Tesevatinib (EXEL-7647 or XL647) was optimized as an inhibitor of a spectrum of growth-promoting and angiogenic receptor tyrosine kinases (RTKs) to simultaneously block tumor growth and vascularization. In particular, Tesevatinib potently inhibits the EGF/ErbB2, VEGF, and ephrin RTK families. The drug is being developed by Kadmon Corporation under licence from Symphony Evolution (Symphony Capital Partners). Kadmon is developing tesevatinib for the treatment of autosomal polycystic kidney disease and solid cancers.

Liarozole is an imidazole-containing compound that inhibits the cytochrome P-450-dependent metabolism of all-trans-retinoic acid (RA). Liarozole, a retinoic acid (RA) metabolism-blocking agent (RAMBA) in clinical development, has been granted orphan drug designation for congenital ichthyosis by the European Commission and the U.S. Food and Drug Administration. Later, based on the mixed results from a phase II/III trial of liarozole for the treatment of ichthyosis, Barrier decided to discontinue the development of liarozole. Liarozole displays antitumor activity against androgen-dependent and independent rat prostate carcinomas.A large phase III international study was completed comparing liarozole 300 mg twice daily with cyproterone acetate (CPA) 100 mg twice daily in a total of 321 patients with metastatic prostate cancer in relapse after first-line endocrine therapy. The results indicate that liarozole might be a possible treatment option for prostate cancer (PCA) following failure of first-line endocrine therapy.

Tiospirone (TSP) is an atypical antipsychotic drug. Tiaspirone appeared to be a promising antipsychotic agent as it didn`t cause extrapyramidal syndromes. It has 5HT-2 antagonistic properties as well as affinity for D2, 5HT-1a, 5HT-6 and sigma receptors. Tiospirone was in phase III clinical trials for the treatment of attention hyperactivity disorder with Mead Johnson in the USA but its development appears to have been discontinued.

Fedotozine [(1R)-1-phenyl-1-[(3,4,5-trimethoxy) benzyloxymethyl]-N,N- dimethyl-n-propylamine, (2S,3S-tartrate], derived from the arylacetamide series, is an opioid drug which acts as a selective agonist for kappa(1a)-opioid receptor. Pharmacological studies have shown that fedotozine exerts a peripheral antinociceptive action, comparable with that of other kappa-agonists. Results of Phase III trials of fedotozine against irritable bowel syndrome and dyspepsia have ultimately been disappointing and was lack of efficacy in subsequent studies.

Crenolanib is an orally active, highly selective, small molecule, next generation inhibitor of platelet-derived growth factor receptor (PDGFR) tyrosine kinase. Crenolanib, manufactured by Arog Pharmaceuticals in Dallas, is taken orally with chemotherapy. The compound is currently being evaluated for safety and efficacy in clinical trials for various types of cancer, including acute myeloid leukemia (AML), gastrointestinal stromal tumor (GIST), and glioma. Crenolanib is an orally bioavailable, selective small molecule inhibitor of type III tyrosine kinases with nanomolar potencies against platelet-derived growth factor receptors (PDGFR) (isoforms PDGFRα and PDGFRβ) and Fms-related tyrosine kinase 3 (FLT3). Besides PDGFR and FLT3, crenolanib does not inhibit any other known receptor tyrosine kinase (RTK) (e.g. VEGFR and FGFR) or any other serine/threonine kinase (e.g., Abl, Raf) at clinically achievable concentrations. Preclinical trials have shown Crenolanib to be active in inhibiting both wild-type and mutant FLT3. Crenolanib is cytotoxic to the FLT3/ITD-expressing leukemia cell lines Molm14 and MV411, with IC50s of 7 nM and 8 nM, respectively. In immunoblots, crenolanib inhibited phosphorylation of both the wild-type FLT3 receptor (in SEMK2 cells) and the FLT3/ITD receptor (in Molm14 cells) in culture medium with IC50s of 1-3 nM. Importantly, the IC50 of crenolanib against the D835Y mutated form of FLT3 was 8.8 nM in culture medium. Furthermore, crenolanib had cytotoxic activity against primary samples that were obtained from patients who had developed D835 mutations while receiving FLT3 TKIs. In vitro, the IC50 of crenolanib for inhibition of FLT3/ITD in plasma was found to be 34 nM, indicating a relatively low degree of plasma protein binding. From pharmacokinetic studies of crenolanib in solid tumor patients, steady state trough plasma levels of roughly 500 nM were found to be safe and tolerable, suggesting that crenolanib could potentially inhibit the target in vivo. Crenolanib has no significant activity against c-KIT, which may be an advantage in that myelosuppression can be avoided.1Furthermore, there was no evidence of QTc prolongation in patients treated with crenolanib. In summary, crenolanib offers a number of advantages over other FLT3 TKIs. Clinical trials of crenolanib in AML patients with FLT3 activating mutations are being planned.

