Multicenter Phase II Study of Lenalidomide in Patients with Relapsed Adult T-Cell Leukemia-Lymphoma

Introduction: Adult T-cell leukemia-lymphoma (ATL), a distinct subtype of peripheral T-cell lymphoma (PTCL), is caused by human T-lymphotropic virus type-I (HTLV-1). Although rare in the rest of the world, ATL accounts for 25% of PTCL cases diagnosed in Japan, where ATL cases are clustered in areas endemic for HTLV-1 infection. Studies of lenalidomide, an oral immunomodulatory agent that has antiproliferative and direct antineoplastic activity in cutaneous T-cell lymphoma and PTCL, have reported encouraging clinical activity. On the basis of the results from the ATLL-001 dose-finding study of lenalidomide (Uike et al. ASH 2012. Abstract 2737), this multicenter phase II study (ATLL-002) was designed to investigate the efficacy and safety of single-agent lenalidomide in Japanese patients with relapsed ATL.

Methods: Patients with relapsed acute, lymphoma, or the unfavorable chronic subtype of ATL who were at least 20 years of age, had ECOG performance status 0-2, no prior allogeneic stem cell transplant, and who had failed at least 1 chemotherapy were included in the study. Patients refractory to their last prior therapy were excluded. Treatment consisted of oral lenalidomide 25 mg/day administered continuously until disease progression or unacceptable toxicity. The primary endpoint was overall response rate (ORR). The secondary endpoints were progression-free survival (PFS), duration of response (DOR), overall survival (OS), and safety. Response was assessed by central review using the criteria proposed by Tsukasaki et al in their international consensus report (J Clin Oncol. 2009;27:453-459.); safety was assessed per NCI CTCAE v4.0 criteria. The estimated number of patients required was 25, for 90% power to detect a lower limit of the 95% confidence interval (CI) exceeding the 5% threshold of ORR, based on the assumptions that the minimum required ORR to a new drug for relapsed or recurrent ATL is 5% and the expected ORR to lenalidomide is 25%.

Results: Twenty-six patients were enrolled and received lenalidomide. The median age was 68.5 years (range, 53-81), with 15 (58%) acute, 7 (27%) lymphoma, and 4 (15%) unfavorable chronic type ATL patients. Patients had received a median of 2 (range, 1-4) prior chemotherapeutic or antibody agents for ATL, 11 (42%) of whom received prior mogamulizumab (anti-CCR4 antibody). At a median 3.8-month follow-up, lenalidomide met the primary endpoint by exhibiting an ORR of 42% (11/26; 95% CI, 23-63) (acute 33% [5/15], lymphoma 57% [4/7], unfavorable chronic 50% [2/4]), including 5 (19%) complete responses (CR)/CR unconfirmed (95% CI, 7 to 39; Table 1). Stable disease was 31%, and progressive disease was 27%. The median time to response was 1.9 months (95% CI, 1.8 to 3.7). Although the data were immature at the time of analysis, median DOR for all responders was not reached (NR) (95% CI, 0.5 months to NR), median PFS was 3.8 months (95% CI, 1.9 months to NR), and median OS was 20.3 months (95% CI, 9.1 months to NR). At the time of the data cut-off, 5 (19%) patients remained on lenalidomide treatment. The most common grade 3/4 adverse events (AEs), accounting for at least 10% of all cases, were neutropenia (65%), leukopenia (39%), lymphopenia (39%), thrombocytopenia (23%), anemia (19%), and hypokalemia (12%). Serious AEs were reported in 9 (35%) patients; only thrombocytopenia (2 patients [8%]) was observed in >1 patient. AEs led to dose reduction/interruption in 17 (65%) patients and study discontinuation in 6 (23%). Seven deaths occurred during the study, 6 due to disease progression and 1 due to pneumonia unrelated to lenalidomide treatment.

Conclusions: In this multicenter, open-label, phase II study, lenalidomide monotherapy demonstrated a 42% ORR and acceptable tolerability profile. These results support the potential for lenalidomide monotherapy becoming a treatment option for patients with relapsed ATL.

Table 1. Best response to lenalidomide in relapsed ATL

ATL type	All patients (N = 26)	Acute (n = 15)	Lymphoma (n = 7)	Unfavorable chronic (n = 4)
ORR, n (%)	11 (42)	5 (33)	4 (57)	2 (50)
CR/CRu, n (%)	5 (19)	3 (20)	2 (29)	0
PR, n (%)	6 (23)	2 (13)	2 (29)	2 (50)
SD, n (%)	8 (31)	6 (40)	0	2 (50)
PD, n (%)	7 (27)	4 (27)	3 (43)	0

CR, complete response; CRu, CR unconfirmed; ORR, overall response rate; PD, progressive disease; PR, partial response; SD, stable disease.