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.

Selective Inhibitors of Dual Leucine Zipper Kinase (DLK, MAP3K12) with Activity in a Model of Alzheimer's Disease

Significant data exists to suggest that dual leucine zipper kinase (DLK, MAP3K12) is a conserved regulator of neuronal degeneration following neuronal injury and in chronic neurodegenerative disease. Consequently, there is considerable interest in the identification of DLK inhibitors with a profile compatible with development for these indications. Herein, we use structure-based drug design combined with a focus on CNS drug-like properties to generate compounds with superior kinase selectivity and metabolic stability as compared to previously disclosed DLK inhibitors. These compounds, exemplified by inhibitor 14, retain excellent CNS penetration and are well tolerated following multiple days of dosing at concentrations that exceed those required for DLK inhibition in the brain.

Toxicity profile of small-molecule IAP antagonist GDC-0152 is linked to TNF-α pharmacology

Inhibitor-of-apoptosis (IAP) proteins suppress apoptosis and are overexpressed in a variety of cancers. Small-molecule IAP antagonists are currently being tested in clinical trials as novel cancer therapeutics. GDC-0152 is a small-molecule drug that triggers tumor cell apoptosis by selectively antagonizing IAPs. GDC-0152 induces NF-κB transcriptional activity leading to expression of several chemokines and cytokines, of which tumor necrosis factor alpha (TNF-α) is the most important for single-agent tumor activity. TNF-α is a pleiotropic cytokine that drives a variety of cellular responses, comprising inflammation, proliferation, and cell survival or death depending on the cellular context. As malignant and normal cells produce TNF-α upon IAP antagonism, increased TNF-α could drive both efficacy and toxicity. The toxicity profile of GDC-0152 in dogs and rats was characterized after iv dose administration once every 2 weeks for four doses. Findings in both species consisted of a dose-related, acute, systemic inflammatory response, and hepatic injury. Laboratory findings included elevated plasma cytokines, an inflammatory leukogram, and increased liver transaminases with histopathological findings of inflammatory infiltrates and apoptosis/necrosis in multiple tissues; a toxicology profile consistent with TNF-α-mediated toxicity. Dogs exhibited more severe findings than rats, and humans did not exhibit these findings, at comparable exposures across species. Furthermore, elevations in blood neutrophil count, serum monocyte chemoattractant protein-1, and other markers of inflammation corresponded to GDC-0152 exposure and toxicity and thus may have utility as safety biomarkers.

Wear rates of resin composites

SUMMARY A laboratory study was conducted to examine the wear of resin composite materials using a generalized wear simulation model. Ten specimens each of five resin composites (Esthet•X [EX], Filtek Supreme Plus [SP], Filtek Z250 [Z2], Tetric EvoCeram [EC], and Z100 Restorative [Z1]) were subjected to wear challenges of 100,000, 400,000, 800,000, and 1,200,000 cycles. The materials were placed in cylinder-shaped stainless-steel fixtures, and wear was generated using a flat stainless-steel antagonist in a slurry of polymethylmethacrylate beads. Wear (mean facet depth [μm] and volume loss [mm(3)]) was determined using a noncontact profilometer (Proscan 2000) with Proscan and ProForm software. Statistical analysis of the laboratory data using analysis of variance and Tukey's post hoc test showed a significant difference (p<0.05) for mean wear facet depth and volume loss for both the number of cycles and resin composite material. Linear regression analysis was used to develop predictive wear rates and volume loss rates. Linear wear was demonstrated with correlation coefficients (R(2)) ranging from 0.914 to 0.995. Mean wear values (mean facet depth [μm]) and standard deviations (SD) for 1200K cycles were as follows: Z1 13.9 (2.0), Z2 26.7 (2.7), SP 30.1 (4.1), EC 31.8 (2.3), and EX 67.5 (8.2). Volume loss (mm(3)) and SDs for 1200K cycles were as follows: Z1 0.248 (0.036), Z2 0.477 (0.044), SP 0.541 (0.072), EC 0.584 (0.037), and EX 1.162 (0.139). The wear rate (μm) and volume loss rate (mm(3)) per 100,000 cycles for the five resin composites were as follows: wear rate Z1 0.58, EC 1.27, Z2 1.49, SP 1.62, and EX 4.35, and volume loss rate Z1 0.009, EC 0.024, Z2 0.028, SP 0.029, and EX 0.075. The generalized wear model appears to be an excellent method for measuring relative wear of resin composite materials.

WITHDRAWN. Neurological assessments after treatment with the antimalarial β-arteether in neonatal and adult rats

The World Health Organization currently recommends combinatorial treatment including artemisinins as first-line therapy against drug-resistant Plasmodium falciparum malaria. Although highly efficacious, artemisinin and its derivatives, including β-arteether (βAE), are associated with ototoxicity, tremors, and other autonomic and motor impairments in the clinic. Similar neurological symptoms, as well as brainstem lesions, have been observed in adult laboratory species (mice, rats, dogs, and non human primates) following acute treatment with βAE; however, few long-term, nonclinical studies have been conducted. Furthermore, the majority of deaths attributed to malarial infection occur in children under age five, yet no laboratory studies have been initiated in neonatal or juvenile animals. In the current study, neonatal 7-day-old rats were administered intramuscular doses of 1-90mg/kg βAE in sesame oil for up to eight treatment cycles (one cycle=7days treatment+7days without treatment). Neonates were tested for changes in sensorimotor function, and the same animals were tested as adults in the Functional Observational Battery, for motor activity, and in the 8-arm radial maze. Pups receiving a single cycle of 60 or 90mg/kg died within a week of treatment but had few behavioral changes and no brainstem pathology. In the long-term study, behavioral and motor changes and brainstem lesions were observed in a dose- and time-related manner. Rats given repeated cycles of 1 or 5mg/kg βAE showed subtle motor abnormalities (e.g., slight loss of righting reflex) while repeated cycles of 10mg/kg βAE treatment resulted in obvious motor and behavioral changes. Rats receiving 1mg/kg βAE had no brainstem lesions whereas some rats treated with 5mg/kg βAE and all rats treated with 10mg/kg βAE had brainstem lesions. Brainstem lesions were observed after as few as five cycles and were characterized by gliosis, satellitosis and progressive necrosis in motor neurons of the trapezoid, vestibular, and olivary nuclei. This study shows that repeated treatment with clinically relevant doses of βAE causes motor deficits associated with brainstem damage in rodents and suggests that repeated treatment with βAE in children may elicit neurological damage.

Neural progenitor implantation restores metabolic deficits in the brain following striatal quinolinic acid lesion

Neural progenitor transplantation is a potential treatment for neurodegenerative diseases, including Huntington's disease (HD). In the current study, we tested the potential of rat embryonic neural progenitors expanded in vitro as therapy in the rat quinolinic acid-lesioned striatum, a model that demonstrates some of the pathological features of HD. We used positron emission tomography (PET) to demonstrate that the intrastriatal injection of cultured rat neural progenitors results in improved metabolic function in the striatum and overlying cortex when compared to media-injected controls. Transplanted progenitors were capable of surviving, migrating long distances and differentiating into neurons and glia. The cortices of transplanted animals contained greater numbers of neurons in regions that had shown metabolic improvement. However, histological analysis revealed that only a small fraction of these increased neurons could be accounted for by engrafted cells, indicating that the metabolic sparing was likely the result of a trophic action of the transplanted cells on the host. Behavioral testing of the implanted animals did not reveal improvement in apomorphine-induced rotation. These data demonstrate that progenitor cell implantation results in enhanced metabolic function and sparing of neuron number, but that these functions do not necessarily result in the restoration of complex circuitry.