Discovery and Preclinical Pharmacology of NX-2127, an Orally Bioavailable Degrader of Bruton's Tyrosine Kinase with Immunomodulatory Activity for the Treatment of Patients with B Cell Malignancies.

Bruton's tyrosine kinase (BTK), a member of the TEC family of kinases, is an essential effector of B-cell receptor (BCR) signaling. Chronic activation of BTK-mediated BCR signaling is a hallmark of many hematological malignancies, which makes it an attractive therapeutic target. Pharmacological inhibition of BTK enzymatic function is now a well-proven strategy for the treatment of patients with these malignancies. We report the discovery and characterization of NX-2127, a BTK degrader with concomitant immunomodulatory activity. By design, NX-2127 mediates the degradation of transcription factors IKZF1 and IKZF3 through molecular glue interactions with the cereblon E3 ubiquitin ligase complex. NX-2127 degrades common BTK resistance mutants, including BTKC481S. NX-2127 is orally bioavailable, exhibits in vivo degradation across species, and demonstrates efficacy in preclinical oncology models. NX-2127 has advanced into first-in-human clinical trials and achieves deep and sustained degradation of BTK following daily oral dosing at 100 mg.

NRX-0492 degrades wild-type and C481 mutant BTK and demonstrates in vivo activity in CLL patient-derived xenografts.

Bruton tyrosine kinase (BTK) is essential for B-cell receptor (BCR) signaling, a driver of chronic lymphocytic leukemia (CLL). Covalent inhibitors bind C481 in the active site of BTK and have become a preferred CLL therapy. Disease progression on covalent BTK inhibitors is commonly associated with C481 mutations. Here, we investigated a targeted protein degrader, NRX-0492, that links a noncovalent BTK-binding domain to cereblon, an adaptor protein of the E3 ubiquitin ligase complex. NRX-0492 selectively catalyzes ubiquitylation and proteasomal degradation of BTK. In primary CLL cells, NRX-0492 induced rapid and sustained degradation of both wild-type and C481 mutant BTK at half maximal degradation concentration (DC50) of ≤0.2 nM and DC90 of ≤0.5 nM, respectively. Sustained degrader activity was maintained for at least 24 hours after washout and was equally observed in high-risk (deletion 17p) and standard-risk (deletion 13q only) CLL subtypes. In in vitro testing against treatment-naïve CLL samples, NRX-0492 was as effective as ibrutinib at inhibiting BCR-mediated signaling, transcriptional programs, and chemokine secretion. In patient-derived xenografts, orally administered NRX-0492 induced BTK degradation and inhibited activation and proliferation of CLL cells in blood and spleen and remained efficacious against primary C481S mutant CLL cells collected from a patient progressing on ibrutinib. Oral bioavailability, >90% degradation of BTK at subnanomolar concentrations, and sustained pharmacodynamic effects after drug clearance make this class of targeted protein degraders uniquely suitable for clinical translation, in particular as a strategy to overcome BTK inhibitor resistance. Clinical studies testing this approach have been initiated (NCT04830137, NCT05131022).

Dual antagonists of α5ß1/αvß1 integrin for airway hyperresponsiveness.

Inhibition of integrin α5ß1 emerges as a novel therapeutic option to block transmission of contractile forces during asthma attack. We designed and synthesized novel inhibitors of integrin α5ß1 by backbone replacement of known αvß1 integrin inhibitors. These integrin α5ß1 inhibitors also retain the nanomolar potency against αvß1 integrin, which shows promise for developing dual integrin α5ß1/αvß1 inhibitor. Introduction of hydrophobic adamantane group significantly boosted the potency as well as selectivity over integrin αvß3. We also demonstrated one of the inhibitors (11) reduced airway hyperresponsiveness in ex vivo mouse tracheal ring assay. Results from this study will help guide further development of integrin α5ß1 inhibitors as potential novel asthma therapeutics.

Exploring N-Arylsulfonyl-l-proline Scaffold as a Platform for Potent and Selective αvß1 Integrin Inhibitors.

One small molecule inhibitor of αvß1 integrin, c8, shows antifibrotic effects in multiple in vivo mouse models. Here we synthesized c8 analogues and systematically investigate their structure-activity relationships (SAR) in αvß1 integrin inhibition. N-Phenylsulfonyl-l-homoproline analogues of c8 maintained excellent potency against αvß1 integrin while retaining good selectivity over other RGD integrins. In addition, 2-aminopyridine or cyclic guanidine analogues were shown to be equally potent to c8. A rigid phenyl linker increased the potency compared to c8, but the selectivity over other RGD integrins diminished. These results can provide further insights on design of αvß1 integrin inhibitors as antifibrotics.

