The new Marini Hair has the two peptides used in Marini Lash, tetrapeptide-12 and pentapeptide-17. Hair has, as one of its key ingredients, something called spirolac (7α-Acetylthio-3-oxo-17α-pregn-4-ene-21,17-carbolactone). This turned out to be spironolactone. It is commonly taken orally as a diuretic or for treating acne. Topically it is used to treat hair loss.
It seems to work by inhibiting the production of testosterone (for this reason, it is not usually prescribed for men) and it may even bind to the hair follicle before testosterone can get there.
Unfortunately, spironolactone is linked to cancer. This is what the manufacturer says in big letters at the very top of the spec' page: "Spironolactone has been shown to be a tumorigen in chronic toxicity studies in rats. Unnecessary use of this drug should be avoided." I imagine this was a study of oral use (since that is usually how spironolactone is taken) and I don't know if the same dangers are likely with topical use. Still, the definition of "unnecessary use" probably depends on how you feel about a little thinning of the hair.
Water (Aqua), Butylene Glycol, Spirolac (7α-Acetylthio-3-oxo-17α-pregn-4-ene-21,17-carbolactone), Hydroxypropyl Starch Phosphate Ester, Steareth-100, Steareth-2, Mannan, Xanthan Gum, Diazolidinyl Urea, Methylparaben,Propylparaben, Retinol, Panthetine, Kiwi Fragrance (Parfum), Zinc PCA, Myristoyl Tetrapeptide-12, Myristoyl Pentapeptide-17, Hydrolyzed Wheat Protein, Japanese Green Tea Extract, Hydrolyzed Oat Protein, Dipotassium Glycyrrhizate, Niacinamide