Phase I study of UCN-01 and perifosine in patients with relapsed and refractory acute leukemias and high-risk myelodysplastic syndrome

Abstract

Background: The PI3K-Akt pathway is frequently activated in acute leukemias and represents an important therapeutic target. UCN-01 and perifosine are known to inhibit Akt activation.

Methods: The primary objective of this phase I study was to determine the maximum tolerated dose (MTD) of UCN-01 given in combination with perifosine in patients with advanced acute leukemias and myelodysplastic syndrome. Secondary objectives included safety, pharmacokinetics, pharmacodynamics, and efficacy. Perifosine 150 mg every 6 h was given orally on day 1 followed by 100 mg once a day continuously in 28-day cycles. UCN-01 was given intravenously over 3 h on day 4 at three dose levels (DL1=40 mg/m(2); DL2=65 mg/m(2); DL3=90 mg/m(2)).

Results: Thirteen patients were treated (DL1, n=6; DL2, n=4; DL3, n=3) according to a traditional "3+3" design. Two patients at the DL3 experienced dose-limiting toxicity including grade 3-4 pericardial effusion, hypotension, hyperglycemia, hyperkalemia, constitutional symptoms and grade 5 pneumonitis. Other frequent toxicities were grade 1-2 nausea, diarrhea, vomiting, fatigue and hyperglycemia. The MTD was determined to be UCN-01 65 mg/m(2) with perifosine 100 mg a day. No appreciable direct Akt inhibition could be demonstrated in patients' mononuclear cells using Western blot, however, reduced phosphorylation of the downstream target ribosomal protein S6 in leukemic blasts was noted by intracellular flow cytometry. No objective responses were observed on this study.

Conclusion: UCN-01 and perifosine can be safely administered, but this regimen lacked clinical efficacy. This approach may have failed because of insufficient Akt inhibition in vivo.

Trial registration: ClinicalTrials.gov NCT00301938.

Fig 1. The in vivo effects of perifosine and UCN-01 in leukemia cells

a Western blot shows phospho-Ser473 Akt and total Akt expression among purified mononuclear cells collected from marrow or blood on indicated treatment days. P38 MAPK is shown to ensure equal protein loading. b Table demonstrating the % of leukemia blasts with constitutive p-S6 expression on day 1 and following treatment on days 4 and 29 as measured by intracellular flow cytometry. c Fixed, unfractionated peripheral blood sample from subject #13 shows alterations in S6 phosphorylation downstream of Akt induced by perifosine monotherapy. Lymphoblasts and lymphocytes are discriminated by CD45 antigen density and granulocytes by side scatter. In top right, controls for S6 basal phosphorylation are established by comparing fully stained samples to that of samples lacking pS6 antibody (fluorescence minus one, FMO). PMA stimulated blasts occupy the positive gate, while unstimulated lymphocytes serve as an internal negative control for both CD34 and p-S6 staining. The two bottom panels show blast gate events at baseline and on day 4 of therapy. The percentage of gated events in each region is indicated, illustrating a >50% reduction in +p-S6 events by day 4.