Eradication of Minimal Residual Disease Using Alemtuzumab Consolidation After High-Dose Methyl-Prednisolone Plus Rituximab (HDMP-R) Is Safe, Effective and Induces Long Term Remission in Chronic Lymphocytic Leukemia

Abstract 2866

Despite advances in the treatment of patients with chronic lymphocytic leukemia (CLL), the disease still remains incurable and eradication of minimal residual disease (MRD) being one of the most challenging goals of treatment. Alemtuzumab (Campath-H1™) has been shown to effectivily eradicate MRD from the bone marrow and induce long-term remissions, however its use is limited to patients without bulky disease. Futhermore, combination of alemtuzumab with chemotherapy has resulted in serious adverse events.

In this study, we evaluate the toxicity and efficacy of alemtuzumab as consolidation therapy for CLL patients following induction with high-dose methylprednisolone in combination with rituximab (HDMP-R).

Twenty-one patients with evidence of residual disease after treatment with HDMP-R received additional treatment with alemtuzumab. This antibody was administered three times a week for a total of 8 weeks. Patients received antibiotic prophylaxis with trimethoprim-sulfamethoxazole 160/800 mg twice a day × 3 per week, fluconazole 100 mg / day and valganciclovir 900 mg / day. The median age was 60 years (range, 49–73), with Rai stage III-IV in 81% of the patients. Twelve patients (57%) had evidence of unmutated IgV_H gene and thirteen (62%) had high level of ZAP-70 expression. Cytogenetic and FISH analysis showed eight patients with deleletion 13q, three patients with trisomy 12, one patient with deletion 11q, five patients with no chromosomal abnomalities and in six patients data was not available. The median number of previous treatments was 1.3 (range, 0–5) and the median time from the end of HDMP-R treatment to initiation of alemtuzumab was 5 months (range, 1–14).

After HDMP-R, nine patients (43%) achieved CR and twelve (57%) were in PR; all of them had evidence of residual disease in the bone marrow by 4-color flow cytometry analysis. Eight additional patients achieved CR after consolidation with alemtuzumab for a total of 17 patients (81%) in CR at the end of the study. We found no evidence of MRD (MRD^neg) in 12 of those patients (57% of the total and 71% of CR patients). Of the remaining patients, one had PR and three patients had progressive disease for an overall response rate of 86%. The median progression-free survival (PFS) was 63 months (range, 6–84) for all patients. The median PFS in CR MRD^neg patients has not been reached at a median follow-up of 46 months (range, 18–84), with 8/12 patients that have not progressed after a time at risk of 3.8 years. CR MRD^pos patients have a median PFS of 48 months (range, 6–48).

The treatment was well tolerated and there were no deaths attributed to therapy. Adverse events were classified following the NCI common terminology criteria for adverse events (CTCAE) Version 4.0. Two patients (9.5%) developed infections. The first event occurred during the administration of alemtuzumab and required hospitalization of the patient for management of pneumonia galactomannan positive suspicious for invasive aspergillosis (Grade 3), the second event was in a patient with aspegillus sp. infection of the skin that occurred four months after completion of alemtuzumab (Grade 2). Both patients recovered completely. We observed no CMV or other opportunistic infections. Three patients (14%) developed cytopenias; two patients with (Grade 4) thrombocytopenia and three patients with (Grade 4) neutropenia.

In conclusion, alemtuzumab consolidation for residual disease after treatment with HDMP-R was well tolerated and effective in patients with CLL. We observed a near two-fold increase in the number of patients that achieved CR and the majority of these (71%) had no evidence of MRD. Moreover, patients with CR MRD^neg have an exceptionally long PFS. The low rate of infection and lack of treatment related mortality compares very favorably with previous studies using alemtuzumab consolidation after chemotherapy treatment in which toxicities including treatment related death were found to be prohibitive. These encouraging results provide the rationale for additional studies using this combination therapy.