FLGR-242 (Follistatin-Derived Construct)
Get a source-linked, educational explanation from this profile.
Complete Research Guide
Open each section for the available evidence. Gaps are stated rather than inferred.
Overview
FLGR-242 (Follistatin-Derived Construct) is listed as engineered follistatin construct (investigational).
- •Muscle-growth (myostatin-pathway) research
- •Protein-engineering research
- •Sold by research suppliers for laboratory use
- •Discussed in muscle-wasting and aging-muscle research circles
Regulatory status: Not FDA-approved for any use and not in registered human clinical trials as of this review. Sold online as a "research chemical" — not for human use, not a dietary supplement, and not eligible for standard pharmacy compounding. Follistatin-pathway products are prohibited in sport under WADA's general rules on myostatin inhibitors and non-approved substances..
Structure & Properties
Compound: FLGR-242 (Follistatin-Derived Construct); also known as FLGR242, FLGR 242, Follistatin FLGR242, follistatin-derived albumin-binding construct.
Pharmacologic class: Engineered Follistatin Construct (investigational).
Known delivery routes: Subcutaneous (vendor-suggested only), No studied route.
Sequence, molecular weight, salt form, and excipient details are formulation-specific and are not listed unless verified by a manufacturer or laboratory COA.
How It Works
FLGR-242 is described by vendors as a modified form of follistatin — a natural protein that traps myostatin, the body's main brake on muscle growth — fused to an albumin-binding section intended to make it last longer in the blood. The underlying biology is well established: blocking myostatin increases muscle mass in animals and in rare human gene-therapy studies. However, no published study has tested FLGR-242 itself, so its exact makeup, how well it binds myostatin, and how long it actually lasts in the body are unverified vendor claims.
- •None established for FLGR-242 itself
- •Related science: follistatin gene therapy increased muscle mass and strength in monkeys
- •Related science: blocking myostatin produces large muscle gains in animals
- •Vendor claim of a long (multi-day) duration in the body — unverified
Human Research
Evidence grade: Pre-clinical / Observational
Evidence is primarily preclinical or observational; human effectiveness and long-term safety are not established.
- Schuelke M et al. Myostatin mutation associated with gross muscle hypertrophy in a child. N Engl J Med. 2004;350:2682-8.
- Lee SJ, McPherron AC. Regulation of myostatin activity and muscle growth. Proc Natl Acad Sci USA. 2001;98:9306-11.
- Amthor H et al. Follistatin complexes myostatin and antagonises myostatin-mediated inhibition of myogenesis. Dev Biol. 2004;270:19-30.
- Kota J et al. Follistatin gene delivery enhances muscle growth and strength in nonhuman primates. Sci Transl Med. 2009;1:6ra15.
- Haidet AM et al. Long-term enhancement of skeletal muscle mass and strength by single gene administration of myostatin inhibitors. Proc Natl Acad Sci USA. 2008;105:4318-22.
- Mendell JR et al. Follistatin gene therapy for Becker muscular dystrophy and sporadic inclusion body myositis (clinical trial program). Mol Ther. 2017;25:870-879.
- Sleep D et al. Non-covalent albumin-binding ligands for extending the circulating half-life of small biotherapeutics. Med Res Rev. 2019;39:715-762.
- World Anti-Doping Agency. The Prohibited List (myostatin inhibitors and non-approved substances prohibited in sport).
- U.S. FDA. Bulk drug substances used in compounding — follistatin products are not approved and not on the 503A bulks list.
Laboratory Research
No peer-reviewed publication studies FLGR-242 itself. The supporting science is indirect: follistatin gene therapy increased muscle mass and strength in monkeys, a human child with a myostatin mutation developed exceptional muscle, and albumin-binding is a proven general strategy for extending a protein's time in circulation. None of this confirms that the FLGR-242 product works or is safe.
Preclinical findings describe biological plausibility, not proven benefit in people. Animal and laboratory doses do not translate directly to human use.
Processing & Interactions
Timing and exposure
No studied schedule — FLGR-242 has never been given to people or animals in a published study.
Potential interactions and combinations to avoid
- •Competitive sport — myostatin inhibitors are prohibited
- •Active or suspected cancer
- •Unverified research-market products
Absorption, half-life, metabolism, and clearance can vary by formulation and route. Use prescribing information when an approved product exists.
