Millennium Pharmaceuticals Inc's tandutinib (MLN-518), a piperazinyl derivative of quinazoline, is an orally active inhibitor of FLT3 kinase and family members PDGFR beta and c-Kit. Tandutinib inhibited FLT3 phosphorylation, downstream signaling and malignant growth in vitro and in animal models. The drug exhibited limited activity as a single agent in phase I and II clinical trials in patients with AML and myelodysplastic syndrome, but displayed promising antileukemic activity (90% complete remissions) in a phase I/II trial in patients with newly diagnosed AML when administered in combination with cytarabine and daunorubicin. Phase II clinical trials for tandutinib in patients with Glioblastoma have being discontinued. The use of tandutinib to treat AML has been granted fast-track status by the U.S. Food and Drug Administration. Phase II trials were underway., but later withwrawn.

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.

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.

Ralimetinib (LY2228820), a trisubstituted imidazole derivative, is a potent and selective, ATP-competitive inhibitor of the α- and β-isoforms of p38 mitogen-activated protein kinase. LY2228820 produced significant tumor growth delay in multiple in vivo cancer models (melanoma, non-small cell lung cancer, ovarian, glioma, myeloma, breast). Eli Lilly is developing ralimetinib for the treatment of cancer.

Esculin (Esculoside), a coumarin compound derived from the horse chestnut and the traditional Chinese herbs such as Cortex Fraxini, has long been used for treating inflammatory and vascular diseases. The main activities of Esculoside focus on capillary protection, as it improves capillary permeability and fragility. It is reported to inhibit catabolic enzymes such as hyaluronidase and collagenase, thus preserving the integrity of the perivascular connective tissue. Esculin has various biological activities including anti-oxidant activity, intestinal anti-inflammatory activity, anti-cancer activity and growth inhibition of human leukemia cells. Esculin inhibits lipid peroxidation and scavenges hydroxyl radicals in the rat liver and exerts anti-inflammatory activity in both carrageenan- and zymosan-induced paw edema in mice. Esculin has the gastroprotective effect in cold-restraint stress and pylorus ligation-induced ulcer models. Esculin is used in a microbiology laboratory to aid in the identification of bacterial species (especially Enterococci and Listeria).

Esculin (Esculoside), a coumarin compound derived from the horse chestnut and the traditional Chinese herbs such as Cortex Fraxini, has long been used for treating inflammatory and vascular diseases. The main activities of Esculoside focus on capillary protection, as it improves capillary permeability and fragility. It is reported to inhibit catabolic enzymes such as hyaluronidase and collagenase, thus preserving the integrity of the perivascular connective tissue. Esculin has various biological activities including anti-oxidant activity, intestinal anti-inflammatory activity, anti-cancer activity and growth inhibition of human leukemia cells. Esculin inhibits lipid peroxidation and scavenges hydroxyl radicals in the rat liver and exerts anti-inflammatory activity in both carrageenan- and zymosan-induced paw edema in mice. Esculin has the gastroprotective effect in cold-restraint stress and pylorus ligation-induced ulcer models. Esculin is used in a microbiology laboratory to aid in the identification of bacterial species (especially Enterococci and Listeria).