Alemtuzumab and Rituximab for Therapy of Patents with Early Stage High Risk CLL: Report of a Planned Interim Analysis.

The standard of care for CLL is to treat only patients with obvious clinical progression because earlier intervention is not of proven benefit. The discovery of more accurate prognostic markers for CLL could change that paradigm. The predictors of more aggressive disease include 17p13 deletion (17p13−), 11q22-3 deletion (11q22−), unmutated (UM) immunoglobulin heavy-chain variable region (IgV_H), and expression of ZAP-70 and CD38. In addition, monoclonal antibody (MoAb) therapies provide effective treatment with less toxicity than chemotherapy and are likely to be most efficacious in early stage CLL. The combination of alemtuzumab (ALEM) and rituximab (RIT) is of interest because of non-overlapping mechanisms of action. ALEM is also effective therapy for patients with defects in the p53 apoptotic pathway that are more resistance to purine analogue therapy. We tested the hypothesis that MoAb therapy with ALEM and RIT will eliminate/greatly decrease the high risk clone characterized by 17p13−, 11q22−, or UM IgV_H plus either ZAP70+ or CD38+, in early stage CLL.

Methods This trial will enroll a maximum of 30 patients and be considered promising if ≥ 19 patients respond. All patients with previously untreated CLL (Rai stage 0 −II) not meeting NCI-WG 1996 treatment criteria and with a high risk CLL clone were evaluated for enrollment. Treatment duration was 30 days (subcutaneous ALEM dose escalation, 3 mg - 10 mg - 30 mg on days 1–3) then 30 mg Monday, Wednesday and Friday for 4 weeks. RIT (375 mg/m²/dose IV x 4) was administered weekly staring on day 8. All patients received PCP and herpes virus prophylaxis and had CMV viral DNA testing for 7 months. Response was evaluated using NCI-WG 1996 criteria and minimal residual disease (MRD) was measured in peripheral blood using sensitive flow cytometry (1:10⁴) for CD19+/CD5+/CD79b− lymphocytes.

Results Since January 2005, 17 patients have been enrolled and the interim analyses are for the first 11 patients accrued. Median age was 62 years (29 – 75) with 6 males and 5 females. The qualifying high risk features were 17p13− (n = 4), 11q22− (n = 3), and UM IgVH + CD38+ +/− ZAP-70+ (n = 4). Median time from diagnosis to treatment was 11 months (2–72). Clinical stage (Rai) was 0 in 3 patients, I in 5 patients and II in 3 patients. Median absolute lymphocyte count was 25.6 x 10⁹/L (15.9 – 81.8), Hgb 14.4 g/dL (12 – 15.8), and platelet count 171 x 10⁹/L (125 – 312). Two patients had serious adverse reactions requiring intervention (CMV reactivation responsive to treatment; febrile drug reaction to sulfamethoxazole/trimethoprim). Grade 3–4 adverse reactions not requiring interventions were leukopenia (n = 4), neutropenia (n = 2), anemia (n = 1), elevated ALT (n = 1), and skin reaction to ALEM (n =1). There were no “first dose” reactions. All patients responded to therapy with 5 CR (4 of these MRD negative), 3 nodular PR, and 3 PR. Median duration of response has not yet been reached at median follow up of 11.7 months (6.5 – 14.9). Patients with a MRD negative CR had recurrence of detectable MRD at 120 – 210 days after completing therapy but all remain in CR. One patient died off study of complications of a myeloablative allogeneic transplant for progressive CLL.

Discussion ALEM and RIT is effective and tolerable therapy for early stage high risk CLL. All patients responded with 36% achieving a MRD negative CR but serial MRD assays showed that the CLL clone was not deleted. This promising, treatment requires further improvement.