Abstract 2538: Immune responses to common melanoma-associated antigens following intratumoral injection of alpha-gal glycolipids in patients with advanced melanoma

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Background: One mechanism of immune escape in the tumor microenvironment is the inhibition of processes involved in tumor antigen uptake by antigen presenting cells (APC). Effective uptake of tumor cells by APC is achieved pre-clinically by labeling them with α-gal glycolipids (α-gal) and exploiting the natural anti-Gal antibody response that constitutes approximately 1% of immunoglobulins in humans. The current study involves intratumoral injection of glycolipids expressing α-gal epitopes in patients (pts) with advanced melanoma and evaluates, in HLA-A2+ treated pts, the development of immune responses to common melanoma-associated antigens (MAA). Methods: Eligibility criteria included unresectable metastatic melanoma (recurrent stage III or stage IV); at least one readily resectable cutaneous, subcutaneous, or readily palpable lymph node metastasis; and a serum anti-Gal titer above 1:50. Pts received 2 injections of alpha-gal glycolipids four weeks apart at 0.1 mg/injection (n=3; dose level 1), 1.0 mg/injection (n=3; dose level 2), or 10 mg/injection (n=3; dose level 3). Ex vivo pre-treatment and Day 57 post-treatment peripheral blood mononuclear cells (PBMC) from pts who were HLA-A2+ (8 of 9 treated pts) were stained with pooled MAA pentamers (gp100209-217, gp100154-162, Melan-A/MART-126-35, NY-ESO-1157-165, and Tyrosinase368-376) and evaluated by flow cytometry. Cells stained with cytomegalovirus (CMV) pp65495-504 or HTLV-1 Tax11-19 served as positive or negative controls, respectively. Results: MAA pentamer+ T cells were detected in 7 of 8 HLA-A2+ pts, both pre- and post-treatment. The frequency of MAA pentamer+ T cells post- versus pre-treatment increased approximately 2-fold for 2 pts [one from dose level 2 and one from dose level 3 (0.16% vs. 0.082%, and 0.033% vs. 0.017%, respectively (background subtracted))]. Similar increases were not observed for the other 5 pts with detectable MAA pentamer+ cells. Furthermore, the median fluorescence intensity (MFI) of MAA pentamer+ T cells, an indirect measure of T cell activation potential, was markedly higher post-treatment, as compared to pre-treatment, for 2 of 3 pts in dose level 1 (11227 vs. 3027, and 4045 vs. 1581). Substantial changes in MFI were not observed for the other pts.. Conclusions: Intratumoral injection of α-gal glycolipids can increase the ex vivo frequency of circulating MAA reactive T cells in some pts with advanced melanoma. Based on this finding, we are pursuing functional characterization of these pre- and post-treatment PBMC. Citation Format: Cindy L. Zuleger, Paul M. Sondel, Jacquelyn A. Hank, Erik A. Ranheim, Thomas A. McFarland, Jennifer Collins, Erin Clements, Giles Whalen, Uri Galili, Mark R. Albertini. Immune responses to common melanoma-associated antigens following intratumoral injection of alpha-gal glycolipids in patients with advanced melanoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2538. doi:10.1158/1538-7445.AM2014-2538