An Effective and Tolerable Chemoimmunotherapy Regimen For Relapsed/Refractory and Very-High Risk Chronic Lymphocytic Leukemia Combining Alemtuzumab With Pentostatin and Low Dose Rituximab
Authors: Zent Clive S. , LaPlant Betsy R , Wu Wenting , Call Timothy G. , Bowen Deborah , Conte Michael J. , Weiner George J. , Witzig Thomas E 
Published: October 2019

Abstract
Patients with very-high risk (purine analogue refractory and TP53 defective) CLL have limited treatment options. In these patients alemtuzumab can be effective against CLL cells in the circulation and bone marrow, and in combination therapy with fludarabine can be active in patients with bulky disease, but these regimens have a high risk of serious infections. Addition of rituximab to alemtuzumab can also improve efficacy but has limited activity against bulky disease. We conducted a phase II clinical trial to determine the efficacy and toxicity of therapy with pentostatin, alemtuzumab, and low dose higher frequency rituximab (PAR) in patients with relapsed/refractory or progressive CLL with 17p13 deletion. The rituximab schedule was designed to decrease the loss of CD20 expression by circulating CLL cells.

Methods
This two-stage phase II trial study (NCT00669318) conducted at the Mayo Clinic Rochester and University of Iowa with IRB approval had an accrual goal of 38 evaluable patients. Eligibility required a diagnosis of progressive CLL by standard criteria and either previous treatment for CLL (<4 purine analogue regimens) or 17p13 deletion (17p13-). Exclusion criteria were organ failure, poor performance status (ECOG >3), infection with HIV, hepatitis B, hepatitis C, active autoimmune cytopenia, or alemtuzumab therapy within the past 2 months. Rituximab 20 mg/m2 IV M-W-F started on day 1, alemtuzumab started on day 3 with an escalation of 3-10-30 mg/d SQ and then 30 mg M-W-F from day 8, and pentostatin 2 mg/m2 IV every 2 weeks started on day 8. Peg-G-CSF or GM-CSF was used after each dose of pentostatin and patients received Pneumocystis and Varicella prophylaxis. CMV PCR assays were done weekly during treatment and viremia was treated with either valganciclovir or ganciclovir. Cycle 1 was 5 weeks and subsequent cycles were 4 weeks. At the end of cycle 2 patients with a clinical CR had a CT scan and a bone marrow study with immunohistochemical (IHC) staining for residual CLL cells, and therapy was stopped if there was no radiological or IHC evidence of residual CLL (stringent CR). Patients with residual disease received a 3rd cycle of therapy.

Results
Forty-one patients were enrolled (July 2008 - February 2013) and all 39 who started therapy were evaluable for response: Median age 61 years (range 47-78), 30 (77%) males, 36 (92%) relapsed/refractory CLL (median prior regimens = 2, range 1-10), 3 (8%) previously untreated, 23 (59%) advanced stage (Rai III-IV), 16 (41%) intermediate stage (Rai I-II). Prognostic factors: FISH (hierarchical classification) 15 (38%) 17p13-, 6 (15%) 11q22-, 5 (13%) 12+, 3 (8%) no defects, 8 (21%) 13q14-, and 2 (5%) other abnormalities, IGHV analysis (n=38) 27 (71%) unmutated (<2%), ZAP-70 (n=37) 28 (76%) positive (>20%).
Thirty (77%) patients completed planned therapy (28 had 3 cycles, 2 had 2 cycles with stringent CR). Nine patients received one (n=4) or two (n=5) cycles of therapy because of disease progression or complications. Grade 3-4 hematological adverse events (n=37) at least possibly related to treatment included neutropenia (n=22), thrombocytopenia (n=11), anemia (n=2) and hemolysis (n=2). Non-hematological adverse events (n=17) included infections/neutropenic fever (n=8), fatigue (n=3), and hemorrhage (n=2). CMV reactivation was detected and treated in 14 patients (grade 1-2). No patients died during treatment or from treatment related complications.
The overall response rate was 56% (95% CI 40-72) with 4 (10%) CR, 7 (18%) CRi, 11 (28%) PR, 7 (18%) SD, and 10 (26%) PD. Four patients (3 CR and 1 CRi) had IHC negative bone marrow studies. Thirteen (33%) patients have died due to progressive CLL (n = 11), sepsis (n=1), and pneumonia (n=1). Median follow up for surviving patients is 23 months (range 3-55). Seven (18%) patients proceeding to RIC allogeneic transplant were censored for time to next treatment. Twenty-one (54%) patients required therapy for progressive CLL and 7 (18%) have required no further therapy. Median progression free survival was 7 months (95% CI: 5-16), time to next treatment 9 months (95% CI: 6-27) and median overall survival has not been reached.

Discussion
PAR was effective and tolerable therapy for high-risk CLL. This study suggests that alemtuzumab can be used safely in combination with a purine analogue in a short-duration regimen.

Disclosures:
Zent: Genentech : Research Funding; Genzyme: Research Funding; Biothera: Research Funding; GlaxSmithKline: Research Funding; Novartis: Research Funding. Off Label Use: Pentostatin therapy for CLL, use of lower doses of rituximab.