Safety and Efficacy of Repeat Administration of Ad/PNP and Fludarabine Phosphate in Patients With Local Head/Neck Cancer

• Mechanism of action. The study drug, Ad/PNP-F-araAMP (Fludarabine phosphate) consists of a nonreplicating adenoviral vector expressing the E. coli purine nucleoside phosphorylase (PNP) injected intratumorally followed by intravenous administration of F-araAMP. This combination generates 2-fluoroadenine (F-Ade) within the tumor resulting in focal chemotherapeutic activity.

F-araAMP is an agent that is rapidly cleaved by plasma phosphatases to fludarabine, which is the primary circulating form of the drug and has activity against certain hematological malignancies, but not against solid tumors such as head and neck squamous cell carcinoma (HNSCC). Fludarabine (F-araA) is an adenosine analog and substrate for E. coli PNP, which cleaves the glycosidic bond of F-araA to generate F-Ade. The F-Ade metabolite has shown pronounced activity against human tumor xenografts in mice.

Many refractory tumors are refractory precisely because they have a very low growth fraction, i.e., a relatively small percentage of tumor cells dividing at any particular point in time. In nonclinical studies, significant in vivo antitumor activity has been demonstrated by F-Ade generation from F-araAMP in tumors in which 2.5 to 10% of cells express the E. coli PNP gene. In addition, anti-tumor effect was seen in patients with advanced solid tumors (melanoma and head and neck cancer) in the higher dose cohorts during a Phase 1 study (see next section).

• Tumor response with Ad/PNP-F-araAMP in Phase 1 Study. The safety and efficacy of Ad/PNP-F-araAMP has been evaluated in a Phase 1 study, PNP-001 (NCT01310179). Four escalating dose levels were evaluated in 10 subjects with head and neck cancer and 2 subjects with melanoma; clinical activity was observed at the highest dose levels following 3 intratumoral injections of Ad/PNP over 2 days and IV F-araAMP phosphate over 3 days. The overall response rate (CR+PR) was approximately 67% in the 2 highest dose cohorts, Cohorts 3 and 4. Results suggest a dose response effect. The duration of response in the injected tumor was limited, with 4 of 5 responding tumors having disease progression of the injected lesion prior to last follow-up on Day 56, suggesting that repeat administration should be evaluated. Ad/PNP + F-araAMP was well tolerated. No subject experienced a dose-limiting toxicity and none of the subjects discontinued study treatment. Overall, the activity and safety profile of Ad/PNP seen in the Phase 1 study supports further clinical evaluation of repeat administration of Ad/PNP (IT) and F-araAMP phosphate infusion for patients with HNSCC.
• Purpose of the Study. Based upon the tumor response seen with a single administration of the two highest dose levels of Ad/PNP-F-araAMP in the Phase 1 study (NCT01310179), PNP plans to investigate the safety and assess anti-tumor activity of repeat cycles of injection of Ad/PNP + F-araAMP in patients with advanced head and neck cancer. Subjects in the study will have RECIST 1.1 measurable HNSCC which is amenable to local injection for which there is no effective curative or palliative treatment option. This study population was selected since results from this Phase 1/2 trial are intended to support the safety of repeat dosing in further clinical investigation.
• Study Design. The trial is designed as a single-arm study to evaluate the safety of repeat cycles of Ad/PNP and F-araAMP in patients with recurrent HNSCC with tumor(s) accessible for injection. Ad/PNP will be injected intratumorally twice on Day 1 and once on Day 2 followed by infusion of F-araAMP daily on Days 3, 4, and 5. Subjects will receive repeat administration of Ad/PNP-F-araAMP every 4 weeks (i.e., each cycle) for 5 cycles or until injected tumor progresses, unacceptable toxicity occurs, no tumor is present for injection, or patient death. Tumor response in the injected tumor(s) will be assessed by physical examination as well as by radiographic imaging. All subjects will be monitored for adverse events during study participation.

