Novel chimeric antigen receptor-expressing T cells targeting the malignant mesothelioma-specific antigen sialylated HEG1.

The selection of highly specific target antigens is critical for the development of clinically efficient and safe chimeric antigen receptors (CARs). In search of diagnostic marker for malignant mesothelioma (MM), we have established SKM9-2 monoclonal antibody (mAb) which recognizes a MM-specific molecule, sialylated Protein HEG homolog 1 (HEG1), with high specificity and sensitivity. In this study, to develop a novel therapeutic approach against MM, we generated SKM9-2 mAb-derived CARs that included the CD28 (SKM-28z) or 4-1BB (SKM-BBz) costimulatory domain. SKM-28z CAR-T cells showed continuous growth and enhanced Tim-3, LAG-3, and PD-1 expression in vitro, which might be induced by tonic signaling caused by self-activation; however, these phenotypes were not observed in SKM-BBz CAR-T cells. In addition, SKM-BBz CAR-T cells exhibited slightly stronger in vitro killing activity against MM cell lines than SKM-28z CAR-T cells. More importantly, only SKM-BBz CAR-T cells, but not SKM-28z CAR-T cells, significantly inhibited tumor growth in vivo in a MM cell line xenograft mouse model. Gene expression profiling and reporter assays revealed differential signaling pathway activation; in particular, SKM-BBz CAR-T cells exhibited enhanced NF-kB signaling and reduced NFAT activation. In addition, SKM-BBz CAR-T cells showed upregulation of early memory markers, such as TCF7 and CCR7, as well as downregulation of pro-apoptotic proteins, such as BAK1 and BID, which may be associated with phenotypical and functional differences between SKM-BBz and SKM-28z CAR-T cells. In conclusion, we developed novel SKM9-2-derived CAR-T cells with the 4-1BB costimulatory domain, which could provide a promising therapeutic approach against refractory MM.

MMP1, IL-1ß, sTNFR-1, and IL-6 are prognostic factors for patients with unresectable or metastatic renal cell carcinoma treated with immune checkpoint inhibitors.

BACKGROUND: Few studies have reported reliable prognostic factors for immune checkpoint inhibitors (ICIs) in renal cell carcinoma (RCC). Therefore, we investigated prognostic factors in patients treated with ICIs for unresectable or metastatic RCC. METHODS: We included 43 patients who received ICI treatment for RCC between January 2018 and October 2021. Blood samples were drawn before treatment, and 73 soluble factors in the plasma were analyzed using a bead-based multiplex assay. We examined factors associated with progression-free survival (PFS), overall survival (OS), and immune-related adverse events (irAE) using the Chi-squared test, Kaplan-Meier method, and the COX proportional hazards model. RESULTS: Patients exhibited a median PFS and OS of 212 and 783 days, respectively. Significant differences in both PFS and OS were observed for MMP1 (PFS, p < 0.001; OS, p = 0.003), IL-1ß (PFS, p = 0.021; OS, p = 0.008), sTNFR-1 (PFS, p = 0.017; OS, p = 0.005), and IL-6 (PFS, p = 0.004; OS, p < 0.001). Multivariate analysis revealed significant differences in PFS for MMP1 (hazard ratio [HR] 5.305, 95% confidence interval [CI], 1.648-17.082; p = 0.005) and OS for IL-6 (HR 23.876, 95% CI, 3.426-166.386; p = 0.001). Moreover, 26 patients experienced irAE, leading to ICI discontinuation or withdrawal. MMP1 was significantly associated with irAE (p = 0.039). CONCLUSION: MMP1 may be associated with severe irAE, and MMP1, IL-1ß, sTNFR-1, and IL-6 could serve as prognostic factors in unresectable or metastatic RCC treated with ICIs. MMP1 and IL-6 were independent predictors of PFS and OS, respectively. Thus, inhibiting these soluble factors may be promising for enhancing antitumor responses in patients with RCC treated with ICIs.

A phase 1 trial of NY-ESO-1-specific TCR-engineered T-cell therapy combined with a lymph node-targeting nanoparticulate peptide vaccine for the treatment of advanced soft tissue sarcoma.

