LAUSR

Background: Larotrectinib, a selective TRKi, is now FDA approved for pediatric and adult TRK-fusion solid tumors, regardless of tumor origin. Emergent TRK kinase mutations are a common mechanism of resistance to TRKis. LOXO-195, a selective TRKi, was developed to maintain potency against multiple TRK kinase domain mutations. Methods: Patients (pts) received LOXO-195 via a Phase I study (NCT03215511, n=20) or FDA expanded access single patient protocol (SPP, n=11). Eligible pts were ≥4-weeks old with a locally identified TRK fusion and had progressed or were intolerant to at least 1 priorTRKi. Parallel 3+3 dose escalations were pursued in adults and children, with intra-patient dose escalation permitted based on tolerance and pharmacokinetics. Pts aged Results: As of 03-DEC-2018, a total of 31 TRK-fusion pts (7 children, 24 adults) with 11 cancer types had been treated. Median duration on last prior TRKi was 9.5 months (range, 2-30). In the Phase 1, doses of 32 mg QD to 150mg BID were explored, and TEAEs (all grades/cause, in >3 pts) were dizziness/ataxia (65%), nausea/vomiting (50%), anemia (30%), myalgia, abdominal pain, fatigue, & lymphopenia (all 20%). Five Phase I pts (all adults) had DLTs: ataxia/dizziness (4), and ataxia/vomiting (1). For the SPPs: 1 pt dose-reduced and none discontinued for a TEAE. Cmax at doses ≥50 mg exceeded the predicted IC50 for TRK kinase mutations. Pretreatment tissue and/or plasma, as available, defined TRK kinase mutation status. Preliminary efficacy overall, and by TRK kinase mutation status, is shown in the Table. Discussion: LOXO-195 had preliminary efficacy in pts with resistance to prior TRKi mediated by TRK kinase mutations. The subset of pts who develop TRK-independent resistance are unlikely to benefit from LOXO-195. Dose selection is ongoing in both children and adults. Citation Format: David Hyman, Shivaani Kummar, Anna Farago, Birgit Geoerger, Morten Mau-Sorensen, Matthew Taylor, Elena Garralda, Ramamoorthy Nagasubramanian, Michael Natheson, Lucy Song, Michael Capra, Mette Jorgensen, Alan Ho, Neerav Shukla, Steve Smith, Xin Huang, Brian Tuch, Nora Ku, Theodore W. Laetsch, Alexander Drilon, David Hong. Phase I and expanded access experience of LOXO-195 (BAY 2731954), a selective next-generation TRK inhibitor (TRKi) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT127.