Project Summary / Abstract The major goal in this application is to evaluate isatin-derived spirocyclic dimers as novel unfolded protein response (UPR) activators in proof-of-concept studies. Despite the dynamic changes in protein levels, protein homeostasis is maintained by a combination of tightly controlled processes which include synthesis, folding, trafficking and degradation. Accumulation of unfolded / misfolded proteins in the ER due to cell intrinsic and / or extrinsic signals results in the activation of UPR, an adaptation mechanism. Failure to resolve this results in irremediable ER stress and triggers UPR mediated programmed cell death. Cell intrinsic situations in cancer such as loss of tumor suppressor gene or oncogene addication result in higher basal UPR levels. Cancer cells maintain the higher basal UPR levels through upregulation of UPR associated proteins. The higher basal UPR levels in cancer cells provides a therapeutic window that can be exploited by UPR activators. This has been attributed to the success of proteasome inhibitors in the treatment of hematological malignancies. Although the success of proteasome inhibitors validates activation of UPR as a therapeutic modality, the need for UPR activators with novel mechanisms of action (MOA) is exemplified by the failure of proteasome inhibitors in patients with solid tumors. In this application we will address the above need by focusing on the development of a UPR activator with a novel MOA. We have identified an isatin-derived spirocyclic dimer (n7) that activates UPR in both normal and cancer cells but selectively induces apoptosis in cancer cells. Here we propose to continue the development of the novel chemical entity n7 through the following specific aims. Aim 1 will focus on characterization of n7 MOA, aim 2 will focus on structure activity relationship through synthesis and evaluation of n7 analogs and aim 3 will assess the efficacy of n7 or an improved UPR activator in in vivo models. Successful completion of the proposed aims will provide critical proof-of-concept for translating isatin-derived spirocyclic dimers as UPR activators.