The efficacy of immune checkpoint inhibitors is limited in refractory solid tumors. T-cell receptor gene-modified T (TCR-T)-cell therapy has attracted attention as a new immunotherapy for refractory cold tumors. We first investigated the preclinical efficacy and mode of action of TCR-T cells combined with the pullulan nanogel:long peptide antigen (LPA) vaccine in a mouse sarcoma model that is resistant to immune checkpoint inhibition. Without lymphodepletion, the pullulan nanogel:LPA vaccine markedly increased the number of TCR-T cells in the draining lymph node and tumor tissue. This change was associated with enhanced CXCR3 expression in TCR-T cells in the draining lymph node. In the phase 1 trial, autologous New York esophageal squamous cell carcinoma 1 (NY-ESO-1)-specific TCR-T cells were infused twice into HLA-matched patients with NY-ESO-1+ soft tissue sarcoma (STS). The pullulan nanogel:LPA vaccine contains an epitope recognized by TCR-T cells, and it was subcutaneously injected 1 day before and 7 days after the infusion of TCR-T cells. Lymphodepletion was not performed. Three patients with refractory synovial sarcoma (SS) were treated. Two out of the three patients developed cytokine release syndrome (CRS) with low-to-moderate cytokine level elevation. We found obvious tumor shrinkage lasting for more than 2 years by tumor imaging and long-term persistence of TCR-T cells in one patient. In conclusion, NY-ESO-1-specific TCR-T-cell therapy plus vaccination with the pullulan nanogel carrying an LPA containing the NY-ESO-1 epitope without lymphodepletion is feasible and can induce promising long-lasting therapeutic effects in refractory SS (Registration ID: JMA-IIA00346).

Clinical roles of soluble PD-1 and PD-L1 in plasma of NSCLC patients treated with immune checkpoint inhibitors.

INTRODUCTION: Immune checkpoint inhibitors (ICIs) have significantly improved the prognosis of non-small cell lung cancer (NSCLC). However, only a limited proportion of patients can benefit from this therapy, and clinically useful predictive biomarkers remain to be elucidated. METHODS: Blood was collected from 189 patients with NSCLC before and six weeks after the initiation of ICI treatment (anti-PD-1 or anti-PD-L1 antibody). Soluble PD-1 (sPD-1) and PD-L1 (sPD-L1) in plasma before and after treatment were analyzed to evaluate their clinical significance. RESULTS: Cox regression analysis demonstrated that higher sPD-L1 levels before treatment significantly predicted unfavorable progression-free survival (PFS; HR 15.4, 95% CI 1.10-86.7, P = 0.009) and overall survival (OS; HR 11.4, 95% CI 1.19-52.3, P = 0.007) in NSCLC patients treated with ICI monotherapy (n = 122) but not in those treated with ICIs combined with chemotherapy (n = 67: P = 0.729 and P = 0.155, respectively). In addition, higher sPD-1 levels after treatment were significantly associated with better OS (HR 0.24, 95% CI 0.06-0.91, P = 0.037) in patients treated with anti-PD-1 monotherapy, whereas higher sPD-L1 levels after treatment were significantly associated with worse PFS (HR 6.09, 95% CI 1.42-21.0, P = 0.008) and OS (HR 42.6, 95% CI 6.83-226, P < 0.001). The levels of sPD-L1 at baseline closely correlated with those of other soluble factors, such as sCD30, IL-2Ra, sTNF-R1, and sTNF-R2, which are known to be released from the cell surface by zinc-binding proteases ADAM10/17. CONCLUSIONS: These findings suggest the clinical significance of pretreatment sPD-L1 as well as posttreatment sPD-1 and sPD-L1 in NSCLC patients treated with ICI monotherapy.

Exhaustion of CAR T cells: potential causes and solutions.

Chimeric antigen receptor (CAR) T cell therapy has attracted attention for its promising therapeutic effects on hematological malignancies. However, there are problems such as relapse during long-term follow-up and limited effect on solid tumors with this therapy. Exhaustion, which impairs in vivo persistence and killing activity of CAR T cells, is one of the causes of these issues. Depending on their structure of extracellular portion, some CARs induce tonic signals in the absence of ligand stimulation and induce exhaustion phenotype in CAR T cells. Analysis of these self-activating CARs is expected to provide key information for understanding and resolving CAR T cell exhaustion. In this review, we introduced examples of self-activating CARs and summarized their phenotypes to figure out how CAR T cell exhaustion occurs. Further, we aimed to review promising solutions to the CAR T cell exhaustion that hampers generalized application of CAR T cell therapy.

