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.

Selective estrogen receptor degraders (SERDs) and covalent antagonists (SERCAs): a patent review (July 2021-December 2023).

INTRODUCTION: Breast cancer is the most frequently diagnosed cancer worldwide. With around 70% of breast cancers expressing the estrogen receptor (ER), molecules capable of antagonizing and degrading ER (SERDs) or covalently binding to and antagonizing ER (SERCAs) are at the forefront of efforts to bring better treatments to patients. AREAS COVERED: This review summarizes patent applications that claim estrogen receptor degraders (SERDs) and covalent antagonists (SERCAs) identified using SciFinder between the period July 2021 to December 2023. A total of 91 new patent applications from 32 different applicants are evaluated with stratification into acidic SERDs, basic SERDs, SERCAs and miscellaneous degraders. EXPERT OPINION: The widespread adoption of fulvestrant in the treatment of ER+ breast cancer continues to stimulate research into orally bioavailable SERDs and SERCAs. A number of molecules have entered clinical development and, although some have been discontinued, a cohort of potential new treatments have generated encouraging efficacy and safety data. Notably, the first example of an oral SERD, elacestrant, has now been approved by the FDA and EMA, providing further encouragement for this class of targeted therapies.

Metabolism-driven in vitro/in vivo disconnect of an oral ERɑ VHL-PROTAC.

Targeting the estrogen receptor alpha (ERα) pathway is validated in the clinic as an effective means to treat ER+ breast cancers. Here we present the development of a VHL-targeting and orally bioavailable proteolysis-targeting chimera (PROTAC) degrader of ERα. In vitro studies with this PROTAC demonstrate excellent ERα degradation and ER antagonism in ER+ breast cancer cell lines. However, upon dosing the compound in vivo we observe an in vitro-in vivo disconnect. ERα degradation is lower in vivo than expected based on the in vitro data. Investigation into potential causes for the reduced maximal degradation reveals that metabolic instability of the PROTAC linker generates metabolites that compete for binding to ERα with the full PROTAC, limiting degradation. This observation highlights the requirement for metabolically stable PROTACs to ensure maximal efficacy and thus optimisation of the linker should be a key consideration when designing PROTACs.

Development of a Series of Pyrrolopyridone MAT2A Inhibitors.

The optimization of an allosteric fragment, discovered by differential scanning fluorimetry, to an in vivo MAT2a tool inhibitor is discussed. The structure-based drug discovery approach, aided by relative binding free energy calculations, resulted in AZ'9567 (21), a potent inhibitor in vitro with excellent preclinical pharmacokinetic properties. This tool showed a selective antiproliferative effect on methylthioadenosine phosphorylase (MTAP) KO cells, both in vitro and in vivo, providing further evidence to support the utility of MAT2a inhibitors as potential anticancer therapies for MTAP-deficient tumors.

The Next-Generation Oral Selective Estrogen Receptor Degrader Camizestrant (AZD9833) Suppresses ER+ Breast Cancer Growth and Overcomes Endocrine and CDK4/6 Inhibitor Resistance.

Oral selective estrogen receptor degraders (SERD) could become the backbone of endocrine therapy (ET) for estrogen receptor-positive (ER+) breast cancer, as they achieve greater inhibition of ER-driven cancers than current ETs and overcome key resistance mechanisms. In this study, we evaluated the preclinical pharmacology and efficacy of the next-generation oral SERD camizestrant (AZD9833) and assessed ER-co-targeting strategies by combining camizestrant with CDK4/6 inhibitors (CDK4/6i) and PI3K/AKT/mTOR-targeted therapy in models of progression on CDK4/6i and/or ET. Camizestrant demonstrated robust and selective ER degradation, modulated ER-regulated gene expression, and induced complete ER antagonism and significant antiproliferation activity in ESR1 wild-type (ESR1wt) and mutant (ESR1m) breast cancer cell lines and patient-derived xenograft (PDX) models. Camizestrant also delivered strong antitumor activity in fulvestrant-resistant ESR1wt and ESR1m PDX models. Evaluation of camizestrant in combination with CDK4/6i (palbociclib or abemaciclib) in CDK4/6-naive and -resistant models, as well as in combination with PI3Kαi (alpelisib), mTORi (everolimus), or AKTi (capivasertib), indicated that camizestrant was active with CDK4/6i or PI3K/AKT/mTORi and that antitumor activity was further increased by the triple combination. The response was observed independently of PI3K pathway mutation status. Overall, camizestrant shows strong and broad antitumor activity in ER+ breast cancer as a monotherapy and when combined with CDK4/6i and PI3K/AKT/mTORi. SIGNIFICANCE: Camizestrant, a next-generation oral SERD, shows promise in preclinical models of ER+ breast cancer alone and in combination with CDK4/6 and PI3K/AKT/mTOR inhibitors to address endocrine resistance, a current barrier to treatment.

