MSB to dispute FDA finding in Type A meeting, page-589

In revisiting some announcements in 2018... I found something quite informative.

On the 22nd Feb 2018 MSB announced that they had met the primary endpoint for the phase 3 SR-aGVHD clinical trial. At that time they said this

”Based on interactions with the FDA, Mesoblast believes successful results from the completed phase 3 trial, together with Day 180 safety and quality of life parameters in these patients, may provide sufficient clinical evidence for filing for accelerated approval...”

This was reiterated in June 2018 when the 100 day survival data was strong and was to be presented at a conference.

Then on 20 Sep 2018, the 180 safety data was available and continued to show strong survival outcomes. At this point it appears management made a decision to go for full approval with priority review.

I can’t access the webcasts around that time, but that is when I recall Silviu being asked why they had not taken the accelerated approval pathway and he responded that they were very confident with full approval given the strength of the data in hand.

If someone has luck accessing that webcast, it would be good to have the accuracy of my recollection confirmed or clarified.

In any case, it appears the FDA and MSB has prior discussions on accelerated approval and the FDA may have even encouraged them to take that path... I say this because it sounds like the discussions were positive... but instead it appears management went for full approval instead.

This could partly explain the combative language/attitude the FDA conveyed in their briefing notes. Maybe a little annoyed MSB tried to overreach for full approval... when an accelerated pathway was available and they suggested MSB would be in a position to apply for such an expedited approval pathway.

This does alleviate some of my concern when it comes to the eligibility for accelerated approval, in that the data needs to be “adequate and well controlled” as well as the use of 28 ORR as surrogate data. It appears MSB already have guidance from the FDA on all of this.

What MSB have now is a successful phase 3 single arm trial, strong 180 day survival data... and a 9-1 ODAC vote. The ODAC vote probably puts it well beyond doubt that the data is considered “adequate and well controlled”.