ALBERT

Description: Purpose: Alemtuzumab (MabCampath) is a humanized monoclonal antibody that targets the CD52 antigen, which is highly expressed on most human B and T lymphocytes. Alemtuzumab has shown considerable activity in both relapsed/refractory CLL and in the frontline treatment setting. In a recent study, treatment with single-agent alemtuzumab induced MRD-negative remissions in 20% of patients with relapsed/refractory CLL (Moreton et al JCO 2005;23:2971–2979). Other studies suggest that MRD negativity can also be attained when alemtuzumab is administered as consolidation for patients with CLL who achieve incomplete initial responses to chemotherapy. Here, we report our long-term experience within a randomized phase III trial that investigates the role of alemtuzumab for consolidation therapy in patients with previously untreated CLL. Methods: Pts in complete or partial remission after induction chemotherapy, with either fludarabine (F) or fludarabine plus cyclophosphamide (FC), were randomized to receive either alemtuzumab 30 mg, 3 times a week for ≤12 wks or no further treatment. Of 21 eligible pts, who had responded to induction with F or FC (1 CR, 1 nPR, 9 PRs), 11 pts (median age: 60 years) randomized to receive alemtuzumab consolidation and 10 to the observation arm. Pts in the alemtuzumab arm received standard premedication and infection prophylaxis with famciclovir and trimethoprim/sulfamethoxazole. Results: After a median follow-up of 48 months, calculated from time of randomization within this consolidation trial, progression-free survival (PFS) was significantly improved for pts who received alemtuzumab consolidation compared to those who received no further treatment (median PFS not reached versus 20.6 months, P = 0.004). PFS from the beginning of induction therapy with F or FC is also significantly greater for patients in the alemtuzumab consolidation arm versus the observation arm. So far, 3 of 11 pts presented with disease progression after alemtuzumab consolidation compared with 8/10 progressing pts in the observation arm. Differences in PFS between both arms were not associated with disease stage before first line treatment, type of first line chemotherapy (F vs. FC) or response status before initiation of consolidation therapy (CR vs. nPR vs. PR). Correlations between achievement of MRD negative responses and PFS is still under investigation and is planned for presentation. With the exception of 2 patients (1 pt in each arm) all patients remain alive. The study was stopped prematurely due to severe infections (7 CTC III infections, which included 4 CMV reactivations, 1 CTC IV infection) in 7/11 patients being treated with alemtuzumab. However, these infections were successfully treated, not associated with the cumulative dose of alemtuzumab, and no late complications of consolidation therapy have been observed. Conclusions: Although based on few pts due to incomplete accrual, long-term PFS was significantly prolonged in patients with CLL receiving alemtuzumab consolidation after first line chemotherapy with F or FC. An ongoing phase I/II trial of the GCLLSG (CLL2i) is currently evaluating the optimal dose and schedule of alemtuzumab in CLL pts after fludarabine-based chemotherapy.

Description: Conventional therapy in CLL is not curative, partly because minimal residual disease (MRD) is usually detectable after therapy. Recent therapeutic approaches achieve higher complete remission (CR) rates, and often aim for MRD eradication as this has repeatedly been shown to predict improved outcome. However, many different MRD techniques have been used to assess response, making it extremely difficult to interpret and compare different clinical trials. The aim of this international collaboration is to develop standardized flow cytometric and PCR approaches to MRD monitoring in CLL that are broadly applicable; to assess their relative sensitivity and specificity in a variety of laboratories; and to establish a standardized reporting convention to facilitate the interpretation of clinical trials. These techniques may be used as a benchmark for assessing response and comparing the efficacy of different therapeutic approaches. PCR approaches using consensus primers to the immunoglobulin heavy chain (IgH) gene are straightforward and frequently used, but have highly variable sensitivity between patients. In the proposed standardized method, the IgH gene is amplified using the BIOMED-2 primers (van Dongen et al, Leukemia 2003, 17:2257) and an allele-specific CDR3 primer is designed. CLL cells are identified by RQ-PCR using the allele-specific oligonucleotide (ASO) primer coupled with intronic JH primers and consensus reporter probes. The amount of PCR product is compared to a single copy housekeeping gene (albumin) to identify the number of CLL cells in the sample. This approach reproducibly quantitates as few as 1 CLL cell in 10,000 other leucocytes, and may provide qualitative information below this level. Multi-parameter flow cytometric analysis with combinations such as CD19/CD5/CD79b/CD20 is reported to have a sensitivity approaching that of ASO-PCR. However, such approaches are less effective in situations where normal B-cells lack CD20, e.g. in patients treated with combinations including rituximab and in normal bone marrow. To circumvent these problems, the group has tested 58 individual four-colour combinations of antibodies identified from protein expression profiling and previously published studies. CD79b/CD43/CD19/CD5, CD81/CD22/CD19/CD5, and CD20/CD38/CD19/CD5 provided the least inter-laboratory variation, independent of methodology. They show low contamination by non-CLL cells and were therefore selected as a core panel for MRD analysis. Dilutional studies indicate that a quantitative sensitivity equivalent for detection of 1 CLL cell in 10,000 leucocytes is achievable; the practical sensitivity is being tested in blinded dilutional analyses. The proposed flow cytometry approach is applicable to all sample types and all therapeutic regimes, and sufficiently rapid and sensitive to guide therapy to an MRD negative status in real time. The PCR approach is highly sensitive but more complex, and is most suited to retrospective response assessment of clinical trials. We have identified the appropriate standardized analytical methods for both techniques and are currently validating these findings. These approaches will allow direct comparison of efficacy between different clinical trials, allowing more rapid international progress towards identifying a curative approach.