Clinical Activity of Azacitidine In Combination with the Oral mTOR Inhibitor Everolimus (RAD001) In Relapsed and Refractory AML: Interim Analysis of a Phase Ib/II Study

Although the demethylating agent azacitidine has an established role in myelodysplastic syndromes and encouraging activity in oligoblastic acute myeloid leukemia (AML), information regarding its role in relapsed and refractory AML is still emerging. The French ATU reported an overall response rate (ORR; CR/CRi+PR) in relapsed and refractory AML of 11% (Itzykson et al. ASH 2009 #1054). In a similar population, azacitidine salvage therapy produced a CR/CRi rate of 19% (Ayari S, et al. ASH 2009 #2044). Rapamycin, an inhibitor of the AKT downstream target mammalian Target Of Rapamycin (mTOR), is reported to specifically target leukemic stem cells and orally bioavailable rapamycin derivatives, such as everolimus (RAD001), are in active clinical development. Clinical responses with single agent everolimus in relapsed, refractory AML, however, have been modest (Yee et al, Clin Cancer Research 2006 and Boehm et al, European Journal of Internal Medicine 2009).

Building on our experience combining everolimus with low dose cytarabine (submitted to ASH, 2010), we have sought to investigate the feasibility and preliminary efficacy of combining everolimus with azacitidine in relapsed and refractory AML.

Phase Ib/II open label dose escalation study. Patients were treated with azacitidine 75 mg/m² s.c. daily on days 1–5 and 8–9 of each 28-day cycle with either 2.5, 5 or 10 mg everolimus orally on days 5–21 for a maximum of 12 cycles.

This preliminary analysis includes 20 patients (M 14, F 6), median age 64 years (range 17–76) receiving 2.5 mg (n=6), 5 mg (n=12) or 10 mg (n=2) everolimus. 9 (45%) had chemotherapy refractory and 11 (55%) relapsed AML after 1 (n=8), 2 (n=10) or 3 (n=2) previous lines of therapy. 7/17 (41%) had poor risk and 10/17 (59%) intermediate risk cytogenetics. 6/19 (32%) had secondary AML. The overall response rate (ORR) in 14 evaluable patients was 36% (2 CR, 3 PR). Stable disease (SD) was observed in 7 (50%) patients and 2 (14%) had progressive disease. Absolute bone marrow blast reductions from baseline in the 5 responders ranged from 9 to 88% (Figure 1). Grade 3/4 non-hematologic toxicities are summarized as follows: 2.5 mg everolimus cohort- septicemia (n=1) and mucositis (n=1, dose limiting toxicity; DLT), 5 mg everolimus cohort- septic arthritis (n=1, DLT). Febrile neutropenia during the first cycle of therapy was reported in 5/20 (25%). Safety analysis in the 10 mg everolimus cohort is ongoing. With a median follow up of 82 days, 30 day mortality was 0%. Enrolment continues to a planned 40 patients. Of interest, 2 out of 3 patients with FLT3-ITD+ AML refractory to high-dose cytarabine and antracyclines, had a striking reduction in bone marrow blasts after commencing azacitidine + everolimus (2.5 mg) therapy, with the absolute blast count falling from 95% to 16% and 92% to 5%, respectively, and lasting for at least 5 months in both. One of these patients has so far proceeded to allogeneic stem cell transplant (allo-SCT). Another patient with 3^rd relapse of AML after failing allo-SCT, achieved CR after 3 cycles of treatment with azacitidine + everolimus (2.5 mg) and remains in CR after 157 days.

Figure 1.

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Azacitidine + RAD001-Bone marrow response

Figure 1.

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Azacitidine + RAD001-Bone marrow response

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In relapsed and refractory AML, azacitidine in combination with the mTOR inhibitor everolimus was well tolerated and demonstrates substantial clinical activity in this advanced AML population. Further evaluation of this promising combination is ongoing.

Wei:Novartis: Advisory board, Research Funding; Celgene: Research Funding. Off Label Use: AML therapy. Catalano:Celgene: Research Funding; Roche: Honoraria, Research Funding, Travel Grants.