CRISPR Gene Editing Treatment Leads to Patient's Death 8 Days Later

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CRISPR Gene Editing Treatment Leads to Patient’s Death 8 Days Later

CRISPR Gene Editing Treatment Leads to Patient’s Death 8 Days Later, NEJM Publishes Autopsy Findings Revealing AAV-Induced Innate Immune Response as the Cause of Death.

The emergence and application of CRISPR gene editing technology have brought unprecedented hope to the treatment of genetic diseases.

In recent years, we have witnessed clinical advancements in CRISPR gene editing for rare genetic diseases, cancer, and cardiovascular disorders, igniting hope for many families facing rare and devastating conditions.

In October 2022, a 27-year-old Duchenne’s Muscular Dystrophy (DMD) patient named Terry Horgan tragically passed away after receiving CRISPR gene editing treatment delivered through a recombinant adeno-associated virus serotype 9 (rAAV9) vector.

On September 28, 2023, researchers from the Massachusetts Medical School and Yale University published a study in the New England Journal of Medicine (NEJM) titled “Death after High-Dose rAAV9 Gene Therapy in a Patient with Duchenne’s Muscular Dystrophy.”

Terry Horgan developed acute decompensated heart failure on the 6th day post-treatment, followed by sustained cardiac arrest, and succumbed to these complications 2 days later.

The research team conducted a thorough analysis of the cause of his death, and the autopsy findings revealed severe acute respiratory distress syndrome (ARDS) with diffuse alveolar damage.

Transgene expression in the liver was minimal, and there was no evidence of AAV9 antibodies or effector T-cell responses in the organs.

These results indicated that high-dose rAAV-induced innate immune responses led to ARDS in late-stage DMD patients receiving CRISPR gene editing therapy, marking the first reported case of patient death due to gene therapy-induced ARDS in the scientific community.

CRISPR Gene Editing Treatment Leads to Patient's Death 8 Days Later, NEJM Publishes Autopsy Findings Revealing AAV-Induced Innate Immune Response as the Cause of Death.

Duchenne’s Muscular Dystrophy (DMD)

Duchenne’s Muscular Dystrophy (DMD) is an X-linked recessive genetic disease, primarily affecting boys. It is estimated that approximately 1 in every 3500 male newborns worldwide is affected by this disease. Patients typically begin to manifest symptoms between the ages of 3 and 5, initially showing progressive leg muscle weakness, leading to impaired mobility. They typically lose the ability to walk by the age of 12, develop cardiac and respiratory weakness during adolescence, and experience severe complications that often lead to death between the ages of 20 and 30.

As a monogenic disease, DMD is caused by mutations in the Dystrophin gene located on the X chromosome. Due to these mutations, the Dystrophin gene fails to produce a sufficient or functionally intact dystrophin protein, resulting in the gradual replacement of muscle tissue with fat and fibrotic tissue in patients.

Customized CRISPR Gene Editing Therapy

The protagonist of this story, Terry Horgan, was diagnosed with DMD at the age of 5 and began daily treatment with Deflazacort, a corticosteroid that can alleviate muscle weakness and slow the progression of disability but cannot cure DMD.

In 2017, Terry’s brother, Richard Horgan, founded Cure Rare Disease, a nonprofit organization dedicated to helping rare disease patients like Terry.

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Terry (left) and his brother Richard (right)

In 2019, Richard collaborated with scientists from the University of Massachusetts and Yale University to develop a personalized CRISPR gene editing therapy for his brother, Terry.

In August 2022, the FDA approved the clinical trial application for this CRISPR gene editing therapy, known as CRD-TMH-001, for the treatment of Terry’s Duchenne’s Muscular Dystrophy (DMD). It was not only the first personalized CRISPR gene editing therapy but also the first CRISPR-based therapy for DMD to receive clinical approval.

The Dystrophin gene is exceptionally large, with as many as 79 exons, and mutations in different exons can lead to DMD. Due to its size, delivering the correctly encoded Dystrophin gene directly into cells is challenging.

For Terry, who had a deletion mutation in exon 1 of the Dystrophin gene, the CRD-TMH-001 therapy utilized a recombinant adeno-associated virus serotype 9 (rAAV9) to deliver a Cas9 variant (dSaCas9) with lost cleavage activity from Staphylococcus aureus and a transcription activation protein VP64.

This approach aimed to upregulate the expression of a shorter non-muscle full-length dystrophin isoform (Dp427c) to stabilize or reverse the progression of DMD.

CRISPR Gene Editing Treatment Leads to Patient's Death 8 Days Later, NEJM Publishes Autopsy Findings Revealing AAV-Induced Innate Immune Response as the Cause of Death.

Design of the CRD-TMH-001 Therapy

Clinical Trial Data

On October 4, 2022, Terry received the rAAV9-delivered CRISPR gene editing therapy via intravenous injection at a dose of 1x10E14 vg/kg.

Two days after the injection, he experienced premature ventricular contractions, followed by a declining platelet count.

On the third day, he was administered the first dose of Eculizumab, an anti-C5 antibody, to prevent complement-driven platelet reduction.

Meanwhile, B-type natriuretic peptide (BNP) and proBNP levels continued to rise, which are markers of cardiac function.

Aspartate aminotransferase and alanine aminotransferase increased proportionally to creatine kinase elevation, a common occurrence in DMD patients, while gamma-glutamyl transferase levels remained normal.

