ACE-031 vs Mod GRF 1-29

Soluble decoy receptor for ActRIIB; sequesters myostatin, activin, and GDF-11 to remove multiple brakes on muscle and bone growth simultaneously

ACE-031 is a soluble decoy receptor fusion protein consisting of the extracellular domain of activin type IIA receptor (ActRIIA) linked to a human IgG1 Fc region, developed by Acceleron Pharma to bind and sequester myostatin, activin, and related TGF-beta superfamily ligands that negatively regulate muscle mass, with the goal of promoting muscle growth in severe wasting conditions including Duchenne muscular dystrophy. By competitively binding circulating myostatin and related ligands, ACE-031 reduces signaling through the Smad2/3 pathway that suppresses muscle satellite cell activation and protein synthesis; in preclinical models of myopathy, blockade of ActRIIA signaling produced significant increases in lean mass, supporting its evaluation in Phase 2 human trials. A Phase 2 randomized placebo-controlled trial in ambulatory boys with Duchenne muscular dystrophy demonstrated significant increases in lean body mass; however, the trial was halted early due to vascular-related adverse events including epistaxis and telangiectasias, attributed to off-target inhibition of angiogenic TGF-beta family ligands, and the Acceleron clinical program was subsequently discontinued. ACE-031 has no FDA approval and is not approved for any indication; commercial development was halted due to the adverse event signal identified in the clinical trial; it is not commercially available, and the vascular safety concern inherent to pan-ActRIIA ligand inhibition represents an unresolved risk that precludes its extrapolation to general performance or muscle enhancement applications.

Modified GHRH analog; binds GHRH receptors with improved stability to produce physiological GH pulses when combined with a GHRP

Mod-GRF 1-29 (also designated CJC-1293 without DAC, or tetrasubstituted GHRH[1-29]) is a synthetic analogue of the first 29 amino acids of growth hormone-releasing hormone, modified at four positions including substitution of norleucine at position 27 to improve proteolytic stability and extend the effective half-life of native GHRH 1-29, thereby producing more sustained pituitary GH stimulation per dose. Like endogenous GHRH, it acts through GHRH receptors on pituitary somatotrophs to stimulate cAMP-mediated GH synthesis and secretion, and is administered to mimic the hypothalamic pulse signal that drives GH release and downstream IGF-1 axis activity. Modified GHRH 1-29 analogues sharing the core amino acid substitutions of Mod-GRF 1-29, specifically [Nle27]GHRH(1-29)-NH2, have been administered to humans in controlled studies that documented sustained GH and IGF-1 axis effects with endocrine, metabolic, and immune endpoints characterized in age-advanced subjects. Mod-GRF 1-29 has not received FDA approval; the related compound sermorelin (unmodified GHRH 1-29) was previously FDA-approved for pediatric GH deficiency but was withdrawn by its manufacturer, and Mod-GRF 1-29 is an investigational compound not approved for any clinical indication. Naming note — Mod GRF 1-29 vs CJC-1295: the research compound marketplace uses several overlapping names for this compound. "Mod GRF 1-29" and "CJC-1295 without DAC" refer to the same tetrasubstituted GHRH(1-29) peptide. "CJC-1295 with DAC" (or simply "CJC-1295" in most clinical protocol contexts) is a different compound — it includes a Drug Affinity Complex (DAC) linker that enables albumin binding and produces a dramatically extended half-life (~8 days vs ~30 minutes for Mod GRF 1-29). CJC-1295 with DAC is used as an infrequent injection (weekly or biweekly) while Mod GRF 1-29 / CJC-1295 without DAC is used at each injection session, typically immediately before or alongside a GHRP such as ipamorelin to maximally leverage the GH pulse window. Dosage in research protocols: Mod GRF 1-29 is typically used at 100 mcg per injection alongside ipamorelin or another GHRP, administered 2–3 times daily or immediately before sleep to align with natural GH secretion peaks. Subcutaneous injection after reconstitution with bacteriostatic water is the standard route. Provider availability for Mod GRF 1-29 and CJC-1295 compounds is listed in the PeptideBase directory.