Unique potential of 4-1BB agonist antibody to promote durable regression of HPV ⁺ tumors when combined with an E6/E7 peptide vaccine

Abstract

Antibody modulation of T-cell coinhibitory (e.g., CTLA-4) or costimulatory (e.g., 4-1BB) receptors promotes clinical responses to a variety of cancers. Therapeutic cancer vaccination, in contrast, has produced limited clinical benefit and no curative therapies. The E6 and E7 oncoproteins of human papilloma virus (HPV) drive the majority of genital cancers, and many oropharyngeal tumors. We discovered 15-19 amino acid peptides from HPV-16 E6/E7 for which induction of T-cell immunity correlates with disease-free survival in patients treated for high-grade cervical neoplasia. We report here that intranasal vaccination with these peptides and the adjuvant alpha-galactosylceramide elicits systemic and mucosal T-cell responses leading to reduced HPV + TC-1 tumor growth and prolonged survival in mice. We hypothesized that the inability of these T cells to fully reject established tumors resulted from suppression in the tumor microenvironment which could be ameliorated through checkpoint modulation. Combining this E6/E7 peptide vaccine with checkpoint blockade produced only modest benefit; however, coadministration with a 4-1BB agonist antibody promoted durable regression of established genital TC-1 tumors. Relative to other therapies tested, this combination of vaccine and α4-1BB promoted the highest CD8 + versus regulatory FoxP3 + T-cell ratios, elicited 2-to 5-fold higher infiltration by E7-specific CTL, and evoked higher densities of highly cytotoxic TcEO (T cytotoxic Eomesodermin) CD8 (>70-fold) and ThEO (T helper Eomesodermin) CD4 (>17-fold) T cells. These findings have immediate clinical relevance both in terms of the direct clinical utility of the vaccine studied and in illustrating the potential of 4-1BB antibody to convert therapeutic E6/E7 vaccines already in clinical trials into curative therapies.C ervical cancer is the second most common malignancy in women worldwide and continues to cause significant morbidity and mortality in the developing world, where screening and prevention programs remain rudimentary (1). The E6 and E7 oncoproteins of human papilloma virus (HPV) drive cervical cancer formation and are critical for maintenance of the transformed state (2). Beyond cervical cancer, HPV infection underlies 40% or greater of cases of oropharyngeal, anal, penile, vaginal, and vulvar cancers (3).The immunologically foreign nature of the HPV E6 and E7 proteins, coupled with their critical role in maintaining the oncogenic state, makes them ideal target antigens for therapeutic cancer vaccination. Whereas peptide-, protein-, viral-and DNAbased vaccines targeting E6 and E7 have been studied both preclinically and in clinical trials, most fail to induce regression of established HPV + tumors (4). To some degree, all of these vaccines succeed in eliciting peripheral E6/E7-specific T-cell responses; however, not all are proven to generate T cells capable of trafficking to the genital mucosa where cervical cancer develops. Whereas a number of these vaccines extend survival, few can induce regression of establishe...

Nanoparticle Conjugation of Human Papillomavirus 16 E7-long Peptides Enhances Therapeutic Vaccine Efficacy against Solid Tumors in Mice

“…We have in addition confirmed the results of a previous study describing the potential of combining therapeutic vaccination with anti-41BB (40), strengthening the proof of concept by demonstrating herein that this agonistic antibody can be beneficially combined with a lymph-node targeting solid-phase antigen delivery system. Collectively, the data establish that anti-41BB treatment promotes the generation of terminal effector CD8 + T cells that infiltrate the tumors in higher numbers, are more activated, and produce higher amounts of cytokines.…”

“…Next we vaccinated TC-1 tumor-bearing mice at an earlier timepoint, incipient neoplasia, similarly to what has been reported in a previous study (40). We vaccinated at day 7 after implantation, when the mean tumor volume was ~22 mm 3, and 32% of the mice lacked a palpable mass.…”

“…Another recognized limitation of therapeutic vaccines based on SLPs is the concomitant generation of Tregs in response to the immunization (16,40), an undesirable response that has also been observed in HPV + cancer patients, particularly those with larger/advanced lesions (7). Consistent with this result, we observed that immunization of tumor-bearing mice with free E7LP was associated with an increase in tumor-infiltrating Tregs that resulted in a low CD8 + T cell/Treg ratio.…”

“…Early immunization with a traditional free SLP vaccine of TC-1 tumor-bearing mice led to discernibly enhanced immune responses and survival when given in combination with an agonistic anti-41BB antibody (40). In light of the evident loss of CD8 + T-cell activity in the stable disease and relapse phases (Fig.…”

Hope in the Long Road Toward the Development of a Therapeutic Human Papillomavirus Vaccine

“…HPV-positive tumors often present upregulated levels of PD-1 ligand on their surface and decreased levels of costimulatory molecules such as OX40 and 4-1BB on T cells. In preclinical models, blockade of these cells or molecules synergized with HPV vaccine, but it was not always the same antagonist or agonist of costimulatory molecules that optimally synergized with selected HPV vaccines (12)(13)(14). Several clinical trials are currently examining the effects of checkpoint inhibitors such as anti-CTLA-4 and/or anti-PD-1/PD-L1 in advanced stage HPV-associated disease (NCT01711515, NCT01693783, NCT01975831).…”