Feasibility and Tolerability of IMLYGIC for the Treatment of Cutaneous Neurofibromas in Adults With NF1

This is a single institutional feasibility and tolerability study of IMLYGIC monotherapy in adults with NF1 and cNFs in need of treatment. Each 28-day treatment cycle will be defined as intralesional administration of IMLYGIC administered on day 1 and 21 of Cycle 1 and days 7 and 21 for Cycles 2-4 for up to 4 cycles. (8 treatments). All patients must be at least 18 years of age or older with at least 8 cNFs measuring 5 mm at minimum in longest diameter, Karnofsky performance status of 80% or higher, and have adequate hematologic, renal and hepatic function. After providing written informed consent to participate in the study, patients will be evaluated for study eligibility during the screening visits. During screening, a complete medical history will be documented, and a complete physical examination will be conducted. Measurement of vital signs and Karnofsky performance status will be obtained. Laboratory samples will be collected to assess hematologic, renal, and hepatic function. The investigators will also collect a sample to evaluate Herpes Simplex-1 (HSV1) DNA Polymerase Chain Reaction (PCR), HSV1 Immunoglobin G (IgG) and Immunoglobin M (IgM) antibodies, these will be Clinical Laboratory Improvement Amendments (CLIA) certified laboratory tests at baseline and at the end of the study. Patients should be treated until week 16 (4 months). After 16 weeks, patients will remain on study for 30-days to allow post-treatment assessment. If a participant achieves a complete response (cutaneous neurofibromas resolve and are no longer visible) for all of the target tumors before the end of the planned treatment, then the study drug will be stopped at that point, but the patient will be seen at the 30 day mark post last treatment in all cases. Efficacy assessment will be based on tumor measurement by physical measurement, photographs of superficial lesions, and representative biopsy of residual masses suspected. After cycles 2, 4 and at End of Treatment (EOT), a thorough assessment of the clinical response status will be made, particularly to determine if any evidence of biological activity of treatment can be observed.