Acadesine for Patients with Relapsed/Refractory Chronic Lymphocytic Leukemia (CLL): A Multicentre Phase I/II Study

Abstract 4625

CLL - Therapy, excluding Transplantation

Acadesine induces cell death in B-cell chronic lymphocytic leukemia (CLL) cells in a dose-dependent manner. Acadesine enters B-cells where it is phosphorylated to ZMP, which induces apoptosis independently of ATM or p53. It is active in vitro against CLL cells from patients who have not responded to prior treatment with fludarabine and/or chlorambucil.

A phase I/II open-labeled clinical study was designed to determine the safety and tolerability of acadesine given intravenously as a 4-hour infusion to patients with CLL. Part I is the dose escalation part of the study where patients receive a single dose of acadesine on Day 1 and are followed up to Day 22. In Part II, patients will receive up to 5 doses of acadesine at the maximum tolerated dose (MTD) identified in Part I over a period of up to 20 days. Patient population includes CLL patients with relapsed/refractory disease who have received one or more prior lines of treatment including either a fludarabine or an alkylator-based regimen. A patient is defined as having refractory disease if they fail to achieve less than a partial response (PR) according to the NCI working group guidelines, or relapse within the first 6 months after treatment after achieving at least partial response.

Primary endpoints of the study evaluate the safety and tolerability of acadesine. Secondary endpoints evaluate the pharmacokinetics of acadesine and ZMP, and B and T-cell counts in peripheral blood as efficacy biomarkers.

Twenty-one patients have been included to date, eighteen in Part I at doses of 50, 83.5, 139.5, 210 or 315 mg/kg, and three in Part II, with two doses at 210 mg/kg at days 1 and 4. Pharmacokinetic data showed acadesine is rapidly converted into ZMP inside blood cells.

In part I, at single acadesine dose, the Cmax levels for ZMP in whole blood obtained at 315 mg/kg were similar to the ones obtained at the previous dose (210 mg/kg), suggesting that the saturation plateau was reached, which was confirmed by the PK modeling. In 5 patients treated with acadesine at 210 mg/kg and 315 mg/kg a decrease in absolute B cell count was observed, ranging from 6% to 54% with respect to the B cell count prior to acadesine administration. Reversible asymptomatic hyperuricaemia was observed in four patients in cohorts 1 to 3, probably due the metabolism of acadesine to ZMP and uric acid. Prophylactic allopurinol was used in cohorts 4 and 5 and it has significantly reduced the incidence of hyperuricaemia.

Acadesine 315 mg/kg was the dose limiting toxicity (DLT) dose with 2 of 3 patients having DLTs-Tumour Lysis Syndrome (TLS) and clinically significant acute renal failure (CTCAE V3.0 Grade 3-chronic dialysis not indicated).

We started Part II of the study, with two consecutive doses at 210 mg/kg (Optimal Biological Dose). Three patients have been included to date. No DLT nor grade 3 or 4 Adverse Events related to acadesine were observed, and in all of treated patients a decrease in absolute B cell count was observed ranging from 6% to 35% with respect to the B cell count prior to acadesine administration.

In the following cohort, we will administer 5 consecutive doses of acadesine at 210 mg/kg, at days 1, 4, 8, 11 and 15.

In conclusion, a MTD was found at one single acadesine dose. Two consecutive doses have already been tested without safety concerns and 5 consecutive doses are currently planned in part II of this ongoing study. Results for this cohort and additional safety, pharmacokinetics and efficacy data will be presented at the meeting.