Safety Assessment of High-Purity, Synthetic Nicotinamide Riboside (NR-E) in a 90-Day Repeated Dose Oral Toxicity Study, With a 28-Day Recovery Arm

Abstract

Nicotinamide riboside (NR) is a naturally occurring form of vitamin B3 shown to preferentially elevate the nicotinamide adenine dinucleotide (NAD+) metabolome compared to other vitamin B3 forms (nicotinic acid and nicotinamide). Although daily requirements of vitamin B3 are typically met through the diet, recent studies have shown that additional supplementation with NR may be an effective method to counter the age-related decline in NAD+ levels as NR bypasses the rate-limiting step in NAD+ biosynthesis. Furthermore, pharmaceutical applications of NR for age-related disorders have been proposed. In this study, the safety of a high-purity, nature-identical, synthetic NR (NR-E), manufactured under the guidelines of good manufacturing practices for dietary supplements (21 CFR 111) as well as for drugs (21 CFR 210), was investigated in a 90-day oral toxicity study in Sprague Dawley rats at 300, 500, and 1,200 mg/kg/d. There were no mortality or clinical observations attributable to the test substance at any dose. A small but statistically significant decrease in body weight was observed at day 92 in the 1,200 mg/kg/d NR-treated male rats only. In contrast to a previously published safety assessment using a different synthetic NR (NIAGEN), whose no-observed-adverse-effect-level (NOAEL) was reported to be 300 mg/kg/d, there were no adverse changes in clinical pathology parameters and no notable macroscopic or microscopic findings or treatment-related effects at similar doses. In the current study, the NOAEL for systemic toxicity of NR-E in Sprague-Dawley rats was conservatively determined to be 500 mg/kg/d for males (solely based on body weight) and 1,200 mg/kg/d for females.

Extension of use of nicotinamide riboside chloride as a novel food pursuant to Regulation (EU) 2015/2283

“…The Panel considers that the study by Marinescu et al. ( 2020 ) shows similar findings to the study conducted with the NF (Bhoite et al., 2015 ; Conze et al., 2016 ), such as decreased body weights, increased relative liver and kidney weights and effects on the haematopoietic system. In light of this, the Panel reconsidered the validity of its conclusions regarding the adversity of the effect on body weight observed in the Conze study.…”

“…As part of the request for extension of uses, the applicant provided an additional GLP‐, OECD‐compliant 90‐day subchronic rat toxicity study to the Panel on NRC produced by another company (Marinescu et al., 2020 ). The test substance used in the study is described as ‘a synthetic, nature‐identical nicotinamide riboside chloride (CAS #23111‐00‐4) designated as NR‐E manufactured using a proprietary process under the guidelines of good manufacturing practice (GMP) 21 CFR 111/210 (C.F.R.…”

“…The Panel considers that the study from Marinescu et al. ( 2020 ) is relevant to the safety assessment of the NF.…”

“…In this study (Marinescu et al., 2020 ), Sprague Dawley rats were exposed to 0, 300, 500 or 1,200 mg/kg bw per day of synthetic NRC by daily oral gavage (10 per sex for each dose group) for 90 days, followed by a 28‐day recovery for five rats per sex for each dose group.…”

“…The applicant conducted a benchmark dose (BMD) modelling based on combined data from the two above‐described 90‐day subchronic toxicity studies (Conze et al., 2016 ; Marinescu et al., 2020 ), using male body weight as an endpoint. The Panel notes the difference in body weights of the rats involved (i.e.…”