Finding the perfect spot for fluorine: improving potency up to 40-fold during a rational fluorine scan of a Bruton's Tyrosine Kinase (BTK) inhibitor scaffold.

A rational fluorine scan based on co-crystal structures was explored to increase the potency of a series of selective BTK inhibitors. While fluorine substitution on a saturated bicyclic ring system yields no apparent benefit, the same operation on an unsaturated bicyclic ring can increase HWB activity by up to 40-fold. Comparison of co-crystal structures of parent molecules and fluorinated counterparts revealed the importance of placing fluorine at the optimal position to achieve favorable interactions with protein side chains.

Structure-based drug design of RN486, a potent and selective Bruton's tyrosine kinase (BTK) inhibitor, for the treatment of rheumatoid arthritis.

Structure-based drug design was used to guide the optimization of a series of selective BTK inhibitors as potential treatments for Rheumatoid arthritis. Highlights include the introduction of a benzyl alcohol group and a fluorine substitution, each of which resulted in over 10-fold increase in activity. Concurrent optimization of drug-like properties led to compound 1 (RN486) ( J. Pharmacol. Exp. Ther. 2012 , 341 , 90 ), which was selected for advanced preclinical characterization based on its favorable properties.

Discovery of AM-7209, a potent and selective 4-amidobenzoic acid inhibitor of the MDM2-p53 interaction.

Structure-based rational design and extensive structure-activity relationship studies led to the discovery of AMG 232 (1), a potent piperidinone inhibitor of the MDM2-p53 association, which is currently being evaluated in human clinical trials for the treatment of cancer. Further modifications of 1, including replacing the carboxylic acid with a 4-amidobenzoic acid, afforded AM-7209 (25), featuring improved potency (KD from ITC competition was 38 pM, SJSA-1 EdU IC50 = 1.6 nM), remarkable pharmacokinetic properties, and in vivo antitumor activity in both the SJSA-1 osteosarcoma xenograft model (ED50 = 2.6 mg/kg QD) and the HCT-116 colorectal carcinoma xenograft model (ED50 = 10 mg/kg QD). In addition, 25 possesses distinct mechanisms of elimination compared to 1.

Novel inhibitors of the MDM2-p53 interaction featuring hydrogen bond acceptors as carboxylic acid isosteres.

We previously reported the discovery of potent and selective morpholinone and piperidinone inhibitors of the MDM2-p53 interaction. These inhibitors have in common a carboxylic acid moiety that engages in an electrostatic interaction with MDM2-His96. Our continued search for potent and diverse inhibitors led to the discovery of novel replacements for these acids uncovering new interactions with the MDM2 protein. In particular, using pyridine or thiazole as isosteres of the carboxylic acid moiety resulted in very potent analogues. From these, AM-6761 (4) emerged as a potent inhibitor with remarkable biochemical (HTRF IC50 = 0.1 nM) and cellular potency (SJSA-1 EdU IC50 = 16 nM), as well as favorable pharmacokinetic properties. Compound 4 also shows excellent antitumor activity in the SJSA-1 osteosarcoma xenograft model with an ED50 of 11 mg/kg. Optimization efforts toward the discovery of these inhibitors as well as the new interactions observed with the MDM2 protein are described herein.

Selective and potent morpholinone inhibitors of the MDM2-p53 protein-protein interaction.

We previously reported the discovery of AMG 232, a highly potent and selective piperidinone inhibitor of the MDM2-p53 interaction. Our continued search for potent and diverse analogues led to the discovery of novel morpholinone MDM2 inhibitors. This change to a morpholinone core has a significant impact on both potency and metabolic stability compared to the piperidinone series. Within this morpholinone series, AM-8735 emerged as an inhibitor with remarkable biochemical potency (HTRF IC50 = 0.4 nM) and cellular potency (SJSA-1 EdU IC50 = 25 nM), as well as pharmacokinetic properties. Compound 4 also shows excellent antitumor activity in the SJSA-1 osteosarcoma xenograft model with an ED50 of 41 mg/kg. Lead optimization toward the discovery of this inhibitor as well as key differences between the morpholinone and the piperidinone series will be described herein.

Discovery of AMG 232, a potent, selective, and orally bioavailable MDM2-p53 inhibitor in clinical development.

