Gene Immunotherapy of Chronic Lymphocytic Leukemia: A Phase I Study of Intranodally Injected Adenovirus Expressing a Chimeric CD154 Molecule

New therapies for chronic lymphocytic leukemia (CLL) are needed, particularly those that can eradicate residual disease and elicit anti-CLL immune responses. CD40 ligation on CLL cells, which can be achieved using adenovirus encoding chimeric CD154 (Ad-ISF35), enhances their ability to function as antigen presenting cells and increases their sensitivity to clearance by immune-effector mechanisms. In this study, we report the results of a first-in-man Phase I trial of intranodal direct injection (IDI) of Ad-ISF35 in patients with CLL to evaluate toxicity, safety, and tolerability. Fifteen patients received a single IDI of 1-33 x 1010 Ad-ISF35 viral particles (vp), with a defined maximum tolerated dose as 1x1011 vp. Although the most common adverse events were transient grade 1-2 pain at the injection site and flu-like symptoms following IDI, some patients receiving the highest dose had transient, asymptomatic grade 3-4 hypophosphatemia, neutropenia, or transaminitis. Increased expression of death receptor, immune co-stimulatory molecules, and Ad-ISF35 vector DNA was detected in circulating CLL-cells. Notably, we also observed preliminary clinical responses, including reductions in leukemia cell counts, lymphadenopathy, and splenomegaly. Six patients did not require additional therapy for more than 6 months, and 3 achieved a partial remission. In conclusion, Ad-ISF35 IDI was safely delivered in patients with CLL and induced systemic biological and clinical responses. These results provide the rationale for phase II studies in CLL, lymphomas, and CD40-expressing solid tumors.