Positive allosteric modulators (PAMs) of the M4 muscarinic acetylcholine receptor (mAChR) represent a novel approach for the treatment of psychotic symptoms associated with schizophrenia and other neuropsychiatric disorders. We recently reported that the selective M4 PAM VU0152100 produced an antipsychotic drug-like profile in rodents after amphetamine challenge. Previous studies suggest that enhanced cholinergic activity may also improve cognitive function and reverse deficits observed with reduced signaling through the N-methyl-d-aspartate subtype of the glutamate receptor (NMDAR) in the central nervous system. Prior to this study, the M1 mAChR subtype was viewed as the primary candidate for these actions relative to the other mAChR subtypes. Here we describe the discovery of a novel M4 PAM, VU0467154, with enhanced in vitro potency and improved pharmacokinetic properties relative to other M4 PAMs, enabling a more extensive characterization of M4 actions in rodent models. We used VU0467154 to test the hypothesis that selective potentiation of M4 receptor signaling could ameliorate the behavioral, cognitive, and neurochemical impairments induced by the noncompetitive NMDAR antagonist MK-801. VU0467154 produced a robust dose-dependent reversal of MK-801-induced hyperlocomotion and deficits in preclinical models of associative learning and memory functions, including the touchscreen pairwise visual discrimination task in wild-type mice, but failed to reverse these stimulant-induced deficits in M4 KO mice. VU0467154 also enhanced the acquisition of both contextual and cue-mediated fear conditioning when administered alone in wild-type mice. These novel findings suggest that M4 PAMs may provide a strategy for addressing the more complex affective and cognitive disruptions associated with schizophrenia and other neuropsychiatric disorders.

Allosteric modulation of AMPA, NR2B, mGlu2, mGlu5 and M1, targeting glutamatergic dysfunction, represents a significant area of research for the treatment of schizophrenia. Of these targets, clinical promise has been demonstrated using muscarinic activators for the treatment of Alzheimer’s disease (AD) and schizophrenia. These diseases have inspired researchers to determine the effects of modulating cholinergic transmission in the forebrain, which is primarily regulated by one of five subtypes of muscarinic acetylcholine receptor (mAChR), a subfamily of G-protein-coupled receptors (GPCRs). Of these five subtypes, M1 is highly expressed in brain regions responsible for learning, cognition and memory. Xanomeline, an orthosteric muscarinic agonist with modest selectivity, was one of the first compounds that displayed improvements in behavioral disturbances in AD patients and efficacy in schizophrenics. Since these initial clinical results, many scientists, including those in our laboratories, have strived to elucidate the role of M1 with compounds that display improved selectivity for this receptor by targeting allosteric modes of receptor activation. A survey of selected compounds in this area will be presented.

Accumulating evidence suggests that selective M 4 muscarinic acetylcholine receptor (mAChR) activators may offer a novel strategy for the treatment of psychosis. However, previous efforts to develop selective M 4 activators were unsuccessful because of the lack of M 4 mAChR subtype specificity and off-target muscarinic adverse effects. We recently developed VU0152100, a highly selective M 4 positive allosteric modulator (PAM) that exerts central effects after systemic administration. We now report that VU0152100 dose-dependently reverses amphetamine-induced hyperlocomotion in rats and wild-type mice, but not in M4 KO mice. VU0152100 also blocks amphetamine-induced disruption of the acquisition of contextual fear conditioning and prepulse inhibition of the acoustic startle reflex. These effects were observed at doses that do not produce catalepsy or peripheral adverse effects associated with non-selective mAChR agonists. To further understand the effects of selective potentiation of M 4 on region-specific brain activation, VU0152100 alone and in combination with amphetamine were evaluated using pharmacologic magnetic resonance imaging (phMRI). Key neural substrates of M 4 -mediated modulation of the amphetamine response included the nucleus accumbens (NAS), caudate-putamen (CP), hippocampus, and medial thalamus. Functional connectivity analysis of phMRI data, specifically assessing correlations in activation between regions, revealed several brain networks involved in the M 4 modulation of amphetamine-induced brain activation, including the NAS and retrosplenial cortex with motor cortex, hippocampus, and medial thalamus. Using in vivo microdialysis, we found that VU0152100 reversed amphetamine-induced increases in extracellular dopamine levels in NAS and CP. The present data are consistent with an antipsychotic drug-like profile of activity for VU0152100. Taken together, these data support the development of selective M 4 PAMs as a new approach to the treatment of psychosis and cognitive impairments associated with psychiatric disorders such as schizophrenia.

Myeloid cell leukemia-1 (Mcl-1) is a member of the Bcl-2 family of proteins responsible for the regulation of programmed cell death (PCD). Amplification of Mcl-1 is a common genetic aberration in human cancer whose overexpression contributes to the evasion of apoptosis and is one of the major resistance mechanisms for many chemotherapies. Mcl-1 mediates its effects primarily through interactions with pro-apoptotic BH3 containing proteins that achieve high affinity for the target by utilizing four hydrophobic pockets in its binding groove. Here we describe the discovery of Mcl-1 inhibitors using fragment based methods and structure-based design. These novel inhibitors exhibit low nanomolar binding affinities to Mcl-1 and greater than 500-fold selectivity over Bcl-xL. X-ray structures of lead Mcl-1 inhibitors when complexed to Mcl-1 provided detailed information on how these small-molecules bind to the target, and were used extensively to guide compound optimization.

