Antisense oligonucleotide-based therapy in human erythropoietic protoporphyria

Area of Science:

• Genetics and Molecular Biology
• Hematology
• Genetic Medicine

Background:

• Erythropoietic protoporphyria (EPP) is a genetic disorder affecting red blood cells, characterized by light sensitivity and abdominal pain.
• In 90% of EPP cases, the condition stems from a common hypomorphic FECH allele and a deleterious mutation, leading to reduced ferrochelatase enzyme activity below 35%.
• This enzyme deficiency causes the accumulation of protoporphyrin IX (PPIX) in red blood cells, contributing to disease symptoms.

Purpose of the Study:

• To identify a therapeutic strategy targeting the common splicing defect in the FECH gene responsible for EPP.
• To develop and test an antisense oligonucleotide (ASO) capable of correcting the aberrant splicing event.
• To evaluate the efficacy of the ASO in restoring functional FECH mRNA and reducing PPIX levels in EPP models.

Main Methods:

• Utilized a candidate-sequence approach and antisense oligonucleotide (ASO)-tiling to identify a specific sequence for therapeutic targeting.
• Designed and tested an antisense oligonucleotide (ASO-V1) to block a cryptic splice site in intron 3 of the FECH gene.
• Assessed ASO-V1's impact on splicing, FECH mRNA levels, and PPIX accumulation in lymphoblastoid cell lines and primary erythroblasts from EPP patients.

Main Results:

• ASO-V1 successfully prevented the usage of the cryptic splice site, redirecting splicing to the physiological acceptor site.
• Transfection with ASO-V1 significantly increased the abundance of functional FECH mRNA in EPP-derived cell lines.
• In vivo administration of ASO-V1 to erythroblasts from an EPP patient markedly boosted WT FECH mRNA production and reduced PPIX accumulation to levels seen in asymptomatic individuals.

Conclusions:

• EPP represents a Mendelian disease where a common splicing defect can be corrected therapeutically.
• ASO-V1 demonstrates potential as a targeted therapy for EPP by restoring FECH enzyme function.
• This study highlights the feasibility of in vivo correction of splicing defects for treating genetic disorders like EPP.