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  • The ADME profile of AAT was


    The ADME profile of AAT-008 () was very promising, with high stability in HLM. The pre-clinical pharmacokinetic properties of AAT-008 were also assessed in rats (Sprague-Dawley, male), dogs (beagle, male), and monkeys (cynomolgus, male). The experimentally determined parameters are summarized in . AAT-008 was absorbed into the systemic circulation following oral administration to rats, dogs, and monkeys with a of 0.438–8.00h. In all the pre-clinical species, AAT-008 showed good oral bioavailability in rats, dogs, and monkeys with 73.6%, 80.6%, and 73.3%, respectively. AAT-008 had a pharmacokinetic profile with low clearance (CL) and moderate volume of distribution (). After intravenous injection of AAT-008 at the dose of 1mg/kg, the plasma elimination half-life () values are 4.59h in rats, 8.43h in dogs, and 14.5h in monkeys. Moreover, AAT-008 () had a significantly improved pharmacological profile over grapiprant, as was demonstrated in acute and chronic inflammatory pain models in rats (). The oral dosing of AAT-008 reduced NAD/NADH Quantitation Colorimetric Kit induced mechanical hyperalgesia in rats in a dose dependent manner with an MED 1mg/kg, PO at 1-h post dosing (vs 30mg/kg, PO for grapiprant). In a model of chronic inflammatory pain, CFA induced weight bearing deficit in the rat, AAT-008 exhibited an analgesic effect in a dose dependent manner with an MED of 1mg/kg, PO (vs 20mg/kg, PO for grapiprant). AAT-008 exhibited good passive permeability and good metabolic stability in HLM (>120min) or hepatocytes (>360min). Inhibitory effects of AAT-008 (1μM) on CYP1A, CYP2C9, CYP2C19, CYP2D6, and CYP3A activities were determined to be less than 5%. In conclusion, a novel series of -acylaminomethylbenzoic acid-based selective prostaglandin EP4 receptor antagonists has been identified, starting from -acyl sulfonamide HTS hit , followed by hit-to-lead optimization using in-house compound library. Lead compound was sequentially optimized by dividing it into three parts. The most significant improvement was achieved when a ()-methyl substituent was introduced at the benzylic position. Eventually, (AAT-008) was identified as a development candidate, having excellent potency, selectivity for EP4, and metabolic stability. Superior potency of AAT-008 to grapiprant was demonstrated in different models. AAT-008 was stable in human liver microsomes or hepatocytes and was predicted to be well absorbed in humans. AAT-008 was selected as a candidate for preclinical development and subsequent clinical studies. The projected efficacious oral dosing regimen of AAT-008 for OA pain is 1–20mg QD. Acknowledgements
    Introduction The ability to choose between life and death provides the mammalian immune system with the capacity to discriminate between foreign chemical entities and the body\'s own components. Interaction of BCR on mature B cells with foreign antigens initiates immune responses, while recognition of antigens by BCR on immature B cells leads to their depletion by apoptosis [1]. Due to its unique surface phenotype resembling immature B cells (membrane immunoglobulin M-positive [mIgM+], mIgD−/low, FcRlow, Faslow and major histocompatibility complex [MHC] class IIlow), the murine B lymphoma cell line WEHI 231 has been widely used as a model for dissecting the molecular mechanism underlying clonal deletion of immature B lymphocytes, which undergo growth arrest and apoptosis following ligation of the B cell receptor (BCR) [2], [3]. B-cell fate is determined by the balance between survival and death signals initiated through BCR. Several different signaling pathways have been implicated in BCR-mediated apoptosis [4]. Crucial survival pathways involve PI3K/AKT, RAS–RAF–ERK and NF-κB dependent pathways [5]. Activation of NF-κB by the canonical pathway involves phosphorylation of IkBa by IkB kinase (IKK), followed by ubiquitination and proteasomal degradation. Consequently, NF-κB translocates to the nucleus, and promotes the expression of anti-apoptotic genes [6].