u/jcfin

PEG-MGF: Entry #16 of 100+ Peptides
▲ 2 r/peptidehelper+1 crossposts

PEG-MGF: Entry #16 of 100+ Peptides

Same MGF molecule, with a polyethylene glycol leash that makes it last days instead of minutes

TL;DR: PEG-MGF is MGF (the IGF-1Ec C-terminal E-domain peptide) with polyethylene glycol covalently attached, which extends the plasma half-life from ~5 minutes to ~2-3 days. The pitch: get the MGF effect systemically without injecting locally before every workout. The trade: no independent primary literature exists for the pegylated form. The pegylation is a community-engineered modification, not a drug-development program. You are extrapolating from MGF's mechanism and PEG-conjugation's general pharmacokinetics.

Quick facts

·         Aliases: Pegylated Mechano Growth Factor

·         Origin: Community/research-supplier produced; not a registered drug development program

·         Structure: MGF (24-aa E-domain peptide) covalently conjugated to polyethylene glycol

·         Class: Pegylated IGF-1 splice-variant peptide

·         Route: SC or IM

·         Half-life: ~2-3 days (vs. native MGF's ~5 min)

·         Dose (anecdotal): 200-400 mcg SC, 1-2x weekly

·         Regulatory status:

·         No human approvals; no investigational program

·         Research-chemical sourcing only

·         WADA-banned

Mechanism(s) (extrapolated from MGF)

·         Same satellite cell signaling premise as native MGF

·         The pegylation is intended to allow systemic, non-local dosing — which fundamentally changes the pharmacology of a peptide whose endogenous role is local and pulsatile

·         Whether systemic PEG-MGF reproduces local MGF's satellite-cell activation, or just produces a sustained IGF-1Ec signal that satellite cells weren't evolved to respond to chronically, is genuinely an open question

Research highlights

McKoy G et al. 1999 (J Physiol, PMID 10087355): the original MGF paper, the same citation that grounds native MGF. PEG-MGF has no independent indexed primary literature

Honest caveat: the entire body of pharmacokinetic, safety, and efficacy data for PEG-MGF specifically is community-anecdotal. Pegylation can change immunogenicity (anti-PEG antibody formation in a non-trivial percentage of the population) and alter receptor pharmacology in ways that don't always match the parent peptide

Side effects (reported)

·         Injection-site reactions

·         Possible immunogenicity / anti-PEG antibodies in a subset of users (PEG sensitization is a well-documented phenomenon across pegylated drugs)

·         Theoretical cancer concerns, same IGF-1 axis caveats as LR3 / DES / MGF

·         Long-term safety: completely uncharacterized

Why this peptide is on a different evidence tier than the rest of the IGF-1 family:

LR3 has cell-culture and cattle data. DES has biochem and oncology cell-line data. MGF has the McKoy/Goldspink rabbit-muscle work. PEG-MGF has none of those — it has the conceptual logic of "extend MGF's half-life" and that's it. The community has been using it for years without obvious disasters, which is real-world Bayesian evidence of a kind, but it's not the same evidence that you'd want to see before a drug enters an IND.

If you're going to use a peptide in this family, MGF (local, post-workout, with the McKoy paper as the mechanistic basis) is the most defensible choice. PEG-MGF is the one where the gap between "what bodybuilders do" and "what has been studied" is widest. That doesn't mean it doesn't work. It means there is no honest answer to the question "does it work" that doesn't come down to anecdote.

Find more information about PEG-MGF and potential interactions with other peptides here.

u/jcfin — 8 hours ago
▲ 3 r/peptidehelper+1 crossposts

IGF-1 LR3: Entry #13 of 100+ Peptides

Long R3 IGF-1: what bodybuilders use when they want IGF-1's effects without IGF-1's plasma kinetics

TL;DR: 83-aa modified version of IGF-1 with two changes: a 13-aa N-terminal extension and an Arg3 substitution. Both modifications dramatically reduce binding to IGF-binding proteins (IGFBP-3 in particular). Results in much more free IGF-1 floating around, way longer half-life (20-30 hours vs. native IGF-1's 10-15 minutes), and a level of receptor agonism that pushes muscle hyperplasia in animal models. There is essentially no controlled human data for the bodybuilding use case.

