(T1430-10-66) Pharmacokinetics of Nervonic Acid, a Monounsaturated Fatty, in an Adrenoleukodystrophy (ALD) Mouse Model

Purpose: Adrenoleukodystrophy (ALD) is an X‐linked disorder caused by a mutation in the Abcd1 gene and characterized by the accumulation of saturated very long-chain fatty acids (VLCFA), mainly hexacosanoic acid (C26:0), particularly in plasma, cerebral white matter, adrenal cortex, and testis1. The elevation of VLCFAs primarily results from impaired β-oxidation of VLCFAs in peroxisomes and decreased activity of peroxisomal very-long-chain acyl CoA synthetase (VLCS), which ultimately leads to severe and progressive neurological dysfunction2. Monounsaturated fatty acids can reduce saturated VLCFA accumulation in fibroblasts derived from patients, thus indicating the potential use of dietary fatty acids to lower the toxic C26:0 levels in patients with ALD and delay disease onset or progression3,4. We previously showed the biochemical benefits of nervonic acid (NA, C24:1), a naturally existing monounsaturated fatty acid, in lowering C26:0 levels in ALD fibroblasts3. While NA has been utilized in the market as a supplement in combination with other substances, the pharmacokinetics (PK) of NA in rodents or humans is not fully understood. The objective of this study is to evaluate the key PK parameters and assess brain exposure to NA in an ALD mouse model, which displays elevated tissue levels of saturated VLCFAs, particularly in the brain and adrenal gland.

Methods: Pharmacokinetic studies were performed on ALD gene-knockout mice (KO; Abcd1−). A single dose of 30 mg/kg stable-labeled NA was administered either intravenously (IV) or orally (PO) to 12-week-old male mice using a sparse sampling approach. Blood samples were collected from the submandibular vein prior to dosing and at 0.25, 0.5, 1, 2, 6, 18, 24, 30, 48, 72, and 168 hours post-administration. The accuSpin™ Micro 17 Microcentrifuge was utilized to separate plasma from blood immediately after sample collection, in preparation for future analysis. Brain and liver samples were collected at selected time points for the evaluation of NA distribution. A previously developed GC/MS method was used to analyze the concentration of NA in both plasma and tissue samples. PK parameters including systemic clearance (CL), volumes of distribution (V), elimination half-life (t1/2), and the area under the curve (AUC) were estimated using Phoenix™ (Certara, V8, NC, USA) with non-compartmental analysis (NCA). One-compartment population model was also evaluated for NA using non-linear mixed effects (NLME). The oral bioavailability of NA was determined based on AUCs.

Results: To distinguish it from the endogenous levels of NA, we used stable-labeled NA in this study to obtain accurate data for PK analysis. Following single-dose IV administration, the plasma concentration of NA was approximately 0.06 μg/mL. The concentration of NA decreased exponentially with time, which indicates first-order elimination kinetics. By applying NCA on the IV data, the estimated CL is 183.8 mL/hr, the estimated V is 10872 mL, the elimination t1/2 was estimated to be 41 hrs, and the AUC was found to be 2.219 hr*μg/mL. One-compartment population model of NA will be developed based on the results from NCA as more data comes out, and the results will be presented on the poster. Tissue samples and samples obtained from the oral study are being analyzed and the corresponding results will be elaborated on during the presentation.

Conclusion: In summary, we investigated the PK of NA in mice after a single IV or PO administration. This is the first PK study of NA in rodents. Our results indicated that NA was eliminated slowly with its estimated t1/2 of 41 hrs, which is comparable to those of Omega-3 carboxylic acids. Furthermore, we also evaluated the accumulation of NA in tissues (brain and liver), which is crucial for understanding the exposure-response relationship. As a key component involved in the biosynthesis of myelin, NA seems to be a promising candidate for treating not only ALD but also other neurological diseases. Further studies would be required to better understand the population PK of NA and develop dosage regimens for treating the mentioned diseases. Long-term safety and efficacy studies would also be required to evaluate the therapeutic potential of NA.

References: [1] Kemp S, Valianpour F, Denis S, et al. Elongation of very long-chain fatty acids is enhanced in X-linked adrenoleukodystrophy [published correction appears in Mol Genet Metab. 2008 Mar;93(3):350]. Mol Genet Metab. 2005;84(2):144-151. doi:10.1016/j.ymgme.2004.09.015
[2] Lu JF, Lawler AM, Watkins PA, et al. A mouse model for X-linked adrenoleukodystrophy. Proc Natl Acad Sci U S A. 1997;94(17):9366-9371. doi:10.1073/pnas.94.17.9366
[3] Terluk MR, Tieu J, Sahasrabudhe SA, et al. Nervonic Acid Attenuates Accumulation of Very Long-Chain Fatty Acids and is a Potential Therapy for Adrenoleukodystrophy [published online ahead of print, 2022 Apr 4]. Neurotherapeutics. 2022;10.1007/s13311-022-01226-7. doi:10.1007/s13311-022-01226-7
[4] Rizzo WB, Watkins PA, Phillips MW, Cranin D, Campbell B, Avigan J. Adrenoleukodystrophy: oleic acid lowers fibroblast saturated C22-26 fatty acids. Neurology. 1986;36(3):357-361. doi:10.1212/wnl.36.3.357

Figure 1. Schematic diagram of study design (Created with BioRender.com)