Somewhere around 2024, NAD+ escaped the longevity forums. The coenzyme that powers cellular energy metabolism, and that declines with age, had spent a decade as a supplement-world obsession — precursors in capsules, infusions in Los Angeles clinics — and it was only a matter of time before a skincare brand tried to bottle the idea. Dr. Dennis Gross, which has spent 26 years riding each year's ingredient conversation from vitamin C to ferulic retinol to hyaluronic infusions, has done it with a serum launched on 21 August 2026 and an acronym: G.N.A., for glutathione, niacinamide and adenosine, described as precursors that ignite the skin's energy cycle. Add 'collagen amino acids' — glycine, proline, alanine, the building blocks of collagen — and you have a serum whose pitch is metabolic rather than cosmetic: feed the skin, fuel the skin, let the skin do the rest. It is a clever story. The question is how much of the ingredient list believes it.
Start with the acronym, one letter at a time. N is niacinamide, and here the story holds: niacinamide is literally the dietary precursor the skin converts to NAD+, and it sits fifth on the list, behind water and three humectants, which is where a working dose lives. It also happens to be one of the most versatile ingredients in skincare regardless of any energy narrative — barrier support, pore and tone improvement, a slowing of pigment transfer — and most of what a buyer will notice in the first month of this serum is niacinamide doing niacinamide things. A is adenosine, seventh, an unusually high position for an ingredient most brands bury near the preservative, and adenosine has real if modest clinical evidence: small controlled trials have shown improvement in crow's feet and glabellar lines with topical adenosine over eight weeks. Inosine, its nucleoside cousin, appears further down. If any part of the 'skin energy' framing has legs, it is this one. G is glutathione, sixth, and here the story strains. Glutathione is a genuinely important intracellular antioxidant — the 'master antioxidant' of supplement copy — but it is a water-soluble tripeptide that penetrates intact skin poorly and oxidises readily in a water-based serum, and the clinical literature for skin consists of small oral and lozenge studies with modest pigmentation findings. Pairing it with acetyl cysteine, one of its precursors, is a thoughtful touch; it does not turn a poorly delivered molecule into a delivered one.
Then the collagen amino acids. Fourteen free amino acids run from ninth position downward, led by glycine, proline and alanine, joined by dipalmitoyl hydroxyproline, a lipidised form of the hydroxyproline that gives collagen its stability. The framing is that these are the raw materials skin needs to build collagen. The biochemistry says fibroblasts are not short of raw materials — amino acids arrive constantly from the bloodstream — and that collagen synthesis responds to signals, not to supply. Retinoids signal. Peptides signal. Injury signals. A surface top-up of glycine does not. What free amino acids do very well on skin is hold water; they are components of the skin's own natural moisturising factor, and a serum this rich in them is an excellent humectant, which is a real and immediate benefit. It is simply a different benefit from the one printed on the box.
And this is the pattern with the BioRejuvenation Serum: underneath the new narrative sits a very conventional, very well-constructed firming serum. Three signal peptides — copper tripeptide-1, the best studied of the family, plus palmitoyl pentapeptide-4 and palmitoyl tripeptide-28 — sit just after the amino acids and ahead of the antioxidant extracts, which is a respectable position for peptides in a 30 mL bottle. Superoxide dismutase heads an antioxidant roster that runs to ectoin, amla, green tea, resveratrol, ubiquinone, ellagic and gallic acids and two forms of vitamin C at trace levels: the kitchen-sink construction that is this brand's house style, and that delivers breadth rather than depth. Lactobionic acid, four hyaluronate weights, squalane, pomegranate sterols and a little shea handle hydration and slip. Trace glycolic, mandelic and retinol appear far down, too low to act and too low to sting. It is a lot of ingredients. Most of them are good ones. None of them is new.
In use, the serum is easy to like. It is a light, translucent gel that spreads thin over face and neck in two or three pumps, sinks in within a minute, and leaves a soft satin film that vanishes under moisturizer. Skin looks a shade brighter and feels smoother from the first week — humectants and niacinamide — and the texture improvement builds through the first month. The tightening is subtler and slower: around week four some users describe a faint taut feeling along the jaw, which is plausible from the peptides and adenosine and also plausible from wanting it to be so. The brand's own numbers come from two in-house studies of 50 participants, at 8 and 12 weeks, reporting that 84% saw visibly firmer, tighter skin and 90% said their skin felt firmer. Those are perception figures — what participants said when asked — from studies the brand designed and paid for, and a serum four weeks old has no independent data to set beside them. Fifty people is a respectable panel for an in-house consumer study. It is not a clinical trial, and a jawline that has begun to soften will not be re-sculpted by any serum, this one included.
Two formulation choices sit uneasily with the clinical positioning. The first is fragrance: lavender and jasmine oils, clove extract and linalool close the list and give the serum a soft spa-floral scent that fades in minutes but is unmistakably there, and that a fragrance-sensitive or rosacea-prone buyer at $89 has every right to resent. The second is glutaral — glutaraldehyde — as a preservative, a legitimate cosmetic ingredient at trace levels but a well-known contact sensitiser in occupational settings, and an unusual thing to find in a serum sold on dermatologist credentials. Neither is a dealbreaker for most skin. Both are choices a brand founded by a dermatologist could have made differently.
Which leaves the price. Eighty-nine dollars for 30 mL, used at two to three pumps daily over face and neck, is a bottle every six to eight weeks and a running cost that puts this in the top tier of Sephora serums. Dr. Dennis Gross is an established brand with a quarter-century of competent formulation behind it, and the ingredient list justifies a premium: high-position niacinamide and adenosine, real peptides, a serious antioxidant load. What the price also buys is a story that the evidence does not yet support, from a product that has existed for one month, tested only by the people selling it. That is the hype-aware caveat, and it is a caveat, not a verdict — the serum will do good things for most skin. It just does them for the reasons firming serums have always done them, and calling those reasons 'cellular energy' does not make them cost more to produce.
For the buyer with normal, combination or dry skin, no fragrance sensitivity, a budget that does not flinch at $89 a bottle, and realistic expectations — smoother, brighter, perhaps a touch firmer over three months — this is a well-made serum that will deliver. For anyone with reactive skin, anyone pregnant, anyone hoping a serum will lift a jowl, or anyone who would rather wait for a second opinion than be the second opinion, the sensible move is to let the formula age for a year and see whether the 84% survives contact with the public.
