Discovery of a Series of Orally Bioavailable Androgen Receptor Degraders for the Treatment of Prostate Cancer.

Androgen receptor (AR) signaling plays a key role in the progression of prostate cancer. This study describes the discovery and optimization of a novel series of AR PROTAC degraders that recruit the Cereblon (CRBN) E3 ligase. Having identified a series of AR ligands based on 4-(4-phenyl-1-piperidyl)-2-(trifluoromethyl)benzonitrile, our PROTAC optimization strategy focused on linker connectivity and CRBN ligand SAR to deliver potent degradation of AR in LNCaP cells. This work culminated in compounds 11 and 16 which demonstrated good rodent oral bioavailability. Subsequent SAR around the AR binding region brought in an additional desirable feature, degradation of the important treatment resistance mutation L702H. Compound 22 (AZ'3137) possessed an attractive profile showing degradation of AR and L702H mutant AR with good oral bioavailability across species. The compound also inhibited AR signaling in vitro and tumor growth in vivo in a mouse prostate cancer xenograft model.

Identification of Novel Potent NSD2-PWWP1 Ligands Using Structure-Based Design and Computational Approaches.

Dysregulation of histone methyl transferase nuclear receptor-binding SET domain 2 (NSD2) has been implicated in several hematological and solid malignancies. NSD2 is a large multidomain protein that carries histone writing and histone reading functions. To date, identifying inhibitors of the enzymatic activity of NSD2 has proven challenging in terms of potency and SET domain selectivity. Inhibition of the NSD2-PWWP1 domain using small molecules has been considered as an alternative approach to reduce NSD2-unregulated activity. In this article, we present novel computational chemistry approaches, encompassing free energy perturbation coupled to machine learning (FEP/ML) models as well as virtual screening (VS) activities, to identify high-affinity NSD2 PWWP1 binders. Through these activities, we have identified the most potent NSD2-PWWP1 binder reported so far in the literature: compound 34 (pIC50 = 8.2). The compounds identified herein represent useful tools for studying the role of PWWP1 domains for inhibition of human NSD2.

The SAR development of substituted purine derivatives as selective CB2 agonists for the treatment of chronic pain.

Osteoarthritis (OA) and the associated joint pain are highly prevalent and a leading cause of disability. We have previously reported the identification of a series of purines as selective CB2 agonists and the identification of compound 1 as a clinical candidate for the treatment of joint pain. In this article we describe the further SAR development of the purine scaffold leading to the discovery of compound 6 as a potent, CNS penetrating CB2 agonist with high selectivity for CB2 over CB1 and oral efficacy in animal models of chronic OA pain.

Unique pharmacology of heteromeric α7ß2 nicotinic acetylcholine receptors expressed in Xenopus laevis oocytes.

α7ß2 is a novel type of nicotinic acetylcholine receptor shown to be uniquely expressed in cholinergic neurons of the basal forebrain and in hippocampal interneurons. We have compared the pharmacological properties of recombinant homomeric α7 and heteromeric α7ß2 nicotinic acetylcholine receptors in order to reveal the pharmacological consequences of ß2 subunit incorporation into the pentamer. The non-selective agonist epibatidine did not distinguish α7ß2 from α7 nicotinic acetylcholine receptors, but three other non-selective agonists (nicotine, cytisine and varenicline) were less efficacious on α7ß2 than on α7. A more dramatic change in efficacy was seen with eight different selective α7 agonists. Because of their very low intrinsic efficacy, some compounds became very efficacious functional antagonists at α7ß2 receptors. Three α4ß2 nicotinic receptor selective agonists that were not active on α7, were also inactive on α7ß2, and dihydro-ß-erythroidine, an α4ß2 receptor-preferring antagonist, inhibited α7 and α7ß2 in a similar manner. These results reveal significant effects of ß2 incorporation in determining the relative efficacy of several non-selective and α7 selective agonists, and also show that incorporation of ß2 subunits does not cause a shift to a more "ß2-like" pharmacology of α7 nicotinic acetylcholine receptors.

Selective cannabinoid receptor type 2 (CB2) agonists: optimization of a series of purines leading to the identification of a clinical candidate for the treatment of osteoarthritic pain.

A focused screening strategy identified thienopyrimidine 12 as a cannabinoid receptor type 2 agonist (hCB2) with moderate selectivity over the hCB1 receptor. This initial hit suffered from poor in vitro metabolic stability and high in vivo clearance. Structure-activity relationships describe the optimization and modification to a new more polar series of purine CB2 agonists. Examples from this novel scaffold were found to be highly potent and fully efficacious agonists of the human CB2 receptor with excellent selectivity against CB1, often having no CB1 agonist activity at the highest concentration measured (>100 µM). Compound 26 is a centrally penetrant molecule which possesses good biopharmaceutical properties, is highly water-soluble, and demonstrates robust oral activity in rodent models of joint pain. In addition, the peripherally restricted molecule 22 also demonstrated significant efficacy in the same analgesic model of rodent inflammatory pain.

