GRP78 Selective Inhibitors From a Direct-to-Biology Strategy

Area of Science:

• Biochemistry
• Molecular Biology
• Cancer Therapeutics

Background:

• Cancer cells exhibit increased protein homeostasis demands, making proteostasis machinery a therapeutic target.
• The 70 kDa heat shock protein (HSP70) family is differentially regulated in cancers, necessitating isoform-selective targeting to avoid toxicity.
• GRP78 (HSPA5/BiP), an endoplasmic reticulum-resident HSP70, is crucial for secretory protein homeostasis and the unfolded protein response (UPR).

Purpose of the Study:

• To develop a GRP78-selective inhibitor using a direct-to-biology (D2B) strategy.
• To optimize a dipeptide-based scaffold for selective binding to GRP78 over other HSP70s.
• To validate the therapeutic potential of a GRP78-selective inhibitor in lung cancer models.

Main Methods:

• Employed a direct-to-biology (D2B) strategy to optimize a dipeptide scaffold.
• Synthesized and characterized lead compound 12 for GRP78 selectivity and binding.
• Assessed compound 12's efficacy in A549 lung cancer cells (2D and 3D cultures) and confirmed GRP78 engagement and inhibition.

Main Results:

• Identified a lead compound, 12, that potently and selectively inhibits GRP78.
• Compound 12 binds to the substrate-binding pocket of GRP78.
• Demonstrated that GRP78 inhibition by compound 12 leads to A549 lung cancer cell death in vitro.
• Confirmed GRP78 engagement and that its inhibition is the primary mode of action.

Conclusions:

• This study presents the first GRP78-selective inhibitor capable of inhibiting substrate binding.
• The developed compound shows promise as a targeted therapeutic agent for cancers reliant on GRP78.
• Isoform-selective targeting of HSP70 family members, like GRP78, offers a viable strategy for cancer therapy with potentially reduced toxicity.