Abstract A038: The feasibility of inducing effective systemic immune responses to human metastatic melanoma with intralesional secreted cytokines

The induction of new additional immune responses to potential neoantigens on metastatic melanoma resulting in dense lymphocytic infiltrates might cause regression of metastases and could enhance the effects of anti-check point therapies. The blocking of CTLA-4 or PD-1/PD-L1, which normally constrain immune responses, results in significant prolongation of life and up to 7% complete responses (CRs) of metastatic melanoma when used individually. Insufficient nascent anti-melanoma immunity may account for the relatively low frequency of CRs. Also the lack of specificity in the dis-inhibition of immune responses can cause adverse reactions. We investigated a different strategy: inducing new specific immune responses to metastatic melanoma with mixed secreted cytokines. The development of immune responses is regulated by multiple cytokines/chemokines (CKs) acting in concert. To mimic this secretory environment, in a non-randomized prospective study, 88 patients with multiple palpable cutaneous/subcutaneous metastases (stages IIIC and IV-M1a) received weekly injections of autologous secreted CKs into some metastatic nodules while other metastases were never injected. CKs were prepared ex-vivo by stimulating PBMCs with recall microbial antigens to which the patients were sensitive as assessed by PBMC proliferative responses. The secreted mixtures contained individual cytokines at picogram to nanogram concentrations. New immune responses were identified by the development of dense lymphocytic infiltrates in never-injected metastases, consisting of CD8 and smaller numbers of CD4 T cells. This study was conducted before the availability of current therapies. After multiple injections into some metastatic nodules, never-injected metastases developed dense tumor-infiltrating lymphocytes (TILs) and often regressed completely. CD8 TILs from metastases directly killed fresh autologous melanoma cells ex-vivo in an MHC-restricted manner without in- vitro boosting. Although both never-injected and injected metastases often regressed completely, in some patients new metastases appeared even while never- injected nodules were regressing. The new metastases often regressed with or without injections. In 40% of subjects all never-injected and injected metastases regressed completely for > 2 months. 20% remained free of disease for 5 to 28 years (median 60 months, range 2 to 334 months). Median overall survival of patients, progressing and regressing, was 28.5 months (4-348 months), with 55% of patients surviving 2 years, and 30% 5 years. Durable disease-free survival also occurred in recipients of intracutaneous CKs mixed with irradiated autologous melanoma cells. No adverse events occurred. We conclude that intralesional secreted, mixed CKs can induce new systemic and effective cellular immune responses to metastatic melanoma. Mixtures of secreted cytokine/chemokines (CKs) may be more effective in inducing the development of immune responses than individual CKs. These immune responses were associated with a surprisingly high frequency (40%) of complete regressions and prolonged disease-free periods of 1 to 28 years. These new anti-melanoma cellular immune responses also might enhance the frequency of clinical responses to subsequent anti-check point therapies. Citation Format: Fred T. Valentine, Frederick M. Golomb, Matthew Haris, Daniel F. Roses. The feasibility of inducing effective systemic immune responses to human metastatic melanoma with intralesional secreted cytokines. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A038.