Evaluation of X-ray and carbon-ion beam irradiation with chemotherapy for the treatment of cervical adenocarcinoma cells in 2D and 3D cultures.

BACKGROUND: Cervical cancer is the second most common cancer in women and causes more than 250,000 deaths worldwide. Among these, the incidence of cervical adenocarcinomas is increasing. Cervical adenocarcinoma is not only difficult to detect and prevent in the early stages with screening, but it is also resistant to chemotherapy and radiotherapy, and its prognosis worsens significantly as the disease progresses. Furthermore, when recurrence or metastasis is observed, treatment options are limited and there is no curative treatment. Recently, heavy-particle radiotherapy has attracted attention owing to its high tumor control and minimal damage to normal tissues. In addition, heavy particle irradiation is effective for cancer stem cells and hypoxic regions, which are difficult to treat. METHODS: In this study, we cultured cervical adenocarcinoma cell lines (HeLa and HCA-1) in two-dimensional (2D) or three-dimensional (3D) spheroid cultures and evaluated the effects of X-ray and carbon-ion (C-ion) beams. RESULTS: X-ray irradiation decreased the cell viability in a dose-dependent manner in 2D cultures, whereas this effect was attenuated in 3D spheroid cultures. In contrast, C-ion irradiation demonstrated the same antitumor effect in 3D spheroid cultures as in 2D cultures. In 3D spheroid cultures, X-rays and anticancer drugs are attenuated because of hypoxia inside the spheroids. However, the impact of the C-ion beam was almost the same as that of the 2D culture, because heavy-particle irradiation was not affected by hypoxia. CONCLUSION: These results suggest that heavy-particle radiotherapy may be a new therapeutic strategy for overcoming the resistance of cervical adenocarcinoma to treatment.

Clinical significance of peripheral TCR and BCR repertoire diversity in EGFR/ALK wild-type NSCLC treated with anti-PD-1 antibody.

INTRODUCTION: TCR and BCR repertoire diversity plays a critical role in tumor immunity. Thus, analysis of TCR and BCR repertoires might help predict the clinical efficacy of anti-PD-1 treatment. METHODS: Blood samples from 30 patients with non-small cell lung cancer (NSCLC) treated with anti-PD-1 antibody were collected before and six weeks after treatment initiation. The clinical significance of TCR and BCR repertoire diversity in peripheral blood was evaluated in all the enrolled patients (n = 30) or in the subset with (n = 10) or without (n = 20) EGFR/ALK mutation. RESULTS: TCR and BCR diversity was significantly correlated at baseline (R = 0.65; P = 1.6 × 10-4) and on treatment (R = 0.72; P = 1.2 × 10-5). Compared to non-responders (SD or PD), responders (PR) showed significantly decreased TCR and BCR diversity after treatment in the EGFR/ALK wild-type subset (P = 0.0014 and P = 0.034, respectively), but not in all the enrolled patients. The post-treatment reduction in TCR and BCR repertoire diversity was also significantly associated with the occurrence of adverse events in the EGFR/ALK wild-type subset (P = 0.022 and P = 0.014, respectively). Patients with more reduced TCR diversity showed better progression-free survival (PFS) in the EGFR/ALK wild-type subset (P = 0.011) but not in the mutant subset. CONCLUSIONS: These findings suggest the clinical significance of changes in peripheral TCR and BCR repertoire diversity after anti-PD-1 treatment in patients with NSCLC without EGFR/ALK mutation. Monitoring of the peripheral TCR and BCR repertoires may serve as a surrogate marker for the early detection of EGFR/ALK wild-type NSCLC patients who would benefit from anti-PD-1 treatment.

Galectin-9 expression as a poor prognostic factor in patients with renal cell carcinoma.

