor does it inhibit the growth of parental cells whose progeny have been transformed. Such selectivity makes it an attractive candidate for cancer therapy suggesting that it should not cause the toxicity of conventional cytotoxic agents but should inhibit tumor growth. 8-Cl-cAMP has been evaluated in phase I/II clinical trials.

Pinometostat, also known as EPZ-5676, is a small molecule inhibitor of histone methyltransferase with potential antineoplastic activity. Upon intravenous administration, EPZ-5676 specifically blocks the activity of the histone lysine-methyltransferase DOT1L, thereby inhibiting the methylation of nucleosomal histone H3 on lysine 79 (H3K79) that is bound to the mixed lineage leukemia (MLL) fusion protein which targets genes and blocks the expression of leukemogenic genes. Epizyme is developing pinometostat, a small molecule inhibitor of DOT1L, for the treatment of patients with MLL-r, a genetically defined acute leukemia. Epizyme is conducting a phase 1 clinical trial in pediatric patients. Epizyme is evaluating preclinical combinations of pinometostat with other anti-cancer agents in MLL-r leukemia. Pinometostat is being developed in collaboration with Celgene. Epizyme retains all U.S. rights to pinometostat and has granted Celgene an exclusive license to pinometostat outside of the U.S.

Puromycin dihydrochloride belongs to the aminonucleoside family of antibiotics and is isolated from Streptomyces alboniger. Since the partial structure of this antibiotic showed it to be a purine derivative, puromycin was assigned as its generic name. Puromycin is a broad spectrum antibiotic and antibacterial agent. It is active against Gram-positive microorganisms, less active against acid-fast bacilli, and weakly active against Gram-negative microorganisms. It acts very quickly and can kill 99% of the cells within 2 days. It also exhibits antitumor activity in studies on brain tumor cells. Puromycin is a protein synthesis inhibitor that causes premature chain termination by acting as an analog of the 3’-terminal end of aminoacyl-tRNA. It has been used to study transcriptional regulatory mechanisms that control the sequential and coordinate expression of genes during cell differentiation.

Dexniguldipine (B8509-035, (-)-(R)-niguldipine) is a new dihydropyridine derivative, that exerts selective antiproliferative activity in a variety of tumor models and, in addition, has a high potency in overcoming multidrug resistance. Dexniguldipine is ( - )-(R)-enantiomer of niguldipine, of which the ( )-(S)-enantiomer shows pronounced cardiovascular hypotensive activity due to its high affinity for the voltage-dependent Ca2 channel. As compared with the (S)-enantiomer, the (R)-enantiomer has a 40-fold lower affinity for the Ca 2 channel and, accordingly, only minimal hypotensive activity in animal pharmacology models. Dexniguldipine have shown antiproliferative activity in several tumor cell lines, but the concentrations necessary to inhibit growth have varied by several orders of magnitude between cell lines. Initial results of preclinical investigations for the evaluation of the mechanism of its antiproliferative activity demonstrate that dexniguldipine interferes with intracellular signal transduction by affecting phosphoinositol pathways, protein kinase C expression, and intracellular Ca 2 metabolism. In a series of human tumor xenografts in vitro, dexniguldipine demonstrated selective antiproliferative activity against several tumor types, e.g., melanoma and renal-cell carcinoma. Striking results were obtained in a hamster model, in which neuroendocrine lung tumors could be completely eradicated by 20 weeks of oral treatment with 32.5mg/kg dexniguldipine, whereas Clara-cell-type lung tumors were not affected. In in vitro studies, dexniguldipine has been found to bind to P-glycoprotein (P-gp) and to enhance the cytotoxicity of chemotherapeutic agents such as doxorubicin and etoposide in several cell lines The synergistic effect may well be associated with the reversal of multidrug resistance (MDR) related to the activity of P-gp. In the clinical therapy of cancer, resistance to many cytostatic drugs is a major cause of treatment failure. However, the high potency of dexniguldipine (about 10-fold as compared with that of verapamil in vitro) and its low cardiovascular activity provide the opportunity to achieve blood or tumor concentrations that might be high enough to overcome Mdr 1 resistance in patients without producing dose-limiting cardiovascular effects.

Puromycin dihydrochloride belongs to the aminonucleoside family of antibiotics and is isolated from Streptomyces alboniger. Since the partial structure of this antibiotic showed it to be a purine derivative, puromycin was assigned as its generic name. Puromycin is a broad spectrum antibiotic and antibacterial agent. It is active against Gram-positive microorganisms, less active against acid-fast bacilli, and weakly active against Gram-negative microorganisms. It acts very quickly and can kill 99% of the cells within 2 days. It also exhibits antitumor activity in studies on brain tumor cells. Puromycin is a protein synthesis inhibitor that causes premature chain termination by acting as an analog of the 3’-terminal end of aminoacyl-tRNA. It has been used to study transcriptional regulatory mechanisms that control the sequential and coordinate expression of genes during cell differentiation.