The answer is D. Ipilimumab.
Amifostine, pentoxifylline, and palifermin are all types of radioprotectants.
Ipilimumab is a CTLA-4 inhibitor that has shown promise in clinical trials to improve some patients’ response to radiation therapy. Several recent trials have suggested that combining radiation with immunotherapy, primarily checkpoint inhibitors, may have a synergistic effect on metastatic melanoma by preventing tumor cells from evading the immune response through several mechanisms.
For more information about checkpoint inhibitors and how they work, watch a short video.