A novel series of 3-amino-piperidin-2-one-based calcitonin gene-related peptide (CGRP) receptor antagonists was invented based upon the discovery of unexpected structure-activity observations. Initial exploration of the structure-activity relationships enabled the generation of a moderately potent lead structure (4). A series of modifications, including ring contraction and inversion of stereocenters, led to surprising improvements in CGRP receptor affinity. These studies identified compound 23, a structurally novel potent, orally bioavailable CGRP receptor antagonist.

Background The trigeminal sensory neuropeptide calcitonin gene–related peptide (CGRP) is identified as an essential element in migraine pathogenesis. Methods In vitro and in vivo studies evaluated pharmacologic properties of the CGRP receptor antagonist atogepant. Radioligand binding using 125 I-CGRP and cyclic adenosine monophosphate (cAMP) accumulation assays were conducted in human embryonic kidney 293 cells to assess affinity, functional potency and selectivity. Atogepant in vivo potency was assessed in the rat nitroglycerine model of facial allodynia and primate capsaicin-induced dermal vasodilation (CIDV) pharmacodynamic model. Cerebrospinal fluid/brain penetration and behavioral effects of chronic dosing and upon withdrawal were evaluated in rats. Results Atogepant exhibited high human CGRP receptor-binding affinity and potently inhibited human α-CGRP-stimulated cAMP responses. Atogepant exhibited significant affinity for the amylin1 receptor but lacked appreciable affinities for adrenomedullin, calcitonin and other known neurotransmitter receptor targets. Atogepant dose-dependently inhibited facial allodynia in the rat nitroglycerine model and produced significant CIDV inhibition in primates. Brain penetration and behavioral/physical signs during chronic dosing and abrupt withdrawal were minimal in rats. Conclusions Atogepant is a competitive antagonist with high affinity, potency and selectivity for the human CGRP receptor. Atogepant demonstrated a potent, concentration-dependent exposure/efficacy relationship between atogepant plasma concentrations and inhibition of CGRP-dependent effects.

Inhibition of glucosylceramide synthase (GCS) has been proposed as a therapeutic strategy for the treatment of Parkinson's Disease (PD), particularly in patients where glycosphingolipid accumulation and lysosomal impairment are thought to be contributing to disease progression. Herein, we report the late-stage optimization of an orally bioavailable and CNS penetrant isoindolinone class of GCS inhibitors. Starting from advanced lead 1, we describe efforts to identify an improved compound with a lower human dose projection, minimal P-glycoprotein (P-gp) efflux, and acceptable pregnane X receptor (PXR) profile through fluorine substitution. Our strategy involved the use of predicted volume ligand efficiency to advance compounds with greater potential for low human doses down our screening funnel. We also applied minimized electrostatic potentials (V-min) calculations for hydrogen bond acceptor sites to rationalize P-gp SAR. Together, our strategies enabled the alignment of a lower human dose with reduced P-gp efflux, and favorable PXR selectivity for the discovery of compound 12.

Parkinson's disease is the second most prevalent progressive neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra. Loss-of-function mutations in GBA, the gene that encodes for the lysosomal enzyme glucosylcerebrosidase, are a major genetic risk factor for the development of Parkinson's disease potentially through the accumulation of glucosylceramide and glucosylsphingosine in the CNS. A therapeutic strategy to reduce glycosphingolipid accumulation in the CNS would entail inhibition of the enzyme responsible for their synthesis, glucosylceramide synthase (GCS). Herein, we report the optimization of a bicyclic pyrazole amide GCS inhibitor discovered through HTS to low dose, oral, CNS penetrant, bicyclic pyrazole urea GCSi's with in vivo activity in mouse models and ex vivo activity in iPSC neuronal models of synucleinopathy and lysosomal dysfunction. This was accomplished through the judicious use of parallel medicinal chemistry, direct-to-biology screening, physics-based rationalization of transporter profiles, pharmacophore modeling, and use a novel metric: volume ligand efficiency.

