A selective and orally bioavailable VHL-recruiting PROTAC achieves SMARCA2 degradation in vivo

Targeted protein degradation offers an alternative modality to classical inhibition and holds the promise of addressing previously undruggable targets to provide novel therapeutic options for patients. Heterobifunctional molecules co-recruit a target protein and an E3 ligase, resulting in ubiquitylation and proteosome-dependent degradation of the target. In the clinic, the oral route of administration is the option of choice but has only been achieved so far by CRBN- recruiting bifunctional degrader molecules. We aimed to achieve orally bioavailable molecules that selectively degrade the BAF Chromatin Remodelling complex ATPase SMARCA2 over its closely related paralogue SMARCA4, to allow in vivo evaluation of the synthetic lethality concept of SMARCA2 dependency in SMARCA4-deficient cancers. Here we outline structure- and property-guided approaches that led to orally bioavailable VHL-recruiting degraders. Our tool compound, ACBI2, shows selective degradation of SMARCA2 over SMARCA4 in ex vivo human whole blood assays and in vivo efficacy in SMARCA4-deficient cancer models. This study demonstrates the feasibility for broadening the E3 ligase and physicochemical space that can be utilised for achieving oral efficacy with bifunctional molecules.

Psychiatric and physical outcomes of long-term use of lithium in older adults with bipolar disorder and major depressive disorder: A cross-sectional multicenter study

OBJECTIVE

Although lithium is widely used in current practice to treat bipolar disorder (BD) and treatment-resistant major depressive disorder (MDD) among older adults, little is known about its efficacy and tolerability in this population, which is generally excluded from randomized clinical trials. The objective of this study was to evaluate the efficacy and tolerability of long-term use of lithium among older adults with BD and MDD.

METHOD

Data from the Cohort of individuals with Schizophrenia and mood disorders Aged 55 years or more (CSA) were used. Two groups of patients with BD and MDD were compared: those who were currently receiving lithium versus those who were not. The effects of lithium on psychiatric (i.e., depressive symptoms severity, perceived clinical severity, rates of psychiatric admissions in the past-year), geriatric (overall and cognitive functioning) and physical outcomes (i.e., rates of non-psychiatric medical comorbidities and general hospital admissions in the past-year) were evaluated. All analyses were adjusted for age, sex, duration of disorder, diagnosis, smoking status, alcohol use, and use of antipsychotics, antiepileptics or antidepressants.

RESULTS

Among the 281 older participants with BD or MDD, 15.7% were taking lithium for a mean duration of 12.5(SD = 11.6) years. Lithium use was associated with lower intensity of depressive symptoms, reduced perceived clinical global severity and lower benzodiazepine use (all p < 0.05), without being linked to greater rates of medical comorbidities, except for hypothyroidism.

LIMITATIONS

Data were cross-sectional and data on lifetime history of psychotropic medications was not assessed.

CONCLUSION

Our results suggest that long-term lithium use may be efficient and relatively well-tolerated in older adults with BD or treatment-resistant MDD.

PTPσ inhibitors promote hematopoietic stem cell regeneration

Receptor type protein tyrosine phosphatase-sigma (PTPσ) is primarily expressed by adult neurons and regulates neural regeneration. We recently discovered that PTPσ is also expressed by hematopoietic stem cells (HSCs). Here, we describe small molecule inhibitors of PTPσ that promote HSC regeneration in vivo. Systemic administration of the PTPσ inhibitor, DJ001, or its analog, to irradiated mice promotes HSC regeneration, accelerates hematologic recovery, and improves survival. Similarly, DJ001 administration accelerates hematologic recovery in mice treated with 5-fluorouracil chemotherapy. DJ001 displays high specificity for PTPσ and antagonizes PTPσ via unique non-competitive, allosteric binding. Mechanistically, DJ001 suppresses radiation-induced HSC apoptosis via activation of the RhoGTPase, RAC1, and induction of BCL-XL. Furthermore, treatment of irradiated human HSCs with DJ001 promotes the regeneration of human HSCs capable of multilineage in vivo repopulation. These studies demonstrate the therapeutic potential of selective, small-molecule PTPσ inhibitors for human hematopoietic regeneration.

