Laboratory of Molecular Design
PET Imaging of KRAS2 Activation to Guide EGFR Targeting in Lung Cancer
Cancer cell growth depends on high expression of cancer genes. Overexpression of epithelial growth factor receptor (EGFR) stimulates lung cancer cell growth. Anti-EGFR antibodies or tyrosine kinase inhibitors (TKIs) fail in most lung cancer patients. KRAS2 activation makes cancer cell proliferation independent of EGFR activity. As a result, treating lung cancer with anti-EGFR antibodies or TKIs fails when KRAS2 has been mutated. We hypothesize that determining KRAS2 cancer gene mutation status by external mRNA PET imaging of mutant KRAS2 mRNA overexpression, as an adjunct to biopsy, will enable physicians to decide on alternatives to EGFR-directed therapies. We have imaged high levels of mutant KRAS2 mRNA and other oncogenes in malignant pancreas cancer xenografts. We designed radionuclide-chelator-spacer-peptide nucleic acid (PNA)-spacer-insulin-like growth factor 1 (IGF1) analogs to enable IGF1R-mediated cellular uptake and genetic radioimaging of mutant KRAS2 mRNA in suspect masses. We demonstrated sequence-specific PNA mRNA imaging and quantitation of high levels of mutant KRAS2 mRNA in pancreas cancer xenografts after tail vein injection of 99mTc (SPECT) or 64Cu (PET) PNA-spacer-IGF1 probes. To extend this technology platform to lung cancer, we propose to carry out essential preclinical steps to maximize the sensitivity of imaging multiple mutants of KRAS2 mRNA with a codon 12 redundant chelator-KRAS2 mRNA imaging agent in lung cancer xenografts. Our team includes an experienced radiopharmaceutical company, Molecular Targeting Technologies, which will submit an exploratory IND to FDA for a future trial of the KRAS2 mRNA imaging agent in patients with suspect lung masses. Specific Aim 1: Test the sensitivity and specificity of a codon 12 multimutant KRAS2 mRNA imaging agent in lung cancer xenografts. TJU will synthesize a novel KRAS2 mRNA imaging agent designed to detect multiple KRAS2 codon 12 mutations, and control sequences. MTTI will purify and analyze large scale batches of KRAS2 mRNA imaging agent and controls. Specific Aim 2: Determine whether genetic imaging of KRAS2 mRNA in lung cancer xenografts provides an early indication of the efficacy of antiproliferative chemotherapy. TJU will determine whether lowered KRAS2 mRNA, measured by mRNA PET imaging, provides an earlier indication of the efficacy of antiproliferative chemotherapy, compared with [18F]FDG measurement of metabolic activity. Specific Aim 3: Obtain an eIND number from FDA for a future feasibility study. MTTI will acquire a dedicated cGMP batch of the KRAS2 mRNA imaging agent, direct a microdose toxicology study in rats, compile and submit the eIND application for the KRAS2 mRNA imaging agent to FDA, then address FDA questions and concerns. Early external imaging of lung cancer gene activity might (1) improve diagnosis of early lung cancer, (2) avoid biopsy trauma in patients with benign masses, (3) guide EGFR targeted therapy, and (4) ultimately reduce deaths from lung cancer.
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