Figure 3.

Colorectal cancer–specific immune responses induced by PolyPEPI1018 at peripheral and tumor level indicate treatment benefit. A, The breadth of TAA-specific CD8⁺ T-cell responses and magnitude of CD4⁺ T-cell responses in each patient measured by IVS ELISpot. Post-vaccination (Po) results are the maximum responses measured for each subject during the study. CD8 T-cell responses were measured using the individual 9-mer test peptides listed in Supplementary Table S1, and summed for obtaining TAA-specific responses. CD4 T-cell responses were measured with the pooled 30-mer peptides. B, Number of responsive vaccine TAAs plotted by patient (n = 10). Dark gray bars: Pre-only: No change or <2-fold increase in responses compared with pre-vaccination; mid gray bars: response boosted compared with pre-vaccination (at least 2-fold increase by IVS ELISpot); light gray: de novo induced vaccine-specific immune responses (no pre-vaccination response measured). C, Magnitude of PolyPEPI1018 vaccine-specific CD8⁺ and CD4⁺ T-cell responses detected at baseline and after multiple doses. D, T-cell (TIL) infiltration to the CT and IM area of the tumors post-vaccination assessed by HalioDx's Immunoscore CR TL assay. Changes in TIL density were calculated from IHC data obtained for pre/post-vaccination biopsy pairs; pre: baseline sample (except for Patient 01–0002, it was week 12 sample); Post: tumor biopsy at week 12 (for Patients 02–0002 and 02–0004) or week 38 (Patients 01–0002 and 01–0007). E, Whisker plot of upregulated gene-expression signatures upon treatment with PolyPEPI1018 for responder (R) tumors (Patients 02–0004, 01–0002, and 01–0007) and a nonresponder (NR) tumor (Patient 02–0002) assessed by NanoString's PanCancer gene-expression panel. Each dot represents the fold change of a gene in a sample. Boxes on the plot represents the quartiles (1 to 3). CD8⁺ effector T-cell gene signature: [CD8A molecule (CD8A), CD8B molecule (CD8B), eomesodermin (EOMES), granzyme A (GZMA), granzyme B (GZMB), IFNγ (IFNG), and perforin 1 (PRF1)]; IFNγ gene signature: [indoleamine 2,3-dioxygenase 1 (IDO1), C-X-C motif chemokine ligand (CXCL) 9 and 10, MHC class II DR α (HLA-DRA), signal transducer and activator of transcription 1 (STAT1) and IFNG] and PD-L1 and PD-L2 gene signatures. F, Impact of TAA-specific CD8⁺ T-cell responses boosted by the vaccine (measured by IVS ELISpot) on treatment benefit; DCB, durable clinical benefit = patients with objective tumor response (PR) and/or stabilized disease (SD) for at least 50 weeks on maintenance treatment; Others: patients with no DCB. ΔSFU, background corrected spot-forming units; #, number. ND, not detected; ns., not significant. Error bars represent SEM.