Quick facts

·         Aliases: Long R3 IGF-1, LR3-IGF-1

·         Origin: Originally a research reagent for cell-culture work. The Arg3 substitution was designed to study IGFBP-independent IGF-1 signaling. The bodybuilding repurposing came later

·         Structure: 83-aa modified IGF-1; ~9111 Da; Arg3 substitution plus N-terminal 13-aa extension

·         Class: IGF-1 receptor agonist (long-acting analog)

·         Route: SC or IM

·         Half-life: ~20-30 hours, the central design feature

·         Dose (anecdotal): 20-100 mcg SC daily, often timed post-workout

·         Regulatory status:

·         Not approved for any human indication anywhere

·         Sold as a cell-culture research reagent; the bodybuilding use is off-label diversion

·         WADA-banned as part of the IGF-1 / GH axis class

Mechanism(s)

·         Direct IGF-1 receptor agonism on muscle, bone, and most other tissues

·         Reduced IGFBP binding means more of the molecule is bioavailable at any given time

·         Drives satellite cell proliferation, differentiation and protein synthesis simultaneously; that combination is the muscle hyperplasia story

·         Crosses the insulin receptor at high doses, which is the hypoglycemia risk

Research highlights

·         Hammon H et al. 1997 (Am J Physiol, PMID 9252489): the foundational paper on Long R3-IGF-1 modulating the somatotropic axis in neonatal calves. Most LR3 dosing intuition comes from cattle and cell culture work, not human RCTs

·         Cell-culture work, the original use case: LR3 is the standard reagent for studying IGF-1 signaling without IGFBP confounders

·         Honest caveat: there is no published Phase 1/2 in humans for the bodybuilding indication. Everything written about LR3 dosing in humans is anecdotal or extrapolated from cattle physiology

Side effects (reported)

·         Hypoglycemia, especially at higher doses or fasted states. This is the most common acute adverse event

·         Disproportional tissue growth (the "IGF-1 gut" rumor in bodybuilding circles, which has not been formally documented but is consistent with prolonged IGFR agonism on visceral organs)

·         Theoretical cancer-progression risk via IGF-1 axis

·         Injection site irritation

·         Tachyphylaxis after weeks of continuous daily use, which is why most users cycle

The unresolved tension:

LR3 is doing something IGF-1 in your body normally cannot do. Native IGF-1 is bound to IGFBP-3 and the acid-labile subunit ~99% of the time, with the binding proteins acting as a slow-release reservoir and keeping the bioactive fraction in a narrow physiologic window. LR3 broke that ratio on purpose to make a useful research tool. The acute effects are well characterized in cell culture and short animal studies. The chronic systemic consequences in healthy adults are not.

Find more information about IGF-1 LR3 and potential interactions with other peptides here.

u/jcfin — 3 days ago
▲ 3 r/peptidehelper+1 crossposts

Somatropin (recombinant HGH): Entry #12 of 100+ Peptides

TL;DR: 191-amino-acid recombinant human growth hormone, identical to pituitary-secreted GH. Sold under a long list of brand names (Humatrope, Genotropin, Norditropin, Saizen, etc.). FDA-approved for pediatric and adult GH deficiency, Turner, Prader-Willi, idiopathic short stature, AIDS wasting, and short bowel. Schedule III in the U.S. for non-medical use, illegal to distribute off-label. Every other peptide in this cluster (sermorelin, CJC-1295, ipamorelin, tesamorelin, MK-677) is either a workaround for the legal status or an attempt to drive GH the body's own way instead of bypassing the pituitary.

Quick facts

  • Aliases: Recombinant hGH; Humatrope, Genotropin, Norditropin, Saizen, Omnitrope, etc.
  • Origin: Recombinant E. coli expression (Genentech, 1985; replaced cadaver-derived hGH after the CJD contamination crisis)
  • Structure: 191-aa recombinant hGH, MW ~22 kDa
  • Class: Direct growth hormone receptor agonist
  • Route: SC daily (some protocols 6/7 days, weekend off)
  • Half-life: 2-5 hours subcutaneous; effective biological half-life longer due to IGF-1 induction
  • Dose: 0.15-0.3 mg/day SC for adult GHD on label; 1-2 IU/day off-label "anti-aging"; 4-12 IU/day in performance use (well outside any therapeutic range)
  • Regulatory status:
  • FDA-approved for multiple indication above
  • Schedule III for off-label distribution (a felony in the U.S.)
  • Banned in WADA-tested sport
  • Long-acting weekly versions (lonapegsomatropin/Skytrofa, somatrogon/Ngenla) recently approved

