Reference Detail

Ref Type

abstract

PMID

Authors

Patrick Schöffski, Michael C. Heinrich, Jonathan C. Trent, Cesar Serrano, Sebastian Bauer, Margaret von Mehren, Neeta Somaiah, Peter Reichardt, George D. Demetri, Nick Lydon, Jaap Verweij, Vivek Kadambi, Jessica Christo, Sean Kim, Debbie Johnson, James Shao, Suzanne George

Title

StrateGIST 1: A first-in-human (FIH), phase 1 study of IDRX-42 in patients with metastatic gastrointestinal stromal tumors resistant to prior treatment with tyrosine kinase inhibitors (TKIs).

Journal	Vol	Issue	Date	Pages	Journal Short Title
american society of clinical oncology	42	Supplement 16

URL

https://meetings.asco.org/abstracts-presentations/231575

Abstract Text

Background: Resistance to kinase inhibitors in gastrointestinal stromal tumors (GIST) is mainly driven by secondary mutations in KIT, and currently available TKIs fail to inhibit the full spectrum of secondary KIT mutations.IDRX-42 is an oral, potent, and highly selective inhibitor of the KITtyrosine kinase, active against multiple primary and secondary resistance mutations in KIT-driven GIST. We present data from the ongoing FIH phase (ph) 1 study evaluating IDRX-42 in patients (pts) with metastatic GIST in 2nd or later lines of therapy after failure of imatinib and other drugs. Methods: This ph 1 study evaluates the safety, tolerability, pharmacokinetics, and antitumor activity of oral IDRX-42 in adult pts with KIT-mutant GIST in dose escalation (ph1a) and defines the recommended dose for continued development (ph 1b). Ph 1b comprises 4 cohorts including pts without prior exposure to TKIs (1st line), pts treated with prior imatinib only (2nd line) and later line treatment cohorts. Correlative studies include sequential circulating tumor DNA (ctDNA) analyses and metabolic imaging using 18FDG-PET. Results: As of January 2, 2024, 42 pts received IDRX-42 in the ph 1a portion of the study with median treatment duration of 19+ (range 2-73+) weeks, with 30 pts remaining on treatment as of data cutoff. The median number of prior TKI therapy lines was 4 (range 1-6). Primary driver mutations were in KIT exon (ex) 11 (n = 27), ex 9 (n = 13) and ex 8 (n = 2). To date, five dose levels (120, 240, 400 and 600 mg QD; 400 mg BID) have been deemed safe to continue escalation. MTD has not been reached. A total of 39/42 pts are evaluable for efficacy; 9 achieved objective partial response (PR) per mRECIST (5 confirmed, 4 pending) across all doses studied. Three of 6 patients receiving IDRX-42 as 2nd line therapy have confirmed PRs at 120 mg QD, 400 mg QD, and 400 mg BID respectively. The clinical benefit rate (mRECIST PR or stable disease ≥16 weeks) is 71% overall and 100% in 2nd line. Sequential analyses of ctDNA show reductions across all primary and secondary KITmutations. Treatment-related adverse events (TRAE, CTCAE v5.0) were mainly low grade. The most frequently reported TRAE (≥25%) were gastrointestinal symptoms (diarrhea, nausea, vomiting, decreased appetite, dysgeusia) and fatigue. Eight of 42 pts reported Grade 3/4 TRAEs including gastrointestinal symptoms, fatigue and anemia. Two events qualified as DLT, 1 at 600 mg QD (syncope) and 1 at 400 mg BID (vomiting); after dose reduction both pts continued IDRX-42 for more than 8 and 5 months, respectively. Only two patients discontinued treatment due to TRAEs. Conclusions: IDRX-42 demonstrates promising clinical activity and a favorable safety profile in patients with advanced GIST following resistance to prior TKIs. Dose finding continues, and additional cohorts are ongoing. Clinical trial information: NCT05489237.

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Molecular Profile	Treatment Approach

Gene Name	Source	Synonyms	Protein Domains	Gene Description	Gene Role

Therapy Name	Drugs	Efficacy Evidence	Clinical Trials

Drug Name	Trade Name	Synonyms	Drug Classes	Drug Description

Gene	Variant	Impact	Protein Effect	Variant Description	Associated with drug Resistance

Molecular Profile	Indication/Tumor Type	Response Type	Therapy Name	Approval Status	Evidence Type	Efficacy Evidence	References
KIT exon11	gastrointestinal stromal tumor	predicted - sensitive	IDRX-42	Phase I	Actionable	In a Phase I trial, IDRX-42 treatment demonstrated safety and resulted in 9 partial responses among 39 evaluable patients with gastrointestinal stromal tumor harboring a KIT exon 11 (n=27), exon 9 (n=13), or exon 8 (n=2) mutation with a clinical benefit rate of 71% overall and 100% as second-line treatment (J Clin Oncol 42, 2024 (suppl 16; abstr 11501); NCT05489237).	detail...
KIT exon9	gastrointestinal stromal tumor	predicted - sensitive	IDRX-42	Phase I	Actionable	In a Phase I trial, IDRX-42 treatment demonstrated safety and resulted in 9 partial responses among 39 evaluable patients with gastrointestinal stromal tumors harboring a KIT exon 11 (n=27), exon 9 (n=13), or exon 8 (n=2) mutation with a clinical benefit rate of 71% overall and 100% as second-line treatment (J Clin Oncol 42, 2024 (suppl 16; abstr 11501); NCT05489237).	detail...