Discovery of a Potent and Orally Bioavailable Zwitterionic Series of Selective Estrogen Receptor Degrader-Antagonists.

Herein, we report the optimization of a meta-substituted series of selective estrogen receptor degrader (SERD) antagonists for the treatment of ER+ breast cancer. Structure-based design together with the use of modeling and NMR to favor the bioactive conformation led to a highly potent series of basic SERDs with promising physicochemical properties. Issues with hERG activity resulted in a strategy of zwitterion formation and ultimately in the identification of 38. This compound was shown to be a highly potent SERD capable of effectively degrading ERα in both MCF-7 and CAMA-1 cell lines. The low lipophilicity and zwitterionic nature led to a SERD with a clean secondary pharmacology profile and no hERG activity. Favorable physicochemical properties resulted in good oral bioavailability in preclinical species and potent in vivo activity in a mouse xenograft model.

Virtual Screening in the Cloud Identifies Potent and Selective ROS1 Kinase Inhibitors.

ROS1 rearrangements account for 1-2% of non-small cell lung cancer patients, yet there are no specifically designed, selective ROS1 therapies in the clinic. Previous knowledge of potent ROS1 inhibitors with selectivity over TrkA, a selected antitarget, enabled virtual screening as a hit finding approach in this project. The ligand-based virtual screening was focused on identifying molecules with a similar 3D shape and pharmacophore to the known actives. To that end, we turned to the AstraZeneca virtual library, estimated to cover 1015 synthesizable make-on-demand molecules. We used cloud computing-enabled FastROCS technology to search the enumerated 1010 subset of the full virtual space. A small number of specific libraries were prioritized based on the compound properties and a medicinal chemistry assessment and further enumerated with available building blocks. Following the docking evaluation to the ROS1 structure, the most promising hits were synthesized and tested, resulting in the identification of several potent and selective series. The best among them gave a nanomolar ROS1 inhibitor with over 1000-fold selectivity over TrkA and, from the preliminary established SAR, these have the potential to be further optimized. Our prospective study describes how conceptually simple shape-matching approaches can identify potent and selective compounds by searching ultralarge virtual libraries, demonstrating the applicability of such workflows and their importance in early drug discovery.

A patent review of MAT2a inhibitors (2018-2021).

INTRODUCTION: In methylthioadenosine phosphorylase (MTAP)-deficient tumor cells, reduced S-adenosylmethionine (SAM) levels in the context of elevated methylthioadenosine (MTA) has been hypothesized to lead to inhibition of protein arginine methyltransferase 5 (PRMT5) and tumor growth inhibition. Inhibitors of methionine adenosyltransferase 2A (MAT2a) prevent the synthesis of SAM from methionine and have therefore attracted increasing attention as potential chemotherapeutic agents in cancers characterized by MTAP-loss. AREAS COVERED: This review covers patent applications between January 2018 and December 2021. 18 patent applications from 5 different applicants are evaluated. EXPERT OPINION: Recent advances in the field show a significant interest in the MAT2a therapeutic hypothesis. Agios and Ideaya in particular have capitalized on an allosteric binding mode first published by Pfizer in at least two of the filings during this time period, leading to potent, selective inhibitors. They have advanced MAT2a inhibitors to phase I clinical studies to explore their benefit to patients suffering with MTAP-deficient solid tumors or lymphoma. Whilst the other patent disclosures during this time frame have not led to disclosed candidates, the trials initiated by Agios and Ideaya studies will clearly inform on the potential for such inhibitors as viable therapeutic agents either as single agent or in combination.

Identification and optimisation of a pyrimidopyridone series of IRAK4 inhibitors.

In this article, we report the discovery of a series of pyrimidopyridones as inhibitors of IRAK4 kinase. From a previously disclosed 5-azaquinazoline series, we found that switching the pyridine ring for an N-substituted pyridone gave a novel hinge binding scaffold which retained potency against IRAK4. Importantly, introduction of the carbonyl established an internal hydrogen bond with the 4-NH, establishing a conformational lock and allowing truncation of the large basic substituent to a 1-methylcyclopyl group. Subsequent optimisation, facilitated by X-ray crystal structures, allowed identification of preferred substituents at both the pyridone core and pyrazole. Subsequent combinations of optimal groups allowed control of lipophilicity and identification of potent and selective inhibitors of IRAK4 with better in vitro permeability and lower clearance.

Selective estrogen receptor degraders (SERDs) and covalent antagonists (SERCAs): a patent review (2015-present).

