CK1δ Inhibition and Riluzole in ALS: Synergy at Lower Doses

Despite advances in understanding its biology, amyotrophic lateral sclerosis (ALS) has few approved treatment options. Riluzole, approved three decades ago, modestly extends survival—typically by a few months. Yet most patients develop progressive disability driven by TDP-43 proteinopathy, present in more than 95% of sporadic and familial ALS cases. In Neuropharmacology, investigators examined whether targeting casein kinase 1δ (CK1δ), a kinase implicated in TDP-43 phosphorylation, could enhance disease modification—alone or in combination with riluzole.

Their candidate, IGS2.7, is a brain-penetrant benzothiazole derivative designed to reduce TDP-43 hyperphosphorylation. The study integrates patient-derived lymphoblastoid cell lines and a TDP-43(A315T) transgenic mouse model, allowing parallel assessment of molecular, histologic, and behavioral endpoints.

Elevated CK1δ Activity in Patient-Derived Cells

Lymphoblasts from sporadic ALS patients exhibit significantly higher CK1δ mRNA, protein expression, and kinase activity compared with controls. The increase in enzymatic activity, measured by a luminescent kinase assay, supports CK1δ as a biologically relevant target.

With 24 hours of treatment, IGS2.7 reduced TDP-43 phosphorylation and restored nuclear localization. Riluzole alone, at 1 μM, had minimal impact. And combination of the two therapies further suppressed hyperphosphorylation.

STMN2, a TDP-43–regulated transcript typically reduced in ALS, also increased most robustly under combination treatment. Finally, dual therapy also produced the greatest reduction in protein aggregation. These results in patient-derived cells suggest pharmacologic synergy with the two treatments.

In Vivo: Additive at Full Dose, Synergistic at Low Dose

The translational test came in TDP-43(A315T) mice. At previously validated “effective” doses, IGS2.7 (1 mg/kg/day) and riluzole (10 mg/kg/day) each preserved motor neurons and reduced gliosis. Co-administration did not improve outcomes beyond IGS2.7 alone, but also did not introduce adverse effects.

The more provocative findings emerged at subeffective doses. In the second experiment, neither low-dose IGS2.7 nor low-dose riluzole alone prevented motor neuron loss. However, the combination of the two significantly preserved spinal motor neuron viability compared with untreated transgenic mice (p < 0.001).

Behavioral improvements on rotarod were modest and did not reach statistical significance, underscoring the persistent challenge of translating histologic protection into functional recovery. Still, the emergence of synergy only at lower doses raises an important pharmacodynamic question: might partial modulation of these complementary pathways outperform maximal inhibition of either alone?

MicroRNAs as Mechanistic Readouts

The authors further profiled inflammation-associated microRNAs. miR-124-3p, miR-221-3p, and miR-3065-5p were significantly upregulated in symptomatic TDP-43 mice. Combination therapy most effectively normalized miR-124 and uniquely restored miR-221 to near control levels.

Gene ontology analysis links these miRNAs to inflammatory pathways, protein kinase activity, and neuron-glia signaling. The coordinated modulation of miRNAs alongside motor neuron preservation suggests a systems-level effect beyond TDP-43 phosphorylation alone.

Limitations and Translational Context

Several caveats should indicate cautious interpretation. The mouse model captures key aspects of TDP-43 pathology but does not fully replicate human ALS heterogeneity. Behavioral benefits were limited, and treatment windows were short. Riluzole’s variable preclinical performance also complicates interpretation of interaction effects.

Moreover, lymphoblastoid cell lines, while useful for screening, are peripheral surrogates. Whether CK1δ inhibition in human motor neurons produces comparable molecular correction remains to be determined.

Clinical Implications

The study supports further exploration of CK1δ Inhibition as a therapeutic pathway in ALS. IGS2.7 may function as a stand-alone therapy targeting TDP-43 phosphorylation. But perhaps more intriguingly, lower-dose co-administration with riluzole may achieve synergistic benefit while limiting dose-related toxicity.

For a disease in which incremental survival gains are meaningful, combination therapy resulting in synergistic effects merits further exploration. The next step will be determining whether CK1δ inhibition translates from molecular correction in preclinical models to clinically meaningful outcomes in patients with ALS.

Reference:

Gomez-Almeria M, Martinez-Gonzalez L, Matos AT, et al. Assessment of the therapeutic effect of IGS2.7, a CK1δ protein kinase inhibitor, in combination with riluzole for the treatment of ALS-associated TDP-43 proteinopathy. Neuropharmacology. 2026;285:110804. doi:10.1016/j.neuropharm.2025.110804