Discovery and optimization of novel purines as potent and selective CB2 agonists.

A focused screening strategy identified thienopyrimidine 1 as a hCB2 cannabinoid receptor agonist with moderate selectivity over the hCB1 receptor. This initial hit suffered from poor in vitro metabolic stability and high in vivo clearance. Structure-activity relationships describe the optimization and modification to a less lipophilic purine core. Examples from this novel series were found to be highly potent and fully efficacious agonists of the human CB2 receptor with excellent selectivity against CB1. Compound 10 possesses good biopharmaceutical properties, is highly water soluble and demonstrates robust oral activity in rodent models of joint pain.

Total synthesis of (+/-)-alpha-isosparteine, (+/-)-beta-isosparteine, and (+/-)-sparteine from a common tetraoxobispidine intermediate.

The three title alkaloids were separately prepared in stereocontrolled fashion from a common tetraoxobispidine precursor, 3,7-diallyl-2,4,6,8-tetraoxo-3,7-diazabicyclo[3.3.1]nonane (16). Bisimide 16 was generated from malonate via acid promoted cyclization of the Knoevenagel condensation adduct 1,1,3,3-propanetetracarboxamide. (+/-)-alpha-Isosparteine (dl-2) was elaborated from 16 in 28% overall yield by a two-directional synthetic sequence composed of four reactions: double addition of allylmagnesium bromide, ring-closing olefin metathesis (RCM), hydrogenation, and borane mediated reduction. (+/-)-beta-Isosparteine (dl-3) was targeted along similar lines by a strategic reversal in allylation and reduction operations on the core synthon. Thus, 16 was advanced to dl-3 in five steps and 12% overall yield by a reaction sequence commencing with sodium borohydride mediated reduction and followed by double Sakurai-type allylation of the resulting bishemiaminal. The synthesis of dl-3 was concluded by RCM and then global reduction (H2, Pd/C; LiAlH4). The final target, (+/-)-sparteine (dl-1), was secured in six steps and 11% overall yield from 16 by monoreduction and Sakurai allylation, followed by allyl Grignard addition and then RCM and global reduction as before. Reasons for the inherent C2-type regioselectivity of net double nucleophilic additions to tetraoxobispidines are discussed and enantioselective oxazaborolidine mediated reduction of the N,N'-dibenzyl congener of 16 is reported.

Species selectivity of a nicotinic acetylcholine receptor agonist is conferred by two adjacent extracellular beta4 amino acids that are implicated in the coupling of binding to channel gating.

5-(Trifluoromethyl)-6-(1-methyl-azepan-4-yl)methyl-1H-quinolin-2-one (TMAQ) is a novel nicotinic acetylcholine receptor (nAChR) agonist with strong selectivity for beta4-containing receptors. TMAQ also exhibits remarkable species selectivity, being a potent agonist of nAChRs containing the human beta4 subunit but having no detectable agonist activity on nAChRs containing the rat beta4 subunit. With the aim of identifying subunit domains and individual amino acids, which contribute to the species selectivity of TMAQ, a series of chimeric and mutated beta4 subunits has been constructed. Recombinant receptors containing wild-type, chimeric, or mutated beta4 subunits have been examined by radioligand binding, intracellular calcium assays, and electrophysiological recording. Two adjacent amino acids located within the extracellular loop D domain of the beta4 subunit (amino acids 55 and 56) have been identified as playing a critical role in determining the agonist potency of TMAQ. Mutagenesis of these two residues within the rat beta4 subunit to the corresponding amino acids in the human beta4 subunit (S55N and I56V mutations) confers sensitivity to TMAQ. The converse mutations in the human beta4 subunit (N55S and V56I) largely abolish sensitivity to TMAQ. In contrast, these mutations have little or no effect on sensitivity to the nonselective nicotinic agonist epibatidine. Despite acting as a potent agonist of human beta4-containing nAChRs, TMAQ acts as an antagonist of rat beta4-containing receptors. Our experimental data, together with homology models of the rat and human alpha3beta4 nAChRs, suggest that amino acids 55 and 56 may be involved in the coupling of agonist binding and channel gating.

A practical synthesis of (+/-)-alpha-isosparteine from a tetraoxobispidine core.

[reaction: see text] The title alkaloid was synthesized in racemic form from 3,7-diallyl-2,4,6,8-tetraoxo-3,7-diazabicyclo[3.3.1]nonane (7) by a regioselective diallylation reaction followed by double ring-closing olefin metathesis and exhaustive reduction. Tetraoxobispidine 7 was itself prepared in three simple operations from dimethyl malonate. The entire sequence to alpha-isosparteine was conducted on a multigram scale and proceeded without recourse to chromatography.