1 2 5 4 VOLUME 18 | NUMBER 8 | AUGUST 2012 nAture medicine Therapeutic cancer vaccines hold the promise of combining meaningful efficacy (prolongation of survival) with very good safety and tolerability, as has been shown in several recent randomized trials 1-3 . However, development of cancer vaccines remains a major challenge, with little knowledge of (i) the optimal tumor antigens to target, (ii) suitable agents to counteract regulatory mechanisms opposing successful immunotherapy and (iii) surrogate and predictive biomarkers that can improve our understanding of these regulatory mechanisms and predict a patient's response to therapy. The first major issue addressed in this work is whether relevant HLArestricted peptides for immunotherapeutic intervention in patients with RCC can be identified and clinically validated. We defined the relevance of the antigens as their natural presence on the tumor in the majority of RCC samples, their immunogenicity (induction of T cell responses in clinical studies) and the association of the vaccine-induced T cell responses with clinical benefit. For the identification, selection and preclinical immunological validation of such antigens, we used the antigen discovery platform XPRESIDENT 4,5 to create a multipeptide vaccine designated IMA901 for immunotherapy of RCC. We tested IMA901 in HLA-A*02 + subjects with advanced RCC in two clinical trials, a phase 1 (n = 28) and a randomized phase 2 (n = 68) trial, both of which assessed the association of T cell responses to IMA901 with clinical benefit.

The use of rhGM-CSF allowed safe escalation of chemotherapy doses. Despite a 50% increase of the doxorubicin dose-intensity, the high-dose regimen failed to demonstrate any impact on survival in patients with ASTS. The low complete response rate, the high incidence of leiomyosarcomas, and liver metastases may in part explain these results. However, the lengthening of the PFS in the intensive arm, because of the quality of stable disease and inappropriate tumor evaluation policies that potentially lead to an underestimation of antitumor activity, does not definitively refute the use of a high-dose chemotherapy regimen in selected patients with ASTS.

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We conclude that after conventional-dose VIP chemotherapy, a shortened treatment course of IL-3 (5 days) sequentially followed by GM-CSF (10 days) combines the benefits of prolonged single GM-CSF treatment on WBC count recovery in all patients and an accelerated platelet recovery only in some intensively pretreated patients.