Obatoclax (GX15-070) is a novel BH3 mimetic pan Bcl- 2 inhibitor. The clinically studied formulation is as obatoclax mesylate (Box 1), a salt. It is only under study as an intravenous preparation. It functions to block BH3-mediated binding of Bcl-2, Bcl-XL, Mcl-1 and A1 to Bax and Bak. Bax and Bak thus are unopposed and able to dimerize to allow initiation of intrinsic apoptosis. Preclinically, obatoclax has been shown to reverse inhibition of Bax or Bak by Bcl-2, Bcl-XL, Bcl-w and Mcl-1. Obatoclax was discovered by Gemin X, which was acquired by Cephalon, which has since been acquired by Teva Pharmaceuticals. Obatoclax had been in phase III clinical trials by Gemin X Biotechnologies (subsidiary of Teva) for the treatment of non-small lung cancer (NSCLC). The compound received orphan drug designation in the U.S. in 2004 for the treatment of chronic lymphocytic leukemia (CLL). However, Teva discontinued the development of obatoclax in 2013.

Atrasentan (ABT-627, A-127722) is a selective endothelin A receptor antagonist. Atrasentan is being developed by AbbVie as an oral treatment for diabetic nephropathies.Abbott Laboratories was conducting clinical development of atrasentan for the treatment of certain cancers, including phase II trials for prostate cancer. However, no recent development has been reported for cancer indications and development is presumed to be discontinued.

Barasertib (AZD1152) is a dihydrogen phosphate prodrug of a pyrazoloquinazoline Aurora kinase inhibitor [AZD1152–hydroxyquinazoline pyrazol anilide (HQPA)] and is converted rapidly to the active AZD1152-HQPA in plasma. AstraZeneca was developing the aurora kinase inhibitor, barasertib (AZD 1152) as a therapeutic for cancer. AZD1152-HQPA is a highly potent and selective inhibitor of Aurora B (Ki, 0.36nmol/L) compared with Aurora A (Ki, 1,369nmol/L) and has a high specificity versus a panel of 50 other kinases. Consistent with inhibition of Aurora B kinase, addition of AZD1152-HQPA to tumour cells in vitro induces chromosome misalignment, prevents cell division, and consequently reduces cell viability and induces apoptosis. Barasertib (AZD1152) potently inhibited the growth of human colon, lung, and haematologic tumour xenografts (mean tumour growth inhibition range, 55% to ≥100%; P < 0.05) in immunodeficient mice. Detailed pharmacodynamic analysis in colorectal SW620 tumour-bearing athymic rats treated i.v. with Barasertib (AZD1152) revealed a temporal sequence of phenotypic events in tumours: transient suppression of histone H3 phosphorylation followed by accumulation of 4N DNA in cells (2.4-fold higher compared with controls) and then an increased proportion of polyploid cells (>4N DNA, 2.3-fold higher compared with controls). Histologic analysis showed aberrant cell division that was concurrent with an increase in apoptosis in AZD1152-treated tumours. Bone marrow analyses revealed transient myelosuppression with the drug that was fully reversible following cessation of Barasertib (AZD1152) treatment. Barasertib (AZD1152) was in phase III for the treatment of Acute myeloid leukaemia, but later these studies were discontinued.

Sanguinarine is an extract of the bloodroot plant Sanguinaria canadensis, a member of the poppy family. It is an inhibitor of protein phosphatases PP1, PP2C and PP2B in vitro. Also inhibits mitogen-activated protein kinase phosphatase-1 (MKP-1) and other enzymes. Sanguinarine exerts a protective effect in cerebral ischemia, and this effect is associated with its anti-inflammatory and anti-apoptotic properties. It was clinically tested as an agent against gingivitis and tooth plaques.

Nafoxidine is a nonsteroidal antiestrogen available as an investigational agent from the Investigational Drug Branch of the National Cancer Institute. It has been used effectively in the treatment of breast cancer patients. Nafoxidine competes with endogenous estrogen for binding to specific estrogen receptors. This agent also inhibits angiogenesis in some tissues by blocking the effects of fibroblast growth factor (FGF) and vascular endothelial growth factor (VEGF); paradoxically, it may enhance angiogenesis in uterine tissue. Nafoxidine also induces oxidative stress, protein kinase C and calcium signaling.