PB1: a low toxicity analog of interleukin-2, an important cytokine already used in cancer immunotherapy. Pivotal's drug is modified to significantly improve the clinical utility of the approved version by decreasing toxicity without reducing efficacy. PB1 has been shown in animal studies to solve the problem of vascular leak syndrome toxicity associated with Chiron's Proleukin®. Pivotal's improved version is expected to allow larger, more therapeutic dosages to be delivered to patients without the life-threatening side effects present in this FDA-approved therapy for renal cancer and melanoma, and which is being increasingly used "off-label" for HIV/AIDS patients with compromised immune systems.
PB3: This LEC/mab fusion protein is a novel, potent immunotherapy agent based on Pivotal's platform LEC technology. The technology creates a fusion protein composed of a cancer-targeting antibody and the CC chemokine LEC (liver-expression chemokine, CCL16), which is a very potent chemoattractant to neutrophils, T-cells, macrophages, B-cells, and dendritic cells. Once at the tumor site, PB3 attracts and amplifies responding lymphoid and dendritic cells capable of inducing an effective anti-tumor immune response to the tumor. In animal studies, PB3 with one targeting moiety has shown efficacy when used alone, and has produced lasting and complete remissions of established colorectal and renal cancer when used in combination with another drug. Experiments with various targeting antibodies are now being developed, and Pivotal expects to license in or enter into joint ventures to obtain one or more promising targeting antibodies to further develop this compound. PB3 was selected by the National Cancer Institute for development in their RAID (Rapid Access to Interventional Development) program.