Briciclib (also known as ON-013105 and ON-014185) has the potential of targeting and inhibition of eukaryotic translation initiation factor 4E (eIF4E) for solid cancers. eIF4E is a proto-oncogene that promotes translation of several genes essential for cellular proliferation (cyclin D1, c-Myc, mTOR), survival (Akt), angiogenesis (VEGF), and metastasis (MMP9). Overexpression of eIF4E has been observed in almost all major groups of cancers and has been shown to induce increased expression of cyclin D1 and c-Myc). An intravenous formulation of briciclib was being investigated in the Phase 1 clinical trial. The purpose of the study was to determine the highest dose of briciclib that could be given safely in patients with relapsed/refractory Lymphoma or B-cell Acute Lymphocytic Leukemia (Philadelphia chromosome negative). However, this study was terminated because of the lack of available clinical drug supply. In addition, briciclib was also involved in phase I clinical trials with advanced cancer and solid tumors, to determine the highest dose that can be safely given.

Mericitabine is a specific inhibitor of hepatitis C virus (HCV) replication that target NS5B polymerase. Mericitabine, a prodrug, is hydrolyzed in vivo to produce PSI-6130. It had been studied in phase II clinical trials for the treatment of chronic hepatitis C. However, while it showed a good safety profile in clinical trials, it was not sufficiently effective to be used as a standalone agent.

Efatutazone (CS-7017 or RS-5444) is a peroxisome proliferator-activated receptor gamma (PPAR-gamma) agonist with antineoplastic properties. Mediated through activation of PPAR-gamma, this agent is capable of inducing cell differentiation and apoptosis, thereby leading to a reduction in cellular proliferation. Efatutazone was in clinical trials for the treatment of solid tumors however; its development has been discontinued.

Silmitasertib (CX-4945) is a potent and selective orally bioavailable small molecule inhibitor of Casein kinase II (CK2). The antiproliferative activity of CX-4945 against cancer cells correlated with expression levels of the CK2α catalytic subunit. CX-4945 caused cell-cycle arrest and selectively induced apoptosis in cancer cells relative to normal cells. When administered orally in murine xenograft models, CX-4945 was well tolerated and demonstrated robust antitumor activity. Senhwa Biosciences is developing silmitasertib for the treatment of cholangiocarcinoma, other solid tumours, Castleman's disease (giant lymph node hyperplasia) and multiple myeloma. The compound was originally developed by Cylene Pharmaceuticals. Phase Ib/II development is underway in the US and South Korea for the treatment of cholangiocarcinoma, and development in the remaining indications is at the phase I stage. As at July 2016, no recent reports of development had been identified for phase-I development in Giant-lymph-node-hyperplasia in USA (PO, Capsule), phase-I development in Multiple-myeloma in USA (PO, Capsule), phase-I development in Solid-tumours (Late-stage disease) in USA (PO, Capsule).

Asulacrine, also known as CI-921, an inhibitor of topoisomerase II, participated in clinical trials phase II for the treatment of cancer. In spite of the positive and promising results, this drug showed the toxicity, phlebitis that blocks its implementation in the future.

Piritrexim is a synthetic antifolate agent with antiparasitic, antipsoriatic and antitumor properties. Piritrexim inhibits the enzyme dihydrofolate reductase, thereby disrupting folate metabolism and DNA synthesis and cell division. A theoretical advantage of piritrexim over trimetrexate is a lack of any known effects on histamine metabolism, which may lower the risk of hypersensitivity reactions. Piritrexim is a nonclassical antifolate for antitumor and parasitic chemotherapy that passively diffuses into cells and hence do not have to depend on folylpoly-gamma-glutamate synthetase or the reduced folate carrier. Because piritrexim is not a substrate for polyglutamation, the drug is not selectively retained within cells for prolonged periods. Piritrexim has a reliably high oral bioavailability of about 75%, which has led to its development as an oral lipophilic antifolate. Most commonly, it has been administered in oral daily doses of 75 to 150 mg bid or tid every 5 days, with cycles repeated every 3 weeks. Oral absorption is rapid, with peak plasma levels appearing at 1.5 hours after ingestion. Elimination occurs primarily via hepatic metabolism of the drug to active metabolites, and the terminal half-life of the parent compound is about 1.5 to 4.5 hours. Single-agent oral piritrexim has clinical activity in melanoma, urothelial cancers, and head and neck cancers. Tolerable combinations of piritrexim with cisplatin, fluorouracil, and leucovorin have been tested, with promising results achieved in head and neck cancer. An interesting attempt to alternate piritrexim with methotrexate did not have any greater activity than methotrexate alone.

Onalespib (AT13387; (2,4-dihydroxy-5-isopropyl-phenyl)-[5-(4-methyl-piperazin-1-ylmethyl)-1,3-dihydro-isoindol-2-yl] methanone, l-lactic acid salt), is wholly owned by Astex, a novel, high-affinity HSP90 inhibitor, which is currently being clinically tested, has shown activity against a wide array of tumor cell lines, including lung cancer cell lines. As a targeted inhibitor of Hsp90, onalespib has the potential to control the proliferation of multiple solid tumors and hematological malignancies where uncontrolled cell growth is dependent on the interaction between Hsp90 and its client proteins. Astex is pursuing an approach based on the observation that addition of onalespib to a molecularly targeted agent may delay the emergence of resistance to the agent, and hence prolong the window of therapeutic benefit. Onalespib is currently being evaluated via a CRADA with the National Cancer Institute (NCI) in various tumor types, and in a Phase 1/2 clinical study in combination with AT7519, Astex CDK inhibitor.

The dihydrochloride salt of nolatrexed, a water-soluble lipophilic quinazoline folate analog with antineoplastic activity. Nolatrexed occupies the folate binding site of thymidylate synthase, resulting in inhibition of thymidylate synthase activity and thymine nucleotide synthesis with subsequent inhibition of DNA replication, DNA damage, S-phase cell cycle arrest, and caspase-dependent apoptosis. This agent also exhibits radiosensitizing activity. Orphan designation of nolatrexed was granted in the Unites States of America for treatment of hepatocellular carcinoma.

The BET-bromodomain inhibitor OTX015 (MK-8628) was initially developed by Mitsubishi Tanabe Pharma Corporation, but then was licensed by OncoEthix, privately held biotechnology company. OTX015 is a selective bromodomains: BRD2, BRD3, and BRD4 inhibitor and inhibits their binding to AcH4. Bromodomains have an important role in the targeting of chromatin-modifying enzymes to specific sites, including methyltransferases, HATs and transcription factors and regulate diverse biological processes from cell proliferation and differentiation to energy homeostasis and neurological processes. OTX015 has potent antiproliferative activity accompanied by c-MYC down-regulation in several tumor types, and has demonstrated synergism with the mTOR inhibitor everolimus in different models. Oral administration of OTX-015 markedly inhibited tumor growth and reduced tumor volume. OTX015 is currently in Phase 1b studies for the treatment of hematological malignancies and advanced solid tumors such as Triple Negative Breast Cancer, Non-small Cell Lung Cancer, Castrate-resistant Prostate Cancer (CRPC) and Pancreatic Ductal Adenocarcinoma. In addition, OTX015 was in phase II for the treatment of Glioblastoma Multiforme, but there were not detected clinical activity of the drug in the treatment populations and trial was closed.