Sentence: Pharmacokinetic studies showed that chronic lymphocytic leukemia involving more than 80 % of the bone marrow at study start was associated with lower trough concentrations of alemtuzumab and rituximab , and that higher trough serum concentrations of alemtuzumab were associated with complete bone marrow clearance .
Drug combination annotation:
[{'class': 'POS', 'spans': ['alemtuzumab', 'rituximab'], 'is_context_needed': True}]