Phase I trial to determine safety and immunogenicity of amplivant, a synthetic toll-like receptor 2 ligand, conjugated to two HPV16 E6 synthetic long peptides.

2614 Background: Therapeutic vaccines based on synthetic long peptides (SLPs) have a great potential for immunotherapy of cancer patients as these SLPs include both human leukocyte antigen (HLA) class I and II epitopes and no patient selection for HLA types is required. The antigen-induced immune response can be strengthened with immune stimulating additives. Amplivant (AV) is a synthetic Toll-like receptor 2 ligand which can be directly conjugated to tumor peptide antigens. In preclinical studies, AV-conjugation to antigens led to both enhanced antigen presentation by dendritic cells and T-cell priming and caused superior induction of effective anti-tumor responses. Moreover, AV-conjugated SLPs showed a 100 times higher immune response compared to unconjugated SLP. The current study is a first-in-human trial to investigate safety and immunogenicity of AV-conjugated human papillomavirus (HPV)16-SLPs. Methods: A dose escalation phase I trial was performed in 24 patients with HPV16 positive (pre-) malignant lesions. AV was conjugated to two SLPs derived from the most immunodominant regions of the HPV16 E6 oncoprotein. Four dose groups (1, 5, 20 or 50 μg of each peptide) in 6 patients each were studied. The vaccine was injected three times intradermally in DMSO / water with a three-week interval. Adverse events (AE) were collected according to CTCAE v4.0 up to 26 weeks. Peptide-specific T-cell immune responses were determined in blood samples taken before and after vaccination using complementary immunological assays (proliferation assay, IFNγ-ELISPOT and cytokine bead array). Results: Toxicity after three AV-conjugated HPV16-SLP vaccinations was limited to CTCAE grade 1 or 2, with predominantly inflammation at the vaccination site and sometimes flu-like symptoms, which generally resolved within one day. Dose increase resulted from no AE in the lowest dose group to mild/moderate AE in all vaccinated persons in the highest dose group. In the lowest dose group, minor vaccine-induced T-cell responses were observed in three of six vaccinated persons. In the highest dose group, all patients displayed a strong HPV16-specific T-cell response after vaccination. The induced T-cell response against HPV16 lasted until the end of the trial. Conclusions: This first-in-human study showed that AV conjugated to SLPs can safely be used as an intradermal therapeutic vaccine. AV-conjugated HPV16-SLP was able to induce robust HPV16-specific T-cell immunity in patients treated for HPV16 positive (pre-) malignancies without any other vaccine adjuvant or formulation. Increase in dose resulted in both a higher number of mild adverse events as well as stronger T-cell immunity. Clinical trial information: NCT02821494.

Association of T cell responses after vaccination with HPV16 long peptides for late stage cervical cancer with prolonged survival.

5525 Background: Therapeutic vaccination with HPV type 16 synthetic long peptides (HPV16-SLP) results in T cell–mediated regression of HPV16-induced premalignant lesions but fails to install effective immunity in patients with advanced HPV16-positive cervical cancer. We showed that HPV16-SLP vaccination in mice and in patients with advanced cervical cancer patients fosters robust HPV16-specific T cell responses, when combined with chemotherapy (Welters et al. Sci. Transl. Med., 2016). Methods: We have now completed a chemo-immunotherapy study in 70 patients with late stage HPV16+ cervical cancer (clinical trials.gov NCT02128126). Three HPV16-SLP vaccine doses were given 2 weeks after the second, third and fourth cycle of standard chemotherapy (carboplatin, AUC 6; paclitaxel 175 mg/ m2). Cohorts of 12 patients each were vaccinated with each of 4 dose levels (20, 40, 100 and 300 µg/ per peptide) of 13 overlapping HPV16 synthetic long peptides (HPV16-SLP) together covering the length of the 2 E6 and E7 proteins. Two additional cohorts of 6 patients each were vaccinated with the most promising doses of 40 and 100 µg/ peptide. Results: Robust vaccine-induced HPV16-specific T cell responses as assessed by interferon-γ Elispot were observed and were sustained until at least 30 days after the 6th cycle of chemotherapy. In addition the chemotherapy augmented recall responses to microbial antigens. Such robust T cell responses were not noted in previous trials when similar patients were vaccinated without timing of vaccination during chemotherapy. A marked and significant positive correlation was observed between the strength of the vaccine-induced immune response and overall survival. No such correlation was observed between the strength of the T cell response against common recall antigens and survival. In addition a remarkably high proportion of patients survived beyond 2 years after the start of therapy. Conclusions: The results suggest that survival duration is directly related to the strength of the vaccine-induced HPV16-specific T cell response and is not due to generally better immuno-competence. Clinical trial information: NCT 02128126.

Correlation between strength of T-cell response against HPV16 and survival after vaccination with HPV16 long peptides in combination with chemotherapy for late-stage cervical cancer.

140 Background: Therapeutic vaccination with HPV type 16 synthetic long peptides (HPV16-SLP) results in T cell–mediated regression of HPV16-induced premalignant lesions but fails to install effective immunity in patients with advanced HPV16-positive cervical cancer. We showed that HPV16-SLP vaccination in mice and in patients with advanced cervical cancer patients fosters robust HPV16-specific T cell responses, when combined with chemotherapy. In this study we noted that a single dose of vaccine 2 weeks into the 2nd cycle of chemotherapy was optimal, because at this time the immunosuppressive myeloid cells were down. Methods: We now completed a chemo-immunotherapy study in a larger number of patients with late stage HPV16+ cervical cancer. Three HPV16-SLP vaccine doses were given 2 weeks after the second, third, and fourth cycles of standard chemotherapy. Cohorts of 12 patients each were vaccinated with each of 4 dose levels (20, 40, 100, and 300 µg/ per peptide) of 13 overlapping HPV16 synthetic long peptides (HPV16-SLP) together covering the length of the 2 E6 and E7 proteins. Results: Robust vaccine-induced HPV16-specific T cell responses as assessed by interferon-g Elispot were observed and were sustained throughout the cycles of chemotherapy. These T cell responses were substantially increased in all patients who received HPV16-SLP . In addition, the chemotherapy augmented recall responses to microbial antigens. Such robust T cell responses were not noted in previous trials when similar patients were vaccinated without timing of vaccination during chemotherapy. A marked correlation was observed between the strength of the vaccine-induced immune response and longer-term clinical outcomes such as overall survival. No such correlation exists between the strength of the T cell response against common recall antigens and survival. In addition, a remarkably high proportion of patients survived beyond 20 months after the start of therapy. Conclusions: These results indicate that the survival advantage is specifically related to the strength of the vaccine-induced T cell response and is not due to generally better immuno-competence. Clinical trial information: NCT02128126.