Mutations in the lysosomal enzyme glucocerebrosidase (GCase, GBA1 gene) are the most common genetic risk factor for developing Parkinson's disease (PD). GCase metabolizes the glycosphingolipids glucosylceramide (GlcCer) and glucosylsphingosine (GlcSph). Mutations in GBA1 reduce enzyme activity and the resulting accumulation of glycosphingolipids may contribute to the underlying pathology of PD, possibly via altering lysosomal function. While reduction of GCase activity exacerbates α-synuclein (α-syn) aggregation, it has not been determined that this effect is the result of altered glycosphingolipid levels and lysosome function or some other effect of altering GCase. The glycosphingolipid GlcCer is synthesized by a single enzyme, glucosylceramide synthase (GCS), and small molecule inhibitors (GCSi) reduce cellular glycosphingolipid levels. In the present studies, we utilize a preformed fibril (PFF) rodent primary neuron in vitro model of α-syn pathology to investigate the relationship between glycosphingolipid levels, α-syn pathology, and lysosomal function. In primary cultures, pharmacological inhibition of GCase and D409V GBA1 mutation enhanced accumulation of glycosphingolipids and insoluble phosphorylated α-syn. Administration of a novel small molecule GCSi, benzoxazole 1 (BZ1), significantly decreased glycosphingolipid concentrations in rodent primary neurons and reduced α-syn pathology. BZ1 rescued lysosomal deficits associated with the D409V GBA1 mutation and α-syn PFF administration, and attenuated α-syn induced neurodegeneration of dopamine neurons. In vivo studies revealed BZ1 had pharmacological activity and reduced glycosphingolipids in the mouse brain to a similar extent observed in neuronal cultures. These data support the hypothesis that reduction of glycosphingolipids through GCS inhibition may impact progression of synucleinopathy and BZ1 is useful tool to further examine this important biology.

A growing body of evidence has implicated the calcitonin gene–related peptide (CGRP) receptors in migraine pathophysiology. With the approval of monoclonal antibodies targeting CGRP or the CGRP receptor, the inhibition of CGRP-mediated signaling emerged as a promising approach for preventive treatments of migraine in adults. Recently, small-molecule anti-CGRP treatments have shown efficacy for treating migraine. The current studies aimed to characterize the pharmacologic properties of ubrogepant, an orally bioavailable CGRP receptor antagonist for the acute treatment of migraine. In a series of ligand-binding assays, ubrogepant exhibited a high binding affinity for native (Ki = 0.067 nM) and cloned human (Ki = 0.070 nM) and rhesus CGRP receptors (Ki = 0.079 nM), with relatively lower affinities for CGRP receptors from rat, mouse, rabbit, and dog. In functional assays, ubrogepant potently blocked human α-CGRP−stimulated cAMP response (IC50 of 0.08 nM) and exhibited highly selective antagonist activity for the CGRP receptor compared with other members of the human calcitonin receptor family. Furthermore, the in vivo CGRP receptor antagonist activity of ubrogepant was evaluated in a pharmacodynamic model of capsaicin-induced dermal vasodilation (CIDV) in rhesus monkeys and humans. Results demonstrated that ubrogepant produced concentration-dependent inhibition of CIDV with a mean EC50 of 3.2 and 2.6 nM in rhesus monkeys and humans, respectively. Brain penetration studies with ubrogepant in monkeys showed a cerebrospinal fluid:plasma ratio of 0.03 and low CGRP receptor occupancy. In summary, ubrogepant is a competitive antagonist with high affinity, potency, and selectivity for the human CGRP receptor. SIGNIFICANCE STATEMENT Ubrogepant is a potent, selective, orally delivered, small-molecule competitive antagonist of the human CGRP. In vivo studies using a pharmacodynamic model of CIDV in rhesus monkeys and humans demonstrated that ubrogepant produced concentration-dependent inhibition of CIDV, indicating a predictable pharmacokinetic-pharmacodynamic relationship.

In our efforts to develop CGRP receptor antagonists as backups to MK-3207, 2, we employed a scaffold hopping approach to identify a series of novel oxazolidinone-based compounds. The development of a structurally diverse, potent (20, cAMP + HS IC50 = 0.67 nM), and selective compound (hERG IC50 = 19 μM) with favorable rodent pharmacokinetics (F = 100%, t1/2 = 7 h) is described. Key to this development was identification of a 3-substituted spirotetrahydropyran ring that afforded a substantial gain in potency (10 to 35-fold).

Elevated plasma homocysteine (Hcy) levels are an independent risk factor for the onset and progression of Alzheimer’s disease. Reduction of Hcy to normal levels therefore presents a new approach for disease modification. Hcy is produced by the cytosolic enzyme S-adenosylhomocysteine hydrolase (AHCY), which converts S-adenosylhomocysteine (SAH) to Hcy and adenosine. Herein we describe the design and characterization of novel, substrate-based S-adenosylhomocysteine hydrolase inhibitors with low nanomolar potency in vitro and robust activity in vivo.