*3.6. RP1*/*2*

RP-1 (by Replimmune Group Inc. Woburn, MA, USA) is a derivative of a wild-type HSV1 isolate containing deletions of γ*34.5* and *ICP47* and expresses GM-CSF and GALV-GP-R- -a fusogenic membrane glycoprotein from gibbon ape leukemia virus that was shown to increase tumor-cell killing potential and immunogenic effects [58]. The viral construct is in clinical trials for recurrent or advanced squamous cell carcinoma (NCT04349436), combinations with the anti-PD-1 antibody cemiplimab (NCT04050436) in recurrent or advanced squamous cell carcinoma, and nivolumab in advanced or refractory solid tumors (NCT03767348) are also under evaluation. A further development on this backbone is the RP2 oHSV, which additionally expresses anti-CTLA-4 [59] and is being tested in combination with nivolumab for advanced or metastatic solid tumors in a phase I study (NCT04336241).