Mechanism(s)

  • Direct GH receptor agonism on hepatocytes leading to IGF-1 production
  • Direct GHR signaling on muscle, adipose, bone via the JAK2/STAT5 pathway
  • Lipolysis (fat loss) and protein anabolism (lean mass) at supraphysiologic doses; that's the cosmetic appeal
  • Chronic dosing down-regulates pulsatile endogenous secretion. This is the central pharmacological difference from sermorelin or ipamorelin: HGH replaces the system, GHRH/GHRP analogs work with it

Research highlights

Side effects (reported)

  • Edema, carpal tunnel, arthralgia (the classic dose-dependent triad)
  • Insulin resistance, frank type 2 diabetes at high chronic doses
  • Acromegaly features (jaw, hands, feet, organomegaly) at sustained supraphysiologic dosing
  • Theoretical and somewhat-supported cancer-progression risk (IGF-1 axis)
  • In children with GHD, generally well tolerated; in non-deficient adults, the risk-benefit gets steeply worse with dose

Find more information about Somatropin (HGH) and potential interactions with other peptides here.

u/jcfin — 4 days ago

GHRP-6: Entry #11 of 100+ Peptides

TL;DR

GHRP-6 is the original growth hormone releasing peptide. It was developed in 1984 by Cyril Bowers' group at Tulane University and became the first strong proof that an unknown growth hormone secretagogue receptor existed. That receptor was later identified as GHS-R1a, now known as the ghrelin receptor.

Modern compounds like GHRP-2, hexarelin, and ipamorelin all descend from this discovery. GHRP-6 was effectively the prototype for the entire GHRP class.

Quick Facts

  • Full name: Growth Hormone Releasing Peptide-6
  • Developed by: Cyril Bowers et al., Tulane University
  • First described: 1984
  • Structure: His-D-Trp-Ala-Trp-D-Phe-Lys-NH2
  • Class: GHRP / ghrelin receptor agonist
  • Administration: Primarily subcutaneous injection; intranasal routes appeared in older studies
  • Half-life: Approximately 15 to 30 minutes
  • Common anecdotal dosing: 100 to 300 mcg SC, 2 to 3 times daily

Regulatory Status

  • Never FDA approved
  • Studied experimentally in cardiac and inflammatory settings
  • Listed in FDA 503A Category 2, alongside compounds such as BPC-157

Mechanism of Action

GHRP-6 acts primarily as a GHS-R1a agonist, stimulating pulsatile growth hormone release while also strongly increasing appetite. The hunger effect is one of its most recognizable characteristics and separates it from newer compounds like ipamorelin.

Unlike more selective modern secretagogues, GHRP-6 can also increase cortisol and prolactin levels in a dose-dependent manner. Those hormonal spillover effects were one of the reasons later compounds were developed.

Researchers have also explored possible cardioprotective effects in animal models. Some evidence suggests these actions may involve receptor subtypes outside the pituitary pathway.

Synergy With Other GH Pathway Compounds

GHRP-6 is commonly discussed alongside GHRH analogs because the pathways complement each other.

Examples include:

Using both pathways together generally produces a stronger GH pulse than either pathway alone.

Key Research

Bowers et al. (1984)

Endocrinology | PMID: 6714155

This was the foundational paper for the entire class. The study demonstrated that a synthetic hexapeptide could trigger potent GH release in rat and ovine somatotrophs through a receptor distinct from the GHRH receptor.

Wu et al. (1996)

Journal of Endocrinology | PMID: 8699133

Compared GHRP-6 and GHRP-2 in terms of cAMP signaling and GH secretion dynamics.

Granado et al. (2008)

Journal of Endocrinology

Investigated cardioprotective effects in rodent ischemia-reperfusion models.

Important Caveat

Like most GHRPs, the modern recreational use of GHRP-6 rests heavily on mechanistic studies, animal data, and small human trials. Large-scale clinical success never materialized. One major failed postoperative ileus trial also contributed to the collapse of corporate development for related compounds such as ipamorelin.

Reported Side Effects

The defining side effect is rapid appetite stimulation, often occurring within 20 to 40 minutes after administration.

