Immune adjuvant therapy using Bacillus Calmette-Guérin cell wall skeleton (BCG-CWS) in advanced malignancies: A phase 1 study of safety and immunogenicity assessments

Abstract

The cell wall skeleton of Bacillus Calmette-Guérin (BCG-CWS) is a bioactive component that is a strong immune adjuvant for cancer immunotherapy. BCG-CWS activates the innate immune system through various pattern recognition receptors and is expected to elicit antigen-specific cellular immune responses when co-administered with tumor antigens. To determine the recommended dose (RD) of BCG-CWS based on its safety profile, we conducted a phase I dose-escalation study of BCG-CWS in combination with WT1 peptide for patients with advanced cancer.The primary endpoint was the proportion of treatment-related adverse events (AEs) at each BCG-CWS dose. The secondary endpoints were immune responses and clinical effects. A BCG-CWS dose of 50, 100, or 200 μg/body was administered intradermally on days 0, 7, 21, and 42, followed by 2 mg of WT1 peptide on the next day. For the escalation of a dose level, 3 + 3 design was used.Study subjects were 18 patients with advanced WT1-expressing cancers refractory to standard anti-cancer therapies (7 melanoma, 5 colorectal, 4 hepatobiliary, 1 ovarian, and 1 lung). Dose-limiting toxicity occurred in the form of local skin reactions in 2 patients at a dose of 200 μg although no serious treatment-related systemic AEs were observed. Neutrophils and monocytes transiently increased in response to BCG-CWS. Some patients demonstrated the induction of the CD4 T cell subset and its differentiation from the naïve to memory phenotype, resulting in a tumor response.The RD of BCG-CWS was determined to be 100 μg/body. This dose was well tolerated and showed promising clinical effects with the induction of an appropriate immune response.

Figure 1

Study schedule and study profile. A, Schedule of the study treatment and immunological assessments during the study treatment phase. B, Study profile of the dose-escalation portion (left) and the extended portion (right) of the study.

Figure 2

Local skin reactions at vaccine sites. A, Typical skin reactions according to BCG-CWS dose. B, Comparison of the size of induration with each BCG-CWS dose. C, Comparison of the size of ulceration with each BCG-CWS dose.

Figure 3

Dynamic changes in immune-related cells (1). A, B, Dynamic changes in absolute neutrophil counts in all patients and individual cases. C, D, Dynamic changes in absolute monocyte counts in all patients and individual cases. E, F, Dynamic changes in absolute lymphocyte counts in all patients and individual cases. In the line graphs, each color represents the same case in all panels. Peripheral blood samples were collected before (pre) and 24 to 48 hours after (post) the administration of BCG-CWS. Abbreviation: ns, not significant.

Figure 4

Dynamic changes in immune-related cells (2). A, Dynamic changes in percentages of CD4⁺ T cell in total lymphocytes in all patients (left) and individual cases (right). B, Frequencies of CD4⁺ T cell immunological phenotypes in individual cases. C, Dynamic changes in percentages of CD8⁺ T cells in total lymphocytes in all patients (left) and individual cases (right). D, Frequencies of CD8⁺ T cell immunological phenotypes in individual cases. In the line graphs, each color represents the same case in all panels. Peripheral blood mononuclear cells were collected before (baseline) and 1 or 2 months after the beginning of the study treatment. CM = central memory, EM = effector memory.

Figure 5

Tumor-associated antigen (TAA)-specific immune response. A, Dynamic changes in percentage of WT1-specific CTLs in total CD8⁺ T cells (%WT1-CTLs) in all patients (left) and individual cases (right). B, Fold-increase in %WT1-CTLs after the study treatment. Left and right graphs represent DTH-positive and DTH-negative patients, respectively. Peripheral blood mononuclear cells were collected before (baseline) and 1 or 2 months after the beginning of the study treatment. CTLs = cytotoxic T lymphocytes, DTH = delayed-type hypersensitivity, WT1 = Wilms’ tumor gene 1.

Figure 6

Clinical course and immunological monitoring in one case (#203). A, Chest computed tomography (CT) scan and chest X-ray radiograph (Chest-Xp) before and after the study treatment. Upper, intrapulmonary metastatic lesion; Middle, pleural disseminated lesions; Bottom, pleural effusion. B, Immunological assessment during the study treatment. (Left) Neutrophil and monocyte counts. Blue and red lines represent neutrophil and monocyte counts, respectively. (Right) CD4⁺ T cells. Black line represents %CD4⁺ T cells. Bar graph indicates immunological phenotypes of CD4⁺ T cells. Blue, red, orange, and green columns represent naïve, central memory (CM), effector memory (EM), and effector CD4⁺ T cells, respectively.