Getting into the AKT

A phase I/Ib trial targeting the Pi3k/Akt pathway using perifosine: Long-term progression-free survival of patients with resistant neuroblastoma

AKT plays a pivotal role in driving the malignant phenotype of many cancers, including high-risk neuroblastoma (HR-NB). AKT signaling, however, is active in normal tissues, raising concern about excessive toxicity from its suppression. The oral AKT inhibitor perifosine showed tolerable toxicity in adults and in our phase I trial in children with solid tumors (clinicaltrials.gov NCT00776867). We now report on the HR-NB experience. HR-NB patients received perifosine 50-75 mg m^-2  day^-1 after a loading dose of 100-200 mg m^-2 on day 1, and continued on study until progressive disease. The 27 HR-NB patients included three treated for primary refractory disease and 24 with disease resistant to salvage therapy after 1-5 (median 2) relapses; only one had MYCN-amplified HR-NB. Pharmacokinetic studies showed μM concentrations consistent with cytotoxic levels in preclinical models. Nine patients (all MYCN-non-amplified) remained progression-free through 43+ to 74+ (median 54+) months from study entry, including the sole patient to show a complete response and eight patients who had persistence of abnormal ¹²³ I-metaiodobenzylguanidine skeletal uptake but never developed progressive disease. Toxicity was negligible in all 27 patients, even with the prolonged treatment (11-62 months, median 38) in the nine long-term progression-free survivors. The clinical findings (i) confirm the safety of therapeutic serum levels of an AKT inhibitor in children; (ii) support perifosine for MYCN-non-amplified HR-NB as monotherapy after completion of standard treatment or combined with other agents (based on preclinical studies) to maximize antitumor effects; and (iii) highlight the welcome possibility that refractory or relapsed MYCN-non-amplified HR-NB is potentially curable.

Perifosine-induced inhibition of Akt attenuates brain-derived neurotrophic factor/TrkB-induced chemoresistance in neuroblastoma in vivo

BACKGROUND

Neuroblastoma (NB) tumors expressing high levels of brain-derived neurotrophic factor (BDNF) and its receptor TrkB or activated Akt are associated with decreased event-free or overall survival in patients with NB. In the current study, the effect of perifosine, an Akt inhibitor, on the chemosensitivity of TrkB-expressing NB cells or tumors was evaluated.

METHODS

A tetracycline-regulated TrkB-expressing isogenic NB cell model system was tested. In this system, NB cells were treated with etoposide and/or perifosine both in vitro and in vivo. Inhibition of the target by perifosine was evaluated by Western blot analysis or kinase activity assay. Cell survival and tumor growth were investigated.

RESULTS

In vitro BDNF treatment induced Akt phosphorylation and rescued cells from etoposide-induced cell death in cells with high TrkB expression, but not in cells with low TrkB expression. Pretreatment of high TrkB-expressing TB3 cells with perifosine blocked BDNF/TrkB-induced Akt phosphorylation and inhibited BDNF's protection of TB3 cells from etoposide treatment. In vivo, tumors with high TrkB expression were found to have elevated levels of phosphorylated Akt and were less sensitive to etoposide treatment compared with tumors with low TrkB expression. Mice treated with a combination of perifosine and etoposide were found to have a statistically significant decrease in tumor growth compared with mice treated with either etoposide or perifosine alone. Activation of Akt through the BDNF/TrkB signaling pathway induced chemoresistance in NB in vivo.

CONCLUSIONS

Perifosine-induced inhibition of Akt increased the sensitivity of NB to chemotherapy. The results of the current study support the future clinical evaluation of an Akt inhibitor combined with cytotoxic drugs for the improvement of treatment efficacy.

Phase II trial of temsirolimus in children with high-grade glioma, neuroblastoma and rhabdomyosarcoma

PURPOSE

A phase II study of temsirolimus was conducted in children and adolescents with high-grade glioma, neuroblastoma or rhabdomyosarcoma.

PATIENTS AND METHODS

Temsirolimus 75 mg/m(2) was administered once weekly until disease progression or intolerance. Using the Simon 2-stage design, further enrolment in each disease cohort required ≥ 2 objective responses within the first 12 weeks for the first 12 evaluable patients (those who received ≥ 3 temsirolimus doses).

RESULTS

Fifty-two heavily pretreated patients with relapsed (12%) or refractory (88%) disease, median age 8 years (range 1-21 years), were enroled and treated. One patient with neuroblastoma achieved confirmed partial response within the first 12 weeks; thus, none of the 3 cohorts met the criterion for continued enrolment. Disease stabilisation at week 12 was observed in 7 of 17 patients (41%) with high-grade glioma (5 diffuse pontine gliomas, 1 glioblastoma multiforme and 1 anaplastic astrocytoma), 6 of 19 (32%) with neuroblastoma and 1 of 16 (6%) with rhabdomyosarcoma (partial response confirmed at week 18). In the three cohorts, median duration of stable disease or better was 128, 663 and 75 d, respectively. The most common treatment-related adverse events were thrombocytopaenia, hyperlipidaemia and aesthenia. Pharmacokinetic findings were similar to those observed in adults.

CONCLUSIONS

Temsirolimus administered weekly at the dose of 75 mg/m(2) did not meet the primary objective efficacy threshold in children with high-grade glioma, neuroblastoma or rhabdomyosarcoma; however, meaningful prolonged stable disease merits further evaluation in combination therapy.