Ultimate Summer Stack across Europe

Ultimate Summer Stack is our largest set: RETATRUTIDE 32, MELANOTAN II 20 (in stock and shipping now), GHK-CU 50 and NAD+ 1000 in one order. The name is a marketing name; the set puts the pens you read about under weight loss and skin next to the coenzyme. No published study has tested any two of these together, let alone all four.

Four compounds at four different stages

Pen	Strongest published human evidence	Authorisation
RETATRUTIDE 32	Phase 2 randomised trial, 48 weeks	None anywhere
MELANOTAN II 20	Case reports only	None in the EU or UK
GHK-CU 50	Topical and wound-gel studies, not injectable	None as a medicine
NAD+ 1000	Trials of oral precursors, not injected NAD+	None as a medicine for this use

Retatrutide: a triple agonist with Phase 2 data

Retatrutide activates the GIP, GLP-1 and glucagon receptors; the glucagon activity separates it from tirzepatide and semaglutide (what is retatrutide?). The trial behind the interest is Jastreboff AM et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity, a Phase 2 Trial. N Engl J Med 2023. PMID 37366315: a 48-week double-blind, randomised, placebo-controlled study in adults with a body-mass index of 30 or higher, or 27 to under 30 with a weight-related condition, reporting body-weight reductions of around 24% at the highest dose. Gastrointestinal adverse events were the most common, as across the incretin class, which is why the trial titrated upward slowly. A Phase 2 trial informs dose selection; it is not the basis on which a medicine is authorised. Retatrutide’s Phase 3 programme is not complete. Trial means describe supervised, titrated groups, not a forecast for you; we do not publish a dosing schedule.

Melanotan II: non-selective, and thinly evidenced

Melanotan II is a cyclic analogue of alpha-melanocyte-stimulating hormone. Pigmentation runs through MC1R, but it also activates MC3R and MC4R, central receptors governing appetite and sexual function, so its reported effects extend well beyond skin (what is Melanotan II?). There is no published human dose-ranging trial. The peer-reviewed human record is largely case reports, several describing serious harm: systemic toxicity with rhabdomyolysis after injection (Nelson ME et al. Melanotan II injection resulting in systemic toxicity and rhabdomyolysis. Clin Toxicol 2012. PMID 23121206) and melanoma diagnosed in people who had been injecting it (Hjuler KF et al. Melanoma associated with the use of melanotan-II. Dermatology 2014. PMID 24355990). Case reports cannot establish causation in either direction; they do establish that serious events have been documented and no controlled evidence of benefit has. Its regulatory position is distinct within our catalogue: it holds no marketing authorisation in the EU or the UK, and the MHRA states that it has repeatedly removed melanotan tanning products from the UK market over more than ten years (Medicines and Healthcare products Regulatory Agency. FOI 21/1237: Yellow Card reports for melanotan II products, 2011–2021. 2021.). Because melanocortin signalling stimulates the cell type melanoma arises from, discuss existing moles and skin-cancer risk with a qualified clinician before deciding about this pen.

GHK-Cu: a well-described complex whose human data is topical

GHK-Cu is a defined 1:1 complex of the tripeptide glycyl-L-histidyl-L-lysine with copper(II) (what is GHK-Cu?). Its best-characterised finding is collagen synthesis in fibroblast culture, with stimulation beginning between 10⁻¹² and 10⁻¹¹ M and peaking around 10⁻⁹ M (Maquart FX et al. Stimulation of collagen synthesis in fibroblast cultures by the tripeptide-copper complex GHK-Cu. FEBS Lett 1988. PMID 3169264). That is a cell-culture finding. Human work concerned topical skincare programmes and a specific wound gel (Mulder GD et al. Enhanced healing of ulcers in patients with diabetes by topical treatment with glycyl-l-histidyl-l-lysine copper. Wound Repair Regen 1994. PMID 17147644); because the complex’s behaviour depends on pH, concentration and counter-ions, a serum, a wound gel and an injectable solution are three different products, and those results do not transfer to this pen.

NAD+: the biomarker moves, the outcomes are mixed

NAD+ is a coenzyme, not a peptide (what is NAD+?), and its human trial literature is mostly about the oral precursors nicotinamide riboside and nicotinamide mononucleotide. A long-term randomised, placebo-controlled trial of nicotinamide riboside chloride in healthy overweight adults addressed safety and metabolism (Conze D et al. Safety and Metabolism of Long-term Administration of NIAGEN (Nicotinamide Riboside Chloride) in a Randomized, Double-Blind, Placebo-controlled Clinical Trial of Healthy Overweight Adults. Sci Rep 2019. PMID 31278280), and precursor supplementation raised blood NAD+. A meta-analysis of randomised NMN trials at 250 to 2000 mg per day found no significant effect on fasting glucose, fasting insulin, glycated haemoglobin or lipids (Chen F et al. Effects of nicotinamide mononucleotide on glucose and lipid metabolism in adults. Curr Diab Rep 2024. PMID 39531138). Raising the level is reliable; a clinical benefit is not established; none of that work used injected NAD+.

Where the evidence for the set stops, and who chooses it

Nothing is known about how these four compounds behave together, because nobody has studied it; the set is a purchasing convenience, not a tested combination. Nothing here is co-formulated: every pen is the item sold on its own product page, and combining them is not something we give instructions on. What is documented is the pen: an independent laboratory tests each batch for identity, purity and sterility, and the certificate for your lot is one QR scan away, or in the index at /coa. Why none is authorised is explained at why these compounds are not EMA-authorised.

You choose this set after reading the weight-loss and skin pages and wanting all four pens in one order. If only the incretin and the coenzyme are relevant, Advanced Lean Stack is retatrutide and NAD+; if only the skin-listed peptide and the coenzyme are, Vitality Stack is NAD+ and GHK-Cu. Melanotan II is the pen to decide about on its own, on the case-report record and regulatory position above, not because it happens to be in the set.