Title

A Phase I/Ib Trial of the VEGFR-Sparing Multikinase RET Inhibitor RXDX-105.

Document Type

Article

Publication Date

3-1-2019

Publication Title

Cancer Discov

Abstract

RET fusions are oncogenic drivers of various tumors, including non-small cell lung cancers (NSCLC). The safety and antitumor activity of the multikinase RET inhibitor RXDX-105 were explored in a phase I/Ib trial. A recommended phase II dose of 275 mg fed daily was identified. The most common treatment-related adverse events were fatigue (25%), diarrhea (24%), hypophosphatemia (18%), maculopapular rash (18%), and nonmaculopapular rash (17%). In the phase Ib cohort of RET inhibitor-naïve patients with RET fusion-positive NSCLCs, the objective response rate (ORR) was 19% (95% CI, 8%-38%, n = 6/31). Interestingly, the ORR varied significantly by the gene fusion partner (P < 0.001, Fisher exact test): 0% (95% CI, 0%-17%, n = 0/20) with KIF5B (the most common upstream partner for RET fusion-positive NSCLC), and 67% (95% CI, 30%-93%, n = 6/9) with non-KIF5B partners. The median duration of response in all RETfusion-positive NSCLCs was not reached (range, 5 to 18+ months). SIGNIFICANCE: Although KIF5B-RET is the most common RET fusion in NSCLCs, RET inhibition with RXDX-105 resulted in responses only in non-KIF5B-RET-containing cancers. Novel approaches to targeting KIF5B-RET-containing tumors are needed, along with a deeper understanding of the biology that underlies the differential responses observed.

PubMed ID

30487236

Volume

9

Issue

3

First Page

384

Last Page

395

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