Mcl-1 is an anti-apoptotic member of the Bcl-2 family of proteins that when overexpressed is associated with high tumor grade, poor survival, and resistance to chemotherapy. Mcl-1 is amplified in many human cancers, and knockdown of Mcl-1 using RNAi can lead to apoptosis. Thus, Mcl-1 is a promising cancer target. Here, we describe the discovery of picomolar Mcl-1 inhibitors that cause caspase activation, mitochondrial depolarization, and selective growth inhibition. These compounds represent valuable tools to study the role of Mcl-1 in cancer and serve as useful starting points for the discovery of clinically useful Mcl-1 inhibitors.

Herein we report the discovery and SAR of a novel series of M1 agonists based on the MLPCN probe, ML071. From this, VU0364572 emerged as a potent, orally bioavailable and CNS penetrant M1 agonist with high selectivity, clean ancillary pharmacology and enantiospecific activity.

ABSTRACT:The M 1 muscarinic acetylcholine receptor is thought to play an important role in memory and cognition, making it a potential target for the treatment of Alzheimer's disease (AD) and schizophrenia. Moreover, M 1 interacts with BACE1 and regulates its proteosomal degradation, suggesting selective M 1 activation could afford both palliative cognitive benefit as well as disease modification in AD. A key challenge in targeting the muscarinic acetylcholine receptors is achieving mAChR subtype selectivity. Our lab has previously reported the M 1 selective positive allosteric modulator ML169. Herein we describe our efforts to further optimize this lead compound by preparing analogue libraries and probing novel scaffolds. We were able to identify several analogues that possessed submicromolar potency, with our best example displaying an EC 50 of 310 nM. The new compounds maintained complete selectivity for the M 1 receptor over the other subtypes (M 2 −M 5 ), displayed improved DMPK profiles, and potentiated the carbachol (CCh)-induced excitation in striatal MSNs. Selected analogues were able to potentiate CCh-mediated nonamyloidogenic APPsα release, further strengthening the concept that M 1 PAMs may afford a disease-modifying role in the treatment of AD. KEYWORDS: Muscarinic, acetylcholine, positive allosteric modulator (PAM), ML169, Alzheimer's disease (AD), medium spiny neurons (MSNs), MLPCN T he muscarinic acetylcholine receptors (mAChRs) are members of the family A G-protein-coupled receptors (GPCRs) and comprise five subtypes (M 1 −M 5 ) that mediate a broad range of actions of the neurotransmitter acetylcholine (ACh, 1) in the central nervous system and other tissues (Figure 1) and play key roles in memory and attention mechanisms, motor control, nociception, regulation of sleepwake cycles, cardiovascular function, renal function, and GI function. 1 mAChR subtypes M 1 , M 3 , and M 5 are coupled to G q and stimulate phospholipase C and intracellular Ca 2+ release, while M 2 and M 4 are coupled to G i and block adenylyl cyclase. 2 Data from brain expression, cellular localization, and knockout mice have implicated that M 1 plays a vital role in both memory and cognition, 3 and numerous studies have shown efficacy in preclinical cognition models with selective M 1 activators. 4−7 Recently, studies have conclusively shown that M 1 interacts with BACE1 to regulate its protesomal degradation and that M 1 activation activates α-secretase, which leads to an increase in sAPPα thereby preventing the formation of Aβ via MAPK-and PKC-dependent pathways. 8 In addition, M 1 activation decreases τ phosphorylation; therefore, M 1 activation affects the major pathological hallmarks of AD. 8,9 Beyond the cholinergic and NMDA hypofunction hypotheses of schizophrenia where M 1 could play a critical therapeutic role, 10 BACE1 has also been linked to schizophrenia, via neuregulin 1; thus, the ability of M 1 activation to regulate BACE1 suggests that pharmacological agents that can selectivity activate M 1 represent a nove...

Myeloid cell leukemia 1 (Mcl-1), an antiapoptotic member of the Bcl-2 family of proteins, has emerged as an attractive target for cancer therapy. Mcl-1 upregulation is often found in many human cancers and is associated with high tumor grade, poor survival, and resistance to chemotherapy. Here, we describe a series of potent and selective tricyclic indole diazepinone Mcl-1 inhibitors that were discovered and further optimized using structure-based design. These compounds exhibit picomolar binding affinity and mechanism-based cellular efficacy, including growth inhibition and caspase induction in Mcl-1-sensitive cells. Thus, they represent useful compounds to study the implication of Mcl-1 inhibition in cancer and serve as potentially useful starting points toward the discovery of anti-Mcl-1 therapeutics.