Recently, the effectiveness of anti-programmed death 1 (PD-1) antibody therapy in the treatment of renal cell carcinoma (RCC) has been established. Nevertheless, efficacy has been reported to be limited to only 10-30% of patients. To develop more effective immunotherapy for RCC, we analyzed the immunological characteristics in RCC tissues by immunohistochemistry (IHC). We prepared a tissue microarray that consisted of tumor tissue sections (1 mm in diameter) from 83 RCC patients in Kanagawa Cancer Center between 2006 and 2015. IHC analysis was performed with antibodies specific to immune-related (CD8 and Foxp3) and immune checkpoint (programmed death ligand 1 (PD-L1) and 2 (PD-L2), B7-H4 and galectin-9) molecules. The numbers and proportions of positively stained tumor cells or immune cells were determined in each section. From multivariate analysis of all 83 patients, higher galectin-9 expression was detected as a factor associated with worse overall survival (OS) (P = 0.029) and that higher stage and higher B7-H4 expression were associated with worse progression-free survival (PFS) (P < 0.001 and P = 0.021, respectively). Similarly, in multivariate analysis of 69 patients with clear cell RCC, though not statistically significant, there was a trend for association between higher galectin-9 expression and worse OS (P = 0.067), while higher stage was associated with worse PFS (P < 0.001). This study suggests that higher galectin-9 expression is an independent adverse prognostic factor of OS in RCC patients. Therefore, to develop more effective personalized immunotherapy to treat RCC, it may be important to target not only PD-1/PD-L1, but also other immune checkpoint molecules such as galectin-9.

Mixed 20-peptide cancer vaccine in combination with docetaxel and dexamethasone for castration-resistant prostate cancer: a randomized phase II trial.

A novel cancer vaccine consisting of 20 mixed peptides (KRM-20) was designed to induce cytotoxic T lymphocytes (CTL) against twelve different tumor-associated antigens. The aim of this phase II trial was to examine whether KRM-20 in combination with docetaxel and dexamethasone enhances the antitumor effects in patients with castration-resistant prostate cancer (CRPC). In this double-blind, placebo-controlled, randomized phase II study, we enrolled chemotherapy-naïve patients with CRPC from ten medical centers in Japan. Eligible patients were randomly assigned 1:1 centrally to receive either KRM-20 combined with docetaxel and dexamethasone (n = 25) or placebo with docetaxel and dexamethasone (n = 26). The primary endpoint was the difference in prostate-specific antigen (PSA) decline between each treatment. The rates of > 50% PSA decline in the two arms were similar (56.5% versus 53.8%; P = 0.851). Human leukocyte antigen (HLA)-matched peptide-specific immunoglobulin G (P = 0.018) and CTL (P = 0.007) responses in the KRM-20 arm significantly increased after treatment. The addition of KRM-20 did not increase toxicity. There were no between-group differences in progression-free or overall survival (OS). The addition of KRM-20 was safe, and similar PSA decline and HLA-matched peptide-specific CTL and IgG responses increased in combination with docetaxel and dexamethasone in CRPC patients. Subgroup analysis suggested that this treatment is favorable for CRPC patients with ≥ 26% lymphocytes or PSA levels of < 11.2 ng/ml, but further clinical trials comparing OS are required.

Association between soluble immune mediators and tumor responses in patients with nonsmall cell lung cancer treated with anti-PD-1 inhibitor.

Although programmed death (PD)-1 immune checkpoint therapies target the immune system, the relationship between inflammatory factors and the clinical outcome of anti-PD-1 therapy for nonsmall cell lung cancer (NSCLC) is not fully understood. Here we examined the association between soluble immune mediators and the outcome of treatment with PD-1 inhibitors in patients with advanced/recurrent NSCLC. In two independent cohorts, we assessed the levels of 88 different soluble immune mediators in peripheral blood before and after anti-PD-1 treatment, and evaluated their associations with clinical outcomes. In the training cohort, the plasma levels of chitinase 3-like-1 and GM-CSF before treatment (p = 0.006 and p = 0.005, respectively) and changes in the plasma levels of CXCL2, VEGF, IFNα2, and MMP2 after treatment (p < 0.001, p = 0.019, p = 0.019, and p = 0.012, respectively) were significantly correlated with PFS. The change in the plasma CXCL2 level was also significantly associated with treatment-related AEs (p = 0.017). In the validation cohort, however, only the changes in the plasma levels of CXCL2 and MMP2 after treatment were associated with PFS (p = 0.003 and p = 0.006, respectively), and these changes were maintained during the course of anti-PD-1 therapy in patients who showed better clinical outcomes, even in those with tumor pseudoprogression. Since CXCL2 and MMP2 can be easily measured by minimally invasive blood sampling, they could be useful for monitoring of clinical outcomes in NSCLC patients receiving PD-1 inhibitor therapy.

