Pre-Clinical and Interim Results of a Phase II Trial of Perifosine In Patients with Relapsed or Refractory Chronic Lymphocytic Leukemia (CLL)

Abstract 1842

Perifosine (Keryx Biopharmaceuticals) is an oral alkylphospholipid that has been shown to have clinical activity in multiple myeloma and Waldenstrom's macroglobulinemia. Pre-clinical data suggest that its activity is due to inhibition of the Akt signal transduction pathway. The Akt pathway is known to be important for viability in CLL, another B-cell malignancy. Therefore, we investigated the in vitro activity of perifosine in freshly isolated primary CLL cells. CLL patients at the Duke University and Durham VA Medical Centers were enrolled in an IRB-approved research protocol for blood sample collection. CLL cells were negatively selected using the RosetteSep B-cell enrichment cocktail (StemCell Technologies) and a ficoll-Hypaque gradient. This method yields greater than 95% purity of malignant lymphocytes, determined by flow cytometry. Prognostic markers such as IgV_H mutation status, CD38 and ZAP70 expression, and interphase cytogenetics were determined. We found the 50% effective dose (ED50) of perifosine for inducing cytotoxicity in CLL cells after a three-day incubation using the MTS colorimetric assay to be 510 nM (n = 29, range 120 – 1540 nM). CLL cells were obtained from patients with generally poor prognostic markers: 52% CD38+, 93% ZAP70+, 78% IgV_H unmutated, 42% 17p deletion, 8% 11q deletion, 27% trisomy 12, 12% normal, and 12% 13q deletion as a sole abnormality. There were no statistical differences in ED50 between cells obtained from patients in high or low risk prognostic groups. Perifosine induced apoptosis in a dose- and time-dependent manner, measured by Annexin V and PI staining (n = 4). Based upon these pre-clinical results, we initiated a phase II study of perifosine (50 mg orally, twice daily) in relapsed or refractory CLL/small lymphocytic lymphoma (SLL) (NCT00873457). The primary objective of this study is to assess the response rate at 3 and 6 months of perifosine treatment in patients with relapsed or refractory CLL/SLL. Secondary objectives are to monitor toxicity, evaluate overall survival, progression-free survival and response duration, and perform laboratory correlates. Early interim results of this study are presented. Since trial initiation in September 2009, 13 patients have been enrolled. Nine patients had Rai stage III/IV disease at the time of therapy, and 4 patients were fludarabine-refractory. Patients had extensive prior treatment (median 4, range 1 – 11). Many patients had high-risk prognostic features: 9/11 IgV_H unmutated, 10/13 CD38+, and 11/13 ZAP70+. Evaluation of interphase and metaphase cytogenetics demonstrated 4 patients with 17p deletion, two with 11q deletion, 2 with trisomy 12, 4 normal, and 4 with other complex cytogenetic anomalies. Of 12 patients who began therapy, 5 patients withdrew from the study prior to 3 months, 6 patients received at least 3 months of therapy, and 1 patient completed 6 months of therapy. Of the patients who received at least 3 months of therapy, there were 5 patients with stable disease, and one patient with partial response, using iwCLL response criteria. Grade 3/4 toxicities included anemia (n=2), fatigue (n=2), dehydration (n=1), febrile neutropenia (n=1), hyperbilirubinemia (n=1), hyponatremia (n=1), cough (n=1), and dyspnea (n=1). One patient required a dose reduction to 50 mg daily and two patients required dose delays due to toxicities. In conclusion, perifosine has potent in vitro activity against primary CLL cells. Preliminary results of this ongoing phase II study of oral perifosine in relapsed or refractory CLL/SLL demonstrate mostly disease stabilization in a group of very high-risk patients and an acceptable toxicity profile. Completion of this clinical study is necessary to determine if perifosine monotherapy has a potential role in the treatment of CLL/SLL.