Dihexa

Dihexa is a small lab-made molecule ^[17]. Scientists built it from a short piece of angiotensin IV, a fragment of a hormone ^[8]. They changed that piece so it would last longer in the body and pass from the blood into the brain ^[8]. Its full chemical name is N-hexanoic-Tyr-Ile-(6)-amino hexanoic amide, and one study calls it PNB-0408 ^[13].

Its makers tested it as a possible treatment for memory loss, such as in Alzheimer's disease ^{[8] [17]}. FDA calls the substance Dihexa acetate ^[1]. FDA has found no data on any person given a drug containing it ^[1].

Dihexa is in limbo: FDA lists Dihexa acetate among the Category 2 substances whose nominations were withdrawn, and it has not added it to Category 1 ^{[1] [2]}. That is not approval, and it does not make compounding lawful. Checked 25 October 2026.

Category 2 is FDA's list of substances that may raise significant safety risks. Category 1 is the list of substances under review that pharmacies may use while FDA decides ^[3]. In April 2026, the groups that nominated Dihexa acetate withdrew, so it came off Category 2 ^{[1] [5]}. Taking a substance off Category 2 does not by itself let pharmacies use it ^{[5] [6]}.

FDA says its Pharmacy Compounding Advisory Committee will discuss Dihexa acetate at a meeting before the end of February 2027 ^{[4] [7]}. FDA has posted no date for that meeting and no review of Dihexa for it ^[4]. No public comment docket was open for that meeting when a trade group reported on it ^[18]. The committee gives advice only ^[5]. FDA decides by writing a rule ^[6].

Until FDA acts, a pharmacy may not use Dihexa under the federal compounding law ^{[3] [6]}.

The evidence grade is animal-only: every study we found tested Dihexa in rats, mice, fish or cells ^[16]. FDA found no data on any person given Dihexa ^[1]. A result in an animal does not show what happens in people.

Memory: in a 2013 study, Dihexa helped rats with memory problems find their way in a water maze ^[8]. It also helped aged rats with memory loss ^[8]. In 2021, the journal posted a notice of concern about that study ^[9]. In a 2021 study, Dihexa helped mice bred to have an Alzheimer's-like disease do better in the same maze ^[12]. A 2018 review of animal studies found that angiotensin IV and related molecules, Dihexa among them, helped memory in eight of nine studies of memory loss ^[16].

How it acts: a 2014 animal study proposed that Dihexa acts by boosting a growth signal called HGF ^[10]. The journal retracted that study in 2025 ^[11]. A 2015 review by two of the scientists who made Dihexa describes it the same way ^[17]. That review came out before the retraction. Both of its authors also list a biotech company among their workplaces ^[17].

Other uses: in rats with Huntington's-like damage, Dihexa did not protect them ^[13]. In rats with a repaired leg nerve, walking improved when stem cells and Dihexa were put into a leg muscle ^[14]. In young zebrafish, Dihexa protected hair cells like those of the inner ear from two antibiotics that can harm hearing ^[15].

There is no legal way to get Dihexa in the US today ^{[1] [2]}. FDA has found no data on any person given a drug containing it ^[1]. A pharmacy may use a substance with no official quality standard only if it is in an approved drug or on the federal list ^[3]. Dihexa is not on that list, and FDA is still deciding whether to add it ^{[2] [4]}.

Any open trial would appear in the trials block below, with the date the registry was last checked.

Groups once asked FDA to let pharmacies make Dihexa acetate, then withdrew that request ^{[1] [3]}. No pharmacy may lawfully make it now ^{[3] [6]}.

We found no federal warning letter, import alert or court record that names Dihexa. So this page does not describe websites, clinics or other sellers for Dihexa. FDA has no data on what Dihexa does in people, by any route ^[1].