Synaptys Neuroscience: preventing Alzheimer’s disease with combination therapy

Sébastien Lasnier, a former pharmaceutical industry professional who switched to entrepreneurship some fifteen years ago, founded the start-up Synaptys Neuroscience in February 2024. The company is developing a drug candidate capable of slowing the progression of Alzheimer’s disease. “We are tackling this condition using a combinatorial approach. We are combining two highly synergistic molecules within a single treatment. This type of therapy exists in several fields, either in combination or in association: for HIV infection with triple therapy, in oncology with dual therapy, whereas for Alzheimer’s disease there is nothing. This has been my conviction for fifteen years, and today it has become the gold standard in Alzheimer’s disease research. With the help of AI, this field is set to accelerate. It is for these reasons that this combinatorial approach – particularly in the case of a multifactorial disease – seemed obvious to me,” explains the start-up’s founder.

To this end, Synaptys Neuroscience uses two molecules. A meta-analysis carried out by the AP-HP on 24,000 patients showed that the first molecule reduces mortality among patients with dementia. A second study conducted by Harvard University on 1,000 patients highlighted that the second molecule acts on at least two of the processes involved in cellular ageing. “It’s not just a simple combination of molecules; there’s a genuine synergistic effect, and that’s what we were looking for. We have global exclusivity to use the two in combination to treat Alzheimer’s disease,” adds the founder. The start-up succeeded in demonstrating positive results in vitro in a study carried out in 2022: according to Sébastien Lasnier, “42 per cent of neurons were saved”, whereas the molecules on their own would preserve only 2 per cent to 8 per cent of neurons.

A complex formulation

Formulating these two molecules took time because one is hydrophobic and the other hydrophilic. One of them acts as an anti-glutamate agent, glutamate being the main excitatory neurotransmitter in the central nervous system. This amino acid is involved in the transmission of nerve impulses and information between neurons. This is the system that malfunctions in Alzheimer’s disease.

One of the two molecules used by Synaptys Neuroscience is vitamin D, which primarily influences the calcium cycle. The other, memantine, acts on NMDA receptors, which are activated by glutamate and are essential for memory and synaptic plasticity. “NMDA allows calcium to pass through, which transmits the message to the neurons. Our molecule, just like vitamin D, acts on the synapse and the quality of calcium, particularly as it has anti-inflammatory effects. A recent study has also shown that it may have an impact on the clearance of amyloid plaques, which are involved in the development of Alzheimer’s disease,” explains Sébastien Lasnier.

To develop their drug candidate, the start-up went through four stages. The first was to identify the right molecules, which took two years. Next came targeting: they had to identify the correct receptor and, once this was done, the precise target or the right site to target on that receptor. Because, as Sébastien Lasnier points out, “if we hit just above our target, our substance could have hallucinogenic effects”.

During the third phase, the researchers focused on chronopharmacology – that is, the timing of when the active ingredient should be delivered into the body. Finally, the optimal doses had to be determined; these are in the nanomolar (nM) range. This is a complex issue, as the receptors become blocked if they are overstimulated. “We had a fairly narrow window for the whole system to work. These four elements are inseparable and patented. We have spent five years working on these issues,” says the founder. Several patents have already been filed and a proof of concept has been demonstrated.

Tackling the disease at an early stage

Three stages are envisaged for treating the disease: managing symptoms, slowing cognitive decline and a cure. Unfortunately, to date, no treatment has shown satisfactory results in the curative stage, as rebuilding destroyed neurons remains, for the time being, unachievable. Symptomatic treatments do exist, but are rarely prescribed as they have no effect on the progression of the disease. “Biogen and E. Lilly have brought out monoclonal antibodies that appear to have an initial effect on cognitive decline, but they cost 100,000 euros a year. Moreover, only patients with a specific genotype can benefit from them,” explains Sébastien Lasnier.

Diagnoses used to be made via lumbar puncture, but since 2025 it has been possible to be screened by a simple blood test. However, in the absence of a suitable preventive treatment, these tests serve no purpose. On the other hand, if Synaptys Neuroscience’s drug were to be developed, it would be a game-changer. “With our treatment, we could save almost one in two neurons. Taken over 20 years, it delays the onset of symptoms, which occur twice as late. This is a crucial issue. Our drug can truly change patients’ lives,” adds Sébastien Lasnier.

This is even more important given that this condition is very costly for the healthcare system: 3,400 euros per person, according to the founder. A drug, available in drop or tablet form, such as the one developed by the start-up, priced between 200 and 500 euros, would significantly reduce costs.

A market launch in 2030

The start-up’s six partners are based on the Saclay campus to “benefit from the powerful ecosystem comprising SATT Paris-Saclay, public incubators, and internationally renowned public and private research laboratories”, says Sébastien Lasnier. From the very beginning, Synaptys Neuroscience has been supported by IncubAlliance Paris-Saclay, the public incubator run by the Ministry of Higher Education, Research and Space, and Genopole. The start-up received its first grants from Bpifrance in 2024. Its first round of fundraising was finalised in February 2026, raising 500,000 euros from business angels. “We’ll have the results of our in vivo study in October and will then be able to move on to our 2.6 million euro seed round. The clinical phase will begin in 2028 with a Series A funding round of 35 million euros. From 2030 onwards, we will be able to finalise initial discussions with pharmaceutical companies in order to carry out the final trials required and bring our medicine to market as quickly as possible,” explains Sébastien Lasnier. 
The start-up is also allocating one million euros to prepare the regulatory dossiers required to obtain approval from the European Medicines Agency (EMA) and the US Food and Drug Administration (FDA). It is also collaborating with Inserm, the CEA and Contract Research Organisations (CROs) to carry out its trials, as it does not have its own laboratory. In April 2026, it was named Alzheimer’s Drug Development Company of the Year 2026 by Global Health & Pharma (GHP).