The L730V/I RET roof mutations display different activities toward pralsetinib and selpercatinib

Abstract

Recently Food and Drug Administration (FDA)-approved pralsetinib (BLU-667) and selpercatinib (LOXO-292) are RET-selective protein tyrosine kinase inhibitors for treating RET-altered cancers, but whether they have distinct activity was unknown. The L730V/I mutations at the roof of the solvent-front site of the RET kinase were identified as strongly resistant to pralsetinib but not to selpercatinib. Selpercatinib effectively inhibited these mutants and the KIF5B-RET(L730V/I) oncogene-driven tumors.

Fig. 1. L730V/I display different sensitivity to pralsetinib and selpercatinib.

a BaF3 cells containing KIF5B-RET or KIF5B-RET with indicated mutations were treated with pralsetinib or selpercatinib for 3 days, and viable cells were determined. Data points are means and s.d. b Cell lysates were analyzed by immunoblotting with indicated antibodies. c The vicinity of L730 and G810 of RET kinase. The carbon atoms of the pralsetinib complex (PDB: 7JU5) are colored cyan, and those of the selpercatinib complex (PDB: 7JU6) are colored orange. The sidechain at site 730 has been changed to a valine, modeled in its most favorable state in the absence of the drugs. G810 has been changed to serine. d–g data from L730I tumors. d BaF3/KIF5B-RET(L730I) xenograft tumors were treated with pralsetinib, selpercatinib, or vehicle. Tumor sizes were measured on the indicated days. The data shown are the mean ± s.d. e Tumor weight at the endpoint. The error bars shown are mean ± s.d. *p < 0.05. ns, p > 0.05. f Waterfall plot of tumor size change at the endpoint from the baseline (prior to drug treatment). Each bar corresponds to a tumor in each mouse (6 per group). g Tissue samples from two different mice in each group were analyzed by immunoblotting with the indicated antibodies. PST pralsetinib, SPC selpercatinib. h–k data from the BaF3/KIF5B-RET(L730V) tumors. The experiment was performed in parallel to the BaF3/KIF5B-RET(L730I) tumors as described above for the (d–g) panels.