On the third and fourth days post-treatment, the patient developed asymptomatic hypercapnia and respiratory acidosis. On the fifth day, his cardiac function began to deteriorate, and on the sixth day, he developed acute respiratory distress syndrome (ARDS) and left ventricular ejection fraction (LVEF) reduction.

CRISPR Gene Editing Treatment Leads to Patient's Death 8 Days Later, NEJM Publishes Autopsy Findings Revealing AAV-Induced Innate Immune Response as the Cause of Death.

Clinical Research Data

During treatment, various interventions were attempted, including increasing corticosteroid dosage, administering Eculizumab (anti-C5 antibody), Tocilizumab (anti-IL-6R antibody), and Anakinra (IL-1R blocker). After suffering a cardiac and pulmonary arrest, the patient was placed on ECMO respiratory support.

Unfortunately, the patient passed away on the 8th day post-treatment due to multi-organ failure and severe hypoxic-ischemic neurological injury, resulting in coma and imaging changes in the brain.

Autopsy Findings Analysis

The autopsy revealed severe ARDS with diffuse alveolar damage in the patient. Transgene expression was minimal in the liver.

There was no evidence of AAV9 antibodies or effector T-cell responses.

These findings suggest that in older, late-stage DMD patients receiving high-dose rAAV-delivered gene therapy, a strong innate immune response induced by the high rAAV dose leads to ARDS.

Notably, the patient did not exhibit thrombotic microangiopathy or evidence of humoral or cell-mediated immune responses against the AAV capsid or delivered transgene products, unlike some other DMD patients who received similar or higher doses of rAAV9 vector-based gene therapy.

The patient had received a dose of 1x10E14 vg/kg, which was similar to testing doses in other clinical trials. However, he experienced a higher viral vector genome load, attributed to his lower lean muscle mass. The study also found that this patient experienced a more severe innate immune response compared to DMD patients who received similar or higher AAV doses in microdystrophin gene therapy clinical trials.

Based on these findings, the research team concluded that more data on factors that may predispose individuals to severe innate immune responses are needed when administering AAV gene therapy. Dose determination will remain a challenge for customized AAV gene therapy.

In summary, the 27-year-old late-stage DMD patient’s severe cardiopulmonary toxicity occurred on the 6th day after receiving intravenous injection of rAAV9-dSaCas9-VP64 therapy at a dose of 1x10E14 vg/kg. The research team suggested that the patient experienced a cytokine-mediated capillary leak syndrome, manifested by pericardial effusion on day 5 and ARDS on day 6, exacerbating pre-existing right ventricular heart failure. Unlike some DMD patients who received rAAV gene therapy, this patient did not exhibit thrombotic microangiopathy or evidence of humoral or cell-mediated immune responses against dSaCas9 or AAV9.

Although platelet reduction may indicate complement activation in this patient, the absence of complement deposition in the lungs and heart suggested that complement-mediated thrombotic microangiopathy was not the cause of death. ARDS is typically not associated with AAV gene therapy, and other DMD patients receiving similar doses of rAAV9 vector gene therapy did not experience this toxicity, indicating that host factors and inherent properties of the vector led to unexpectedly high levels of vector genome in the lungs, possibly contributing to this outcome.

Due to the rapid onset of acute toxicity in this patient after treatment, the safety and efficacy of the therapy could not be assessed. While trace amounts of the rAAV-delivered transgene product were found in his liver, none were detected in his heart or skeletal muscles. No evidence of effector T-cell responses against dSaCas9 or AAV9, or antibodies against AAV9, was observed. Another contributing factor may have been the patient’s low muscle mass (only 45%), resulting in a relatively high vector dose per muscle cell nucleus.

In 2021, a 16-year-old DMD patient died 6 days after receiving Pfizer’s AAV gene therapy fordadistrogene movaparvovec (dose of 2x10E14 vg/kg), which involved rAAV9 delivery of a “mini-dystrophin” and did not involve gene editing. Analysis suggested that the patient’s death was related to an innate immune response against the AAV viral capsid in the heart, leading to cardiogenic shock and heart failure.

In conclusion, this paper elucidates the cause of Terry Horgan’s death after receiving customized CRISPR gene editing therapy, which was an innate immune response to the high dose of rAAV. At 27 years old, he was already in the late stages of DMD, which may have limited his physiological reserves and ability to survive under the cardiopulmonary stress associated with acute toxicity from gene therapy.

Moving Forward in Tragedy

On October 14, 2022, following Terry Horgan’s untimely passing, Cure Rare Disease stated in an announcement: “It is with a heavy heart that Cure Rare Disease announces the passing of Terry Horgan, brother of Cure Rare Disease Founder and CEO Richard Horgan, who participated in a clinical trial of a novel CRISPR gene editing therapy, CRD-TMH-001. The cause of Terry’s passing is currently unknown. Terry’s loss is devastating, and he will be remembered as a medical pioneer, his courage and unwavering determination paved the way for increased attention, funding, and development of new therapies for rare diseases.”

CRISPR gene editing technology has only been in existence for a decade, and gene therapy for just over 20 years. Any death during clinical trials of CRISPR gene editing and gene therapy is an opportunity for reflection in these fields.

When a brave individual passes away, we must not only mourn but also learn as much as possible from the experience, identify the underlying issues, and swiftly address them to pave the way for progress.