ONESTX-01, a potent inhibitor of Steroid Sulphatase (STS), that restores neuron cholinergic activity and decreases cognitive impairment: design of a phase IIa clinical study

Abstract

Background: ONESTX-01 (Irosustat/STX64) is a small molecule that inhibits steroid sulfatase (STS), which showed a good safety and tolerability profile in patients with cancer in Phase I-II clinical trials. ONESTX-01 activity produced an increase in sulfated steroids. Some of them are called neurosteroids for its role in Central Nervous System (CNS). The administration of ONESTX-01 increased the ratio of sulfated/free steroids which expanded the lifespan of C. elegans, decreased the b-amyloid accumulation and recovered memory in Alzheimer Disease’s (AD) models (mice) (1). The drug appeared to act on the biology of aging. According to this idea, old mice showing cognitive impairment, treated up to 6 months with ONESTX-01, showed histological and molecular changes compatible with neuroprotection mechanism, such as increase of microglial response, decrease of inflammation markers, and improvement in cognition. We investigated whether the activity of ONESTX-01 on the cholinergic neuron was involved in the dependent cognition restoration in aged or in the Alzheimer’s models. Methods: On the one side, we have studied the cholinergic response in C. elegans using aldicarb, an acetylcholinesterase inhibitor, which generate a time-dependent paralysis due to the excess of acetylcholine. Then paralysis time depend on the amount of acetylcholine. On the other hand, to investigate the cholinergic activity in a mammal model, we tested the anti-amnesic effects of ONESTX-01 in a scopolamineinduced amnesia rat model. Animals were orally treated with ONESTX-01 (1 and 4mg/Kg) for 16 consecutive days before receiving scopolamine administration. Results: In C elegans, the simultaneous treatment with ONESTX-01 and aldicarb produced an earlier paralysis than aldicarb treatment alone, indicating a synergic cholinergic response. In the rat model of amnesia induced by acetylcholine deficiency, chronic oral administration of ONESTX-01 was effective in the prevention of memory impairments induced by acute administration of scopolamine, similarly to donepezil treatment. Our results suggest that the mechanism of action is due to changes in neuron functions and/or neuroprotection. Conclusion: ONESTX-01 oral treatment reduced symptoms in neurodegenerative diseases and decreased the cognitive impairment associated to aging in different “in vivo” models. Histological, genetic, pharmacological, and behavioural analysis pointed out that ONESTX-01 treatment increased cholinergic activity in different animal models, which may underlie the observed beneficial effect on neurodegeneration. A Phase IIa clinical trial, double-blind, multicenter, randomized, parallel group, placebo-controlled to assess the safety, tolerability and clinical benefitof treatment with ONESTX-01 in subjects mild to moderate AD that have abandonedanti-acetylcholinesterase treatments is being planned.