Melanin-concentrating hormone

MCH is made by lateral hypothalamic neurons intermingled with the orexin neurons but firing in almost the opposite pattern: MCH neurons are near-silent during wake, active during non-REM sleep and maximally active during REM. Optogenetic and chemogenetic activation of these neurons in rodents increases REM sleep, and ablating them reduces it, making MCH one of the few genuinely REM-selective signals identified. It signals through MCHR1, a Gi/Gq-coupled receptor densely expressed in the nucleus accumbens and hypothalamus; humans and other primates also express MCHR2, whereas rodents do not, which has repeatedly wrecked the translation of rodent MCH pharmacology into humans. On the metabolic side MCH is orexigenic and reduces energy expenditure, so the entire commercial interest has been in MCHR1 antagonists for obesity — a programme that has produced a long series of failures on cardiac and hepatic safety grounds rather than efficacy.

Targets: MCH receptor 1 (MCHR1), MCH receptor 2 (MCHR2, primates only), REM sleep-generating circuits in the lateral hypothalamus, Nucleus accumbens feeding and reward circuitry

• · MCH has no human dosing protocol. Every meaningful sleep finding comes from intracerebroventricular infusion or optogenetic manipulation of MCH neurons in rodents. Peripheral MCH does not usefully reach the receptors that produce the REM effect.

Work out your exact syringe units →

• commonMarked increase in food intake— The most reproducible effect of MCH administration in animals.
• commonReduced energy expenditure and weight gain— Chronic central administration causes obesity in rodents.
• commonExcessive REM sleep and daytime sleepiness— Inferred from the animal sleep phenotype, not measured in humans.
• commonUnknown human safety profile— No human administration data exists.

• Any human use - MCH agonism has never been tested in a person and the predictable outcome is weight gain and hypersomnia.
• Obesity or metabolic syndrome - the pharmacology runs directly against the goal.
• Narcolepsy or idiopathic hypersomnia - pushing REM pressure up is the wrong direction.

• conflictorexin-a-wake — MCH and orexin neurons are physically interleaved in the lateral hypothalamus and functionally opposed - MCH promotes REM and feeding, orexin promotes wake and suppresses REM.
• cautiondsip — Both are marketed on sleep-deepening grounds but act on different sleep stages; there is no data on combining them and no reason to.

• · Not applicable outside research. Body weight and food intake would be the first things to change if anyone did administer it.
• · Polysomnography with REM staging is the only way to observe the effect this compound is known for.

Research reagent only. Never approved or clinically trialled as an agonist therapy in humans.

• Verret et al. 2003, a role for MCH neurons in paradoxical sleep regulation (preclinical)
• Konadhode et al. 2013, optogenetic stimulation of MCH neurons increases sleep (preclinical)
• Diniz & Bittencourt, MCH and sleep regulation review (review)
• Al-Massadi et al. 2021, Nature Reviews Endocrinology - MCH and mammalian energy homeostasis (review)

MCH is one of the two lateral hypothalamic peptide systems that between them arbitrate sleep and wake, and understanding it properly means understanding it against orexin. The two populations are physically interleaved in the lateral hypothalamus and functionally opposed. Orexin neurons fire during wake and are silent in REM. MCH neurons do the reverse: near-silent during wake, active during non-REM sleep, and maximally active during REM. That firing pattern was the first clue and it has held up under every subsequent method. Verret, Luppi and colleagues showed in BMC Neuroscience in 2003 that MCH neurons are activated during paradoxical (REM) sleep and that intracerebroventricular MCH increases it. Konadhode, Shiromani and colleagues then closed the loop optogenetically in the Journal of Neuroscience in 2013 - direct stimulation of MCH neurons increased sleep, and lesion or ablation studies reduce REM. Very few sleep signals are this selectively tied to a single sleep stage, and that is what makes MCH genuinely important neuroscience rather than a curiosity. The receptor pharmacology is where translation has repeatedly died. MCHR1 is a class A GPCR that couples to both Gi/Go and Gq, so it inhibits adenylate cyclase and lowers cAMP while also mobilising intracellular calcium via phospholipase C. It is densely expressed in the nucleus accumbens shell, hypothalamus, hippocampus and cortex. MCHR2 exists in humans, non-human primates, ferrets and dogs - and does not exist as a functional receptor in rodents. That single fact has wrecked more drug programmes than almost any other species difference in metabolic pharmacology. Every elegant MCHR1 result in a mouse is generated in an animal that lacks half the human receptor system. On the metabolic side MCH is orexigenic and lowers energy expenditure. Chronic central administration produces obesity in rodents; MCH knockouts are lean and hypophagic. Al-Massadi and colleagues reviewed the full picture in Nature Reviews Endocrinology in 2021, and the picture is that MCH sits at an integration point between feeding, reward, energy expenditure and sleep - which is not a coincidence, since REM sleep, feeding and reward are all things the lateral hypothalamus coordinates. Which brings the commercial history, and it runs entirely in the opposite direction from anything sold as a peptide. Nobody in the pharmaceutical industry has ever wanted to give people MCH. Everybody has wanted to block it, as an anti-obesity strategy, and multiple MCHR1 antagonist programmes have been taken into development and stopped. The failures have generally been on safety grounds - cardiac effects including QT liability, and hepatic signals - rather than on lack of efficacy, which is a particularly frustrating pattern because it suggests the biology works and the chemistry keeps poisoning people. So the honest summary of MCH as a compound is: a well-characterised, stage-selective REM-promoting signal, with no peripheral route to its receptor, whose predictable effects in a person would be more REM sleep, more eating and less energy expenditure. Two of those three are things nobody wants.

