Abstract
The dysfunction and death of pancreatic ß cells are key features in all types of diabetes. It was recently
shown that increased proinsulin misfolding occurs well before the onset of diabetes and is responsible for
events, including endoplasmic reticulum (ER) stress, leading to ß-cell dysfunction and death in diabetes. There
is currently no interventional means that suppresses proinsulin misfolding. In our preliminary studies, we
identified a small molecule (named as PTTD) that protects ß-cells from ER stress-induced death in a high-
throughput screen. We discovered that PTTD suppressed the ER stress-induced activation of all three
branches (IRE1, PERK, and ATF6) of unfolded protein response (UPR) pathways in ß-cells under ER stress.
We then observed that PTTD eliminated the accumulation of misfolded proinsulin while increasing mature
insulin production in ß-cells and that PTTD suppressed purified insulin protein misfolding/aggregation in cell-
free biochemical assays. Importantly, in in vivo animal studies, PTTD significantly ameliorated hyperglycemia
in multiple mouse diabetes models of ß-cell failure. These exciting results demonstrate that suppression of
proinsulin misfolding by PTTD protects ß-cells and ameliorates diabetes. In this application, we will use PTTD
as the starting molecule to develop potent analogs as first-in-class proinsulin misfolding inhibitors. To achieve
this, we will use an approach that integrates iterative and parallel medicinal chemistry with in vitro and in vivo
efficacy and DMPK studies with specific aims. In Aim 1, we will improve and optimize our lead compound,
PTTD, through medicinal chemistry-based structure-activity relationship studies. In Aim 2, compounds with
improved potency will be characterized physicochemically and pharmacologically using standardized ADMET
and in vivo PK assays. In Aim 3, we will evaluate the in vivo efficacy of lead PTTD analogs in two well-
established diabetes models of proinsulin misfolding and progressive ß cell loss. Completion of this work will
not only identify PTTD and its analogs as first-in-class chemical suppressors of proinsulin misfolding for ß-cell
protection, but also establish the suppression of proinsulin misfolding as a new therapeutic direction for
diabetes, which will serve as a foundation and provide a lead compound that may guide further development of
proinsulin folding therapeutics.