INTRODUCTION: The estrogen receptor (ER) is a clinically validated oncology target with a pivotal role in hormonally driven breast cancer, the most prevalent form of female cancer. Current treatments that directly modulate ER include antagonists (SERMs), such as tamoxifen, and degraders (SERDs), such as fulvestrant which is administered by intramuscular injection. AREAS COVERED: This review covers patent applications that claim estrogen receptor degraders (SERDs) and covalent antagonists (SERCAs) between the period January 2015 to June 2021. A total of 114 patent applications from 23 different applicants are evaluated with stratification into acidic SERDs, basic SERDs, and SERCAs. EXPERT OPINION: The clinical success of fulvestrant in the treatment of ER+ breast cancer has spurred research over the last decade into the discovery and development of novel SERDs, with a particular focus on the discovery of orally bioavailable drugs. This has resulted in a diverse range of candidates entering clinical trials. Although some have faltered in development, a cohort of oral SERDs has generated encouraging efficacy and safety data that has allowed advancement into late stage clinical trials. Data from these trials is eagerly awaited, with these molecules having the potential to offer significant benefits in the treatment of ER+ breast cancer.

Relating Conformational Equilibria to Conformer-Specific Lipophilicities: New Opportunities in Drug Discovery.

Efficient drug discovery is based on a concerted effort in optimizing bioactivity and compound properties such as lipophilicity, and is guided by efficiency metrics that reflect both aspects. While conformation-activity relationships and ligand conformational control are known strategies to improve bioactivity, the use of conformer-specific lipophilicities (logp) is much less explored. Here we show how conformer-specific logp values can be obtained from knowledge of the macroscopic logP value, and of the equilibrium constants between the individual species in water and in octanol. This is illustrated with fluorinated amide rotamers, with integration of rotamer 19 F NMR signals as a facile, direct method to obtain logp values. The difference between logp and logP optimization is highlighted, giving rise to a novel avenue for lipophilicity control in drug discovery.

Fragment-Based Design of a Potent MAT2a Inhibitor and in Vivo Evaluation in an MTAP Null Xenograft Model.

MAT2a is a methionine adenosyltransferase that synthesizes the essential metabolite S-adenosylmethionine (SAM) from methionine and ATP. Tumors bearing the co-deletion of p16 and MTAP genes have been shown to be sensitive to MAT2a inhibition, making it an attractive target for treatment of MTAP-deleted cancers. A fragment-based lead generation campaign identified weak but efficient hits binding in a known allosteric site. By use of structure-guided design and systematic SAR exploration, the hits were elaborated through a merging and growing strategy into an arylquinazolinone series of potent MAT2a inhibitors. The selected in vivo tool compound 28 reduced SAM-dependent methylation events in cells and inhibited proliferation of MTAP-null cells in vitro. In vivo studies showed that 28 was able to induce antitumor response in an MTAP knockout HCT116 xenograft model.

Skipped Fluorination Motifs: Synthesis of Building Blocks and Comparison of Lipophilicity Trends with Vicinal and Isolated Fluorination Motifs.

Given there is an optimal lipophilicity range for orally bioavailable drugs, structural modifications applied in the drug development process are not only focused on optimizing bioactivity but also on fine-tuning lipophilicity. Fluorine introduction can be used for both purposes. Insights into how fluorine introduction affects lipophilicity are thus of importance, and systematic series of fluorinated compounds with measured octanol-water partition coefficients are a powerful way to enhance our qualitative understanding in this regard and are essential as input for computational log P estimation programs. Here, we report a detailed comparison of all possible vicinal and skipped (1,3-substituted) fluorination motifs when embedded in structurally equivalent environments (X-CFnH2-n-CFmH2-m-X versus X-CFnH2-n-CH2-CFmH2-m-X, with n,m ≠ 0 and X = CH2OH) to compounds with isolated fluorination (n ≠ 0; m = 0, and including X-CH2-CFnH2-n-CH2-X, n = 0-2). It is shown that skipped fluorination is more powerful for log P reduction purposes compared to single or vicinal fluorination. Efficient stereoselective syntheses of the compounds with skipped fluorination motifs are reported, which where relevant can be made enantioselective using known chiral building blocks. These compounds, and some intermediates, will be of interest as advanced fluorinated building blocks.

Addition of Fluorine and a Late-Stage Functionalization (LSF) of the Oral SERD AZD9833.

Herein we describe our efforts using a late stage functionalization together with more traditional synthetic approaches to generate fluorinated analogues of the clinical candidate AZD9833. The effects of the addition of fluorine on the lipophilicity, permeability, and metabolism are discussed. Many of these changes were tolerated in terms of pharmacology and resulted in high quality molecules which reached advanced stages of profiling in the testing cascade.

Improving metabolic stability and removing aldehyde oxidase liability in a 5-azaquinazoline series of IRAK4 inhibitors.

