Synergistic interaction between trazodone and gabapentin in rodent models of neuropathic pain

Neuropathic pain is a chronic debilitating condition caused by injury or disease of the nerves of the somatosensory system. Although several therapeutic approaches are recommended, none has emerged as an optimal treatment leaving a need for developing more effective therapies. Given the small number of approved drugs and their limited clinical efficacy, combining drugs with different mechanisms of action is frequently used to yield greater efficacy. We demonstrate that the combination of trazodone, a multifunctional drug for the treatment of major depressive disorders, and gabapentin, a GABA analogue approved for neuropathic pain relief, results in a synergistic antinociceptive effect in the mice writhing test. To explore the potential relevance of this finding in chronic neuropathic pain, pharmacodynamic interactions between low doses of trazodone (0.3 mg/kg) and gabapentin (3 mg/kg) were evaluated in the chronic constriction injury (CCI) rat model, measuring the effects of the two drugs both on evoked and spontaneous nociception and on general well being components. Two innate behaviors, burrowing and nest building, were used to assess these aspects. Besides exerting a significant antinociceptive effect on hyperalgesia and on spontaneous pain, combined inactive doses of trazodone and gabapentin restored in CCI rats innate behaviors that are strongly reduced or even abolished during persistent nociception, suggesting that the combination may have an impact also on pain components different from somatosensory perception. Our results support the development of a trazodone and gabapentin low doses combination product for optimal multimodal analgesia treatment.

Optimization of Indazole-Based GSK-3 Inhibitors with Mitigated hERG Issue and In Vivo Activity in a Mood Disorder Model

Bipolar disorders still represent a global unmet medical need and pose a requirement for novel effective treatments. In this respect, glycogen synthase kinase 3β (GSK-3β) aberrant activity has been linked to the pathophysiology of several disease conditions, including mood disorders. Therefore, the development of GSK-3β inhibitors with good in vivo efficacy and safety profile associated with high brain exposure is required. Accordingly, we have previously reported the selective indazole-based GSK-3 inhibitor 1, which showed excellent efficacy in a mouse model of mania. Despite the favorable preclinical profile, analog 1 suffered from activity at the hERG ion channel, which prevented its further progression. Herein, we describe our strategy to improve this off-target liability through modulation of physicochemical properties, such as lipophilicity and basicity. These efforts led to the potent inhibitor 14, which possessed reduced hERG affinity, promising in vitro ADME properties, and was very effective in a mood stabilizer in vivo model.

HnRNP A1 controls a splicing regulatory circuit promoting mesenchymal-to-epithelial transition

Epithelial-to-mesenchymal transition (EMT) is an embryonic program used by cancer cells to acquire invasive capabilities becoming metastatic. ΔRon, a constitutively active isoform of the Ron tyrosine kinase receptor, arises from skipping of Ron exon 11 and provided the first example of an alternative splicing variant causatively linked to the activation of tumor EMT. Splicing of exon 11 is controlled by two adjacent regulatory elements, a silencer and an enhancer of splicing located in exon 12. The alternative splicing factor and oncoprotein SRSF1 directly binds to the enhancer, induces the production of ΔRon and activates EMT leading to cell locomotion. Interestingly, we now find an important role for hnRNP A1 in controlling the activity of the Ron silencer. HnRNP A1 is able to antagonize the binding of SRSF1 and prevent exon skipping. Notably, hnRNP A1, by inhibiting the production of ΔRon, activates the reversal program, namely the mesenchymal-to-epithelial transition, which instead occurs at the final metastasis sites. Also, hnRNP A1 affects Ron splicing by regulating the expression level of hnRNP A2/B1, which similarly to SRSF1 can promote ΔRon production. These results shed light on how splicing regulation contributes to the tumor progression and provide potential targets to develop anticancer therapies.