David Sinclair posted:

On November 4th, 2022, the US Food and Drug Administration (FDA) published a letter regarding the marketing and sales of nicotinamide mononucleotide (NMN) as a supplement to boost NAD levels.
I am deeply grateful for your patience while I’ve gathered information to share with you about the impact of this decision. I know many of you are worried about what this means about the safety of NMN, and the possible limitations to the availability of NMN supplements.
While NAD boosters such as NMN have become popular as supplements, in part because of my research, I am not, and have not, been involved as an owner, cofounder, investor, shareholder, marketer, spokesperson or sponsor of any company that sells NAD boosters as supplements.
The FDA’s decision was preceded by a letter from MetroBiotech, a company I co-founded but do not manage or control, pointing out that the company had begun clinical trials with a special, crystalline form of NMN that is stable and made under FDA drug standards.
The FDA’s letter is based on the Food, Drug & Cosmetic Act, which states “...the term 'dietary supplement' does not include an article authorized for investigation as a new drug...” In other words, if a clinical trial of a substance has been initiated, it cannot be classified as a dietary supplement.
In its action, the FDA is in line with its own regulations, which do not allow for the authorization of a substance to be classified as a dietary supplement if it has already been cleared by the FDA for clinical trials.
I remain enthusiastic about the science of NAD boosters and their promise of improving human health. Furthering that science, and the prospect of cellular age reversal, continues to be my life’s work, which includes helping other researchers perform clinical trials to address medical conditions like glaucoma, kidney failure, frailty, and rare diseases such as Freidreich’s ataxia.
Human clinical trials conducted by MetroBiotech on NMN have produced promising results, some of which are published (Pencina et al., 2022) and some are under peer review. https://academic.oup.com/biomedgerontology/advance-article-abstract/doi/10.1093/gerona/glac049/6532484?redirectedFrom=fulltext&login=false
The important work of bringing NMN to market as an FDA-approved medication is in the best interest of the tens of millions of people who suffer from and will succumb to aging-related diseases.
The FDA standards for testing, quality control, and efficacy are among the most responsible consumer protection regulations in the world. All consumers deserve the trust, safety and reliability that comes with appropriate regulation and oversight.
Whether NMN will remain on the supplement market is not yet known but another molecule, N-acetylcysteine (NAC), which is sold both as a supplement and prescribed as a medicine for acetaminophen overdosing and as a mucolytic agent in respiratory diseases, fell under the same law and remains on the US supplement market.

Thank you for your patience and please rest assured that advancing the health and well-being of everyone who could potentially benefit from scientific curiosity and discovery will continue to be my highest priority