Selonsertib, also known as GS-4997, is a small-molecule inhibitor of apoptosis signal-regulating kinase 1 (ASK1), which promotes inflammation, apoptosis and fibrosis in settings of increased oxidative stress associated with NASH pathogenesis. GS-4997 prevents the production of inflammatory cytokines, down-regulates the expression of genes involved in fibrosis, suppresses excessive apoptosis and inhibits cellular proliferation. GS-4997 is currently being evaluated in an ongoing Phase 2 study in patients with NASH and moderate to severe liver fibrosis.

CK-101 is an orally available third-generation and selective inhibitor of certain epidermal growth factor receptor (EGFR) activating mutations, including the resistance mutation T790M, with potential antineoplastic activity. Activating mutations in the tyrosine kinase domain of EGFR are found in approximately 20% of patients with advanced Non-Small Cell Lung Cancer (NSCLC). Compared to chemotherapy, first-generation EGFR inhibitors significantly improved ORR and progression-free survival in previously untreated NSCLC patients carrying EGFR mutations. However, tumor progression could develop due to resistance mutations, often within months of treatment with first-generation EGFR inhibitors. CK-101 designed to be highly selective against the T790M mutation while sparing wild-type EGFR, thereby improving tolerability and safety profiles. Compared to some other EGFR inhibitors, CK-101 may have therapeutic benefits in tumors with T790M-mediated drug resistance. This agent shows minimal activity against wild-type EGFR (WT EGFR) and does not cause dose-limiting toxicities that occur during the use of non-selective EGFR inhibitors, which also inhibit WT EGFR.

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.

Lestaurtinib (CEP-701, KT-5555) is an orally bio-available polyaromatic indolocarbazole alkaloid derived from K-252a. Lestaurtinib is a multi-targeted tyrosine kinase inhibitor which has been shown to potently inhibit FLT3 at nanomolar concentrations in preclinical studies, leading to its rapid development as a potential targeted agent for treatment of AML. Phase I studies have shown lestaturtinib to be an active agent particularly when used in combination with cytotoxic drugs. Currently, Phase II and Phase III studies are underway aiming to establish the future of this agent as a treatment option for patients with FLT3-ITD AML.

INCB-039110 (also known as Itacitinib) is an orally bioavailable inhibitor of Janus-associated kinase 1 (JAK1) with potential antineoplastic activity patented by Incyte Corporation for treatment of autoimmune disorders and cancer. Upon oral administration of NCB-039110, this agent selectively inhibits the phosphorylation and activity of JAK1, which may result in inhibition of JAK1-mediated signaling, induction of apoptosis, and reduction of cell proliferation in JAK1-expressing tumor cells. INCB-039110 in combination with nab-paclitaxel plus gemcitabine demonstrated an acceptable safety profile with clinical activity seen in patients with advanced solid tumors including pancreatic cancers. Based on the potential for additive or synergistic effects, NCB-039110 is currently being explored in combination with immunotherapeutic agents including the anti-programmed cell death protein 1 antibody and small molecule inhibitors.