Abstract 3849: Structure-based PROTAC design demonstrates BAF complex ATPase vulnerabilities in cancer

Targeting subunits of BAF/PBAF complexes has been proposed as an approach to exploit cancer vulnerabilities, yet small molecules developed to date have remained largely ineffectual. Here we develop PROTAC degraders of the BAF ATPase subunits SMARCA2 and SMARCA4 using a bromodomain ligand and recruitment of the E3 ubiquitin ligase VHL. High-resolution ternary complex crystal structures and biophysical investigation guided the rational optimization of ACBI1, a potent cooperative SMARCA2/4 degrader. ACBI1 induced antiproliferative effects and cell death caused by SMARCA2 depletion in SMARCA4 mutant cancer cells, and in acute myeloid leukemia cells dependent on SMARCA4 ATPase activity. These findings exemplify a successful biophysics and structure driven campaign to degrade targets previously considered undruggable, and pave the way towards new therapeutics for the treatment of tumors sensitive to the loss of BAF complex ATPases.

Citation Format: Manfred Koegl, William Farnaby, Claire Whitworth, Michael Roy, Emelyne Diers, Nicole Trainor, Steffen Steurer, Carina Riedmueller, Teresa Gmaschitz, Johannes Wachter, Christian Dank, Michael Gallant, Bernadette Sharps, Klaus Rumpel, Elisabeth Traxler, Romario Lorenz, Oliver Petermann, Peter Greb, Harald Weinstabl, Gerd Bader, Andreas Zoephel, Alexander Weiss-Puxbaum, Joerg Rinnenthal, Heribert Arnnhof, Nicola Wiechens, Meng-Ying Wu, Tom Owen-Hughes, Peter Ettmayer, Mark Pearson, Darryl B. McConnell, Alessio Ciulli. Structure-based PROTAC design demonstrates BAF complex ATPase vulnerabilities in cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3849.

BAF complex vulnerabilities in cancer demonstrated via structure-based PROTAC design

Targeting subunits of BAF/PBAF chromatin remodeling complexes has been proposed as an approach to exploit cancer vulnerabilities. Here we develop PROTAC degraders of the BAF ATPase subunits SMARCA2 and SMARCA4 using a bromodomain ligand and recruitment of the E3 ubiquitin ligase VHL. High-resolution ternary complex crystal structures and biophysical investigation guided rational and efficient optimization towards ACBI1, a potent and cooperative degrader of SMARCA2, SMARCA4 and PBRM1. ACBI1 induced antiproliferative effects and cell death caused by SMARCA2 depletion in SMARCA4 mutant cancer cells, and in acute myeloid leukemia cells dependent on SMARCA4 ATPase activity. These findings exemplify a successful biophysics- and structure-based PROTAC design approach to degrade high profile drug targets and pave the way towards new therapeutics for the treatment of tumors sensitive to the loss of BAF complex ATPases.

Triazole-assisted ruthenium-catalyzed C-H arylation of aromatic amides

Site-selective ruthenium(II)-catalyzed direct arylation of amides was achieved through CH cleavages with modular auxiliaries, derived from easily accessible 1,2,3-triazoles. The triazolyldimethylmethyl (TAM) bidentate directing group was prepared in a highly modular fashion through copper(I)-catalyzed 1,3-dipolar cycloaddition and allowed for ruthenium-catalyzed CH arylations on arenes and heteroarenes, as well as alkenes, by using easy-to-handle aryl bromides as the arylating reagents. The triazole-assisted CH activation strategy was found to be widely applicable, to occur under mild reaction conditions, and the catalytic system was tolerant of important electrophilic functionalities. Notably, the flexible triazole-based auxiliary proved to be a more potent directing group for the optimized ruthenium(II)-catalyzed direct arylations, compared with pyridyl-substituted amides or substrates derived from 8-aminoquinoline.

Ruthenium-catalyzed C-H bond arylations of arenes bearing removable directing groups via six-membered ruthenacycles

Ruthenium-catalyzed direct arylations of phenols bearing removable directing groups were accomplished through carboxylate assistance via six-membered ruthenacycles as key intermediates.