Heat shock protein 105 peptide vaccine could induce antitumor immune reactions in a phase I clinical trial.

Heat shock protein 105 (HSP105) is overexpressed in many cancers, including colorectal cancer (CRC) and esophageal cancer (EC). We carried out a phase I clinical trial of HLA-A24- and HLA-A2-restricted HSP105 peptide vaccines in patients with CRC or EC. In this additional study of the trial, we examined the immunological efficacy of the novel vaccine. Thirty patients with advanced CRC or EC underwent HSP105 peptide vaccination. Immunological responses were evaluated by ex vivo and in vitro γ-interferon enzyme-linked immunospot assays and their correlation with patients' prognosis was analyzed. The HSP105 peptide vaccines induced peptide-specific CTLs in 15 of 30 patients. Among HLA-A24 patients (n = 15), 7 showed induction of CTLs only ex vivo, whereas among HLA-A2 patients (n = 15), 4 showed the induction ex vivo and 6 in vitro. Heat shock protein 105-specific CTL induction correlated with suppression of cancer progression and was revealed as a potential predictive biomarker for progression-free survival (P = .008; hazard ratio = 3.03; 95% confidence interval, 1.34-6.85) and overall survival (P = .025; hazard ratio = 2.72; 95% confidence interval, 1.13-6.52). Production of cytokines by HSP105 peptide-specific CTLs was observed at the injection sites (skin) and tumor tissues, suggesting that HSP105-specific CTLs not only accumulated at vaccination sites but also infiltrated tumors. Furthermore, we established 2 HSP105 peptide-specific CTL clones, which showed HSP105-specific cytokine secretion and cytotoxicity. Our results suggest that the HSP105 peptide vaccine could induce immunological effects in cancer patients and improve their prognosis.

[Translational Research in Immuno-Oncology - Comprehensive Analysis of Phenotypes and Functions of Various Immune Cells Using the Colorectal Cancer Surgical Sample].

Colorectal cancer(CRC)is one of the increasing cancers, and development of novel treatments is imperative for advanced CRC. In recent years, immune checkpoint inhibitors have demonstrated impressive clinical efficacy in various types of cancers, but only limited clinical responses were reported in CRC. It has been reported that such poor therapeutic effects might be possibly due to immune suppressive mechanisms other than immune checkpoints in the CRC. Therefore, comprehensive grasp of the immune environment is considered to be of significance for CRC patients. Our study aims to comprehensively assess the phenotypes and functions of various immune cells isolated from various tissues, including primary tumors and related lymph nodes, in primary CRC patients. Our preliminary results by flow cytometry analysis suggest that the immune suppression, particularly in regional lymph nodes, may be related to tumor progression. Further studies remain to be performed to more thoroughly elucidate immune suppressive mechanisms, and thereby to develop a novel immunotherapeutic strategy in the CRC.

Feasibility study of personalized peptide vaccination for hepatocellular carcinoma patients refractory to locoregional therapies.

Overall survival of patients with hepatocellular carcinoma (HCC) refractory to locoregional therapy is dismal, even following treatment with sorafenib, a multikinase inhibitor. To develop a more efficacious treatment, we undertook a feasibility study of personalized peptide vaccination (PPV) for HCC, in which the peptides were selected from 31 peptide candidates based on the pre-existing immunity. Twenty-six HCC patients refractory to locoregional therapies (cohort 1) and 30 patients refractory to both locoregional and systemic therapies (cohort 2) were entered into the study. There were no severe adverse events related to PPV except for one injection site reaction. At the end of the first cycle of six vaccinations, successful CTL or IgG boosting was observed in 57% or 46% of patients in cohort 1 and in 54% or 52% of patients in cohort 2, respectively. Successful IgG boosting at the end of the second cycle was observed in the majority of patients tested. Median overall survival was 18.7 months (95% confidence interval, 12.2-22.5 months) in cohort 1, and 8.5 months (95% confidence interval, 5.9-12.2 months) in cohort 2. Based on the higher rates of immune boosting and the safety profile of PPV, further clinical studies of PPV would be warranted for patients with HCC refractory to not only locoregional therapy but also both locoregional and systemic therapies. The protocol of this study was registered with the UMIN Clinical Trials Registry (UMIN000001882 and UMIN000003590).

