Gene therapy-mediated delivery of targeted cytotoxins for glioma therapeutics

Abstract

Restricting the cytotoxicity of anticancer agents by targeting receptors exclusively expressed on tumor cells is critical when treating infiltrative brain tumors such as glioblastoma multiforme (GBM). GBMs express an IL-13 receptor (IL13Rα2) that differs from the physiological IL4R/IL13R receptor. We developed a regulatable adenoviral vector (Ad.mhIL-4.TRE.mhIL-13-PE) encoding a mutated human IL-13 fused to Pseudomonas exotoxin (mhIL-13-PE) that specifically binds to IL13Rα2 to provide sustained expression, effective anti-GBM cytotoxicity, and minimal neurotoxicity. The therapeutic Ad also encodes mutated human IL-4 that binds to the physiological IL4R/IL13R without interacting with IL13Rα2, thus inhibiting potential binding of mhIL-13-PE to normal brain cells. Using intracranial GBM xenografts and syngeneic mouse models, we tested the Ad.mhIL-4.TRE.mhIL-13-PE and two protein formulations, hIL-13-PE used in clinical trials (Cintredekin Besudotox) and a second-generation mhIL-13-PE. Cintredekin Besudotox doubled median survival without eliciting long-term survival and caused severe neurotoxicity; mhIL-13-PE led to ∼40% long-term survival, eliciting severe neurological toxicity at the high dose tested. In contrast, Ad-mediated delivery of mhIL-13-PE led to tumor regression and long-term survival in over 70% of the animals, without causing apparent neurotoxicity. Although Cintredekin Besudotox was originally developed to target GBM, when tested in a phase III trial it failed to achieve clinical endpoints and revealed neurotoxicity. Limitations of Cintredekin Besudotox include its short half-life, which demanded frequent or continued administration, and binding to IL4R/IL13R, present in normal brain cells. These shortcomings were overcome by our therapeutic Ad, thus representing a significant advance in the development of targeted therapeutics for GBM.

Novel Clostridium perfringens enterotoxin suicide gene therapy for selective treatment of claudin-3- and -4-overexpressing tumors

“…[5][6][7][8]10 Apart from diphteria toxin and Pseudomonas exotoxin, other toxins such as streptolysin O and CPE came into focus. The two latter toxins are both pore-forming proteins, of which streptolysin O is rather unspecific, whereas CPE possesses specificity in action.…”

“…4,9 The two toxins were used for the treatment of prostate, pancreatic, ovarian, lung carcinoma and glioblastoma with promising therapeutic efficacies, and exerted also therapeutic efficacy in gene therapy approaches. [5][6][7][8][10][11][12][13][14] Alternatively, the pore-forming bacterial toxins streptolysin O (Streptococcus pyrogenes) and Clostridium perfringens enterotoxin (CPE) came into focus as promising cancer therapeutics. [15][16][17][18] CPE is produced by the anaerobic gram-positive Clostridium perfringens type A strain, known to cause food poisoning.…”

Gene Therapy for the Nervous System: Challenges and New Strategies

“…Using receptor-specific single-chain antibodies fused to a truncated hemagglutinin envelope protein, Anliker et al [66] achieved highly specific for in vivo transduction of neurons with a lentivirus vector. In an innovative approach, Candolfi et al [67] engineered an Ad vector encoding a GBM-specific cytotoxin by fusing a ligand specific for IL-13Rα2 (a tumor specific receptor) to Pseudomonas exotoxin and showed enhanced survival without neurotoxicity in a murine model of human GBM. The groups of Grandi and Glorioso reengineered glycoproteins on HSV including a single chain antibody to target to epidermal growth factor receptors on GBM [68].…”

Maximizing Local Access to Therapeutic Deliveries in Glioblastoma. Part I: Targeted Cytotoxic Therapy

“…To further widen the reach of a targeting agent, we are incorporating mutated IL-13 (IL-13M), which has dramatically altered reactivity toward the normal tissue receptor, IL-13RA1/ IL-4RA, but not toward the tumor-associated receptor, IL-13RA2 (41,(108)(109)(110)(111) into the eA5-Fc construct (Figures 2A and 5A). The very first construct retained an ability to bind to the EphA2 receptor and IL-13RA2.…”