Peptide bioregulators
Met-Enkephalin
An endogenous five-amino-acid opioid that quietly puts a brake on cell division — well-studied in oncology and immunology labs, but that's not the same as a validated self-use protocol.
Research chemical Peptide bioregulators
- Full name
- Methionine-Enkephalin (Opioid Growth Factor, OGF)
- Also known as
- OGF, [Met5]-enkephalin, Methionine enkephalin, Opioid Growth Factor
- Regulatory status
- Endogenous human peptide (naturally produced). Not FDA-approved as a drug in its own right; investigated in early-phase oncology trials as 'OGF' biotherapy and mechanistically tied to low-dose naltrexone (LDN) research, which itself is used off-label.
Origin
Met-enkephalin (Tyr-Gly-Gly-Phe-Met) is one of the body's native opioid peptides, derived from proteolytic processing of proenkephalin. Beyond its classical role as a weak opioid-receptor ligand, a specific pool of it functions as the 'opioid growth factor' (OGF) — an autocrine/paracrine signal that acts through a distinct, non-classical receptor (OGFr) to regulate cell replication.
Mechanism
OGF (Met-enkephalin) binds OGFr and traffics into the cell nucleus, where it upregulates cyclin-dependent kinase inhibitors (p16, p21), delaying the G1/S transition of the cell cycle and slowing proliferation. This is the same axis proposed to underlie low-dose naltrexone's effects: brief opioid receptor blockade triggers compensatory upregulation of OGF and OGFr, amplifying the inhibitory signal once blockade wears off — a rebound mechanism distinct from naltrexone's classical opioid antagonism.
Research summary
Evidence
Human data is limited mostly to small early-phase oncology trials using OGF as an adjunct biotherapy, plus indirect clinical experience via low-dose naltrexone (which is not the same compound but is mechanistically linked). The bulk of solid evidence is in vitro and in xenograft/animal models: the OGF-OGFr axis has been shown to inhibit proliferation across multiple human cancer cell lines (triple-negative breast, thyroid follicular, pancreatic, ovarian, colorectal, squamous cell), consistently via p16/p21-mediated cell-cycle arrest, and mutations in OGFr found in human tumors can blunt this response. Immune-modulating and wound-healing/homeostatic roles are also documented, chiefly in rodent models. No robust randomized controlled trial has established Met-enkephalin itself as a clinical therapy.
Evidence tier: Research chemical — see the methodology note for how this is assessed.
Citations
- The opioid growth factor-opioid growth factor receptor axis: homeostatic regulator of cell proliferation and its implications for health and disease — McLaughlin PJ, Zagon IS (2012)
- Opioid growth factor - opioid growth factor receptor axis inhibits proliferation of triple negative breast cancer — Zagon IS, Porterfield NK, McLaughlin PJ (2013)
- Low-dose naltrexone targets the opioid growth factor-opioid growth factor receptor pathway to inhibit cell proliferation: mechanistic evidence from a tissue culture model — Donahue RN, McLaughlin PJ, Zagon IS (2011)
- Growth inhibition of thyroid follicular cell-derived cancers by the opioid growth factor (OGF) - opioid growth factor receptor (OGFr) axis — McLaughlin PJ, Zagon IS, Park SS, et al. (2009)
- Mutations in the opioid growth factor receptor in human cancers alter receptor function — Kren NP, Zagon IS, McLaughlin PJ (2015)
Reported benefits
- Cell-cycle arrest / growth inhibition of cancer cell lines in vitro and in animal xenograft models
- Proposed synergy with chemotherapy agents (e.g., paclitaxel) in preclinical models
- Immune-modulatory and homeostatic signaling implicated in wound healing and autoimmune disease models
- Mechanistic basis cited for low-dose naltrexone's reported effects in autoimmune and oncology self-experimentation contexts
Dosing protocols reported in the literature & community
These are protocols reported by compounding pharmacies, published trials, or self-experimentation communities — not a prescription. Start low, especially for anything new.
| Route | Reported protocol |
|---|---|
| Intravenous (clinical trial context, historical) | Early oncology trials investigated OGF infusions in defined clinical protocols under medical supervision; these are not replicable or safe outside a trial/clinical setting and specific dosing is not something to extrapolate for self-use. |
| Subcutaneous (self-experimentation reports) | Community-reported use (loosely modeled on published rodent dosing, roughly 0.1-1 mg/kg equivalents scaled down) is speculative and not validated in controlled human studies — genuine dosing standards do not exist outside supervised trials. |
Side effects
- Because it interacts with opioid-receptor-adjacent pathways, theoretical risk of interaction with opioid medications or endogenous opioid tone
- Injection-site reactions reported anecdotally
- Unknown long-term effects of exogenous administration outside short clinical trial windows
- Tumor cells with OGFr mutations may not respond as expected, complicating any assumption of predictable growth-inhibitory effect
Safety notes
Community & reddit notes (anecdotal — not clinical evidence)
In self-experimentation and biohacking circles, Met-enkephalin/OGF is discussed mostly as the 'mechanistic explanation' for why low-dose naltrexone might work in autoimmune and oncology-adjacent contexts, rather than as a peptide people commonly inject directly — actual first-hand use reports are far rarer than LDN reports themselves.