A randomized phase II trial of personalized peptide vaccine with low dose cyclophosphamide in biliary tract cancer.

Since the prognosis of advanced biliary tract cancer (aBTC) still remains very poor, new therapeutic approaches, including immunotherapies, need to be developed. In the current study, we conducted an open-label randomized phase II study to test whether low dose cyclophosphamide (CPA) could improve antigen-specific immune responses and clinical efficacy of personalized peptide vaccination (PPV) in 49 previously treated aBTC patients. Patients with aBTC refractory to at least one regimen of chemotherapies were randomly assigned to receive PPV with low dose CPA (100 mg/day for 7 days before vaccination) (PPV/CPA, n = 24) or PPV alone (n = 25). A maximum of four HLA-matched peptides were selected based on the pre-existing peptide-specific IgG responses, followed by subcutaneous administration. T cell responses to the vaccinated peptides in the PPV/CPA arm tended to be greater than those in the PPV alone arm. The PPV/CPA arm showed significantly better progression-free survival (median time: 6.1 vs 2.9 months; hazard ratio (HR): 0.427; P = 0.008) and overall survival (median time: 12.1 vs 5.9 months; HR: 0.376; P = 0.004), compared to the PPV alone arm. The PPV alone arm, but not the PPV/CPA arm, showed significant increase in plasma IL-6 after vaccinations, which might be associated with inhibition of antigen-specific T cell responses. These results suggested that combined treatment with low dose CPA could provide clinical benefits in aBTC patients under PPV, possibly through prevention of IL-6-mediated immune suppression. Further clinical studies would be recommended to clarify the clinical efficacy of PPV/CPA in aBTC patients.

Personalized peptide vaccination as second-line treatment for metastatic upper tract urothelial carcinoma.

This study investigated the applicability of personalized peptide vaccination (PPV) for patients with metastatic upper tract urothelial cancer (mUTUC) after failure of platinum-based chemotherapy. In this single arm, open-label, phase II clinical trial, patients with mUTUC received PPV at a single institution. Personalized peptide vaccination treatment used a maximum of four peptides chosen from 27 candidate peptides according to human leukocyte antigen types and peptide-reactive IgG titers, for six s.c. injections weekly as one cycle. The safety of PPV, as well as its influence on host immunity and effect on overall survival were assessed. Forty-eight patients were enrolled in this study. Personalized peptide vaccinations were well tolerated without severe adverse events. Median survival time was 7.3 months (95% confidence interval [CI], 5.3-13.1) with 13.0 months for patients receiving combined salvage chemotherapy (95% CI, 5.7-17.5) and 4.5 months for patients receiving PPV alone (95% CI, 1.7-10.1) (P = 0.080). Patients with positive CTL responses showed a significantly longer survival than patients with negative CTL responses (hazard ratio, 0.37; 95% CI, 0.16-0.85; P = 0.019). Multivariate Cox regression analysis showed that lower numbers of Bellmunt risk factors and lower levels of B-cell activating factor were significantly associated with favorable overall survival for patients under PPV treatment. This study indicated that PPV for patients with mUTUC after failure of platinum-based chemotherapy induced substantial peptide-specific CTL responses without severe adverse events and has the potential to prolong survival when combined with salvage chemotherapy. UMIN Clinical Trials Registry ID: 000001854.

Immunological evaluation of peptide vaccination for cancer patients with the HLA -A11+ or -A33+ allele.

The HLA-A11 or -A33 allele is found in approximately 18% or 10% of the Asian population, respectively, but each of which is a minor allele worldwide, and therefore no clinical trials were previously conducted. To develop a therapeutic peptide vaccine for each of them, we investigated immunological responses of advanced cancer patients with the HLA-A11+ /A11+ (n = 18) or -A33+ /A33+ (n = 13) allele to personalized peptide vaccine (PPV) regimens. The primary sites of HLA-A11+/A11+ or -A33+/A33+ patients were the colon (n = 4 or 2), stomach (2 or 3), breast (3 or 2), lung and pancreas (2 or 2), and so on. For PPV, a maximum of four peptides were selected from nine different peptides capable of binding to HLA-A11 and -A33 molecules based on the pre-existing peptide-specific IgG responses. There were no severe adverse events related to PPV. At the end of the first cycle, peptide-specific CTL responses were augmented in 4/12 or 2/9 of HLA-A11+ /A11+ or -A33+ /A33+ patients, while peptide-specific IgG responses were augmented in 6/14 or 4/10 patients, respectively. Clinical responses consisted of four stable diseases and 14 progressive diseases in HLA-A11+ /A11+ patients, versus seven and six in -A33+ /A33+ patients, respectively. Further clinical study of PPV could be recommended because of the safety and positive immunological responses.