Other commonly reported effects include:

  • Increased hunger
  • Mild cortisol elevation
  • Mild prolactin elevation
  • Water retention
  • Temporary tingling or numbness near the injection site
  • Fatigue or heavy eyelids after dosing

These effects appear dose dependent in many users.

Why People Still Use It

Despite newer and cleaner compounds existing, GHRP-6 still has a niche.

The main reasons are straightforward:

  • It is relatively inexpensive
  • It is widely available in research markets
  • Some users specifically want the appetite stimulation

That appetite effect makes it appealing in certain contexts, including:

  • Bulking phases in bodybuilding
  • Medically supervised recovery from appetite suppression
  • Cachexia-related experimentation

For users focused purely on cleaner GH signaling with fewer side effects, compounds like ipamorelin or hexarelin are generally considered more refined tools.

Historical Significance

The importance of GHRP-6 goes beyond its current use.

Bowers' group was originally attempting to create a cholecystokinin-related analog. Instead, they accidentally discovered a compound that revealed an entirely new endocrine signaling pathway. That observation eventually led to the identification of the ghrelin receptor and the development of the entire GHRP category.

Pretty much every modern ghrelin receptor agonist traces back to this discovery. No exxageration.

Learn more, as always, here.

u/jcfin — 6 days ago
▲ 4 r/peptidehelper+1 crossposts

Tesamorelin: Entry #9 of 100+ Peptides

Synthetic GHRH analog (44-aa peptide) that stimulates pituitary release of endogenous growth hormone.

Quick facts

  • Class: GHRH receptor agonist
  • Route: SC daily injection
  • Regulatory status:
  • Not approved for general anti-aging or weight loss
  • Available by prescription; reformulated as Egrifta SV in

Mechanism(s)

  • Spares peripheral subcutaneous fat in trial data; thatselectivity is what made the HIV-lipodystrophy approval possible

.

Research highlights

Faulk - Metabolic effects of a growth hormone-releasing factor in patients with HIV

Stanley TL et al. Reduction in visceral adiposity with tesamorelin and improved metabolic profile in HIV-infected patients. Clin Infect Dis 2012. PMID 22495074

• ⁠What we don't have: any large RCT outside HIV lipodystrophy. The off-label "tesamorelin for visceral fat in metabolic syndrome" use is mostly extrapolation

Side effects (reported)

  • Injection site reactions (the most common reason for trial dropout)
  • Joint pain, edema, hyperglycemia
  • Glucose intolerance, especially in pre-diabetic patients
  • Class warning shared with all GH-axis stimulators: any active malignancy is a hard contraindication

The interesting part mechanistically:

Tesamorelin's whole identity is seemingly a paradox in review. GH and IGF-1 are generally lipolytic but also generally diabetogenic; push the GH axis hard and you usually trade fat loss for worse glucose control. The HIV lipodystrophy trials showed the opposite: VAT dropped, triglycerides dropped, and metabolic markers actually improved.

The leading explanation is that visceral adipose in HIV lipodystrophy is inflammatory and is GH-resistant before treatment, so a GHRH-stimulated pulse re-sensitizes it to lipolysis without the expected insulin-resistance downside you'd see in a metabolically healthy person.

This is dense as hell though. So if you're still interested you can find more information about Tesamorelin and potential interactions with other peptides here.

u/jcfin — 7 days ago

Post your peptide-related questions!

I want this place to be the best sub on reddit for posting and actually getting questions answered well!

I’ll try to answer as many questions myself as I can, but ultimately the vision is for this site to be the ultimate combo of scientific resource/friendly forum.

reddit.com
u/jcfin — 8 days ago

Ipamorelin: Entry #7 of 100+ Peptides

Ipamorelin: the GHRP that doesn't make you cortisol-spike

TL;DR: Pentapeptide ghrelin-receptor agonist developed at Novo Nordisk in the late 90s. The thing that put it on the GH-stack crowd's radar is what it doesn't do: it pushes GH without the cortisol bump, prolactin bump, or wreck-your-day hunger that older GHRPs (GHRP-2, GHRP-6, hexarelin) brought along for the ride. Most commonly stacked with CJC-1295 no-DAC.