The first thing that goes wrong is that nothing happens, and it is the most likely outcome. MCHR1 is a central receptor. Peripherally administered MCH does not usefully reach it. Every finding that makes this compound sound interesting came from a cannula in a ventricle or a fibre-optic in the hypothalamus. Injecting MCH subcutaneously and expecting more REM sleep is expecting a molecule to cross a barrier it does not cross. The second is that something does happen and it is the metabolic arm rather than the sleep arm. Peripheral MCH receptors and peripheral MCH biology exist, and the most reproducible effect of MCH in animals by a wide margin is increased food intake with reduced energy expenditure. If any of this translates, the effect a person would actually get is hunger and weight gain. That is the opposite of what almost anyone buying it wants. The third is the direction of the whole field. Twenty years of pharmaceutical investment in this target has been spent trying to block MCH, not supply it, because blocking it is the useful direction for the most common disease it touches. When the entire industry is working on an antagonist and the grey market is selling the agonist, the grey market is not ahead of the industry. The fourth is the rodent problem, which is subtle and important. Humans express MCHR2; rodents do not. The sleep findings that give MCH its reputation were generated in animals missing half the human receptor system. Nobody knows what MCHR2 contributes to the sleep phenotype in a human because there is no animal in which to ask the question cheaply. This is not a hypothetical concern - it is the documented reason multiple MCH programmes failed to translate. The fifth is practical. MCH is disulfide-cyclised, and the ring formed by Cys7-Cys16 is required for receptor activation. A peptide whose disulfide has been reduced or scrambled is inactive, and standard vendor certificates of analysis - mass spectrometry and HPLC purity - do not reliably detect either. Reducing agents, repeated freeze-thaw and prolonged storage in solution all degrade it in ways you cannot see. And the honest framing: MCH is not a compound with a bad risk-benefit ratio. It is a compound with no established benefit, a predictable and unwanted metabolic effect, no route to its target, and no human exposure. It belongs in the section of this site labelled 'targets worth understanding', not the section labelled 'things to buy'.

• MCH receptor 1 (MCHR1 / GPR24) — Sub-nanomolar to low nanomolar affinity for MCH; a specific Kd was not resolved to a primary source in this session

  The principal MCH receptor. Dual Gi/Go and Gq coupling - lowers cAMP while raising intracellular calcium. Densely expressed in nucleus accumbens shell, hypothalamus, hippocampus and cortex. Mediates the orexigenic effect, the reduction in energy expenditure, and the REM-promoting effect. The target of every failed anti-obesity antagonist programme.

• MCH receptor 2 (MCHR2 / GPR145) — Binds MCH; pharmacology less well characterised than MCHR1

  Gq-coupled. Present and functional in humans, non-human primates, ferrets and dogs; absent as a functional receptor in rodents. This species difference is the single biggest reason rodent MCH pharmacology has failed to translate, and it means half the human MCH receptor system is invisible in the animal models that generated the sleep findings.

