A Technical Feasibility Report On Correlative Studies From The Investigator-Initiated Phase Ii Study Of Pembrolizumab (Pembro) Immunological Response Evaluation (Inspire).

11607 Background: Validated biomarkers of response to immune checkpoint inhibitors are needed. Methods: INSPIRE (NCT02644369) is a biomarker-driven study to comprehensively evaluate changes in genomic and immune landscapes in tumors and blood of patients (pts) treated with pembro at 200 mg IV Q3W. It consists of 5 histological cohorts of 20 evaluable pts each: head and neck squamous cell cancer (SCCHN), triple negative breast cancer (TNBC), high grade serous ovarian cancer (HGSOC), melanoma (MM) and mixed solid tumors (MST). All pts undergo pre- and on-treatment (week 6-9) fresh tumor biopsies (bx), and at progression for responders. The first core bx is for immunohistochemistry and subsequent cores are pooled to create single cell suspension for 5 prioritized biomarker assay groups: (1) whole exome/RNA-/TCR-sequencing; (2) T/B/NK, APCs, and/or Treg phenotyping; (3) patient-derived xenografts; (4) RNA-seq on viably sorted immune populations; (5) TIL expansion and characterization. Serial blood samples for immunophenotyping, chemokines/cytokines and ctDNA are collected. Results: 53 pts were enrolled from March 21, 2016-January 16, 2017 (5 SCCHN, 8 TNBC, 17 HGSOC, 7 MM, 16 MST). 84 tumor bx (53 pre-, 30 on-treatment, 1 progression) and 244 blood-based biomarker samples have been collected. The most common sites of tumor bx were: lymph nodes (27%), liver (22%) and skin (14%) (see table). For the 5 cohorts, the % of tumor bx with sufficient cellularity for biomarker assay groups 1 and 2 are: SCCHN (33%), TNBC (9%), HGSOC (52%), MM (55%), MST (55%). Conclusions: This report provides robust technical feasibility data to plan immune and molecular characterization of tumor and blood-based biomarkers in pts receiving ICI. Clinical trial information: NCT02644369. [Table: see text]