Proteolytic pan-RAS Cleavage Leads to Tumor Regression in Patient-derived Pancreatic Cancer Xenografts

Vania Vidimar, Minyoung Park, Caleb K. Stubbs, Nana K. Ingram, Wenan Qiang, Shanshan Zhang, Demirkan Gursel, Roman A. Melnyk, Karla J.F. Satchell*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


The lack of effective RAS inhibition represents a major unmet medical need in the treatment of pancreatic ductal adenocarcinoma (PDAC). Here, we investigate the anticancer activity of RRSP-DTB, an engineered biologic that cleaves the Switch I of all RAS isoforms, in KRAS-mutant PDAC cell lines and patient-derived xenografts (PDX). We first demonstrate that RRSP-DTB effectively engages RAS and impacts downstream ERK signaling in multiple KRAS-mutant PDAC cell lines inhibiting cell proliferation at picomolar concentrations. We next tested RRSP-DTB in immunodeficient mice bearing KRAS-mutant PDAC PDXs. Treatment with RRSP-DTB led to ≥95% tumor regression after 29 days. Residual tumors exhibited disrupted tissue architecture, increased fibrosis and fewer proliferating cells compared with controls. Intratumoral levels of phospho-ERK were also significantly lower, indicating in vivo target engagement. Importantly, tumors that started to regrow without RRSP-DTB shrank when treatment resumed, demonstrating resistance to RRSP-DTB had not developed. Tracking persistence of the toxin activity following intraperitoneal injection showed that RRSP-DTB is active in sera from immunocompetent mice for at least 1 hour, but absent after 16 hours, justifying use of daily dosing. Overall, we report that RRSP-DTB strongly regresses hard-to-treat KRAS-mutant PDX models of pancreatic cancer, warranting further development of this pan-RAS biologic for the management of RAS-addicted tumors.

Original languageEnglish (US)
Pages (from-to)810-820
Number of pages11
JournalMolecular cancer therapeutics
Issue number5
StatePublished - May 2022

ASJC Scopus subject areas

  • Oncology
  • Cancer Research


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