Consolidation Therapy with Subcutaneous (SC) Alemtuzumab After Fludarabine and Rituximab (FR) Induction Therapy Improves the Complete Response (CR) Rate in Chronic Lymphocytic Leukemia (CLL) and Eradicates Minimal Residual Disease (MRD) but Is Associated with Severe Infectious Toxicity: Final Analysis of CALGB Study 10101.

Alemtuzumab (Campath-1H) is approved for the treatment of CLL. CALGB sought to determine whether alemtuzumab can improve the CR rate and eradicate MRD after induction chemoimmunotherapy by performing a phase II study administering FR followed by alemtuzumab consolidation to previously untreated, symptomatic CLL patients (pts). We previously reported preliminary toxicity data (Lin et al. ASH 2007) and now report final toxicity and response data.

Pts received fludarabine 25 mg/m² IV on days 1–5, and rituximab 50 mg/m² IV on day 1, 325 mg/m² on day 3, and 375 mg/m² on day 5 of cycle 1 and then only on day 1 of cycles 2–6, repeated every 28 days for up to 6 cycles. Four months after the last fludarabine dose, pts with stable (SD) or responsive disease by NCI 96 criteria received SC alemtuzumab 3 mg on day 1, 10 mg on day 3, and 30 mg on day 5, and then thrice weekly thereafter for 6 weeks (18 total doses). Pts received standard Pneumocystis (PCP) and Varicella zoster virus prophylaxis and were monitored weekly by PCR for Cytomegalovirus (CMV) viremia. When unacceptable serious infectious toxicity was noted in pts who received alemtuzumab after achieving CR from FR induction, the study was amended so that only PR or SD pts received alemtuzumab after FR.

Median age of pts (n=102) was 61 years (range, 23–82), 74% were male, and 30% were Rai stage III/IV. FR was well tolerated; 93% of pts received at least 3 cycles, and 77% completed all 6 cycles. Overall, complete and partial response (OR, CR, PR) rates after FR induction were 90%, 29% and 61%, and 15% were MRD negative by flow cytometry. Fifty-eight pts received alemtuzumab, and 42 (72%) completed the planned 6 weeks of therapy. OR, CR, and PR rates after alemtuzumab (n=58) were 91%, 66% and 26%, and 50% were MRD negative. Twenty-eight of 45 pts (62%) in PR after FR who received alemtuzumab attained CR. Of 11 pts in CR after FR who received alemtuzumab, 5 were MRD negative prior to consolidation and 3 of the other 6 converted to MRD negative afterwards. By intent-to-treat for all patients enrolled, OR, CR, and MRD negativity were attained by 90%, 57% and 42% of pts. With a median follow up of 34 months, median progression free survival (PFS) was 37 months (95% CI, 33–43 months); PFS was 73% and overall survival (OS) 86% at 2 years. Two-year PFS (76% vs 70%, p=0.54) and OS (84% vs 88%, p=0.89) were similar for pts who did and did not receive alemtuzumab. Similarly, there were no differences in PFS or OS among the 30 pts in CR after FR whether or not they received alemtuzumab, although the numbers were small. Grade 3–4 neutropenia and thrombocytopenia were observed in 43% and 19% of pts during alemtuzumab therapy. Grade 3–4 non-hematologic toxicity was observed in 41% of pts, including 19% infections and 19% febrile neutropenia, during alemtuzumab therapy. As we previously reported, 5 pts in CR after FR who received alemtuzumab died from infections (viral meningitis, Listeria meningitis, Legionella pneumonia, CMV and PCP pneumonia), and one pt in PR after FR who received alemtuzumab died of Epstein-Barr (EBV) viremia without evidence of EBV lymphoma. These grade 5 toxicities occurred both during and for up to 7 months after alemtuzumab therapy.

Alemtuzumab consolidation improved the CR and MRD negative rates after FR induction. However, alemtuzumab consolidation resulted in significant toxicity, particularly severe infections in pts who achieved a CR after FR induction. Longer follow up is needed to determine if the improved CR and MRD negative rates following alemtuzumab consolidation will eventually result in improved PFS or OS, especially among pts who achieved a PR after FR induction.

Lin:GlaxoSmithkline: Consultancy, Employment; Genentech: Consultancy; Bayer: Consultancy. Off Label Use: Use of alemtuzumab as consolidation therapy. Byrd:Genentech: Consultancy, Research Funding. Link:Genentech: Consultancy. Rai:Genentech: Consultancy; Bayer: Consultancy.