5-Amino-1MQ History: From a Vitamin B3 Enzyme to a Quinolinium Inhibitor

5-Amino-1MQ is not a peptide, and it was not found in nature. It is a small synthetic molecule, 5-amino-1-methylquinolinium, that was designed to block one enzyme: nicotinamide N-methyltransferase (NNMT). So its history is really the history of that enzyme, and of how a "vitamin B3 clearance" enzyme came to be studied as a metabolic research target. The [5-Amino-1MQ research overview](/research/5-amino-1mq) covers what the compound is. This article traces how it got there.

1951: an enzyme that methylates vitamin B3

The enzyme was first described by Giulio Cantoni in 1951. In the *Journal of Biological Chemistry*, he reported the methylation of nicotinamide by a soluble enzyme system from rat liver [1]. The reaction, now catalogued as EC 2.1.1.1, transfers a methyl group from S-adenosyl-L-methionine (SAM) to nicotinamide, producing S-adenosyl-L-homocysteine and 1-methylnicotinamide (1-MNA) [1].

For decades this was read mainly as a disposal step: a way for the liver to tag excess nicotinamide (a form of vitamin B3) for excretion.

1990–1994: the human enzyme

Work on the human enzyme came largely from Richard Weinshilboum's pharmacogenetics group.

• Measuring it (1990). Rini and colleagues developed an ion-pairing radiochemical assay for human liver NNMT and described its biochemical properties and variation between individuals [2].
• Cloning it (1994). Aksoy, Szumlanski and Weinshilboum reported the cloning and expression of a human liver NNMT cDNA [3]. The encoded protein is 264 amino acids long, and the gene sits on chromosome 11 (11q23) [3].

At this point NNMT was still mainly a drug-metabolism enzyme. Nobody was trying to block it.

2014: NNMT becomes a metabolic research target

The turn came in 2014. Kraus and colleagues, in Barbara Kahn's group, reported in *Nature* that NNMT expression was higher in the white adipose tissue and liver of obese and diabetic mice [4]. Knocking down Nnmt in fat and liver protected the mice against diet-induced obesity, which the authors linked to increased cellular energy expenditure [4]. Reducing NNMT raised adipose SAM and NAD+ levels and increased polyamine flux [4].

That paper reframed NNMT as an enzyme that sits where methylation (SAM) and NAD+ metabolism meet. A 2017 review in *Trends in Endocrinology & Metabolism* summed up the shift in its title: "more than a vitamin B3 clearance enzyme" [5]. The [5-Amino-1MQ mechanism of action](/blog/5-amino-1mq-mechanism-of-action) spoke covers that biology in detail.

The 2014 study used genetic knockdown, not a drug. The next question was whether a small molecule could do something similar.

2017: building an inhibitor around the quinolinium scaffold

The small-molecule work came from Stanley Watowich and Harshini Neelakantan's group at the University of Texas Medical Branch (UTMB) in Galveston.

• Structure-activity study. In 2017 the group published a structure-activity relationship study in the *Journal of Medicinal Chemistry* [6]. They screened N-methylated quinolinium, isoquinolinium, pyridinium and benzimidazolium/benzothiazolium analogues and reported inhibitors whose activity spanned more than 1,000-fold. Quinoliniums emerged as the most promising scaffold, with NNMT inhibition in the low-micromolar range (IC50 around 1 µM). Docking into the enzyme's nicotinamide-binding site correlated well with the measured IC50 values [6].
• The patent. The same researchers filed patent protection, with a priority date of March 30, 2017 [7]. The resulting US patent 11,401,243, assigned to the University of Texas System and granted in August 2022, names compound "1j (5-amino-1-methylquinolinium)", abbreviated 5-amino-1MQ, and lists its IC50 against NNMT as 1.2 ± 0.1 µM [7].

This is where the name enters the record. 5-Amino-1MQ is one member of a designed series, chosen for its activity and its ability to get into cells.

