Phase I study: to determine the biological activity of two HPV16 E6 specific peptides coupled to Amplivant®, a Toll-like receptor ligand in nonmetastatic patients treated for HPV16-positive head and neck cancer

Human papillomavirus (HPV) has been found to be associated with several types
of cancer, amongst others oropharyngeal squamous cell cancers (OSCC). The
number of HPV attributable OSCC is strongly increasing, and comprises a large
proportion of this disease in young adults and women. HPV16 is the far most
common HPV type detected. HPV16 encodes the two tumor-specific oncoproteins E6
and E7. In most humans the virus is cleared. However, in some individuals,
infection results in an uncontrolled persistent HPV16 infection that due to
expression of the viral oncoproteins E6 and E7 may lead to the formation of
malignancies. Moreover, these oncoproteins maintain the malignant state of the
transformed cells. The virus-specific interferon-γ (IFNγ)-producing CD4+ helper
T cells (Th1 cells) and CD8+ cytotoxic T-lymphocytes (CTL) are able to
recognize peptides processed from the highly immunogenic E6 and play a critical
role in the elimination and/or control of the virus. Studies in patients with
HPV associated tumors (such as OSCC) showed that the spontaneous HPV-specific
T-cell responses, are weak and fail to sufficiently control tumor outgrowth.
Preexisting T-cell responses specific against E6 and E7 in patients with HPV
related tumors such as OSCC are associated with better outcome after treatment.
Since the HPV16-transformed tumor cells constitutively express the two HPV16
encoded E6 and E7 oncoproteins, these viral antigens are considered to be
excellent targets for immunotherapeutic vaccine strategies aiming at
reinforcing the tumor-specific T-cell response. Previous vaccination studies
showed that the use of our first generation HPV16 synthetic long peptides
vaccine (HPV16-SLP) was safe and highly immunogenic in patients with
HPV-induced anogenital lesions. Vaccination of patients with cervical cancer
(CxCa) also resulted in the induction of HPV16-specific T-cell responses but
the nature and strength of the induced T-cell responses was not sufficient for
the regression of these tumors. Specifically, it was concluded that the
polarization of the T-cell response to Th1 (IFN*-response) was not optimal and
a much stronger CD8+ T-cell response was required for clinical efficacy. These
results initiated the development of new HPV16 vaccination strategies that are
able to polarize the induced Th1 response and obtain strong CD8+ T-cell
cytotoxicity. One of these developments consists of conjugating two of the
HPV16 E6 SLP to Amplivant®, a synthetic Toll-like receptor (TLR) 2 ligand.
These two peptides cover the most immunodominant regions of the overlapping
HPV16-SLP set and contain both Th and CTL epitopes. Peptide conjugated
Amplivant® has been selected because it is acknowledged for its capacity to
strongly enhance antigen presentation by dendritic cells (DCs), enhance T-cell
priming and cause superior induction of effective anti-tumor CTL responses in
mouse tumor models, compared to a mixture of free TLR ligand and peptide. In
preclinical murine studies, Amplivant®-conjugated SLP showed 10 to 100 times
higher bioactivity compared to unconjugated SLP, in terms of induced immune
responses. In addition, the quantity and quality of human T-cell responses, and
especially the HPV16-specific CD8+ T-cell response, in cancer patients could be
markedly enhanced by ex vivo stimulation with Amplivant®-conjugated SLPs. Here
we propose a phase I study to establish the biological activity using this
highly promising novel therapeutic vaccine concept named: Hespecta (HPV E Six
Peptide Conjugated To Amplivant®), to induce HPV16 E6-specific T-cell
responses.

Primary objective: to determine the biological activityof Hespecta that is able
to induce HPV16 E6-specific T-cell immunity within a proposed dose escalation
of 1, 5, 20 or 50 µg/peptide - conjugate in patients treated for HPV16+ OSCC.
Secondary objectives: to study safety of Hespecta by collecting all adverse
events according to Common Terminology Criteria for Adverse Events v4.0
(CTCAE).

This is a single center, translational dose escalation phase I trial.

Patients first treated with curative intent for advanced HPV16+ OSCC will be
vaccinated intradermally (i.d.) in four dose escalation groups (1, 5, 20 or 50
µg/peptide). Each dose group exists of 6 patients. The dose range is based on a
10-100 fold higher bioactivity of Amplivant® conjugated peptides in preclinical
studies. The starting dose of this dose escalation trial is based on
preclinical murine experiments showing that a dose of 1 µg per Amplivant®
conjugated peptide resulted in no severe toxicity and a suboptimal immune
response in that the magnitude of the immune response increased when mice were
given a higher dose of vaccine. We reason that this provides the best
scientific basis for the first dose to start with. As Amplivant® conjugated
peptides are expected to induce T-cell responses more effectively compared to
unconjugated peptides, the lowest dose known (50 µg per peptide) of
unconjugated peptides able to induce T-cell responses is used as highest dose
in this trial. From this starting dose an ascending dose range is proposed,
evaluating four doses (1, 5, 20, 50 micrograms per peptide). Notably, the
higher the dose the smaller the dose-fold increase between the doses (5, 4, 2.5
times), this should allow for maximal safety. Patients will be vaccinated three
times with an interval of three weeks with a fixed dose of Hespecta (i.e. no
escalating dose within the patient). Vaccination will start with the i.d.
injection of the lowest dose. The decision to start enrollment at the next dose
level will be made by the Independent Data Monitoring Committee (IDMC), and
will be based only on the assessment of safety data when 4 out of 6 patients
have completed the first follow up visit after the third vaccination. If in two
or more patients, grade 3 or 4 vaccine related toxicity occurs the dose
escalation phase will be discontinued. If in the lowest dose group two patients
experience grade 3 or 4 vaccine related toxicity, there is no safe dose and the
study will be discontinued.

Patients will visit the clinic during the trial seven additional times
(screening visit, three vaccination visits, and three follow up visits).These
follow up visits are combined with regular treatment follow up visits.
Potential risks with the current trial are mainly linked to the toxicity
related to the treatment compounds utilized in Hespecta. Although the rabbit
toxicity testing of Hespecta (see IMPD brochure) did not show any severe side
effects, it is expected from previous results with HPV16-SLP, that the most
important AEs of Hespecta may consist of fever, chills, nausea, malaise,
fatigue and local reactions at the vaccination site including pain, redness,
swelling and itching. Generally the AEs after vaccination with HPV16-SLP did
not exceed grade 2 according to the CTCAE criteria. Almost all patients,
vaccinated with HPV16-SLP formulated in Montanide ISA51 experienced local
injection site reactions (grade 2). After vaccination, ulceration/abscess
formation occasionally occurred, estimated to be in between 1 and 5% of
vaccinations, due to the use of this Montanide as adjuvant. The current vaccine
is administered without Montanide, and therefore, it is expected that these
local reaction will be less severe. Allergic reactions have occurred in a few
patients after HPV16-SLP vaccinations, controlled with antihistamines.
Vaccinations should therefore only be administered in a clinic where immediate
treatment of severe allergic reactions is possible. Thus, after vaccinations,
patients will be closely monitored during one hour after injection to provide
means for immediate treatment of allergic reactions. In addition to the
standard of care, the patients participating in the trial will receive three
vaccinations with Hespecta for the induction of a strong and broad CTL response
against HPV16 E6. Study patients will not be paid for their participation
however any study-related travel expenses will be reimbursed.