# Development and optimization of skeletal muscle delivery vehicles

> **NIH NIH R01** · CINCINNATI CHILDRENS HOSP MED CTR · 2024 · $525,048

## Abstract

Project Summary/Abstract
Correction of genetic muscle diseases, such as the muscular dystrophies, is a unique problem due to the
distribution of muscle throughout the body in inaccessible locations. Current clinical trials for Duchenne muscular
dystrophy, caused by mutations in the dystrophin gene, involve gene therapy strategies that utilize AAV
serotypes to deliver micro-Dystrophin (µDys). While AAV gene therapies are promising, use of lentiviruses that
have some desirable characteristics are not considered for skeletal muscle gene therapy. AAVs contain protein
capsids that mediate entry into cells, in contrast to lentiviruses that have a membrane envelope derived from
budding off from host cells. Enveloped viruses utilize membrane fusion to enter cells, which is mediated by
fusogenic proteins that form a complex between membranes to drive rearrangements needed for fusion. Skeletal
muscle development also requires membrane fusion events between progenitor cells to form multinucleated
myofibers. Myomaker and Myomerger are muscle-specific cell fusogens, but do not structurally or functionally
resemble classical viral fusogens. We tested if the muscle fusogens could functionally substitute for viral
fusogens, despite their structural distinctiveness, and fuse viruses to cells. We used a pseudotyping platform, a
general process where envelope proteins are altered to change the tropism of the virus, to engineer Myomaker
and Myomerger on the membrane of lentiviruses. We found that these muscle fusogenic lentiviruses leads to
specific transduction of skeletal muscle and that locally and systemically injected virions can deliver micro-
Dystrophin (µDys) to skeletal muscle of a mouse model of Duchenne muscular dystrophy and alleviate
pathology. In addition to lentiviruses, extracellular vesicles are another type of membrane vehicle being
considered for gene therapies. Extracellular vesicles are a heterogenous group of membrane particles released
from most cell types and can contain factors important for homing and entry. We have also uncovered a system
where Myomaker and Myomerger are present on extracellular vesicles and these vehicles exhibit delivery of
material to muscle cells. We will explore these novel membrane vehicles that harness the intrinsic properties of
myogenic membranes. Specifically, we propose to: 1) identify an optimal dosing strategy for lentiviruses
pseudotyped with Myomaker and Myomerger 2) characterize these novel lentiviruses and molecularly dissect
their fusion mechanism with muscle cells 3) develop extracellular vesicles engineered with Myomaker and
Myomerger that target skeletal muscle. Successful completion of these studies will provide unique insight into
these novel vectors specific for skeletal muscle, which have the potential to complement limitations of current
viral-based gene therapies.

## Key facts

- **NIH application ID:** 10975610
- **Project number:** 1R01AR083368-01A1
- **Recipient organization:** CINCINNATI CHILDRENS HOSP MED CTR
- **Principal Investigator:** Douglas Paul Millay
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $525,048
- **Award type:** 1
- **Project period:** 2024-07-08 → 2029-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10975610

## Citation

> US National Institutes of Health, RePORTER application 10975610, Development and optimization of skeletal muscle delivery vehicles (1R01AR083368-01A1). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10975610. Licensed CC0.

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