Sentence: We validated these initial findings in samples collected in a clinical trial comparing the nucleoside analog fludarabine alone or in combination with the alkylating agent cyclophosphamide in untreated CLL samples collected prior to starting therapy ( E2997 ) .
Drug combination annotation:
[{'class': 'COMB', 'spans': ['fludarabine', 'cyclophosphamide'], 'is_context_needed': True}]