Necroptosis blockade prevents lung injury in severe influenza.

Severe influenza A virus (IAV) infections can result in hyper-inflammation, lung injury and acute respiratory distress syndrome1-5 (ARDS), for which there are no effective pharmacological therapies. Necroptosis is an attractive entry point for therapeutic intervention in ARDS and related inflammatory conditions because it drives pathogenic lung inflammation and lethality during severe IAV infection6-8 and can potentially be targeted by receptor interacting protein kinase 3 (RIPK3) inhibitors. Here we show that a newly developed RIPK3 inhibitor, UH15-38, potently and selectively blocked IAV-triggered necroptosis in alveolar epithelial cells in vivo. UH15-38 ameliorated lung inflammation and prevented mortality following infection with laboratory-adapted and pandemic strains of IAV, without compromising antiviral adaptive immune responses or impeding viral clearance. UH15-38 displayed robust therapeutic efficacy even when administered late in the course of infection, suggesting that RIPK3 blockade may provide clinical benefit in patients with IAV-driven ARDS and other hyper-inflammatory pathologies.

A high-affinity conformation of Hsp90 confers tumour selectivity on Hsp90 inhibitors.

Heat shock protein 90 (Hsp90) is a molecular chaperone that plays a key role in the conformational maturation of oncogenic signalling proteins, including HER-2/ErbB2, Akt, Raf-1, Bcr-Abl and mutated p53. Hsp90 inhibitors bind to Hsp90, and induce the proteasomal degradation of Hsp90 client proteins. Although Hsp90 is highly expressed in most cells, Hsp90 inhibitors selectively kill cancer cells compared to normal cells, and the Hsp90 inhibitor 17-allylaminogeldanamycin (17-AAG) is currently in phase I clinical trials. However, the molecular basis of the tumour selectivity of Hsp90 inhibitors is unknown. Here we report that Hsp90 derived from tumour cells has a 100-fold higher binding affinity for 17-AAG than does Hsp90 from normal cells. Tumour Hsp90 is present entirely in multi-chaperone complexes with high ATPase activity, whereas Hsp90 from normal tissues is in a latent, uncomplexed state. In vitro reconstitution of chaperone complexes with Hsp90 resulted in increased binding affinity to 17-AAG, and increased ATPase activity. These results suggest that tumour cells contain Hsp90 complexes in an activated, high-affinity conformation that facilitates malignant progression, and that may represent a unique target for cancer therapeutics.

Rationally designed high-affinity 2-amino-6-halopurine heat shock protein 90 inhibitors that exhibit potent antitumor activity.

Heat shock protein 90 (Hsp90) is a molecular chaperone protein implicated in stabilizing the conformation and maintaining the function of many cell-signaling proteins. Many oncogenic proteins are more dependent on Hsp90 in maintaining their conformation, stability, and maturation than their normal counterparts. Furthermore, recent data show that Hsp90 exists in an activated form in malignant cells but in a latent inactive form in normal tissues, suggesting that inhibitors selective for the activated form could provide a high therapeutic index. Hence, Hsp90 is emerging as an exciting new target for the treatment of cancer. We now report on a novel series of 2-amino-6-halopurine Hsp90 inhibitors exemplified by 2-amino-6-chloro-9-(4-iodo-3,5-dimethylpyridin-2-ylmethyl)purine (30). These highly potent inhibitors (IC50 of 30 = 0.009 microM in a HER-2 degradation assay) also display excellent antiproliferative activity against various tumor cell lines (IC50 of 30 = 0.03 microM in MCF7 cells). Moreover, this class of inhibitors shows higher affinity for the activated form of Hsp90 compared to our earlier 8-sulfanylpurine Hsp90 inhibitor series. When administered orally to mice, these compounds exhibited potent tumor growth inhibition (>80%) in an N87 xenograft model, similar to that observed with 17-allylamino-17-desmethoxygeldanamycin (17-AAG), which is a compound currently in phase I/II clinical trials.

First-in-class pan caspase inhibitor developed for the treatment of liver disease.

A series of oxamyl dipeptides were optimized for pan caspase inhibition, anti-apoptotic cellular activity and in vivo efficacy. This structure-activity relationship study focused on the P4 oxamides and warhead moieties. Primarily on the basis of in vitro data, inhibitors were selected for study in a murine model of alpha-Fas-induced liver injury. IDN-6556 (1) was further profiled in additional in vivo models and pharmacokinetic studies. This first-in-class caspase inhibitor is now the subject of two Phase II clinical trials, evaluating its safety and efficacy for use in liver disease.

The heat-shock protein 90 inhibitor 17-allylamino-17-demethoxygeldanamycin suppresses glial inflammatory responses and ameliorates experimental autoimmune encephalomyelitis.

The heat-shock response (HSR), a highly conserved cellular response, is characterized by rapid expression of heat-shock proteins (HSPs), and inhibition of other synthetic activities. The HSR can attenuate inflammatory responses, via suppression of transcription factor activation. A HSR can be induced pharmacologically by HSP90 inhibitors, through activation of the transcription factor Heat Shock Factor 1 (HSF1). In the present study we characterized the effects of 17-allylamino-17-demethoxygeldanamycin (17-AAG), a less toxic derivative of the naturally occurring HSP90 inhibitor geldanamycin, on glial inflammatory responses and the development of experimental autoimmune encephalomyelitis. In primary enriched glial cultures, 17-AAG dose dependently reduced lipopolysaccharide-dependent expression and activity of inducible nitric oxide synthase, attenuated interleukin (IL)-1beta expression and release, increased inhibitor of kappaB protein levels, and induced HSP70 expression. 17-AAG administration to mice immunized with myelin oligodendrocyte glycoprotein peptide prevented disease onset when given at an early time, and reduced clinical symptoms when given during ongoing disease. T cells from treated mice showed a reduced response to immunogen re-stimulation, and 17-AAG reduced CD3- and CD28-dependent IL-2 production. Together, these data suggest that HSP90 inhibitors could represent a new approach for therapeutic intervention in autoimmune diseases such as multiple sclerosis.

Acyl dipeptides as reversible caspase inhibitors. Part 1: initial lead optimization.

Parallel synthesis was used to explore the SAR of a peptidomimetic caspase inhibitor. The most potent compound had nanomolar activity against caspases 1, 3, 6, 7, and 8.

Acyl dipeptides as reversible caspase inhibitors. Part 2: further optimization.

A new structural class of broad spectrum caspase inhibitors was optimized for its activity against caspases 1, 3, 6, 7, and 8. The most potent compound had low nanomolar broad spectrum activity, in particular, single digit nanomolar inhibitory activity against caspase 8.