Belzutifan (PT2977) is an orally active, small molecule inhibitor of hypoxia-inducible factor (HIF)-2alpha (HIF-2a). Upon oral administration, HIF-2alpha inhibitor PT2977 binds to and blocks the function of HIF-2alpha, thereby preventing HIF-2alpha heterodimerization and its subsequent binding to DNA. This results in decreased transcription and expression of HIF-2alpha downstream target genes, many of which regulate hypoxic signaling. This inhibits cell growth and survival of HIF-2alpha-expressing tumor cells. HIF-2alpha, the alpha subunit for the heterodimeric transcription factor HIF-2, is overexpressed in many cancers and promotes tumorigenesis.

Dacinostat (also known as LAQ824), is a hydroxamate histone deacetylase inhibitor with potential anticancer activity. Dacinostat inhibits histone deacetylase enzymatic activities in vitro and transcriptionally activated the p21 promoter in reporter gene assays. Tumor cells treated with Dacinostat caused acetylation of HSP90 and degradation of its cargo oncoproteins. Flow cytometry studies revealed that both tumor cell lines and normal diploid fibroblasts arrested in the G2/M phase of the cell cycle after Dacinostat treatment. However, an increased sub-G1 population at 48 h (reminiscent of apoptotic cells) was only observed in the cancer cell lines treated with Dacinostat. Dacinostat exhibited antitumor effects in a xenograft animal models. In phase I trials, Dacinostat was well tolerated at doses that induced accumulation of histone acetylation, with higher doses inducing changes consistent with HSP90 inhibition. In another phase 1 in patients with advanced solid tumors, grade 3 or 4 toxicities were observed. Dacinostat had been in phase II clinical trials by Novartis for the treatment of solid tumors but further studies were discontinued.

AST-1306, also known as Allitinib, is an orally active potent, selective, irreversible inhibitor of the HER family of receptor tyrosine kinases. AST-1306 inhibits the enzymatic activities of wild-type epidermal growth factor receptor (EGFR) and ErbB2 as well as EGFR resistant mutant in both cell-free and cell-based systems. AST1306 potently suppressed tumor growth in ErbB2-overexpressing adenocarcinoma xenograft and FVB-2/N(neu) transgenic breast cancer mouse models. Allitinib is in Phase I clinical trial for the treatment of advanced solid tumors. Serious adverse effects detected were: diarrhea, dehydration and hyperbilirubinemia.

IPI-549 is an orally bioavailable, highly selective small molecule inhibitor of the gamma isoform of phosphoinositide-3 kinase (PI3K-gamma) with potential immunomodulating and antineoplastic activities. Upon administration, IPI-549 prevents the activation of the PI3K-gamma-mediated signaling pathways, which may lead to a reduction in cellular proliferation in PI3K-gamma-expressing tumor cells. In addition, this agent is able to modulate anti-tumor immune responses and inhibit tumor-mediated immunosuppression. Unlike other isoforms of PI3K, the gamma isoform is overexpressed in certain tumor cell types and immune cells; its expression increases tumor cell proliferation and survival. By selectively targeting the gamma isoform, PI3K signaling in normal, non-neoplastic cells is minimally or not affected, which results in a reduced side effect profile. Preclinical data in multiple solid tumor models have demonstrated that IPI-549 targets immune cells and alters the immune-suppressive microenvironment, promoting an anti-tumor immune response that leads to tumor growth inhibition. A Phase 1 study of IPI-549 in patients with advanced solid tumors is ongoing.

OSI-930 (now SIM-930) is a potent, oral small-molecule receptor tyrosine kinase inhibitor, which acts predominantly against VEGF receptors (VEGFR), c-Kit, and platelet-derived growth factor receptors. OSI-930 has a pharmacokinetic-pharmacodynamic profile distinct from other RTK inhibitors, with potent antitumor activity in multiple xenograft models. OSI-930 passed through phase I clinical trial in the USA (in patients with advanced solid tumors) and recieved the clinical approval by China FDA after being out-licensed to Simcere Pharma in China.

HSP-990 is an oral Hsp90 inhibitor being developed by Novartis in a collaboration with Vernalis. It is also known by NVP-HSP990. HSP-990 is an inhibitor of human heat-shock protein 90 (Hsp90) with potential antineoplastic activity. Hsp-990 binds to and inhibits the activity of Hsp90, which may result in the proteasomal degradation of oncogenic client proteins, including HER2/ERBB2, and the inhibition of tumor cell proliferation. Hsp90, upregulated in a variety of tumor cells, is a molecular chaperone that plays a key role in the conformational maturation, stability and function of oncogenic signaling proteins, such as HER2/ERBB2, AKT, RAF1, BCR-ABL, and mutated p53, as well as many other molecules that are important in cell cycle regulation and/or immune responses.

PF-477736 is a selective, potent and ATP-competitive Chk1 inhibitor. Compound was tested in combination with gembcitabine in phase I clinical trials in patients with advanced solid tumors.

XK-469 (2-[4-(7-chloro-2-quinoxalinyloxy)phenoxy]-propionic acid) is a novel synthetic quinoxaline phenoxypropionic acid derivative. The R-isomer of XK-469 was approximately twice as effective as the S-isomer of XK-469R. R( )-isomers induce reversible protein DNA crosslinks in mammalian cells. It acts as a selective topoisomerase IIβ inhibitor. A phase I study was performed to determine the safety and pharmacokinetics of XK-469, (R)- in patients with various neoplasms.

RO4987655 is a highly selective non-competitive small molecule inhibitor of MEK. RO4987655 has a strong anti-proliferation efficacy in various tumor cells including COLO205, HT29, QG56, MIA and C32 with IC50 values of 0.86nM, 1.7nM, 9.5nM, 3.3nM and 8.4nM, respectively. In addition, RO4987655 is found to have antitumor activity in a wide range of human cancer xenograft models. In the HT-29 human colon cancer xenograft, RO4987655 shows a strong inhibition of pERK formation as well as tumor regression. RO4987655 shows clinical activity in both patients with BRAF wild-type melanoma and BRAF V600-mutated melanoma. It is also efficacious in patients with KRAS-mutated non-small cell lung cancer but not KRAS-mutated colorectal cancer.

AT13148, being developed by Astex Pharmaceuticals and its collaborators, is an orally active small molecule inhibitor of Rho activated kinases (ROCK) 1 and 2 and of protein kinase (PK) A and is currently in phase 1 clinical studies under Cancer Research UK’s Clinical Development Program (CDP). AT13148 is currently being tested in a phase 1 clinical trial in patients with advanced solid tumors.