e15125 Background: In solid tumors such as prostate cancer, novel biomarkers are needed for assessing immunological responses and clinical efficacy. By using dextramers specific for PSA we have retrospectively analyzed CD8+ T cell frequencies in patients with HER-2/neu+ prostate cancer who had received the AE37 vaccine in a phase I study (Perez SA et al Clin. Cancer Res. 2010, 16:3495). AE37 binds to numerous MHC alleles (Perez SA et al Clin. Cancer Res. 2010, 16:3495) (Salazar LG, Clin Cancer Res. 2003, 9:5559) encouraging its use as a therapeutic vaccine for general HER-2/neu+ cancer patients. Methods: CD8+ Dextramer+ T cells were measured, retrospectively, in the blood (which was stored in N2 liquid) of HLA-A24+ (n= 12) and HLA-A2+ (n=12) patients. Blood lymphocytes collected before, during and 6-months post vaccination were all analyzed with the same method involving direct labeling with HLA A24/PSA(153-161)-FITC and PerCP-conjugated anti-CD8 monoclonal antibody. Results: 8 of 12 HLA-A24+ patients had preexistent immunity to PSA as evidenced by the increased percentages of CD8+ HLA-A24/PSA(153-161)+ T cells in pre-vaccination samples. All of these patients had shown increased in vitro (IFNγ-based ELISPOT assay) and in vivo (DTH) immunological responses to the AE37 vaccine in the phase I study (Perez SA et al Clin. Cancer Res. 2010, 16:3495). Importantly, this preexistent immunity was significantly boosted in 5 patients during vaccinations with AE37, was slightly increased in 2 others, whereas in one patient no changes were observed during vaccinations. Conclusions: These results suggest that HLA-A24 expression along with preexistent immunity to PSA(153-164) may represent biomarkers based on which HER-2/neu+ patients can be selected most likely to benefit from vaccination with AE37. A phase II trial is warranted for validating these results. Given the promiscuity of AE37, it would be intriguing to examine if preexistent immunity to other prostate antigens restricted by various MHC alleles exist and to demonstrate an increase in preexistent immunity in association with a positive immunologic response to vaccination with AE37.
Phase I study of BIBF 1120 with docetaxel and prednisone in metastatic chemo-naive hormone-refractory prostate cancer patients