Abstract CT103: Phase I study of LHC165 ± spartalizumab (PDR001) in patients (pts) with advanced solid tumors

Background: Toll-like receptors (TLRs), including TLR7, are involved in innate immune signaling. LHC165 is a TLR7 agonist which activates signaling pathways, increases cytokine release and promotes effector T-cell antitumor activity. In mouse models LHC165 treatment led to inhibition of tumor growth, and combination with an anti-PD-1 agent had more effective inhibition than either treatment alone. Methods: LHC165X2101 is a Phase I/Ib open-label dose-escalation/-expansion trial of LHC165 single agent (SA) ± spartalizumab, an anti-PD-1 mAb (NCT03301896). Eligible pts (≥18 yrs, ECOG 0-2) with advanced/metastatic solid tumors were treated with LHC165 SA (100-600 µg, Q2W intratumoral injection) ± spartalizumab (400 mg, Q4W IV). Primary objective was to assess safety and tolerability. Dose-escalation data are presented. Results: As of the data cutoff Sept 18, 2020, 39 pts enrolled; 20 pts received LHC165 SA and 19 pts combination. Median age 56 y, ECOG ≤1, median prior IO therapies: 2 (1-8) in SA pts, 3 (1-7) in combination pts. 37 (95%) pts discontinued: 27 (69%) progressive disease; 4 (10%) pt decision; 2 (5%) AEs; 2 (5%) completed treatment; and 2 (5%) pts died, treatment unrelated. 1 DLT of Gr 3 reversible pancreatitis was observed (LHC165 400 µg + spartalizumab 400 mg). AEs suspected to be treatment related observed in 22 (56%) pts; Gr ≥3 in 2 (5%) pts, 1 pt with lymphopenia and neutropenia, and 1 pt with pancreatitis. BOR in all pts was 3 PRs (all IO pretreated) and 4 SDs (1 IO pretreated). DCR (95%) was 18% (7.5%-33.5%). Median DOE (wks) was 4.5 (1.1-25.0) for SA pts, 11.9 (4.0-48.3) for combination pts. RDE was declared LHC165 600 µg ± spartalizumab 400 mg, with promising results in pts with melanoma and HNSCC. Systemic cytokine increases (CXCL10, IFNγ, IL6) were notable in a subset of pts following LHC165 ± spartalizumab. Immunohistochemistry tended to show higher baseline tumoral levels of CD8 and CD68 in pts with PR and on-treatment increases in pts with PR/SD. Tumoral RNA-sequencing showed higher T-cell inflammation at baseline in pts with PR and a consistent increase in T-cell inflammation in pts with PR/SD after treatment. Dose response relationships were not observed with available data. In most pts maximum LHC165 concentration was reached at around 1 hr, the first PK sampling time. Exposure of LHC165 ± spartalizumab increased with increasing dose of LHC165. Terminal half-life of LHC165 600 µg ranged from 9.4-58.9 hrs. No evidence of LHC165 accumu