Sanofi SA (ADR) (SNY) just announced that it has struck a deal with privately held biotechnology company Principia Biopharma. The arrangement will see the two companies, spearheaded by the former, team up to try and develop and, in turn, bring to market, a multiple sclerosis (MS) asset that takes advantage of what is essentially a brand new mechanism of action in the space.

Here’s a look at the deal, the science behind the drug target and what all it means for Sanofi and the MS population going forward.

So, as mentioned, the collaboration is rooted in a drug that’s been developed by Principia – a drug called PRN2246. Chances are this is a new asset to most reading but many might already be familiar with the asset class – it’s part of a family of drugs called BTK inhibitors.

This sort of drug has a really interesting mechanism of action but it’s pretty complicated, so stick with us.

BTK is an abbreviation for what’s called a Bruton’s tyrosine kinase, which is an enzyme that in humans is encoded by the BTK gene. The role that these BTK enzymes play is rooted in the creation of B cells (of which there are many different types) and these B cells perform a variety of functions in the body, from immune system regulation to antibody secretion.

Sometimes, however, the BTK gene is mutated and this results in dysfunctional BTK that, in turn, results in overproduction of (or the production of dysfunctional) B cells. When you get too many B cells or B cells that don’t work, you get problems. MS in one such problem. Excessive B cell presence leads to the stripping of the myelin sheath (which is also referred to as demyelination) from nerves that comprise the central nervous system (CNS). The idea behind PRN2246, therefore is that it inhibits the BTK enzymes, translating to a reduction in the number of B cells produced by the body.

Fewer B cells should lead to a reduction in the degree of demyelination which, in turn, should lead to a halting of the progression of (or even, in the best case scenario, a reversal of the severity of) the MS in these patients.

We say should here because, right now, this is all preclinical. Well, that’s not entirely accurate. The ability of BTK inhibitors to improve certain diseases (mainly cancers) has been validated already. In MS, however, this is a new approach.

What are the terms of the collaboration?

Sanofi has paid $40 million up front to Principia and has earmarked a further $805 million for further payment based around development and commercialization milestones. The exact input we are likely to see from each isn’t immediately clear but there’s a good chance Sanofi is going to take the lead on the program, given the latter’s access to resources.

What does this mean for the space?

The potential of BTK inhibitors has long been discussed in the MS space but – until now – no company has really taken the lead in trying to underpin this potential with anything quantitative. With the latest news, Sanofi has finally opened the door to what could potentially prove a game changing treatment type for patients with this devastating disease.

What’s next?

The drug is at pre-IND phase right now, so we expect Sanofi and Principia to put together an IND for the FDA in the US and submit for approval. Once this is in place, the companies will initiate a phase I safety trial and, beyond that, try to demonstrate efficacy as part of a raft of mid stage studies.