Abstract
Rociletinib (CO-1686), a 2,4-diaminopyrimidine derivative, is a highly potent tyrosine kinase inhibitor (TKI) that acts on epidermal growth factor receptor (EGFR) with L858R/T790M mutations. We supposed radioiodinated CO-1686 would function as a useful tool for monitoring EGFR L858R/T790M mutations. To aid in patient selection before therapy with EGFR-TKIs, this study aimed to develop a 125I-labeled derivative of CO-1686, N-{3-[(2-{[4-(4-acetylpiperazin-1-yl)-2-methoxyphenyl]amino}-5-(trifluoromethyl)pyrimidine-4-yl] amino}-5-([125I]iodophenyl)acrylamide ([125I]ICO1686) and evaluate its selectivity toward EGFR L858R/T790M. Radiosynthesis was performed by iododestannylation of the corresponding tributylstannyl precursor with [125I]NaI and N-chlorosuccinimide. The selectivity of the tracer for detecting EGFR L858R/T790M was evaluated using three relevant non-small cell lung cancer (NSCLC) cell lines—H1975, H3255 and H441 overexpressing the dual mutation EGFR L858R/T790M, active mutant EGFR L858R and wild-type EGFR, respectively. The nonradioactive ICO1686 and the precursor compound were successfully synthesized. A novel radiolabeled probe, [125I]ICO1686, was prepared with high radiochemical yield (77%) and purity (>99%). ICO1686 exhibited high cytotoxicity toward H1975 (IC50 0.20 ± 0.05 μM) and H3255 (IC50 0.50 ± 0.21 μM), which is comparable to that of CO-1686. In contrast, the cytotoxicity of ICO1686 toward H441 was 10-fold lower than that toward H1975. In the cell uptake study, the radioactivity uptake of [125I]ICO1686 in H1975 was 101.52% dose/mg, whereas the uptakes in H3255 and H441 were 33.52 and 8.95% dose/mg, respectively. The uptake of [125I]ICO1686 in H1975 was greatly reduced to 45.61% dose/mg protein by treatment with excess CO-1686. In vivo biodistribution study of the radiotracer found that its accumulation in H1975 tumor (1.77 ± 0.43% ID/g) was comparable to that in H3255 tumor (1.63 ± 0.23% ID/g) and the accumulation in H1975 tumor was not reduced by pretreatment with an excess dose of CO-1686. Although this radiotracer exhibited highly specific in vitro uptake in target cancer cells, structural modification is required to improve in vivo biodistribution.
Highlights
Despite the continuous development of cancer treatments, lung cancer remains a deadly disease worldwide [1]
Iodine was introduced to the diaminophenyl group of CO-1686, because this substituent would not overly influence the affinity of CO-1686 for epidermal growth factor receptor (EGFR)
L858R/T790M due to the complex crystal structure of CO-1686 and T790M EGFR [7]. Their complex crystal structure suggests that the anilinopyrimidine core, methoxy and trifluoromethyl groups are the most important substituents and play a key role in the binding of CO-1686 to EGFR L858R/T790M [7]
Summary
Despite the continuous development of cancer treatments, lung cancer remains a deadly disease worldwide [1]. Non-small cell lung cancer (NSCLC) is the most prevalent type, accounting for over 80%. Activated mutations in exons 18–21, in the kinase domain of epidermal growth factor receptor (EGFR), were associated with NSCLC; among them, frequently occurring mutations are the single L858R mutation in exon 21 and the EGFR exon 19 deletion [4,5,6]. The treatment of patients with NSCLC with EGFR-tyrosine kinase inhibitors (TKIs) has shown impressive therapeutic outcomes [3,7]. The first-generation EGFR-TKIs, gefitinib and erlotinib, significantly prolonged the overall survival of patients with NSCLC with the EGFR exon 19 deletion or EGFR L858R mutation [8,9]. Most patients acquire a further mutation in EGFR after long-term drug administration of first-generation EGFR-TKIs. Drug resistance eventually develops
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