Quick facts

Aliases: NNC 26-0161

Origin: Novo Nordisk, late 1990s. Designed as a selective GHS-R1a agonist

Structure: Aib-His-D-2-Nal-D-Phe-Lys-NH2 (pentapeptide)

Class: Growth hormone-releasing peptide (GHRP) / ghrelin receptor agonist

Route: SC injection

Half-life: ~2 hours

Doses (research/anecdotal): 200-300 mcg SC, 2-3x daily, often timed pre-bed and post-workout

Regulatory status:

Not FDA-approved for any indication

Phase 2 work was done in the early 2000s for postoperative ileus (Helsinn) and stalled

Listed as a research chemical; compounding pharmacies in the U.S. cannot dispense it as a human prescription post-2023 503A categorization

Mechanism(s)
Selective GHS-R1a agonism at the anterior pituitary → pulsatile GH release

Minimal off-target activity at ACTH/cortisol or prolactin pathways, which is the design selling point

Synergizes with GHRH-axis drugs (CJC-1295, sermorelin) — dual-pathway activation gives a bigger pulse than either alone

Research highlights
Raun K et al. 1998 (Eur J Endocrinol, PMID 9849822): the original characterization paper. Showed potent GH release in pigs and rats with no measurable ACTH or prolactin elevation

Beck DE et al. 2014 (J Gastrointest Surg): Phase 2 in postop ileus — failed primary endpoint, killed corporate development

Honest caveat: for a peptide this widely used, there is essentially no controlled human data on the chronic anti-aging/recovery indications people are actually taking it for

Side effects (reported)

Mild fatigue and headache, especially at start

Injection site reactions

IGF-1 elevation with chronic use (theoretical insulin-resistance risk if pushed)

Tachyphylaxis if dosed continuously without a pulse pattern

Comparison vs. the rest of the GHRPs

Ipamorelin and GHRP-6 hit the same receptor. The difference is everything in their off-target profile. GHRP-6 was the original — it works, but it stings you with hunger and bumps cortisol. GHRP-2 cleaned that up partly. Ipamorelin cleaned it up the rest of the way. If you read older bodybuilding forums you'll see GHRP-6 + CJC-1295; modern stacks almost universally swapped to ipamorelin once it became compoundable.

The unanswered question is whether selective GHS-R agonism is enough on its own. Ghrelin's natural job is to coordinate hunger, GH, and reward — strip out the off-target effects and you get a cleaner GH pulse, but you also lose whatever reason ghrelin signaling co-opted those pathways in the first place. Long-term consequences aren't characterized.

Find more information about Ipamorelin and potential interactions with other peptides here.

reddit.com
u/jcfin — 9 days ago

No video is going to be perfect, but at least this is a break from the massive info dumps I usually post! Same as always, please check out more than one source before making any decisions about research for your lab rat.

This is different and important since we haven’t discussed stacking these two yet. Plus I think it’s easier to digest than reading dense academic research sometimes.

u/jcfin — 9 days ago

TB-500: the actin-sequestering fragment that became BPC-157's running mate

TL;DR: TB-500 is a synthetic 7–amino acid peptide (LKKTETQ) derived from the larger Thymosin β4 protein. It is commonly discussed alongside BPC-157 in experimental and online communities, particularly in the context of tissue repair. Its mechanism differs from many peptides in that it acts on cytoskeletal dynamics rather than binding to a traditional receptor. Human clinical evidence remains limited, and regulatory restrictions apply in both medical and athletic settings.

Quick facts

  • Class: Tissue repair / cytoskeletal regulator
  • Studied administration routes: Subcutaneous (SC), intramuscular (IM)
  • Estimated half-life: Several hours, with extended tissue uptake

Regulatory status:

  • Not FDA-approved
  • Marketed as a research chemical

Mechanism(s)

  • G-actin sequestration: Binds free actin monomers, regulating the equilibrium between monomeric (G-actin) and filamentous (F-actin) forms
  • Cell migration: Cytoskeletal reorganization supports movement of fibroblasts and endothelial cells during tissue repair
  • Anti-inflammatory: Downregulates NF-κB signaling in some models
  • Hair follicle activity: Observed activation of follicular stem cells in animal studies, forming the basis for off-label cosmetic interest

Research highlights

Caveat: Most Much of the available research focuses on full-length Thymosin β4 rather than the TB-500 fragment specifically. Whether the fragment reproduces the full biological activity in humans remains unproven.