• REM sleep-generating circuitry (lateral hypothalamic MCH neurons) — Circuit-level, not a binding site

  MCH neurons are near-silent in wake, active in non-REM and maximally active in REM. Optogenetic stimulation increases sleep (Konadhode et al., J Neurosci 2013); central MCH infusion increases paradoxical sleep (Verret et al., BMC Neurosci 2003); ablation reduces REM. One of the few genuinely stage-selective signals in sleep neuroscience.

• Nucleus accumbens feeding and reward circuitry — Downstream of MCHR1

  MCHR1 in the accumbens shell links MCH to food reward and motivated feeding, not just homeostatic hunger. Part of why MCH administration produces a marked and reproducible increase in food intake in animals.

• Energy expenditure regulation — Downstream, multiple sites

  MCH lowers energy expenditure alongside raising intake, so chronic central administration produces obesity in rodents while MCH-deficient animals are lean. Reviewed comprehensively in Al-Massadi et al., Nat Rev Endocrinol 2021.

• No human trial of melanin-concentrating hormone as an agonist therapy exists None

  Stated explicitly because it is the most important fact about this compound. MCH has never been administered to a human in a published, controlled protocol for any indication. All clinical development at this target has been on the antagonist side for obesity, and those programmes have repeatedly stopped on cardiac and hepatic safety grounds rather than for lack of effect.

• Verret, Goutagny, Fort, Luppi et al. - a role of melanin-concentrating hormone producing neurons in the central regulation of paradoxical sleep (BMC Neuroscience 2003) Preclinical, rat · 2003

  Activation of MCH neurons during paradoxical (REM) sleep, and increased paradoxical sleep after intracerebroventricular MCH. The founding observation linking MCH specifically to REM.

• Konadhode, Pelluru, Blanco-Centurion, Shiromani et al. - optogenetic stimulation of MCH neurons increases sleep (Journal of Neuroscience 2013) Preclinical, mouse · 2013

  Direct optogenetic activation of MCH neurons increased sleep. The causal complement to the correlational firing-pattern work, and the study that made the MCH-REM link difficult to argue with.

In humans: unknown, entirely. No human has received MCH in a published protocol. In rodents, after intracerebroventricular administration: feeding behaviour changes within minutes, and sleep state changes are evident within the same recording session. Effects are acute and short-lived, consistent with rapid peptide degradation. With chronic central infusion in rodents: the metabolic phenotype - hyperphagia, reduced energy expenditure, weight gain - develops over days to weeks and produces frank obesity. With optogenetic stimulation of MCH neurons: sleep changes are immediate and time-locked to the stimulation, which is exactly what makes the optogenetic evidence stronger than the pharmacological evidence. There is no peripheral onset timeline because there is no demonstrated peripheral effect on sleep to time.

There is no human protocol and therefore no stack. The mechanistic relationships are still worth stating because they explain why the compound sits in this class at all. MCH and orexin are the cleanest functional opposition on this site. Their neurons are physically interleaved in the lateral hypothalamus and fire in near-mirror-image patterns: orexin in wake, MCH in REM. Orexin promotes wake and suppresses REM; MCH promotes REM and suppresses nothing about wake except by competition. Running both would be an attempt to hold the lateral hypothalamus in two states at once. With DSIP: both are marketed on sleep-deepening grounds and they target different stages. DSIP's human data concerns sleep continuity and slow-wave sleep; MCH's animal data concerns REM. There is no combination data and no mechanistic reason to expect additivity. With a GLP-1 agonist or anything else being used for weight: directly self-defeating. MCH is one of the more powerful orexigenic signals in the brain and it lowers energy expenditure at the same time. Taking it alongside a compound whose entire purpose is appetite suppression is paying for both sides of the same argument. With any REM-suppressing drug - SSRIs, SNRIs, venlafaxine in particular, or alcohol: an MCH agonist would be pushing REM pressure up against a drug pushing it down, and REM rebound phenomena are unpleasant. Purely theoretical, since nobody has done it. The compound that people in this space should actually be looking at, if the goal is understanding MCH rather than taking it, is an MCHR1 antagonist - and those are the ones that keep failing on safety.