Cancer immunotherapy targeting neoantigens derived from tumor-specific gene mutations.

Cancer immunotherapies targeting "tumor-associated antigens" derived from wild-type proteins have shown limited success in clinical trials to date. Recent development of next generation sequencing and bioinformatics technology has allowed identification of "neoanti- gens" derived from genetic alterations, such as mutations, insertions, and deletions, re- stricted to tumor cells. Tumor-specific neoantigens, but not tumor-associated antigens, can be recognized as "foreign" by the host immune system. Therefore, they might show higher immunogenicity and more efficiently activate anti-tumor immune responses capable of con- trolling tumor burden. In this review article, I have summarized and discussed clinical signifi- cance of tumor-specific neoantigens and their potential clinical application for personalized cancer immunotherapies.

Phase I study of a new cancer vaccine of ten mixed peptides for advanced cancer patients.

A phase I study of a new cancer vaccine (KRM-10), consisting of a mixture of 10 different short peptides, was conducted for patients with advanced gastrointestinal cancers. Primary or secondary endpoints included the dose-limiting toxicity (DLT), or safety and immune responses, respectively. Peptide-specific cytotoxic T lymphocytes (CTL) and immunoglobulin G (IgG), together with soluble inflammatory factors, were measured before and after vaccination. Twenty-one patients were vaccinated with KRM-10 at dose levels of 10 (n = 6), 20 (n = 8) or 30 mg (n = 7) of peptides every week for 6 weeks. No DLT were observed in the dose range evaluated. Common treatment-related adverse events were a grade 1 injection site reaction in 15 patients, and fever in three patients (grade 1 in two patients and grade 2 in one patient). CTL activity to at least one peptide at the time of the third and sixth vaccination increased in 2 and 3 of 6 (10 mg), 2 of 8 and 4 of 6 (20 mg), or 2 and 1 of 6 (30 mg) patients, respectively. IgG levels, at the third and sixth vaccination, were also increased in 1 and 1 of 6 (10 mg), 2 of 8 and 4 of 6 (20 mg), or 1 and 3 of 6 (30 mg) patients, respectively. The KRM-10 vaccine consisting of 20 mg of peptides was determined as the optimal dose for a coming phase II trial because of its safety, and also for demonstrating the most potent activity for augmenting the immune response of the three doses tested. This trial was registered at the UMIN Clinical Trials Registry as UMIN000008820.

A randomized phase II clinical trial of personalized peptide vaccination with metronomic low-dose cyclophosphamide in patients with metastatic castration-resistant prostate cancer.

This study investigated the effect of metronomic cyclophosphamide (CPA) in combination with personalized peptide vaccination (PPV) on regulatory T cells (Treg) and myeloid-derived suppressor cells (MDSC), and whether it could improve the antitumor effect of PPV. Seventy patients with metastatic castration-resistant prostate cancer were randomly assigned (1:1) to receive PPV plus oral low-dose CPA (50 mg/day), or PPV alone. PPV treatment used a maximum of four peptides chosen from 31 pooled peptides according to human leukocyte antigen types and antigen-specific humoral immune responses before PPV, for 8 subcutaneous weekly injections. Peptide-specific cytotoxic T lymphocyte (CTL) and immunoglobulin G responses were measured before and after PPV. The incidence of grade 3 or 4 hematologic adverse events was higher in the PPV plus CPA arm than in the PPV alone arm. Decrease in Treg and increase in MDSC were more pronounced in PPV plus CPA treatment than in PPV alone (p = 0.036 and p = 0.048, respectively). There was no correlation between the changes in Treg or MDSC and CTL response. There was no difference in positive immune responses between the two arms, although overall survival in patients with positive immune responses was longer than in those with negative immune responses (p = 0.001). Significant differences in neither progression-free survival nor overall survival were observed between the two arms. Low-dose CPA showed no change in the antitumor effect of PPV, possibly due to the simultaneous decrease in Treg and increase in MDSC, in patients under PPV.