Abstract CN01-03: Immunotherapy of established lesions caused by high-risk HPV

Therapeutic vaccination with a synthetic long peptide (SLP@) vaccine mediated the eradication of established human papillomavirus type 16 (HPV16)-positive tumors in mice and controlled wart growth and latent virus infection in rabbits persistently infected with cottontail rabbit papillomavirus. Subsequent phase I/II studies with an HPV16 SLP@ vaccine, consisting of 13 long peptides covering the HPV16 E6 and E7 antigens, in patients with advanced HPV16-positive cervical cancer, revealed that this vaccine was safe and highly immunogenic. The purpose of the current study was to test the clinical efficacy of this HPV16 SLP@ vaccine in HPV16-induced high-grade vulvar intraepithelial neoplasia (VIN3), a premalignant epithelial disorder, spontaneous regression of which occurs in less than 2% of patients and in which recurrence after standard treatment is high. In a phase 2 trial, 20 women with VIN3 were vaccinated three times sc in the limbs with a mix of the HPV16 E6 and E7 synthetic long peptides formulated in Montanide ISA-51. The endpoints were objective clinical responses, defined as reduction of at least 50% in lesion size (partial response) or complete regressions, and HPV16-specific T-cell responses, determined before and after vaccination. The vaccine was safe, as no side effects exceeding CTC grade 2 were observed. At 3 and 12 months after the last vaccination an objective response was observed in 12/20 (60%) and 15/19 (79%) patients respectively. Nine of them showed a complete and durable regression of the lesions at 12 months and at 24 months. The strength of the vaccine-induced HPV16-specific T-cell response was significantly higher in the group of patients with a complete regression of their lesions as compared to nonresponders. This study shows that in women with VIN3 objective clinical responses can be achieved by therapeutic vaccination with synthetic long peptides that is able to induce effective HVP16-specific T-cell responses. Literature: 1. Kenter GG, Welters MJ, Valentijn AR, Lowik MJ, Berends-van der Meer DM, Vloon AP, Essahsah F, Fathers LM, Drijfhout JW, Offringa R,Wafelman AR, Oostendorp J, Fleuren GJ, Burg van der SH, Melief CJ. Vaccination against Human Papillomavirus 16 oncoproteins for vulvar intraepithelial neoplasia. N Engl J Med. 2009 Nov 5;361(19):1838-47. 2. Melief CJ, van der Burg SH. Immunotherapy of established (pre)malignant disease by synthetic long peptide vaccines. Nat Rev Cancer. 2008 May;8(5):351-60. Citation Information: Cancer Prev Res 2010;3(12 Suppl):CN01-03.