Inhibiting the HSP90 chaperone slows cyst growth in a mouse model of autosomal dominant polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) is a progressive genetic syndrome with an incidence of 1:500 in the population, arising from inherited mutations in the genes for polycystic kidney disease 1 (PKD1) or polycystic kidney disease 2 (PKD2). Typical onset is in middle age, with gradual replacement of renal tissue with thousands of fluid-filled cysts, resulting in end-stage renal disease requiring dialysis or kidney transplantation. There currently are no approved therapies to slow or cure ADPKD. Mutations in the PKD1 and PKD2 genes abnormally activate multiple signaling proteins and pathways regulating cell proliferation, many of which we observe, through network construction, to be regulated by heat shock protein 90 (HSP90). Inhibiting HSP90 with a small molecule, STA-2842, induces the degradation of many ADPKD-relevant HSP90 client proteins in Pkd1(-/-) primary kidney cells and in vivo. Using a conditional Cre-mediated mouse model to inactivate Pkd1 in vivo, we find that weekly administration of STA-2842 over 10 wk significantly reduces initial formation of renal cysts and kidney growth and slows the progression of these phenotypes in mice with preexisting cysts. These improved disease phenotypes are accompanied by improved indicators of kidney function and reduced expression and activity of HSP90 clients and their effectors, with the degree of inhibition correlating with cystic expansion in individual animals. Pharmacokinetic analysis indicates that HSP90 is overexpressed and HSP90 inhibitors are selectively retained in cystic versus normal kidney tissue, analogous to the situation observed in solid tumors. These results provide an initial justification for evaluating HSP90 inhibitors as therapeutic agents for ADPKD.

HSP90 Inhibitor-SN-38 Conjugate Strategy for Targeted Delivery of Topoisomerase I Inhibitor to Tumors.

The clinical benefits of chemotherapy are commonly offset by insufficient drug exposures, narrow safety margins, and/or systemic toxicities. Over recent decades, a number of conjugate-based targeting approaches designed to overcome these limitations have been explored. Here, we report on an innovative strategy that utilizes HSP90 inhibitor-drug conjugates (HDC) for directed tumor targeting of chemotherapeutic agents. STA-12-8666 is an HDC that comprises an HSP90 inhibitor fused to SN-38, the active metabolite of irinotecan. Mechanistic analyses in vitro established that high-affinity HSP90 binding conferred by the inhibitor backbone could be exploited for conjugate accumulation within tumor cells. In vivo modeling showed that the HSP90 inhibitor moiety was required for selective retention of STA-12-8666, and this enrichment promoted extended release of active SN-38 within the tumor compartment. Indeed, controlled intratumoral payload release by STA-12-8666 contributed to a broad therapeutic window, sustained biomarker activity, and remarkable degree of efficacy and durability of response in multiple cell line and patient-derived xenograft models. Overall, STA-12-8666 has been developed as a unique HDC agent that employs a distinct mechanism of targeted drug delivery to achieve potent and sustained antitumor effects. These findings identify STA-12-8666 as a promising new candidate for evaluation as novel anticancer therapeutic.

The oncology drug elesclomol selectively transports copper to the mitochondria to induce oxidative stress in cancer cells.

Elesclomol is an investigational drug that exerts potent anticancer activity through the elevation of reactive oxygen species (ROS) levels and is currently under clinical evaluation as a novel anticancer therapeutic. Here we report the first description of selective mitochondrial ROS induction by elesclomol in cancer cells based on the unique physicochemical properties of the compound. Elesclomol preferentially chelates copper (Cu) outside of cells and enters as elesclomol-Cu(II). The elesclomol-Cu(II) complex then rapidly and selectively transports the copper to mitochondria. In this organelle Cu(II) is reduced to Cu(I), followed by subsequent ROS generation. Upon dissociation from the complex, elesclomol is effluxed from cells and repeats shuttling elesclomol-Cu complexes from the extracellular to the intracellular compartments, leading to continued copper accumulation within mitochondria. An optimal range of redox potentials exhibited by copper chelates of elesclomol and its analogs correlated with the elevation of mitochondrial Cu(I) levels and cytotoxic activity, suggesting that redox reduction of the copper triggers mitochondrial ROS induction. Importantly the mitochondrial selectivity exhibited by elesclomol is a distinct characteristic of the compound that is not shared by other chelators, including disulfiram. Together these findings highlight a unique mechanism of action with important implications for cancer therapy.

Potent anti-muscarinic activity in a novel series of quinuclidine derivatives.

The synthesis and biological evaluation of a novel family of M(3) muscarinic antagonists are described. A systematic modification of the substituents to a novel alkyne-quinuclidine scaffold yielded original compounds displaying potent in vitro anticholinergic properties.