Bryostatin 1 is a macrocyclic lactone which can be isolated from the marine bryozoan, Bugula neritina. The effects of bryostatin 1 are attributed to its ability to selectively modulate the activity of two of the three subgroups of protein kinase C (PKC) isozymes. PKC isozymes are divided into three subgroups which differ in their molecular structures and co-factor requirements: classical PKC (cPKC), novel PKC (nPKC), and atypical PKC (aPKC). Bryostatin-1 modulates nPKC activity independent of a Ca2+ signaling. It activates cPKC only when associated with Ca2+ signaling. And, aPKC activity is not sensitive to bryostatin-1 administration. Ca2+ signals play an important role in synaptic transmission and information processing which creates a biological environment where Bryostatin-1 possesses a unique action profile. Bryostatin-1 will not affect cPKC activity in neurons which are not functioning as an active part of the signaling processing circuit with significant Ca2+influx and intracellular Ca2+ release. Bryostatin 1 is in phase II clinical trials for investigation as an anticancer agent; specifically for treatment of metastatic or recurrent head and neck cancer, ovarian epithelial cancer that has not responded to previous chemotherapy, and myelodysplastic syndrome. Bryostatin 1 has also generated interest as an investigational compound for the treatment of Alzheimer's disease.

MKC-1 is an orally available cell cycle inhibitor with downstream targets that include tubulin and the importin-β family. MKC-1 has shown broad antitumor activity in preclinical models. MKC-1 and its metabolites inhibit tubulin polymerization, blocking the formation of the mitotic spindle, which may result in cell cycle arrest at the G2/M phase and apoptosis. In addition, this agent has been shown to inhibit the activities of the oncogenic kinase Akt, the mTOR pathway, and importin-beta, a protein essential to the transport of other proteins from the cytosol into the nucleus. MKC-1 had been in phase II clinical trials for the treatment of ovarian cancer, endometrial cancer, pancreatic cancer and breast cancer. This compound was originally discovered by Roche, then licensed to EntreMed (now CASI Pharmaceuticals) the exclusive worldwide rights to develop and commercialize. However, no recent development has been reported.

7-Hydroxystaurosporine (UCN-01) is a protein kinase inhibitor which is under development as an anti-cancer agent in the USA and Japan. Although UCN-01 was originally isolated from the culture broth of Streptomyces sp. as a protein kinase C-selective inhibitor, its ultimate target as an anti-cancer agent remains elusive. As a single agent, UCN-01 exhibits two key biochemical effects, namely accumulation of cells in the G1 phase of the cell cycle and induction of apoptosis. Both these effects may be important for its anti-cancer activity. As a modulator, 7-Hydroxystaurosporine enhances the cytotoxicity of other anti-cancer drugs such as DNA-damaging agents and anti-metabolite drugs through putative abrogation of G2 and/or S phase accumulation induced by these anti-cancer agents. 7-Hydroxystaurosporine had been in phase II clinical trials Life Sciences for the treatment of T-cell lymphoma, malignant melanoma, pancreatic cancer, small cell lung cancer, acute myeloid leukemia, ovarian cancer. However, the research was either discontinued or suspended.

Elesclomol (also known as STA-4783), originally identified in a cell-based phenotypic screen for pro-apoptotic activity, is a novel small-molecule that potently induces apoptosis of cancer cells through the rapid generation of reactive oxygen species (ROS) and the induction of unmanageable levels of oxidative stress. Elesclomol exhibits antitumor activity against a broad spectrum of types of cancer cell in human tumour xenograft models due to its excessive ROS production and elevated levels of oxidative stress leading to the death of cancer cells. Elesclomol is currently being studied as novel cancer therapeutic, in which it has demonstrated the ability to prolong progression-free survival in study subjects. Elesclomol induces oxidative stress by provoking a buildup of reactive oxygen species within cancer cells. Elesclomol requires a redox-active metal ion to function; the Cu(II) complex is 34 times more potent than the Ni(II) complex and 1040-fold more potent than the Pt(II) complex. Elesclomol is an HSP-90 Inhibitor with pro-apoptotic and potential antineoplastic activities. Elesclomol induces oxidative stress and triggers mitochondrial-induced apoptosis in cancer cells. Elesclomol is being developed by Synta Pharmaceuticals and GlaxoSmithKline as a chemotherapy adjuvant and has received both fast track and orphan drug status from the U.S. Food and Drug Administration for the treatment of metastatic melanoma. Synta Pharmaceuticals announced on February 26, 2009, the suspension of all clinical trials involving Elesclomol due to safety concerns. In March 2010, Synta announced that the FDA had approved resuming clinical development of elesclomol, and that they expected to initiate one or more clinical trials for elesclomol in the second half of the year. In a small, randomized phase II study, elesclomol was shown to significantly increase progression-free survival in people with metastatic melanoma when given in addition to paclitaxel (Taxol).

