Signal transducer and activator of transcription 3 (STAT3) is a transcription factor and an attractive therapeutic target for cancer and other human diseases. Despite 20 years of persistent research efforts, targeting STAT3 has been very challenging. We report herein the structure-based discovery of potent small-molecule STAT3 degraders based upon the proteolysis targeting chimera (PROTAC) concept. We first designed SI-109 as a potent, small-molecule inhibitor of the STAT3 SH2 domain. Employing ligands for cereblon/cullin 4A E3 ligase and SI-109, we obtained a series of potent PROTAC STAT3 degraders, exemplified by SD-36. SD-36 induces rapid STAT3 degradation at low nanomolar concentrations in cells and fails to degrade other STAT proteins. SD-36 achieves nanomolar cell growth inhibitory activity in leukemia and lymphoma cell lines with high levels of phosphorylated STAT3. A single dose of SD-36 results in complete STAT3 protein degradation in xenograft tumor tissue and normal mouse tissues. SD-36 achieves complete and long-lasting tumor regression in the Molm-16 xenograft tumor model at well-tolerated dose-schedules. SD-36 is a potent, selective, and efficacious STAT3 degrader.

Photoreceptor cell death is the ultimate cause of vision loss in many retinal disorders, and there is an unmet need for neuroprotective modalities to improve photoreceptor survival. Similar to cancer cells, photoreceptors maintain pyruvate kinase muscle isoform 2 (PKM2) expression, which is a critical regulator in aerobic glycolysis. Unlike PKM1, which has constitutively high catalytic activity, PKM2 is under complex regulation. Recently, we demonstrated that genetically reprogramming photoreceptor metabolism via PKM2-to-PKM1 substitution is a promising neuroprotective strategy. Here, we explored the neuroprotective effects of pharmacologically activating PKM2 via ML-265, a small molecule activator of PKM2, during acute outer retinal stress. We found that ML-265 increased PKM2 activity in 661 W cells and in vivo in rat eyes without affecting the expression of genes involved in glucose metabolism. ML-265 treatment did, however, alter metabolic intermediates of glucose metabolism and those necessary for biosynthesis in cultured cells. Long-term exposure to ML-265 did not result in decreased photoreceptor function or survival under baseline conditions. Notably, though, ML-265-treatment did reduce entrance into the apoptotic cascade in in vitro and in vivo models of outer retinal stress. These data suggest that reprogramming metabolism via activation of PKM2 is a novel, and promising, therapeutic strategy for photoreceptor neuroprotection.

Redox modulators have been developed as an attractive approach to treat cancer. Herein, we report the synthesis, identification, and biological evaluation of a quinazolinedione reactive oxygen species (ROS) inducer, QD394, with significant cytotoxicity in pancreatic cancer cells. QD394 shows a transcriptomic profile remarkably similar to napabucasin, a cancer stemness inhibitor. Both small molecules inhibit STAT3 phosphorylation, increase cellular ROS, and decrease the GSH/GSSG ratio. Moreover, QD394 causes an iron- and ROS-dependent, GPX4 mediated cell death, suggesting ferroptosis as a major mechanism. Importantly, QD394 decreases the expression of LRPPRC and PNPT1, two proteins involved in mitochondrial RNA catabolic processes and both negatively correlated with the overall survival of pancreatic cancer patients. Pharmacokinetics-guided lead optimization resulted in the derivative QD394-Me, which showed improved plasma stability and reduced toxicity in mice compared to QD394. Overall, QD394 and QD394-Me represent novel ROS-inducing drug-like compounds warranting further development for the treatment of pancreatic cancer.

Ginger is known to have antiinflammatory and antioxidative effects and has traditionally been used as an herbal supplement in the treatment of various chronic diseases. Here, we report antineutrophil properties of 6-gingerol, the most abundant bioactive compound of ginger root, in models of lupus and antiphospholipid syndrome (APS). Specifically, we demonstrate that 6-gingerol attenuates neutrophil extracellular trap (NET) release in response to lupus- and APS-relevant stimuli through a mechanism that is at least partially dependent on inhibition of phosphodiesterases. At the same time, administration of 6-gingerol to mice reduces NET release in various models of lupus and APS, while also improving other disease-relevant endpoints, such as autoantibody formation and large-vein thrombosis. In summary, this study is the first to our knowledge to demonstrate a protective role for ginger-derived compounds in the context of lupus. Importantly, it provides a potential mechanism for these effects via phosphodiesterase inhibition and attenuation of neutrophil hyperactivity.

Inhibition of oxidative phosphorylation (OX-PHOS) is a promising therapeutic strategy for select cancers that are dependent on aerobic metabolism. Here, we report the discovery, optimization, and structure−activity relationship (SAR) study of a series of novel OXPHOS inhibitors. The hit compound, benzene-1,4-disulfonamide 1, was discovered in a phenotypic screen selective for cytotoxicity in a galactose-containing medium. Our multi-parameter optimization campaign led to the discovery of 65 (DX3-235), showing nanomolar inhibition of complex I function and adenosine triphosphate (ATP) production in a galactose-containing medium resulting in significant cytotoxicity. Importantly, 64 (DX3-234), a close analogue of 65, is well tolerated in mice and shows significant single agent efficacy in a Pan02 syngeneic pancreatic cancer model, suggesting that highly potent and selective OXPHOS inhibitors can be useful for the treatment of pancreatic cancer.