Orphanet Journal of Rare Diseases | Liver Transplantation and Gene Therapy in Inherited Metabolic Diseases: Health Policy Considerations

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This study provides a critical health policy perspective for treatment decision-making in inherited metabolic diseases, emphasizing the continued clinical value of liver transplantation and the importance of equitable resource allocation in the era of gene therapy.

 

Literature Overview

The article titled 'Transplantation as disease modifying therapy in the era of gene therapy medicinal products – health policy considerations,' published in the Orphanet Journal of Rare Diseases, systematically explores the ongoing therapeutic value of liver transplantation (LTx) in inherited metabolic diseases (IMDs), such as urea cycle disorders (UCD), glycogen storage disease type 1a (GSD1a), methylmalonic acidemia (MMA), and propionic acidemia (PA), against the backdrop of rapid advancements in gene therapy medicinal products (GTMP). The article not only compares the efficacy and safety of the two treatment modalities but also deeply analyzes their real-world accessibility, cost-effectiveness, and impact on health policy formulation. The study highlights that despite the promising future of GTMP, LTx still holds significant advantages in terms of survival benefit, long-term data support, and cost control—especially among adult patients and should not be overlooked.

Background Knowledge

Inherited metabolic diseases (IMDs) are a group of rare disorders caused by single-gene mutations leading to dysfunctional metabolic pathways. Diseases such as UCD, GSD1a, MMA, and PA often result in severe metabolic decompensation, neurodevelopmental impairments, and multi-organ damage. Liver transplantation as a disease-modifying therapy has been proven to significantly improve patient survival and quality of life, nearly achieving a 'cure' in UCD. However, with the emergence of gene therapies (GTMP), particularly those based on AAV vectors and mRNA-LNP platforms, patients and clinicians may be inclined to delay LTx in anticipation of safer, non-surgical therapies. Yet GTMP faces numerous bottlenecks: pre-existing immunity to AAV, vector-related hepatotoxicity, unknown long-term safety, and accessibility issues due to exorbitant costs. Additionally, most GTMP clinical trials focus on children, leaving adult data scarce and creating age-related bias in treatment decisions. This article's central argument lies in a systematic comparison of LTx and GTMP from a health policy perspective, emphasizing that under limited resources, treatment choices must be based on hard endpoint data, cost-effectiveness, and principles of fairness, rather than solely on patient preference or theoretical advantages.

 

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Research Methods and Core Experiments

The authors conducted a systematic review of published clinical data to compare liver transplantation and gene therapy in UCD, GSD1a, MMA, and PA regarding efficacy, safety, data quality, and health policy impact. The study included multiple single-center cohort studies, meta-analyses, and large transplant registry data (e.g., UNOS, ELTR), alongside publicly available results from ongoing GTMP clinical trials (e.g., NCT05345171, NCT05139316) for comparative analysis. Key evidence shows that LTx achieves nearly 90% 5-year survival in UCD patients and significantly reduces hyperammonemia episodes; in GSD1a, it eliminates hypoglycemia and improves quality of life; in MMA and PA, it reduces metabolic decompensation frequency and hospitalization rates. In contrast, GTMPs such as DTX301 (AAV for OTCD) and mRNA-3927 (LNP-mRNA for PA) show metabolic improvement but lack long-term survival data and carry safety risks such as hepatotoxicity and immune responses. The study also used cost-utility models (e.g., QALY) to compare the economic burden of both treatments, finding LTx more cost-effective in most cases.

Key Conclusions and Perspectives

• Liver transplantation can achieve disease cure or significant phenotypic improvement in UCD and GSD1a, whereas gene therapy currently offers only partial disease modification and has not reached equivalent efficacy levels.
• The long-term safety of gene therapy (e.g., risk of AAV-mediated hepatocellular carcinoma) remains unclear, especially in GSD1a and UCD patients with pre-existing liver damage, requiring cautious evaluation.
• Although liver transplantation is limited by donor organ shortages, the exorbitant cost of gene therapy (e.g., over $1 million per treatment) results in even poorer accessibility, particularly in low- and middle-income countries.
• Current gene therapy clinical trials primarily focus on children, lacking adult data, potentially skewing reimbursement policies toward younger populations and exacerbating treatment inequity.
• In health technology assessments, liver transplantation—not just standard drug therapy—should be used as the comparator for gene therapy to more accurately reflect clinical decision-making contexts.

Research Implications and Outlook

The study delivers an important warning to the drug development field: even though GTMPs have the theoretical potential for 'one-time cure,' their clinical translation must confront real-world challenges of long-term follow-up, safety monitoring, and cost control. For clinical surveillance, the study emphasizes the need to establish long-term registries for GTMP patients, particularly to monitor AAV vector-related liver tumor risks. In disease modeling, animal models should more accurately simulate the chronic progression and organ damage of human IMDs to better predict treatment outcomes. Additionally, the study calls on policymakers to require indirect comparison data with LTx during GTMP approval and to promote value-based pricing mechanisms, ensuring innovative therapies truly benefit patients rather than becoming economic burdens.

 

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Conclusion

From the perspective of translational research, this study emphasizes that in today’s rapidly advancing gene therapy landscape, liver transplantation should still be considered a cornerstone of the treatment framework for inherited metabolic diseases. Although gene therapy represents a future direction, its efficacy in UCD, GSD1a, MMA, and PA has not yet surpassed that of LTx, and it faces major challenges in safety, accessibility, and cost-effectiveness. Particularly in adult patients, LTx not only improves metabolic control but also manages complications such as hepatic adenomas and hepatocellular carcinoma—functions that GTMP cannot currently replace. Therefore, health policy must move beyond the 'innovation-first' mindset and return to a decision-making framework centered on patients, grounded in evidence, and aimed at resource sustainability. Future research should prioritize filling the adult data gap and promote the integration of multimodal treatment strategies, such as using GTMP as a bridge to LTx or for patients unable to access donor organs. Ultimately, only through fair, transparent, and multi-stakeholder policy dialogue can true progress in rare disease treatment be achieved.

 

Margreet Wagenmakers, Anna Lehman, Caroline den Hoed, Mirjam Langeveld, and Sandra Sirrs. Transplantation as disease modifying therapy in the era of gene therapy medicinal products – health policy considerations. Orphanet Journal of Rare Diseases.