Induction of antigen specific CD8+ T cell infiltration by a novel neoadjuvant vaccine containing HSP70 and GPC3 peptides plus soluble LAG-3 and Poly-IC:LC: Interim results of a Phase I study.

Abstract

e14306 Background: Even with curative resection, the recurrence rate of HCC is still high, and no effective adjuvant therapy is currently available. Our previous Phase I study with novel therapeutic peptides and immune adjuvants demonstrated the safety, antigen specific CTL induction in PBMC and a sign of efficacy (ASCO 2017 Abstract # 3086); thus, we started Phase I study of the same therapy as a perioperative immunotherapy setting in patients with resectable HCC (UMIN000029991). Methods: Two mg each of HLA-A*24:02, 02:01, or 02:06 restricted HSP70- and GPC3-derived peptides, in combination with hLAG-3Ig (1.0 mg) + Poly-IC:LC (1.4 mg) were injected intradermally at four sites of the inguinal and axillary regions every week for 6 weeks before surgery. Patients subsequently received 10 injections of adjuvant immunotherapy over 4 months. Surgical specimens and PBMCs were analyzed by mass cytometry (CyTOF), using 66 antibodies to monitor T cell exhaustion, T cell activation, Effector Treg induction, etc. Tumor specimens were also subjected to immunohistochemical staining of CD3, CD8, PD1, HSP70, and GPC3. The reason for early reporting is the interesting findings at the foci of HCC, and the interim analyses was approved by the Data and Safety Monitoring Committee. Results: Of the 11 screened patients, 5 completed the treatments and were analyzed. We found massive CD8+ T lymphocyte infiltration in the intratumor foci of HCC, which is usually accompanied by peritumoral lymphocytic infiltration. Moreover, the density of lymphocytes was markedly higher in areas of HSP70 or GPC3 antigen expression. One case out of five recurred 5 month after surgery and it showed low CD8+ and PD1+ cell infiltration and high effector Treg (CD4+/CD25+/CD45RA-/FoxP3 +) infiltration. This trend was not observed in PBMC, suggesting the importance of TIL analysis. The high PD1 expression was accompanied by massive intratumoral infiltration of CD8+ lymphocytes. Conclusions: The novel therapeutic peptide and immune adjuvant combination induced sustained immune cell infiltration into tumor microenvironments, especially those presenting target tumor-associated antigens. Our novel immunotherapy may convert cold tumors into hot tumors containing PD1+ lymphocytes. Thus, the combination of this novel strategy with PD (L) 1 antibody is warranted. Clinical trial information: 000029991.