Diethylhomospermine is the polyamine analogue. It suppressed the activity of the major biosynthetic enzymes, ornithine decarboxylase and S-adenosylmethionine decarboxylase in human bladder cancer cell lines. Diethylhomospermine given as the subcutaneous injection is overall well tolerated at lower doses, but significant toxicities were observed at the 37.5mg/m2/day dose level. Maximal tolerated dose was established at 25 mg/m2/day but further investigation with this study drug is not recommended secondary to the potential for neurotoxicities and hepatic damage as a result of cumulative doses. Diethylhomospermine had been in phase II clinical trials for the treatment of AIDS-related chronic diarrhea. However, this research has been discontinued.

Buparlisib (NVP-BKM12), a dimorpholino pyrimidine derivative, is a selective pan class I phosphatidylinositol-3 kinase (PI3K) inhibitor for treating cancer. It penetrates the blood-brain barrier and has a potential as a glioma treatment. NVP-BKM120 inhibits PI3K activity by binding to the ATP binding cleft of this enzymes and was tested against class I PI3K and other kinases using an ATP depletion (Kinase-Glo) assay. The compound was shown to be active against P110 α, β, γ and δ. The inhibition of the PI3K signaling pathways leads to different forms of cell death on the basis of p53 statuses. Buparlisib demonstrated its activity in human glioblastoma (GBM) cells in vitro and in vivo and is in clinical trials for solid tumors including GBM.

E-7820 is a novel angiogenesis inhibitor. It inhibited in vitro proliferation and tube formation of human umbilical vascular endothelial cell (HUVEC). E-7820 decreased integrin alpha 2, 3, 5, and beta 1 in confluent culture of HUVEC, and integrin alpha 2 was initially suppressed in mRNA level, followed by decrement of integrins alpha 3, 5, and beta 1. Up-regulation of integrin alpha2 by phorbol 12-myristate 13-acetate abrogated the inhibitory effect of E7820 on tube formation within type I collagen gel, whereas addition of antibody against integrin alpha2 canceled the phorbol 12-myristate 13-acetate effect. This finding may provide the basis for a new approach to antiangiogenic therapy through the suppression of integrin alpha2 on endothelium. E-7820 showed a broad-spectrum antitumor effect in mice through inhibition of angiogenesis and indicate that the decrease of integrin alpha2 on platelets might serve as a biological marker for the antitumor efficacy of E-7820. Combining E-7820 and chemotherapeutic agents to block the integrin α2β1/PI3K/AKT/Snail signaling pathway revealed dramatically enhanced tumor suppression and provided an innovative approach for clinical colorectal cancer treatment.

Cenisertib (also known as R763) is water-soluble, synthetic small molecule aurora kinase inhibitor with potential antineoplastic activity. Cenisertib is a potent adenine triphosphate-competitive inhibitor of Aurora kinase isoforms A–C, disrupting mitotic spindle activity, blocking cell separation, and leading to polyploidy and cell death. At low nanomolar concentrations, Cenisertib also inhibits other kinases involved in cell survival and proliferation including FLT3, BCR-ABL1, and BCR-ABL1 with T315I mutation. It also inhibits JAK2 kinase, but at higher concentrations. Preclinically, Cenisertib has demonstrated potent antitumor activity as a single agent and in combination treatment in leukemia cell lines, freshly isolated leukemia cells, and leukemia xenograft models. Toxicities appear to be related mainly to the gastrointestinal and hematopoietic systems. In animal models, activity and toxicity depend not only on dose but also on the schedule of administration.

Sparsomycin is a model protein synthesis inhibitor that blocks peptide bond formation by binding to the large ribosome subunit. It is a unique dipeptidyl alcohol, consisting of a uracil acrylic acid moiety and a monooxo-dithioacetal group. Sparsomycin is a cytotoxic drug exhibiting a broad spectrum of in vitro activity against murine tumors and many tumor cell lines. It also appears to be a potent stimulator of the antitumor activity of cisplatin against L1210 leukemia in vivo. However, because of its toxicity, the antitumor activity of sparsomycin on murine tumors in vivo has been disappointing. Sparsomycin has shown cytostatic activity in a number of in vivo tumor systems, therefore, it was introduced in 1964 in a clinical Phase I study. Two of the five patients of this study developed an ocular toxicity, probably caused by sparsomycin, and so this Phase I study was stopped prematurely.

Swainsonine is an indolizidine alkaloid found in Australian Swainsona canescens, North American plants of the genera Astragalus and Oxytropis and also in the fungus Rhizoctonia leguminocola. It is competitive inhibitor of Golgi alpha-mannosidase II and lysosomal alpha-mannosidases. This compound has been reported to be a potent antiproliferative and immunomodulatory agent. However, no evidence of anti-tumor activity of swainsonine was seen in phase II clinical trial, in patients with locally advanced or metastatic renal cell carcinoma. Adverse events such as fatigue, nausea and diarrhea were common but generally mild. Swainsonine is locoweed toxin. Locoweed poisoning is seen throughout the world and annually costs the livestock industry millions of dollars. Swainsonine inhibits lysosomal alpha-mannosidase and Golgi mannosidase II. Poisoned animals are lethargic, anorexic, emaciated, and have neurologic signs that range from subtle apprehension to seizures.

HDAC-IN-2 (also known as citarinostat or ACY-241) was developed as a selective histone deacetylase (HDAC) 6 inhibitor with potential antineoplastic activity. Inhibition of HDAC leads to the inhibition of tumor oncogene transcription, and the selective transcription of tumor suppressor genes, which inhibit tumor cell division and induce tumor cell apoptosis. HDAC-IN-2 participates in phase 1b clinical trial in patients with multiple myeloma to determine the maximum tolerated dose (MTD) and evaluate the safety and preliminary antitumor activity. Besides, HDAC-IN-2 in combination with paclitaxel participates in phase Ib in patients with advanced solid tumors. In addition, HDAC-IN-2 in combination with nivolumab participates in phase I in patients with unresectable non-small cell lung cancer to determine the safety, tolerability, dose-limiting toxicities (DLTs), and maximum tolerated dose (MTD) of the drug.

Plomestane is an enzyme-activated aromatase inhibitor. Plomestane have demonstrated their ability to irreversibly inhibit estrogen biosynthesis in human placental microsomes. Plomestane have a dose-dependent effect on the metabolism of androstenedione in vitro in human breast tissues. It is selective inhibitors of aromatization in human breast tissues and may provide a mechanism for controlling estrogen responsive processes. Prolonged administration of plomestane to rats bearing dimethylbenzanthracene-induced mammary tumors resulted in significant regression of hormone-responsive tumors within several days. In animal models, the effects of plomestane on both regression of existing tumors and the appearance of new tumors were reversed by co-administration of estradiol. Thus, plomestane impairs estrogen-dependent mammary tumor growth, resulting in cessation of new growth and regression of responsive tumors.

Mitolactol is a synthetic derivative of hexitol with antineoplastic and radiosensitizing properties. Mitolactol alkylates DNA via actual or derived epoxide groups, resulting in inhibition of DNA and RNA synthesis.

Tanomastat (previously known as BAY 12-9566) is an inhibitor of angiogenesis and a biphenyl matrix metalloprotease (MMP). The drug was selective towards MMPs 2,3, and 9 and no activity against MMP1. Tanomastat was developed for the treatment of cancer and arthritis. Tanomastat participated in phase III clinical trials as maintenance therapy in patients with advanced ovarian cancer, and in patients with pancreatic, lung cancers. However, all studied were discontinued after the recommendation of the independent data safety monitoring board.