We recently reported the discovery of AM-8553 (1), a potent and selective piperidinone inhibitor of the MDM2-p53 interaction. Continued research investigation of the N-alkyl substituent of this series, focused in particular on a previously underutilized interaction in a shallow cleft on the MDM2 surface, led to the discovery of a one-carbon tethered sulfone which gave rise to substantial improvements in biochemical and cellular potency. Further investigation produced AMG 232 (2), which is currently being evaluated in human clinical trials for the treatment of cancer. Compound 2 is an extremely potent MDM2 inhibitor (SPR KD = 0.045 nM, SJSA-1 EdU IC50 = 9.1 nM), with remarkable pharmacokinetic properties and in vivo antitumor activity in the SJSA-1 osteosarcoma xenograft model (ED50 = 9.1 mg/kg).

Discovery of N-[4-[6-tert-butyl-5-methoxy-8-(6-methoxy-2-oxo-1H-pyridin-3-yl)-3-quinolyl]phenyl]methanesulfonamide (RG7109), a potent inhibitor of the hepatitis C virus NS5B polymerase.

In the past few years, there have been many advances in the efforts to cure patients with hepatitis C virus (HCV). The ultimate goal of these efforts is to develop a combination therapy consisting of only direct-antiviral agents (DAAs). In this paper, we discuss our efforts that led to the identification of a bicyclic template with potent activity against the NS5B polymerase, a critical enzyme on the life cycle of HCV. In continuation of our exploration to improve the stilbene series, the 3,5,6,8-tetrasubstituted quinoline core was identified as replacement of the stilbene moiety. 6-Methoxy-2(1H)-pyridone was identified among several heterocyclic headgroups to have the best potency. Solubility of the template was improved by replacing a planar aryl linker with a saturated pyrrolidine. Profiling of the most promising compounds led to the identification of quinoline 41 (RG7109), which was selected for advancement to clinical development.

3-Amino-pyrazolo[3,4-d]pyrimidines as p38α kinase inhibitors: design and development to a highly selective lead.

Learnings from previous Roche p38-selective inhibitors were applied to a new fragment hit, which was optimized to a potent, exquisitely selective preclinical lead with a good pharmacokinetic profile.

Discovery of 6-(2,4-difluorophenoxy)-2-[3-hydroxy-1-(2-hydroxyethyl)propylamino]-8-methyl-8H-pyrido[2,3-d]pyrimidin-7-one (pamapimod) and 6-(2,4-difluorophenoxy)-8-methyl-2-(tetrahydro-2H-pyran-4-ylamino)pyrido[2,3-d]pyrimidin-7(8H)-one (R1487) as orally bioavailable and highly selective inhibitors of p38α mitogen-activated protein kinase.

The development of a new series of p38α inhibitors resulted in the identification of two clinical candidates, one of which was advanced into a phase 2 clinical study for rheumatoid arthritis. The original lead, an lck inhibitor that also potently inhibited p38α, was a screening hit from our kinase inhibitor library. This manuscript describes the optimization of the lead to p38-selective examples with good pharmacokinetic properties.

A novel series of IKKß inhibitors part II: description of a potent and pharmacologically active series of analogs.

A novel series of (E)-1-((2-(1-methyl-1H-imidazol-5-yl) quinolin-4-yl) methylene) thiosemicarbazides was discovered as potent inhibitors of IKKß. In this Letter we document our efforts at further optimization of this series, culminating in 2 with submicromolar potency in a HWB assay and efficacy in a CIA mouse model.

A novel series of IKKß inhibitors part I: Initial SAR studies of a HTS hit.

A novel series of (E)-1-((2-(1-methyl-1H-imidazol-5-yl) quinolin-4-yl) methylene) thiosemicarbazides was discovered as potent inhibitors of IKKß. In this Letter we document our early efforts at optimization of the quinoline core, the imidazole and the semithiocarbazone moiety. Most potency gains came from substitution around the 6- and 7-positions of the quinoline ring. Replacement of the semithiocarbazone with a semicarbazone decreased potency but led to some measurable exposure.

Design and synthesis of 4-azaindoles as inhibitors of p38 MAP kinase.

Inhibition of the biosynthesis of proinflammatory cytokines such as tumor necrosis factor and interleukin-1 via p38 has been an approach toward the development of a disease modifying agent for the treatment of chronic inflammation and autoimmune diseases. The development of a new core structure of p38 inhibitors, 3-(4-fluorophenyl)-2-(pyridin-4-yl)-1H-pyrrolo[3,2-b] pyridine, is described. X-ray crystallographic data of the lead bound to the active site of p38 was used to guide the optimization of the series. Specific focus was placed on modulating the physical properties of the core while maintaining potent inhibition of p38. These efforts identified 42c as a potent inhibitor of p38, which also possessed the required physical properties worthy of advanced studies.