Safety & Precautions
Known or reported risks
- •No human or animal safety data for this specific product
- •Identity, purity and sterility of research-market vials are unverified
- •Blocking myostatin long-term may affect tendons, heart muscle and reproductive hormones (pathway-level concerns)
- •Possible immune reaction to an engineered foreign protein
- •Prohibited in competitive sport
Contraindications
- •Active cancer or history of cancer (growth-signaling effects unknown)
- •Heart conditions (cardiac effects of myostatin blockade are not understood)
- •Pregnancy or breastfeeding
- •Under 18 years of age
- •Competitive athletes subject to anti-doping testing
- •History of any solid tumor or hematologic malignancy
- •Bleeding disorders, epistaxis, or anticoagulant/antiplatelet therapy (telangiectasia risk)
- •Cardiac hypertrophy, cardiomyopathy, or valvular disease
- •Pre-existing tendon or ligament pathology (strength gain outpaces connective-tissue adaptation)
- •Bleeding disorders or anticoagulant therapy without physician guidance (injection-site haematoma)
- •Active skin infection, cellulitis, or lipohypertrophy at intended injection sites
- •Inability to maintain sterile technique or safe sharps disposal
- •Not FDA-approved for human therapeutic use — no verified purity, sterility, or potency standards
- •Immunocompromised or transplant patients (unverified sterility and immunogenicity risk)
- •Concurrent participation in drug-tested sport (WADA prohibited or non-cleared substance)
- •Known hypersensitivity or prior reaction to this compound or any excipient/diluent
- •Pregnancy, attempting conception, or breastfeeding unless prescribed and monitored by a physician
- •Children and adolescents with open growth plates (unless under specialist endocrine care)
- •Active or recently treated malignancy without oncology clearance
- •Use without a confirmed diagnosis, baseline labs, and licensed clinical supervision
Unknown long-term toxicity should be assumed where controlled human data are limited. Seek urgent care for a severe or unexpected reaction.
Administration & Studied Formulations
Reference range: No established dose. No published animal or human study has dosed FLGR-242; vendor suggestions are not evidence-based.
Frequency: Not established
Cycling: No cycle exists — FLGR-242 has never been tested in a published study.
Subcutaneous (vendor-suggested only)
Not established — no published study exists.
Research only — no studied device or technique. No human or animal technique has been published.
Vendors claim a long duration in the body from albumin binding; this has not been independently verified.
Dosing information is educational context, not a personal recommendation. Approved products must follow their label and prescriber instructions.
Applications & Related Therapies
Potentially complementary measures
- •Progressive resistance training and adequate protein (the proven drivers of muscle)
- •Creatine and vitamin D (well-studied muscle support)
Clinical use should account for diagnosis, approved alternatives, nutrition, activity, sleep, rehabilitation, current medicines, and appropriate monitoring.
Educational only. All evidence is indirect — from follistatin and myostatin research, not from FLGR-242 itself.
Cases, Considerations & Ethics
Decision framework: establish the clinical goal, confirm evidence quality and legal status, screen contraindications and interactions, compare approved alternatives, define monitoring and stopping criteria, and use shared decision-making with a licensed clinician.
Case evidence: individual reports cannot establish safety or effectiveness and should not outweigh controlled trials.
Ethics: informed consent should distinguish established care from experimental use, disclose uncertainty and cost, avoid overstated claims, and never substitute research products for medically necessary care.
What is FLGR-242 (Follistatin-Derived Construct)?
In plain words
FLGR-242 is a lab-engineered version of follistatin, a natural protein that switches off myostatin — the body's built-in brake on muscle growth. Sellers claim a modification makes it last longer in the blood. The science behind blocking myostatin is real, but no published study has ever tested FLGR-242 itself, so whether the product works, how long it lasts, and whether it is safe are all unknown.
Technical definition
FLGR-242 is a vendor-designated, investigational protein construct described as a truncated recombinant follistatin variant fused via a glycine-serine linker to an albumin-binding domain, intended to neutralize myostatin (GDF-8) and extend circulating half-life. The parent biology is established: follistatin binds TGF-β superfamily ligands including myostatin and activin, and myostatin blockade increases skeletal muscle mass in animals and in AAV-follistatin primate studies. However, no peer-reviewed publication characterizes FLGR-242 itself — its sequence, binding selectivity, pharmacokinetics and safety are unverified vendor claims. It is not FDA-approved, not in registered human trials, and myostatin inhibitors are prohibited in sport by WADA.
Function
Dosing
Recommended Time of Day
Not established — no published study has dosed FLGR-242 at any time of day.
See “Timing & Interactions” below for full fasted/fed circumstances, what to avoid combining, and what pairs well.
Administration & Technique
Injection & Application Sites
- Abdomen — 2 in (5 cm) away from the navel, either side. Fastest, most consistent SubQ absorption.
- Flank / love handle — Lateral fat pad above the hip. Good rotation site when the abdomen is tender.
- Outer thigh — Upper outer quadrant, a hand-width below the hip. SubQ pinch at 45°.
Diagram is a general illustration, not a medical instruction. Rotate sites every injection, keep 1 in (2.5 cm) between recent sites, and avoid scars, moles, bruises and the navel area.
Cycling
No cycle exists — FLGR-242 has never been tested in a published study.
