Discovery of DNL343: A Potent, Selective, and Brain-Penetrant eIF2B Activator Designed for the Treatment of Neurodegenerative Diseases

Eukaryotic translation initiation factor 2B (eIF2B) is a key component of the integrated stress response (ISR), which regulates protein synthesis and stress granule formation in response to cellular insult. Modulation of the ISR has been proposed as a therapeutic strategy for treatment of neurodegenerative diseases such as vanishing white matter (VWM) disease and amyotrophic lateral sclerosis (ALS) based on its ability to improve cellular homeostasis and prevent neuronal degeneration. Herein, we report the small-molecule discovery campaign that identified potent, selective, and CNS-penetrant eIF2B activators using both structure- and ligand-based drug design. These discovery efforts culminated in the identification of DNL343, which demonstrated a desirable preclinical drug profile, including a long half-life and high oral bioavailability across preclinical species. DNL343 was progressed into clinical studies and is currently undergoing evaluation in late-stage clinical trials for ALS.

LRRK2 Inhibition by BIIB122 in Healthy Participants and Patients with Parkinson's Disease

BACKGROUND

Leucine-rich repeat kinase 2 (LRRK2) inhibition is a promising therapeutic approach for the treatment of Parkinson's disease (PD).

OBJECTIVE

The aim of this study was to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of the potent, selective, CNS-penetrant LRRK2 inhibitor BIIB122 (DNL151) in healthy participants and patients with PD.

METHODS

Two randomized, double-blind, placebo-controlled studies were completed. The phase 1 study (DNLI-C-0001) evaluated single and multiple doses of BIIB122 for up to 28 days in healthy participants. The phase 1b study (DNLI-C-0003) evaluated BIIB122 for 28 days in patients with mild to moderate PD. The primary objectives were to investigate the safety, tolerability, and plasma pharmacokinetics of BIIB122. Pharmacodynamic outcomes included peripheral and central target inhibition and lysosomal pathway engagement biomarkers.

RESULTS

A total of 186/184 healthy participants (146/145 BIIB122, 40/39 placebo) and 36/36 patients (26/26 BIIB122, 10/10 placebo) were randomized/treated in the phase 1 and phase 1b studies, respectively. In both studies, BIIB122 was generally well tolerated; no serious adverse events were reported, and the majority of treatment-emergent adverse events were mild. BIIB122 cerebrospinal fluid/unbound plasma concentration ratio was ~1 (range, 0.7-1.8). Dose-dependent median reductions from baseline were observed in whole-blood phosphorylated serine 935 LRRK2 (≤98%), peripheral blood mononuclear cell phosphorylated threonine 73 pRab10 (≤93%), cerebrospinal fluid total LRRK2 (≤50%), and urine bis (monoacylglycerol) phosphate (≤74%).

CONCLUSIONS

At generally safe and well-tolerated doses, BIIB122 achieved substantial peripheral LRRK2 kinase inhibition and modulation of lysosomal pathways downstream of LRRK2, with evidence of CNS distribution and target inhibition. These studies support continued investigation of LRRK2 inhibition with BIIB122 for the treatment of PD. © 2023 Denali Therapeutics Inc and The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Topoisomerase Inhibitors Addressing Fluoroquinolone Resistance in Gram-Negative Bacteria

Since their discovery over 5 decades ago, quinolone antibiotics have found enormous success as broad spectrum agents that exert their activity through dual inhibition of bacterial DNA gyrase and topoisomerase IV. Increasing rates of resistance, driven largely by target-based mutations in the GyrA/ParC quinolone resistance determining region, have eroded the utility and threaten the future use of this vital class of antibiotics. Herein we describe the discovery and optimization of a series of 4-(aminomethyl)quinolin-2(1H)-ones, exemplified by 34, that inhibit bacterial DNA gyrase and topoisomerase IV and display potent activity against ciprofloxacin-resistant Gram-negative pathogens. X-ray crystallography reveals that 34 occupies the classical quinolone binding site in the topoisomerase IV-DNA cleavage complex but does not form significant contacts with residues in the quinolone resistance determining region.

Structural and Biological Basis of Small Molecule Inhibition of Escherichia coli LpxD Acyltransferase Essential for Lipopolysaccharide Biosynthesis

LpxD, acyl-ACP-dependent N-acyltransferase, is the third enzyme of lipid A biosynthesis in Gram-negative bacteria. A recent probe-based screen identified several compounds, including 6359-0284 (compound 1), that inhibit the enzymatic activity of Escherichia coli (E. coli) LpxD. Here, we use these inhibitors to chemically validate LpxD as an attractive antibacterial target. We first found that compound 1 was oxidized in solution to the more stable aromatized tetrahydro-pyrazolo-quinolinone compound 1o. From the Escherichia coli strain deficient in efflux, we isolated a mutant that was less susceptible to compound 1o and had an lpxD missense mutation (Gly268Cys), supporting the cellular on-target activity. Using surface plasma resonance, we showed direct binding to E. coli LpxD for compound 1o and other reported LpxD inhibitors in vitro. Furthermore, we determined eight cocrystal structures of E. coli LpxD/inhibitor complexes. These costructures pinpointed the 4'-phosphopantetheine binding site as the common ligand binding hotspot, where hydrogen bonds to Gly269 and/or Gly287 were important for inhibitor binding. In addition, the LpxD/compound 1o costructure rationalized the reduced activity of compound 1o in the LpxD_Gly268Cys mutant. Moreover, we obtained the LpxD structure in complex with a previously reported LpxA/LpxD dual targeting peptide inhibitor, RJPXD33, providing structural rationale for the unique dual targeting properties of this peptide. Given that the active site residues of LpxD are conserved in multidrug resistant Enterobacteriaceae, this work paves the way for future LpxD drug discovery efforts combating these Gram-negative pathogens.