According to the company, Provecta was injected once into one to 20 tumors in each subject. In addition to these treated tumors, an additional one to three tumors were left untreated in each subject to allow assessment of a potential bystander effect resulting from immune system response to tumor treatment.
A total of 114 tumors were injected and 39 bystander tumors were observed in the study. Subjects were followed for 4 to 27 weeks. Study treatments were well tolerated and elicited minimal side effects, the most common being mild to moderate pain at the injection site.
At final evaluation after injection with a single dose of Provecta, the following results were obtained: 20% of subjects achieved complete response of their injected tumors, 20% achieved partial response, 35% achieved stable response and 25% achieved progressive disease, corresponding to an objective response (CR+PR) in 40% of subjects and local disease control (CR+PR+SD) in 75% of subjects.
Among those subjects achieving an objective response of their treated tumors, 25% achieved an objective response of their untreated bystander tumors, and 100% exhibited disease control in their bystander tumors. In contrast, for those subjects failing to achieve an objective response of their treated tumors, only 8% achieved an objective response of their bystander tumors, and 92% exhibited progressive disease in their bystander tumors.
These differences in response of bystander lesions as a function of response of target lesions were statistically significant and support the occurrence of a bystander effect in subjects whose target lesions have been responsive to PV-10 chemoablation, according to Provectus.