Side effects (reported)

  • Injection site pain
  • Anecdotal reports of lethargy or cognitive “fog”
  • Theoretical proliferation concerns (it's a wound-healing peptide; same tumor-growth worries as BPC-
  • WADA ban means competitive athletes test positive

The interesting part mechanistically:

Unlike many peptides that function through receptor binding and downstream signaling, TB-500 appears to act through direct interaction with intracellular structural proteins. By binding G-actin and altering cytoskeletal dynamics, it influences cell shape and motility. This represents a fundamentally different pharmacological approach, closer to modifying cellular architecture than activating a signaling pathway. This distinction also explains why it is often conceptually paired with BPC-157. The two compounds are proposed to target similar biological outcomes such as wound healing through different mechanisms.

Find more information about TB-500 and potential interactions with other peptides here. Also feel free to check out the tools for peptide evaulations!

The site included above is my personal passion project and includes NO suppliers, and every tool/resource is totally free. Please check if you need. It is just a reference/toolkit that beginners can use to get educated and understand their peptides before beginning their research.

​

reddit.com
u/jcfin — 11 days ago
▲ 3 r/peptidehelper+1 crossposts

BPC-157: the "body protection compound"

TL;DR: 15-amino-acid fragment of a stomach-juice protein. Wildly popular for tendon, ligament, and gut healing. Almost zero human data. Compounding pharmacies were hit hard by FDA's 2023 categorization. Pivot from the GLP-1 hype-train to something with a very different evidence story.

Quick facts

  • Structure: Synthetic pentadecapeptide (sequence: GEPPPGKPADDAGLV)
  • Class: Cytoprotective peptide
  • Studied administration routes: Subcutaneous (SC), intramuscular (IM), oral, intranasal

Regulatory status:

  • Not approved by the U.S. FDA for any medical indication
  • Continues to be marketed online as a “research chemical”

Mechanism(s)

  • Growth factor signaling: Associated with increased expression of growth hormone receptors and fibroblast growth factors in connective tissue
  • Nitric oxide modulation: Demonstrates bidirectional interaction with nitric oxide pathways in preclinical models
  • Dopaminergic effects: Animal studies suggest modulation of dopamine-related responses
  • Gastrointestinal protection: Appears to support mucosal integrity and reduce NSAID-induced damage in rodent models

Research highlights

Honest caveat: The vast majority of citations are animal models from a single Croatian research group (Sikiric et al.). Independent replication is thin. There is no published Phase 2/3 human trial.

Side effects (reported)

  • Injection site irritation
  • No notable systemic toxicity in rodent studies even at high doses
  • Theoretical concerns: pro-angiogenic activity raises a tumor-growth question. This has not been evaluated in human trials.

The interesting part mechanistically:

BPC-157 is notable for being derived from a protein naturally present in gastric juice, which underlies the rationale for oral administration—unusual for peptides, which are typically degraded in the digestive tract. The central question remains whether systemic administration (e.g., subcutaneous injection) produces the same effects as its proposed local activity in the gastrointestinal environment, or whether it behaves as a distinct pharmacological agent.

Find more information about BPC-157 and potential interactions with other peptides here. There are also some tools for comparing these peptides given how dense all of the information can be!

***The site included above is my personal passion project and includes NO suppliers, and every tool/resource is totally free. Please check if you need. It is just a reference/toolkit that beginners can use to get educated and understand their peptides before beginning their research.

u/jcfin — 1 day ago

Tirzepatide: the dual agonist that beat semaglutide head-to-head TL;DR: 39-amino-acid dual agonist at the GIP and GLP-1 receptors. SURMOUNT-1 reported ~22.5% mean weight loss at 72 weeks at the 15 mg dose — meaningfully higher than semaglutide's ~15%. SURPASS-2 beat semaglutide head-to-head on HbA1c and weight in T2D. Same C20 fatty diacid albumin-binding trick as semaglutide, with one extra receptor everyone used to think was the wrong one to target.