Against orexin-A: the two are mirror images and orexin-A is by far the better developed of the pair. Orexin-A has two controlled human studies, a validated intranasal rationale, primate route-comparison data, and a small-molecule successor with a New England Journal of Medicine result. MCH has rodent optogenetics and no human exposure at all. Both are lateral hypothalamic peptides with a delivery problem; only one has been given to people. Against DSIP: DSIP has human polysomnography going back to 1981, however small and old. MCH has none. If the goal is more or better sleep and you insist on a peptide, DSIP is the only one in this class with human sleep-laboratory data supporting the actual use case. Against nothing: this is the comparison that matters. For a person who wants more REM sleep, the interventions with real evidence are getting enough total sleep, going to bed at a consistent time, stopping alcohol (which suppresses REM sharply in the first half of the night), and reviewing any SSRI or SNRI, which are potent REM suppressors. All four are free. None of them require a peptide that cannot reach its receptor. Against MCHR1 antagonists: worth noting that the interesting drug at this target points the other way. If MCH biology ever produces an approved medicine it will be an antagonist for obesity, assuming somebody solves the cardiac and hepatic safety problems that have stopped every attempt so far. As neuroscience rather than as a product: MCH is one of the more elegant discoveries in sleep biology. A neuronal population that fires almost exclusively during REM, whose stimulation increases sleep and whose ablation reduces REM, is about as clean a stage-specific signal as the field has found. That is genuinely worth knowing. It is not a reason to buy a vial.

Deliberately null. MCH is a research reagent sold in milligram quantities for laboratory use. There is no human protocol, no established dose and no validated route, so any monthly figure would require inventing a protocol. Disulfide-cyclised 19-residue peptides are moderately expensive to synthesise correctly, but that is a per-milligram catalogue fact, not a cost of use.

• ?MCH has never been administered to a human in a published protocol. There is no human dose, route, safety data or pharmacokinetics.
• ?No pharmacokinetic data exists in any species for peripherally administered MCH that I could resolve.
• ?Specific binding affinity values (Kd or Ki) for MCH at MCHR1 and MCHR2 were not resolved to a primary source in this session.
• ?Whether peripherally or intranasally administered MCH reaches central MCHR1 at any dose is unknown and appears untested.
• ?The relative contribution of MCHR2 to the human sleep phenotype is completely unknown, because the receptor is absent in the rodents in which all the sleep work was done.
• ?The specific MCHR1 antagonist programmes that were discontinued, and the precise safety findings that stopped each of them, were not individually verified in this session. The general pattern of cardiac and hepatic safety terminations is described in the Al-Massadi 2021 review, which I confirmed exists but did not read in full.
• ?Whether the rodent REM findings would translate to a human at all is unknown, and translation has already failed repeatedly on the metabolic side of this same target.
• ?The 2387 Da molecular weight in the Core record was not independently verified against an analytical source, though the sequence and disulfide position were confirmed via UniProt P20382.
• ?Disulfide integrity in commercially supplied MCH cannot be assessed from a standard certificate of analysis, and the cyclic core is required for activity.

• A role of melanin-concentrating hormone producing neurons in the central regulation of paradoxical sleep Verret L, Goutagny R, Fort P, Cagnon L, Salvert D, Leger L, Boissard R, Salin P, Peyron C, Luppi PH, BMC Neuroscience, 2003 · PMID 12964948

  BMC Neurosci 4:19. Open access. The paper that established MCH neurons as REM-active and central MCH as REM-promoting.

• Optogenetic stimulation of MCH neurons increases sleep Konadhode RR, Pelluru D, Blanco-Centurion C, Zayachkivsky A, Liu M, Uhde T, Glen WB Jr, van den Pol AN, Mulholland PJ, Shiromani PJ, Journal of Neuroscience, 2013 · PMID 23785141

  J Neurosci 33(25):10257-63. The causal optogenetic demonstration. Read alongside Verret 2003 for the full argument.

• Multifaceted actions of melanin-concentrating hormone on mammalian energy homeostasis Al-Massadi O, Dieguez C, Schneeberger M, Lopez M, Schwaninger M, Prevot V, Nogueiras R, Nature Reviews Endocrinology, 2021 · PMID 34608277

  Nat Rev Endocrinol 17(12):745-755. The current authoritative review of MCH in energy homeostasis, including the MCHR1 antagonist development history and the MCHR2 species problem.

• Pro-melanin-concentrating hormone precursor, UniProtKB entry P20382 UniProt Consortium, UniProtKB

  Source for the 19-residue mature MCH sequence, its position in the precursor at residues 147-165, and the Cys153-Cys162 disulfide bond given in this record. Resolved directly in this session.