Seven immunocompetent, revaccinated patients with surgically incurable cutaneous melanoma underwent treatment of dermal and/or subcutaneous metastases with twice-weekly intratumoral injections of escalating doses (10 4 Ϫ2 ϫ 10 7 plaque-forming units (PFU)/lesion; 10 4 Ϫ8 ϫ 10 7 PFU/session) of a vaccinia/GM-CSF recombinant virus for 6 weeks. Patients with stable or responding disease were maintained on treatment until tumor resolution or progression. Systemic toxicity was infrequent, dose-related, and limited to mild flu-like symptoms that resolved within 24 hours. Local inflammation, at times with pustule formation, was consistently seen with doses of Ն10 7 PFU/lesion. Chronically treated lesions showed a dense infiltration, with CD4 ϩ and CD8 ϩ lymphocytes, histiocytes, and eosinophils. All seven patients developed an antivaccinia humoral immune response 14 -21 days following revaccination. Despite the presence of these antivaccinia antibodies, the reporter gene was expressed, as judged by the development of anti-␤-galactosidase antibodies in all patients. Passenger cytokine gene function was evidenced by the presence of virally encoded GM-CSF mRNA at injection sites both early (weeks 1 and 5) and late (week 31) in the course of treatment. Eosinophilia at treatment sites indicated that physiologically significant levels of functional cytokine were generated. However, there were no changes in the total number of peripheral white blood cells or in the numbers or percentages of polymorphonuclear leukocytes, monocytes, or eosinophils. GM-CSF was not detected in the sera. The two patients with the largest tumor burdens failed to respond even at treatment sites. Three patients had mixed responses, with regression of treated and untreated dermal metastases and progression of disease elsewhere. One patient had a partial response, with regression of injected and uninjected regional dermal metastases. Residual melanoma was excised, rendering the patient disease free. One patient with only dermal metastases confined to the scalp achieved a complete remission. Sequential administration of escalating doses of a GM-CSF recombinant vaccinia virus is safe, effective at maintaining passenger gene function, and can induce tumor regression.

IL-10 is an immunomodulatory cytokine that is frequently upregulated in various types of cancer. The biological role of IL-10 in cancer is quite complex; however, the presence of IL-10 in advanced metastases and the positive correlation between serum IL-10 levels and progression of disease indicates a critical role of IL-10 in the tumor microenvironment. IL-10 has been shown to directly affect the function of antigen-presenting cells by inhibiting the expression of MHC and costimulatory molecules, which in turn induces immune suppression or tolerance. Additionally, IL-10 downregulates the expression of Th1 cytokines and induces T-regulatory responses. Taken together, a combination of IL-10 antagonism and immunostimulatory treatments such as cancer vaccines, Toll-like receptor agonists, Th1 cytokines, and chemokines would be a logical approach to enhance an antitumor immune response.

We treated 64 patients with metastatic melanoma using a melanoma vaccine preceded by low-dose cyclophosphamide (CY), and monitored immunologic effects and antitumor activity. On day 0, the patients were given CY 300 mg/m2 intravenously. Three days later, they were injected intradermally with vaccine consisting of 10 to 25 x 10(6) autologous, enzymatically dissociated, cryopreserved, irradiated (25 Gy) tumor cells mixed with bacillus Calmette-Guérin (BCG). This treatment sequence was repeated every 28 days. Of 40 assessable patients with measurable metastases, five had responses, four complete and one partial, with a median duration of 10 months (7 to 84+ months). In six additional patients, we observed an antitumor response that seems to be peculiar to this vaccine therapy: the regression of metastatic lesions that appeared after the immunotherapy was begun. Delayed-type hypersensitivity (DTH) to autologous, mechanically dissociated melanoma cells that had not been exposed to extraneous antigens, such as enzymes or fetal calf serum, increased significantly following immunotherapy (day 0 v day 49, P less than .001; day 0 v day 161, P less than .001; day 0 v day 217, P = .021). Antitumor responses to the vaccine were strongly associated with DTH, as indicated by three observations: (1) eight of 10 patients who exhibited tumor regression had positive DTH, (2) in postsurgical adjuvant patients, there was a highly significant linear relationship (P less than .001) between the intensity of DTH to autologous melanoma cells and the time to recurrence of tumor, and (3) nine patients who developed DTH to the autologous melanoma cells in their original vaccine developed new metastases that failed to elicit DTH or elicited a much smaller response. In three cases, we were able to excise regressing tumors for histologic examination; such tumors were characterized by an intense infiltration of lymphocytes. This demonstration that an immune response to melanoma-associated antigens can be elicited in cancer-bearing patients provides some basis for optimism about the prospects for developing active immunotherapy that has practical therapeutic value.

Scientific discoveries that provide strong evidence of antitumor effects in preclinical models often encounter significant delays before being tested in patients with cancer. While some of these delays have a scientific basis, others do not. We need to do better. Innovative strategies need to move into early stage clinical trials as quickly as it is safe, and if successful, these therapies should efficiently obtain regulatory approval and widespread clinical application. In late 2009 and 2010 the Society for Immunotherapy of Cancer (SITC), convened an "Immunotherapy Summit" with representatives from immunotherapy organizations representing Europe, Japan, China and North America to discuss collaborations to improve development and delivery of cancer immunotherapy. One of the concepts raised by SITC and defined as critical by all parties was the need to identify hurdles that impede effective translation of cancer immunotherapy. With consensus on these hurdles, international working groups could be developed to make recommendations vetted by the participating organizations. These recommendations could then be considered by regulatory bodies, governmental and private funding agencies, pharmaceutical companies and academic institutions to facilitate changes necessary to accelerate clinical translation of novel immune-based cancer therapies. The critical hurdles identified by representatives of the collaborating organizations, now organized as the World Immunotherapy Council, are presented and discussed in this report. Some of the identified hurdles impede all investigators; others hinder investigators only in certain regions or institutions or are more relevant to specific types of immunotherapy or first-in-humans studies. Each of these hurdles can significantly delay clinical translation of promising advances in immunotherapy yet if overcome, have the potential to improve outcomes of patients with cancer.

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