Quick facts • Aliases: LY3298176, Mounjaro, Zepbound

• Origin: 39-aa synthetic peptide based on the GIP backbone, engineered for dual GIP-R + GLP-1R activity, with a C20 fatty diacid for albumin binding

• MW: ~4813 Da • Class: GIP / GLP-1 dual receptor agonist (the first approved dual incretin) • Route: SC weekly injection

• Half-life: ~5 days • Doses: 2.5 mg start, titrated to a max of 15 mg weekly

Regulatory status:

• FDA-approved: Mounjaro (T2D, 2022), Zepbound (chronic weight management, 2023)

• Same thyroid C-cell tumor black-box warning as the GLP-1 class

Mechanism(s)

• GLP-1R agonism: same axis as semaglutide — insulin secretion, gastric emptying delay, central satiety, glucagon suppression

• GIP receptor agonism: the differentiator. GIP-R activation enhances insulin secretion and appears to improve adipose tissue insulin sensitivity. Centrally, GIP-R neurons in the hypothalamus suppress food intake through pathways distinct from GLP-1

• Synergy, not additivity: in head-to-head trials the dual agonist outperforms maximal-dose GLP-1 monotherapy by more than the GIP arm alone would predict

• Albumin binding: C20 diacid (one carbon longer than semaglutide's C18) extends half-life similarly

Research highlights

• Jastreboff AM et al. 2022 (NEJM, PMID 35658024): SURMOUNT-1 — 20.9% (10 mg) and 22.5% (15 mg) weight loss at 72 weeks in obesity without diabetes

• Frias JP et al. 2021 (NEJM): SURPASS-2 — head-to-head vs. semaglutide 1 mg in T2D; tirzepatide superior on HbA1c reduction and weight loss across all doses

• SURMOUNT-2 (PMID 37385275): efficacy in T2D with obesity • SURMOUNT-3 / SURMOUNT-4: durability and lifestyle-intervention combinations

Side effects (reported)

• Nausea, vomiting, diarrhea (dose-dependent, titrate to mitigate)

• Constipation

• Pancreatitis (rare, listed)

• Gallbladder events

• Black-box warning: thyroid C-cell tumors (same class warning as semaglutide)

• Hypoglycemia when combined with insulin or sulfonylureas

The interesting part mechanistically:

For decades GIP was considered the wrong incretin to target for obesity. Older receptor-knockout work in mice suggested that knocking out GIP signaling protected against diet-induced obesity, which read as: GIP agonism would make people fatter. Tirzepatide is the result of someone at Lilly betting the opposite — that chronic GIP-R agonism, paired with GLP-1, would amplify weight loss rather than blunt it. They were right, but the mechanistic explanation is still being argued. The leading hypothesis: sustained GIP-R agonism functionally desensitizes the receptor in adipose tissue (so the "stores fat" signal blunts) while preserving the pancreatic insulinotropic effect — and centrally, GIP-R activation suppresses appetite through a hypothalamic neuron population separate from GLP-1's. The SURMOUNT-1 vs. STEP-1 delta is one of the cleanest "second receptor matters" demonstrations in modern incretin pharmacology. It's also exactly why retatrutide (next entry) bolted on a third.

Find more information about Tirzepatide and potential interactions with other peptides here.

***The site included above is my personal passion project and includes NO suppliers, and every tool/resource is totally free. Please check if you need. It is just a reference/toolkit that beginners can use to get educated and understand their peptides before beginning their research.

u/jcfin — 14 days ago

Semaglutide: the molecule that turned GLP-1 into a household word

TL;DR: 31-amino-acid modified GLP-1 with a C18 fatty diacid linker that latches onto serum albumin and stretches a 1-2 minute native peptide into a 7-day weekly drug. Marketed as Ozempic (T2D), Wegovy (obesity), Rybelsus (oral T2D). The SELECT trial established cardiovascular benefit in non-diabetic obesity — that's the result that pushed it from "diabetes drug" to "category-defining weight-loss drug."

Quick facts

·  Aliases: NN9535, Ozempic, Wegovy, Rybelsus

·  Origin: Modified human GLP-1(7-37); two amino acid substitutions (Aib8, Arg34) plus a glutamic acid spacer + C18 fatty diacid attached at Lys26

·  MW: ~4114 Da

·  Class: GLP-1 receptor agonist

·  Routes: SC weekly injection (Ozempic / Wegovy); oral daily (Rybelsus, with SNAC absorption enhancer)

·  Half-life: ~7 days

Regulatory status:

·  FDA-approved: Ozempic (T2D, 2017), Rybelsus (T2D, 2019), Wegovy (obesity, 2021)

·  Black-box warning for thyroid C-cell tumors (rodent finding)

·    Intermittent shortages on FDA's drug shortage list during the obesity boom — drove the compounded-semaglutide market

