Research on myostatin inhibitor ACE-031 stopped – but the stuff does work


Pharmaceutical companies Acceleron Pharma and Shire have put the myostatin inhibitor ACE-031 on hold. They made an announcement about this in a joint press release recently [acceleronpharma.com May 2, 2013]. A strange development, as a few weeks previously Muscle & Nerve published a study that shows that ACE-031 is stuff that anyone who considers themself to be a chemical bodybuilder would be happy to be able to afford.

Injectable ACE-031 – an underground example is shown above – is a synthetic activin receptor type IIB. Muscle cells have this receptor too: it’s intended for proteins like myostatin, GDF11 and activin A and B. If myostatin attaches itself to an activin receptor type IIB, then the growth of muscle fibres is inhibited. Under the ‘right’ conditions myostatin actually breaks down muscle.

If you inject ACE-031 this doesn’t happen at all. The synthetic activin receptor type IIB filters out the muscle inhibiting proteins and deactivates them.


In 2007 Acceleron Pharma still had high expectations for ACE-031. At that point the company only had animal studies to back them up. But in 2013 they published the results of a human study, in which 48 healthy women aged from 45-75 had been given a single injection containing 0.02, 0.05, 0.1, 0.3, 1 or 3 mg ACE-031 per kg bodyweight. The substance remained in circulation in the body for a number of weeks: the half-life was 10-15 days.



But the single injection did lead to muscle growth. The 3-mg/kg dose led to an increase in muscle of volume of 5 percent, it boosted lean body mass by 3 percent [just over a kilogram], and seemed to also reduce fat mass.


The injection reduced the leptin concentration and boosted that of adiponectin. This would suggest that ACE-031 breaks down fat mass.

Moreover, the myostatin inhibitor boosted the concentration of bone specific alkaline phosphatase [BSAP] in the blood and reduced that of C-terminal type 1 collagen telopeptide [CTX]. This would suggest that ACE-031 strengthens bones. Acceleron has demonstrated these effects in animal studies using RAP-031, the mouse variant of ACE-031. [Endocrinology. 2010 Sep; 151(9): 4289-300.]


If you read the article in Muscle & Nerve you wonder why Acceleron has put the development of ACE-031 on hold. And why it doesn’t declare war on the web-shop owners who happily ignore Acceleron’s patents and sell ACE-031 for prices that no ordinary pharmaceuticals company can compete with.

The answer is in a post on the website of the Muscular Dystrophy Association. [quest.mda.org May 2, 2013] This describes a trial [NCT01099761] performed in 2011 in which researchers gave ACE-031 to children with muscular dystrophy. During the trial side effects emerged and the researchers had to stop the study.

“The adverse events that the trial participants experienced — minor nose and gum bleeding and dilation of blood vessels in the skin — were not, in and of themselves, considered dangerous. However, the companies and regulatory agencies involved say they need to fully understand these events before continuing clinical studies of ACE-031.”

Some other strange side effects also came to light in the study published in Muscle & Nerve. ACE-031 caused the concentration of FSH in the women subjects to plummet. How this happened, and what the effects of this might be, the researchers don’t know.

Research on MYO-029, Wyeth’s myostatin blocker, is not going anywhere either. In 2008 disappointing results of a trial with MYO-029 were published, in which adults with muscular dystrophy gained no strength at all. [Ann Neurol. 2008 May; 63(5): 561-71.] After that Wyeth stopped developing MYO-029.

A single ascending-dose study of muscle regulator ACE-031 in healthy volunteers.

Attie KM, Borgstein NG, Yang Y, Condon CH, Wilson DM, Pearsall AE, Kumar R, Willins DA, Seehra JS, Sherman ML.


Department of Medical Research, Acceleron Pharma, Inc., 128 Sidney Street, Cambridge, Massachusetts 02139, USA.



ACE-031 is a soluble form of activin receptor type IIB (ActRIIB). ACE-031 promotes muscle growth by binding to myostatin and other negative regulators of muscle mass.


This double-blind, placebo-controlled study evaluated the safety, pharmacokinetics, and pharmacodynamics of ACE-031 in 48 healthy, postmenopausal women randomized to receive 1 dose of ACE-031 (0.02-3 mg/kg s.c.) or placebo (3:1).

ACE-031 was generally well-tolerated. Adverse events included injection site erythema. Mean ACE-031 AUC(0-∞) and C(max) increased linearly with dose; mean T(½) was 10-15 days. Statistically significant increases in mean total body lean mass (3.3%; P = 0.03, by DXA) and thigh muscle volume (5.1%; P = 0.03, by MRI) were observed at day 29 in the 3 mg/kg group. Statistically significant changes in serum biomarkers suggest ACE-031 also improved bone and fat metabolism.


Single-dose ACE-031 treatment was generally well-tolerated and resulted in increases in muscle mass in healthy postmenopausal women.

PMID: 23169607 [PubMed – indexed for MEDLINE]

Source: http://www.ncbi.nlm.nih.gov/pubmed/23169607

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