Thierry Dorval

BACKGROUND: DC derived-exosomes are nanomeric vesicles harboring functional MHC/peptide complexes capable of promoting T cell immune responses and tumor rejection. Here we report the feasability and safety of the first Phase I clinical trial using autologous exosomes pulsed with MAGE 3 peptides for the immunization of stage III/IV melanoma patients. Secondary endpoints were the monitoring of T cell responses and the clinical outcome. PATIENTS AND METHODS: Exosomes were purified from day 7 autologous monocyte derived-DC cultures. Fifteen patients fullfilling the inclusion criteria (stage IIIB and IV, HLA-A1+, or -B35+ and HLA-DPO4+ leukocyte phenotype, tumor expressing MAGE3 antigen) were enrolled from 2000 to 2002 and received four exosome vaccinations. Two dose levels of either MHC class II molecules (0.13 versus 0.40 x 1014 molecules) or peptides (10 versus 100 mug/ml) were tested. Evaluations were performed before and 2 weeks after immunization. A continuation treatment was performed in 4 cases of non progression. RESULTS: The GMP process allowed to harvest about 5 x 1014 exosomal MHC class II molecules allowing inclusion of all 15 patients. There was no grade II toxicity and the maximal tolerated dose was not achieved. One patient exhibited a partial response according to the RECIST criteria. This HLA-B35+/A2+ patient vaccinated with A1/B35 defined CTL epitopes developed halo of depigmentation around naevi, a MART1-specific HLA-A2 restricted T cell response in the tumor bed associated with progressive loss of HLA-A2 and HLA-BC molecules on tumor cells during therapy with exosomes. In addition, one minor, two stable and one mixed responses were observed in skin and lymph node sites. MAGE3 specific CD4+ and CD8+ T cell responses could not be detected in peripheral blood. CONCLUSION: The first exosome Phase I trial highlighted the feasibility of large scale exosome production and the safety of exosome administration.

BACKGROUND: The clinicopathologic features of infiltrating lobular carcinoma (ILC), which represents 5% to 15% of all breast cancers, are still controversial. In particular, the high frequency of multicentric lesions has led to questioning of the effectiveness of conservative treatment for this type of cancer. By studying a large number of cases, we aimed to compare the clinicopathological features of ILC with those of nonlobular infiltrating carcinoma (NLIC) and to assess the advisability of conservative therapy in the management of ILC. METHODS: The population analyzed included 726 cases of ILC, 249 cases of mixed ILC/invasive ductal carcinoma (ILC/IDC), and 10,061 cases of NLIC. The age of patients, TNM status, estrogen- and progesterone-receptor status (ER, PR), and histologic grades of the 3 groups were compared. The follow-up was carried out on a subgroup of 5846 cases. RESULTS: At diagnosis, ILC tumors were found to be larger on average and were detected in patients older than those with NLIC, but the degree of lymph node involvement was lower in patients with ILC than in NLIC. In ILC, tumors are more frequently grade I and ER-positive than in NLIC. Multicentric lesions were not significantly more frequent in ILC than in NLIC. The overall survival, locoregional control, disease free interval, and metastatic spread rates were not different among the three groups neither by univariate nor multivariate analysis, but the pattern of metastatic dissemination was different. In 480 cases of ILC considered for conservation therapy, the local recurrence and overall survival rates were similar to those observed for IDC. CONCLUSIONS: Our analysis specifies the clinicopathological features of ILC and confirms that conservation therapy may be an appropriate treatment for this type of cancer.

PURPOSE: Active immunization against the tumor-specific MAGE-A3 antigen is followed by a few but impressive and durable clinical responses. This randomized phase II trial evaluated two different immunostimulants combined with the MAGE-A3 protein to investigate whether a more robust and persistent immune response could be associated with increased clinical benefit. PATIENTS AND METHODS: Patients with MAGE-A3-positive stage III or IV M1a melanoma were randomly assigned to receive the MAGE-A3 protein combined either with AS02B or with AS15 immunostimulant. Clinical end points were toxicity and rates of objective clinical responses, progression-free survival (PFS), and overall survival (OS). RESULTS: Seventy-five patients were treated, with 36 eligible patients per arm. Both treatments were well tolerated. In the AS15 arm, four objective responses were observed (three complete responses and one partial response) versus one partial response in the AS02B arm. In the AS15 and AS02B arms, the PFS rates after 6 months were 25% and 14%, respectively; and the median OS times were 33 months and 19.9 months, respectively, with a median observation period of 48 months. Antibodies against MAGE-A3, found in all patients, showed three-fold higher titers in the AS15 arm. The anti-MAGE-A3 cellular response was also more pronounced in the AS15 arm. CONCLUSION: In the MAGE-A3+AS15 arm, clinical activity was higher and the immune response more robust. Therefore, the AS15 immunostimulant was selected for combination with the MAGE-A3 protein in phase III trials.

Vaccination of melanoma patients with tumor-specific antigens recognized by cytolytic T lymphocytes (CTL) produces significant tumor regressions in a minority of patients. These regressions appear to occur in the absence of massive CTL responses. To detect low-level responses, we resorted to antigenic stimulation of blood lymphocyte cultures in limiting dilution conditions, followed by tetramer analysis, cloning of the tetramer-positive cells, and T-cell receptor (TCR) sequence analysis of the CTL clones that showed strict specificity for the tumor antigen. A monoclonal CTL response against a MAGE-3 antigen was observed in a melanoma patient, who showed partial rejection of a large metastasis after treatment with a vaccine containing only the tumor-specific antigenic peptide. Tetramer analysis after in vitro restimulation indicated that about 1/40,000 postimmunization CD8(+) blood lymphocytes were directed against the antigen. The same TCR was present in all of the positive microcultures. TCR evaluation carried out directly on blood lymphocytes by PCR amplification led to a similar frequency estimate after immunization, whereas the TCR was not found among 2.5 x 10(6) CD8(+) lymphocytes collected before immunization. Our results prove unambiguously that vaccines containing only a tumor-specific antigenic peptide can elicit a CTL response. Even though they provide no information about the effector mechanisms responsible for the observed reduction in tumor mass in this patient, they would suggest that low-level CTL responses can initiate tumor rejection.