The investigators hypothesize that Tadalafil treatment, by lowering Myeloid Derived Suppressor Cells (MDSCs) and regulatory T cells (Tregs), can prime an antitumor immune response and promote a permissive environment that should increase the efficacy of anti-tumor vaccine in a setting of minimal residual disease.

This study is halting accrual at the end of the phase 1 portion of the study as data from the phase I study suggest that an alternative approach for the phase 2 portion of the study be undertaken. A newly designed Phase II trial is being developed and will be submitted as a new study protocol.

Inclusion Criteria:

1. Biopsy-proven recurrent or second primary HNSCC of the oral cavity, oropharynx, hypopharynx or larynx (second primary includes unknown primary)

2. Stage III or IV (AJCC, 7th ed., 2010) recurrent or second primary HNSCC (For recurrent tumors, staging is determined by the recurrent stage, not by the original pretreatment stage.)

3. Surgically resectable, recurrent or second primary HNSCC

4. Prior radiation, with or without prior surgery and/or chemotherapy, to the head and neck for definitive treatment of HNSCC of the oral cavity, oropharynx, hypopharynx or larynx with previously documented complete clinical or radiographic response to initial treatment

   • a. Prior radiation and any chemotherapy, must have been completed >4 months prior to biopsy-proven recurrence or second primary site disease
   • b. Recurrent or second primary HNSCC arises within the previously irradiated field

5. Age ≥ 18 years

6. Eastern Cooperative Oncology Group (ECOG) Performance Status of 0, 1 or 2 or equivalent scale score. See Appendix D for equivalent scale criteria.

7. Acceptable organ function as defined by all of the following:

   • Alkaline phosphatase < 4.0 x upper limit of normal (ULN)

   • Aspartate transaminase (AST) ≤ 2.5 x ULN

   • Alanine transaminase (ALT) ≤ 2.5 x ULN

   • calculated Creatinine Clearance ≥ 51ml/min as determined by the Cockcroft-Gault Equation:

     • [(140-age) * (Weight in kg) * (0.85, if female)] / (72 * Cr)

8. Suitable venous access to allow for all study related blood sampling (safety and research)

9. Ability to understand and willingness to sign the written informed consent and Health Insurance Portability and Accountability Act (HIPAA) document/s.

Inclusion Criteria (non-randomized control)

1. Biopsy-proven recurrent or second primary HNSCC of the oral cavity, oropharynx, hypopharynx or larynx (second primary includes unknown primary)

2. Stage III or IV (AJCC, 7th ed., 2010) recurrent or second primary HNSCC (For recurrent tumors, staging is determined by the recurrent stage, not by the original pretreatment stage.)

3. Surgically resectable, recurrent or second primary HNSCC

4. Prior radiation with or without prior surgery and/or chemotherapy, to the head and neck for definitive treatment of HNSCC of the oral cavity, oropharynx, hypopharynx or larynx with previously documented complete clinical or radiographic response to initial treatment

   • a. Prior radiation and any chemotherapy, must have been completed >4 months prior to biopsy-proven recurrence or second primary site disease
   • b. Recurrent or second primary HNSCC arises within the previously irradiated field

5. Age ≥18 years

6. Eastern Cooperative Oncology Group (ECOG) Performance Status of 0, 1 or 2 or equivalent scale score.

7. Suitable venous access to allow for all study related blood sampling (safety and research)

8. Ability to understand and willingness to sign the written informed consent and HIPAA document/s.

Exclusion Criteria:

1. Salvage surgery is not recommended as per National Comprehensive Cancer Network (NCCN) guidelines, or after multidisciplinary treatment evaluation, including those with surgically unresectable disease at primary site or regional lymph nodes

2. Recurrent or second primary AJCC Stage I or II HNSCC (for recurrent tumors, staging is determined by the recurrent stage, not by the original pretreatment stage).

3. Distant metastatic disease

4. Recurrent or second primary HNSCC of the nasopharynx, paranasal sinuses, or cervical esophagus

5. Use of Phosphodiesterase Type 5 (PDE5) inhibitors such as vardenafil (Levitra®), Tadalafil (Cialis®), and sildenafil citrate (Viagra®) ≤15-days prior to (intended) enrollment

6. Patients who have the intention to receive non-study PDE5 inhibitors and flu vaccination(s) anytime during the study will be excluded.

7. Prior or known adverse reactions to PDE5 inhibitors, poly-ICLC (Hiltonol®), and prior dose(s) of Influenza vaccine including but not limited to their components

8. History of severe or unstable cardiac or cerebrovascular disease:

   • a. Myocardial infarction within the last 90 days
   • b. Unstable angina or angina occurring during sexual intercourse
   • c. New York Heart Association (NYHA) Class 2 or greater heart failure in the last 3 months.
   • d. Uncontrolled arrhythmias
   • e. Sustained hypotension (<90/50 mmHg) or uncontrolled Hypertension (>170/100 mmHg)
   • f. Stroke within the last 6 months

9. Therapy with nitrates, alpha-blockers, or cytochrome P450 (CYP3A4) inhibitors within 7-days prior to study treatment initiation and for whom stopping is unsafe and/or a safe substitute is not medically recommended. Some examples are provided in Appendix A.

10. Positive Antinuclear Antibody Test (ANA)

11. Immunosuppression or immunocompromised for reasons not directly related to patient's malignancy (e.g. HIV or kidney transplant)

12. History of severe or life threatening autoimmune diseases [Exceptions: Mild autoimmune diseases determined at the discretion of the Investigator(s), e.g. psoriasis.]

13. Unilateral blindness, hereditary retinal disorders, or at an increased risk of blindness

14. Unilateral deafness, or severe hearing loss dependent upon hearing aid(s) for serviceable communication

15. Female patients who are pregnant or breastfeeding. (Females of childbearing potential are required to have a negative urine β-human chorionic gonadotropin (β-hCG) pregnancy test result obtained during screening; pregnancy testing is not required for post-menopausal or surgically sterilized women.)

16. Females of childbearing potential who refuse to practice effective methods of contraception or abstain from heterosexual intercourse from the time of signing the informed consent through 30-days after the last vaccination.

17. Serious medical or psychiatric illness/condition, including alcohol or drug abuse likely in the judgment of the Investigator(s) to interfere with compliance to protocol treatment/research.

18. Patients of vulnerable populations such as children less than 18 years of age, prisoners, institutionalized individuals or others likely to be vulnerable are not eligible for participation in this study.

Exclusion Criteria (non-randomized control)

1. Salvage surgery is not recommended as per NCCN guidelines, or after multidisciplinary treatment evaluation, including those with surgically unresectable disease at primary site or regional lymph nodes
2. Recurrent or second primary AJCC Stage I or II HNSCC (for recurrent tumors, staging is determined by the recurrent stage, not by the original pretreatment stage).
3. Distant metastatic disease
4. Recurrent or second primary HNSCC of the nasopharynx, paranasal sinuses, or cervical esophagus
5. Use of PDE5 inhibitors such as vardenafil (Levitra®), Tadalafil (Cialis®), and sildenafil citrate (Viagra®) ≤15-days prior to (intended) enrollment
6. Patients who have the intention to receive non-study PDE5 inhibitors and flu vaccination(s) anytime during the study will be excluded.
7. Positive Antinuclear Antibody Test (ANA)
8. Immunosuppression or immunocompromised for reasons not directly related to patient's malignancy (e.g. HIV or kidney transplant)
9. History of severe or life threatening autoimmune diseases [Exceptions: Mild autoimmune diseases determined at the discretion of the Investigator(s), e.g. psoriasis.]