Immune Gene Therapy for Patients with CLL Using Repeat Dose Intranodal Injection of Ad-ISF35, a Replication Incompetent Vector Expressing a Membrane-Stable CD40 Binding Protein.

Abstract 1476 Ad-ISF35 is a replication-defective adenovirus (Ad) vector that encodes ISF35, which is a potent immuno-stimulatory CD40 binding protein designed to maximize stable, high-level cell-surface expression of this molecule. ISF35 can induce expression of costimulatory and death receptor molecules on chronic lymphocytic leukemia (CLL) cells in vitro and in vivo . Ad-ISF35 has shown to be safe and to have potential activity in two clinical studies in CLL patients, one using infusions of autologous CLL cells trasduced ex-vivo with Ad-ISF35 and the second one using a single intranodal injection of Ad-ISF35. From this second study we have observed that the maximum tolerated intranodal dose (MTD) was 3.3 × 10 10 viral particles (vp) due to development of asymptomatic and transient hypophosphatemia, SGOT/AST elevation and neutropenia in some patients treated with higher doses. Using this MTD dose (3.3 × 10 10 vp), we designed a clinical study to evaluate the toxicity and efficacy of repeat doses of intranodal Ad-ISF35 administration in CLL patients. Ten patients with median age of 66 years (range 56–74, 80% male and 20% female), with progressive CLL (Rai stage III and IV) and median leukemia-cell doubling times of 6 months participated in this repeat dose intranodal administration study involving up to six biweekly injections with a fixed dose of 3.3 ×10 10 vp. Intranodal Ad-ISF35 injections were done into pathologically enlarged lymph nodes accessible by palpation using ultrasound guidance. Repeat dose intranodal administration of Ad-ISF35 was well tolerated by the majority of patients. The median number of injections was 5. One patient developed transient and asymptomatic Grade III hyponatremia after injection #4 considered to be a dose-limiting toxicity (DLT). No dose adjustments were required in any of the patients and we have not observed cumulative dose effect or long-term toxicities after a median follow up of 14 months. Other adverse events included erythema, swelling and/or pain at the site of injection and “flu-like symptoms”, which occurred primarily during the first 24 hours after each injection and were self-limited. The majority of patients experienced >50% reduction in leukemia cell counts (70% of patients), lymphadenopathy (80% of patients) and/or splenomegaly (70% of patients) during the course of treatment. Response assessment based on IW-CLL-08 criteria showed and overall response rate of 30% with 3 patients achieving a partial response, 4 patients with stable disease and 3 patients with disease progression. Although we have no evidence of Ad-ISF35 vector expression beyond the injected lymph node, we observed upregulation of death receptors, immune costimulatory molecules, and pro-apoptotic proteins in the circulating, non-transduced CLL cells of the treated patients suggesting a bystander effect. Cytokine expression analysis in the sera of treated patients showed increased levels of interferon-gamma and interleukin-6 beginning 8 hours after injection. In addition, we observed evidence of antibody production against Ad-ISF35 with the ability in some cases to neutralize vector transduction in vitro . However, we did not see antibody formation against human CD154. In summary, we found that repeat dose Ad-ISF35 intranodal administration via direct injection in patients with CLL was well tolerated and had systemic biologic and clinical activity that appears to be mediated by the effect of non-transduced bystander cells. These data suggest that intranodal administration of Ad-ISF35 may be safe and potentially effective in the treatment of patients with CLL or other B-cell lymphomas. Disclosures: Kipps: Memgen, LLC: Membership on an entity9s Board of Directors or advisory committees.