Inclusion criteria

• Provided Informed Consent
• Age ≥ 18 years
• Patients with histologically or cytologically confirmed diagnosis of recurrent cancer of the head and neck region for whom there is no curative treatment option. For the purposes of trial eligibility, cancers of the head and neck shall include, in addition to head and neck squamous cell carcinoma (HNSCC), cutaneous squamous cell primary sites and squamous cell carcinoma of unknown primary presenting with neck lymph nodal disease, as well as nasopharyngeal carcinoma, and salivary gland tumors.
• All standard or approved treatment options that would provide substantive palliation must have failed, been exhausted, or patient not eligible or willing to use them (for example neuropathy, nephropathy , or hearing loss precluding the use of cisplatin)
• Tumor mass (primary tumor and/or lymphadenopathy) measurable by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 and technically suitable for intratumoral injections (otolaryngologist will determine feasibility). Patients with nodal disease (or metastatic disease) that is needle accessible are eligible. Patients with additional tumors (including distant metastatic disease) beyond the intratumoral injection accessible tumor(s) that are not accessible for intratumoral injection are eligible ONLY if the patient has no other treatment option for the metastatic disease and treatment of local disease may provide the patient some benefit or palliation.
• Eastern Cooperative Oncology Group performance status of ≤ 2
• In the judgment of the Investigator, the patient has recovered sufficiently from any previous significant therapy side effects or toxicities prior to Ad/PNP administration.
• Absolute neutrophil count ≥ 1,500 cells/ul; hemoglobin ≥ 9 g/dl, platelets ≥ 100,000/ul
• Serum creatinine ≤ 1.5 mg/dl, or calculated creatinine clearance ≥ 60 ml/min
• Bilirubin ≤ upper limit of normal, alanine aminotransferase ≤ 1.5 x upper limit of normal and/or aspartate aminotransferase ≤ 1.5 x upper limit of normal, alkaline phosphatase ≤ 2.5 x upper limit of normal
• Prothrombin time (PT)/international normalized ratio (INR) ≤ 1.5 x upper limit of normal
• Activated partial thromboplastin (aPTT) time ≤ 1.5 x upper limit of normal
• Female patients must have a negative urine or serum pregnancy at screening (pregnancy test is not required for patients with bilateral oophorectomy and/or hysterectomy or for those patients who are > 1 year postmenopausal)
• All patients of reproductive potential must agree to use a medically acceptable form of contraception (eg, hormonal birth control, double-barrier method) or abstinence.

Exclusion criteria

• Prior history or current diagnosis of leukemia
• Have received any gene therapy products or oncolytic viral therapy
• Receiving allopurinol
• Received an investigational drug within 30 days prior to first injection of Ad/PNP
• Received radiation treatment < 4 weeks prior to first injection of Ad/PNP, and does not have any RECIST 1.1 evaluable lesions that are outside the radiation field. (If the patient has RECIST 1.1 evaluable lesions outside the radiation field then they can be included.)
• Received chemotherapy (systemic anticancer treatment) < 4 weeks prior to first injection of Ad/PNP and has not recovered from all the related side effects. (If the patient has recovered from all related side effects or has reached a new baseline, then they may begin receiving treatment at sooner than 4 weeks)
• Have significant baseline neuropathy (> Grade 2 based on Common Terminology Criteria for Adverse events [CTCAE] v5.0)
• Uncontrolled intercurrent disease (e.g., diabetes, hypertension, thyroid disease, active infection)
• Had within 6 months prior to enrollment: Myocardial infarction, cerebral vascular accident, uncontrolled congestive heart failure, significant liver disease, unstable angina
• Fever (temperature > 38.1 degrees C orally)
• Receiving chronic systemic corticosteroids (> 3 weeks) or any chronic immunosuppressive medications within 14 days prior to first injection of Ad/PNP. Subjects receiving short courses of corticosteroids are considered eligible for the study.
• Receiving anticoagulants other than those to maintain patency of venous lines
• Women who are pregnant or breast feeding
• History of HIV infection. No requirement for testing.