Development of a Fluorinated Analogue of Erlotinib for PET Imaging of EGFR Mutation-Positive NSCLC.

PURPOSE: Positron emission tomography (PET) using [11C]erlotinib identifies non-small cell lung carcinoma (NSCLC) tumors with activating mutations in the epidermal growth factor receptor (EGFRm). The short half-life of C-11, however, limits its clinical utility to centers with a nearby cyclotron. We therefore developed a F-18-labeled analogue of erlotinib for imaging EGFRm NSCLC. PROCEDURES: 6-O-Fluoroethylerlotinib (6-O-FEE) was synthesized and its anti-proliferative activity was tested using human NSCLC cell lines. The F-18-labeled compound, 6-O-[18F]FEE, was obtained in a two-step synthesis, and PET acquisitions were carried out following its injection to NSCLC tumor-bearing mice. RESULTS: In vitro, 6-O-FEE had maintained the selectivity and potency of erlotinib to EGFRm NSCLC. In vivo, 6-O-[18F]FEE accumulation in EGFRm tumors at 60 min after injection was 2- and 3.3-fold higher than in erlotinib-resistant or erlotinib-insensitive tumors, respectively. CONCLUSIONS: 6-O-[18F]FEE holds promise for imaging EGFRm NSCLC, warranting further investigation to fully explore its potential for stratifying NSCLC patients.

Identifying erlotinib-sensitive non-small cell lung carcinoma tumors in mice using [(11)C]erlotinib PET.

BACKGROUND: Non-small cell lung carcinoma (NSCLC) represents approximately 80% of lung cancer cases, and over 60% of these tumors express the epidermal growth factor receptor (EGFR). Activating mutations in the tyrosine kinase (TK) domain of the EGFR are detected in 10% to 30% of NSCLC patients, and evidence of their presence is a prerequisite for initiation of first-line therapy with selective TK inhibitors (TKIs), such as gefitinib and erlotinib. To date, the selection of candidate patients for first-line treatment with EGFR TKIs requires an invasive tumor biopsy to affirm the mutational status of the receptor. This study was designed to evaluate whether positron emission tomography (PET) of NSCLC tumor-bearing mice using [(11)C]erlotinib could distinguish erlotinib-sensitive from erlotinib-insensitive or erlotinib-resistant tumors. METHODS: Four human NSCLC cell lines were employed, expressing either of the following forms of the EGFR: (i) the wild-type receptor (QG56 cells), (ii) a mutant with an exon 19 in-frame deletion (HCC827 cells), (iii) a mutant with the exon 21 L858R point mutation (NCI-H3255 cells), and (iv) a double mutant harboring the L858R and T790M mutations (NCI-H1975 cells). Sensitivity of each cell line to the anti-proliferative effect of erlotinib was determined in vitro. In vivo PET imaging studies following i.v. injection of [(11)C]erlotinib were carried out in nude mice bearing subcutaneous (s.c.) xenografts of the four cell lines. RESULTS: Cells harboring activating mutations in the EGFR TK domain (HCC827 and NCI-H3255) were approximately 1,000- and 100-fold more sensitive to erlotinib treatment in vitro, respectively, compared to the other two cell lines. [(11)C]Erlotinib PET scans could differentiate erlotinib-sensitive tumors from insensitive (QG56) or resistant (NCI-H1975) tumors already at 12 min after injection. Nonetheless, the uptake in HCC827 tumors was significantly higher than that in NCI-H3255, possibly reflecting differences in ATP and erlotinib affinities between the EGFR mutants. CONCLUSIONS: [(11)C]Erlotinib imaging in mice differentiates erlotinib-sensitive NSCLC tumors from erlotinib-insensitive or erlotinib-resistant ones.