Intense Reversal of Bone Marrow Angiogenesis after Consolidation Therapy with Alemtuzumab in Advanced Chronic Lymphocytic Leukemia.

We evaluated microvessel area of bone marrow (BM) samples from 20 patients with advanced CLL (i.e., symptomatic Binet stage A, B or C) who received at least 8 weeks, after the end of treatment with fludarabine, subcutaneous alemtuzumab, three times weekly for 6 weeks, at escalating dose up to 10 mg. The patient sample included 14 males and 6 females with a median age of 51 years (range 44–60). After a median number of 6 cycles of fludarabine (range, 4–13), 11 (55%) patients could be classified in complete remission (CR) and 9 (45%) in partial remission (PR) (7 nodular-PR and 2 PR). Interestingly, the rate of CR increased to 90% (18 CR; P=0.03; Fisher’s exact test) after treatment with alemtuzumab. In keeping with hematological responses, significant changes in BM microvessel area were observed The decrease of BM angiogenesis, observed virtually in all patients, was a continuous process characterizing the sequential use of fludarabine and alemtuzumab (P = 0.002; Kruskal-Wallis test). This conspicuous feature was easily demonstrable in either ZAP-70-positive (P = 0.02) or ZAP-70-negative (P = 0.001) patients.

Residual disease was assessed using a consensus polymerase chain reaction (PCR) methodology to detect the clonality of IgH sequences. Thirteen out of 20 (65%) patients changed from a monoclonal to a polyclonal pattern of IgH after alemtuzumab consolidation. We wondered whether molecular response could translate into a change in the BM microvessel area. A separate evaluation carried out in patients with a persistent monoclonal pattern and in those who changed to a polyclonal pattern of IgH after alemtuzumab therapy showed a significant reduction of BM microvessel area only in the latter (P = 0.0002).

A new information provided by the present study concerns the impact of the cumulative dose of alemtuzumab on either molecular response or reduction in BM angiogenesis. Analysis carried out after setting as cut-off the median cumulative dose of alemtuzumab (i.e., 184 mg; range, 134–187) revealed a dose-response relationship. Only two (15.3%) out of 13 patients who received a cumulative dose of alemtuzumab higher than 184 mg had persistent monoclonal IgH in comparison to 5 (71.4%) out 7 patients who had received a cumulative dose of alemtuzumab lower than median (P = 0.007). Similarly, a significant decrease in the extent of microvessel area was observed among patients whose cumulative dose was equal or higher than 184 mg (P = 0.0001) while the same did not apply for a cumulative dose of alemtuzumab lower than 184 mg (P = 0.09).

Overall, these data demonstrate a decrease in BM vascularity after treatment with alemtuzumab, which reflects both molecular response and cumulative dose of this drug, and suggest a potential use of alemtuzumab as anti-angiogenic agent in the treatment of advanced CLL.