Abstract 2660: Targeting an attenuated cytokine to tumor cells via antibody fusion results in enhanced tumor killing with significantly reduced off-target activity
Authors: Pogue Sarah L. , Taura Tetsuya , Bi Mingying , Mikesell Glen , Yun Yong , Sho Angela , Behrens Collette , Stevens Maxwell , Domagala Teresa , Sokolovsky Maya , Hallak Hussein , Rosenstock Moti , Doyle Anthony , Wilson David S. 
Published: May 2015

Abstract
Many cytokines have potential therapeutic applications and several, including interferon (IFN)α and IFNβ, have been approved for the treatment of cancer and/or autoimmune disease. While these agents are effective, they are associated with significant dose-limiting toxicities that prevent their use at levels sufficient to promote optimal therapeutic benefit. The toxicity of type I interferons, like other cytokines, is likely mediated via cognate receptor activation on cells other than those that mediate their therapeutic effects. For example, IFNα2b, which is indicated for the treatment of multiple myeloma (MM), has a narrow therapeutic index due to significant systemic toxicity. Approaches that seek to minimize dose-limiting systemic toxicity while maximizing tumor-specific cytokine exposure could greatly enhance the therapeutic index and effectiveness of type I IFNs and other cytokines.
Other groups have previously shown that a moderate degree of tumor-specificity can be achieved by attaching a cytokine such as IFNα to a tumor-targeting antibody; such first generation antibody-targeted cytokines are highly active but show only moderate tumor-specificity since the cytokine can still potently stimulate its receptor on antigen-negative cells. We sought to improve the therapeutic index of antibody-targeted cytokines by mutating the cytokine portion to significantly reduce affinity for its receptor, thereby making it more dependent on antibody-based cell-targeting. Here we demonstrate that such fusion proteins, consisting of mutant or attenuated cytokines (Attenukines™) attached to tumor-targeting antibodies, are 1,000 to 100,000-fold more potent on target-positive cells compared to target-negative (normal) cells. This is shown for antibody-Attenukine™ fusion proteins based on multiple tumor antigens (CD20, CD38, CD138, HMW-MAA, HLA) and multiple attenuated mutants of IFNα, IFNβ, IL-4 and IL-6. Furthermore, we have evaluated an anti-CD38-attenuated IFNα molecule (anti-CD38-Attenukine™) in various CD38+ MM xenograft models and found that this molecule retains potent tumor-targeting activity and anti-tumor efficacy. Moreover, in non-human primates, we have confirmed that the attenuating mutation in IFNα indeed decreases non-targeted IFNα biomarker responses by greater than 100-fold. Taken together, our findings suggest that the administration of antibody-attenuated cytokine fusion proteins to cancer patients may promote robust cytokine-dependent tumor-killing while minimizing systemic toxicity.
Citation Format: Sarah L. Pogue, Tetsuya Taura, Mingying Bi, Glen Mikesell, Yong Yun, Angela Sho, Collette Behrens, Maxwell Stevens, Teresa Domagala, Maya Sokolovsky, Hussein Hallak, Moti Rosenstock, Anthony Doyle, David S. Wilson. Targeting an attenuated cytokine to tumor cells via antibody fusion results in enhanced tumor killing with significantly reduced off-target activity. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2660. doi:10.1158/1538-7445.AM2014-2660