2018: the first diet-induced obesity study

A 2018 paper in *Biochemical Pharmacology* tested the series further [8]. The authors reported that methylquinolinium compounds with primary-amine substitutions showed high membrane permeability. In cultured adipocytes, the inhibitors reduced intracellular 1-MNA, increased NAD+ and SAM, and suppressed lipogenesis [8]. In high-fat-diet obese mice, systemic treatment with a potent inhibitor from the series was associated with reduced body weight and white adipose mass, smaller adipocytes and lower plasma total cholesterol. The authors reported no change in total food intake and no observable adverse effects [8].

A parallel track: other NNMT inhibitors

UTMB was not the only group working on the target. In 2018, Kannt and colleagues described JBSNF-000088, a nicotinamide analog that inhibited NNMT [9]. In high-fat-diet obese mice it was associated with reduced body weight, improved insulin sensitivity and normalised glucose tolerance. The effects were not seen in NNMT-knockout mice, which the authors took as evidence of specificity [9]. It is a different molecule from 5-amino-1MQ, and its results should not be attributed to it.

2019–2024: aged muscle, diet and exercise models

The UTMB group then extended its NNMT inhibitor work beyond obesity. Several of the later papers identify the compound only as "NNMTi" in their abstracts, so we note where 5-amino-1MQ is named.

• Aged muscle (2019). In 24-month-old mice with a barium-chloride injury to the tibialis anterior muscle, NNMTi treatment (5 or 10 mg/kg) was associated with increased muscle stem-cell proliferation and fusion, roughly twofold larger myofiber cross-sectional area and about 70% higher peak torque than controls [10].
• Diet switch (2021). In obese mice switched to a lean diet, adding NNMTi was associated with faster and greater body-weight and fat loss than the diet switch alone, and with body composition and liver adiposity measures similar to lean-diet controls [11].
• Microbiome (2022). This study names the inhibitor as 5-amino-1-methylquinolinium (5A-1MQ). It was given at 32 mg/kg by subcutaneous injection, a route the authors chose because the compound has poor oral bioavailability in mice. They used male C57BL/6J mice, 6 to 8 per group [12]. Combined with a reduced-calorie diet, treatment was associated with a distinct gut microbiome profile, including higher Lactobacillus. The authors noted limited statistical power and that the design could not establish causation [12].
• Exercise (2024). In aged mice treated from 22 to 24 months of age, NNMTi-treated sedentary mice showed about 40% greater grip strength than sedentary controls. Exercise alone was associated with about a 20% increase, and the combination with about 60% [13].

The 2022 paper also records a commercial step. Its competing-interests statement discloses that Watowich founded Ridgeline Therapeutics and that co-authors were paid employees of the company [12].

State of the literature

The history explains both why 5-amino-1MQ draws research interest and why the evidence is narrower than it may look.

• The target is well established; the compound is less so. NNMT has been studied since 1951 [1], and its metabolic role is supported by genetic work in mice [4]. Evidence for 5-amino-1MQ itself is much thinner.
• One group did most of the work. Most published studies of 5-amino-1MQ come from one academic group and its spin-out company, with disclosed financial interests [12]. Independent replication is limited.
• The models are small and mostly male mice. Studies used rodents, mostly males and small groups, and several later papers name the compound only as "NNMTi" [10, 11, 13].
• Route matters. The 2022 authors gave the compound by injection because of poor oral bioavailability in mice [12].
• There are no human data. As of October 2026, we have not found a published human clinical trial of 5-amino-1MQ. Mouse findings cannot be used to predict any effect in people.

5-Amino-1MQ is not FDA-approved for any use. For the pathways studied, see the [5-Amino-1MQ mechanism of action](/blog/5-amino-1mq-mechanism-of-action) spoke. For common questions, see the [5-Amino-1MQ research FAQ](/blog/5-amino-1mq-research-faq). For how it compares with a mitochondrial peptide studied in similar models, see [5-Amino-1MQ vs MOTS-c](/blog/5-amino-1mq-vs-mots-c). For the full picture, see the [5-Amino-1MQ research overview](/research/5-amino-1mq).