Alemtuzumab Achieved Durable Hematologic Response In Heavily Treated T-Large Granular Lymphocytosis Irrespective To STAT3 Mutation Or V-Beta Clone Size

Background T-large granular lymphocytosis (T-LGL) is a rare lymphoproliferative disease characterized by clonal expansion of cytotoxic CD3+CD8+ lymphocytes, presenting with immune mediated cytopenias and associated with autoimmune syndromes. Immunosuppressive therapy (IST) with methotrexate, cyclosporine, or cyclophosphamide can improve the cytopenias in about half the patients but can lead to significant toxicity in older patients. The anti CD52 antibody alemtuzumab is a potent immunosuppressive agent with a good safety profile. We therefore initiated a pilot phase II study to evaluate alemtuzumab as a treatment for T-LGL. Methods 20 consecutive patients with T-LGL were enrolled from October 2006 to August 2012 at National Institutes of Health (www.clinicaltrials.gov - NCT00345345). After a 1 mg test dose, alemtuzumab was administered at 10 mg/dose/day intravenously for 10 days. Peripheral blood, bone marrow, and plasma samples were collected from patients before and at 3 or 6 months after treatment. Blood was analyzed for 1) lymphocytes subsets, T-cell receptor V-beta repertoire and CD57 and CD52 expression by flow cytometry (LSR II, BD, San Jose, California), 2) plasma cytokines using a a magnetic bead based Luminex assay (Affymetrix, CA, USA), 3) STAT3 mutation by direct Sanger sequencing and 4) expression level of 84 genes of the JAK-STAT signaling pathway quantified by PCR array 384 well from SABiosciences (Frederick, MD, USA). Results We report here the results of treatment with alemtuzumab in 20 T-LGL patients enrolled in the first stage of the protocol. Three had associated myelodysplasia (MDS) and two had T-LGL following hematopoietic stem cell transplantation (HSCT). The median age was 61 years (range, 26-82). The median number of prior therapeutic interventions for T-LGL leukemia was 3 (range, 0-7) and the median time from diagnosis to alemtuzumab therapy was 1096 days (range, 18-6054). The median follow-up for all patients is 508 days (range, 99-1481) and for surviving patients 650 days (range, 120-1481). One patient was lost to follow-up 4 months after alemtuzumab therapy. Alemtuzumab was generally well tolerated. Labeled infusion related reactions were common and managed symptomatically. Prolonged and subclinical EBV and CMV reactivations were common but there were no cases of EBV or CMV disease without instituting prophylactic or pre-emptive therapy. Hematological response as defined by protocol was observed in 11 of 20 patients by 3 months after treatment. No patient with MDS or post HSCT responded to alemtuzumab. Four patients relapsed and received a second round of immunosuppression. One patient achieved stable blood counts on cyclosporine, three received alemtuzumab with one patient responding but relapsing 1 year later. STAT3 mutations in the SH2 domain identified in 10 of 20 patients did not correlate with response to alemtuzumab (5 responders and 5 non-responders). Treatment with alemtuzumab reduced significantly the absolute clonal population of T-cytotoxic lymphocytes, as identified by their V-beta receptor phenotype, but they tended to persist in frequency in the peripheral blood of responders. The expanded V-beta clone expressed both CD52 positive and negative cells and both compartments reduced in size after the treatment. When compared with healthy volunteers T-LGL patients had a distinct plasma cytokine signature (IL-12p40, TRAIL, IL22, IP10, MCP1, M-CSF, PDGF-AA, LIF, SCF) as well as JAK-STAT pathway activation prior to treatment but neither was correlated to clinical responses to alemtuzumab, likely due to the various prior IST regimens. Conclusion This is the largest cohort of T-LGL patients treated with alemtuzumab yet reported. Treatment was well tolerated and at this dose minimal side effects were observed. Alemtuzumab treatment in previously heavily treated T-LGL patients results in over 50% response rate and represents a good treatment option for this condition. Disclosures: Off Label Use: Alemtuzumab for T-LGL.