Phase I study with ONCOS-102 for the treatment of solid tumors - an evaluation of clinical response and exploratory analyses of immune markers

Abstract

Background: We conducted a phase I study with a granulocyte macrophage colony stimulating factor (GMCSF)-expressing oncolytic adenovirus, ONCOS-102, in patients with solid tumors refractory to available treatments. The objectives of the study were to determine the optimal dose for further use and to assess the safety, tolerability and adverse event (AE) profile of ONCOS-102. Further, the response rate and overall survival were evaluated as well as preliminary evidence of disease control. As an exploratory endpoint, the effect of ONCOS 102 on biological correlates was examined.

Methods: The study was conducted using a classic 3 + 3 dose escalation study design involving 12 patients. Patients were repeatedly treated intratumorally with ONCOS-102 plus daily low-dose oral cyclophosphamide (CPO). Tumor response was evaluated with diagnostic positron emission tomography (PET) and computed tomography (CT). Tumor biopsies were collected at baseline and after treatment initiation for analysis of immunological correlates. Peripheral blood mononuclear cells (PBMCs) were collected at baseline and during the study to assess antigen specificity of CD8+ T cells by interferon gamma (IFNγ) enzyme linked immunospot assay (ELISPOT).

Results: No dose limiting toxicity (DLT) or maximum tolerated dose (MTD) was identified for ONCOS-102. Four out of ten (40 %) evaluable patients had disease control based on PET/CT scan at 3 months and median overall survival was 9.3 months. A short-term increase in systemic pro-inflammatory cytokines and a prominent infiltration of TILs to tumors was seen post-treatment in 11 out of 12 patients. Two patients showed marked infiltration of CD8+ T cells to tumors and concomitant systemic induction of tumor-specific CD8+ T cells. Interestingly, high expression levels of genes associated with activated TH1 cells and TH1 type immune profile were observed in the post-treatment biopsies of these two patients.

Conclusions: ONCOS-102 is safe and well tolerated at the tested doses. All three examined doses may be used in further development. There was evidence of antitumor immunity and signals of clinical efficacy. Importantly, treatment resulted in infiltration of CD8+ T cells to tumors and up-regulation of PD-L1, highlighting the potential of ONCOS-102 as an immunosensitizing agent for combinatory therapies with checkpoint inhibitors.

Trial registration: NCT01598129. Registered 19/04/2012.

Keywords: Anti-tumor immunity; Cytotoxic CD8+ T cell; Immunotherapy; Intratumoral; Oncolytic adenovirus; in situ vaccine.

Fig. 1

Intratumoral ONCOS-102 treatment triggered a short-term increase in the systemic levels of pro-inflammatory cytokines. Treatment with ONCOS-102 induced a short-term increase of systemic pro-inflammatory cytokines IL-6 and IL-8 in patients. The increase was most prominent 6 h after each treatment and decreased nearly to baseline-values by the 24-h time-point

Fig. 2

ONCOS-102 viral particles in blood. ONCOS-102 particles in blood were analyzed before each administration and 6 and 24 h after each administration. The number of viral genomes peaked at 6-h and lower values were detected 24-h after administration. A secondary peak in virus titer (*) suggests a productive virus replication at tumor site. Data is presented as median of all patients per time point

Fig. 3

Intratumoral ONCOS-102 treatment induced an infiltration of immune cells to tumors. An absolute expression of indicated immune cell markers by immunohistochemistry in sequential tumor biopsies was quantified before and after local ONCOS-102 treatment. All 12 patients treated in the study are presented. Each solid line indicates an individual patient. Dotted line indicates median

Fig. 4

Increased number of immune cells were detected by immunohistochemistry in tumors after ONCOS-102 treatment. A waterfall plot of indicated CD markers for all patients treated in the trial. Results are presented as the biggest logarithmic fold-change from baseline either 1 month or 2 months after treatment. Patient code is depicted in each column

Fig. 5

ONCOS-102 attracted CD8+ lymphocytes to tumors. A prominent infiltration of CD8+ T-cells was seen after treatment (lower row) in tumors showing very little CD8+ T-cells before treatment (upper row). Of note, patient FI1-15 showed infiltration of CD8+ immune cells to a non-injected distant tumor

Fig. 6

ONCOS-102 attracted macrophages and B cells to tumors. Infiltration of CD68+ (a), CD11c + (b) and CD19+ (c) immune cells in patients FI1-14 and FI1-19 was seen after treatment with ONCOS-102

Fig. 7

Increase in tumor-infiltrating immune cells following ONCOS-102 treatment is associated with increased survival. The fold change of total T cells (CD3+), CD8+ cells, CD68+ cells, CD163+ cells, and CD11c + cells correlated with overall survival in patients treated with ONCOS-102. Correlation between the post-treatment increase in different sub-populations of TILs and overall survival was assessed by Spearman’s rank correlation analysis. Overall survival is depicted as months, open label is patient FI1-19 who is still alive

Fig. 8

Intratumoral ONCOS-102 treatment induced systemic tumor-specific CD8+ T cell responses in chemotherapy refractory cancer patients. Systemic, tumor-specific CD8+ cellular response depicted in IFNγ ELISPOT. a Anti-MAGE-A3 ELISPOT for CD8+ cells in patients FI1-14 (lower row) and anti-mesothelin ELISPOT for CD8+ T cells for patient FI1 19 (upper row). b Numerical values for anti-MAGE-A3, anti-MAGE-A1 and anti-NY-ESO-1 (p157-165) ELISPOT for patient FI1-19. BL = baseline, pool1 = days 8–85 after treatment initiation, pool 2 = days 113–169 after treatment initiation. * = numerical values for anti-NY-ESO-1 (p91-110) ELISPOT at follow-up 17 months after the last ONCOS-102

Fig. 9

ONCOS-102 treatment induced up-regulation of PD-L1 in tumors. The increase in PD-L1 expression (a) coincided with an infiltration of CD8+ cells (Fig. 6) and an increase in gene expression of IFN-γ in tumors in mesothelioma patients FI1-14 and FI1-09 (b), suggesting induction of dynamic adaptive changes in response to T-cell-derived IFNγ