In this article, we report our efforts towards improving in vitro human clearance in a series of 5-azaquinazolines through a series of C4 truncations and C2 expansions. Extensive DMPK studies enabled us to tackle high Aldehyde Oxidase (AO) metabolism and unexpected discrepancies in human hepatocyte and liver microsomal intrinsic clearance. Our efforts culminated with the discovery of 5-azaquinazoline 35, which also displayed exquisite selectivity for IRAK4, and showed synergistic in vitro activity against MyD88/CD79 double mutant ABC-DLBCL in combination with the covalent BTK inhibitor acalabrutinib.

Discovery of AZD9833, a Potent and Orally Bioavailable Selective Estrogen Receptor Degrader and Antagonist.

Herein we report the optimization of a series of tricyclic indazoles as selective estrogen receptor degraders (SERD) and antagonists for the treatment of ER+ breast cancer. Structure based design together with systematic investigation of each region of the molecular architecture led to the identification of N-[1-(3-fluoropropyl)azetidin-3-yl]-6-[(6S,8R)-8-methyl-7-(2,2,2-trifluoroethyl)-6,7,8,9-tetrahydro-3H-pyrazolo[4,3-f]isoquinolin-6-yl]pyridin-3-amine (28). This compound was demonstrated to be a highly potent SERD that showed a pharmacological profile comparable to fulvestrant in its ability to degrade ERα in both MCF-7 and CAMA-1 cell lines. A stringent control of lipophilicity ensured that 28 had favorable physicochemical and preclinical pharmacokinetic properties for oral administration. This, combined with demonstration of potent in vivo activity in mouse xenograft models, resulted in progression of this compound, also known as AZD9833, into clinical trials.

Lipophilicity trends upon fluorination of isopropyl, cyclopropyl and 3-oxetanyl groups.

A systematic comparison of lipophilicity modulations upon fluorination of isopropyl, cyclopropyl and 3-oxetanyl substituents, at a single carbon atom, is provided using directly comparable, and easily accessible model compounds. In addition, comparison with relevant linear chain derivatives is provided, as well as lipophilicity changes occurring upon chain extension of acyclic precursors to give cyclopropyl containing compounds. For the compounds investigated, fluorination of the isopropyl substituent led to larger lipophilicity modulation compared to fluorination of the cyclopropyl substituent.

A Buchwald-Hartwig Protocol to Enable Rapid Linker Exploration of Cereblon E3-Ligase PROTACs*.

A palladium-catalysed Buchwald-Hartwig amination for lenalidomide-derived aryl bromides was optimised using high throughput experimentation (HTE). The substrate scope of the optimised conditions was evaluated for a range of alkyl- and aryl- amines and functionalised aryl bromides. The methodology allows access to new cereblon-based bifunctional proteolysis targeting chimeras with a reduced step count and improved yields.

Structure-Guided Design and In-Cell Target Profiling of a Cell-Active Target Engagement Probe for PARP Inhibitors.

Inhibition of the poly(ADP-ribose) polymerase (PARP) family of enzymes has become an attractive therapeutic strategy in oncology and beyond; however, chemical tools to profile PARP engagement in live cells are lacking. Herein, we report the design and application of PARPYnD, the first photoaffinity probe (AfBP) for PARP enzymes based on triple PARP1/2/6 inhibitor AZ9482, which induces multipolar spindle (MPS) formation in breast cancer cells. PARPYnD is a robust tool for profiling PARP1/2 and is used to profile clinical PARP inhibitor olaparib, identifying several novel off-target proteins. Surprisingly, while PARPYnD can enrich recombinant PARP6 spiked into cellular lysates and inhibits PARP6 in cell-free assays, it does not label PARP6 in intact cells. These data highlight an intriguing biomolecular disparity between recombinant and endogenous PARP6. PARPYnD provides a new approach to expand our knowledge of the targets of this class of compounds and the mechanisms of action of PARP inhibitors in cancer.

Systematic Investigation of Lipophilicity Modulation by Aliphatic Fluorination Motifs.

Optimization of compound lipophilicity is a key aspect of drug discovery. The aim of this work was to compare the lipophilicity modulations induced by 16 distinct known and novel fluoroalkyl motifs on three parent models. Fifty fluorinated compounds, with 28 novel experimental aliphatic log P values, are involved in discussing various lipophilicity trends. As well as confirming known trends, a number of novel lipophilicity-reducing motifs are introduced. Tactics to reduce lipophilicity are discussed, such as "motif extensions" and "motif rearrangements", including with concomitant extension of the carbon chain, as well as one- and two-fluorine 'deletions' within perfluoroalkyl groups. Quantum chemical log P calculations (SMD-MN15) based on solvent-dependent three-dimensional (3D) conformational analysis gave excellent correlations with experimental values, superior to Clog P predictions based on 2D structural motifs. The availability of a systematic collection of data based on a small number of parent molecules illustrates the relative lipophilicity modulations of aliphatic fluorination motifs.