AZD1775 selectively targets and inhibits WEE1, a tyrosine kinase that phosphorylates cyclin-dependent kinase 1 (CDK1, CDC2) to inactivate the CDC2/cyclin B complex. Inhibition of WEE1 activity prevents the phosphorylation of CDC2 and impairs the G2 DNA damage checkpoint. This may lead to apoptosis upon treatment with DNA damaging chemotherapeutic agents. Current ongoing trials of AZD1775 include monotherapy and combination therapy with certain DNA damaging agents in solid tumors, ovarian tumors, gynaecological cancer, non-small cell lung cancer. AZD1775 is genotoxic, which is considered to be a result of its mechanism of action. Common serious adverse events (with chemotherapy) include: febrile neutropenia, neutropenia, thrombocytopenia.

Rubitecan [Orathecin™] is a topoisomerase I inhibitor extracted from the bark and leaves of the Camptotheca acuminata tree, which is native to China. Rubitecan is an oral compound being developed for the treatment of pancreatic cancer and other solid tumours by SuperGen. Rubitecan binds to and inhibits the enzyme topoisomerase I and induces protein-linked DNA single-strand breaks, thereby blocking DNA and RNA synthesis in dividing cells; this agent also prevents repair of reversible single-strand DNA breaks.

Idronoxil (Phenoxodiol) is a synthetic flavonoid derivative developed by MEI Pharma for cancer treatment. Idronoxil inhibits proliferation of many cancer cell lines and induces apoptosis by disrupting FLICE-inhibitory protein, FLIP, expression and by caspase-dependent and -independent degradation of the X-linked inhibitor of apoptosis, XIAP. In addition, Idronoxil sensitizes drug-resistant tumour cells to anticancer drugs including paclitaxel, carboplatin, and gemcitabine. The antiproliferative effects of Idronoxil are associated with inhibition of plasma membrane electron transport in tumour cell lines and primary immune cells. Idronoxil displays anti-cancer activity against all forms of cancer tested in vitro and in vivo to date, using cells representative of all major forms of cancer. While having a modest ability to kill cancer cells(IC50 range between about 1-5 uM), preclinical studies point to its optimal use being to sensitize cancer cells to the toxic effects of standard therapies (chemotherapy and radiotherapy). The rationale is that a sub-lethal inhibitory effect on sphingosine kinase activity reduces the ability of the cancer cell to operate drug-resistance mechanisms and to effect repair of drug- or radiation-induced damage to DNA. In the case of cytotoxic drugs such as cisplatin, carboplatin, paclitaxel, Doxorubicin, and gemcitabine, Idronoxil is an exquisite sensitizer, increasing the cytotoxic potential of those agents by between 103 -105 times, in the process restoring sensitivity to cancer cells highly refractory to those agents.

Pyrazofurin (PF) (3,β-D-ribofuranosyl, 4-hydroxyprazole-5-carboxamide) is a C-nucleoside antibiotic, one in which the ribose joins the base-ring carbon instead of a base-ring nitrogen. Pyrazofurin potently inhibits orotidine 5'-monophosphate (OMP) decarboxylase, thereby interfering with de novo synthesis of uridine nucleotides and resulting in cytotoxicity. This agent also causes a rapid depletion of the pyrimidine deoxynucleotide pool, thereby inhibiting DNA synthesis and cell replication. PF was isolated from fermentation filtrate of Strepomyces candidus. This compound was initially found to have inhibitory activity against the vaccinia, herpes simplex, rhino and measles viruses in vitro and the vaccinia virus in vivo. More recently the antiviral spectrum has been extended to include the polio, Coxsackie, Sindbis and vesicular stomatitis viruses.

3,3',5,5'-Tetraiodothyroacetic acid (Tetrac) is a deaminated analog of L-thyroxine (T4) that blocks the proangiogenesis actions of T4 and 3, 5, 3’-triiodo-L-thyronine as well as other growth factors at the cell surface receptor for thyroid hormone on integrin αvβ3. 3,3',5,5'-Tetraiodothyroacetic acid blocks the transcriptional activities directed by L-thyroxine (T4) and 3,5,3’-triiodo-L-thyronine (T3) at αvβ3, but, independently of T4 and T3, 3,3',5,5'-Tetraiodothyroacetic acid modulates transcription of cancer cell genes that are important to cell survival pathways, control of the cell cycle, angiogenesis (VEGFA, FGF), apoptosis, cell export of chemotherapeutic agents, and repair of double-strand DNA breaks. 3,3',5,5'-Tetraiodothyroacetic acid was found to perturb the angiogenesis process stimulated by VEGF (Vascular Endothelial Growth Factor) or FGF (Fibroblast Growth Factor) without influencing the preexisting blood vessels.

Ergosterol endoperoxide is a derivative of ergosterol. It has been isolated from a variety of fungi, yeast, lichens and sponges. Ergosterol endoperoxide has been shown to inhibit the growth of some cancer cells and to induce apoptosis of HL60 human leukemia cells. Ergosterol endoperoxide also decreases lipid peroxidation of rat liver microsomes and suppresses the proliferation of mouse and human lymphocytes stimulated with mitogens. It has been reported as having immunosuppressive, antiplasmodial, antimycobacterial, antiviral, anti-inflammatory and antitumoural properties. The interaction of Trypanosoma cruzi with ergosterol peroxide in vitro resulted in a strong lytic activity possibly due to the disruption of the parasite membrane.