How a Promising Pancreatic Cancer Drug Loses Its Punch
A breakthrough oral drug for pancreatic cancer can shrink tumors dramatically — and then, after about seven months, stop working. The New York Times reported September 30 that former U.S. Senator Ben Sasse's Stage 4 pancreatic cancer had developed resistance to the drug after an initial strong response. Researchers are now mapping exactly how tumors evade it, hunting for ways to hit back.
The drug is daraxonrasib (code name RMC-6236), marketed as Rasonque by Revolution Medicines of Redwood City, California. It is a first-in-class RAS(ON) multi-selective "molecular glue" inhibitor: inside the cell it first binds the chaperone protein cyclophilin A (CypA), and the resulting complex then captures active, GTP-bound RAS — mutant KRAS G12D, G12V and G12R as well as wild-type RAS — sterically blocking RAS from engaging downstream effectors in the MAPK pathway. More than 90% of pancreatic tumors are driven by KRAS mutations, a target considered "undruggable" for decades.
The pivotal Phase 3 trial, RASolute 302, enrolled 500 patients with previously treated metastatic pancreatic cancer. Median overall survival was 13.2 months on daraxonrasib versus 6.7 months on chemotherapy (hazard ratio 0.40 — a 60% reduction in the risk of death); median progression-free survival was 7.3 versus 3.5 months; the objective response rate was 31.6%. The FDA approved the drug on August 26, 2026 for metastatic pancreatic adenocarcinoma after at least one prior systemic therapy — 6.5 months ahead of its target decision date.
But resistance arrives fast. "Nearly every pancreatic cancer patient taking that drug, called daraxonrasib, eventually develops resistance," Dr. Andrew Aguirre, a pancreatic cancer specialist at Dana-Farber Cancer Institute, told the Times. Sasse's tumor volume shrank 76% and his pain fell roughly 80% before the drug stopped working. One skeptical commentator notes the median duration of response is about 8.2 months — and that, unstated, "100% of these patients will eventually have disease progression and die."
A peer-reviewed study published September 30 in *Cancer Research* (AACR) revealed allele-specific escape routes. In KRAS G12D pancreatic cancer cells, resistance arises through retained KRAS-G12D-GTP signaling plus a decrease in cyclophilin A — the very binding partner the drug needs to work. In KRAS G12R cells, resistant tumors reroute through EGFR and wild-type-RAS-GTP signaling instead.
That finding points directly to salvage therapy. A KRAS G12R patient who progressed after 10 months on daraxonrasib received sixth-line trametinib-based combination therapy and gained about five months of disease control, reaching 40 months of overall survival — against a typical 8-to-12-month median for metastatic pancreatic cancer. Tyler Jacks of MIT called daraxonrasib and other KRAS inhibitors "important initial steps" toward "one day, cures."
The drug's significance lies in its reach. The FDA approval covers G12, G13 and Q61 mutants — more than 90% of pancreatic cancer patients — with no companion diagnostic required. On safety, more than 86% of patients developed a prominent skin rash, along with stomatitis, diarrhea, nausea and vomiting; but treatment discontinuation due to toxicity was just 1.2%, versus 11.2% for chemotherapy.
Not everyone shares the optimism. Physician-commentator Vinay Prasad argues the 8.2-month median response duration means the drug buys months, not cures. For patients facing a disease where only 13% are alive at five years, those months matter — but the framing matters too.
The research agenda is now clear: combination regimens to delay resistance, sequential salvage strategies after progression, and allele-specific precision approaches. The first gate of the RAS fortress has fallen. The road inside is still long.