Timing & Interactions
- ·Competitive sport — myostatin inhibitors are prohibited
- ·Active or suspected cancer
- ·Unverified research-market products
- ·Progressive resistance training and adequate protein (the proven drivers of muscle)
- ·Creatine and vitamin D (well-studied muscle support)
Storage & Reconstitution
Reconstitution Calculator
1 mL = 100 units on a standard U-100 insulin syringe. Draw to the nearest 0.5 unit and confirm dosing with a clinician before injection.
Your Notes
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Benefits
- ·None established for FLGR-242 itself
- ·Related science: follistatin gene therapy increased muscle mass and strength in monkeys
- ·Related science: blocking myostatin produces large muscle gains in animals
- ·Vendor claim of a long (multi-day) duration in the body — unverified
Risks
- ·No human or animal safety data for this specific product
- ·Identity, purity and sterility of research-market vials are unverified
- ·Blocking myostatin long-term may affect tendons, heart muscle and reproductive hormones (pathway-level concerns)
- ·Possible immune reaction to an engineered foreign protein
- ·Prohibited in competitive sport
Contraindications
- ·Active cancer or history of cancer (growth-signaling effects unknown)
- ·Heart conditions (cardiac effects of myostatin blockade are not understood)
- ·Pregnancy or breastfeeding
- ·Under 18 years of age
- ·Competitive athletes subject to anti-doping testing
- ·History of any solid tumor or hematologic malignancy
- ·Bleeding disorders, epistaxis, or anticoagulant/antiplatelet therapy (telangiectasia risk)
- ·Cardiac hypertrophy, cardiomyopathy, or valvular disease
- ·Pre-existing tendon or ligament pathology (strength gain outpaces connective-tissue adaptation)
- ·Bleeding disorders or anticoagulant therapy without physician guidance (injection-site haematoma)
- ·Active skin infection, cellulitis, or lipohypertrophy at intended injection sites
- ·Inability to maintain sterile technique or safe sharps disposal
- ·Not FDA-approved for human therapeutic use — no verified purity, sterility, or potency standards
- ·Immunocompromised or transplant patients (unverified sterility and immunogenicity risk)
- ·Concurrent participation in drug-tested sport (WADA prohibited or non-cleared substance)
- ·Known hypersensitivity or prior reaction to this compound or any excipient/diluent
- ·Pregnancy, attempting conception, or breastfeeding unless prescribed and monitored by a physician
- ·Children and adolescents with open growth plates (unless under specialist endocrine care)
- ·Active or recently treated malignancy without oncology clearance
- ·Use without a confirmed diagnosis, baseline labs, and licensed clinical supervision
Regulatory
Not FDA-approved for any use and not in registered human clinical trials as of this review. Sold online as a "research chemical" — not for human use, not a dietary supplement, and not eligible for standard pharmacy compounding. Follistatin-pathway products are prohibited in sport under WADA's general rules on myostatin inhibitors and non-approved substances.
Veterinary Use (Pets)
No established veterinary protocol for FLGR-242 (Follistatin-Derived Construct). Consult a licensed veterinarian before considering off-label use in any species.
Full veterinary reference →Functional Groups
Cited Works
Tap any study to open the published work.
- 1.Schuelke M et al. Myostatin mutation associated with gross muscle hypertrophy in a child. N Engl J Med. 2004;350:2682-8.Read published work Link not opening? Search Google Scholar
- 2.Lee SJ, McPherron AC. Regulation of myostatin activity and muscle growth. Proc Natl Acad Sci USA. 2001;98:9306-11.Read published work Link not opening? Search Google Scholar
- 3.Amthor H et al. Follistatin complexes myostatin and antagonises myostatin-mediated inhibition of myogenesis. Dev Biol. 2004;270:19-30.Read published work Link not opening? Search Google Scholar
- 4.Kota J et al. Follistatin gene delivery enhances muscle growth and strength in nonhuman primates. Sci Transl Med. 2009;1:6ra15.Read published work Link not opening? Search Google Scholar
- 5.Haidet AM et al. Long-term enhancement of skeletal muscle mass and strength by single gene administration of myostatin inhibitors. Proc Natl Acad Sci USA. 2008;105:4318-22.Read published work Link not opening? Search Google Scholar
- 6.Mendell JR et al. Follistatin gene therapy for Becker muscular dystrophy and sporadic inclusion body myositis (clinical trial program). Mol Ther. 2017;25:870-879.Read published work Link not opening? Search Google Scholar
- 7.Sleep D et al. Non-covalent albumin-binding ligands for extending the circulating half-life of small biotherapeutics. Med Res Rev. 2019;39:715-762.Read published work Link not opening? Search Google Scholar
- 8.World Anti-Doping Agency. The Prohibited List (myostatin inhibitors and non-approved substances prohibited in sport).Read published work Link not opening? Search Google Scholar
- 9.U.S. FDA. Bulk drug substances used in compounding — follistatin products are not approved and not on the 503A bulks list.Read published work Link not opening? Search Google Scholar