A Phase I Study of CHR-2797, an Orally Active Aminopeptidase Inhibitor in Elderly and/or Treatment Refractory Patients with Acute Myeloid Leukemia or Multiple Myeloma.

Background. CHR-2797 is a novel, orally bioavailable agent which displays potent, tumor cell-selective, anti-proliferative properties. It is an inhibitor of Zn⁺⁺-dependent aminopeptidases and generates signs of amino acid deprivation in sensitive cells, decreased protein synthesis and an increase in the level of the pro-apoptotic protein, NOXA. CHR-79888 is an active metabolite of CHR-2797.

Methods. This was an open label, single agent, dose escalating phase I salvage study to assess tolerance, MTD/DLT, activity, and pharmacokinetics of CHR-2797 in patients with hematological malignancies. Elderly patients and/or relapsed patients with acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), and multiple myeloma (MM) were eligible. Patients were treated with escalating once daily doses (60–180 mg) for up to 84 days or until progressive disease (PD). Clinical responses were assessed by monthly bone marrow aspirates in AML/MDS patients and by M-protein levels in MM patients.

Results. Sixteen adults (4 women, 12 men) of median age 70 yrs, (range 45–84 yrs) were accrued between May 2006 and Jan 2007: 13 patients with AML, 1 with MDS, and 2 with MM. Thirteen patients finished the dose finding phase of 28 days and 6 patients continued for at least 84 days. CHR-2797 was well tolerated and, except for one patient with grade III ALT elevation, no grade III/IV drug related non-hematological toxicity was observed during the first 28 days of treatment. Two patients on 180 mg developed DLT that was considered drug related: >75 percent reduction in platelet count. CHR-2797 had no influence on hemoglobin or neutrophils in this trial. Overall the most frequently reported adverse events were thrombocytopenia (6.7%), diarrhea (4.5%), dizziness (3.9%), and fatigue (3.9%). Five AML patients died in the first 3 months of the trial or within 4 weeks of discontinuing CHR-2797: 3 due to disease progression and 2 following a MI (not related to drug). Bone marrow studies revealed complete responses (< 5% blasts in bone marrow) in 3/12 AML patients after 1–3 months of therapy (60 and 130mg), one of which was also a cytogenetic response. One of the 2 responding patients on 130 mg was evaluated as a CRp at 3 months; this patient was in remission for 3 months following platelet recovery after the drug was stopped. One further AML patient (60 mg) became completely transfusion independent and remained so for 6 weeks. Good exposure to CHR-2797, including levels of the active metabolite CHR-79888 has been observed on days 1 and 28 with a terminal half life (for 79888) of 8– 11 hours.

Conclusions. Oral once daily CHR-2797 in AML/MDS/MM patients with adverse prognostic risk was well tolerated. MTD for maintenance therapy was reached at 180 mg. Single agent CHR-2797 therapy showed encouraging clinical activity (incl. 3/12 CRs) in these elderly and poor risk AML patients who were able to continue therapy for at least 28 days. Because of the favorable results a phase II study with CHR-2797 in advanced AML is currently in progress.