ACE-083 is an experimental therapy being developed by Acceleron Pharma to treat muscle-wasting diseases — specifically, facioscapulohumeral muscular dystrophy (FSHD) and Charcot-Marie-Tooth disease (CMT). While CMT can cause muscle wasting, it is considered a nerve disorder rather than a form of muscular dystrophy.

How ACE-083 works

FSHD is a disease characterized by the progressive weakening of muscles, starting in the face, shoulders, and upper arms.

ACE-083 is designed to increase strength and function in specific muscles to improve function. The therapy contains a small molecule that binds to and inhibits select proteins in the TGF-beta protein superfamily, namely activins and myostatin, which reduce muscle growth.

Normally, muscle size is controlled by a balance of building and breaking down muscle. Exercising helps muscles to grow; if a person stops exercising, the muscles gradually reduce in size, due to the function of activins and myostatin, among other factors.

Inhibiting the TGF-beta family — sometimes called the “myostatin +” approach — means that muscle breakdown can be reduced or slowed. This approach is thought to increase muscle mass and strength where the treatment is administered. Untreated muscles or other organs are not affected, which reduces the potential of side effects.

ACE-083 in clinical trials

A Phase 1 clinical trial (NCT02257489) evaluated the safety and tolerability of single and multiple doses of ACE-083 administered as a local injection into selected skeletal muscles of healthy volunteers. The study also determined the amount of ACE-083 that reached systemic circulation following local administration, and whether local administration into a skeletal muscle can lead to an increase in muscle size and/or strength. The results of this trial were presented at the 14th International Congress on Neuromuscular Disease in 2016. They showed that local administration of ACE-083 into the rectus femoris muscle (one of the muscles of the upper leg) was well-tolerated and associated with dose-dependent increases in muscle volume.

Based on these results, Acceleron is conducting a Phase 2 clinical trial (NCT02927080) to evaluate the safety, tolerability, pharmacodynamics (effect on the body), efficacy, and pharmacokinetics (movement in the body) of ACE-083 in patients with FSHD. The trial is being conducted in two parts. Part 1 is open-label and dose-escalating, and part 2 is randomized, double-blind, and placebo-controlled. The trial is currently ongoing and is expected to conclude in 2020. Participants will be eligible to enroll in an open-label extension trial (NCT03943290) that will study the long-term effects of ACE-083 on patients with FSHD.

Other information

The U.S. Food and Drug Administration granted ACE-083 fast track and orphan drug designations for FSHD and CMT.

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