: Non-surgical treatments for cervical intraepithelial neoplasia 2/3 (CIN2/3) are needed as surgical treatments have been shown to double preterm delivery rate. The goal of this study was to demonstrate safety of a human papillomavirus (HPV) therapeutic vaccine called PepCan, which consists of four current good-manufacturing production-grade peptides covering the HPV type 16 E6 protein and skin test reagent as a novel adjuvant.: The study was a single-arm, single-institution, dose-escalation phase I clinical trial, and the patients (n = 24) were women with biopsy-proven CIN2/3. Four injections were administered intradermally every 3 weeks in limbs. Loop electrical excision procedure (LEEP) was performed 12 weeks after the last injection for treatment and histological analysis. Six subjects each were enrolled (50, 100, 250, and 500 μg per peptide). : The most common adverse events (AEs) were injection site reactions, and none of the patients experienced dose-limiting toxicities. The best histological response was seen at the 50 μg dose level with a regression rate of 83% (n = 6), and the overall rate was 52% (n = 23). Vaccine-induced immune responses to E6 were detected in 65% of recipients (significantly in 43%). Systemic T-helper type 1 (Th1) cells were significantly increased after four vaccinations ( = 0.02). : This study demonstrated that PepCan is safe. A significantly increased systemic level of Th1 cells suggests that which induces interleukin-12 (IL-12) , may have a Th1 promoting effect. A phase II clinical trial to assess the full effect of this vaccine is warranted.
In the dose-escalation phase of a Phase I clinical trial in which six subjects each were vaccinated with PepCan at the 50, 100, 250, and 500μg per peptide dose, the 50μg dose showed the best histological regression rate. Ten additional subjects were vaccinated at this dose in the final dose phase. As with the dose-escalation phase, no dose-limiting toxicities were observed. Overall, the histological regression rates were 50% at the 50μg dose (7 of 14) and 100μg dose (3 of 6), and 45% overall (14 of 31). Of subjects in whom HPV type 16 (HPV 16) was detected at entry, it became undetectable in 3 subjects after vaccination, and the viral loads significantly decreased in 9 subjects in whom HPV 16 infection was detected at entry and exit (p=0.008). Immune profiling revealed increased T-helper type 1 cells after vaccinations (p=0.02 and p=0.0004 after 2 and 4 vaccinations respectively). T-helper type 2 cells initially increased after 2 vaccinations (p=0.01), but decreased below the baseline level after 4 vaccinations although not significantly. Pre-vaccination regulatory T-cell levels were significantly lower in histological responders compared to non-responders (p=0.03). Feasibility of testing plasma for multiplex cytokine/chemokine analysis and of performing proteomic analysis of PBMCs was examined for potentially identifying biomarkers in the future. While these analyses are feasible to perform, attention needs to be given to how soon the blood samples would be processed after phlebotomy. As sufficient safety of PepCan has been demonstrated, enrollment for the Phase II clinical trial has been opened.
The association between the CD8+ T-cell responses to human papillomavirus type 16 (HPV-16) E6 protein and a favorable clinical trend has been demonstrated previously. The roles of human papillomavirus (HPV)-specific CD4+ T-cell responses and of regulatory T-cells (Tregs) were examined. Subjects with a recent history of abnormal Papanicolaou smear were eligible, and colposcopy guided biopsy was performed at enrollment. Interferon-γ enzyme-linked immunospot assay, and fluorescent activated cell sorter analysis to measure the frequencies of Tregs were performed. Subjects with histological diagnoses of cervical intraepithelial neoplasia 1, 2, or 3 were considered to have short-term persistence of cervical abnormality and were called “persistors” (n=51) while those of normal histology were designated to be “regressors” (n=33). A significantly higher percentage CD4+ T-cell response was detected in the regressors (15/33 or 45.5%) compared to the persistors (10/51 or 19.6%) (p=.015) for the E6 peptides but not for the E7 peptides. The CD4+ responses to certain E6 regions [E6(16–40), E6(91–115), E6(106–130), and E6(136–158)] were also significantly higher in the regressors. Although there was no difference in the frequencies of Tregs between the two groups, low frequencies of Tregs were significantly associated with positive CD4+ T-cell responses within certain E6 regions [E6(16–40), E6(31–55), E6(76–100), E6(91–115), and E6(106–130)]. The CD4+ and CD8+ T-cell responses to the HPV-16 E6 protein are associated with a favorable clinical trend. The HPV-16 E6 protein should be incorporated in the design of an HPV therapeutic vaccine.
The CD8 T-cell immune responses to the HPV-16 E6 antigens but not to E7 antigens are associated with a favorable clinical trend regardless of HPV types currently detected.
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