FDA Grants Fast-Track Designation to First Bioengineered Liver for Acute Liver Failure After Phase 1 Trial Shows Promise

Overview

The U.S. Food and Drug Administration has granted Regenerative Medicine Advanced Therapy (RMAT) designation to miroliverELAP, an investigational external liver assist product developed by Miromatrix Medical Inc., a wholly owned subsidiary of United Therapeutics Corporation. The designation, announced on April 8, 2026, follows positive results from a Phase 1 clinical trial and positions the bioengineered liver for an accelerated path through regulatory review.

MiroliverELAP is the first manufactured organ alternative to reach this regulatory milestone, representing a significant step forward for the field of organ bioengineering. The product is designed to provide temporary liver support to patients with acute liver failure (ALF) who currently face a 30 percent mortality rate when they are ineligible for transplant or cannot receive a donor organ in time.

What We Know

MiroliverELAP consists of an external blood circuit connected to a single-use bioengineered liver sustained outside the patient’s body. The bioengineered liver is manufactured by stripping a porcine liver of its cells through a process called decellularization, leaving behind the organ’s natural scaffold structure. That scaffold is then repopulated with allogeneic human endothelial cells and human hepatocytes isolated from donated human livers that were deemed unsuitable for transplantation, according to United Therapeutics.

The device functions as a bridge therapy: a patient’s blood is circulated through the external bioengineered liver, which performs critical metabolic functions while the patient’s own liver either recovers on its own or a transplant organ becomes available.

Phase 1 Trial Results

In January 2026, United Therapeutics reported positive results from a Phase 1 study in which five patients with acute forms of liver failure, acute-on-chronic liver failure, and severe acute alcoholic hepatitis were continuously treated with miroliverELAP for at least 44 hours each. None of the five patients were candidates for liver transplantation.

The single-arm, open-label safety study met its primary endpoint: all five patients survived during miroliverELAP treatment. Over a subsequent 32-day follow-up period, no unexpected serious adverse events attributable to the device were reported. Jeff Ross, president of Miromatrix, said the study “provides early evidence that miroliverELAP has the potential to provide liver support for patients experiencing ALF.”

The first patient in the trial was treated in June 2025 at Intermountain Medical Center in Murray, Utah, marking the first time a manufactured organ alternative was used in a human clinical trial. The Phase 1 study enrolled patients across multiple clinical sites, with 5 to 15 patients planned for the total study.

What RMAT Designation Means

The RMAT program, created under the 21st Century Cures Act, is specifically designed to accelerate development and review of regenerative medicine therapies targeting serious or life-threatening diseases with unmet medical needs. The designation grants miroliverELAP several regulatory advantages, including intensive FDA guidance on study design, eligibility for priority review, and rolling review of Biologics License Application materials.

What We Don’t Know

United Therapeutics has not yet disclosed full clinical data from the Phase 1 trial, including detailed biomarker changes, liver function measurements, or individual patient outcomes. The company has stated that complete study results will be published in the second half of 2026.

It remains unclear how long the bioengineered liver can sustain metabolic function during treatment, what the optimal treatment duration is, or how the therapy compares to existing liver support approaches such as dialysis-based systems. The Phase 1 trial was designed purely as a safety study with no control group, making it impossible to draw conclusions about efficacy at this stage.

The manufacturing scalability of the approach also presents open questions. Each miroliverELAP unit requires both a suitable porcine liver scaffold and human hepatocytes from donated livers that were not viable for transplantation, raising potential supply chain considerations as the therapy moves toward broader clinical testing.

Analysis

Acute liver failure affects thousands of patients annually, and current treatment options are limited. Approximately 45 percent of ALF patients recover spontaneously, 25 percent receive liver transplants, and 30 percent die because they are either ineligible for transplant or cannot receive a donor organ in time due to organ shortage and the rapid onset of the disease, according to United Therapeutics.

MiroliverELAP’s approach differs fundamentally from previous liver assist devices, which have generally relied on artificial filtration or individual cell-based bioreactors. By using an intact organ scaffold repopulated with functional human cells, the device aims to replicate the full range of liver metabolic activity rather than just filtration.

The RMAT designation adds miroliverELAP to a growing list of organ bioengineering programs receiving regulatory recognition. As previously reported, the broader field of organ manufacturing is advancing on multiple fronts, including xenotransplantation with gene-edited pig organs and ARPA-H-funded bioprinting efforts. MiroliverELAP occupies a distinct niche: rather than replacing organs entirely, it provides temporary external support using a bioengineered organ that functions outside the body.

Martine Rothblatt, CEO of United Therapeutics, described the Phase 1 results as “groundbreaking,” and the company has indicated it will initiate a Phase 2 study. United Therapeutics is also developing mirokidney, which uses the same decellularized scaffold technology for kidney applications, suggesting the platform could extend beyond liver support if clinical development continues to progress.