Discovery and Optimization of Pyrazole Amides as Inhibitors of ELOVL1

Abstract

Accumulation of very long chain fatty acids (VLCFAs) due to defects in ATP binding cassette protein D1 (ABCD1) is thought to underlie the pathologies observed in adrenoleukodystrophy (ALD). Pursuing a substrate reduction approach based on the inhibition of elongation of very long chain fatty acid 1 enzyme (ELOVL1), we explored a series of thiazole amides that evolved into compound 27a highly potent, central nervous system (CNS)-penetrant compound with favorable in vivo pharmacokinetics. Compound 27 selectively inhibits ELOVL1, reducing C26:0 VLCFA synthesis in ALD patient fibroblasts, lymphocytes, and microglia. In mouse models of ALD, compound 27 treatment reduced C26:0 VLCFA concentrations to near-wild-type levels in blood and up to 65% in the brain, a disease-relevant tissue. Preclinical safety findings in the skin, eye, and CNS precluded progression; the origin and relevance of these findings require further study. ELOVL1 inhibition is an effective approach for normalizing VLCFAs in models of ALD.

Discovery of Novel, Orally Bioavailable Pyrimidine Ether-Based Inhibitors of ELOVL1

“…Similar to pyrazole 1 , compound 22 demonstrated a significant reduction of C26:0 lysophosphatidyl choline (LPC) synthesis in human HEK293 cells. Human HEK293 cells were treated with 100 nM compound 22 and 13 C-labeled acetate, and the synthesis of C16:0 to C26:0 LPCs was measured over a 48 h period (Figure ).…”

“…These results suggest that compound 22 specifically inhibits ELOVL1 and has minimal activity against ELOVL6 and ELOVL7 in human cells (IC 50 values of 22 were >50 μM for ELOVLs 4, 6, and 7. IC 50 values were determined using a radiometric enzyme assay) …”

“…In an 8 week investigative safety study in rats, corneal opacities were observed macroscopically at all dose levels (10 and 50 mg/kg/day QD). The ocular findings were consistent with observations on our lead compound 1 , as well as an additional compound from a third structurally distinct series (manuscript in preparation), suggesting a pharmacological class effect. The ocular findings were specific to rats.…”

“…All in vitro and in vivo VLCFA assessments (including the analysis of dried blood spot and tissue samples) were carried out as previously described …”

“…26 Recently, we described our efforts to optimize a novel series of pyrazole amide-based inhibitors of ELOVL1 as a means of reducing VLCFA levels in the central nervous system (CNS), which we hypothesized could prevent conversion to the cerebral form of the disease as well as slow or arrest disease progression in adults. 27 Optimization of a high-throughput screening (HTS) hit along with scaffold hopping rapidly identified a potent and metabolically stable pyrazole amide analogue, 1, that reduced C26:0 VLCFA levels in the blood of ABCD1 knockout (KO) mice to near wild-type (WT) levels (Figure 1). 27…”