Blinatumomab/Lenalidomide in Relapsed/Refractory Non-Hodgkin's Lymphoma: A Phase I California Cancer Consortium Study of Safety, Efficacy and Immune Correlative Analysis

Introduction

Both blinatumomab and lenalidomide have proven, but limited, efficacy in relapsed/refractory (R/R) non-Hodgkin's lymphoma (NHL). Failure of blinatumomab to mediate durable responses is due to its inability to recruit competent cytotoxic T cells which leads to eventual T cell exhaustion. Lenalidomide has been shown to improve efficacy of rituximab through T and NK cell activation even in patients who have previously failed rituximab containing regimens. Based on this, we hypothesized that lenalidomide, when combined with blinatumomab, will enhance its efficacy. We report safety, efficacy and correlative analysis of blinatumomab and lenalidomide in R/R NHL.

Methods

We conducted a phase I, open-label trial involving patients 18 years and older with R/R CD19+ NHL who have received at least two prior chemotherapeutic or biologic regimens and were not eligible for standard curative options at time of enrollment. Previous CD19-targeted therapy was allowed. Study consisted of a dose escalation followed by a dose expansion phase once the maximum tolerated dose (MTD)/ recommended phase II dose (RP2D) was established using a Phase I Queue modified 3+3 design. The escalation phase has been completed and consisted of blinatumomab continuous infusion (level 1 and 2: 9 mcg/day to 112 mcg/day) from days 1-56 and lenalidomide (level 1: 10 mg and level 2: 20 mg daily) days 29-49 of a 56-day induction cycle. Patients who responded underwent consolidation with blinatumomab continuous infusion days 1-7 and lenalidomide days 1-21 of a 28-day cycle for a maximum of 6 cycles followed by lenalidomide maintenance for 2 years or until unacceptable toxicity or disease progression. Dose limiting toxicities (DLT) included any grade 3/4 drug related adverse events (AE) observed during and up to 7 days after blinatumomab/lenalidomide simultaneous administration. Additional patients were accrued to replace patients who had grade 3/4 AE or progressed before receiving lenalidomide for dose-finding purposes. Primary endpoints included toxicity and determination of the MTD/RP2D during the first 8 weeks of blinatumomab/ lenalidomide induction. Secondary endpoints included overall response rate (ORR), complete response (CR) rate, progression free survival (PFS) which was censored at time of transplant and immune response biomarkers.

Results

As of July 17, 2019, 18 patients initiated therapy; 7 with diffuse large B cell lymphoma, 3 with mantle cell lymphoma, 3 with follicular lymphoma, 2 with nonspecified B cell lymphoma and 1 each with marginal zone lymphoma, Burkitt's lymphoma and small lymphocytic lymphoma. Median age was 58 (range 30-84) years and the median number of prior regimens was 2.5 (range 2-5); 5 patients had previous stem cell transplant (SCT). 6 patients had disease progression prior to starting lenalidomide. 3 patients received blinatumomab/lenalidomide at dose level 1 with no DLT noted. 9 patients received blinatumomab/lenalidomide at dose level 2 with 4 requiring blinatumomab dose reduction prior to starting lenalidomide. Due to favorable safety profiles with the combination using the MTD/RP2D of lenalidomide 20 daily, upfront doublet therapy was initiated as part of the planned expansion phase. Most common grade 3/4 adverse events were lymphopenia (39%), hypophosphatemia (22%) and hyponatremia (11%). 1 patient (5.5%) experienced grade 3 neurotoxicity. No grade 3/4 cytokine release syndrome or treatment related deaths were seen. At time of data cutoff, three patients remain on active treatment. At a median follow-up time of 14.3 months, ORR was 56% for all patients and 83% (50% CR) for those who received blinatumomab/lenalidomide combination therapy. Median PFS was 3.8 months (95% CI, 1.1 to NR) for all patients and 8.3 months (95% CI, 2.2 to NR) for those who received blinatumomab/lenalidomide combination therapy. 3 patients who achieved response underwent allogeneic SCT and remained in remission for 14.2 to 22.3 months thereafter. Correlative studies are pending and will be reported at time of presentation.

Conclusions

The combination of blinatumomab and lenalidomide, given at the RP2D dose of 20 mg daily, is safe and well tolerated. This regimen demonstrates encouraging efficacy in this heavily pretreated patient population and is a promising alternative treatment option for R/R NHL patients who are not candidates for aggressive cytotoxic chemotherapy or as a bridge to allogeneic SCT.

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