Transmedics panel defies expectations

A scorchingly positive adcom was somewhat unexpected given the FDA’s scepticism in the briefing documents.

Policy and regulation

The uncharacteristically negative attitude the FDA took earlier this week, before yesterday’s panel meeting assessing Transmedics’ OCS Liver system, had spooked the group’s investors, who sent the company’s stock down 5% before the shares were halted yesterday. Now those who sold up are doubtless regretting their skittishness.

In the end the panel’s votes were so favourable Transmedics must have wondered what all the fuss was about. Only one panellist cast a negative vote, on only one of the three questions, and OCS Liver, designed to perfuse a donated liver with warm, oxygenated blood during the transplant procedure, is now odds-on for approval later this year. Transmedics’ shares are up 11% in early trade.

Transmedics’ filing for premarket approval of the Liver version of its Organ Care System rests on data from a trial called OCS Liver Protect. This met its primary effectiveness endpoint by showing a significant reduction in early allograft dysfunction, at 18% when the system was used versus 31% when the organs were kept on ice, the current standard of care.

The OCS Liver system also resulted in significantly higher use of livers from donors after cardiac death, at 51% versus 25% of those packed in ice. Protect’s safety endpoint was also met, with rates of graft-related serious adverse events with the device non-inferior to control. Patient survival at one year was 94% for both OCS Liver and control arms.

The FDA, controversially lenient when it comes to certain drug approvals, seemed not wholly convinced of Protect’s success. In the briefing documents the agency had called out several concerns with the Protect trial’s design and data, including the fact that, despite the improvement on early allograft dysfunction, no significant difference between subsequent mortality or graft loss rates were seen.

The briefing docs described these as “the ultimate and most relevant measures of transplant success”, and added that the reduction in EAD in the OCS arm was therefore of unclear significance.

Benefits

The panel seemed to take little notice. The votes on effectiveness and safety were both unanimously in favour of the system, and the panel voted 12 to one, with one abstention, that the benefits of the OCS Liver system outweighed its risks.

The main concern of the two panellists who did not vote in favour was that the data were insufficient to back this statement up clearly. 

Should the FDA side with the panel, approval for OCS Liver could come towards the end of this year. Before that, though, Transmedics could see approval for the heart version of the machine, OCS Heart, which was the subject of a more mixed, though still broadly positive, adcom in April, and on which a decision could arrive in the next month or so. 

Along with the version of the Organ Care System device designed to preserve donated lungs, approved in the US in 2018, Transmedics could soon find itself with three approved devices. It plans to start development work on a fourth, OCS Kidney, late this year or early next.

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