Preclinical Data with KIT D816V Inhibitor Bezuclastinib (CGT9486) Demonstrates High Selectivity and Minimal Brain Penetrance

The molecular pathogenesis of Systemic Mastocytosis (SM) is driven by mutations in the KIT gene, with 95% of patients having a mutation in exon 17, D816V, leading to constant proliferation of mast cells (Garcia-Montero et al, 2006; Jara-Acevedo et al, 2015; Vaes et al, 2017). Targeted therapeutics have revealed clinical activity in these patients, but toxicities such as cognitive effects, intracranial hemorrhage, hypertension, and edema may limit dosing and availability of these therapies. While the exact cause of these effects is difficult to determine, numerous closely related kinases, such as wild type PDGFRα, PDGFRβ, KIT, VEGFR2 (KDR), and CSF1R (FMS), are considered to be anti-targets, with previous evidence of their inhibition linked to observed clinical toxicities (Liu & Kurzrock, 2015; Giles et al., 2009; Jayson et al., 2005). Bezuclastinib (CGT9486) was designed to selectively inhibit KIT D816V versus these other closely related kinase anti-targets. Additionally, we demonstrate that bezuclastinib has minimal brain penetration, together with no observed CNS-related toxicities in nonclinical studies. Herein, we present results from cell-based kinase profiling assays, which demonstrate that bezuclastinib has a significant and unique selectivity to KIT D816V relative to the aforementioned kinases when tested head-to-head against other clinically relevant compounds in SM. Additionally, a similar selectivity profile was observed for a broader panel of kinases, ion channels, transporters, and enzymes, which will be presented here, including drug concentrations and target engagement achieved with recent in vivo studies. Importantly, we also show that bezuclastinib has minimal brain penetration, a preferred feature of an anti-Kit molecule due to CNS-related adverse events observed in these indications. In a tissue distribution study performed in rats, bezuclastinib shows a brain:plasma ratio <0.1 following 3 day administration at 25 mg/kg, a dose that closely correlates with clinical plasma exposure. This was supported functionally by assessing neurobehavioral effects of bezuclastinib at dose levels up to 100 mg/kg in rats which showed no CNS related effects. This attractive selectivity and nonclinical safety profile, combined with early clinical data in advanced solid tumors (Trent et al, 2020), supports the potential for a best-in-class KIT inhibitor. Bezuclastinib is currently under clinical investigation in advanced SM with additional clinical studies planned in non-advanced SM and imatinib-resistant GIST. Disclosures Guarnieri: Cogent Biosciences: Current Employment. Cable: Cogent Biosciences: Current Employment. Bouhana: Cogent Biosciences: Current Employment. Sullivan: Cogent Biosciences: Current Employment. Ball: Cogent Biosciences: Current Employment. Sachs: Cogent Biosciences: Current Employment. Winski: Cogent Biosciences: Current Employment. Robinson: Cogent Biosciences: Current Employment.

Tissue Distribution Study of Poloxamer188 in Rats by Ultra-High-Performance Liquid Chromatography Quadrupole Time of Flight/Mass Spectrometry with MSALL-Based Approach

Poloxamer188 (PL188), as one of the most commonly used pharmaceutical excipients, has unique physicochemical properties and good biocompatibility, and so is playing an increasingly extensive role in the field of medicine. Currently, there are few studies on the tissue distribution of PL188 in vivo. In this study, the LC-MS method based on MSALL technique of quadrupole time of flight mass spectrometry for absolute quantitative analysis of poloxamer 188 in biological substrates was established for the first time. The tissue distribution of poloxamer188 in SD rats were studied using the established quantitative analysis method. To explore the distribution of PL188 in organs and tissues, PL188 was administered via rat tail vein at a dose of 5 mg/kg. Eight kinds of tissues including heart, liver, spleen, lung, kidney, stomach, muscle and brain of rats were collected at 0.25 h, 1 h and 4 h after administration. Tissue distributions showed the highest level was observed in kidney, then in stomach, which indicated PL188 mainly bioaccumulated in the kidney. This study can provide references for the further study of PL188.

Simultaneous Measurement of Tadehaginoside and its Principal Metabolite in Rats by HPLC–MS/MS and its Application in Pharmacokinetics and Tissue Distribution Study

Background Tadehaginoside, an active ingredient isolated from Tadehagi triquetrum L., exhibited various biological activities. However, the pharmacokinetics and tissue-distribution which affects tadehaginoside’s therapeutic actions and application remain elusive.MethodsTo clarify the metabolism of tadehaginoside in vivo, a high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was established to detect the level of tadehaginoside in plasma and eleven tat tissues (brain, heart, liver, spleen, lungs, kidneys, stomach, small intestine, skeletal muscle, body fat, and testes). Besides, this validated method was also successfully applied to the quantitative determination of its metabolite, p-hydroxycinnamic acid (HYD) in plasma. The pharmacokinetic and tissue-distribution of tadehaginoside were investigated by this developed method. ResultsThe pharmacokinetic study indicated that tadehaginoside in plasma of rats with intragastric administration showed relatively low concentration may be due to the formation of its metabolite, and the quick absorption of tadehaginoside was detected following intravenous administration. Tissue-distribution study indicated that kidney and spleen were the major distribution organs for tadehaginoside in rats. ConclusionsThese results could provide clues for exploring the bioactivity of tadehaginoside based on its pharmacokinetic characteristics.