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.

Gantofiban (or EMD 122 347) is an oral double prodrug of the drug, EMD 132338 and is GPIIb/IIIa antagonist. The drug participated in phase II clinical trials in Japan in patients with thrombosis. However, in May 2004, Yamanouchi, the developing company, announced that the study was discontinued. Besides gantofiban was involved in phase II trials, like a treatment option in patients with the acute coronary syndrome. However, further information is not available.

Carafiban is orally active heterocyclic peptide mimetics fibrinogen IIb/IIIa receptor antagonist with antithrombotic activity. Carafiban is a prodrug, that underwent metabolic transformation to active metabolite des-ethyl- Carafiban, that inhibited dose-dependently and reversibly human platelet aggregation. In conscious dogs, Carafiban showed a high plasma availability of the active moiety of 42±8% and a plasma half-life of 9.9 h after oral administration as measured by bioassay. Carafiban may potentially be used for chronic treatment and prophylaxis of thrombotic diseases in humans.

Canfosfamide is a modified glutathione analogue and nitrogen mustard prodrug, with potential antineoplastic activity. Canfosfamide is selectively activated by glutathione S-transferase P1-1 an enzyme that is over-expressed in many human cancers including ovarian cancer. GST P1-1-mediated cleavage leads to an active cytotoxic phosphorodiamidate alkylating metabolite that forms covalent linkages with nucleophilic centers in tumor cell DNA, which may induce a cellular stress response and cytotoxicity, and decrease tumor cell proliferation. Preclinical studies showed that canfosfamide inhibited the growth and was cytotoxic to a wide range of established cancer cell lines including those derived from ovarian cancer (OVCAR3, HEY, SK-OV-3). Canfosfamide treatment inhibited cancer cell proliferation and induced apoptosis through the activation of the cellular stress response kinase pathway. The cytotoxic activity of canfosfamide correlated with the expression of GST P1-1. Cancer cells in which GST expression levels were increased by transfection with the GST P1-1 gene, were more sensitive to the cytotoxic effects of canfosfamide than the parental cell lines Canfosfamide in combination with pegylated liposomal doxorubicin is well tolerated and active in platinum and paclitaxel refractory or resistant ovarian cancer.

Amiselimod (MT-1303) is a selective sphingosine 1-phosphate 1 (S1P1 ) receptor modulator which is currently being developed for the treatment of various autoimmune diseases. Unlike some other S1P receptor modulators, amiselimod seemed to show a favourable cardiac safety profile in preclinical, phase I and II studies. Amiselimod may be potentially useful for treatment of multiple sclerosis; inflammatory diseases; autoimmune diseases; psoriasis and inflammatory bowel diseases. Amiselimod is currently being developed by Mitsubishi Tanabe Pharma Corporation.

Sibrafiban (G-7453) is the orally administered, nonpeptide, double-prodrug of Ro 44-3888 which is a selective glycoprotein IIb/IIIa receptor antagonist. Sibrafiban is a double prodrug that undergoes bioconversion to the inactive prodrug Ro 48-3656 and to the active IIb/IIIa antagonist, Ro 44-3888, after oral administration. Sibrafiban was undergoing clinical trials for secondary prevention of cardiac events in patients stabilised after acute coronary syndromes. Sibrafiban has been shown to have comparable efficacy to aspirin in preventing recurrent ischemic events in patients suffering from acute coronary syndromes. Sibrafiban was under development by Genentech and Hoffmann-La Roche, and in phase III trials as an antithrombotic. The development of sibrafiban was discontinued in 1999 following unfavorable Phase III efficacy data.

Ezatiostat (TLK199) [γ-glutamyl-S-(benzyl)cysteinyl-R-phenyl glycine diethyl ester] is an inhibitor of Glutathione S-transferase P1–1 (GSTπ). The drug is a peptidomimetic of GSH (glutathione), esterified to enhance cellular uptake and designed to bind to the “G-site” of GSTP1–1. Independent of catalysis inhibition, TLK199 also disrupts the protein:protein interaction site(s) between GSTP1–1 and JNK1. Telik Inc was developing TLK-199 for the potential prevention of myelosuppression in blood diseases, namely myelodysplastic syndrome.