Mechanism(s)

·  GLP-1R agonism on pancreatic β-cells: glucose-dependent insulin secretion (insulin only releases when glucose is elevated, which limits hypoglycemia risk vs. insulin/sulfonylureas)

·  Gastric emptying delay: slower glucose appearance, prolonged satiety

·  Central appetite suppression: hypothalamic and brainstem GLP-1R activation → reduced food intake, reduced food reward

·  Glucagon suppression: lowers hepatic glucose output

·  Albumin binding via the C18 linker: the actual half-life trick — non-covalently anchors to albumin in serum and rides around for a week

Research highlights

·  Wilding JPH et al. 2021 (NEJM, PMID 33567185): STEP 1 — 14.9% weight loss at 68 weeks in adults with overweight/obesity (the headline obesity result)

·  Lincoff AM et al. 2023 (NEJM, PMID 37952131): SELECT — 20% reduction in major adverse cardiovascular events in obese non-diabetic patients; established the cardiovascular indication

·  Marso SP et al. 2016 (NEJM): SUSTAIN-6 — earlier T2D cardiovascular outcomes trial; basis of the original CV label

Side effects (reported)

·  Nausea (most common, dose-related, usually decreases over weeks)

·  Vomiting, constipation, diarrhea

·  Pancreatitis (rare)

·  Gallbladder disease (cholelithiasis / cholecystitis)

·  Black-box warning (Serious Side-Effect): Thyroid C-cell tumors are possible based on rodent data, although it's uncertain if this has any relevance to humans yet. Contraindicated in MEN2 / personal or family history of medullary thyroid carcinoma

·  Injection-site reactions (ya feel itching/redness)

The interesting part mechanistically:

Native GLP-1 has a half-life of 1-2 minutes. DPP-4 protease snips off the N-terminus almost as fast as the gut secretes it. Every GLP-1 drug since exenatide has been an answer to "how do you keep the molecule alive long enough to dose practically." Semaglutide's answer is the cleanest version of the playbook: protect the N-terminus from DPP-4 (Aib substitution at position 8), block another cleavage site (Arg at 34), then dangle a C18 fatty diacid off the side that quietly binds albumin in serum.

Find more information about Semaglutide and potential interactions with other peptides here.

***The site included above is my personal passion project and includes NO suppliers, and every tool/resource is totally free. Please check if you need. It is just a reference/toolkit that beginners can use to get educated and understand their peptides before beginning their research.

u/jcfin — 14 days ago
▲ 5 r/peptidehelper+4 crossposts

Peptidehelper.org - Guide & Forum for those seeking reliable peptide information.

Has a suite of tools to help newcomers learn and understand peptides & how to conduct their own independent research!

It has in-depth, pertinent information & links to academic sources that support each of the peptide’s claims (some peptides don’t have much yet due to being experimental in nature).

There are currently 100+ catalogued research peptides and more information is always being added!

It includes the following features:

Peptide Library - A complete resource of a large variety of peptides and pertinent information about their approval level, purpoted effects, mechanisms, etc.

A Dosage Calculator

Peptide Combination/Stack Evaluator - Helps independent researchers understand how certain combinations of peptides create redundancies, potential dangers, but also can identify potentially synergistic research stacks. (Shows which pathways are impacted by which peptides & how they work together)

Head-to-Head Peptide Comparison - Compare different peptides based on effect, level of evidence, current approval phase (FDA Approved, Phase 2 trials, Approval in other countries, etc. - Useful for figuring out stacks and which peptides are potentially more risky for research.

Interaction Matrix - High-level chart that shows how every peptide would theoretically interact with all of the others based on the current understanding of academic research. Conveys information more rapidly than conducting individual evaluations.

Essential Guides - Storage, basic supplies, proper lyophilized peptide reconstitution technique, and administration techniques.

Essential Research Supplies - Links to find basics on Amazon and other easily accessible, reputable sites.

IMPORTANT NOTES:

  1. Always use more than one resource before moving forward with any research protocol.

  2. This is an active project. Information moves quickly so always verify with other sources before acting on the information found here.

  3. Remember that many of the peptides are NOT for human use. Know the risks and ALWAYS consult a doctor or licensed medical professional before conducting any kind of research.

Best of luck!!!

u/jcfin — 3 days ago