OBJECTIVES: Adult patients with refractory/relapsed ALL have poor survival outcomes with current chemotherapies. We aimed to determine safety and efficacy of lenalidomide, an oral immunomodulator, in these patients. METHODS: This phase 1/2 trial (EUDRACT # 2009-009372-13) included 10 patients who received 28-day cycles of oral lenalidomide 25 mg/day, days 1 through 21, in combination with oral dexamethasone 40 mg/day on days 1, 8, 15, 22. Primary endpoints were tolerance and the overall response rate (ORR). Secondary endpoints included overall survival (OS) and quality of life. RESULTS: The most common grade 3 or 4 adverse events were myelosuppression. The ORR among the participants who could be evaluated was 28.6% (95% confidence interval [CI], 0-62.2%). The median OS was 92 days (range, 43-133 days). All patients have died because of progressive disease. Quality of life remains stable during treatment cycles. DISCUSSION AND CONCLUSION: The safety of combination therapy consisting of lenalidomide plus dexamethasone is consistent with ambulatory administration. Efficacy should be reevaluated in a larger series including patients less intensively previously treated