Structure-Activity-Relationship Exploration and Animal Validation of a Novel Assembly Modulator Small Molecule Chemical Series with Pan-Cancer Selective Cytotoxicity

PAV-620, and PAV-805 are chemical analogs from a protein assembly modulating small molecule lead series that displays broad anti-cancer activity. These compounds are active against all cancers in the NCI-60 cancer cell line screen, which is representative of diverse blood, brain, breast, colon, lung, ovarian, prostate, renal, and skin cancers. Safety in mice is observed up to doses of 10 mg/kg daily and nontoxicity to healthy human peripheral blood mononuclear cells at doses up to 20uM. The compounds are as efficacious as Paclitaxel in reducing tumor growth and metastasis in the aggressive 4T1 mouse allograft model for triple negative breast cancer. The mechanism of action of PAV-620 and PAV-805 in primary carcinoma cells under conditions inducing programmed cell death was found to be distinct from the cytotoxic mechanisms of Staurosporine, Paclitaxel, and Etoposide. PAV-805 was shown to target a small subset of protein disulfide isomerase (PDI) in a dynamic multi-protein complex enriched in the cancer hallmark proteins involved in reprogramming energy metabolism. These data suggest a new approach to cancer therapeutics, with selectivity arising not from targeting PDI itself, an abundant cellular protein, but from targeting a disease-associated assembly state of PDI-containing complexes as a therapeutically exploitable dimension of cancer biology.