A Phase 1 Study of Sequential Idarubicin + Cytarabine, Followed by Lenalidomide, in Patients with Previously Untreated Acute Myeloid Leukemia (AML)

Lenalidomide (Len) is an immunodulatory agent with proven efficacy in lower-risk myelodysplastic syndromes (MDS) and with strong signals of single-agent activity in higher-risk MDS and AML patients (pts). Our preclinical data showed that Len antagonized cytarabine cytotoxicity with simultaneous exposure, while augmenting the effects of anthracyclines and cytarabine with sequential drug exposure. We initiated a phase 1 combination study in patients with AML investigating sequential standard induction chemotherapy followed by Len.

1) to determine the safety and maximum tolerated dose (MTD) of Len following idarubicin/cytarabine induction. 2) to assess preliminary signs of efficacy of this regimen in adults with previously untreated AML.

This was a multicenter, open-label, dose escalation phase 1 study with a 3+3 dosing design of idarubicin (12 mg/m², day 1–3), cytarabine (100 mg/m², CI day 1–7) + Len (starting dose 5 mg, day 8–21). Len dose was escalated in 5 mg increments up to a maximum of 25 mg/day. Eligibility included pts with AML age ≥60 years or age <60 with associated del 5/5q; or MDS/RAEB-2 with prior hypomethylating agent failure. Other inclusion criteria included: ECOG PS 0–2 and adequate end-organ function (including normal LVEF of ≥ 50%). Pts who achieved CR/CR_i after 1 or 2 cycles of induction were eligible to receive post-remission idarubicin/cytarabine/Len (at the same dose level) for up to 2 cycles, followed by Len maintenance 10 mg/day for up to 12 months. The MTD cohort was expanded to 10 patients.

Of 23 enrolled and treated pts, 21 have completed at least 1 treatment cycle. Median age was 68 years (range 44–79); males: 18 (78%). Eleven pts had del 5/5q associated karyotype (10 of whom had complex karyotype), and 15 had secondary AML (including 8 who received prior hypomethylating agents). Len dose escalation reached 25mg/day, with MTD determined to be 20 mg/day. Dose-limiting toxicities occurred in 2 of 3 patients treated at Len 25 mg/day (grade 3 rash; grade 4 neutropenia and thrombocytopenia persisting beyond day 56) and in 1 of 8 patients treated at Len 20 mg/day (grade 4 cardiac ischemia). Only 1 of 21 (5%) patients died within 30 days of treatment initiation. The most common therapy-related non-hematologic toxicities (occurring in ≥ 20% of patients, the vast majority of which were grade 1–2) included: diarrhea (76%), infection/febrile neutropenia (71%), rash (62%), nausea (43%), pain (43%), hemorrhage (33%), fatigue (29%), and non-neutropenic fever (24%). Of the 20 patients evaluable for response, 7 achieved CR and 1 CR_i, for an overall response rate (ORR) of 40%. Of 11 evaluable patients treated at the MTD (Len 20 mg/day) and higher, the ORR was 55%. CR occurred in 3 out of 10 (30%) patients with associated del 5/5q.

Sequential idarubicin/cytarabine + Len was generally well-tolerated in a primarily older population of patients with previously untreated AML, with MTD of 20 mg/day for Len. Clinical activity in this poor-risk population appears promising at the MTD and higher. Further exploration of this regimen in older AML patients is warranted, with plans for a phase 2 expansion underway. Updated toxicity, response, and survival data will be presented.

Lancet:Celgene: Research Funding. Off Label Use: Lenalidomide is approved for use in MDS. Its investigational role in AML will be discussed. Komrokji:Celgene: Honoraria, Research Funding, Speakers Bureau. Sekeres:Celgene: Advisory Board. List:Celgene: Consultancy.