Phase 1/2 trial of the XPO1 inhibitor selinexor in combination with docetaxel in previously treated, advanced KRAS mutant non-small cell lung cancer (NSCLC)

Background: KRAS mutant NSCLC remains a therapeutic challenge. Although KRAS G12C inhibitors are now approved for cases harboring that specific mutation, their efficacy is modest and the G12C variant accounts for only 40% of KRAS mutations in NSCLC. To date, there are no approved targeted therapies for non- G12C KRAS mutant NSCLC. Selective inhibitors of nuclear export (SINE) modulate cancer cell biology by retaining certain proteins—such as tumor suppressors—within the nucleus, where they remain physiologically active. The XPO1 inhibitor selinexor demonstrated efficacy in preclinical NSCLC models harboring various KRAS mutations.

Methods: In this 3 + 3 dose-escalation phase 1/2 trial, patients with previously treated advanced KRAS mutant NSCLC received selinexor (dosed orally weekly) plus docetaxel 75 mg/m 2 IV every three weeks (NCT03095612). Prior treatment with KRAS G12C inhibitors was permitted.

Results: Among 40 enrolled patients, median age was 66 years, 22 (55%) were female, and 34 (85%) were white. KRAS mutation types included G12C (28%), G12V (23%), G12D (20%), G12A (13%), G12R (5%), G13C (5%), and one case each of G12S, G13D, Q61L, and K117N. Patients had received a median of 2 prior lines of therapy (range 1-4). The maximum tolerated dose of selinexor was 60 mg PO weekly combined with docetaxel. The most common adverse events (AE) were nausea (73%, Gr ≥3 8%), fatigue (70%, Gr ≥3 5%), neutropenia (65%, Gr ≥3 60%), diarrhea (58%, Gr ≥3 10%), anorexia (50%, Gr ≥3 0%), and vomiting (45%, Gr ≥3 5%). Of 32 patients evaluable for efficacy, 7 (22%) had partial response (PR) and 18 (56%) had stable disease (SD) as best response. Median progression-free survival (PFS) was 4.1 months (95% CI, 2.9-5 months); median overall survival (OS) was 7.1 months (95% CI, 4.5-13.7 months). Clinical outcomes did not differ significantly among KRAS mutation types. However, TP53 co-mutations (48%) were associated with significantly worse outcomes: disease control rate (PR + SD) 27% vs 92% (P=0.006); median PFS 1.8 vs 7.4 months (P<0.001); median OS 5.8 vs 17 months (P=0.006). Additional biomarker studies are ongoing.

Conclusions: Selinexor plus docetaxel is tolerated with multi-agent supportive care. The combination shows moderate efficacy across KRAS mutation types, with promising activity in TP53 wild type cases.