Intrathecal delivery of frataxin mRNA encapsulated in lipid nanoparticles to dorsal root ganglia as a potential therapeutic for Friedreich’s ataxia

Abstract

In Friedreich’s ataxia (FRDA) patients, diminished frataxin (FXN) in sensory neurons is thought to yield the predominant pathology associated with disease. In this study, we demonstrate successful usage of RNA transcript therapy (RTT) as an exogenous human FXN supplementation strategy in vitro and in vivo, specifically to dorsal root ganglia (DRG). Initially, 293 T cells were transfected with codon optimized human FXN mRNA, which was translated to yield FXN protein. Importantly, FXN was rapidly processed into the mature functional form of FXN (mFXN). Next, FXN mRNA, in the form of lipid nanoparticles (LNPs), was administered intravenously in adult mice. Examination of liver homogenates demonstrated efficient FXN LNP uptake in hepatocytes and revealed that the mitochondrial maturation machinery had efficiently processed all FXN protein to mFXN in ~24 h in vivo. Remarkably, greater than 50% mFXN protein derived from LNPs was detected seven days after intravenous administration of FXN LNPs, suggesting that the half-life of mFXN in vivo exceeds one week. Moreover, when FXN LNPs were delivered by intrathecal administration, we detected recombinant human FXN protein in DRG. These observations provide the first demonstration that RTT can be used for the delivery of therapeutic mRNA to DRG.

mRNA as novel technology for passive immunotherapy

“…Thereafter, it took almost two decades until further studies started to demonstrate the broad potential of mRNA-based protein therapies. Meanwhile, there is a plethora of publications on a huge variety of indications comprising anemia [188,218], hemophilia [223,224], myocardial infarction [155,225], cancer [226,227], lung disease such as surfactant B deficiency and asthma [228][229][230], metabolic disorders [231][232][233][234][235], fibrosis [195], skeletal degeneration [236], tendon impairment [237], and neurological disorders such as sensory nerve dysfunction, Friedreich's ataxia and Alzheimer's disease [238][239][240]. Whereas evidence for the therapeutic potential of mRNA is mostly restricted to mouse models, first data in swine indicate that mRNA-based protein therapies are feasible also in large animals [218,225].…”

“…Only very few studies looking at local administration used uncomplexed and thus unprotected mRNA [225,228,230,237]. The majority of investigations built on lipid-based formulations with a clear tendency to the application of LNPs [223,224,[231][232][233]239]. Most if not all groups purified their IVT mRNA before in vivo administration.…”

Modified mRNA as a therapeutic tool to induce cardiac regeneration in ischemic heart disease

“…Following that pivotal work, the use of mRNA‐based gene replacement was demonstrated in other diseases using different genes: (1) Bcl‐2 modRNA was used to reduce hepatocytes apoptosis in a mouse model of fulminant hepatitis; (2) Intrathecal injection of mRNA, with optimized codon usage, encoding frataxin was used to treat Friedreich's ataxia in mice; (3) The use of modRNA encoding TLR1 TLR2 and TLR6 has been shown to improve lung function as well as reduced airway inflammation in a mouse model of asthma; (4) ModRNA encoding the transcription factor RUNEX1 was used to treat osteoarthritis in mice; (5) IGF‐1 modRNA was shown to reduce apoptosis in mice model of MI; (6) In 2015, Thess et al demonstrated efficient delivery and physiological effects of modRNA encoding for erythropoietin in large animals including pigs and non‐human primates …”

Sustained FXN expression in dorsal root ganglia from a nonreplicative genomic HSV‐1 vector

“…However, given the elevated number of host cells being genetically modified by vector genomes, these encouraging results now await careful studies of biodistribution and biotoxicity. In a more recent study, intravenous injection of FXN mRNA encapsulated in lipid nanoparticles was shown to increase liver frataxin levels in mice and some expression could be detected in DRG neurons if the nanoparticles were administered by intrathecal delivery . These promising observations open the possibility of using easily manufactured nanoparticles, although the requirement for repeated intrathecal injections as a result of their short persistence of therapeutic effect remains as an obstacle to be overcome before translation to the clinic.…”