Conditionally replicative adenovirus (CRAd)

Conditionally replicative adenoviruses (CRAds) are engineered viral mutants designed to selectively replicate within and destroy cancer cells, sparing normal tissue. These viruses are typically modified in key regions such as E1B-55k (to exploit p53 pathway defects) or E1A-CR2 (to exploit pRb/E2F pathway dysregulation), and sometimes controlled by tumor- or tissue-specific promoters (e.g., hTERT, PSA) to further enhance selectivity. Replication leads to amplification of viral burden, cell lysis, and potential stimulation of anti-tumor immunity. CRAds are under clinical investigation as oncolytic agents, with ONYX-015 as a prominent prototype. They are not a single molecular target but rather a complex biological therapy class dependent on cancer-associated molecular abnormalities for selectivity and efficacy.

Other names

Oncolytic adenovirusOnyx-015dl1520E1B-55k adenovirus mutantE1A-CR2 adenovirus mutantΔ24 adenovirusAdv-TERTp-E1ACG7870 (prostate targeted)tumor-selective adenovirus

Selective viral replication in tumor cells with p53 or pRb pathway defects Direct cytolysis via viral replication/amplification Immunogenic cell death (potential secondary anti-tumor immune effects) Expression of viral proteins (e.g., E3 11.6 death protein) leading to apoptosis or necrosis in cancer cells