**2. HSV-1-Derived Oncolytic Viruses in Clinical Trials**

A number of oHSVs have been developed and tested in clinical trials so far. Overall they have shown efficacy, and encouraging responses as exemplified by T-Vec. For clinical trials, GMP-grade virus stocks are injected intratumorally following biosafety procedures. Depending on the trial, the virus may be injected at multiple areas within the same tumor or by repeated intratumoral injections over time; intravenous virus administration has also been evaluated [20].
