Tecfidera Modulates Activation of Malignant B-Cells: Correlative Analysis from a Phase 1 Clinical Trial in Patients with Chronic Lymphocytic Leukemia

Tecfidera (Dimethylfumarate, DMF) is an immunomodulatory drug currently approved in the United States for the treatment of patients with multiple sclerosis (MS). DMF formulations have also been utilized for the treatment of patients with psoriasis. The ability of DMF to Inhibit autoreactive T-lymphocytes may also be applicable to malignant T- and B- lymphocytes. Indeed, preclinical studies by multiple groups have highlighted its potential efficacy as a treatment for patients with various lymphoid cancers, though inhibition of STAT, NF-KB, Wnt signaling pathways, and glycolysis. This information provided rationale to conduct a phase 1 clinical trial of DMF as a treatment for patients with relapsed chronic lymphocytic leukemia (CLL). In this study we report the correlative assessment of the initial patients who received DMF.

Patients with relapsed or refractory CLL received DMF 120 mg PO BID (based on preclinical modeling with primary CLL cells in vitro and in vivo and 50% lower than the standard DMF dose for patients with MS). Treatment was planned for a short duration of 2 months to evaluate tolerability and effects on CLL cell signaling and tolerability of the drug by patients with CLL. Peripheral blood leukemic cell were isolated and analyzed by RNAseq and phosphoprotein immunoblotting at times just prior to, and 6 hours immediately following drug administration.

Consistent with preclinical results (Brennan et al, PLOS one 2015; Selman et al, Science Trans Med 2018), STAT1 phosphorylation at Y701 was decreased 6 hours following the initial dose, compared to high baseline levels. Differential expression analyses for RNAseq of total RNA isolated from peripheral blood CLL cells weere performed using limma models, which compared pretreatment versus post-treatment at a specific time point. Functional annotations of these genes revealed a significant enrichment related to B-cell activation, B-cell receptor (BCR) signaling, B-cell differentiation, and immune signaling generally. Specifically, several known CLL therapy targets including SYK, LYN, and BTK were significantly downregulated. Gene-set-enrichment analysis (GSEA) revealed that the "CLL-BCR gene signature" previously described by Herishanu et al. (Blood 2011) was consistently down-regulated after DMF treatment in samples from different time points (C1D1 post, C1D8 and C2D1) compared to pretreatment samples (FDR q of 0.24, 0.01 and 0.04, respectively).

In conclusion, this is the first report of the clinical use of DMF for patients with CLL in which inhibition of leukemic cell activation has been demonstrated. The inhibitory effect of DMF on leukemic cell gene expression, in particular its antagonism of BCR signaling, is valuable information for the development of novel combination strategies for CLL or other B-cell malignancies.