Bevacizumab-Primed Vascular Normalization Enhances Intratumoral Delivery and Efficacy of the tBID-Armed Oncolytic Adenovirus KD01 in Glioma.

BACKGROUND

Malignant gliomas remain largely refractory to current therapies, in part because abnormal tumor vasculature and a disrupted blood-brain barrier limit intratumoral drug delivery and cause severe tumor-associated edema. The oncolytic adenovirus KD01 is a conditionally replicating adenovirus type 5 with a 27-bp deletion in Early Region 1A (E1A) and a truncated BH3-Interacting Domain Death Agonist (tBID) expression cassette inserted into the E3 region. This study investigated whether bevacizumab-induced vascular normalization would enhance the delivery and efficacy of KD01 in gliomas.

METHODS

The oncolytic activity and mitochondrial effects of KD01 were evaluated in human glioma cell lines using cell viability assays, JC-1 staining, quantitative real-time-polymerase chain reaction (qRT-PCR), and western blotting for BID/tBID. An orthotopic LN229 nude mouse model was used to assess a sequential bevacizumab→KD01 regimen. Mice were randomized to receive PBS, bevacizumab, KD01, or combination treatment. Body weight and survival were recorded. Tumor cell proliferation (Ki-67), tumor vasculature (CD31), brain water content (ΔWater%), serum biochemistry, coagulation parameters, and organ weights were analyzed to evaluate antitumor activity, edema, and systemic safety.

RESULTS

KD01 induced robust dose- and time-dependent cytotoxicity in glioma cells and caused marked mitochondrial depolarization, accompanied by increased BID mRNA expression, loss of full-length BID, and accumulation of tBID. In the orthotopic LN229 model, bevacizumab administered 48 h before KD01 significantly improved overall outcomes compared with either monotherapy. The bevacizumab→KD01 group showed improved preservation of body weight, pronounced prolongation of survival, and the lowest Ki-67 labeling index. This group also exhibited reduced brain water content (ΔWater%), consistent with sparser CD31-positive vessels resulting from vascular normalization and oncolysis, indicating effective attenuation of tumor-associated edema. Serum liver and kidney function tests, platelet counts, coagulation indices, and major organ weights were comparable across treatment groups, suggesting no additional systemic toxicity associated with combination treatment.

CONCLUSIONS

KD01 exerts potent tBID-mediated mitochondrial oncolytic activity against glioma cells. When used as a priming strategy, transient vascular normalization induced by bevacizumab enhanced the intratumoral efficacy of KD01 in an orthotopic glioma model while maintaining a favorable safety profile. These findings support a simple, sequence-dependent combination approach integrating anti-VEGF therapy with oncolytic virotherapy for the treatment of malignant gliomas.