- Some HL cells have a molecule called cluster of differentiation 25 (CD25) on the surface. Daclizumab is a drug that can detect CD25 on cells. In a treatment study for HL that did not respond to chemotherapy, daclizumab plus a radioactive atom called Yttrium 90 helped kill these HL cells. Researchers want to combine this 90Y daclizumab with high-dose chemotherapy and stem cell transplant. This treatment may be more effective than the daclizumab alone.